Metalworking methods

Abstract

This invention provides a method for processing aluminum alloys that achieves high strength while also enabling cold working. [Solution] The method comprises a solid solution step in which a rod-shaped metal body made of A7075 is subjected to strong strain at 475°C and then rapidly cooled; a first aging treatment step in which it is held at 120°C for 6 hours; a cold working step in which it is plastically deformed at room temperature; and a second aging treatment step in which it is held at 120°C for 12 hours.

Description

Technical Field

[0001] The present invention relates to a method for processing a metal body. More specifically, it relates to a method for processing an aluminum alloy that can achieve high strength and is plastically processable in the cold state.

Background Art

[0002] 7000 series aluminum alloys (for example, A7075 alloy, etc.) are used for aircraft structural members due to their characteristics of high strength and light weight. And in recent years when reduction of CO2 emissions is required, further high-strengthening of aluminum alloys is demanded for miniaturization and weight reduction of aircraft structural members.

[0003] Note that the demand for high-strengthening is not limited to the 7000 series, and the same applies to 6000 series and 2000 series aluminum alloys.

[0004] By the way, in order to significantly improve properties such as strength through grain refinement treatment of metal materials, many grain refinement processes using large strains have been developed and proposed. The inventor of the present invention has also proposed a method for realizing strength improvement of an aluminum alloy by refining the metal structure of the aluminum alloy (see Patent Document 1).

[0005] The technique described in Patent Document 1 is to "form a low deformation resistance region in which the deformation resistance of a metal body (aluminum alloy) is locally reduced, and shear deform this low deformation resistance region to refine the metal structure of the metal body".

[0006] Here, although a certain degree of high-strengthening can be achieved by the processing method described in Patent Document 1, in view of the fact that further high-strengthening is demanded, the inventor of the present invention has proposed the technique described in Patent Document 2.

[0007] The technique described in Patent Document 2 involves "applying strain to a metal body (aluminum alloy) in the low-temperature solution treatment temperature range to break up crystals and precipitates, then cooling it, and subsequently heating it to the solution treatment temperature range and rapidly cooling it." [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] International Publication No. 2004 / 028718 [Patent Document 2] Japanese Patent Publication No. 2024-16738 [Overview of the project] [Problems that the invention aims to solve]

[0009] While the processing method described in Patent Document 2 above can achieve supersaturated solid solution of elements and increase the strength of the metal body (aluminum alloy), it is necessary to perform various plastic deformation processes (extrusion, rolling, forging, etc.) within the solid solution treatment temperature range (450-515°C for the 7000 series, 500-590°C for the 6000 series, and 490-530°C for the 2000 series), which forces work at a hot temperature. Therefore, there is a need for a processing method that allows plastic deformation at a cold temperature.

[0010] This invention was conceived in view of the above points, and aims to provide a method for processing metal bodies that achieves high strength and enables plastic deformation at cold temperatures. [Means for solving the problem]

[0011] To achieve the above objective, the present invention provides a method for processing a metal body, comprising: a solution treatment step in which a metal body made of a heat-treatable aluminum alloy is heated to a solution treatment temperature range, a predetermined strain is applied, and then it is cooled at a rate that does not cause the dissolved elements to precipitate, thereby supersaturating the elements in the matrix of the metal body and refining the crystal grains of the metal body; a first aging treatment step in which an aging treatment is performed after the solution treatment step to precipitate precipitates at the crystal grain boundaries of the metal body; a plastic deformation step in which the metal body is plastically deformed in a cold temperature range after the first aging treatment step to give the metal body a predetermined shape and apply strain to the crystal grains of the metal body; and a second aging treatment step in which an aging treatment is performed after the plastic deformation step to precipitate precipitates in the crystal grains of the metal body, wherein the first aging treatment step starts cooling before all of the precipitates that would precipitate by continuing the aging treatment have precipitated.

[0012] In this process, heating to the solution treatment temperature range allows elements to be dissolved into the matrix, resulting in increased strength due to supersaturated solid solution of elements.

[0013] In this context, the "solid solution treatment temperature range" refers to the temperature range in which elements can be dissolved (solid-solved) into the matrix. This range depends on the material of the aluminum alloy in question, but is 450-515°C for the 7000 series, 500-590°C for the 6000 series, and 490-530°C for the 2000 series.

