Method and system for joining workpieces

Abstract

To provide a method for joining first and second workpieces to each other.SOLUTION: First and second workpieces have respective first and second engagement surfaces thereof. First and second heated portions of the first and second workpieces that are adjacent to the first and second engagement surfaces are heated to one or more hot working temperatures, at which the heated portions are plastically deformable. One or both of the first and second engagement surfaces are formed to limit heat transfer from the first and second heated portions into respective body portions contiguous therewith. While the first and second heated portions are at the hot working temperature(s), the first and second heated portions are engaged with each other and urged together, and one or both of the workpieces are moved relative to the other, for at least partial plastic deformation of the first and second heated portions to join the first and second workpieces together.SELECTED DRAWING: Figure 1A

Description

Technical Field

[0001] The present invention is a method for joining an object to be processed.

Background Art

[0002] As is well known in the art, when conventional welding techniques are applied to relatively thick aluminum objects to be processed (for example, having a thickness of about 12.7 mm (1 / 2 inch)), good results are often not obtained. One of the problems is that in conventional aluminum welding methods, gas often occurs at the welded part, and bubbles are generated inside the temporarily melted aluminum. As a result, conventional aluminum welded parts often become porous to some extent and are prone to cracking. In addition, in conventional welding techniques, metal is generally melted, but when the melted metal solidifies, weak portions affected by heat are formed at the welded part.

[0003] In the prior art, in order to perform solid-state fusion bonding of an object to be processed made of another material (for example, steel), first, a part of the object to be processed is heated to a hot working temperature or a range of hot working temperatures (that is, a temperature lower than the melting temperature) to cause plastic deformation in a part of the object to be processed. Next, the heated parts of the two objects to be processed are engaged with each other. The engaged two heated parts are combined and urged, and while maintaining the heated parts at a hot working temperature at which plastic deformation is possible, one or both of the heated parts are moved relative to the other to metallurgically join the objects to be processed. For example, Patent Document 1 discloses a method of solid-state welding.

[0004] In a well-known solid-state fusion bonding process, engaging the engaging surfaces while relatively moving one or both of the engaging surfaces is performed when the engaging surfaces are in a state where plastic deformation is possible. For this reason, conventional processes are generally intended to be completed in a relatively short time after the heated part is heated to the hot working temperature. Even when the thermal conductivity (k) of the material is relatively low, it is necessary to perform engagement and relative movement within a limited time during which the heated part can be plastically deformed, which depends on the rate at which the heated part cools to a temperature lower than the hot working temperature range.

[0005] When only a part of the solid is heated, a temperature difference occurs within the solid, and a heat flow is generated due to that temperature difference. The rate of heat transfer (or dissipation) from the heated portion is influenced by various factors. Generally, relatively rapid heat loss from the heated portion occurs due to heat transfer by conduction from the heated portion of each object to be processed to other portions connected to that heated portion. The rate of energy transfer due to the temperature gradient can be affected by various parameters.

[0006] The thermal conductivity of the object to be processed is mainly determined by the material of the object to be processed (e.g., steel). When the object to be processed is made of steel, the thermal conductivity of the steel is relatively low (e.g., about 45 W·m -1 ·K -1 ) for carbon steel, for example), so there is sufficient time to complete solid fusion before the temperature of the heated portion drops below the hot working temperature and reaches a temperature at which plastic deformation is not possible.

[0007] However, if one or both of the objects to be processed contain a high thermal conductivity material (e.g., aluminum with a thermal conductivity of about 237 W at atmospheric pressure and about 20 degrees, or copper with a thermal conductivity of about 401 W), the heated portion rapidly loses heat, so the state in which plastic deformation is possible while engaging cannot be maintained for a sufficiently long time. For this reason, a well-known solid fusion method cannot be performed satisfactorily.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0009] For the above reasons, there is a need for a method of joining one or more objects to be processed with high thermal conductivity that eliminates or reduces one or more problems and drawbacks of the prior art.

Means for Solving the Problems

[0010] The present invention generally provides a method for joining a first and a second object to be processed. The objects to be processed each have a first and a second engagement surface. First and second heated portions of the first and second objects to be processed in the vicinity of the first and second engagement surfaces are heated to one or more hot working temperatures at which the heated portions are plastically deformable. The hot working temperature is below the melting point of the material. One or both of the first and second engagement surfaces are formed to limit heat transfer to the adjacent body portions. While the heated portions are at the hot working temperature, the first and second heated portions are engaged with each other and biased together to at least partially plastically deform the heated portions, and one or both of the objects to be processed are moved relative to the other, whereby the first and second objects to be processed are joined by metallurgical bonding. Since the material is not melted, no weak portion affected by heat is formed at the joint.

[0011] The objects to be processed may be made of a high thermal conductivity material. Alternatively, one or both of the objects to be processed may be made of a material with low thermal conductivity. The material of one or both of the objects to be processed is metal (such as aluminum, copper, steel, etc.) or non-metal (such as ceramic, etc.).

[0012] The present invention can be better understood by referring to the accompanying drawings.

Brief Description of the Drawings

[0013]

Figure 1A

Figure 1B

Figure 1C

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Figure 2C

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Figure 4A

Figure 4B

Figure 4C

Figure 5A

Figure 5B

Figure 5C

Figure 6A

Figure 6B

Figure 6C

Figure 6D

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Figure 8A

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Figure 9A

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Figure 9C

DETAILED DESCRIPTION OF THE INVENTION

[0014] Throughout the accompanying drawings, corresponding elements are denoted by the same reference numerals. First, with reference to FIGS. 1A to 4C, an embodiment of a method for joining objects to be processed according to the present invention will be described.

[0015] In one embodiment, the method of the present invention includes providing a first object to be processed 10 having a first engaging surface 12 including a plurality of first ridges 14 and first valleys 16 provided alternately. Also provided is a second object to be processed 18 having a second engaging surface 20 in which a plurality of second ridges 22 and second valleys 24 are provided alternately. The widths of the ridges and valleys shown are exaggerated for clarity of illustration.

[0016] As shown in FIG. 1A, the first and second objects to be processed 10, 18 are preferably arranged at a predetermined distance "D" apart so that a gap 26 is formed between the first and second engaging surfaces 12, 20 facing each other. In one embodiment, the first and second objects to be processed 10, 18 are made of a high thermal conductivity material such as aluminum. Here, the high thermal conductivity material refers to a material having a thermal conductivity equal to or higher than that of aluminum, for example, copper.

[0017] A person skilled in the art can understand that the method of the present invention can be used even for materials with low thermal conductivity. Alternatively, the method of the present invention may be used when bonding a material with low thermal conductivity (for example, steel, ceramic) to a material with high thermal conductivity. For example, the method of the present invention can be used when the thermal conductivity of the object to be processed is not high, but it is desirable to slightly slow down the heat conduction rate across the temperature gradient in the object to be processed. A person skilled in the art can also understand that a metal object to be processed can be heated by induction heating, while a ceramic object to be processed is preferably heated by radiant heating.

[0018] Preferably, one or more heating elements 27 are arranged in the gap 26 to heat the first and second heated parts 28, 30 of the objects to be processed 10, 18 to a hot working temperature at which the first and second heated parts are at least partially plastically deformable. As will be described later, preferably, the first and second heated parts 28, 30 are located in the vicinity of the first and second engaging surfaces 12, 20 at the first and second peak portions 14, 22.

[0019] A person skilled in the art can understand that the hot working temperature is lower than the melting temperature of the material of the object to be processed. Also, the hot working temperature at which the heated part is plastically deformable is a temperature over a given range. In this specification, it is understood that the hot working temperature includes any temperature within the given range of hot working temperatures.

[0020] Preferably, the heated parts 28, 30 are heated by induction heating. Preferably, the heated parts 28, 30 are first heated to the hot working temperature. When the first and second heated parts 28, 30 are heated to the hot working temperature, the first and second main body parts 32, 34 are respectively formed in the first and second objects to be processed 10, 18. The first and second main body parts 32, 34 are not initially heated to the hot working temperature. The first and second main body parts 32, 34 are connected to the first and second heated parts 28, 30, but are parts of the first and second objects to be processed 10, 18 that are not initially heated to the hot working temperature. Those skilled in the art can understand that when the first and second heated parts reach the hot working temperature, the temperature of the main body parts 32, 34 begins to rise by conduction.

[0021] The first and second heated parts 28, 30 preferably include the first and second ridge parts 14, 22. The first and second ridge parts 14, 22 are respectively formed so as to limit heat transfer by conduction to the first and second main body parts 32, 34. Initially (that is, when the first and second heated parts 28, 30 are first heated to the hot working temperature), the first and second heated parts 28, 30 are located on the proximal end side of the first and second ridge parts 14, 22.

[0022] For clarity of illustration, the dashed lines indicated by the reference numerals 36, 38 in FIGS. 1A and 1B respectively show the ideal boundary lines between (i) the first heated part 28 and the first main body part 32, and (ii) the second heated part 30 and the second main body part 34 when the heated parts 28, 30 are first heated to the hot working temperature. As described above, the temperatures of the first and second main body parts 32, 34 are initially lower than the hot working temperature. The dashed lines 36, 38 indicate the ranges of the heated parts 28, 30 at the time when the temperature of the heated parts first reaches the hot working temperature.

[0023] Therefore, the dashed lines 36, 38 indicate that the temperatures of the main body parts 32, 34 are initially lower than the hot working temperature. A person skilled in the art can understand that the illustrated boundary lines 36, 38 are approximate lines and are temporary. For example, although shown as straight lines, they may not actually be so in reality. A person skilled in the art can also understand that in fact, the position of the boundary line between the heated part and the adjacent main body part changes in a short time as heat is transferred (i.e., mainly by conduction) from the heated parts 28, 30 to the adjacent main body parts as soon as the heated parts 28, 30 reach the hot working temperature.

[0024] From the above, it can be seen that the straight dashed lines 36, 38 in FIG. 1A indicate the boundary lines (simplified for clarity) between the heated parts 28, 30 of the workpieces 10, 18 and the main body parts 32, 34 at the time when the heated parts first reach the hot working temperature.

[0025] In use, as shown in FIG. 1A, first, the first and second workpieces 10, 18 are arranged at a distance "D" apart, and the heating element 27 is arranged therebetween. Preferably, at least the first and second heated parts 28, 30 are covered by an inert (non-oxidizing) atmosphere during heating and engagement. Suitable gases for forming the inert atmosphere and suitable means for containing and holding the inert atmosphere in a predetermined position are well known to those skilled in the art. In one embodiment, the inert atmosphere may be arranged to at least partially cover the first and second workpieces 10, 18. The inert atmosphere and its container are omitted in the drawings for clarity.

[0026] Next, preferably by energizing the heating element 27, both the first heated part 28 of the first workpiece 10 and the second heated part 30 of the second workpiece 18 are heated to the hot working temperature.

[0027] When the heated parts 28, 30 reach the hot working temperature, the heating element 27 is removed from the gap 26. As shown in FIGS. 1A and 1B, when the heated parts 28, 30 reach the hot working temperature, a dislocation operation is preferably performed on one or both of the first and second objects to be processed 10, 18, as indicated by the arrows "A" in FIG. 1B. 1 ", "A" 2 ". By this dislocation operation, the engaging surfaces 12, 20 engage with each other. The dislocation operation may be performed on both objects to be processed, or either one, i.e., the first object to be processed 10 or the second object to be processed 18, or both may be dislocated.

[0028] While the first and second heated parts are at the hot working temperature, preferably, the first and second engaging surfaces are biased in the directions indicated by the arrows "A" 1 ", "A" 2 ". Also preferably, while the heated parts 28, 30 are at the hot working temperature, an engaging operation is performed on one or both of the first and second objects to be processed 10, 18, and they engage with each other and are biased together (FIG. 1B). The relative engaging operation of one or both of the first and second objects to be processed 10, 18 is schematically shown by the arrows "B" in FIG. 1B. 1 ", "B" 2 ". Such movement is possible while the heated part is plastically deformable, i.e., at the hot working temperature. Also, since the objects to be processed 10, 18 are fitted by clearance fit, the engaging operation can be performed. Movement in the z direction (i.e., the direction perpendicular to the plane of the drawing) is also possible.

[0029] The engaging operation may be any type of operation performed relatively by one or both of the engaged first and second objects to be processed 10, 18 with respect to the other, regardless of whether it is regularly repeated. While the first and second objects to be processed 10, 18 are engaged with each other, they are pressed against each other, i.e., at the time of engagement, the objects to be processed 10, 18 are in the directions of the arrows "A" in FIG. 1B. 1 ", "A" 2It is preferably biased in the opposite direction indicated by 」. After the engaging surfaces 12 and 20 are engaged with each other and the engaging operation is performed on the objects to be processed 10 and 18, as will be described later, the objects to be processed 10 and 18 are preferably continuously biased until they are joined to each other.

[0030] Basically, while the heated parts 28 and 30 are at the hot working temperature and the engaging surfaces 12 and 20 are biased against each other, it is preferable to perform the engaging operation on one or both of the objects to be processed 10 and 18. The engaging operation may be any operation that relatively moves one or both of the objects to be processed 10 and 18 relative to the other. The relative movement may be repeated regularly (for example, at a preselected time interval) or irregularly.

