Method and system for joining different materials

Abstract

A method of joining a first workpiece and a second workpiece, the first workpiece and the second workpiece comprising a first material and a second material. The intermediate plate is located between the first workpiece and the second workpiece with the heating element therebetween. The heating element is energized to heat a first heated portion of the first workpiece to a hot working temperature and to heat the intermediate plate to a first predetermined temperature at which the intermediate plate heats a second heated portion of the second workpiece to a second predetermined temperature. The one or both workpieces are moved in translation to engage the workpieces, and the one or both workpieces are moved in engagement to shear the first heated portion and adhere the first heated portion to the second heated portion to bond the first and second workpieces together.

Description

[0001] Cross-Reference to Related Applications

[0002] This application claims priority to U.S. Provisional Patent Application No. 63 / 572,583, filed April 1, 2024, the entire contents of which are incorporated herein by reference. TECHNICAL FIELD

[0003] The present invention relates to a method and system for joining different materials. BACKGROUND

[0004] It is well known that joining workpieces made of different materials, for example by welding or soldering, can be very difficult. For example, in the prior art, metal objects made of steel or aluminum cannot typically be soldered or welded directly to objects made of ceramic or composite materials. SUMMARY

[0005] In view of the above, there is a need for a method or system to overcome or alleviate one or more of the deficiencies or shortcomings in the prior art.

[0006] In its broadest aspect, the present invention provides a method of joining a first workpiece and a second workpiece, the first workpiece comprising a first material and the second workpiece comprising a second material. An intermediate plate is positioned between the first and second workpieces to define a first gap between the first workpiece and the intermediate plate, wherein a heating element is positioned. The heating element is energized to heat a first heated portion of the first workpiece to a hot working temperature and to heat the intermediate plate to a first predetermined temperature at which the intermediate plate heats a second heated portion of the second workpiece to a second predetermined temperature. One or both workpieces are subjected to a translational motion to bring the workpieces into engagement and one or both workpieces are subjected to an engagement motion while engaged to cause the first heated portion to be sheared and to cause the first heated portion to adhere to the second heated portion, thereby bonding the first workpiece and the second workpiece together. BRIEF DESCRIPTION OF DRAWINGS

[0007] The present invention will be better understood with reference to the following drawings, in which:

[0008] Figure 1A is a cross-sectional view of an embodiment of a first workpiece and a second workpiece and an intermediate plate, with a heating element positioned between the first workpiece and the intermediate plate;

[0009] Figure 1B is a cross-sectional view of an assembly of a first workpiece and a second workpiece of Figure 1A soldered together;

[0010] Figure 2A is a cross-sectional view of a first workpiece and a second workpiece of another embodiment and an intermediate plate, with a heating element positioned between the first workpiece and the intermediate plate; is a cross-sectional view of a first workpiece and a second workpiece of another embodiment and an intermediate plate, with a heating element positioned between the first workpiece and the intermediate plate;

[0011] Figure 2B is a cross-sectional view of an assembly of first and second workpieces welded together by Figure 2A

[0012] Figure 3 is a side view of another embodiment of a first workpiece of the present invention

[0013] Figure 3A is an end view of another embodiment of a second workpiece of the present invention

[0014] Figure 3B is a cross-sectional view of first and second workpieces of Figure 3 and 3A and an intermediate plate and heating element positioned therebetween

[0015] Figure 3C is a cross-sectional view of an assembly of first and second workpieces welded together by Figure 3 , 3A and 3B

[0016] Figure 3D is a cross-sectional view of workpieces of another embodiment and an intermediate plate and heating element positioned therebetween

[0017] Figure 3E is a cross-sectional view of an assembly of first and second workpieces welded together by Figure 3D

[0018] Figure 4A is an end view of a second workpiece of another embodiment

[0019] Figure 4B is a side view of a second workpiece of Figure 4A

[0020] Figure 4C is an isometric view of first and second workpieces of Figure 4A and 4B welded together

[0021] Figure 4D is a cross-sectional view of workpieces welded together with a retaining ring of another embodiment positioned thereon

[0022] Figure 5A is an end view of another embodiment of a second workpiece of the present invention

[0023] Figure 5B is a side view of another embodiment of an intermediate plate of the present invention

[0024] Figure 5C is an end view of another embodiment of a first workpiece

[0025] ​​​Figure 6A is a top view of another embodiment of the second workpiece of the present invention;

[0026] Figure 6B is a side view of another embodiment of the first workpiece of the present invention;

[0027] Figure 7A is a side view of another embodiment of the second workpiece and the intermediate plate and an isometric view of the first workpiece; and

[0028] Figure 7B yes Figure 7A An isometric view of a first workpiece and a second workpiece. DETAILED DESCRIPTION

[0029] In the accompanying drawings, like reference numerals designate corresponding elements throughout. Figure 1A and 1B , which describes a method of an embodiment of the present invention.

[0030] The method is for joining a first workpiece 22 and a second workpiece 26, wherein the first workpiece 22 includes a first material "M1" having a first thermal conductivity and the second workpiece 26 includes a second material "M2" having a second thermal conductivity that is less than the first thermal conductivity. In one embodiment, the method first includes positioning the first and second workpieces 22, 26 such that their respective first and second surfaces 30, 32 are spaced apart to define a primary gap 34 therebetween.

[0031] Preferably, the intermediate plate 36 is positioned within the primary gap 34 to partially define a first gap 38 and a second gap 40. The first gap 38 is defined between a first side 42 of the intermediate plate 36 and the first surface 30 ( Figure 1A ).like Figure 1A As shown, a second gap 40 is defined between a second side 44 of the intermediate plate 36 and the second surface 32. As described below, the intermediate plate preferably comprises a third material "M3" having a third thermal conductivity that is preferably equal to or greater than the first thermal conductivity.

[0032] It is understood that the first material "M1" can be any suitable metal (e.g., aluminum). The second material "M2" can also be any suitable material, such as a ceramic material or a composite material with suitable properties, such as zirconium diboride (ZrBr2). In addition, the third material "M3" is preferably any suitable material, such as aluminum, copper, steel, or titanium.

[0033] As noted above, the first material "Ml" preferably has a first thermal conductivity, where the first thermal conductivity is greater than a second thermal conductivity of the second material "M2". For example, the first material "Ml" can be aluminum or an alloy thereof, such as having a first thermal conductivity of about 150-220 W / mK or more. The second material "M2" can be a ceramic, such as zirconium diboride, which has a second thermal conductivity of about 57.9 W / mK or less.

[0034] The third material "M3" can be, for example, the same material as the first material. Alternatively, the third material can be any material having a thermal conductivity equal to or greater than the thermal conductivity of the first material. For example, the third material can be copper, which has a thermal conductivity of about 401 W / mK.

[0035] It is also preferred that the melting points of the first, second, and third materials "Ml", "M2", "M3" are compatible. For example, the melting point of the first material "Ml" is preferably no more than the melting point of the second material "M2". Further, the melting point of the third material "M3" is preferably no more than the melting point of the second material "M2".

