Testing and manufacturing methods for dissimilar aluminum bonding materials

Abstract

To provide a test method and a manufacturing method for a heterogeneous aluminum joint material.SOLUTION: A test method for a heterogeneous aluminum joint material of the present invention uses plate-like test materials, wherein when the thickness of each of the test materials is defined as h, the length in a long side direction or a major axis direction as LL, and the length in a short side direction or a minor axis direction being the length LL or less, the test materials used satisfy LS, 0.13≤h / LS≤0.54. The method comprises: heating a plurality of metal test materials having the shape of the test material and not having the same component in an overlapped manner; applying a compressive force in a thickness direction to the plurality of test materials to form a heterogeneous aluminum joint material in which the plurality of test materials are joined to each other; and applying a shear force to a joint surface of the obtained heterogeneous aluminum joint material to evaluate bonding strength.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This invention relates to a method for testing and manufacturing dissimilar aluminum joint materials. [Background technology]

[0002] One known method of joining metals is compression bonding by hot plastic deformation. Hot rolling, in particular, offers high productivity and is widely used industrially for joining dissimilar aluminum sheets, for example. In joining metals by hot plastic deformation, the greater the difference in strength (difference in deformation resistance), the more difficult the manufacturing process becomes. More specifically, in hot rolling, even if a joint appears to have formed, if rolling continues and stress exceeding the joint strength acts on the joint interface, delamination can occur, impairing productivity. In the worst case, if the joint is not formed properly, misalignment may prevent the manufacturing of the desired shape. Therefore, understanding the degree of joint strength achieved through hot plastic deformation is considered an important technical topic.

[0003] Conventionally, for example, Patent Document 1 discloses a technique for reducing a sheet while avoiding delamination by specifying a reduction ratio of 1.0% to 5% when the sheet thickness is 60% or more of the initial thickness. Furthermore, Patent Document 1 discloses a technique for rolling a sheet with a reduction ratio of 5% to 15% when the subsequent sheet thickness is 30% or more of the initial thickness but less than 60%. Patent Document 2 discloses a technique for manufacturing aluminum clad materials, in which the critical shear stress at which delamination does not occur is determined based on rolling performance data, this critical shear stress is quantified using the cumulative strain at the interface, the shear stress acting at the interface for each rolling pass is determined by numerical analysis, and the design is made so that the shear stress does not exceed the critical shear stress.

[0004] Non-patent document 1 below describes a test method for measuring tensile strength by stacking a first cylindrical body 100 made of Cu, a disc body 101 made of Al, and a second cylindrical body 102 made of Cu, as shown in Figure 10, and applying pressure to obtain a jointed material, and then conducting a tensile test on the first cylindrical body 100 and the second cylindrical body 102 in a direction that separates them along their central axes. Non-patent document 2 below describes a study on the effect of the amount of interfacial slip on the joint strength in hot compression bonding, in which cylindrical test pieces 107 and 108, which simulate the core material and outer material, are stacked between a base 105 and a punch 106 arranged vertically as shown in Figure 11(A), and the joints are pressed together while heated to 500°C. Furthermore, Non-Patent Literature 2 describes a test method for gradient compression testing, as shown in Figure 11(B), in which a cylindrical upper test piece 110 having a tapering inclined surface 109 and a cylindrical lower test piece 112 having an inclined concave surface 111 that receives the inclined surface 109 are placed between a base 105 and a punch 106. In this test method, the joint surface of the upper test piece 110 and the lower test piece 112, which are likened to a core material and an outer layer, is an inclined surface, and it is stated that the effect of the amount of interfacial slip can be understood. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 09-184038 [Patent Document 2] Japanese Patent Publication No. 2007-098444 [Non-patent literature]

[0006] [Non-Patent Document 1] "Plastic Processing Technology Series 19 1.4 Evaluation of Joint State," published by Corona Publishing Co., Ltd., edited by the Japan Society for Technology of Plasticity, 1990, p. 16 [Non-Patent Document 2] Shuhei Fujii et al., "Influence of Interfacial Slip Amount on Joint Strength in Hot Compression Joining," 70th Japan Society for Plasticity Processing Conference, pp. 221-222, October 12-13, 2019.

Summary of the Invention

Problems to be Solved by the Invention

[0007] Since the technique for adjusting the reduction rate described in Patent Document 1 does not consider the influence of the material composition, a technique that contributes to the efficiency improvement of the pass schedule, such as achieving a higher reduction rate even earlier, cannot be found. In the method for obtaining the critical shear stress described in Patent Document 2, there is a problem that the pass schedule cannot be determined in the case of a material composition with little experience, and there is also a problem that the application results and examples for specific materials are not disclosed as examples.

[0008] According to the description in Non-Patent Document 1, it is described that annealing is performed at 300°C or lower after cold welding with a compression ratio of 50 to 70%. However, for example, it is not easy to control the reduction rate to about 2 to 20%, and since the Al disk body 101 has a thickness of 2 mm or less, it is considered that an appropriate shear test is not easy. According to the technique described in Non-Patent Document 2, in FIG. 11(A), it is considered that it is not easy to deform the cylindrical lower test piece 107 that has received pressure into a barrel shape and apply a large deformation to the interface to be joined. For this reason, it is assumed that it is not easy to evaluate the joining strength corresponding to a large interface deformation amount. Also, in FIG. 11(B), it is assumed that it is not easy to increase the deformation amount of the interface. Also, it is considered that there is no evaluation method other than directly pulling the test piece after compression in FIG. 11(B) in the vertical direction.

[0009] [[ID=二十]]On the other hand, conventionally, it has been possible to collect samples by conducting pilot tests of hot working on an actual scale or medium scale (by actually performing hot rolling), and evaluate the joining strength of each sample. However, the evaluation method on an actual scale or medium scale has a problem that it is extremely costly as a pilot test because, for example, it is not easy to change the conditional variables. Therefore, it is desirable that the method for evaluating the joining strength be an evaluation method in a small-scale test using a compression testing machine, a tensile testing machine, or the like.

[0010] However, conventional small-scale testing methods have made it difficult to evaluate the bonding properties between dissimilar metals that have differences in strength (differences in deformation resistance). This is because plastic deformation involves the deformation of each material, presenting different challenges compared to evaluating joint strength in welding or brazing, where there is no significant change in shape. For example, metals with lower strength may deform more than those with higher strength, and in extreme cases, only metals with lower strength may deform. Furthermore, because the shape of each metal changes due to plastic deformation, even if strength evaluations are performed by simply pulling the specimens, the specimen shapes will not be consistent, making it difficult to conduct a fair evaluation using this testing method.