[0031] In one embodiment, preferably, as shown in FIG. 1A, the first ridge portion 14 is first aligned with the second groove portion 24, and the second ridge portion 22 is first aligned with the first groove portion 16. As shown in FIG. 1B, in one embodiment, preferably, the first ridge portion 14 is disposed in the second groove portion 24 and the second ridge portion 22 is disposed in the first groove portion 16 by a dislocation operation. As shown in FIGS. 1A and 1B, in one embodiment, the first ridge portion preferably fits into the second groove portion, and the second ridge portion preferably fits into the first groove portion. Preferably, the first ridge portion, the first groove portion, and the second groove portion are rounded.

[0032] Those skilled in the art can understand that in the embodiments shown in FIGS. 1A and 1B, when engaged, the first and second objects to be processed 10 and 18 preferably fit into each other with a clearance fit, that is, when the ridge portion is located in the corresponding groove portion, a predetermined relatively small clearance is generated between the engaging surfaces 12 and 20.

[0033] As shown in FIG. 1A, during heating, the peak portions 14, 22 are located on the proximal side of the heating element 27. Preferably, the peak portions 14, 22 are formed to isolate the heated portions 28, 30 from the main body portions 32, 34 to a limited extent, that is, to at least partially isolate the portions of the workpieces 10, 18 that are first heated to the hot working temperature from the main body portions 32, 34 of the workpieces that are not first heated to the hot working temperature. In this way, heat transfer by conduction from the heated portion to the remaining portion of the workpiece is restricted by the physical characteristics of the engagement surfaces 12, 20. The peak portions 14, 22 are formed so as to limit the range in which the volume of the heated portions 28, 30 is continuous with the volume of the corresponding main body portions 32, 34, whereby the degree of heat transfer by conduction from the heated portions 28, 30 to the main body portions 32, 34 is restricted.

[0034] Since the degree of heat transfer from the heated portion to the main body portion is restricted, as will be described later, the heated portions are maintained at the hot working temperature for a sufficiently long time after being first heated to the hot working temperature so that they can be joined to each other by the engagement operation.

[0035] As described above, in one embodiment, the workpieces 10, 18 are preferably formed of one or more metals having a relatively high thermal conductivity. Those skilled in the art are well aware of metals (including alloys) having a relatively high thermal conductivity such as aluminum. As soon as the heated portions 28, 30 are heated to the hot working temperature, heat energy is transferred to some extent by conduction from the heated portions to the portions in the vicinity of the main body portions 32, 34.

[0036] As shown in FIGS. 1A and 1B, in one embodiment, when the first and second engagement surfaces 12, 20 engage with each other, the portions "T" 1 ", "T" 2It is preferable that the ridges 14, 22 engage with the portion "」. However, the ridges 14, 22 are at the hot working temperature. As described above, when the workpieces 10, 18 engage with each other, a relative engaging operation is performed on one or both of the workpieces in a state where the workpieces 10, 18 are biased against each other. At the time of engagement, sufficient heat is transmitted by conduction from each of the ridges 14, 22 to each portion "T 1 ", "T 2 ", and it is considered that the materials of the workpieces are joined over the entire engaging surfaces 12, 20.

[0037] As described above, the material is plastically deformable over the range of the hot working temperature. Since the workpieces are made of a high thermal conductivity material, heat is transmitted relatively quickly from the ridges 14, 22 to the portions "T 1 ", "T 2 " that engage with the ridges.

[0038] The material in the heated portions 28, 30 at the hot working temperature is a very thin layer, and the thicknesses of the heated portions 28, 30 shown in FIGS. 1A and 1B are exaggerated for clarity of illustration. As described above, the engaging surfaces 12, 20 are maintained at the hot working temperature for a short time after engagement. That is, each layer has a plastically deformable temperature when engaged with each other. The engaged and heated materials tend to adhere to each other, and in a state where they are engaged at the hot working temperature, shear occurs in the heated material due to the engaging operation. Due to the shearing action, the fine structure of the metal in the heated material is torn, and a region "R" of recrystallized metal is formed over the original engaging surfaces 12, 20, and the engaging surfaces are included in the region "R" (FIG. 1C). In this way, the workpieces 10, 18 are metallurgically joined to each other. As the metal is sheared and cooled, recrystallization of the metal occurs, and as a result, a relatively uniform and fine microstructure is formed over the entire region "R" (FIG. 1C) where the workpieces 10, 18 are joined or bonded to each other, and the original engaging surfaces are at least partially included.

[0039] The metallurgical bonding region "R" is slightly smaller than the heated portions 28, 30 and may not be substantially linear as shown in FIG. 1C. The width of the region "R" shown in FIG. 1C is exaggerated for clarity of illustration.

[0040] One skilled in the art can understand that when the high thermal conductivity material is aluminum, it is necessary to deal with the aluminum oxide layer formed on aluminum in an ambient atmosphere because the aluminum oxide layer hinders metallurgical bonding. For example, the engaging surfaces 12, 20 of the first and second objects to be processed 10, 18 may be formed (e.g., by cutting and polishing) immediately before the engaging surfaces are surrounded by an inert atmosphere. Alternatively, even if the engaging surfaces are not cut or polished, the oxide layer may be sufficiently broken when a shearing force is applied to the engaging materials.

[0041] As described above, the objects to be processed 10, 18 are joined or bonded to form the product 39 (FIG. 1C). The first and second objects to be processed are joined over the region "R", and the microstructure within the region "R" is substantially uniform and relatively fine, resulting in a strong bond.

[0042] In FIG. 1C, the product 39 is shown as having planar or substantially planar side shapes "P" 1 ", "P" 2 ". However, the product 39 may be formed such that the shapes "P" 1 ", "P" 2 " are non-planar, e.g., convex or concave, in the region "R" where the objects to be processed 10, 18 are joined to form the product 39. As an example, a convex portion "Q" is shown by a dashed line in FIG. 1C.

[0043] In an alternative embodiment of the method of the present invention, after the engaging surfaces are first engaged, the dislocation operation may be interrupted for a short time. That is, after the engaging surfaces 12, 20 are first engaged with each other, for a predetermined short time, the objects to be processed are engaged with each other but may not be further biased together. The engaging operation is continued for this predetermined short time. During the predetermined short time, the portions "T" 1 ", "T" 2from the heated part connected to the "」, or from the part "T 1 」,「T 2 from the heated part engaged with the "」, heat is further transferred to the part "T 1 」,「T 2 」 by conduction. After a predetermined short time, the workpieces are biased against each other again, and by continuing the engaging operation, the workpieces are joined to each other. Alternatively, after a predetermined short time, the engaging operation is continued (or, in some cases, restarted), and then the workpieces are biased against each other.

[0044] Another alternative embodiment of the method of the present invention is shown in FIGS. 2A to 2C. As shown in FIGS. 2A and 2B, in this embodiment, preferably, the first and second workpieces 110, 118 are arranged such that the first ridge portion 114 of the first workpiece 110 is aligned with the second ridge portion 122 of the second workpiece 118. Also preferably, the first groove portion 116 is aligned with the second groove portion 124.

[0045] The first and second workpieces 110, 118 are preferably arranged at a second predetermined distance "2D" from each other. The first and second workpieces 110, 118 are formed of a high thermal conductivity material such as aluminum, for example. Preferably, the first and second workpieces 110, 118 are arranged such that the first and second engaging surfaces 112, 120 face each other and a gap 126 is provided therebetween.

[0046] Preferably, then one or more heating elements 127 are arranged in the gap 126 to heat the first and second heated parts 128, 130 near the first and second engaging surfaces 112, 120 to a hot working temperature at which the first and second heated parts 128, 130 are plastically deformable. Preferably, the heated parts 128, 130 are heated by induction heating.

[0047] Initially, only the heated parts 128, 130 are heated to the hot working temperature. When the first and second heated parts 128, 130 are heated to the hot working temperature, the first and second main body parts 132, 134 are respectively formed in the first and second objects to be processed 110, 118. The first and second main body parts 132, 134 are not initially heated to the hot working temperature. The first and second main body parts 132, 134 are connected to the first and second heated parts 128, 130, but are parts of the first and second objects to be processed 110, 118 that are not initially heated to the hot working temperature.

[0048] The first and second heated parts 128, 130 are preferably located on the proximal ends of the first and second peak parts 114, 122. The first and second peak parts 114, 122 are formed so as to limit heat transfer by conduction to the first and second main body parts 132, 134 respectively.

[0049] As shown in FIGS. 2A and 2B, the dashed lines indicated by reference numerals 136, 138 respectively indicate (i) the ideal boundary lines between the first heated part 128 and the first main body part 132, and (ii) between the second heated part 130 and the second main body part 134. As described above, the temperatures of the first and second main body parts 132, 134 are initially lower than the hot working temperature.

[0050] In use, the first and second objects to be processed 110, 118 are first arranged at a distance of "2D" apart, and the heating element 127 is arranged therebetween. Preferably, the first and second engaging surfaces 112, 120 and the first and second heated parts 128, 130 are covered by an inert atmosphere during heating and engagement. Suitable gases for forming an inert atmosphere and suitable means for containing the inert atmosphere are well known to those skilled in the art.

[0051] Next, preferably by energizing the heating element 127, the first heated part 128 of the first object to be processed 110 and the second heated part 130 of the second object to be processed 118 are heated to the hot working temperature.

[0052] While the first and second heated portions 128, 130 are at the hot working temperature, the first and second engaging surfaces 112, 120 engage with each other, and the first and second objects to be processed 110, 118 are joined to each other. As shown in FIGS. 2A and 2B, when the heated portions 128, 130 reach the hot working temperature, a dislocation operation is preferably performed on one or both of the first and second objects to be processed 110, 118 as indicated by the arrows "2A 1 ", "2A 2 " in FIG. 2B. By this dislocation operation, the heated portions 128, 130 engage with each other. The dislocation operation may be performed on both objects to be processed, or may be performed on either one, that is, the first object to be processed 110 or the second object to be processed 118, or both.

[0053] As shown in FIG. 2B, in one embodiment, preferably, the first ridge portion 114 engages with the second valley portion 122 by the dislocation operation. When the first ridge portion 114 engages with the second ridge portion 122, the first valley portion 116 is disposed on the opposite side of the second valley portion 124.

[0054] Those skilled in the art can understand that in the embodiments shown in FIGS. 2A and 2B, when engaging, the heated portions 128, 130 of the first and second ridge portions 114, 122 are plastically deformed. Due at least in part to the engaging operation performed on one or both of the objects to be processed 110, 118 in a state where the heated portions are at the hot working temperature and the heated portions 128, 130 are pressed together, the adjacent valley portions are substantially filled by the deformed ridge portions. In FIG. 2C, the product formed by the joining of the objects to be processed 110, 118 is indicated by reference numeral 139.

[0055] The engaging operation may be any kind of operation performed relatively by one or both of the engaged first and second objects to be processed 110, 118 with respect to the other. The relative engaging operation of one or both of the first and second objects to be processed 110, 118 is the arrow "2B 1 ", "2B 2is schematically shown by "", and such an engagement operation may include an operation in the z direction, that is, an operation orthogonal to the plane of the drawing. While the first and second workpieces 110, 118 are engaged, the workpieces 110, 118 are urged against each other in opposite directions indicated by the arrows "2A 1 ", "2A 2 " in FIG. 2B. After the engaging surfaces 112, 120 are engaged with each other, the workpieces 110, 118 are continuously urged against each other until they are joined.

[0056] The ridges and valleys can have any suitable configuration. Preferably, the ridges and valleys of the first and second workpieces 110, 118 are formed so as to limit heat transfer by conduction from the ridges to the remaining portions of the workpieces. By limiting the rate of heat energy transfer by conduction from the heated regions 128, 130 to the main body portions 132, 134, it becomes possible to maintain the heated portions 128, 130 at the hot working temperature for a longer time.

[0057] However, since the portions "2T 1 ", "2T 2 " forming the valleys 116, 124 of the main body portions 132, 134 are also heated to the hot working temperature and made plastically deformable, those skilled in the art can understand that it is preferable that some heat energy is also transferred to these portions "2T 1 ", "2T 2 ". Preferably, the ridges 114, 122 and the valleys 116, 124 are formed so as to facilitate sufficient heat energy to be transferred by conduction from the heated portions 128, 130 to the portions "2T 1 ", "2T 2 ", and the portions "2T 1 ", "2T 2 " can be heated to the hot working temperature in a relatively short time.

[0058] In practice, when the high thermal conductivity material is aluminum, since the aluminum oxide layer may prevent bonding, it is necessary to deal with the aluminum oxide layer formed on aluminum in an ambient atmosphere. For example, the engaging surfaces 112, 120 of the first and second objects to be processed 110, 118 may be formed (e.g., by cutting and polishing) immediately before the engaging surfaces are surrounded by an inert atmosphere. Alternatively, even if the engaging surfaces are not cut or polished, the oxide layer may be sufficiently broken when a shearing force is applied to the engaging materials.