[0036] In one embodiment, the one or more heating elements 46 are preferably located in the first gap 38. As described below, in the first gap 38, the heating elements 46 are preferably spaced a first predetermined distance 48 from the first surface 30 and a second predetermined distance 50 from the first side 42 of the intermediate plate 36.

[0037] Next, the one or more heating elements 46 are energized to heat the first heated portion 52 of the first workpiece 22 to a hot working temperature in an inert atmosphere at which the first heated portion 52 is plastically deformable. The one or more heating elements 46 also heat the intermediate plate 36 to a first predetermined temperature at which the heated intermediate plate 36 heats the second heated portion 54 of the second workpiece 26 to a second predetermined temperature in the inert atmosphere.

[0038] As shown in FIGS. 1 and 2, the first workpiece 22 includes a first heated portion 52 that is initially heated to a hot working temperature. The first heated portion 52 is a portion of the first workpiece 22 that is heated to the hot working temperature. The first heated portion 52 is preferably heated to the hot working temperature by the one or more heating elements 46. Figure 1A and 1B As shown in FIGS. 1 and 2, the first workpiece 22 includes a first heated portion 52 that is initially heated to a hot working temperature. The first heated portion 52 is a portion of the first workpiece 22 that is heated to the hot working temperature. The first heated portion 52 is preferably heated to the hot working temperature by the one or more heating elements 46.

[0039] The second workpiece 26 includes a second heated portion 54 that is initially heated to a second predetermined temperature. The second heated portion 54 is a portion of the second workpiece 26 that is heated to the second predetermined temperature. The second heated portion 54 is preferably heated to the second predetermined temperature by the heated intermediate plate 36.

[0040] Those skilled in the art will appreciate that the hot working temperature is slightly below the melting point of the first material "Ml". For example, the hot working temperature can be about 90% to 95% of the melting point of the first material "Ml". When the first material "Ml" is at the hot working temperature, the first material can be plastically deformed.

[0041] Those skilled in the art will also appreciate that when the second workpiece 26 is made of a ceramic material, such as zirconium diboride, its melting point can be very high, for example, about 3,200°C. In contrast, when the first workpiece 22 is made of aluminum, its melting point is about 660°C. The third material can be, for example, copper, which has a melting point of about 1,085°C.

[0042] As described below, the heating element 46 and the intermediate plate 36 are preferably positioned relative to the first and second workpieces 22, 26 to achieve the desired result, namely, to heat the first heating portion 52 to the hot working temperature and to heat the second heating portion 54 to the second predetermined temperature.

[0043] Those skilled in the art will appreciate a suitable inert (i.e., non-oxidizing) atmosphere. Those skilled in the art will also appreciate methods and apparatus for maintaining the inert atmosphere over, for example, the intermediate plate and the heating portions during heating. It will be appreciated that the inert atmosphere and the apparatus for maintaining the inert atmosphere in place are omitted from the drawings herein for clarity of illustration.

[0044] It will also be appreciated that the one or more heating elements 46 can be any suitable heating element. For example, the one or more heating elements 46 can be configured to heat the first heating portion 52 by induction, and also to heat the intermediate plate 36 by induction.

[0045] Those skilled in the art will also appreciate that when the second workpiece 26 is made of a ceramic material, the second heating portion 54 can be heated from the intermediate plate 36 to the second heating portion by radiation of thermal energy, or by conduction of thermal energy. In one embodiment, the second heating portion 54 can be preheated.

[0046] Once the first and second heating portions 52, 54 are at the hot working temperature and the second predetermined temperature, respectively, the intermediate plate 36 and the one or more heating elements 46 are removed from the main gap 34. Preferably, this removal is performed quickly.

[0047] In one embodiment, when the first heating portion 52 is at the hot working temperature and the second heating portion 54 is at the second predetermined temperature, one or both of the first and second workpieces 22, 26 are preferably moved in translation to bring the first and / or second workpieces together to bring the first and second surfaces 30, 32 into engagement with each other. For example, as shown in FIG. 4, the first workpiece 22 can be moved in translation relative to the second workpiece 26 to bring the first and second surfaces 30, 32 into engagement with each other. Figure 1AAs shown, the first workpiece 22 can move in the direction indicated by arrow "A", and / or the second workpiece 26 can move in the direction indicated by arrow "B", until the first and second surfaces 30, 32 engage each other Figure 1B

[0048] Next, while the first heating portion 52 is at the hot working temperature and the second heating portion 54 is at the second predetermined temperature, and while the first and second surfaces 30, 32 are engaged with each other, one or both of the first and second workpieces 22, 26 are subjected to a joining motion. As described below, when one or both of the workpieces 22, 26 are subjected to a joining motion, the workpiece or workpieces that are subjected to the joining motion move relative to the other workpiece. For example, the first workpiece 22 can move in the direction indicated by arrow "C" relative to the second workpiece 26, and / or the second workpiece 26 can move in the direction indicated by arrow "D" relative to the first workpiece 22, while the first and second surfaces 30, 32 are engaged. The joining motion can be repeated periodically, or otherwise.

[0049] As described below, in another embodiment, the joining motion can begin prior to the first and second surfaces 30, 32 engaging each other. It will be appreciated that, for clarity of illustration, Figure 1A arrows "C" and "D" are included in the center.

[0050] As described above, when the first heating portion 52 is at the hot working temperature, the first heating portion 52 is plastically deformable.

[0051] Preferably, when the workpieces 22, 26 are subjected to the joining motion, the heating portions 52 are at least partially sheared as a result of the engagement of the first and second heating portions 52, 54 during the joining motion of one or both of the workpieces 22, 26. Preferably, the first heating portion 52 at least partially adheres to the second heating portion 54 and remains adhered upon cooling.

[0052] ​It should be understood that only a very small portion (in the form of a layer) of the first and second heating portions 52, 54 are bonded together. Since only a very thin layer of the first and second heating portions 52, 54 are joined together, the resulting bond is a "surface effect" bond, i.e., does not extend beyond the heating portions more than a very shallow depth. It should be understood that the portion or layer 31 of the first heating portion 52 that is at least partially adhered to the second heating portion 54 can be very small, for example, the portion 31 can be a thin layer of only a few atoms thick at the first surface 30. It should be understood that when the workpieces 22, 26 are engaged and one or more of the workpieces are subjected to the joining motion, the small portion 31 of the first heating portion 52 intermixes with the small portion or layer 33 of the second heating portion 54, which can be only a few atoms thick at the second surface 32, thereby forming a bond between the first and second heating portions 52, 54. The mechanism that causes the workpieces 22, 26 to bond together is not fully understood. It should be understood that at the atomic level, due to the first material "Ml" being at its hot working temperature and being plastically deformable, and the second material "M2" also being at an elevated temperature, the atoms in the portion 31 are pressed into openings present in the "M2" crystal structure. However, it should also be understood that the materials "Ml", "M2" are not generally complementary at the subatomic level. In any event, the first heating portion 52 is at least partially sheared and adhered to the second heating portion 54, thereby bonding the first and second workpieces together.