[0011] The present invention was made in view of the above-mentioned background, and aims to provide a testing method that allows for small-scale testing using compression testing machines, tensile testing machines, etc., and enables the evaluation of joint strength by performing a shear test after cutting out a test piece from dissimilar aluminum joint materials. Furthermore, the present invention aims to provide a method for manufacturing dissimilar aluminum joints using joint strength measurement results obtained by changing the type of material constituting the dissimilar aluminum joint, the pressurizing conditions, and the heating temperature in the shear test described above. [Means for solving the problem]

[0012] (1) The method for testing dissimilar aluminum joint materials according to the present invention is: In plan view, it is a rectangle, circle, or ellipse and Flat plate test Piece The thickness is h, and the length in the long side direction or along the long axis direction is L. L , the aforementioned length L L The length in the short side direction or short axis direction is L S year If the lengths of the long side and the short side are equal, or the lengths of the major axis and the minor axis are equal, the length of the side or diameter is L. S year At that time, 0.13 ≤ h / L S ≤ 0.54 Made of pure aluminum or aluminum alloy test Piece Using the test Piece They have the same shape and their components are not identical. Made of pure aluminum or aluminum alloy Testing of manufacturing Piece Multiple layers are stacked and heated to a desired temperature, and a compressive force is applied in the thickness direction to perform the multiple tests. PieceA dissimilar aluminum joint material is formed by joining these materials. An intermediate test piece is cut from the dissimilar aluminum joint material so as to include the central part of the dissimilar aluminum joint material along one of the following cross-sections: a plurality of cross-sections parallel to the short side direction or short axis direction of the test piece and extending in the thickness direction of the test piece; a plurality of cross-sections parallel to the long side direction or long axis direction of the test piece and extending in the thickness direction of the test piece if the lengths of the long side and short side or the long axis and short axis are equal; and then an actual test piece for evaluating joint strength is cut from the intermediate test piece so as to include the central part of the intermediate test piece and along a plurality of cross-sections extending in the thickness direction of the intermediate test piece. obtained The aforementioned test specimen The method is characterized by applying a shear force to the joint surface and evaluating the joint strength.

[0013] (2) In the method for testing dissimilar aluminum joint materials according to the present invention, the flat plate test Piece The plane is rectangular in plan view, and the test Piece It is preferable to apply the compressive force using a mold that applies the compressive force while constraining the deformation in the long-side direction of the material. (3) In the method for testing dissimilar aluminum joint materials according to the present invention, the test Piece In this process, it is preferable that the surface roughness Ra of the surfaces to be joined before joining is 0.01 μm or more and 30 μm or less. (4) In the method for testing dissimilar aluminum joint materials according to the present invention, it is preferable that the reduction ratio when applying the compressive force in the thickness direction of the test piece to form the dissimilar aluminum joint material be 2% or more and 20% or less.

[0014] (5) The method for manufacturing a dissimilar aluminum joint material according to the present invention is (1) ~ (4) In the method for testing dissimilar aluminum joint materials described in any of the above, a plurality of the above tests Piece The method is characterized by making at least one change from among the changes in the composition, the reduction ratio, and the heating temperature, determining the effect of the changes on the test results of the joint strength, and manufacturing a dissimilar aluminum joint material based on one or more conditions from among the composition, reduction ratio, and heating temperature that yielded good joint strength. (6) In the method for manufacturing a dissimilar aluminum joint material according to the present invention, the dissimilar aluminum joint material is made of pure aluminum or an aluminum alloy and is subjected to one of two to four tests. Piece A dissimilar aluminum joint material having a 2-layer to 4-layer structure in which two to four different aluminum materials are joined together, and one of the two to four types of tests Piece At least one of the other exams PieceIt is preferable that it consists of pure aluminum or an aluminum alloy with a different composition. [Effects of the Invention]

[0015] According to the test method of the present invention, the shape of the test specimen is 0.13 ≤ h / L S Since the value is specified as ≤0.54, even in the case of dissimilar aluminum joint materials consisting of combinations of dissimilar metals with different compositions and therefore different strengths, the joint strength at the interface between dissimilar metals can be reliably measured by testing using a test material with a specified ratio range of short side length to thickness, and applying shear force to this test material. The test method of the present invention is an evaluation method that allows for small-scale testing using compression testing machines, tensile testing machines, etc., is easy to implement, and has the advantage of being applicable to any combination of dissimilar metals used in the joint material. Therefore, since the bonding strength that causes interfacial delamination in dissimilar aluminum joining materials can be determined in advance, when manufacturing clad materials such as two-layer or three-layer structures, an appropriate compression ratio can be selected according to the pass schedule and utilized in the clad material manufacturing method. [Brief explanation of the drawing]

[0016] [Figure 1] This shows an example of a plate-shaped test piece suitable for use in the test method for dissimilar aluminum joint materials according to the present invention. (A) is a front view showing the test pieces stacked before joining, and (B) is a front view showing the test pieces after joining. [Figure 2] This is a perspective view showing the same plate-shaped test specimen. [Figure 3] The images show the test specimens of the comparative example; (A) is a front view showing the plate-shaped test specimens stacked before joining, and (B) is a front view showing the test specimen after joining. [Figure 4]This diagram illustrates various methods for evaluating adhesive strength as specified in JIS standards. (A) is an explanatory diagram showing a test specimen for the tensile test specified in JIS K 6849, (B) is an explanatory diagram showing a test specimen for the tensile shear test specified in JIS K 6850, (C) is an explanatory diagram showing a test specimen for the compression shear test specified in JIS K 6852, (D) is an explanatory diagram showing a test specimen for the splitting test specified in JIS K 6853, (E) is an explanatory diagram showing a test specimen for the 180° peel test specified in JIS K 6854, (F) is an explanatory diagram showing a test specimen for the T-type peel test specified in JIS K 6854, (G) is an explanatory diagram showing a test specimen for the impact test specified in JIS K 6855, and (H) is an explanatory diagram showing a test specimen for the bending test specified in JIS K 6856. [Figure 5] This diagram illustrates the problems that arise when applying plate-shaped test specimens suitable for use in the present invention to JIS-specified tensile shear tests or JIS-specified compression shear tests. [Figure 6] This diagram illustrates the process of cutting test specimens from a dissimilar aluminum joint material. (A) is a perspective view showing the cutting position of the dissimilar aluminum joint material, (B) is a perspective view showing an intermediate test specimen cut from the dissimilar aluminum joint material, and (C) is a perspective view showing the actual test specimen cut from the intermediate test specimen. [Figure 7] This is an explanatory diagram illustrating a test in which shear stress is applied to the test specimen shown in Figure (C)6 using the test method according to the present invention. [Figure 8] This figure shows a test in which shear stress is applied to the test specimen shown in Figure 6(C) using a conventional testing machine, where (A) is an explanatory diagram of the testing machine and (B) is a diagram showing the bending moment acting on the test specimen. [Figure 9] This is an explanatory diagram showing a plate-shaped test specimen applicable to the test method according to the present invention and a suitable hot compression apparatus for its preparation, where (A) is a perspective view showing the main part of the hot compression apparatus, (B) is a perspective view showing the cutting position of the dissimilar aluminum joint material, (C) is a perspective view showing an intermediate test specimen cut from the dissimilar aluminum joint material, and (D) is a perspective view showing the actual test specimen cut from the intermediate test specimen. [Figure 10] This is an explanatory diagram showing a sample used in the compression method described in Non-Patent Document 1. [Figure 11] This shows the compression method described in Non-Patent Document 2, where (A) is a side view showing the first example and (B) is a side view showing the second example. [Modes for carrying out the invention]

[0017] An embodiment of the present invention will be described in detail below based on the attached drawings. Note that, for convenience, the drawings used in the following description may show enlarged portions of key features to make them easier to understand.