[0059] The heated portions 128, 130 plastically deform when engaged with each other. When the heated portions 128, 130 are sufficiently plastically deformed, the portions forming the valleys 116, 124 "2T 1 ", "2T 2 " engage with each other. Thereafter, an engaging operation is performed on the objects to be processed 110, 118. As described above, shearing occurs in the microstructure of the engaged and hot-worked temperature materials. As described above, recrystallization of the metal occurs as the metal is sheared and cooled. As a result, a relatively uniform and fine microstructure is formed over the entire region "2R" (FIG. 2C) where the objects to be processed 110, 118 are joined to each other.

[0060] The objects to be processed 110, 118 are combined or joined to form a product 139 (FIG. 2C). The first and second objects to be processed are joined over the region "2R". The microstructure of the region "2R" is substantially uniform and relatively fine, resulting in a strong bond. The engaging surface is at least partially included in the region "2R".

[0061] Also, the width of the region "2R" shown in FIG. 2C is exaggerated for clarity of illustration. In FIG. 2C, the product 139 is shown as having planar or substantially planar side shapes "2P 1 ", "2P 2 ". However, the product 139 has shapes "2P 1 ", "2P 2It may be formed such that "」" is non-planar, for example, convex or concave. As an example, the convex portion "2Q" is shown by a dashed line in FIG. 2C.

[0062] In an alternative embodiment of the method of the present invention, after the engagement surfaces are first engaged, the dislocation operation may be interrupted for a short time. That is, after the engagement surfaces 112, 120 are first engaged with each other, for a predetermined short time, the workpieces are engaged with each other but are not further biased together. The engagement operation is continued for this predetermined short time. During the predetermined short time, more heat is conducted to the portions "2T 1 ", "2T 2 ", that is, it is considered to be further transmitted from the heated portions respectively connected to the portions "2T 1 ", "2T 2 ". After the predetermined short time, the workpieces are biased against each other again, and the engagement operation is continued. As a result, the workpieces are joined to each other. Alternatively, after the predetermined short time, the engagement operation is continued (or, in some cases, restarted), and then the workpieces are biased against each other.

[0063] In another embodiment of the method of the present invention shown in FIGS. 3A and 3B, the workpieces 210, 218 have pointed peaks 214, 222 and fit into complementary valleys 216, 224. The method of heating and engaging the workpieces 210, 218 is substantially the same as the embodiment of the method shown in FIGS. 1A to 1C.

[0064] Preferably, one or more heating elements 227 are arranged in the gap 226 between the first and second engagement surfaces 212, 220 to heat the heated portions 228, 230 to the hot working temperature. The first and second workpieces 210, 218 are formed of a high thermal conductivity material such as aluminum, for example. However, it is preferable that the first and second main body portions 232, 234 of the first and second workpieces 210, 218 are not initially heated to the hot working temperature.

[0065] Preferably, before heating, the first and second engagement surfaces 212, 220 and the first and second heated portions 228, 230 are covered or surrounded by an inert atmosphere. The inert atmosphere is preferably maintained in a predetermined position during heating and engagement. Suitable gases for forming the inert atmosphere and suitable means for containing the inert atmosphere are well known to those skilled in the art.

[0066] Preferably, while the heated portions 228, 230 are at the hot working temperature with respect to the objects to be processed 210, 218, the first and second engagement surfaces 212, 220 of the objects to be processed 210, 218 are engaged with each other by performing a dislocation operation as shown by the arrows "3A" 1 ", "3A" 2 "(FIG. 3B). After the engagement, the objects to be processed are urged against each other until they are joined (in the directions indicated by the arrows "3A" 1 ", "3A" 2 "). While the heated portions 228, 230 are at the hot working temperature, an engagement operation is performed on one or both of the objects to be processed 210, 218, and at least one of the objects to be processed moves relative to the other as shown by the arrows "3B" 1 ", "3B" 2 ". As shown in FIG. 3B, since the ridges and valleys are engaged with each other, the range in which the engagement operation from one object to be processed to the other in the directions indicated by the arrows "3B" 1 ", "3B" 2 " is possible is limited to the gap between the objects to be processed. The engagement operation may also occur in the z direction, that is, the direction perpendicular to the plane of the drawing. In FIG. 3B, the gap "C" is exaggerated for clarity of illustration.

[0067] As shown in FIGS. 3A and 3B, the dashed lines indicated by the reference numerals 236, 238 respectively indicate the ideal boundary lines between (i) the first heated portion 228 and the first main body portion 232, and (ii) the second heated portion 230 and the second main body portion 234. As described above, the temperatures of the first and second main body portions 232, 234 are initially lower than the hot working temperature.

[0068] In practice, when the high thermal conductivity material is aluminum, it is necessary to deal with the aluminum oxide layer formed on the aluminum in an ambient atmosphere because the aluminum oxide layer may prevent bonding. For example, the engaging surfaces 212 and 220 of the first and second objects to be processed 210 and 218 may be formed (e.g., by cutting and polishing) immediately before the engaging surfaces are surrounded by an inert atmosphere. Alternatively, even if the engaging surfaces are not cut or polished, the oxide layer may be sufficiently broken when a shearing force is applied to the engaging materials.

[0069] As shown in FIG. 3A, during heating, the peaks 214 and 222 are located on the proximal side of the heating element 227. Preferably, the peaks 214 and 222 are formed to isolate the heated portions 228 and 230 from the main body portions 232 and 234 to a limited extent, that is, to at least partially isolate the portions of the objects to be processed 210 and 218 that are first heated to the hot working temperature from the main body portions 232 and 234 of the objects to be processed that are not first heated to the hot working temperature. In this way, heat transfer by conduction from the heated portion to the remaining portion of the object to be processed is restricted. The peaks 214 and 222 are formed to limit the range in which the volume of the heated portions 228 and 230 is continuous with the volume of the corresponding main body portions 232 and 234, thereby restricting the degree of heat transfer by conduction from the heated portions 228 and 230 to the main body portions 232 and 234.

[0070] Since the degree of heat transfer from the heated portion to the main body portion is restricted, as will be described later, the heated portions are maintained at the hot working temperature for a sufficiently long time after being first heated to the hot working temperature so that they can be joined to each other by an engaging operation.

[0071] As shown in FIGS. 3A and 3B, when the first and second engaging surfaces 212 and 220 engage with each other, the peaks 214 and 222 form the valleys 216 and 224 of the main body portions 232 and 234, respectively, the portion "3T 1 ", "3T 2engages with "」. However, the ridges 214, 222 are at the hot working temperature. As described above, when the workpieces 210, 218 engage with each other, a relative engagement operation is performed on one or both of the workpieces while the workpieces 210, 218 are biased against each other. At the time of engagement, sufficient heat is transferred by conduction from each of the ridges 214, 222 to each part "3T 1 ", "3T 2 ", and it is considered that the material of the workpiece joins over the entire engagement surfaces 212, 220.

[0072] As described above, the material is plastically deformable over the range of the hot working temperature. Since the workpiece is made of a high thermal conductivity material, heat is transferred relatively quickly from the ridges 214, 222 to the parts "3T 1 ", "3T 2 " that engage with the ridges.

[0073] In an alternative embodiment of the method of the present invention, after the engagement surfaces are first engaged, the dislocation operation may be interrupted for a short time. That is, after the engagement surfaces 212, 220 first engage with each other, for a predetermined short time, the workpieces are engaged with each other but are not further biased together. The engagement operation is continued over this predetermined short time. During the predetermined short time, it is considered that further heat is transferred by conduction from the heated part connected to the parts "3T 1 ", "3T 2 " or from the heated part engaging with the parts "3T 1 ", "3T 2 " to the parts "3T 1 ", "3T 2 ". After the predetermined short time, the workpieces are biased against each other again and the engagement operation is continued. As a result, the workpieces join together. Alternatively, after the predetermined short time, the engagement operation is continued (or, in some cases, resumed), and then the workpieces are biased against each other.

[0074] Similarly, the workpieces 310, 318 shown in FIGS. 4A to 4C are heated and engaged in substantially the same manner as the workpieces 110, 118 shown in FIGS. 2A to 2C. As shown in FIGS. 4A and 4B, in this embodiment, preferably, the first and second workpieces 310 and 318 are arranged such that the first crest 314 of the first workpiece 310 is aligned with the second crest 322 of the second workpiece 318. Therefore, preferably, the first trough 316 is also aligned with the second trough 324.

[0075] The first and second workpieces 310 and 318 are preferably arranged at a predetermined distance “4D” from each other. The first and second workpieces 310 and 318 are formed of a high thermal conductivity material such as aluminum, for example. Preferably, the first and second workpieces 310 and 318 are arranged such that the first and second engagement surfaces 312 and 320 face each other and a gap 326 is provided therebetween.

[0076] Preferably, then, one or more heating elements 327 are arranged in the gap 326 to heat the first and second heated portions 328 and 330 in the vicinity of the first and second engagement surfaces 312 and 320 to a hot working temperature at which the first and second heated portions 328 and 330 can be plastically deformed. Preferably, the heated portions 328 and 330 are heated by induction heating.

[0077] First, only the heated portions 328 and 330 are heated to the hot working temperature. When the first and second heated portions 328 and 330 are heated to the hot working temperature, first and second main body portions 332 and 334 are respectively formed in the first and second workpieces 310 and 318. The first and second main body portions 332 and 334 are not initially heated to the hot working temperature. The first and second main body portions 332 and 334 are portions of the first and second workpieces 310 and 318 that are adjacent to the first and second heated portions 328 and 330 but are not initially heated to the hot working temperature.

[0078] The first and second heated portions 328 and 330 are preferably located on the proximal ends of the first and second crests 314 and 322. The first and second crests 314 and 322 are formed to limit heat transfer to the first and second main body portions 332 and 334, respectively.

[0079] As shown in FIGS. 4A and 4B, the dashed lines indicated by reference numerals 336 and 338 respectively indicate the ideal boundary lines between (i) the first heated portion 328 and the first main body portion 332, and (ii) the second heated portion 330 and the second main body portion 334. As described above, the temperatures of the first and second main body portions 332 and 334 are initially lower than the hot working temperature.

[0080] In use, the first and second objects to be processed 310 and 318 are first arranged at a distance of "4D" apart, with the heating element 327 disposed therebetween. Preferably, the first and second engaging surfaces 312 and 320 and the first and second heated portions 328 and 330 are covered or surrounded by an inert atmosphere during heating and engagement. Suitable gases for forming an inert atmosphere and suitable means for containing the inert atmosphere are well known to those skilled in the art.

[0081] Next, preferably by energizing the heating element 327, both the first heated portion 328 of the first object to be processed 310 and the second heated portion 330 of the second object to be processed 318 are heated to the hot working temperature.

[0082] When the first and second heated portions 328 and 330 are at the hot working temperature, the first and second engaging surfaces 312 and 320 engage with each other, and the first and second objects to be processed 310 and 318 are joined to each other. As shown in FIGS. 4A and 4B, when the heated portions 328 and 330 reach the hot working temperature, a dislocation operation is preferably performed on one or both of the first and second objects to be processed 310 and 318 as indicated by the arrows "4A 1 ", "4A 2 " in FIG. 2B. By this dislocation operation, the heated portions 328 and 330 engage with each other. The dislocation operation may be performed on both objects to be processed, or on either one, i.e., the first object to be processed 310 or the second object to be processed 318, or on both.

[0083] A person skilled in the art can understand that in the embodiments shown in FIGS. 4A and 4B, when engaged, the heated portions 328 and 330 of the first and second ridges 314 and 322 are plastically deformed. While the heated portions are at the hot working temperature and the heated portions 328 and 330 are being pressed together, due to the engaging operation performed on one or both of the workpieces 310 and 318, the valleys in the vicinity are substantially filled by the deformed ridges. In FIG. 4C, the workpiece formed by joining the workpieces 310 and 318 is indicated by reference numeral 339.

[0084] The engaging operation may be any kind of operation that one or both of the engaged first and second workpieces 310 and 318 perform relative to the other. The relative engaging operation of one or both of the first and second workpieces 310 and 318 is schematically shown by the arrows "4B 1 ", "4B 2 " in FIG. 4B, and such an engaging operation may include an operation in the z direction, that is, an operation orthogonal to the plane of the drawing. While the first and second workpieces 310 and 318 are engaged, the workpieces 310 and 318 are urged against each other in opposite directions shown by the arrows "4A 1 ", "4A 2 " in FIG. 4B. In one embodiment, after the engaging surfaces 312 and 320 are engaged with each other, it is preferable that the workpieces 310 and 318 are continuously urged against each other until they are joined.

[0085] The ridges and valleys can have any suitable configuration. Preferably, the ridges and valleys of the first and second workpieces 310 and 318 are formed so as to limit heat transfer by conduction from the ridges to the remaining portions of the respective workpieces. By limiting the rate of heat energy transfer by conduction from the heated regions 328 and 330 to the main body portions 332 and 334, it becomes possible to maintain the heated portions 328 and 330 at the hot working temperature for a longer time.