[0014] Furthermore, in the solution formation process, high strength is achieved by cooling at a rate that prevents the dissolved elements from precipitation, thereby supersaturating the elements in the metal matrix and refining the crystal grains of the metal. In other words, if the cooling rate is too slow, the dissolved elements will partially precipitate in the matrix, leading to problems such as coarsening and a decrease in strength. Therefore, it is necessary to cool at a rate that prevents the dissolved elements from precipitation (in other words, a rate at which the dissolved elements cannot diffuse).

[0015] Similarly, to prevent partial precipitation of elements dissolved in the matrix, which can lead to problems such as coarsening and a decrease in strength, cooling during the solution formation process must be started before the dissolved elements precipitate.

[0016] Incidentally, by applying a predetermined strain within the solution treatment temperature range, the interatomic distance of the aluminum alloy can be increased, raising the solid solution limit. Therefore, if the temperature range is appropriate (a temperature range in which the energy necessary for atomic diffusion contributing to solid solution can be obtained), even greater supersaturation of the solid solution becomes possible, resulting in even higher strength. One example is applying a strain of 400% or more.

[0017] Furthermore, when strain is applied in the solution treatment temperature range by shear deformation, strain can be applied with high efficiency, and a more sufficient supersaturated solid solution can be achieved.

[0018] Specifically, in the solution treatment process, when strain is applied to a metal body by shearing it through a twisting motion, where the metal body is rotated around an axis approximately parallel to its longitudinal direction, strain can be applied with high efficiency.

[0019] Furthermore, if the solution treatment process involves heating the metal body to the solution treatment temperature range, thereby locally reducing the deformation resistance of the metal body and forming a low deformation resistance region, and then shear-deforming this low deformation resistance region to dissolve a predetermined element into the metal body, then supersaturated solid solution of the element into the locally formed low deformation resistance region can be achieved very easily.

[0020] Furthermore, when the low deformation resistance region is moved along the longitudinal direction of the rod-shaped metal body, supersaturated solid solution of elements into the entire metal body (rod-shaped body) can be achieved very easily.

[0021] Another method for applying strain in the solution treatment process is to deform the metal body (plate-like body) by rolling with rolling rolls.

[0022] Also, by performing aging treatment, in the first aging treatment step of precipitating precipitates at the grain boundaries of the metal body, precipitates will precipitate (preferably precipitate) at the grain boundaries of the crystal structure refined in the solution treatment step.

[0023] Furthermore, when the first aging treatment step here is "to start cooling before all the precipitates that precipitate by continuing the aging treatment have precipitated", precipitates can also be precipitated in the subsequent aging treatment (second aging treatment step).

[0024] Examples of the "aging treatment that starts cooling before all the precipitates that precipitate by continuing the aging treatment have precipitated" include "aging treatment that starts cooling when precipitates have precipitated at the grain boundaries of the metal body", "aging treatment that starts cooling when precipitates capable of stress propagation have precipitated at the grain boundaries of the metal body", or "aging treatment that starts cooling in a time of 1 / 2 or less of the aging treatment time specified by JIS", etc.

[0025] Also, as an example of the first aging treatment step, "when the metal body is of the 7000 series, aging treatment that starts cooling at 100 to 125°C with a holding time of 12 hours or less", "when the metal body is of the 6000 series, aging treatment that starts cooling at 155 to 180°C with a holding time of 4 hours or less", or "when the metal body is of the 2000 series, aging treatment that starts cooling at 180 to 200°C with a holding time of 4 hours or less", etc. can be mentioned.

[0026] Furthermore, by performing plastic working of the metal body in the cold temperature range, while shaping the metal body into a predetermined shape, in the plastic working step of imparting strain into the crystal grains of the metal body, strain (dislocation) is imparted into the crystal grains refined in the solution treatment step, and a desired product shape can be obtained.