[0018] The inventors prepared two aluminum alloy metal plates with different compositions, stacked these two metal plates, set them in a mold, and pressure-bonded them at 420-520°C to produce a two-layer dissimilar aluminum joint material. When they cut out rod-shaped test pieces from the resulting dissimilar aluminum joint material, they found that stress was applied to the joint interface of the dissimilar aluminum joint material during cutting, causing delamination at the interface, and making it impossible to evaluate the joint strength. In light of the results of this initial test, the inventors considered and estimated that the ratio of the height, width, and length of the dissimilar aluminum joining material used in the test might be important.

[0019] Figure 1(A) shows two plate-shaped test pieces 1 and 2 stacked together, which are effective in obtaining a dissimilar aluminum joint material of a desired shape based on the results of the examples and comparative examples which will be described in detail later. Figure 1(B) shows a model structure of the two-layer dissimilar aluminum joint material 3 after compression bonding. In the following description of this embodiment, it is assumed that the strength of plate-shaped test piece 1 is higher than the strength of plate-shaped test piece 2. The plate-like test pieces 1 and 2 in Fig. 1(A) are compressed to apply a compressive force in their thickness directions, and a dissimilar aluminum joint material 3 composed of a first layer 1A and a second layer 2A shown in Fig. 1(B) can be obtained. In this dissimilar aluminum joint material 3, the second layer 2A generated from the plate-like test piece 2 with lower strength has a greater degree of deformation, and the second layer 2A has a larger deformation amount than the first layer 1A. Also, the portion indicated by reference numeral 4 in Fig. 1(B) shows a joint portion that is adhered at the interface between the first layer 1A and the second layer 2A. This joint portion 4 is generated in a region excluding both end portions in the width direction of the first layer 1A and the second layer 2A.

[0020] Fig. 2 shows a perspective view of the plate-like test piece 1 before joining. This plate-like test piece 1 is rectangular in plan view, with a long side length L L , a short side length L S , and is assumed to have a height (thickness) h, where h < L S < L L has the relationship. Also, from the comparison results of the examples and comparative examples described later, it is desirable that the plate-like test pieces 1 and 2 have a relationship of 0.13 ≦ h / Ls ≦ 0.54.

[0021] In contrast, Fig. 3 shows an example of a plate-like test piece that is likely to peel at the interface after joining. As shown in Fig. 3(A), it has a structure in which the plate-like test piece 5 and the plate-like test piece 6 are stacked, and is a combination of plate-like test pieces 5 and 6 having a relationship of h > Ls. Here too, it is assumed that the strength of the plate-like test piece 5 is higher than the strength of the plate-like test piece 6.

[0022] When joined by a compressive force as shown in Fig. 3(B), it becomes a two-layer structure in which the first layer 5A and the second layer 6A are laminated. However, at the interface between the first layer 5A and the second layer 6A, only narrow joint portions 7, 7 are generated at both end portions of the interface. In the joint structure shown in Fig. 3(B), since it is only partially joined, when the test piece is cut, it easily peels at the joint interface. When there is a strength difference between the plate-like test pieces 5 and 6, deformation tends to concentrate on the side with lower strength (on one side of the plate-like test piece 6), so it can be expected that such narrow joint portions 7, 7 will be generated.

[0023] On the other hand, as shown in Figures 1 and 2, in plate-shaped test specimens 1 and 2, which have the relationship 0.13 ≤ h / Ls ≤ 0.54, both the upper and lower test specimens deform uniformly, and the entire interface is joined. More specifically, the high-strength material tends to deform less than the low-strength material, but h / L S By reducing the height h, the unevenness in deformation is reduced, resulting in deformation that can be considered generally uniform. In this case, the interface is wide and the joint is generally overall, so specimen processing such as cutting can be done without problems. It can also be said that the relatively smaller ratio of height h makes it easier to apply pressure to the entire specimen, allowing for stable joint testing.

[0024] In specimens with a rectangular or circular cross-section, h / L S If Ls is less than 0.13, the interface is considered to be uniformly joined, but even if Ls = 20 mm, h becomes small, less than 4 mm, making it difficult to secure the length necessary for fixing the specimen to the test apparatus described later as a test piece for bonding strength. The test piece is made proportionally larger, L S While increasing the absolute value of h can also increase the load capacity and heating power required for the high-temperature compression testing machine, this increases costs. In contrast, 0.13 ≤ h / L S Within the range of ≤0.54, the bonding test described above can be performed without difficulty. Furthermore, for rectangular cross-sectional shapes, the range in which bonding tests can be performed smoothly and successfully is 0.2 ≤ h / L. S You can select a range of ≤0.54. h / L S If the value is less than 0.13, it is necessary to limit the reduction ratio of the hot compression being evaluated. In this embodiment, the shape of the test specimen is not limited to being changed proportionally, but each time a test is performed, the size of the test specimen and the capacity and scale of the testing machine corresponding to the test specimen are balanced, so h / L S If the value is less than 0.13, we believe the testing equipment will be unnecessarily expensive.

[0025] Based on the above explanation, when we examine the shapes of test specimens 1 and 2, the h / L ratio in the long-side direction of the plate-shaped test specimens 1 and 2 is smaller than that in the short-side direction, therefore the h / L ratio in the short-side direction SThis is considered a parameter that deserves attention.

[0026] Next, the inventors considered that evaluation conditions are also important when conducting tests to determine bonding strength. Figure 4 shows various methods for evaluating adhesive strength as specified in JIS. Figure 4(A) shows the test specimen and direction of tensile force application for the tensile test specified in JIS K 6849, and Figure 4(B) shows the test specimen and direction of tensile force application for the tensile shear test specified in JIS K 6850. Figure 4(C) shows the test specimen and direction of force application for the compression shear test specified in JIS K 6852, and Figure 4(D) shows the test specimen and direction of force application for the splitting test specified in JIS K 6853. Figure 4(E) shows the test specimen and tensile direction for the 180° peel test specified in JIS K 6854, and Figure 4(F) shows the test specimen and direction of force application for the T-type peel test specified in JIS K 6854. Figure 4(G) shows the test specimen and direction of force application for the impact test specified in JIS K 6855, and Figure 4(H) shows the test specimen and direction of force application for the bending test specified in JIS K 6856.

[0027] In light of these various evaluation conditions, the inventors considered that when determining the joint strength in a joint made by hot plastic deformation, so as not to delaminate the joint surface during testing, shear in the direction along the interface is more important than tensile in the direction perpendicular to the interface. Furthermore, the inventors considered it effective to perform the test specimen processing described below. However, the test specimen processing method described below is merely one example of how to implement the present invention, and the inventors are not limited to this processing method when implementing the present invention.