[0053] When the workpieces are bonded together, the small portions 31, 33 define a very narrow bonding zone "Z" (shown in FIG. 3) through which the first and second workpieces 22, 26 are bonded together. Figure 1B

[0054] It should be understood that the width of the portions 31, 33 shown in FIG. 3 are exaggerated for clarity of illustration. Figure 1B

[0055] As can be seen from the foregoing, the bond formed across the bonding zone "Z" is mechanical in nature (at the atomic level) rather than chemical. This means that engaging more of the respective surface areas of the workpieces (e.g., when the first heating portion is at the hot working temperature and the second heating portion is at the second predetermined temperature) results in a better bond between the first and second workpieces.

[0056] Since the bonding zone "Z" is very narrow, this means that residual stresses are minimized during the inventive process. In contrast, for example, in friction welding, the workpieces are heated to their melting point to a significant depth. It is known in the art that friction welding, when heated to depth, imparts internal stresses to the workpieces being joined, and residual stresses are also created when the workpieces joined by friction welding cool.

[0057] ​​The method of the present invention generally avoids subjecting the workpieces to such residual stresses because the bond zone "Z" is very thin.

[0058] In Figure 1A In the example shown, the intermediate plate 36 is heated by one or more heating elements 46, which in turn heat the intermediate plate 36, which preferably heats the second heating portion 54 by radiation of thermal energy. It will be appreciated that the intermediate plate 36 can have any suitable shape or configuration.

[0059] As can be seen from the foregoing, the intermediate plate 36 is preferably heated only to bring the second heating portion 54 to the second predetermined temperature. It is known in the art that certain ceramic materials are poor conductors of heat, but that aluminum is a good conductor of heat. In one embodiment, the method of the present invention takes advantage of this difference in thermal conductivity, for example when the first workpiece is made of aluminum and the second workpiece is made of zirconium diboride.

[0060] Because of the difference in thermal conductivity, heat dissipates relatively quickly from the first heating portion 52 into the first body portion 53, but more slowly from the second heating portion 54 into the second body portion 55. As described above, when the first heating portion 52 is at the hot working temperature and the second heating portion 54 is at the second predetermined temperature, the first and second surfaces 30, 32 are joined, and one or both of the first and second workpieces 22, 26 are in joining motion. When the first and second surfaces 30, 32 are joined, thermal energy can be transferred from the second workpiece 26 to the first workpiece 22, or from the first workpiece 22 to the second workpiece 26, by conduction, depending on the temperature differential, if any, between them.

[0061] As can be seen from the foregoing, the joining motion occurs when the first and second surfaces 30, 32 are joined, and when the first and second heating portions 52, 54 are at the hot working temperature and the second predetermined temperature, respectively.

[0062] As will be appreciated by those skilled in the art, the joining motion can last only a very short time. It will be appreciated that soon after the respective small portions 31, 33 of the first and second heating portions are joined, sufficient heat has dissipated that the first heating portion 52 is no longer at the hot working temperature. At this point, the first and second workpieces 22, 26 are bonded together, and the joining motion ends.

[0063] Preferably, the first and third melting points of the first and third materials "Ml", "M3" are both less than the second melting point of the second material "M2". It is also preferred that the first melting point is less than the second melting point.

[0064] For example, the first, second, and third materials "Ml", "M2", and "M3" can be the following respective materials (as described above) having the following respective melting points:

[0065] Aluminum ("M1") - melting point: approximately 660 °C;

[0066] Zirconium Diboride ("M2") - melting point: approximately 3,245 °C;

[0067] Copper ("M3") - melting point: approximately 1,085 °C.

[0068] As mentioned above, the hot working temperature is preferably slightly below the melting point of the first material "M1", i.e. at which temperature the first heated portion is plastically deformable. It will be appreciated that the first and second predetermined temperatures are approximately equal to or slightly below the hot working temperature. It can thus be seen that, in this example, the first and second surfaces 30, 32 are at approximately the same temperature when the first and second workpieces 22, 26 are joined to each other. The skilled person will appreciate that it is therefore less likely that significant heat transfer will occur between the first and second workpieces.

[0069] As mentioned above, the first and second workpieces 22, 26 are preferably joined and perform a joining motion when the first and second heated portions 52, 54 are at the hot working temperature and the second predetermined temperature, respectively. The first heated portion is plastically deformed when at the hot working temperature. Preferably, the plurality of workpieces are pushed towards each other in the directions indicated by arrows "A" and "B" when the plurality of workpieces perform the joining motion, resulting in at least a portion 53 of the first heated portion 52 adhering and bonding to a portion 55 of the second heated portion 54, as mentioned above.

[0070] The skilled person will appreciate that the thermal energy in the first and second heated portions 52, 54 dissipates relatively quickly therefrom after joining.

[0071] It will be appreciated that the positions of the intermediate plate 36 and the heating element 46 relative to the first and second surfaces 30, 32 are preferably determined to maximize efficiency. Once the first and second heated portions 52, 54 are at the hot working temperature and the second predetermined temperature, respectively, and preferably when the first and second workpieces 22, 26 perform the joining motion, the workpieces 22, 26 are preferably pushed towards each other such that the surfaces 30, 32 push against each other (i.e. forge), as Figure 1A and 1B illustrated.

[0072] The skilled person will appreciate that the "hot working temperature" referred to herein is to be understood as possibly referring to a range of temperatures (i.e. not necessarily a single temperature) at which the first heated portion is plastically deformable. However, depending on the context, the "hot working temperature" can refer to a single temperature.

[0073] As Figure 1AAs shown, in one embodiment, the first and second workpieces 22, 26 preferably define respective first and second axes 24, 28. In one embodiment, the joining motion preferably includes rotation of one or both workpieces 22, 26 about their respective axes 24, 28. It is also preferred that the first and second workpieces 22, 26 are positioned coaxially.

[0074] As described above, after the heating element 46 and the intermediate plate 36 are removed from the gap 34, one or both workpieces 22, 26 can be moved toward the other workpiece in a translational motion to join the first and second workpieces 22, 26. For clarity of illustration, Figure 1A Arrow "A" indicates the direction of movement of the first workpiece 22 toward the second workpiece 26, and arrow "B" indicates the direction of movement of the second workpiece 26 toward the first workpiece 22.

[0075] In one embodiment, as Figure 1A shown, the first and second surfaces 30, 32 are preferably substantially planar. However, the first and second surfaces 30, 32 can have any suitable configuration. The surfaces 30, 32 are preferably formed to complement or mate with each other.