[0027] In the metal body processing method of the present invention, the crystal grains of the metal body are refined in the solution treatment step, and precipitates are preferentially precipitated at the grain boundaries of the refined crystal structure in the first aging treatment step. As a result, the stress applied by cold working can be sequentially propagated throughout the entire metal body (i.e., the strain applied by cold working can be uniformly distributed to each crystal grain), and a large strain (for example, a strain of 60% or more) can be applied to the entire metal body. In other words, in the metal body processing method of the present invention, "refinement" and "solution treatment" are achieved simultaneously in the solution treatment step, and in the first aging treatment step, the dissolved solid solution components are preferentially precipitated at the grain boundaries of the refined crystal structure. As a result, even if plastic deformation (for example, forging) is performed at a cold temperature of 200°C or lower (for example, at room temperature) that imparts a strain of 60% or more, cracks are less likely to occur.

[0028] Furthermore, a second aging treatment is performed after the plastic deformation process to precipitate precipitates within the crystal grains of the metal body. This second aging treatment causes fine precipitates to precipitate on the strains (dislocations) within the crystal grains that were introduced during the plastic deformation process (the locations where dislocations were introduced within the crystal grains have high energy, and precipitates precipitate at these high-energy locations).

[0029] Examples of the second aging treatment process include: "If the metal body is of the 7000 series, aging treatment at 100-125°C for about 24 hours"; "If the metal body is of the 6000 series, aging treatment at 155-180°C for about 8 hours"; or "If the metal body is of the 2000 series, aging treatment at 180-200°C for about 8 hours."

[0030] In the metal body processing method of the present invention, strain (dislocations) is introduced into the crystal grains in the plastic deformation step, and precipitates precipitate on the strain (dislocations) in the crystal grains in the second aging treatment step, thereby obtaining a crystalline structure in which a large number of precipitates are dispersed.

[0031] In contrast, when aging treatment is performed without introducing strain (dislocations) into the crystal grains (for example, when cooling is performed after all precipitates have precipitated in the first aging treatment step), precipitates do precipitate within the crystal grains, but because no strain (dislocations) is introduced into the crystal grains, it is not possible to disperse a large number of precipitates (the precipitates precipitate in a coarse state). [Effects of the Invention]

[0032] The present invention provides a metal body processing method that can obtain a fine crystalline structure with numerous precipitates dispersed, thereby achieving high strength and enabling cold plastic deformation. [Brief explanation of the drawing]

[0033] [Figure 1] This is a schematic diagram illustrating the processing method for aluminum alloys. [Figure 2] This is a schematic diagram to explain strain application. [Figure 3] This is a schematic diagram illustrating the crystalline structure of an aluminum alloy. [Figure 4] This is a schematic diagram illustrating the strain application in the modified example. [Figure 5] This is a schematic diagram illustrating a modified method for processing aluminum alloys. [Modes for carrying out the invention]

[0034] The following describes embodiments for carrying out the invention (hereinafter referred to as "embodiments").

[0035] <Embodiment> Figure 1 is a schematic diagram illustrating an example of a metal body processing method according to the present invention, specifically a method for processing an aluminum alloy. Figure 3 is a schematic diagram illustrating the microstructure of an aluminum alloy.

[0036] In this embodiment, the explanation will be given using the case where a rod-shaped aluminum alloy (metal body) is used as an example. Specifically, commercially available material A7075 is used, which contains, by weight percent, Si: 0.14%, Fe: 0.14%, Cu: 1.7%, Mn: 0.05%, Mg: 2.7%, Cr: 0.2%, Zn: 5.7%, and Ti: 0.01%, with the remainder being Al and unavoidable impurities.

[0037] [Solution process] In the aluminum alloy processing method according to this embodiment, first, the metal body is heated to 475°C (see reference numeral S1 in Figure 1), severe strain (strain of 400% or more) is applied (see reference numeral S2 in Figure 1), and 10 seconds after applying the severe strain, it is rapidly cooled to room temperature at a rate of 30°C / second (see reference numeral S3 in Figure 1).

[0038] Specifically, as shown in Figure 2(a), the metal body 1 is inserted into the interior of the high-frequency heating coil 3 in a non-contact manner, and the metal body 1 is inductively heated to 475°C to form a low deformation resistance region 2 in which the deformation resistance is locally reduced.

[0039] Furthermore, a rotary motor (not shown) is connected to the front end of the metal body 1 in the drawing. This rotary motor twists the region of the metal body 1 on the rotary motor side, using an axis parallel to the longitudinal direction of the metal body 1 as the axis of rotation, as indicated by the symbol A in Figure 2(a). This twisting motion causes shear deformation of the metal body 1, thereby applying a strong strain.