[0028] In the case of the dissimilar aluminum joint material 3 having a first layer 1A and a second layer 2A as shown in Figure 5(A), in order to perform a tensile shear test in accordance with JIS K 6850 as shown in Figure 5(B), the first layer 1A and the second layer 2A need to be further processed into the shapes shown in Figure 5(B). Furthermore, as shown in Figure 5(C), even when conducting a compression shear test in accordance with JIS K 6852, the first layer 1A and the second layer 2A need to be further processed, which presents a problem as delamination is likely to occur during processing, making it impractical. If the joining method is one that does not deform before and after joining, such as welding, the joined body can be manufactured with strength testing in mind from the beginning. However, in the case of dissimilar aluminum joining material 3, the processing method is time-consuming. Furthermore, it is thought that unless the joint is processed with high precision as shown in the drawings described below, it will not be possible to properly apply shear force to the joint interface.

[0029] In this embodiment, the processing is carried out in the order shown in Figures 6(A), (B), and (C) to cut out an intermediate test piece 10 from the dissimilar aluminum joining material 3, and a test piece 11 for evaluating the joint strength is obtained by cutting out a test piece 11 from this intermediate test piece 10. Using this test piece 11, the joint strength can be measured using the test apparatus 30 shown in Figure 7, which will be described later, and the measured joint strength can be evaluated.

[0030] As shown in Figure 6(A), the dissimilar aluminum joint material 3 is cut along the cross-sectional surfaces S1 and S2 that exist along the thickness direction of the dissimilar aluminum joint material 3 at the positions indicated by the dashed lines L1 and L2, and an intermediate test piece 10 is produced as shown in Figure 6(B). The cross-sectional surfaces S1 and S2 are located on both sides of the length direction of the dissimilar aluminum joint material 3, and the cross-sectional surfaces S1 and S2 along the dashed lines L1 and L2 are formed at positions perpendicular to the length direction of the dissimilar aluminum joint material 3 (parallel to the short side direction). As an example, the length L of the dissimilar aluminum joint material 3 is... L If the length is 40 mm, one cross-section S1 is formed at a position 12 mm apart in the same length direction from one end of the dissimilar aluminum joint material 3, and the other cross-section S2 is formed at a position 12 mm apart in the same length direction from the other end of the dissimilar aluminum joint material 3. Therefore, the length of the intermediate test piece 10 along the length direction of the dissimilar aluminum joint material 3 is 16 mm. In reality, there is a slight width to be cut from the dissimilar aluminum joint material 3, so the length of the intermediate test piece 10 will be approximately 14 to 18 mm.

[0031] Next, in the intermediate test piece 10, dashed lines L3 and L4 are drawn spaced apart on both sides in the short-side direction, flanking a region with a width of 2.0 to 2.5 mm in the central part in the short-side direction. By cutting along these dashed lines L3 and L4 along the cross-sectional surfaces S3 and S4 that exist in the thickness direction of the intermediate test piece 10, a rod-shaped test piece 11 shown in Figure 6(C) can be obtained. As described above, when the test specimen 11 is cut out, it is assumed that there are unjointed portions at both ends in the width direction (both ends in the short side direction) of the dissimilar aluminum joining material 3, just as in the case where the joint portion 4 is not formed at both ends in the width direction of the first layer 1A and the second layer 2A as shown in Figure 1(B), and the test specimen 11 is cut out excluding the unjointed portions.

[0032] In the cutting process for the dissimilar aluminum joint material 3 and intermediate test piece 10 shown in Figures 6(A) to (C), unlike the processing shown in Figure 5(A)→(B) or Figure 5(A)→Figure 5(C), the load on the first layer 1A and the second layer 2A can be reduced, thus reducing the load acting on the joint surface between the first layer 1A and the second layer 2A. Therefore, when obtaining the test piece 11 by processing from the dissimilar aluminum joint material 3, delamination at the joint interface can be prevented. Regarding the cutting process, the procedure shown in Figure 6 is preferable, but it is also acceptable to adopt a procedure in which, while taking the same considerations as described above, an intermediate test piece is cut parallel to the length direction of the joining material 3 as shown in Figure 6(A), and then the final test piece 11 is cut. The test specimen 11 is formed by joining a rod-shaped first joining piece 15, cut from the first layer 1A, to a rod-shaped second joining piece 16, cut from the second layer 2A. The first joining piece 15 and the second joining piece 16 are joined together with one surface of the first joining piece 15 and one surface of the second joining piece 16 butting against each other. The surface where one surface of the first joining piece 15 and the one surface of the second joining piece 16 meet is called the joining surface 17.

[0033] Here, in the test specimen 11, one surface of the first joining piece 15 and one surface of the second joining piece 16 are joined via a joining surface 17, and the end surface 15a of the first joining piece 15 and the end surface 16a of the second joining piece 16 are aligned flush as shown in Figure 6(C). Hereinafter, in the rectangular surface formed by aligning the end surfaces 15a and 16a flush, the longer side will be referred to as the width W of the test specimen 11, and the shorter side will be referred to as the thickness t of the test specimen 11. Once the test specimen 11 is obtained, a shear test is performed on the test specimen 11 using the test apparatus shown in Figure 7.

[0034] Figure 7 shows a test apparatus 30 used when carrying out the test method according to this embodiment. This test apparatus 30 has a lower clamping jig 31 and an upper clamping jig 32, and the lower clamping jig 31 and the upper clamping jig 32 are supported so as to be able to move closer to and further apart in the vertical direction by a support mechanism (not shown). By attaching the test piece 11 to this test apparatus 30 as shown in Figure 7, the joint strength measurement test described later can be carried out. A support plate 33 having the same thickness t as the test specimen 11 is placed between the lower clamping jig 31 and the upper clamping jig 32, while being clamped by them. Furthermore, the first joining piece 15 of the test specimen 11 is placed between the lower clamping jig 31 and the upper clamping jig 32, adjacent to the support plate 33, while being clamped by them. For the test specimen 11, the majority of the first joining piece 15 is clamped by the lower clamping jig 31 and the upper clamping jig 32, but the clamping is performed such that a portion of the joining surface 17 side of the first joining piece 15 protrudes slightly outward from the side surface 31a of the lower clamping jig 31 and the side surface 32a of the upper clamping jig 32.

[0035] In the test apparatus 30, a lower clamping jig 35 and an upper clamping jig 36 are provided on the outer sides of the side surface 31a of the lower clamping jig 31 and the side surface 32a of the upper clamping jig 32, and the lower clamping jig 35 and the upper clamping jig 36 are provided so as to be able to move vertically and move closer to and further away from each other by a support mechanism not shown. The majority of the second connecting piece 16, which protrudes outward from the side surface 31a of the lower clamping jig 31 and the side surface 32a of the upper clamping jig 32, is gripped from above and below by the lower clamping jig 35 and the upper clamping jig 36. In addition, a support plate 34 having a thickness equivalent to the thickness t of the test piece 11 is clamped together with the second connecting piece 16 between the lower clamping jig 35 and the upper clamping jig 36.