[0076] In another embodiment, when the first and second heating portions 52, 54 are at the hot working temperature and the second predetermined temperature, respectively (and after the heating element 46 and the intermediate plate 36 are removed from the gap 34), one or both workpieces 22, 26 preferably undergo axial oscillation while the first and second heating portions 52, 54 are joined or partially joined. In this embodiment, as opposed to rotation of one or both workpieces about their respective axes, one or both workpieces 22, 26 undergo axial oscillation while the first and second heating portions 52, 54 are joined.

[0077] For example, when the second workpiece 26 remains stationary (and when the heating portions 52, 54 are at the hot working temperature and the second predetermined temperature, respectively), the first workpiece 22 can be moved axially in the direction indicated by arrow "A" to push the first heating portion 52 against the second heating portion 54. Shortly after initial joining, the first workpiece 22 is moved in the direction indicated by arrow "Al" to briefly relieve the pressure exerted by the first heating portion 52 against the second heating portion 54. Figure 1A However, it is preferred that the first heating portion 52 does not completely disengage the second heating portion 54 as a result of the movement of the first workpiece in the direction indicated by arrow "Al".

[0078] Alternatively, the second workpiece 26 can be subjected to axial oscillation. As mentioned above, the axial oscillation is preferably performed after the first and second heating portions have been heated to the hot working temperature and the second predetermined temperature, respectively, and after the heating elements and the intermediate plate have been removed. In this embodiment, while the first workpiece 22 remains stationary (and while the heating portions 52, 54 are at the hot working temperature and the second predetermined temperature, respectively), the second workpiece 26 can be moved axially in the direction indicated by arrow "B" to push the second heating portion 54 against the first heating portion 52. Shortly after the initial engagement, the second workpiece 26 is preferably moved in the direction indicated by arrow "Bl", i.e. to briefly relieve the pressure exerted by the second heating portion 54 on the first heating portion 52. Preferably, however, the second heating portion 54 does not completely disengage from the first heating portion 52 as a result of the movement of the second workpiece 26 in the direction indicated by arrow "Bl".

[0079] In yet another embodiment, both workpieces 22, 26 can be subjected to axial oscillation.

[0080] As mentioned above, it can be seen that the shearing of the portions of the engaged first and second heating portions can be accomplished by any movement or movement of one or both workpieces relative to each other as they are engaged, e.g. by rotation of one or both workpieces about their respective axes, or axial oscillation of one or both workpieces.

[0081] Indeed, in these embodiments, the relative axial movement of one or both workpieces 22, 26, i.e. the axial oscillation, as the heating portions are engaged, causes the small portion 31 of the first heating portion 52 to mix at the atomic level with the small portion 33 of the second heating portion 54, similar to the mixing or interweaving of the materials as one or both workpieces are rotated as the first and second heating portions 52, 54 are engaged.

[0082] In the axial oscillation, different magnitudes of force can be applied throughout the process, at predetermined time intervals, pushing the workpieces together, wherein the predetermined time intervals are separated by predetermined time periods. Also, the predetermined time intervals and the predetermined time periods can vary throughout the process.

[0083] In yet another embodiment, the above-described axial oscillation can be combined with the rotation and engagement of the first and second workpieces to bond the first and second workpieces together.

[0084] As Figure 1B shown, the first and second workpieces 22, 26 are preferably fused or bonded together to form an assembly 70.

[0085] As described above, in one embodiment, the joining motion may begin when the first and second surfaces 30, 32 are joined. However, in another embodiment, one or both workpieces 22, 26 may be subjected to the joining motion before the first and second surfaces 30, 32 are joined.

[0086] For example, after the intermediate plate 36 is removed from the main gap 34 (i.e., once the first and second heated portions are at the hot working temperature and the second predetermined temperature, respectively), one or both of the first and second workpieces 22, 26 can be subjected to a joining motion, i.e., before one or both of the first and second workpieces 22, 26 are subjected to a translational motion. In this embodiment, the joining motion continues after the translational motion begins. Preferably, the joining motion continues while the first and second surfaces 30, 32 are joined, remaining constant (or substantially constant) until the first and second workpieces are bonded together.

[0087] As mentioned above, bonding metals and ceramics together is often difficult to achieve due to the different properties and characteristics of the respective materials. In another embodiment of the inventive method, Figure 2A and 2B As shown, one or more slots or grooves 160 are preferably formed in the second workpiece 126. The purpose of the grooves 160 is to provide more surface area for the first and second workpieces 122, 126 to engage, thereby promoting bonding.

[0088] like Figure 2A As shown, in one embodiment, the groove 160 is preferably partially defined by the curved outer wall 162 and the curved second surface 132 of the second workpiece 126. In one embodiment, the groove 160 is preferably at least partially defined by a generally circular concave surface to promote bonding. The groove 160 is preferably also partially defined by a ring 164 ( Figure 2B ), as will be described.

[0089] Preferably, the first and second heated portions 152, 154 of the first and second workpieces 122, 126 are heated to the hot working temperature and the second predetermined temperature, respectively, in the same manner as described above, using one or more heating elements 146 and an intermediate plate 136 positioned as shown. Figure 2A As shown. The first and second workpieces 122 and 126 can be made of suitable metals and suitable ceramics. It will be understood that, as described above, when the first heated portion 152 is at the hot working temperature, the first heated portion 152 can be plastically deformed. On the other hand, although the second heated portion 154 is heated to the second predetermined temperature, the second heated portion 154 cannot be plastically deformed.

[0090] In substantially the same manner as described above, once the first and second heating portions 152, 154 are heated to the hot working temperature and the second predetermined temperature, respectively, the intermediate plate 136 and the heating element 146 are withdrawn from between the first and second workpieces 122, 126.

[0091] Preferably, the workpieces 122, 126 are urged toward each other while the first and second heating portions 152, 154 are at the hot working temperature and the second predetermined temperature, respectively, as Figure 2A indicated by arrows "2A" and "2B". As described above, one or the other or both workpieces 122, 126 can be moved toward the other workpiece to bring the workpieces 122, 126 into engagement with each other. When the workpieces 122, 126 are urged toward each other, the first surface 130 of the first workpiece 122 initially engages the second surface 132 of the second workpiece 126.

[0092] As described above, the engagement motion can be any suitable motion, repeated periodically (at time intervals) or otherwise. It will be appreciated that in one embodiment, one or both workpieces 122, 126 can be rotated about their respective axes 124, 128 prior to engagement. As a result of the first heating portion 152 being at the hot working temperature, the first heating portion 152 is at least partially plastically deformable. The second heating portion 154 is at the second predetermined temperature. As Figure 2B indicated, upon engagement, a portion 166 of the first heating portion 152 is preferably extruded into the recess 160. As can be seen, Figure 2B the portion 166 is at least partially held in place in the recess 160 by the ring 164.

[0093] As Figure 2B indicated, the ring 164 is preferably formed and positioned to hold the plastically deformed material in the recess 160. It will be appreciated that the ring 164 is preferably moved into position in alignment with the recess 160 prior to engagement of the first and second surfaces 130, 132.