[0086] However, the portions "4T 1 ", "4T 2」 is also heated to the hot working temperature and is made plastically deformable, so this part "4T" 1 ", "4T" 2 It will be understood by those skilled in the art that it is preferable that heat energy is also transmitted to some extent to ", "4T" 1 ", "4T" 2 ". Preferably, the ridges 314, 322 and the valleys 316, 324 promote sufficient heat energy to be transmitted by conduction from the heated portions 328, 330 to the parts "4T" 1 ", "4T" 2 ", "4T"

[0087] In practice, when the high thermal conductivity material is aluminum, since the aluminum oxide layer may prevent bonding, it is necessary to deal with the aluminum oxide layer formed on aluminum in the ambient atmosphere. For example, the engaging surfaces 312, 320 of the first and second objects to be processed 310, 318 may be formed (for example, by cutting and polishing) immediately before the engaging surfaces are surrounded by an inert atmosphere. Alternatively, even if the engaging surfaces are not cut or polished, the oxide layer may be sufficiently broken when a shearing force is applied to the engaging materials.

[0088] The heated portions 328, 330 plastically deform when they engage with each other. When the heated portions 328, 330 are sufficiently plastically deformed, the parts "4T" 1 ", "4T" 2 " that form the valleys 316, 324 engage with each other. Thereafter, an engaging operation is performed on the objects to be processed 310, 318. As described above, shearing occurs in the fine structure of the materials that are engaged and at the hot working temperature. As described above, as the metal is sheared and cooled, recrystallization of the metal occurs, and as a result, a relatively uniform and fine microstructure is formed over the entire region "4R" (FIG. 4C) where the objects to be processed 310, 318 are joined to each other.

[0089] The objects to be processed 310, 318 are joined or bonded to form the product 339 (FIG. 4C). The first and second objects to be processed are joined or bonded across the region "4R". The microstructure of the region "4R" is substantially uniform and relatively fine, resulting in a strong bond. The engagement surface is at least partially included in the region "4R".

[0090] Also, the width of the region "4R" shown in FIG. 4C is exaggerated for clarity of illustration. In FIG. 4C, the product 339 is shown as having a planar or substantially planar side surface shape "4P 1 ", "4P 2 ". However, the product 339 may be formed such that the shapes "4P 1 ", "4P 2 " are non-planar, for example convex or concave, in the region "4R" where the objects to be processed 310, 318 are joined to each other. As an example, the convex portion "4Q" is shown by a dashed line in FIG. 4C.

[0091] In another embodiment of the method of the present invention, after the engagement surfaces are first engaged, the dislocation operation may be interrupted for a short time. That is, after the engagement surfaces 312, 320 are first engaged with each other, for a predetermined short time, the objects to be processed are engaged with each other but are not further biased together. The engagement operation is continued over this predetermined short time. During the predetermined short time, heat is further transferred by conduction to the portions "4T 1 ", "4T 2 ", that is, it is considered to be further transferred from the heated portions respectively connected to the portions "4T 1 ", "4T 2 ". After the predetermined short time, the objects to be processed are biased against each other again, and the engagement operation is continued. As a result, the objects to be processed are joined to each other. Alternatively, after the predetermined short time, the engagement operation is continued (or, in some cases, resumed), and then the objects to be processed are biased against each other.

[0092] In another embodiment of the method of the present invention shown in FIGS. 5A to 5C, the first and second objects to be processed 410, 418 have fins 415, 423 extending from the exposed surfaces 413, 421 of the first and second main body portions 432, 434, respectively. The fins 415, 423 terminate at their respective ends 417, 425. Preferably, the first and second objects to be processed 410, 418 are arranged at a distance of "5D" apart, and a gap 426 is formed between the first and second objects to be processed 410, 418. In one embodiment, the first and second objects to be processed 410, 418 are made of a high thermal conductivity material such as aluminum.

[0093] Preferably, one or more heating elements 427 are arranged in the gap 426 to heat the heated portions 428, 430 of the objects to be processed 410, 418 to a hot working temperature at which the heated portions 428, 430 are plastically deformable. The heating element 427 preferably heats the heated portions 428, 430 by induction heating.

[0094] The fins 415, 423 are relatively thin, for example, having a thickness of about 0.1 mm or less. In one embodiment, the heated portions 428, 430 extend from the ends 417, 425 of the respective fins 415, 423 toward the exposed surfaces 413, 421 of the main body portions 432, 434. Preferably, the first and second heated portions are at least partially located on the tip side of the exposed surface. However, the heated portions 428, 430 may include a part of the main body portions 432, 434.

[0095] The fins 415, 423 are formed relatively thin in order to limit the degree to which heat is conducted from the heated portions 428, 430 to the main body portions 432, 434 through the fins 415, 423. The first and second main body portions 432, 434 of the first and second objects to be processed 410, 418 are preferably not heated to the hot working temperature.

[0096] Preferably, at least the first and second heated portions are covered or surrounded by an inert atmosphere during heating and engagement. Suitable gases for forming an inert atmosphere and suitable means for containing the inert atmosphere are well known to those skilled in the art.

[0097] For the objects to be processed 410, 418, preferably, while the heated parts 428, 430 are at the hot working temperature, as indicated by the arrows "5A 1 ", "5A 2 " in FIGS. 5B and 5C, a dislocation operation is performed, and the fins 415 of the first object to be processed 410 and the fins 423 of the second object to be processed 418 engage with each other.

[0098] After the first engagement, the objects to be processed 410, 418 are continuously biased with respect to each other until they are joined (i.e., in the directions indicated by the arrows "5A 1 ", "5A 2 "). While the heated parts 428, 430 are at the hot working temperature, an engagement operation is performed on one or both of the objects to be processed 410, 418, and at least one of the objects to be processed moves with respect to the other, as indicated by the arrows "5B 1 ", "5B 2 " in FIGS. 5B and 5C.

[0099] As shown in FIG. 5B, at the first engagement, the fins 415, 423 are bent, and the heated parts 428, 430 often engage with the exposed surfaces on the opposite sides of the main body parts 432, 434. For example, as shown in FIG. 5B, the heated part 428 of the fin 415 of the first object to be processed 410 engages with the exposed surface 421 of the main body part 434 of the second object to be processed 418. Similarly, the heated part 430 of the fin 423 of the second object to be processed 418 engages with the exposed surface 413 of the first main body part 432 of the first object to be processed 410. As described above, the temperatures of the first and second main body parts 432, 434 are preferably lower than the hot working temperature.

[0100] After the first engagement of the first and second workpieces 410, 418, as shown in FIG. 5C, the dislocation operation and the engagement operation are continued until the first and second workpieces 410, 418 are joined to each other. The heated portions 428, 430 are plastically deformable when at the hot working temperature. Thus, as shown in FIG. 5C, the engagement operation of the first workpiece 410 and / or the second workpiece 418 with respect to each other is continued, and the workpieces 410, 418 are continuously biased together, whereby the fins 413, 421 are pressed together in the region between the exposed surfaces 413, 421 of the first and second workpieces 410, 418. The fins pressed between the exposed surfaces 413, 421 and at least partially plastically deformed, and in some cases a part of the main body portions 432, 434, form a region to which the symbol "5R" is attached in FIG. 5C for clarity of illustration.

[0101] Since the engagement operation continues and the first and second workpieces are biased together, the material in the region "5R" is sheared, and a relatively uniform fine structure is formed in the material of the region "5R" throughout the region "5R", whereby the first and second workpieces 410, 418 are metallurgically bonded or joined to each other. The region "5R" includes the exposed surfaces and the fins.

[0102] In practice, when the high thermal conductivity material is aluminum, since the aluminum oxide layer may prevent bonding, it is necessary to deal with the aluminum oxide layer formed on aluminum under the ambient atmosphere. For example, the fins 415, 423 and the exposed surfaces 413, 421 of the first and second workpieces 410, 418 may be formed immediately before being surrounded or covered by an inert atmosphere (e.g., by cutting and polishing). Alternatively, even if the engagement surface is not cut or polished, the oxide layer may be sufficiently broken when a shearing force is applied to the engaging material.

[0103] As shown in FIGS. 6A and 6B, a method according to one embodiment includes providing a first object to be processed 610 having a first engagement surface 612. A second object to be processed 618 having a second engagement surface 620 is also provided. In one embodiment, the object to be processed includes a high thermal conductivity material (e.g., metal).

[0104] Preferably, the first and second objects to be processed 610, 618 are arranged at a predetermined distance "6D" from each other, and the first and second engagement surfaces 612, 620 face each other and are arranged such that a gap 626 is provided therebetween (FIG. 6A).

[0105] At least one heating element 627 is disposed in the gap 626 to heat the first and second heated portions 628, 630 near the first and second engagement surfaces 612, 620 to the first and second hot working temperatures at which the first and second heated portions 628, 630 plastically deform at the first and second peaks 614, 622, respectively.

[0106] Preferably, next, at least the first and second heated portions 628, 630 are covered with an inert atmosphere. Those skilled in the art can understand that the inert atmosphere is preferably contained in a suitable container (not shown).

[0107] Preferably, one or more heat insulating elements are disposed between the heating element 627 and the first engagement surface 612 to moderate the degree to which the first heated portion 628 is heated, that is, to limit the heat transfer rate from the heated portion 628 to the main body portion 632.

[0108] In the embodiment shown in FIG. 6A, two heat insulating elements 642, 644 are shown. As shown in FIG. 6A, the first heat insulating element 642 is disposed between the heating element 627 and the first engagement surface 612. The second heat insulating element 644 is disposed between the heating element 627 and the second engagement surface 620. The second heat insulating element 644 is configured to moderate the degree to which the second heated portion 630 is heated.

[0109] In one embodiment, preferably, the first and second heat insulation elements 642, 644 each have first and second openings or slots 646, 648. Preferably, the heat insulation elements are arranged such that the openings 646, 648 are aligned with the first and second ridge portions 614, 622, that is, located on the opposite side of the ridge portions. As a result, the first and second ridge portions 614, 622 are heated by the heating element 627 (e.g., by induction), while the main body portions 649, 651 of the first and second heat insulation elements 642, 644 are respectively disposed between the heating element 627 and the valley portions 616, 624, so the valley portions 616, 624 are not heated as much.

[0110] The heating element 627 preferably heats the heated portions 628, 630 by induction. Therefore, it is preferable that the heat insulation elements 642, 644 are configured to moderate the degree to which the first and second heated portions 628, 630 are heated by induction heating via the heating element 627.

[0111] In FIG. 6A, for clarity of illustration, only one heating element 627 is shown. As shown in FIG. 6A, when the heating element 627 is disposed in the gap 626, it is preferable that first and second slots are formed by the heating element 627 between (i) the heating element 627 and the first engagement surface 612 and (ii) the heating element 627 and the second engagement surface 620, and the first and second heat insulation elements 642, 644 are disposed therein.

[0112] Depending on the situation, only one of the heat insulation elements 642, 644 may be used. The heated portions 628, 630 of the first and second workpieces 619, 618 may be heated to different hot working temperatures by the heat insulation elements 642, 644. However, those skilled in the art can understand that, alternatively, the first and second heated portions 628, 630 may be heated to the same or substantially the same hot working temperature.

[0113] Preferably, by energizing the heating element 627, the first heated portion 628 of the first workpiece 610 and the second heated portion 630 of the second workpiece 618 are heated to the first and second hot working temperatures, respectively.

[0114] The first and second heated portions 628, 630 are preferably located on the proximal ends of the first and second peak portions 614, 622. The first and second peak portions 614, 622 are formed so as to limit heat transfer to the first and second main body portions 632, 634, respectively.

[0115] For clarity of illustration, in FIGS. 6A and 6C, the dashed lines labeled 636, 638 respectively indicate (i) the ideal boundary between the first heated portion 628 and the first main body portion 632, and (ii) the ideal boundary between the second heated portion 630 and the second main body portion 634. As described above, the temperatures of the first and second main body portions 632, 634 are lower than the hot working temperature.

[0116] Therefore, the dashed lines 636, 638 indicate the locations of the workpieces 610, 618 where the temperature is lower than the hot working temperature. Those skilled in the art will understand that the illustrated boundary lines 636, 638 are approximate lines because they are represented as straight lines, but in reality they may not be such lines. Those skilled in the art will also understand that in reality, the position of the boundary line between the heated portion and the adjacent main body portion may change in a short time as heat is transferred from the heated portion to the main body portion. From the above, it can be seen that the straight dashed lines 636, 638 represent the boundary lines between the portions 628, 630 of the workpieces 610, 618 at the hot working temperature and the portions 632, 634 at a temperature lower than the hot working temperature, and are simplified for illustration purposes.

[0117] In a state where the first and second heated portions 628 and 630 are plastically deformable, the first and second engaging surfaces 612 and 620 engage with each other, one or more of the engaging surfaces are moved relative to the other engaging surfaces, and the first and second objects to be processed 610 and 618 are joined to each other. The heating element 627 and the heat insulating elements 642 and 644 are preferably removed before the first and second engaging surfaces 612 and 620 are engaged with each other.