[0036] A small clearance (gap) is provided between the side surface 31a of the lower clamping jig 31 and the lower clamping jig 35. To fill this gap, the lower lubrication tape 37 is attached to the side surface 31a of the lower clamping jig 31, and the lower lubrication tape 38 is attached to the side surface of the lower clamping jig 35. A small clearance (gap) is provided between the side surface 32a of the upper clamping jig 32 and the lower clamping jig 36. To fill this gap, the upper lubrication tape 39 is attached to the side surface 32a of the upper clamping jig 32, and the upper lubrication tape 40 is attached to the side surface of the upper clamping jig 36. In the test apparatus 30, the above-mentioned clearance can be set to, for example, about 0.8 mm. To fill this clearance, a lower lubrication tape 37 and a lower lubrication tape 38 are provided below the test specimen 1, and the thickness of these lubrication tapes is set to about 0.4 mm. In addition, an upper lubrication tape 39 and an upper lubrication tape 40 are provided above the test specimen 11, and the thickness of these lubrication tapes is also set to about 0.4 mm.

[0037] Once the test specimen 11 is set up as shown in Figure 7, the upper clamping jig 36 and the lower clamping jig 37 are lowered, and a downward pressing force is applied to the second joining piece 16 that is clamped by these jigs. By applying this pressing force, the shear test of the test specimen 11 can be performed. By sequentially increasing the pressing force on the second joining piece 16, the pressing force at the point when the first joining piece 15 and the second joining piece 16 separate via the joining surface 17 in the test specimen 11 can be determined as the joining strength. More specifically, the joining strength can be determined by dividing the maximum load when shear force is applied by the interfacial cross-sectional area. The lower clamping fixture 35 and the upper clamping fixture 36 are connected to a hydraulic device (not shown) and moved up and down. As the pressing force on the test specimen 11 increases, the joint surface 17 will eventually undergo shear failure, and the load at the time of shear failure can be determined by a load cell provided in the hydraulic device (not shown). The joint strength can be determined by dividing the applied load by the interfacial cross-sectional area of ​​the test specimen 11.

[0038] In the test apparatus 30, a shear test can be performed while minimizing the bending moment acting on the first joint piece 15 and the second joint piece 16. Furthermore, the clearance between the lower clamping jig 31 and the lower clamping jig 35, and the clearance between the upper clamping jig 32 and the upper clamping jig 36 are sealed with lubricating tapes 37, 38, 39, and 40 while the upper clamping jig 36 and the lower clamping jig 37 are lowered to perform the shear test. As a result, the bending moment caused by the aforementioned clearances is minimized, and the joint strength can be measured by applying only shear force to the joint surface 17 of the first joint piece 15 and the second joint piece 16, eliminating the bending moment. Furthermore, by inserting a support plate 33 between the lower clamping jig 31 and the upper clamping jig 32, and a support plate 34 between the lower clamping jig 35 and the upper clamping jig 36, shear force can be applied while stably supporting the test specimen 11.

[0039] Figure 8(A) shows a test apparatus 43 in which the lower support jig 35 and support plate 34 are omitted from the test apparatus 30 shown in Figure 7, and a pressing jig 41 is provided in place of the upper clamping jig 36, and the upper surface of the second joining piece 16 is pressed downward by the pressing jig 41 to perform a shear test. In the test apparatus 43 shown in Figure 8(A), bending moments mf1 and mf2 act on both the first joining piece 15 and the second joining piece 16, as shown in an enlarged view in Figure 8(B). When bending moments mf1 and mf2, as shown in Figure 8(B), are applied, a tensile force acts on the upper side of the joint 17 between the first connecting piece 15 and the second connecting piece 16, pulling the first connecting piece 15 and the second connecting piece 16 apart. Additionally, a compressive force acts on the lower side of the joint 17 between the first connecting piece 15 and the second connecting piece 16, applying pressure to bring the two pieces closer together. When a tensile force acts on the upper side of the joint 17, the conditions become one of shear stress plus tensile force, which may result in unstable results for a basic test. In this regard, the test apparatus 30 shown in Figure 7 makes it possible to measure joint strength based solely on shear, minimizing the influence of bending moment, thus enabling more accurate measurements.

[0040] Figure 9(A) shows a hot compression apparatus 50 used to produce a dissimilar aluminum joint material 3 suitable for use in testing to determine the joint strength of this embodiment. The hot compression device 50 is equipped with a rectangular block-shaped lower die 51 and a punch 52, and a channel groove 53 for receiving plate-shaped test pieces 1 and 2 shown in Figure 1 is formed on the upper surface of the lower die 51. The groove width MW of the channel groove 53 is, for example, the length L of the long side of the plate-shaped test piece 1. L It is formed in the same way as the other. Also, the length of the channel groove 53 in the direction perpendicular to the groove width is the same as the aforementioned long side length L. L It is formed to be larger than the above. For example, in the lower mold 51 shown in Figure 9(A), one end 53a in the longitudinal direction of the channel groove 53 reaches one end of the lower mold 51 and is open, and the other end 53b in the longitudinal direction of the channel groove 53 reaches the other end of the lower mold 51 and is open. The channel groove 53 is formed to a depth of several times the total thickness of the stacked plate-shaped test pieces 1 and 2, for example.

[0041] The punch 52 has a projection 54 that can be fitted into the channel groove 53 of the lower die 51. The height of the projection 54 is equal to the depth of the channel groove 53. The lower die 51 and the punch 52 are provided to be able to move relative to each other by a moving mechanism such as a hydraulic device (not shown). For example, the lower die 51 is fixed, and the punch 52 is supported to be able to move up and down relative to the lower die 51. In addition, the lower die 51 and the punch 52 are equipped with a heating device (heater) (not shown) that can be used to heat the lower die 51 and the punch 52 to a desired temperature (e.g., 200°C to 800°C). To set and join plate-shaped test pieces 1 and 2 in the hot compression device 50, the plate-shaped test pieces 1 and 2 are placed in the channel groove 53 of the lower mold 51 in the orientation shown in Figure 9(A). The length of the long side of plate-shaped test pieces 1 and 2 is L. L Since the groove width of the channel groove 53 is equal to that of the plate-shaped test pieces 1 and 2, the ends on the shorter sides of the plate-shaped test pieces 1 and 2 are inserted into both corners of the channel groove 53 without any gaps, and the plate-shaped test pieces 1 and 2 are housed in the center of the bottom of the channel groove 53. After this, the punch 52 is lowered at a predetermined speed to insert the protrusion 54 into the channel groove 53, and the plate-shaped test pieces 1 and 2 are pressed against the lower surface of the protrusion 54. By applying a compressive force in the thickness direction of the plate-shaped test pieces 1 and 2, the plate-shaped test pieces 1 and 2 are joined together, and a dissimilar aluminum joint material 3 can be obtained.