[0094] The first heated portion 152 is preferably at least partially sheared by rotating one or both workpieces about their respective axes 124, 128 while the first and second workpieces 122, 126 are engaged with one another and the first and second heated portions 152, 154 are at the hot working temperature and the second predetermined temperature, respectively. Preferably, the first heated portion 152 is at least partially adhered to the second heated portion 154 and remains fixed upon cooling. It can be appreciated that the portion 131 of the first heated portion 152 that is at least partially adhered to the portion 133 of the second heated portion 154 can be very small, for example, the portion can be a thin layer of only a few atoms thick at the first surface 130. It will be appreciated that as the workpieces 122, 126 are engaged and rotated, the small portion 131 of the first heated portion 152 mixes with the small portion 133 of the second heated portion 154, which can be only a few atoms thick at the second surface 132, thereby forming the bond between the first and second heated portions 152, 154. It can be appreciated that, Figure 2B The dimensions of the portions 131, 133 shown in FIG. 13 are exaggerated for clarity of illustration.

[0095] It can be appreciated that the workpieces 122, 126 can alternatively be bonded together using axial oscillation, as described above. In one embodiment, the first workpiece 122 can be pushed toward the second workpiece 126 (i.e., the first workpiece 122 can be pushed in the direction indicated by arrow "2A") when the first and second heated portions 152, 154 are at the hot working temperature and the second predetermined temperature, respectively (and after the heating elements and intermediate plate have been removed). After a brief engagement, the first workpiece 122 is preferably moved in the direction indicated by arrow "2A1", however, without completely disengaging the second workpiece 126. This process is preferably repeated while the first heated portion remains plastically deformable.

[0096] Alternatively, the second workpiece 126 can be pushed toward the first workpiece 122 in the direction indicated by arrow "2B" when the first and second heated portions 152, 154 are at the hot working temperature. After a brief engagement, the second workpiece 126 is preferably moved in the direction indicated by arrow "2B1" for a brief period of time without completely disengaging.

[0097] It can also be appreciated that in another embodiment, the two workpieces 122, 126 can be axially oscillated (e.g., substantially simultaneously) while the first and second heated portions 152, 154 are at the hot working temperature and the second predetermined temperature, respectively.

[0098] When the workpieces are bonded together, the small portions 131, 133 define a bond zone "2Z" (FIG. 14) across which the first and second workpieces 122, 126 are bonded together. Figure 2B

[0099] ​In yet another embodiment, the axial oscillation described above may be combined with the rotation and engagement of the first and second workpieces to bond the first and second workpieces together.

[0100] In another alternative embodiment, Figures 3-3C As shown, the first workpiece 222 preferably includes a protruding element 268 that is adapted to be inserted into one or more recesses 260 in the second workpiece 226. Preferably, the first heated portion 252 of the first workpiece 222 is heated to the hot working temperature (°C) of the metal of the first workpiece by the heating element 246 in substantially the same manner as described above. Figure 3B Preferably, the second heating portion 254 of the second workpiece 226 is heated to a second predetermined temperature by the intermediate plate 236 .

[0101] It will be appreciated that the protruding element 268 can have any suitable shape. In one embodiment, the protruding element 268 preferably has a shape complementary to the recess 260, but is configured to engage within the recess, as described below. As will be described further, when the first and second workpieces 222, 226 are engaged, the element 268 is preferably at least partially located within the recess 260. Due to the engagement of the protruding element 268 with the walls of the recess 260, the area over which the first and second workpieces 222, 226 engage one another is increased.

[0102] Once the first heating portion 252 and the second heating portion 254 are at the hot working temperature and the second predetermined temperature, respectively, and preferably when one or both of the first and second workpieces 222, 226 are rotated about their respective axes 224, 228, the first and second workpieces 222, 226 are pushed toward each other, that is, one or both of the first and second workpieces 222, 226 perform a translational motion.

[0103] When the first and second heating portions are at the hot working temperature and the second predetermined temperature, respectively, the first heating portion 252 (including the protruding element 268) is preferably partially sheared and joined, and one or both workpieces 222, 226 are rotated about their respective axes 224, 228. The recess 260 is preferably at least partially located in the second heating portion 254. Preferably, the protruding element 268 is inserted into the recess with an interference or friction fit, resulting in the protruding element 268 being sheared when the first and second heating portions 252, 254 are joined. It is also preferred that the first heating portion 252 is at least partially bonded to the second heating portion 254 and remains fixed after cooling. It can be appreciated that the portion 231 of the first heating portion 252 that is at least partially bonded to the second heating portion 254 can be very small, for example, the portion can be a thin layer of only a few atoms thick. It will be appreciated that the small portion 231 of the first heating portion 252 mixes with a small portion 233 of the second heating portion 254, which can be only a few atoms thick, when the workpieces 322, 326 are joined and rotated, thereby forming a bond between the first and second heating portions Figure 3C As a result, the first and second workpieces 222, 226 are preferably fusion bonded together to form an assembly 270 Figure 3C

[0104] It can be appreciated that the extent of the portions 231, 233 shown in FIGS. 2A-2C are exaggerated for clarity of illustration. Figure 3C It can be appreciated that the extent of the portions 231, 233 shown in FIGS. 2A-2C are exaggerated for clarity of illustration.

[0105] In another embodiment, one or both workpieces 222, 226 are preferably axially oscillated while the first and second heating portions 252, 254 are joined or partially joined when the first and second heating portions are at the hot working temperature and the second predetermined temperature, respectively. In this embodiment, as opposed to rotation of one or both workpieces about their respective axes, one or both workpieces 222, 226 are axially oscillated while the first and second heating portions 252, 254 are joined.

[0106] For example, when the second workpiece 226 remains stationary (and when the heating portions 252, 254 are at the hot working temperature and the second predetermined temperature, respectively), the first workpiece 222 can be axially moved in the direction indicated by arrow "3A" to push the first heating portion 252 against the second heating portion 254. Shortly after initial joining, the first workpiece 222 is moved in the direction indicated by arrow "3Al", i.e., axially, to briefly relieve the pressure exerted by the first heating portion 252 against the second heating portion 254. However, it is preferred that the first heating portion 252 does not completely disengage the second heating portion 254 as a result of the movement in the direction indicated by arrow "3Al". This axial joining and pressure relief can be repeated to achieve oscillation.​

[0107] Alternatively, the second workpiece 226 can be subjected to axial oscillation. The axial oscillation is preferably performed after the first and second heating portions have been heated to the hot working temperature and the second predetermined temperature, respectively, and after the heating elements and the intermediate plate have been removed. In this embodiment, while the first workpiece 222 remains stationary (and while the heating portions 252, 254 are at the hot working temperature and the second predetermined temperature, respectively), the second workpiece 226 can be moved axially in the direction indicated by arrow "3B" to push the second heating portion 254 against the first heating portion 252. Shortly after the initial engagement, the second workpiece 226 is moved, i.e., axially, in the direction indicated by arrow "3B1" to briefly relieve the pressure exerted by the second heating portion 254 on the first heating portion 252. Preferably, however, the second heating portion 254 does not completely disengage the first heating portion 252 as a result of the movement in the direction indicated by arrow "3B1". This axial engagement and pressure relief can be repeated to achieve oscillation.