[0118] As shown in FIG. 6B, in one embodiment, with respect to the first and second objects to be processed 610 and 618, while the heated portions are at the hot working temperature, a dislocation operation is preferably performed in the directions indicated by the arrows "6A 1 ", "6A 2 ". As a result, the first and second engaging surfaces 612 and 620 engage with each other. Preferably, as shown in FIGS. 6A and 6B, the first ridge portion 614 is aligned with the second valley portion 624 before engagement. Similarly, before engagement, the second ridge portion 622 is preferably aligned with the first valley portion 616.

[0119] As shown in FIG. 6B, in one embodiment, preferably, by the dislocation operation, the first ridge portion 614 is disposed in the second valley portion 624, and the second ridge portion 622 is disposed in the first valley portion 616. Those skilled in the art will understand that in the embodiments shown in FIGS. 6A and 6B, when the first and second engaging surfaces 612 and 620 engage, the first and second objects to be processed 610 and 618 preferably fit together in a clearance fit, that is, when the ridge portions are located in the corresponding valley portions, a predetermined gap is formed between the first and second engaging surfaces 612 and 620.

[0120] Also, preferably, while the heated portions 628 and 630 are at the hot working temperature, an engaging operation is performed on at least one of the first and second objects to be processed 610 and 618, or on both the first and second objects to be processed 610 and 618, and they are engaged with each other and biased together (FIG. 6B). Such an operation is possible because the objects to be processed 610 and 618 are fitted to each other with a clearance fit. Although there is a constraint that the engaging operation is an engaging operation restricted by the clearance, it may be any kind of operation on one or both of the engaged first and second objects to be processed 610 and 618 with respect to the other. The relative engaging operation of one or both of the first and second objects to be processed 610 and 618 is schematically indicated by the arrows "6B 1 ", "6B 2 " in FIG. 6B. The first and second objects to be processed 610 and 618 are preferably pressed against each other while receiving the engaging operation, that is, the engaged objects to be processed 610 and 618 are preferably biased against each other in the opposite directions indicated by the arrows "6A 1 ", "6A 2 " in FIG. 6B. After the engaging surfaces 612 and 620 are engaged with each other, the objects to be processed 610 and 618 are continuously biased against each other until they are joined or bonded.

[0121] While the heated portions 628 and 630 are at the hot working temperature and the engaging surfaces 612 and 620 are biased against each other, it is preferable that an engaging operation is performed on one or both of the objects to be processed 610 and 618. The engaging operation may be any operation that relatively moves one or both of the objects to be processed 610 and 618 with respect to the other. The relative movement may be repeated regularly (for example, at a preselected time interval) or irregularly.

[0122] For example, one or both of the objects to be processed 610 and 618 may be moved on the same plane with respect to the other as schematically indicated by the arrows "6B 1 ", "6B 2 " in FIG. 6B. In the embodiments shown in FIGS. 6A and 6B, it will be understood that such an operation is necessarily restricted by a predetermined clearance.

[0123] As shown in FIG. 6A, the ridges 614, 622 are formed to be located on the proximal end side of the heating element 627 during heating. Preferably, the heat insulating elements 642, 644 are disposed between the ridges 614, 622 and the heating element 627. The ridges 614, 622 are formed to isolate the heated portions 628, 630 from the main body portions 632, 634 to a limited extent, that is, to at least partially isolate the portions heated to the hot working temperature in the workpieces 610, 618 from the portions not heated to the hot working temperature. As described above, the engaging surfaces 612, 620 are formed to limit the range in which the volume of the heated portions 628, 630 is continuous with the volume of the corresponding main body portions 632, 634, thereby restricting the degree of heat transfer from the heated portions 628, 630 to the main body portions 632, 634.

[0124] As shown in FIG. 6B, when the first and second engaging surfaces 612, 620 are engaged with each other, at the engaging surfaces of the valleys 616, 624, the workpieces 610, 618 are not at the hot working temperature. However, the ridges 614, 622 are at the hot working temperature. As described above, when the workpieces 610, 618 are engaged with each other, a relatively restricted relative (engaging) movement is performed on one or both of the workpieces. It is considered that sufficient heat for joining the material of the workpiece is transferred from each ridge to the corresponding valley through the engaging surfaces 612, 620.

[0125] In practice, when the high thermal conductivity material is aluminum, since the aluminum oxide layer may prevent bonding, it is necessary to deal with the aluminum oxide layer formed on aluminum in the ambient atmosphere. For example, the engaging surfaces 612, 620 of the first and second workpieces 610, 618 may be formed (e.g., by cutting and polishing) immediately before the engaging surfaces are surrounded by an inert atmosphere. Alternatively, even if the engaging surfaces are not cut or polished, the oxide layer may be sufficiently broken when a shearing force is applied to the engaging material.

[0126] As described above, at least a part of the heated portion is plastically deformed and sheared during the engaging operation to form a region (not shown in FIG. 6B) having a substantially uniform microstructure including the engaging surface, metallurgically joining or bonding the object to be processed.

[0127] In an alternative embodiment, heat insulation elements 642, 644 are disposed between the objects to be processed 610, 618, and openings 646, 648 are disposed on the opposite sides of the first and second valleys 616, 624 (FIGS. 6C, 6D). For clarity of illustration, in FIG. 6C, the first and second heated portions are denoted by reference numerals 1628, 1630, and the first and second main body portions are denoted by reference numerals 1632, 1634.

[0128] Preferably, the first and second objects to be processed 610, 618 are disposed at a predetermined distance "6D" from each other, and the first and second engaging surfaces 612, 620 are disposed opposite to each other with a gap 626 provided therebetween (FIG. 6C).

[0129] One or more heating elements 627 are disposed in the gap 626 to heat the first and second heated portions 1628, 1630 near the first and second engaging surfaces 612, 620 to the first and second hot working temperatures at which the first and second heated portions 1628, 1630 are plastically deformed in the first and second valleys 616, 624, respectively.

[0130] Preferably, next, at least the first and second heated portions 1628, 1630 are covered with an inert atmosphere. Those skilled in the art can understand that the inert atmosphere is preferably contained in a suitable container (not shown).

[0131] Preferably, one or more heat insulation elements are disposed between the heating element 627 and the first engaging surface 612 to moderate the degree to which the first heated portion 1628 is heated, that is, to limit the heat transfer rate from the first heated portion 1628 to the first main body portion 1632.

[0132] In the embodiment shown in FIG. 6C, two heat insulation elements 642, 644 are shown. As shown in FIG. 6C, the first heat insulation element 642 is disposed between the heating element 627 and the first engagement surface 612. The second heat insulation element 644 is disposed between the heating element 627 and the second engagement surface 620. The second heat insulation element 644 is configured to mitigate the degree to which the second heated portion 1630 is heated, that is, to limit the rate of heat transfer from the second heated portion 1630 to the second main body portion 1634.

[0133] In one embodiment, preferably, the first and second heat insulation elements 642, 644 each have first and second openings or slots 646, 648. Preferably, the heat insulation elements are arranged such that the openings 646, 648 are respectively aligned with the first and second valleys 616, 624, that is, are located on the opposite sides of the valleys. As a result, the first and second valleys 616, 624 are heated by the heating element 627 (e.g., by induction), while the main body portions 649, 651 of the first and second heat insulation elements 642, 644 are respectively disposed between the heating element 627 and the ridges 614, 622, so the ridges 614, 622 are not heated as much.

[0134] The heating element 627 preferably heats the heated portions 1628, 1630 by induction. Therefore, it is preferable that the heat insulation elements 642, 644 are configured to mitigate the degree to which the first and second heated portions 1628, 1630 are heated by induction heating via the heating element 627.

[0135] In FIG. 6C, only one heating element 627 is shown for clarity of illustration. As shown in FIG. 6C, when the heating element 627 is disposed in the gap 626, it is preferable that first and second slots are formed by the heating element 627 between (i) the heating element 627 and the first engagement surface 612, and (ii) the heating element 627 and the second engagement surface 620, and the first and second heat insulation elements 642, 644 are disposed therein.

[0136] Depending on the situation, only one of the heat insulation elements 642, 644 may be used. At least the heated parts of the first and second objects to be processed are covered by an inert atmosphere (not shown).

[0137] The heated parts 1628, 1630 of the first and second objects to be processed 610, 618 may be heated to different hot working temperatures by the heat insulation elements 642, 644. However, those skilled in the art can understand that, alternatively, the first and second heated parts 1628, 1630 may be heated to the same or substantially the same hot working temperature.

[0138] Preferably, by energizing the heating element 627, the first heated part 1628 of the first object to be processed 610 and the second heated part 1630 of the second object to be processed 618 are heated to the first and second hot working temperatures, respectively.

[0139] For clarity of illustration, in FIGS. 6A and 6C, the dashed lines labeled 636, 638 respectively indicate (i) the ideal boundary line between the first heated part 1628 and the first main body part 1632, and (ii) the ideal boundary line between the second heated part 1630 and the second main body part 1634. As described above, the temperatures of the first and second main body parts 1632, 1634 are lower than the hot working temperature.

[0140] Therefore, the dashed lines 636, 638 indicate the locations of the objects to be processed 610, 618 where the temperature is lower than the hot working temperature. Those skilled in the art can understand that since the illustrated boundary lines 636, 638 are represented as straight lines, they are approximate lines, but in reality, they may not be such lines. Those skilled in the art can also understand that in reality, the position of the boundary line between the heated part and the adjacent main body part may change in a short time as heat is transferred from the heated part to the main body part. From the above, the straight dashed lines 636, 638 represent the boundary lines between the parts 1628, 1630 of the objects to be processed 610, 618 at the hot working temperature and the parts 1632, 1634 at a temperature lower than the hot working temperature, and it can be seen that they are simplified for illustration purposes.

[0141] When the first and second heated portions 1628 and 1630 are in a plastically deformable state, the first and second engaging surfaces 612 and 620 engage with each other, one or more of the engaging surfaces are moved relative to the other engaging surfaces, and the first and second objects to be processed 610 and 618 are joined to each other. The heating element 627 and the heat insulating elements 642 and 644 are preferably removed before the first and second engaging surfaces 612 and 620 are engaged with each other.

[0142] In one embodiment, with respect to the first and second objects to be processed 610 and 618, while the heated portions are at the hot working temperature, a dislocation operation is preferably performed in the directions indicated by the arrows "6A 3 ", "6A 4 ". As a result, the first and second engaging surfaces 612 and 620 engage with each other.

[0143] Also, preferably, while the heated portions 1628 and 1630 are at the hot working temperature, an engaging operation is performed on at least one of the first and second objects to be processed 610 and 618, or on both of the first and second objects to be processed 610 and 618, and they are engaged with each other and biased together. The engaging operation may be any kind of operation in which one or both of the engaged first and second objects to be processed 610 and 618 move relative to the other. The first and second objects to be processed 610 and 618 are preferably pressed against each other while receiving the engaging operation, that is, the engaged objects to be processed 610 and 618 are preferably biased against each other in the opposite directions indicated by the arrows "6A 3 ", "6A 4 " in FIG. 6C. After the engaging surfaces 612 and 620 are engaged with each other, the objects to be processed 610 and 618 are continuously biased against each other until they are combined or joined.

[0144] Since valleys 616, 624 are located farther from heating element 627 than peaks 614, 622, it is considered necessary to expose the heated portions 1628, 1630 in the vicinity of valleys 616, 624 to the energized heating element 627 for a long time. A person skilled in the art can understand that the arrangement shown in FIG. 6C is beneficial, for example, when it is desired to delay the transfer of thermal energy from the heated portions 1628, 1630 to the main body portions 632, 634. For example, when the thermal conductivity of the materials of the objects to be processed 610, 618 is high, it may be beneficial to limit (i.e., slow down) the heat transfer from the heated portions 1628, 1630 to the main body portions 1632, 1634. Also, when the objects to be processed are made of materials with different thermal conductivities, the heat insulating elements can be arranged at different positions for each object to be processed. For example, the heat transfer rate within an object made of a high thermal conductivity material can be slowed down. In such a situation, the heating element 627 may be arranged at a location that is not equidistant from the object to be processed to limit the heat transfer rate within one object to be processed.

[0145] The heated portions 1628, 1630 tend to adhere to each other when engaged, and shear occurs due to the engaging operation in the state of being engaged at the hot working temperature. Due to the shearing action, the fine structure of the metal in the heated material is torn, and a region "6R" of recrystallized metal is formed across the original engaging surfaces 612, 620, and the engaging surfaces are included in the region "6R" (FIG. 6D). In this way, the objects to be processed 610, 618 are metallurgically joined. As the metal is sheared and cooled, recrystallization of the metal occurs, and as a result, a relatively uniform and fine microstructure is formed across the entire region "6R" (FIG. 6D) where the objects to be processed 610, 618 are joined or bonded, and the original engaging surfaces are at least partially included.

[0146] The metallurgical joining region "6R" is slightly smaller than the heated portions 1628, 1630 and may not be substantially linear as shown in FIG. 6D. The width of the region "6R" shown in FIG. 6D is exaggerated for clarity of illustration.