[0040] Specifically, using the apparatus shown in Figure 2(a), a strong strain is applied at a processing temperature of approximately 475°C (748K), a sample feed rate of 600 mm / min, and a rotation rate of 50 rpm (equivalent to a strain of 1000% or more).

[0041] Furthermore, annular cooling units 4 are positioned on both sides of the high-frequency heating coil 3, which discharge water supplied from water supply pipes (not shown). The water discharged from the cooling units 4 rapidly cools the metal body 1.

[0042] This solution treatment process makes it possible to maintain the refined structure through rapid cooling, resulting in a structure in metal body 1 with refined crystal grains compared to before processing (see Figure 3(a)) (see Figure 3(b)).

[0043] As an example of an apparatus used in the solution formation process, the apparatus described in Patent Document 1 (International Publication No. 2004 / 028718) (Figure 10) can be cited.

[0044] In this embodiment, the explanation uses the case of heating to 475°C as an example, but it is sufficient to heat to the solid solution treatment temperature range (450-515°C in the case of A7075), and it is not necessarily required to be 475°C.

[0045] Furthermore, in this embodiment, the explanation is given using as an example the case in which strain is applied by a twisting motion in which the metal body 1 is rotated around an axis parallel to its longitudinal direction. However, it is sufficient if strain can be applied, and twisting is not necessarily required.

[0046] For example, instead of the twisting motion indicated by the symbol A in Figure 2(a), strain may be applied by applying a predetermined vibration to cause shear deformation of the metal body 1. As an example of a device that applies strain by vibration, the device described in Patent Document 1 (International Publication No. 2004 / 028718) (Figure 9) can be cited.

[0047] Alternatively, instead of the twisting motion indicated by the symbol A in Figure 2(a), the metal body 1 may be gripped at the front end of the metal body 1 (the gripping device configuration is not shown), as shown in Figure 2(b), and then pulled along the longitudinal direction of the metal body 1 as indicated by the symbol B in Figure 2(b). This pulling motion may then apply strain to the metal body 1.

[0048] However, considering the need to apply strain with high efficiency, it is preferable to apply strain by shearing the metal body 1. In other words, rather than applying strain by tensile motion as shown in Figure 2(b), it is preferable to (1) apply strain by twisting motion as shown in Figure 2(a), or (2) apply strain by vibration using the apparatus shown in Figure 9 of Patent Document 1 (International Publication No. 2004 / 028718).

[0049] Furthermore, in this embodiment, rapid cooling is started 10 seconds after applying a strong strain, but it is sufficient to start rapid cooling before the elements dissolved in the matrix precipitate, and it is not necessarily limited to 10 seconds.

[0050] Furthermore, in this embodiment, the example of rapid cooling from 475°C to room temperature at a rate of 30°C / second is used for explanation. However, it is sufficient to rapidly cool to a temperature range (low temperature range) where the dissolved elements do not precipitate, at a rate where the dissolved elements do not precipitate, and it is not necessarily required to rapidly cool from 475°C to room temperature at a rate of 30°C / second.

[0051] [Statute of Limitations Processing (1st time)] In the aluminum alloy processing method according to this embodiment, the alloy is then heated to 120°C (see reference numeral S4 in Figure 1) before spontaneous aging (room temperature aging) occurs, held for approximately 6 hours (see reference numeral S5 in Figure 1), and then air-cooled to room temperature (see reference numeral S6 in Figure 1) to precipitate the elements dissolved in the matrix at the grain boundaries.

[0052] Because this aging process (first time) has a shorter holding time compared to normal aging (in the case of A7075, the standard holding time is 12 to 18 hours, while the holding time in this embodiment is about 6 hours), precipitate X precipitates only at the grain boundaries of the refined crystal grains (see Figure 3(c)).

[0053] In the aging process, precipitates form starting from areas with higher energy. Therefore, precipitates first form at the grain boundaries, and then within the grains themselves. Furthermore, in this embodiment, because the holding time is short, there is insufficient time for precipitates to precipitate within the crystal grains, and precipitate X precipitates only at the grain boundaries of the crystal grains where preferential precipitation occurs (preferential precipitation).

[0054] Furthermore, if sufficient holding time is ensured during the aging process (for example, 12 to 18 hours), precipitates will form "within the crystal grains." However, in this embodiment, because the holding time is short, no precipitates form "within the crystal grains."