[0042] When plate-shaped test pieces 1 and 2 are joined by hot compression, a dissimilar aluminum joint material 3 is obtained as shown in Figure 9(B). An intermediate test piece 10 is obtained by cutting along the cross-sections S1 and S2 along the dashed lines L1 and L2 of this dissimilar aluminum joint material 3, as shown in Figure 9(C). The final test piece 11 is obtained by cutting along the cross-sections S3 and S4 along the dashed lines L3 and L4 of this intermediate test piece 10, as shown in Figure 9(D). The hot compression device 50 shown in Figure 9(A) restrains both ends of the plate-shaped test pieces 1 and 2 in the longitudinal direction with the inner surface of the groove wall of the channel groove 53, thereby suppressing elongation of the plate-shaped test pieces 1 and 2 in the longitudinal direction and applying a compressive force to them. As a result, for example, as illustrated in Figure 1(B), the plate-shaped test piece 2 with lower strength deforms so as to bulge slightly on both sides in the width direction, resulting in a dissimilar aluminum joint material 3 in which the deformation of plate-shaped test piece 1 is small and the deformation of plate-shaped test piece 2 is large.

[0043] Furthermore, multiple test specimens 11 can be cut from the intermediate test specimen 10. In this case, in addition to the dashed lines L3 and L4, dashed lines L5 and L6 are drawn at equal intervals relative to them, and by cutting along these dashed lines L5 and L6 along the cutting surface extending in the thickness direction of the intermediate test specimen 10, for example, three test specimens 11 can be obtained.

[0044] "Method for manufacturing dissimilar aluminum joint materials" Earlier, we explained that a test can be conducted to measure the joint strength of a test specimen 11 cut from a dissimilar aluminum joint material 3 using the test apparatus 30 shown in Figure 7. In this embodiment, when producing a dissimilar aluminum joint material 3, by appropriately changing the materials of the plate-shaped test pieces 1 and 2, and adjusting the magnitude of the compressive force applied to the plate-shaped test pieces 1 and 2, as well as the heating temperature, it is possible to create multiple dissimilar aluminum joint materials corresponding to the type of material, the magnitude of the compressive force, and the heating temperature. Then, by cutting out test pieces from the multiple dissimilar aluminum joint materials and measuring the joint strength as described above, it is possible to understand what kind of joint strength can be obtained depending on the type of material, the magnitude of the compressive force, and the heating temperature. In other words, depending on the type of material, it becomes possible to determine what temperature and compressive force are required to achieve a certain level of interlaminar bonding strength as a clad material.

[0045] Therefore, when manufacturing a clad material with a two-layer laminated structure, the type of material to select and the appropriate temperature and compressive force for cladding can be determined in advance through the above-mentioned tests to determine what level of joint strength can be achieved in a two-layer clad material. Based on these findings, a material can be selected, and by applying the desired temperature and compressive force and manufacturing the clad material by rolling, a clad material with the desired bonding properties can be obtained.

[0046] In the example described above, a two-layer dissimilar aluminum joint material 3 was used as an example. However, when manufacturing clad materials with a multilayer structure such as a three-layer or four-layer structure, a similar joint strength test can be conducted. By manufacturing the clad material based on the test results, it is possible to produce a multilayer clad material with the desired interlayer bonding properties. In those cases, instead of the two-layer structure shown in Figure 1(A), a three-layer or four-layer dissimilar aluminum joint material can be fabricated, and test specimens can be cut from these and evaluated using the test apparatus 30 shown in Figure 7. Based on the evaluation results, a three-layer clad material or a four-layer clad material can be manufactured. Even when using a 3-layer or 4-layer structure, the previously explained 0.13 ≤ h / L S It is preferable that the relationship ≤ 0.54 is satisfied.

[0047] In the example described above, the case in which a dissimilar aluminum joint material 3 is manufactured using the hot compression device 50 shown in Figure 9(A) was explained. However, the device used to manufacture the dissimilar aluminum joint material 3 is not limited to the hot compression device 50. Any device that can apply compressive force in the thickness direction of the plate-shaped test pieces 1 and 2 may be used. Furthermore, the method and position for cutting the test specimen 11 from the dissimilar aluminum joint material 3 are not limited to the cutting method described based on Figures 6 and 9(A). In the examples shown in Figures 6 and 9(A), the case in which the test specimen 11 is cut from the central part of the dissimilar aluminum joint material 3 was described, but the test specimen 11 may also be cut from a position other than the central part.

[0048] Furthermore, as mentioned above, the metallic materials applied to plate-shaped test pieces 1 and 2 can be exemplified by pure aluminum or aluminum alloys, but are not limited to combinations thereof. Plate-shaped test pieces 1 and 2 may be a combination of aluminum alloys with different compositions, or a combination of pure aluminum and an aluminum alloy. Furthermore, the dissimilar aluminum bonding material 3 is not limited to a two-layer structure; a three-layer or four-layer structure can also be adopted. For example, it could be a laminate of three or four layers of aluminum alloy plates, which are widely used in fields such as heat exchangers. [Examples]

[0049] We prepared aluminum alloy samples A1 to A11, which are described below. • Aluminum alloy sample A1 Al-Mn alloy A1 containing 1.5% by mass of Mn, along with Cu and other unavoidable impurities, was manufactured. Ingots were prepared by melting and casting, and the alloy obtained by homogenizing the ingots at 500°C was used in this test. • Aluminum alloy sample A2 Al-Mn alloy A2 containing 1.2 mass% of Mn, along with Cu and other unavoidable impurities, was manufactured. Ingots were prepared by melting and casting, and the alloy obtained by homogenizing the ingots at 500°C was used in this test. • Aluminum alloy sample A3 Al-Mn alloy A3 containing 1.4 mass% of Mn, along with Cu, Mg, and unavoidable impurities, was manufactured. Ingots were prepared by melting and casting, and the alloys obtained by homogenizing the ingots at 500°C were used in this test. • Aluminum alloy sample A4 Al-Mn alloy A4 containing 1.2 mass% of Mn, along with Cu, Mg, and unavoidable impurities, was manufactured. Ingots were prepared by melting and casting, and the alloys obtained by homogenizing the ingots at 500°C were used in this test.

[0050] • Aluminum alloy sample A5 Al-Si alloy A5 containing 7.5% by mass of Si, along with Mg, Mn, and unavoidable impurities, was manufactured. Ingots were prepared by melting and casting, and the alloys obtained by homogenizing the ingots at 500°C were used in this test. • Aluminum alloy sample A6 Al-Si alloy A6 containing 12% by mass of Si, along with Mg, Mn, and unavoidable impurities, was manufactured. Ingots were prepared by melting and casting, and the alloys obtained by homogenizing the ingots at 500°C were used in this test. • Aluminum alloy sample A7 Al-Si alloy A7 containing 10% by mass of Si, along with Mg, Mn, and unavoidable impurities, was manufactured. Ingots were prepared by melting and casting, and the alloys obtained by homogenizing the ingots at 500°C were used in this test. • Aluminum alloy sample A8 Al-Zn alloy A8 containing 2.0 mass% Zn, along with Mn, Si, and unavoidable impurities, was manufactured. Ingots were prepared by melting and casting, and the alloys obtained by homogenizing the ingots at 500°C were used in this test.