[0108] In yet another embodiment, both workpieces 222, 226 can be subjected to axial oscillation, e.g., simultaneously or approximately simultaneously.

[0109] Indeed, in these embodiments, the relative axial movement of one or both workpieces 222, 226, i.e., the axial oscillation, causes the small portions 231 of the first heating portion 252 and the small portions 233 of the second heating portion 254 to intermix at the atomic level when the heating portions are engaged, similar to the mixing or interweaving of the materials when one or both workpieces are rotated while the first and second heating portions 252, 254 are engaged.

[0110] In yet another embodiment, the above-described axial oscillation can be combined with the rotation and engagement of the first and second workpieces to bond the first and second workpieces together.

[0111] It will be appreciated that, Figure 3C the extent of the portions 231, 233 shown in FIGS. 3A and 3B is exaggerated for clarity of illustration. When the workpieces are bonded together, the small portions 231, 233 define a bond zone "3Z" (FIG. 3C) Figure 3C across which the first and second workpieces 222, 226 are bonded together.

[0112] As Figure 3C indicated in FIG. 3D, the first and second workpieces 222, 226 are preferably fusion bonded or bonded together to form an assembly 270.

[0113] In another embodiment, as Figure 3D and 3EAs shown, the first workpiece 222' preferably includes one or more recesses 260', and the second workpiece 226' preferably includes one or more protruding elements 268' adapted to be inserted into the recesses 260'. Preferably, the first and second heating portions 252', 254' of the first and second workpieces 222', 226' are heated to the hot working temperature of the metal of the first workpiece and the second predetermined temperature, respectively, by the heating elements 246' and the intermediate plate 236', substantially in the same manner as described above.

[0114] In one embodiment, it is also preferred that one or both workpieces 222', 226' are rotated about their respective axes 224', 228'. Preferably, one or both workpieces 222', 226' are moved toward the other workpiece (i.e., in the direction indicated by arrows "3A2" and "3B2") so that the heating portions 252', 254' engage each other. It will be appreciated that one or both workpieces 222', 226' are preferably rotated about their respective axes 224', 228' before or after the heating portions 252', 254' engage each other. When the heating portions 252', 254' engage each other, the protruding elements 268' are preferably engaged in the recesses 260'.

[0115] Preferably, the workpieces 222', 226' are bonded together, substantially in the same manner as described above with respect to the workpieces 222, 226 being bonded together, to form the assembly 270'.

[0116] Alternatively, the workpieces 222', 226' can be bonded together, substantially in the same manner as described above with respect to the workpieces 222, 226, by using axial oscillation.

[0117] In another alternative embodiment, as Figures 4A-4C shown, the second workpiece 326 preferably includes a recess 360 formed to allow a portion of the plastically deformed first heating portion (not shown) of the first workpiece 322 to extrude outwardly, away from the central region of the second workpiece 326. Because the workpieces 322, 326 are axially aligned when engaged, the plastically deformed material can also be pushed outwardly from the central region.

[0118] It will be appreciated by those skilled in the art that when the workpieces 322, 326 are engaged, the plastically deformed material tends to, i.e., is driven or forced, radially outwardly, in the direction indicated by arrow "Q" in Figure 4A The recess 360 is formed to receive the plastically deformed material therein.

[0119] It is also preferred that a retaining ring 364 is provided to retain the plastically deformed first heating portion so that it is located between the first and second workpieces when cooled. In one embodiment, as Figure 4CAs shown, the retaining ring can be formed to include a central region 365 for receiving any excess plastic deformation material. Some of the plastic deformation material can form a bulge "R" through the central region 365.

[0120] It can be appreciated that, in Figure 4C the retaining ring 364 is shown separately from the first and second workpieces 322, 326 for illustration clarity. Further, the size of the central region 365 is exaggerated for illustration clarity. Preferably, the extent to which the plastic deformation material forms the bulge "R" is limited.

[0121] In the prior art, plastic deformation material that is deformed during a conventional friction welding process is generally unconstrained and can form a relatively large outward protrusion. The protrusion is due to the unconstrained flow of the plastic deformation material in a direction that is normal to the direction in which the workpieces are pushed toward one another during a conventional friction welding process. In these cases (i.e., bonded workpieces using a conventional friction welding process), a distinct "weld line" is generally formed between the workpieces. The weld line in the prior art is generally normal or approximately normal to the direction in which the workpieces are pushed toward one another. Those skilled in the art will appreciate that the workpieces generally cannot be securely bonded together at the weld line.

[0122] Thus, in the prior art, workpiece products that are joined by conventional friction welding tend to fail at the weld line. It should be appreciated that the retaining ring 364 pushes the plastic deformation material of the first heating portion toward the second heating portion such that a distinct weld line is not formed that marks the edge of the plastic deformation material (and is considered a weak point in conventional welding of metals to ceramics). Thus, Figures 4A-4C The bonded joint provided by the illustrated embodiment is considered stronger than a conventional weld formed using conventional methods.

[0123] In another embodiment, as Figure 4D shown, the retaining ring 364 preferably has an interior surface 367 that curves outwardly with respect to the respective exterior surfaces "SI", "S2" of the workpieces 322, 326. Because the interior surface 367 is aligned with the side surfaces "SI", "S2", when the heating portions are at the hot working temperature and are engaged, the plastic deformation material is pushed inwardly by the retaining ring 364 (as indicated by arrow "T") against itself and against the second workpiece 326. However, the interior surface 367 is preferably formed to accommodate the bulge "R" of the plastic deformation material. It should be appreciated that, therefore, when the retaining ring 364 is used, a distinct weld line is not formed, thereby promoting better bonding between the first and second workpieces 322, 326.

[0124] It should also be appreciated that the retaining ring 364 can be used in a conventional friction welding process to minimize the risk of forming a distinct weld line.

[0125] In another alternative embodiment, as shown in Fig. 48, the intermediate plate 436 preferably includes one or more protrusions 472 configured to be inserted into respective cavities 474 formed in the first and second workpieces 422, 426. Figures 5A-5C

[0126] As shown in Fig. 48, the cavities 474 can have any suitable shape. It will be appreciated that the respective protrusions 472 are formed and positioned to fit into the respective cavities 474. Figures 5A-5C Figure 5B As shown in Fig. 48, the cavities 474 can have any suitable shape. It will be appreciated that the respective protrusions 472 are formed and positioned to fit into the respective cavities 474.