[0055] [Cold working process] In the aluminum alloy processing method according to this embodiment, the aluminum alloy (metal body 1), which is in the form of a rod, is then subjected to plastic deformation (cold working) such as forging at room temperature to obtain the desired product shape (see reference numeral S7 in Figure 1).

[0056] Here, the crystal grains are refined by the solution treatment process, and precipitates are deposited at the grain boundaries of the refined crystal grains by the aging treatment process (first time). Therefore, the strain (dislocation) Y applied by cold working can be uniformly dispersed in each crystal grain (see Figure 3(d)). In other words, cold working can produce a structure in which strain is dispersed "within the crystal grains". [Statute of Limitations Treatment Process (2nd time)] In the aluminum alloy processing method according to this embodiment, the material is then heated to 120°C (see reference numeral S8 in Figure 1), held for 12 to 18 hours (see reference numeral S9 in Figure 1), and then air-cooled to room temperature (see reference numeral S10 in Figure 1) to precipitate the elements dissolved in the matrix onto the strains (dislocations).

[0057] As described above, during aging treatment, precipitates precipitate from areas with high energy. Since areas where strain (dislocations) are applied have high energy, precipitate Z precipitates on top of the strain (dislocations) within the crystal grains (see Figure 3(e)).

[0058] [effect] The metal processing method to which the present invention is applied makes it possible to obtain a crystalline structure in which numerous precipitates are dispersed, thereby achieving high strength in aluminum alloys. In other words, the cold working process can impart dispersed strain (dislocations) within the crystal grains, and the aging process (second time) can precipitate precipitate Z on top of the strain (dislocations) within the crystal grains, thereby improving the mechanical properties (increasing strength) of the aluminum alloy.

[0059] For example, if a standard solution heat treatment (a process in which the material is heated to the solution treatment temperature range to induce solid solution) is followed by aging treatment (a standard aging treatment with sufficient holding time), the strength will be 570 N / mm². 2 To that extent, if a heat treatment that imparts strain during solution heat treatment (a treatment that heats up to the solution treatment temperature range and imparts strain to induce solid solution) is followed by aging treatment (a normal aging treatment with sufficient holding time), the strength will be 600 N / mm². 2 In contrast to the above, the aluminum alloy obtained by the metal processing method to which the present invention is applied has a strength of 700 N / mm². 2 This allows for the acquisition of strength (equivalent to that of an aluminum alloy obtained by the processing method described in Patent Document 2).

[0060] Furthermore, the metal processing method to which the present invention is applied also achieves increased hardness of aluminum alloys. Table 1 shows the hardness at forging temperatures (temperatures used when forging the material) of room temperature (RT), 100°C, and 150°C.

[0061] [Table 1]

[0062] Table 1 shows that the aluminum alloy obtained by the metal processing method to which the present invention is applied has a hardness of 205 MPa when the forging temperature is room temperature (RT), a hardness of 193 MPa when the forging temperature is 100°C, and a hardness of 182 MPa when the forging temperature is 150°C. Table 1 shows that the lower the forging temperature, the greater the increase in hardness.

[0063] Furthermore, the metal body processing method to which the present invention is applied allows for processing at room temperature (cold working), eliminating the need for heating and cooling time compared to hot working, thereby improving work efficiency. In addition, compared to hot working, heating and cooling equipment can be eliminated, resulting in cost reduction.

[0064] Furthermore, while the technology described in Patent Document 2 involves two heating and cooling steps (a low-temperature solution fusion step and a high-temperature solution fusion step), the metal body processing method to which the present invention is applied requires only one heating and cooling step (a solution fusion step), and it is possible to obtain a strength comparable to that of the aluminum alloy obtained by the processing method described in Patent Document 2. Compared to the technology described in Patent Document 2, this method improves work efficiency and reduces costs.

[0065] Furthermore, since natural aging hardly occurs after the first aging treatment, the material can remain in the aged state. Even if there is a gap between the aging treatment and cold working, the mechanical properties are less likely to be affected, and the process is not difficult to implement, making it a highly practical process.