[0051] • Aluminum alloy sample A9 Al-Zn alloy A9 containing 1.0 mass% of Zn, along with Mn and other unavoidable impurities, was manufactured. Ingots were prepared by melting and casting, and the alloys obtained by homogenizing the ingots at 500°C were used in this test. • Aluminum alloy sample A10 Al-Zn alloy A10 containing 2.0 mass% of Zn, along with Si and other unavoidable impurities, was manufactured. Ingots were prepared by melting and casting, and the alloys obtained by homogenizing the ingots at 500°C were used in this test. • Aluminum alloy sample A11 Al-Zn alloy A11 containing 5.0 mass% of Zn, along with Mn, Si, and unavoidable impurities, was manufactured. Ingots were prepared by melting and casting, and the alloys obtained by homogenizing the ingots at 500°C were used in this test.

[0052] Using the alloy combinations prepared as described above, various plate-shaped test specimens were fabricated in the combinations shown in Table 1 below, and bonding tests were conducted. The shape of each plate-shaped test specimen is as shown in Table 2 below, with h (height) and L L (Longest side length), L S (Short side length), h / L S It has a cylindrical or flat shape. The plate-shaped test specimens in the examples were rectangular or cylindrical, and the temperature range was 0.13 ≤ h / L as shown in Table 2. S The relationship is assumed to be ≤0.54. In the embodiment, h = compression direction (4 to 7.5 mm for rectangular shapes, 4 to 12 mm for circular shapes), L L =Length of the longest side (40mm for rectangles, 28-32mm for cylinders), L S =Short side length (14-20 mm for rectangular samples, including copper samples; 28-32 mm for cylindrical samples), but 0.13 ≤ h / L S If the ≤0.54 condition is met, the shape can be proportional to the specifications of the compression testing machine (maximum load / size that can be uniformly heated). Furthermore, the shape of the test specimen is not limited to rectangles or cylinders; it can also be an elliptical or polygonal thin plate.

[0053] In the example above, the upper side (SU side) was made of high-strength material and the lower side (SL side) of low-strength material, but the reverse is also acceptable. Surface smoothness is important in bonding. The samples used in this study were prepared by machining from ingots, and the arithmetic mean surface roughness Ra before bonding was set between 0.08 μm and 3.1 μm. Furthermore, the waviness Wa of each sample surface was set between 0.09 μm and 2.9 μm. While it is desirable to match the surface roughness Ra and waviness Wa to those of the target manufacturing process, it is also possible to intentionally vary the roughness within a controllable range for the target manufacturing process, for example, Ra from 0.012 μm to 25 μm, and evaluate the effect. A confocal laser microscope was used to measure Ra and Wa. However, other methods capable of measuring Ra between 0.012 μm and 25 μm may be used instead of a confocal laser microscope.

[0054] A hot compression device 50 was used, which included a lower die 51 having a channel groove 53 as shown in Figure 9(A) and a punch 52 facing it. In this example, the groove width of the channel groove 53 was set to 40 mm, and the length of the long side in the case of a rectangle L L It matches that. As explained above, the shape can be made proportional to the specifications of the compression testing machine (maximum load / size that can be heated uniformly). Furthermore, additional shape modifications to increase rigidity or modifications to improve heat uniformity for high-temperature testing may be incorporated.L The direction does not necessarily have to be constrained. In this case, it is not necessary to use the hot compression device 50 shown in Figure 9(A); heating and compression can be performed using a flat anvil. Since the direction of plastic flow of the material changes due to the constraint, the shape of the hot compression device can be appropriately selected according to the hot joining process to be considered.

[0055] Note that this embodiment does not present any examples where (deformation resistance of soft material ÷ deformation resistance of hard material) is 0.878 or higher. However, the plastic deformation behavior of two superimposed materials tends to become more homogeneous. Therefore, even if (deformation resistance of soft material ÷ deformation resistance of hard material) is 0.878 or higher, it does not deviate from the technical concept of the present invention. Even for combinations where (deformation resistance of soft material ÷ deformation resistance of hard material) is less than 0.377, a test to measure joint strength can be performed within the scope that does not deviate from the technical concept of the present invention.

[0056] Intermediate test specimens measuring 14-18 mm × 2-2.5 mm were cut from the central part of the dissimilar aluminum joint material obtained by hot compression, while maintaining the same thickness (see the area sandwiched between cut surfaces S1 and S2 in the central part of Figure 6(A)). For more details, see the previously mentioned longest side (L L The length in the ) direction should be 40 mm for a rectangle and 20-40 mm for a cylinder, as described above for the shorter side (L S The cutting process was carried out so that the length in the direction of the rectangle was 14-20 mm, and the length in the cylindrical direction was 28-32 mm. The method of the present invention can uniformly join the entire interface, but it is possible that the joint may not be perfect (partially unconnected at both ends in the width direction of the interface), as shown in the image of the joint in Figure 2(B). Therefore, it is preferable to cut the sample from as close to the center as possible.

[0057] If efficiency is prioritized over accuracy, shear force may be applied directly to the dissimilar aluminum joint material 3 without cutting out test specimens. In this example, the joint strength was measured by applying shear force to the cut test specimen 11 using the test apparatus 30 shown in Figure 7. Note L L , L S Depending on the absolute value of the force, the shape of the cut test specimen may be made proportional within the same ratio range and adopted. It is preferable to smooth the surface by polishing with 1000 grit or higher before applying the shear force. After that, the dimensions of the test specimen were measured and the interface cross-sectional area of ​​the test specimen was determined.

[0058] The deformation resistance shown in Table 1 was evaluated in a cylindrical compression test of 8 mm in diameter and 12 mm in height. The results are for a logarithmic strain of 0.1 at 480°C and a strain rate of 0.1 / sec. As shown in Tables 2 to 4 below, COM1 to COM7 were tested at 440°C to 520°C. The (compression) speeds shown in Tables 2 to 4 represent the compression speed of the punch during hot compression. The reduction ratios shown in Tables 2 to 4 were calculated based on the sum of the thicknesses of the two plates (the total thickness of the two plate-shaped test specimens and the total thickness of the first and second layers after compression). The bonding pressures shown in Tables 2 to 4 were determined by dividing the maximum load during hot compression by the initial sample cross-sectional area. The joint strengths shown in Tables 2 to 4 were determined by dividing the maximum load applied during shear stress by the interfacial cross-sectional area.

[0059] [Table 1]

[0060] [Table 2]

[0061] [Table 3]

[0062] [Table 4]

[0063] Tables 2 and 3 show comparative examples Nos. 1-7 and 19-28. The shape of the test specimens was h / L S Due to a coefficient of >0.54, it was not possible to process the test specimens after hot compression, making it impossible to evaluate the joint strength. In comparative examples No. 1-7 and 19-23, wire cutting was selected to minimize stress on the test specimen interface, but problems such as delamination of the joint surface occurred during handling during processing, preventing the test specimen processing from being completed. Examples Nos. 8-18 in Table 2 and Nos. 29-63 in Tables 2 and 3 are examples. The shape of the test specimen is 0.13 ≤ h / L S The range was consistent with the formula ≤0.54, resulting in test specimens with stable bonding conditions, and enabling evaluation of bonding strength. Note that for samples 8-18 and 24-63, grinding wheel cutting was used for efficiency reasons, but the value was 0.13 ≤ h / L. S If the value was ≤0.54, the test specimens could be processed without any problems. When processing test specimens no. 8-18 and no. 24-63, wire cutting may be performed.