[0147] As described above, the objects to be processed 610, 618 are joined or bonded to form the product 639 (FIG. 6D). The first and second objects to be processed are joined over the region "6R", and the microstructure within the region "6R" is a substantially uniform and relatively fine microstructure, resulting in a strong bond.

[0148] In another embodiment, it is preferable that the objects to be processed 710, 718 are each formed with engagement surfaces 712, 720 (FIG. 7A). The objects to be processed 710, 718 are pipes or tubes. The first object to be processed 710 has a first main body portion 732, and the second object to be processed 718 has a second main body portion 734. Preferably, the objects to be processed 710, 718 are axially aligned. That is, the axes of the objects to be processed 710, 718 are linearly arranged.

[0149] Preferably, the first engaging portion 750 of the first object to be processed 710 has the first engagement surface 712. Preferably, the first object to be processed 710 has a first bridge portion 752 located between the first engaging portion 750 and the first main body portion 732 and connected to the first engaging portion 750 and the first main body portion 732. Similarly, the second object to be processed 718 preferably has a second engaging portion 754 and a second bridge portion 756 located between the second engaging portion 754 and the second main body portion 734.

[0150] In one embodiment, preferably, the first and second objects to be processed 710, 718 are formed of aluminum or other metals having a relatively high thermal conductivity. As shown in FIG. 7A, the bridge portions 752, 756 are preferably narrower (in cross-section) than the engaging portions and main body portions to which they are connected. By narrowing the bridge portions 752, 756, it is considered that the heat transfer from the engaging portions 750, 754 to the main body portions 732, 734 is limited to some extent.

[0151] Preferably, the first and second workpieces 710, 718 are arranged such that the engagement surfaces 712, 720 are separated by a predetermined distance "7D", face each other, and a gap 726 is provided therebetween. Preferably, one or more heating elements 727 are arranged within the gap 726. As will be described later, preferably, one or more guiding elements 762 are provided to guide each workpiece when the workpieces 710, 718 move towards each other. Preferably, at least the engaging portions 750, 754, the bridge portions 752, 756, and the main body portions 732, 734 are covered or surrounded by a single or a plurality of inert (non-oxidizing) gases. In FIGS. 7A to 7C, for clarity of illustration, the inert gas and one or more covers or containers holding the inert gas are omitted.

[0152] The heating element 727 is energized, and the first heated portions 728, 730 of the workpieces 710, 718 are heated to a hot working temperature at which the first heated portions 728, 730 become plastically deformable. Any suitable heating method (e.g., induction heating or radiant heating) can be used for the heating element. When the first heated portions 728, 730 reach the hot working temperature, the heating element 727 is removed.

[0153] In one embodiment, at least a part of the bridge portions 752, 756 is included in the first heated portions 728, 730. However, for clarity of illustration, in FIG. 7A, the first heated portions 728, 730 are shown to be limited to the engaging portions 750, 754 at least for a short time immediately after the heating element is removed.

[0154] As shown in FIGS. 7A and 7B, when the first heated portions 728, 730 are heated to the hot working temperature, with respect to one or both of the first and second workpieces 710, 718, arrows "7A" 1 ", "7A" 2The dislocation operation indicated by "」 is performed, and the engagement surfaces 712 and 720 are brought closer to engage with each other. The objects to be processed 710 and 718 are guided by the guiding elements 762 during movement and maintain an axially aligned state. In one embodiment, once engaged, as will be described later, the objects to be processed 710 and 718 are biased together until they are joined to each other.

[0155] Preferably, as schematically indicated by the arrows "7B 1 」,「7B 2 」, an engagement operation is performed on one or both of the objects to be processed 710 and 718. The engagement operation is any suitable operation of the other object to be processed with respect to one object to be processed. For example, the engagement operation may include an operation in the z direction, that is, an operation orthogonal to the plane of the drawing.

[0156] By the engagement operation while the engagement surfaces 712 and 720 are engaged, the engagement surfaces 712 and 720 are plastically deformed, and a layer 764 generally made of a plastic material is temporarily formed as shown in Fig. 7B. In Fig. 7B, the thickness of the layer 764 of the plastically deformable material is exaggerated for clarity of illustration.

[0157] Those skilled in the art can understand that thermal energy is transferred from the first heated portions 728 and 730 to the bridge portions 752 and 756 connected thereto respectively by conduction. Also, the hot working temperature is a given range of temperature lower than the melting temperature, and the hot working temperature of the bridge portions 752 and 756 is slightly lower than the hot working temperature of the first heated portions 728 and 730. For this reason, after the plastic material layer 764 is formed, the remaining portions of the engagement portions 750 and 754 and the bridge portions 752 and 756 also reach the hot working temperature.

[0158] By urging the objects to be processed 710 and 718 against each other, the bridge portions 752 and 756 are broken, and a second layer 766 generally made of a plastic material is temporarily formed (FIG. 7C). By moving one or more objects to be processed relative to each other to shear and plastically deform the layer 766, a substantially uniform fine structure recrystallized within the layer is formed.

[0159] Next, when the objects to be processed 710 and 718 are cooled to the ambient temperature and the layers 764 and 766 are cooled, the objects to be processed 710 and 718 are joined, and the product 739 (FIG. 7C) is formed as described above. Similarly to the above, the objects to be processed are metallurgically joined or bonded across the region "7R" of the product 739, and the fine structure in this region "7R" is characterized by having a substantially uniform grain size that has been recrystallized.

[0160] In practice, when the high thermal conductivity material is aluminum, since the aluminum oxide layer may prevent bonding, it is necessary to deal with the aluminum oxide layer formed on aluminum under the ambient atmosphere. For example, the engagement surfaces 712 and 720 of the first and second objects to be processed 710 and 718 may be formed (e.g., by cutting and polishing) immediately before the engagement surfaces are surrounded by an inert atmosphere. Alternatively, even if the engagement surfaces are not cut or polished, the oxide layer may be sufficiently broken when a shearing force is applied to the engaging materials.

[0161] In an alternative embodiment of the method of the present invention, after the engagement surfaces are first engaged, the dislocation operation may be interrupted for a short time. That is, after the engagement surfaces 712 and 720 are first engaged with each other and a temporary plastic material layer 764 is formed, for a predetermined short time, the objects to be processed are engaged with each other but are not further urged together. The engagement operation continues for this predetermined short time. That is, the layer 764 is sheared at this point.

[0162] During a predetermined short time, heat is further transmitted to the bridge portions 752, 756 by conduction, that is, it is considered to be further transmitted from the first heated portions 728, 730 respectively connected to the bridge portions 752, 756. Also, preferably, the material 764 solidifies during this predetermined short time. After the predetermined short time, the workpieces are biased against each other again (in the directions indicated by the arrows "7A 1 ", "7A 2 "), and the engaging operation is resumed. As a result, the workpieces are joined or bonded to form the product 739. Alternatively, after the predetermined short time, the engaging operation is continued (or, in some cases, resumed), and then the workpieces are biased against each other.

[0163] In another embodiment, the workpieces 1710, 1718 have first and second engaging portions 1750, 1754 including engaging surfaces 1712, 1720 (FIG. 7D). As shown in FIG. 7D, preferably, the first and second engaging portions 1750, 1754 extend over the entire or substantially the entire diameters 1767, 1768 of the first and second workpieces 1710, 1718. The first workpiece 1710 has a first main body portion 1732, and the second workpiece 1718 has a second main body portion 1734. Preferably, the workpieces 1710, 1718 are axially aligned, and the axes 1719A, 1719B of the workpieces 1710, 1718 are linearly arranged.

[0164] Preferably, the first engaging portion 1750 of the first workpiece 1710 has the first engaging surface 1712. Preferably, the first workpiece 1710 is located between the first engaging portion 1750 and the first main body portion 1732, and also has a first bridge portion 1752 connected between the first engaging portion 1750 and the first main body portion 1732. Similarly, the second workpiece 1718 preferably has a second engaging portion 1754 and a second bridge portion 1756 located between the second engaging portion 1754 and the second main body portion 1734.

[0165] Preferably, the first and second objects to be processed 1710, 1718 are formed of aluminum or other metals having a relatively high thermal conductivity. As shown in FIG. 7D, the bridge portions 1752, 1756 are preferably narrower than the engaged portions and the main body portions to which they are connected. By narrowing the bridge portions 1752, 1756, it is considered that the heat transfer from the engaged portions 1750, 1754 to the main body portions 1732, 1734 is limited to some extent.

[0166] Preferably, the first and second objects to be processed 1710, 1718 are arranged such that the engaging surfaces 1712, 1720 are separated by a predetermined distance " 2 7D

[0167] ", and a gap 1726 is provided therebetween. Preferably, one or more heating elements 1727 are arranged within the gap 1726. As will be described later, preferably, one or more guiding elements 1762 are provided to guide each object to be processed when the objects to be processed 1710, 1718 move towards each other. Preferably, the engaging surfaces 1712, 1720, at least the engaged portions 1750, 1754 and the bridge portions 1752, 1756 are covered or surrounded by an inert gas. In FIGS. 7D - 7F, for clarity of illustration, the inert gas and one or more covers or containers for holding the inert gas are omitted.

[0168] In one embodiment, the first heated portions 1728, 1730 may include at least a part of the bridge portions 1752, 1756. However, for clarity of illustration, in FIG. 7D, at least for a short time immediately after the heating element is removed, the first heated portions 1728, 1730 are shown to be limited to the engaged portions 1750, 1754.

[0169] As shown in FIGS. 7D and 7E, when the heated portion is heated to the hot working temperature, a dislocation operation indicated by the arrows "7A 3 ", "7A 4 " is performed on one or both of the first and second objects to be processed 1710, 1718, and the engagement surfaces 1712, 1720 are brought closer to each other so as to engage with each other. The objects to be processed 1710, 1718 are guided by the guide elements 1762 during movement and maintain an axially aligned state. In one embodiment, once engaged, the objects to be processed 1710, 1718 are biased together until the first and second objects to be processed 1710, 1718 are joined, as will be described later.

[0170] Preferably, an engagement operation is performed on one or both of the objects to be processed 1710, 1718, as schematically indicated by the arrows "7B 3 ", "7B 4 ". The engagement operation is any suitable operation of the other object to be processed with respect to one object to be processed. For example, the engagement operation may include an operation in the z direction, that is, an operation perpendicular to the plane of the drawing.

[0171] Due to the engagement operation while the engagement surfaces 1712, 1720 are engaged, the engagement surfaces 1712, 1720 are plastically deformed, and a layer 1764 generally made of a plastic material is temporarily formed as shown in FIG. 7E. In FIG. 7E, the thickness of the layer 1764 is exaggerated for clarity of illustration.

[0172] Those skilled in the art can understand that the thermal energy is transmitted by conduction from the initial heated portions 1728, 1730 to the bridge portions 1752, 1756 respectively connected thereto. Also, the hot working temperature is a given range of temperature lower than the melting temperature, and the hot working temperature of the bridge portions 1752, 1756 is slightly lower than the hot working temperature of the initial heated portions 1728, 1730. For this reason, after the plastic material layer 1764 is formed, the remaining portions of the engaging portions 1750, 1754 and the bridge portions 1752, 1756 also reach the hot working temperature.

[0173] By urging the objects to be processed 1710 and 1718 against each other, the bridge portions 1752 and 1756 are broken, and a second layer 1766 generally made of a plastic material is temporarily formed (FIG. 7F). Next, when the objects to be processed 1710 and 1718 are cooled to the ambient temperature and the layers 1764 and 1766 are cooled, the objects to be processed 1710 and 1718 are joined, and the product 1739 (FIG. 7F) is formed as described above.

[0174] The objects to be processed are joined in the region "7R" 2 ". The microstructure of the product 1739 is characterized by having a recrystallized substantially uniform grain size. In practice, when the high thermal conductivity material is aluminum, since the aluminum oxide layer may prevent bonding, it is necessary to deal with the aluminum oxide layer formed on aluminum in an ambient atmosphere. For example, the engaging surfaces 1712 and 1720 of the first and second objects to be processed 1710 and 1718 may be formed (e.g., by cutting and polishing) immediately before the engaging surfaces are surrounded by an inert atmosphere. Alternatively, even if the engaging surfaces are not cut or polished, the oxide layer may be sufficiently broken when a shearing force is applied to the engaging materials.

[0175] In an alternative embodiment of the method of the present invention, after the engaging surfaces are first engaged, the dislocation operation may be interrupted for a short time. That is, after the engaging surfaces 1712 and 1720 are first engaged with each other and a temporary layer 1784 of plastic material is formed, for a predetermined short time, the objects to be processed are engaged with each other but are not further urged together. The engaging operation is continued over this predetermined short time. That is, the layer 1764 is sheared at this point.