[0066] <Variation> [Example 1] In the embodiments described above, the example of twisting a rod-shaped aluminum alloy (metal body) is used for explanation, but the solution treatment process is not necessarily limited to this form. For example, as shown in Figure 4, the aluminum alloy 10 (metal body), which is in the form of a plate, may be heated to the solution treatment temperature range (450-515°C in the case of A7075), rolled with water-cooled rolling rolls 11, and then water-cooled (rapidly cooled) with cooling water discharged from a cooling nozzle 12 to refine the crystal grains. In this case, rolling is performed during the cold working process after the aging treatment (first time) to obtain the desired product shape.

[0067] [Differentiation 2] In the embodiments described above, the explanation is given using the case of only one heating and cooling step as an example, but a low-temperature solid solution step may be performed as a step before the solid solution step (two heating and cooling steps may be performed). The following provides a detailed explanation of the second variation.

[0068] [Low temperature solid solution process] In the low-temperature solution fusion process, first, the metal body is heated to 370°C (see symbol T1 in Figure 5), a strong strain (400% strain) is applied (see symbol T2 in Figure 5), and 5 seconds after the strong strain is applied, it is rapidly cooled to room temperature at a rate of 30°C / second (see symbol T3 in Figure 5).

[0069] In the low-temperature solution treatment process, strain is applied in the low-temperature solution treatment temperature range (i.e., the temperature range in which the deformation resistance of the matrix is ​​not too low) (i.e., a mechanical load is applied to the precipitates and crystals), which allows the aggregated precipitates and crystals to be broken down (decomposed), dispersing the added elements and making them easier to dissolve into the matrix (easier to solid-solve), and high strength is achieved through supersaturated solid solution of the elements. The precipitates and crystals mentioned here include MgZn2, Mg2Si, Al6Fe, Al3Fe, and Al 17 Examples include Cu2Fe.

[0070] Furthermore, even if some or all of the fragmented crystals or precipitates remain without solid dissolution in the low-temperature solution process, they will still be dissolved in the subsequent solution process. In other words, in the low-temperature solution process, it is sufficient to fragment (decompose) the aggregated crystals or precipitates, and even if fragmented (decomposed) crystals or precipitates remain, they can be dissolved in the solution process, achieving supersaturated solid solution of elements.

[0071] Furthermore, the "low-temperature solution treatment temperature" in this context refers to the temperature range in which crystals and precipitates can be separated without causing cracks (fractures) in the matrix by applying strain to the metal body.

[0072] Furthermore, when strain is applied in the low-temperature solution treatment temperature range by shear deformation, strain can be applied with high efficiency, and precipitates and other precipitates can be decomposed even more thoroughly.

[0073] In this case, if the temperature is lower than the low-temperature solution treatment temperature range (i.e., if the temperature is too low), although the crystals and precipitates can be decomposed, the matrix lacks sufficient ductility, causing stress to concentrate near the crystals and precipitates, resulting in cracks (fractures) in the matrix. On the other hand, if the temperature is higher than the low-temperature solution treatment temperature range (i.e., if the temperature is too high), the deformation resistance of the matrix is ​​too low, making it impossible to fragment the crystals and precipitates.

[0074] The "low-temperature solution treatment temperature range" depends on the material of the aluminum alloy being treated, but it is 315-420°C for the 7000 series, 320-420°C for the 6000 series, and 280-380°C for the 2000 series.

[0075] In the low-temperature solution treatment process, specifically as shown in Figure 2(a), the metal body 1 is inserted into the interior of the high-frequency heating coil 3 in a non-contact manner, and the metal body 1 is inductively heated to 370°C to form a low deformation resistance region 2 in which the deformation resistance is locally reduced.

[0076] Furthermore, similar to the solution treatment process described above, the region of the metal body 1 on the rotating motor side is twisted using an axis parallel to the longitudinal direction of the metal body 1 as the axis of rotation, as indicated by the symbol A in Figure 2(a). This twisting motion causes shear deformation of the metal body 1, thereby applying a strong strain.

[0077] Furthermore, similar to the solution treatment process described above, the metal body 1 is rapidly cooled by water discharged from the cooling unit 4.

[0078] In modification 2, rapid cooling is started 5 seconds after applying a strong strain, but it is sufficient to start rapid cooling before the elements dissolved in the matrix precipitate, and it is not necessarily limited to 5 seconds.