[0127] The cavities 474 can have any suitable form. It will be appreciated that the various cavities 474 shown in Fig. 48 are exemplary. Figures 5A-5C

[0128] It will be appreciated that the first and second heated portions of the first and second workpieces 422, 426 (not shown) and the intermediate plate 436 are each preferably heated to the hot working temperature and the second predetermined temperature by one or more heating elements, which are omitted in Fig. 48 for clarity of illustration. Figures 5A-5C

[0129] In one embodiment, after the first and second heated portions and the intermediate plate 436 have been subjected to heating as described above, the heating elements are removed and the first and second workpieces and the intermediate plate 436 are urged toward one another, thereby inserting the protrusions 472 into the respective cavities 474.

[0130] Preferably, prior to heating, the workpieces 422, 426 and the intermediate plate 436 are positioned to align the protrusions 472 and the cavities 474. It will be appreciated that in this embodiment, the first and second workpieces 422, 426 are preferably not rotated about their respective axes. Rather, once the workpieces 422, 426 and the plate 436 have been heated to the hot working temperature, one or both of the workpieces is preferably moved axially (i.e. without rotation thereof) against the intermediate plate 436, and / or the intermediate plate 436 is moved axially against one or both of the workpieces, to position the protrusions 472 within the respective cavities 474.

[0131] Preferably, the intermediate plate 436 is heated by the heating elements (not shown) sufficiently such that the protrusions 472 are plastically deformable.

[0132] Once the protrusions 472 are inserted into the cavities 474, the first and second workpieces 422, 426 are joined with the intermediate plate 436. Preferably, the protrusions 472 form a joint with the walls 476 that define the respective cavities 474. It will be appreciated that the protrusions 472 are engaged with the walls 476 as they are pushed into the cavities 474, and thus the protrusions 472 are subjected to some degree of shearing.

[0133] As​​​​Figure 5A and 5C As shown, the first and second workpieces 422, 426 preferably include respective joining surfaces 490, 491 in which the cavities 474 are formed. Preferably, the intermediate plate 436 also includes first and second joining surfaces 492, 493 on opposite sides thereof. Figure 5B As shown, the protrusions 472 preferably extend from the first and second joining surfaces 492, 493. Figure 5B

[0134] It will be appreciated that the joining surface 490 and the first joining surface 492 are preferably substantially fully joined to one another when the protrusions 472 extending from the first joining surface 492 are fully positioned in the cavities 474 of the first workpiece 422. Similarly, the joining surface 491 and the second joining surface 493 are preferably substantially fully joined to one another when the protrusions 472 extending from the second joining surface 493 are preferably fully positioned in the cavities 474 of the second workpiece 426.

[0135] It will be appreciated by those skilled in the art that the respective joining surfaces can have any suitable complementary configuration.

[0136] In one embodiment, the protrusions 472 are preferably inserted into their respective cavities 474 with an interference or friction fit when the protrusions 472 are at the hot working temperature, with the result that the protrusions are sheared to some extent as they are inserted into their respective cavities.

[0137] It will be appreciated that the heated portions of the protrusions and the heated portions of the walls in the first workpiece are preferably at least partially plastically deformable. Preferably, the heated portions of the protrusions 472 inserted into the cavities 474 of the second workpiece 426 are at least partially adhered to the walls 476 of the cavities 474 of the second workpiece 426 and remain fixed upon cooling. Similarly, the heated portions of the protrusions inserted into the cavities of the first workpiece are at least partially adhered to the walls 476 of the cavities 474 of the first workpiece 422 and remain fixed upon cooling.

[0138] It will be appreciated that the heated portions of the protrusions 472 and the walls of the cavities 474 are mixed during the shearing process that occurs as the protrusions 472 are inserted into the cavities 474.

[0139] It will also be appreciated that the first heated portions of the first workpiece and the protrusions 474 extending from the first joining surface 492 can be heated to the hot working temperature at one time and subsequently joined, and the second heated portions of the second workpiece 426 and the protrusions extending from the second joining surface 493 can be heated at another time and subsequently joined. The second heated portions (and the protrusions 472 extending from the second joining surface 493) can be heated to a temperature different than the hot working temperature, such as a second predetermined temperature.

[0140] ​In another embodiment, some or all of the cavities 474 may be formed in the intermediate plate 436 , and some or all of the protrusions 472 may be located on one or both of the engaging surfaces 490 , 491 of the first and second workpieces.

[0141] It will be appreciated that when the protrusion 474 is inserted into the cavity 472 , one or more of the workpieces 422 , 426 and the intermediate plate 436 may be subjected to axial oscillation.

[0142] It should be understood that the relative axial movement (i.e., axial oscillation) of one or more workpieces 422, 426 and the intermediate plate causes small portions of each protrusion to intermingle or interweave with the heated portion of the workpiece while the protrusions 474 and the heated portion of the workpiece are at the hot working temperature. Upon cooling, the workpieces 422, 426 are bonded to the intermediate plate 436 therebetween.

[0143] In another alternative embodiment, Figure 6A and 6B As shown, the first workpiece 522 has protruding elements 568 thereon that are substantially adapted to be inserted into respective recesses 560 in the second workpiece 526. It will be appreciated that the first and second workpieces 522, 526 are heated by one or more heating elements (not shown) and an intermediate plate (not shown) positioned between the second workpiece 526 and the heating elements. Preferably, a first heated portion 552 of the first workpiece 522 is heated to a hot working temperature. It will be appreciated that a second heated portion (not shown) of the second workpiece 526 is also heated to a second predetermined temperature, which may be equal to the hot working temperature. Subsequently, the heating elements and intermediate plate are removed.

[0144] Preferably, the protruding element 568 is then inserted into the groove 560, and one or both of the first and second workpieces 522, 526 are moved linearly (i.e., in the direction indicated by the arrow "X"). Due to the configuration of the groove 560 and the protruding element 568, in the illustrated embodiment, the surface area of ​​engagement between the first and second workpieces 522, 526 is relatively large. The larger surface area of ​​engagement promotes adhesion between the first and second workpieces 522, 526. Preferably, the first heated portion 552 is at least partially adhered to the second heated portion and remains fixed after cooling.

[0145] In another alternative embodiment, Figure 7A and 7B As shown, the first workpiece 622 preferably has a diameter 680 that is smaller than a diameter 681 of the second workpiece 626 .

[0146] It is understood that the first heating portion 652 is heated by one or more heating elements ( Figure 7AThe first heating portion 652 is heated to a hot working temperature (not shown). Preferably, the second heating portion 654 is heated to a second predetermined temperature by the intermediate plate 636, which is positioned between the heating element and the second workpiece 626.

[0147] Next, the heating element and the intermediate plate 636 are removed from between the workpieces 622, 626, and one or both workpieces 622, 626 are rotated about their respective axes 624, 628 Figure 7B ). The first and second surfaces of the workpieces 622, 626 are brought into engagement with each other when the first and second heating portions are at the hot working temperature and the second predetermined temperature, respectively, and when the workpieces are rotated about their respective axes.