[0176] During a predetermined short time, heat is further transferred to the bridge portions 1752, 1756 by conduction, that is, it is considered to be further transferred from the first heated portions 1728, 1730 respectively connected to the bridge portions 1752, 1756. Also preferably, the material 1764 solidifies within this predetermined short time. After the predetermined short time, the objects to be processed are biased against each other again, and the engaging operation is resumed. As a result, the objects to be processed are joined to form the product 1739. Alternatively, after the predetermined short time, the engaging operation is continued (or, in some cases, resumed), and then the objects to be processed are biased against each other.

[0177] In another alternative embodiment, two objects to be processed 810, 818 are provided, and a third object to be processed 870 is formed to fit between them (FIG. 8A). Preferably, the first and second objects to be processed 810, 818 each have first and second engaging surfaces 812, 820, and fins 815, 823 are respectively attached to the engaging surfaces 812, 820. The fins 815, 823 extend from the first and second engaging surfaces 812, 820 respectively (FIG. 8A). The third object to be processed 870 has third and fourth engaging surfaces 872, 874 formed to fit against the first and second engaging surfaces 812, 820, and fins are located between them.

[0178] Preferably, the objects to be processed 810, 818, 870 are formed of aluminum or other metals having a relatively high thermal conductivity. Preferably, the first and second objects to be processed 810, 818 are arranged at a predetermined distance "8D" apart, and a gap 869 is formed therebetween (FIG. 8A).

[0179] As shown in FIG. 8A, the third object to be processed 870 is preferably initially arranged outside the gap 869 and spaced apart from the engaging surfaces 812, 820 of the first and second objects to be processed 810, 818. Preferably, one or more third heating elements 827A are arranged on the proximal ends of the engaging surfaces 872, 874 of the third object to be processed 870.

[0180] Also, preferably, one or more first and second heating elements 827B, 827C are disposed on the proximal ends of the fins 815, 823 and the engagement surfaces 812, 820. The third heating element 827A is an element for heating the third heated portion 876 of the object to be processed 870 to the hot working temperature. The first and second heating elements 827B, 827C are elements for heating the first and second heated portions 878, 880 of the first and second objects to be processed 810, 818. Any suitable heating method (induction heating, radiant heating, etc.) can be used for the heating elements 827A, 827B, 827C. When the heated portion is at the hot working temperature, the material of the heated portion becomes plastically deformable. The sizes of the heated portions 876, 878, 880 shown in FIG. 8A are exaggerated for clarity of illustration. Also, the first and second heated portions 878, 880 preferably include at least a part of the fins 815, 823, but may or may not include a part of the engagement surfaces 812, 820.

[0181] The engagement surfaces 812, 820, the fins attached to the engagement surfaces 812, 820, and the second heating element 827B are preferably covered or surrounded by an inert atmosphere. Similarly, the engagement surfaces 872, 874 and the heating element 827A are preferably covered or surrounded by an inert atmosphere. In FIGS. 8A to 8C, for clarity of illustration, the inert atmosphere and the cover or container for maintaining the inert atmosphere are omitted.

[0182] Next, by energizing the heating elements, each heated portion is heated to the hot working temperature. Preferably, when the heated portion is heated to the hot working temperature, the heating elements 827A, 827B, 827C are removed, and the third object to be processed 870 is moved in the direction indicated by the arrow "8A" in FIG. 8A by performing a dislocation operation on the third object to be processed 870 with respect to the other objects to be processed 810, 818. In one embodiment, it is preferable that an engagement operation is performed when the third object to be processed 870 is moved toward the objects to be processed 810, 818 as schematically shown by the arrow "8B".

[0183] As shown in FIG. 8B, the third object to be processed 870 is moved in the direction indicated by the arrow "8A", and the fins 815, 823 are engaged with the complementary engagement surfaces 872, 874 respectively, and the fins 815, 823 are pressed between the complementary engagement surfaces 872, 874 and the first and second engagement surfaces 812, 820.

[0184] As shown in FIG. 8A, according to the initial position of the third object to be processed 870 with respect to the first and second objects to be processed 810, 818, the heating element 827 may be arranged on the base end side of the complementary engagement surfaces 872, 874 and on the tip end side of the fins 815, 823. Since the fins 815, 823 are relatively thin, it is considered that the fins 815, 823 will reach the hot working temperature or a temperature close thereto when engaged with the complementary engagement surfaces 872, 874. Also, it is considered that the first and second engagement surfaces 812, 820 are heated up to the hot working temperature or a temperature close to the hot working temperature.

[0185] While the first, second, and third heated parts are at the hot working temperature, they engage with each other (FIG. 8B). Preferably, after being engaged in this way, an engagement operation is performed on the third object to be processed 870. The engagement operation may be any relative movement performed while engaging. The engagement operation is schematically shown by the arrow "8B" in FIG. 8B. The engagement operation may be performed in the z direction, that is, the direction perpendicular to the plane of the drawing. Further, after such engagement, the third object to be processed 870 is biased in the direction indicated by the arrow "8A" in FIG. 8B.

[0186] Also, while the third object to be processed 870 is engaged with one or both of the first and second objects to be processed 810, 818, for example, one or more engagement operations on the third object to be processed 870 are performed.

[0187] This engaging operation, the fact that the third workpiece is biased in the direction indicated by arrow "8A" after the first engagement, and the engaging complementary surfaces 872, 874, fins 815, 823 and engaging surfaces 812, 820 being at or near the hot working temperature cause a plastically deformable metal region 866 to be formed between the third workpiece and the first and second workpieces (FIG. 8C), which undergoes plastic deformation under shear while at the hot working temperature. The engaging surfaces 812, 820, 872, 874 are at least partially included in region 866. The material of region 866 recrystallizes to form a fine structure with a relatively uniform grain size, and when region 866 drops below the hot working temperature, the third workpiece 870 metallurgically joins or bonds to the first and second workpieces 810, 818.

[0188] In practice, when the high thermal conductivity material is aluminum, since the aluminum oxide layer may prevent bonding, it is necessary to deal with the aluminum oxide layer formed on aluminum under the ambient atmosphere. For example, the engaging surfaces 812, 820 of the first and second workpieces 810, 818 and the complementary engaging surfaces 872, 874 may be formed (e.g., by cutting and polishing) immediately before the engaging surfaces are surrounded by an inert atmosphere. Alternatively, even if the engaging surfaces are not cut or polished, the oxide layer may be sufficiently broken when a shearing force is applied to the materials being engaged.

[0189] As shown in FIGS. 9A and 9B, in one embodiment, the method of the present invention includes providing a first workpiece 910 having a first engaging surface 912. Preferably, the first engaging surface 912 forms a plane 929 (FIG. 9A). Also provided is a second workpiece 918 having a second engaging surface 920 with a plurality of second ridges 922 and second valleys 924 provided alternately.

[0190] As shown in FIG. 9A, preferably, the first and second workpieces 910, 918 are arranged at a predetermined distance "9D" from each other, with the first and second engaging surfaces 912, 920 facing each other and a gap 926 being formed therebetween.

[0191] Preferably, one or more heating elements 927 are disposed in the gap 926 to heat the first and second heated portions 928, 930 of the workpieces 910, 918 to one or more hot working temperatures at which the first and second heated portions are at least partially plastically deformable. Any suitable heating method (e.g., induction heating or radiant heating) can be used for the heating element 927. As will be described later, preferably, the first heated portion 928 is located near the first engagement surface 912. Preferably, the second heated portion 930 is located near the second peak portion 922 of the second engagement surface 920.

[0192] In one embodiment, the first and second workpieces 910, 918 are preferably formed of different first and second materials (metals). The first and second materials may be materials having different melting points, and thus, the hot working temperatures at which they become plastically deformable may be different. The two different materials may each have different first and second thermal conductivities. For example, the first workpiece 910 may be made of steel and the second workpiece 918 may be formed of aluminum.

[0193] Preferably, when the heating element 927 is energized, the heated portions 928, 930 are first heated to the hot working temperature. When the first and second heated portions 928, 930 are heated to the hot working temperature, first and second body portions 932, 934 are respectively formed in the first and second workpieces 910, 918. The first and second body portions 932, 934 are not initially heated to the hot working temperature. The first and second body portions 932, 934 are connected to the first and second heated portions 928, 930, but are portions of the first and second workpieces 910, 918 that are not initially heated to the hot working temperature. However, those skilled in the art can understand that when the first and second heated portions are heated to the hot working temperature, the temperature of the body portions 932, 934 also rises mainly by conduction.

[0194] In use, as shown in Fig. 9A, first, the first and second objects to be processed 910, 918 are arranged at a distance of "9D" apart, and a heating element 927 is arranged therebetween. Preferably, at least the first and second heated portions 928, 930 are covered with an inert (non-oxidizing) atmosphere during heating and engagement. The inert atmosphere and its container are omitted in the drawings for clarity.

[0195] Next, preferably by energizing the heating element 927, both the first heated portion 928 of the first object to be processed 910 and the second heated portion 930 of the second object to be processed 918 are heated to the hot working temperature. When the first and second objects to be processed are formed of materials with different melting points, the first and second objects to be processed are heated to the first and second hot working temperatures respectively. To facilitate this, the heating element 927 can be arranged as required for the object to be processed. For example, the heating element 927 can be arranged at different positions from the object to be processed.

[0196] When the heated portions 928, 930 reach their respective hot working temperatures, the heating element 927 is removed from the gap 926. As shown in Figs. 9A and 9B, when the heated portions 928, 930 reach the hot working temperature, a dislocation operation is preferably performed on one or both of the first and second objects to be processed 910, 918, as indicated by the arrows "9A 1 ", "9A 2 " in Fig. 9B. By this dislocation operation, the engagement surfaces 912, 920 are engaged with each other. There may be cases where the dislocation operation is performed on both objects to be processed, or one of them, i.e., the first object to be processed 910 or the second object to be processed 918, or both of them may be moved towards the other.

[0197] While the first and second heated portions are at their respective hot working temperatures and the first and second engagement surfaces are engaged, preferably, the first and second engagement surfaces are biased in the directions indicated by the arrows "9A 1 ", "9A 2 ".

[0198] Also, preferably, while the heated parts 28, 30 are at the hot working temperature, an engaging operation is performed on one or both of the first and second objects to be processed 910, 918, and they are engaged with each other and biased together (FIG. 9B). The relative engaging operation of one or both of the first and second objects to be processed 910, 918 is indicated schematically by the arrows "9B 1 ", "9B 2 " in FIG. 9B. Such movement is possible while the heated portion is plastically deformable, i.e., while at the hot working temperature. Also, movement in the z direction (i.e., the direction perpendicular to the plane of the drawing) is possible.

[0199] The engaging operation may be any kind of operation in which one or both of the engaged first and second objects to be processed 910, 918 move relative to the other, whether regularly repeated or not. While the first and second objects to be processed 910, 918 are engaged with each other, they are pressed against each other, i.e., at the time of engagement, the objects to be processed 910, 918 are preferably biased together in opposite directions indicated by the arrows "9A 1 ", "9A 2 " in FIG. 9B. After the engaging surfaces 912, 920 are engaged with each other and the engaging operation is performed on the objects to be processed 910, 918, as will be described later, it is preferable that the objects to be processed 910, 918 are continuously biased together until they are joined.

[0200] Those skilled in the art can understand that the mountain portion 922 and the valley portion 924 are configured to limit the heat transfer by conduction from the heated portion 930 to the second main body portion 934. The mountain portion 922 is formed so as to limit the range in which the volume of the heated portion 930 is continuous with the volume of the corresponding main body portion 934, thereby limiting the range of heat transfer by conduction from the heated portion 930 to the main body portion 934.

[0201] Since the degree of heat transfer from the heated part to the main body part is limited, as will be described later, after the heated part 930 is first heated to the hot working temperature, the heated part 930 is maintained at the hot working temperature for a sufficiently long time so that it can be joined to the heated part 928 by an engaging operation.

[0202] As described above, in one embodiment, the object to be processed 918 may be made of one or more metals or materials having a relatively high thermal conductivity. Those skilled in the art are well aware of metals (including alloys) having a relatively high thermal conductivity such as aluminum. As soon as the heated part 930 is heated to the hot working temperature, thermal energy is transferred to some extent by conduction from the heated part 930 to the vicinity of the main body part 934.

[0203] In the example shown in FIGS. 9A to 9C, the first object to be processed 910 is formed of a metal or a material having a relatively low thermal conductivity, such as steel. Therefore, when the heated part 928 is heated, heat transfer from the heated part 928 to the main body part 932 starts almost immediately, but the heat transfer to the main body part 932 is relatively slow.

[0204] From the above, it is understood that when the object to be processed is formed of metals or materials having significantly different thermal conductivities, the engaging surfaces of the object to be processed may have different configurations. The engaging surface can be configured by any suitable method in order to sufficiently limit the heat transfer rate from the heated part to the main body part of the object to be processed.

[0205] Also, for clarity of illustration, the sizes of the ridges 922 and valleys 924 are exaggerated. Since the metals of the objects to be processed are different, the heated parts 928 and 930 are heated to different first and second hot working temperatures, respectively.