[0079] Furthermore, while the second modification uses the example of rapid cooling from 370°C to room temperature at a rate of 30°C / second, it is sufficient to rapidly cool to a temperature range (low temperature range) where the dissolved elements do not precipitate, at a rate where the dissolved elements do not precipitate. It is not necessarily required to rapidly cool from 370°C to room temperature at a rate of 30°C / second.

[0080] The subsequent steps, "Solid solution treatment (symbols S1-S3 in Figure 5)", "First aging treatment (symbols S4-S6 in Figure 5)", "Cold working treatment (symbol S7 in Figure 5)", and "Second aging treatment (symbols S8-S10 in Figure 5)", are the same as in the embodiment described above.

[0081] In the processing method of Modification 2, supersaturated solid solution of elements is achieved, resulting in increased strength of the aluminum alloy. In other words, the low-temperature solution fusion process can break down precipitates and disperse the added elements, and the dispersed added elements can be sufficiently dissolved in the low-temperature solution fusion process and the solution fusion process, thereby improving the mechanical properties (increasing strength) of the aluminum alloy.

[0082] Furthermore, since virtually no natural aging occurs after the low-temperature solution treatment, aging treatment after the low-temperature solution treatment is unnecessary, and the material can remain in a state rapidly cooled from the low-temperature solution treatment temperature range (370°C in modified example 2). [Explanation of Symbols]

[0083] 1 metal body 2. Low deformation resistance region 3. High-frequency coil 4 Cooling Unit

Claims

1. A solution treatment step involves heating a metal body made of a heat-treatable aluminum alloy to a solution treatment temperature range, applying a predetermined strain, and then cooling it at a rate that prevents the precipitated elements from precipitation, thereby supersaturating the elements in the matrix of the metal body and refining the crystal grains of the metal body. A first aging treatment step is performed after the solid solution treatment step to precipitate precipitates at the grain boundaries of the metal body by performing an aging treatment, Following the first aging treatment step, a plastic deformation step is performed on the metal body in a cold temperature range to give the metal body a predetermined shape and to impart strain to the crystal grains of the metal body. The process includes a second aging treatment step, which involves performing an aging treatment after the plastic deformation step to precipitate precipitates within the crystal grains of the metal body, The first aging treatment step is, By continuing the aging treatment, cooling should be started before all of the precipitates have precipitated. A method for processing metal bodies.

2. The first aging treatment step is, Cooling is started when precipitates have formed at the grain boundaries of the metal body. The method for processing a metal body according to claim 1.

3. The first aging treatment step is, Cooling is initiated when a precipitate capable of transmitting stress has precipitated at the grain boundaries of the metal body. The method for processing a metal body according to claim 2.

4. The first aging treatment step is, Cooling should be initiated at a time of less than half the aging treatment time specified in JIS standards. The method for processing a metal body according to claim 1.

5. The aforementioned metal body is of the 7000 series, The first aging treatment step is, That temperature range is 100 to 125°C. The retention period is 12 hours or less. The method for processing a metal body according to claim 1.

6. The aforementioned metal body is of the 6000 series, The first aging treatment step is, That temperature range is 155 to 180°C. The holding time is 4 hours or less. The method for processing a metal body according to claim 1.

7. The aforementioned metal body is of the 2000 series, The first aging treatment step is, That temperature range is 180-200°C. The holding time is 4 hours or less. The method for processing a metal body according to claim 1.

8. The aforementioned metal body is a rod-shaped body, The solution treatment process involves a twisting motion in which the metal body is rotated around an axis substantially parallel to the longitudinal direction of the metal body, thereby shearing and deforming the metal body and applying a strain of 400% or more. A method for processing a metal body according to claim 1, claim 2, claim 3, or claim 4.

9. The aforementioned metal body is a plate-shaped body, The solution treatment process involves deforming the metal body by a rolling operation using rolling rolls to impart a strain of 400% or more. A method for processing a metal body according to claim 1, claim 2, claim 3, or claim 4.

10. The aforementioned plastic deformation process involves applying a strain of 60% or more at a temperature of 200°C or below. A method for processing a metal body according to claim 1, claim 2, claim 3, or claim 4.

11. The aforementioned plastic deformation process applies a strain of 60% or more at room temperature. A method for processing a metal body according to claim 1, claim 2, claim 3, or claim 4.

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