[0148] It will be appreciated by those skilled in the art that when the second workpiece 626 is at least partially made of a ceramic material, the heated workpiece can fracture or shatter at its engaged portion if the entire surface 632 is engaged with the surface of the first workpiece. It will be appreciated that this is due to the strain experienced by the second workpiece at its outer circumference, and the fact that the outer circumference of the second workpiece is not supported.

[0149] Furthermore, when the workpieces 622, 626 are rotated about their respective central axes, the surface portions near the outer circumference of the workpieces rotate faster than the portions near the respective central axes.

[0150] Accordingly, in the embodiment shown in Figure 7A and 7B the second workpiece 626 is larger, i.e. has a diameter 681 that is greater than the diameter 680 of the first workpiece 622. It will be appreciated that this arrangement makes it less likely that the surface of the second workpiece will fracture at its outer circumference. A retaining ring can be used to push the plastically deformed material inwards so that no distinct fusion line is formed.

[0151] It will be appreciated by persons skilled in the art that the present application can take many forms and that the forms shown are only exemplary. The scope of the claims should not be limited by the preferred embodiments set out in the examples, but should be given the broadest interpretation consistent with the entire description.

Claims

1. A method of joining a first workpiece and a second workpiece, 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, wherein the second thermal conductivity is less than the first thermal conductivity, the method comprising: (a) positioning a first workpiece and a second workpiece so that their respective first and second surfaces are spaced apart to define a primary gap therebetween; (b) positioning an intermediate plate in the main gap to define a first gap in which a first side of the intermediate plate is spaced a first predetermined distance from the first surface, and a second gap in which a second side of the intermediate plate is spaced from the second surface of the second workpiece, the intermediate plate comprising a third material having a third thermal conductivity that is less than or equal to the first thermal conductivity; (c) positioning at least one heating element in the first gap, the at least one heating element being spaced a first predetermined distance from the first surface and a second predetermined distance from the first side of the intermediate plate; (d) energizing the at least one heating element to heat a first heated portion of the first workpiece to a hot working temperature in the inert atmosphere at which the first heated portion is plastically deformable, and to heat the intermediate plate to a first predetermined temperature at which the heated intermediate plate heats a second heated portion of the second workpiece to a second predetermined temperature in the inert atmosphere; (e) removing the intermediate plate and the at least one heating element from the main gap; (f) causing one or both of the first and second workpieces to translate while the first heated portion is at a hot working temperature and the second heated portion is at a second predetermined temperature to engage the first and second surfaces with each other; as well as (g) while the first heated portion is at the hot working temperature and the second heated portion is at the second predetermined temperature, and while the first surface and the second surface are engaged, subjecting one or both of the first and second workpieces to an engaging motion, wherein one or both of the first and second workpieces are moved relative to one another to at least partially shear the first heated portion and adhere the first heated portion to the second heated portion, thereby bonding the first and second workpieces together.

2. The method according to claim 1, wherein: The first, second, and third materials have respective first, second, and third melting points; The first and third melting points are both less than the second melting point; and The first melting point is lower than the second melting point.

3. The method according to claim 1, wherein: The first workpiece defines a first axis thereof; The second workpiece defines a second axis thereof; and The joining motion includes rotation of one or both of the first and second workpieces about their respective axes.

4. The method according to claim 3, characterized in that The first and second workpieces are coaxially positioned.

5. The method according to claim 1, wherein: The first workpiece defines a first axis thereof; The second workpiece defines a second axis thereof; and The joining motion includes oscillation of one or both of the first and second workpieces in an axial direction parallel to the first and second axes.

6. The method according to claim 1, characterized in that The at least one heating element heats the first heating portion by induction.

7. The method according to claim 1, characterized in that The at least one heating element heats the intermediate plate by induction.

8. The method according to claim 1, characterized in that The second heating portion is heated to a second predetermined temperature by radiation of heat energy from the intermediate plate.

9. The method according to claim 1, characterized in that The intermediate plate includes an intermediate plate material having a third thermal conductivity that is equal to or greater than the second thermal conductivity.

10. A method of joining a first workpiece and a second workpiece, 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, the second thermal conductivity being less than the first thermal conductivity, the method comprising: (a) positioning first and second workpieces so that their respective first and second surfaces are spaced apart to define a primary gap therebetween; (b) positioning an intermediate plate in the main gap to define a first gap in which a first side of the intermediate plate is spaced a first predetermined distance from the first surface, and a second gap in which a second side of the intermediate plate is spaced from the second surface of the second workpiece, the intermediate plate comprising a third material having a third thermal conductivity that is less than or equal to the first thermal conductivity; (c) positioning at least one heating element in the first gap, the at least one heating element being spaced a first predetermined distance from the first surface and a second predetermined distance from the first side of the intermediate plate; (d) energizing the at least one heating element to heat a first heated portion of the first workpiece to a first hot working temperature in the inert atmosphere at which the first heated portion is plastically deformable, and to heat the intermediate plate to a first predetermined temperature at which the heated intermediate plate heats a second heated portion of the second workpiece to a second predetermined temperature in the inert atmosphere; (e) removing the intermediate plate and the at least one heating element from the main gap; (f) causing one or both of the first and second workpieces to perform a joining motion in which one or both of the first and second workpieces moves relative to one another while the first and second heating portions are at the hot working temperature and the second predetermined temperature, respectively; (g) causing one or both of the first and second workpieces to translate while the first and second heating portions are at the hot working temperature and the second predetermined temperature, respectively, to engage the first and second surfaces with each other; as well as (h) while the first heated portion and the second heated portion are at the hot working temperature and the second predetermined temperature, respectively, and while the first and second surfaces are engaged, causing one or both of the first and second workpieces to perform an engaging movement to at least partially shear the first heated portion and adhere the first heated portion to the second heated portion, thereby bonding the first and second workpieces together.

11. The method according to claim 10, characterized in that: The first, second, and third materials have respective first, second, and third melting points; The first and third melting points are both less than the second melting point; and The first melting point is lower than the second melting point.

12. The method according to claim 10, wherein: The first workpiece defines a first axis thereof; The second workpiece defines a second axis thereof; and The joining motion includes rotation of one or both of the first and second workpieces about their axes.

13. The method according to claim 12, characterized in that The first workpiece and the second workpiece are coaxially positioned.

14. The method according to claim 10, wherein: The first workpiece defines a first axis thereof; The second workpiece defines a second axis thereof; and The joining motion includes oscillation of one or both of the first and second workpieces in an axial direction parallel to the first and second axes.

15. The method according to claim 10, characterized in that The at least one heating element heats the first heating portion by induction.

16. The method according to claim 10, characterized in that The at least one heating element heats the intermediate plate by induction.

17. The method according to claim 10, wherein: The intermediate plate heats the second heating portion by radiation.

18. The method according to claim 10, wherein: The intermediate plate includes an intermediate plate material having a third thermal conductivity that is equal to or greater than the second thermal conductivity.

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