[0206] The materials within the heated portions 928, 930 at the hot working temperature are very thin layers, and the thicknesses of the heated portions 928, 930 shown in FIGS. 9A and 9B are exaggerated for clarity of illustration. As described above, the engagement surfaces 912, 920 are maintained at each hot working temperature for a short time after engagement. That is, each layer has a temperature at which it can be plastically deformed for a relatively short time. The heated materials engaged in the heated portion tend to adhere to each other, and in the state of being engaged at the hot working temperature, shear due to the engagement operation occurs in the heated materials. Due to the shearing action, the microstructure of the metal in the heated material is torn, and a metal region "9R" is formed across the original engagement surfaces 912, 920, and the engagement surfaces are included in the region "9R" (FIG. 9C). In this way, the workpieces 910, 918 are metallurgically joined or bonded. As the metal is sheared and cooled, recrystallization of the metal occurs, and as a result, a relatively uniform and fine microstructure is formed across the entire region "9R" (FIG. 9C) where the workpieces 910, 918 are joined, and the original engagement surfaces are at least partially included.

[0207] The metallurgical bonding region "9R" is slightly smaller than the heated portions 928, 930 and may not be substantially linear as shown in FIG. 9C. The width of the region "9R" shown in FIG. 9C is exaggerated for clarity of illustration.

[0208] As described above, the workpieces 910, 918 are combined or joined to form a product 939 (FIG. 9C). The first and second workpieces are joined across the region "9R", and the microstructure within the region "9R" is substantially uniform and relatively fine, resulting in a strong bond.

[0209] The present invention can be implemented in many forms, and these forms are within the scope of the present invention described in the claims. The claims should not be limited by the preferred embodiments described in the examples, but should be given the broadest interpretation consistent with the overall description.

Claims

1. 1. A method comprising: (a) providing a first workpiece (10) having a first engagement surface (12) including a plurality of alternating first peaks (14) and first valleys (16); (b) providing a second workpiece (18) having a second engagement surface (20) including a plurality of alternating second peaks (22) and second valleys (24); (c) positioning the first and second workpieces a predetermined distance (D) from one another with the first and second engagement surfaces facing one another to form a gap (26) between the first and second engagement surfaces; (d) disposing at least one heating element (27) in the gap (26) for heating first and second heated portions (28, 30) located in the first and second peaks near the first and second engagement surfaces (12, 20), respectively, to a hot working temperature at which the first and second heated portions are plastically deformable, the first and second heated portions being located at base ends of the first and second peaks to limit transfer of heat from the first and second heated portions to first and second body portions of the first and second workpieces, respectively, the first and second body portions being adjacent to the first and second heated portions and having a temperature lower than the hot working temperature; (e) covering at least the first and second heated portions with an inert atmosphere; (f) energizing the at least one heating element to heat the first heated portion of the first work piece and the second heated portion of the second work piece to the hot working temperature; (g) removing the at least one heating element from the gap when the first and second heated portions (28, 30) are at the hot working temperature, and engaging the first and second engagement surfaces (12, 20) with one another by performing a transposition operation on one or both of the first and second workpieces; (h) urging the first and second mating surfaces together when the first and second heated portions are at the hot working temperature, and moving one or both of the first and second mating surfaces, which are urged together, relative to the other in an engagement motion to bond the first and second workpieces together to at least partially plastically deform the first and second heated portions. The method includes:

2. 2. The method of claim 1, wherein in step (c), the first and second workpieces (10, 18) are positioned such that the first peaks are aligned with the second valleys and the second peaks are aligned with the first valleys.

3. The method of claim 1 , wherein in step (c), the first peaks are aligned with the second peaks and the first valleys are aligned with the second valleys.

4. The method of claim 1 , wherein the first peaks are fitted into the second valleys and the second peaks are fitted into the first valleys.

5. The method of claim 1 , wherein the first and second peaks and the first and second valleys are rounded.

6. The method of claim 1 , wherein the first and second peaks and the first and second valleys are pointed.

7. 1. A method comprising: (a) providing a first workpiece (410) having a first exposed surface (413) and a plurality of first fins (415) extending from the first exposed surface (413); (b) providing a second workpiece (418) having a second exposed surface (421) and a plurality of second fins (423) extending from the second exposed surface (421); (c) disposing the first and second workpieces a predetermined distance (5D) away from each other with the first and second exposed surfaces facing each other to form a gap (426) between the workpieces (410, 418); (d) disposing at least one heating element (427) within the gap (426) for heating first and second heated portions (428, 430) extending from each end (417, 425) of the fin (415, 423) toward the first and second exposed surfaces (413, 421), respectively, to a hot working temperature at which the first and second heated portions are plastically deformable, the first and second heated portions being disposed distal to the exposed surfaces to limit transfer of heat from the first and second heated portions to first and second body portions (432, 434) of the first and second workpieces, respectively, the first and second body portions (432, 434) being adjacent to the first and second exposed surfaces (413, 421); (e) covering at least the first and second heated portions with an inert atmosphere; (f) energizing the at least one heating element (427) to heat the first heated portion of the first work piece and the second heated portion of the second work piece to the hot working temperature; (g) removing the at least one heating element from the gap (426) while the first and second heated portions (428, 430) are at a hot working temperature, and engaging the first and second fins (415, 423) with one another by performing a transposition operation on one or both of the workpieces; (h) while said first and second heated portions (428, 430) are at said hot working temperature, biasing said first and second heated portions together to press said fins of said first and second workpieces together to at least partially plastically deform said first and second heated portions, and bonding said first and second workpieces together by moving one or both of said first and second workpieces, while being biased together, relative to the other in an engaging motion. The method includes:

8. 1. A method comprising: (a) providing a first workpiece (610) including a highly thermally conductive material and having a first engagement surface (612) including a plurality of alternating first peaks (614) and first valleys (616); (b) providing a second workpiece (618) having a second engagement surface (620) including a plurality of alternating second peaks (622) and second valleys (624); (c) positioning the first and second workpieces a predetermined distance (6D) from each other with the first and second engagement surfaces facing each other to form a gap (626) between the first and second engagement surfaces; (d) disposing at least one heating element (627) within the gap for heating first and second heated portions (628, 630) located at the first and second peaks proximate the first and second engagement surfaces (612, 620) to first and second hot working temperatures, respectively, at which the first and second heated portions (628, 630) plastically deform; (e) covering at least the first and second heated portions with an inert atmosphere; (f) disposing at least one heat shield element (642, 644) between the at least one heating element and the first engagement surface to mitigate heat transfer to the first heated portion; (g) energizing the at least one heating element (627) to heat the first heated portion of the first work piece and the second heated portion of the second work piece to first and second hot working temperatures; (h) removing the at least one heating element from the gap when the first and second heated portions are at the hot working temperature and engaging the first and second engagement surfaces with each other by performing a transfer operation on one or both of the workpieces; (i) urging the first and second mating surfaces together and moving one or both of the first and second mating surfaces, when urged together, relative to the other to at least partially plastically deform the first and second heated portions when the first and second heated portions are at the hot working temperature, thereby bonding the first and second workpieces together. The method includes:

9. the at least one heat shield element (642, 644) having a body (649, 651) with an opening (646, 648) formed therein; The method of claim 8 , wherein the at least one heat shield element is positioned such that the openings are located on opposite sides of the first and second peaks.

10. the at least one heat shield element (642, 644) having a body (649, 651) with an opening (646, 648) formed therein; The method of claim 8 , wherein the at least one heat shield element is positioned such that the openings are located on opposite sides of the first and second valleys.

11. 1. A method comprising: (a) providing a first workpiece (710), the first workpiece comprising: a first engagement portion (750) having a first engagement surface (712); a first body portion (732) connected to the first engagement portion (750) by a first bridge portion (752); (b) providing a second workpiece (718), the second workpiece comprising: a second engagement portion (754) having a second engagement surface (720); a second body portion (734) connected to the second engagement portion (754) by a second bridge portion (756); (c) positioning the first and second workpieces (710, 718) a predetermined distance (7D) away from each other with the first and second engagement surfaces (712, 720) facing each other to form a gap (726) between the first and second engagement surfaces; (d) disposing at least one heating element (727) within said gap (726) to heat the initial heated portion (728, 730) to a hot working temperature; (e) covering at least the first and second engagement portions, the first and second body portions, and the first and second bridge portions with an inert atmosphere; (f) energizing the at least one heating element (727) to heat each initial heated portion (728, 730) of the workpiece to a hot working temperature at which the initial heated portion is plastically deformable; (g) performing a transposition operation on one or both of the first and second workpieces while the first and second heated portions are at a hot working temperature, thereby engaging the engagement surfaces (721, 720) with each other; (h) performing an engagement operation on one or both of the first and second workpieces while the first and second heated portions are at the hot working temperature, in which one or both of the first and second workpieces engaged with each other are moved relative to the other to form a first layer (764) of plastically deformable material; (i) biasing the workpieces (710, 718) together to form a second layer (766) of plastically deformable material on the bridge portions (752, 756); (j) bonding the first and second workpieces (710, 718) together by performing an engaging action on the second layer of plastically deformable material to at least partially plastically deform the second layer while the first and second workpieces are biased together; The method includes:

12. The method of claim 11 , wherein the first and second engagement portions (1750, 1754) extend across a diameter of each of the first and second workpieces (1710, 1718).

13. 1. A method comprising: (a) providing a first workpiece (810) having a first engagement surface (812) and a plurality of fins (815) extending from the first engagement surface (812); (b) providing a second workpiece (818) having a second engagement surface (820) and a plurality of fins (823) extending from the second engagement surface (820); (c) disposing the first and second workpieces at a predetermined distance from each other with the first and second exposed surfaces facing each other to form a gap between the workpieces (810, 818); (d) providing a third workpiece (870) having third and fourth engagement surfaces (872, 874) configured to mate with the first and second engagement surfaces (812, 820), respectively; (e) positioning the third workpiece (870) at a distance from the first and second workpieces (810, 818); (f) transferring heat from the first and second heated portions (828, 830) extending from each end (817, 825) of the first and second fins (815, 825) toward the first and second engagement surfaces (813, 821) to a hot working temperature at which the first and second heated portions are plastically deformable, by disposing first and second heating elements (827A, 827B) on the proximal side of the fins (815, 823) and the first and second engagement surfaces (812, 820), respectively, to a hot working temperature at which the first and second heated portions are plastically deformable, the first and second body portions being adjacent to the first and second engagement surfaces; (g) disposing at least one third heating element (827A) proximal to the third and fourth engagement surfaces (872, 874) of the third workpiece (870) to heat the third heated portion to a hot working temperature at which the third heated portion is plastically deformable; (h) covering at least said fins (815, 823) and said engagement surfaces (812, 820, 872, 874) with an inert atmosphere; (i) energizing the at least one first heating element, the at least one second heating element, and the at least one third heating element to heat the first heated portion, the second heated portion, and the third heated portion to a hot working temperature, respectively; (j) removing the heating element from the gap while the first, second and third heated portions are at the hot working temperature; (k) engaging the third heated portion with the first and second heated portions by performing a transposition operation on the third workpiece while the first, second, and third heated portions are at a hot working temperature; (l) while the first, second and third heated portions are at the hot working temperature and collectively biased, joining the third workpiece (870) to the first and second workpieces (810, 818) by performing one or more engaging operations on one or more of the first, second and third workpieces to at least partially plastically deform one or more of the first, second and third workpieces, respectively; The method includes:

14. 1. A method comprising: (a) providing a first workpiece (910) having a first engagement surface (912); (b) providing a second workpiece (918) having a second engagement surface (920) including a plurality of alternating second peaks (922) and second valleys (924); (c) positioning the first and second workpieces a predetermined distance (9D") from one another with the first and second engagement surfaces facing one another to form a gap (926) between the first and second engagement surfaces; (d) disposing at least one heating element (927) in the gap (926) for heating first and second heated portions (928, 930) located at the second peak proximate the first engagement surface (912) and the second engagement surface (920) to at least one hot working temperature at which the first and second heated portions are plastically deformable; (e) covering at least the first and second heated portions with an inert atmosphere; (f) energizing the at least one heating element to heat the first heated portion of the first work piece and the second heated portion of the second work piece to the at least one hot working temperature; (g) removing the at least one heating element from the gap when the first and second heated portions (928, 930) are at the at least one hot working temperature, and engaging the first engagement surface (912, 920) with the second peak by performing a displacement operation on one or both of the first and second workpieces; (h) bonding the first and second workpieces together by urging the first engagement surface and the second peak together to move one or both of the first and second engagement surfaces relative to the other in an engagement motion to at least partially plastically deform the first and second heated portions when the first and second heated portions are at the hot working temperature. The method includes:

15. 15. The method of claim 14, wherein the first workpiece comprises a first material having a first thermal conductivity and the second workpiece comprises a second material having a second thermal conductivity different from the first thermal conductivity.

16. The method of claim 15 , wherein the second thermal conductivity is greater than the first thermal conductivity.

17. The method of claim 14, wherein the first engagement surface defines a flat surface (929).

18. 15. The method of claim 14, wherein the second engagement surface is configured to limit transfer of thermal energy from the second heated portion to a body portion of the second workpiece adjacent the second heated portion.

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