[0064] Specimens No. 1-8, No. 19-23, No. 28, No. 35, and No. 45-47 are cylindrical in shape. h = cylindrical height (4-30 mm), L S =Cylinder diameter (20~32mm), h / L S The result was calculated. Specimens No. 9-18, No. 24-27, No. 29-34, No. 36-44, and No. 48-63 are rectangular in plan view. h = compression direction (4-9 mm), L L =Length of the longest side, (40mm), L S =Short side length (14-20 mm), h / L S The result was calculated. In the rectangular samples viewed from above, compression was performed without restraint in the long-side direction for samples no. 24, 26, 29, 31, 33, 36, and 42, while compression was performed with restraint in the long-side direction by the channel groove 53 of the hot compression device 50 shown in Figure 9(A). Samples No. 11-15 are examples of tests conducted five times under the same conditions. Practical stability was obtained for measuring bonding strength. Preferably, the test is repeated 3-5 times and the average is taken.

[0065] The results shown in Tables 2 to 4 indicate that temperature, compression rate, reduction ratio, and lubrication can be easily varied, and that the relationship between hot working conditions and joint strength can be investigated by systematically acquiring data. The lubrication shown in Tables 2 to 4 refers to the treatment between the lower die / punch and the sample surface, and the tests were conducted with no lubrication and lubrication by spraying BN powder. By applying lubrication, the bonding surface pressure is reduced, allowing for discussion of the effects of bonding surface pressure. Note that the lubrication method is not limited to BN powder lubrication; other lubrication methods may also be applied.

[0066] As shown in Table 1, the material types used were various combinations of COM1, COM2, COM3, COM4, ​​COM5, COM6, and COM7. As shown in the results in Tables 2 to 4, the tests could be conducted without any problems with any of the material types, and bonding tests to determine the bonding strength between dissimilar aluminum alloys were successfully performed.

[0067] "Manufacturing of 3-layer clad material" We fabricated a three-layer clad material by attaching a veneer material to both sides of the core material. A three-layer clad material was manufactured by forming one outer layer from the aforementioned A11 alloy, the core from the A4 alloy, and the other outer layer from the A5 alloy. The cladding ratio of one outer layer was 15% relative to the core, and the cladding ratio of the other outer layer was 20% relative to the core. The total thickness of the three-layer clad material was 600 mm. The rolling temperature was set to 480°C. When manufacturing such three-layer clad materials, as can be seen from the results of Examples No. 8-18 and No. 29-60 shown in Tables 2-4, the joint strength of material grades COM6 (A4-A11) and COM7 (A4-A5) is relatively low, and it can be easily determined from the test results in Tables 2-4 that joining by hot rolling is not easy.

[0068] COM6 (A4-A11) shows a small increase in joint strength with increasing reduction ratio (comparison of no. 55-57), and the joint strength only reaches 10 MPa or more when the reduction ratio exceeds 10%. COM7 (A4-A5) (compared to no. 58-60) shows low joint strength when the reduction ratio is small, but the rate of increase in joint strength with increasing reduction ratio is large, and the joint strength exceeds 10 MPa at a reduction ratio of about 8%. Therefore, it can be seen that the joint strength exceeds 10 MPa for all combinations when the reduction ratio is 10% or more.

[0069] Based on the bonding test results shown in Tables 2 to 4, a three-layer clad material was manufactured under the following conditions. While the plate thickness was more than 90% of the initial thickness, rolling was performed at a reduction rate of 5% or less per pass. This is because a reduction rate of 5% or less per pass allows for a gradual increase in joint strength without causing delamination. While the plate thickness was between 50% and 90% of the initial thickness, rolling was performed at a per-pass reduction ratio of 5.1% to 15%. As mentioned above, in the joint strength evaluation of this test, both COM5 (A4-A11) and COM6 (A4-A5) achieved a joint strength of 10 MPa or more when the reduction ratio was 10% or more (plate thickness was 90% or less of the initial thickness), and delamination did not occur even when the per-pass reduction ratio was increased to 5.1% or more. However, if the per-pass reduction ratio exceeds 15%, delamination is expected to occur due to the shear stress generated at the interface.

[0070] Since cladding problems such as joining do not occur when the plate thickness is less than 50% of the initial thickness, rolling was performed according to production convenience without specifying any conditions. As a result, the material was rolled successfully without significant displacement of the interface during rolling, and the desired three-layer clad material was obtained. Therefore, without having to conduct multiple costly prototypes with a material configuration that is difficult to join, we were able to successfully manufacture a three-layer clad material with good interlayer bonding properties, based on the results shown in Table 2. Ideally, the shear stress generated can be determined through numerical analysis, and by comparing it with the instantaneous joint stress, a more efficient path schedule can be selected. [Explanation of symbols]

[0071] 1, 2... Plate-shaped test specimen, 1A... First layer, 2A... Second layer, 3... Joint material of different types of aluminum, 4... Joint, 10... Intermediate test specimen, 11... Actual test specimen, 15... First joint piece, 16... Second joint piece, 17... Joint, 30... Test apparatus, 31... Lower clamping jig, 32... Upper clamping jig, 33... Support plate, 34... Support plate, 35... Lower clamping jig, 36... Upper clamping jig, 37, 38, 39, 40... Lubrication tape, 50... Hot compression device, 51... Lower die, 52... Punch, 53... Channel groove, 54... Protrusion.

Claims

1. A test specimen that is rectangular, circular, or elliptical in plan view and flat in shape, with a thickness of h and a length in the direction of the long side or the long axis direction of L. Ｌ , the aforementioned length L Ｌ The length in the short side direction or short axis direction is L. Ｓ When the lengths of the long side and short side are equal, or the lengths of the major axis and minor axis are equal, and the lengths of the side or diameter are denoted as L and S, then 0.13 ≤ h / L Ｓ Using test specimens made of pure aluminum or aluminum alloy with a coefficient of ≤0.54, Multiple test pieces having the shape of the test piece but made of pure aluminum or aluminum alloy with different compositions are stacked and heated to a desired temperature, and a compressive force is applied in the thickness direction to form a dissimilar aluminum joint material by joining the multiple test pieces. An intermediate test piece is cut from the dissimilar aluminum joint material so as to include the central part of the dissimilar aluminum joint material along one of the following cross-sections: a plurality of cross-sections parallel to the short side direction or short axis direction of the test piece and extending in the thickness direction of the test piece; a plurality of cross-sections parallel to the long side direction or long axis direction of the test piece and extending in the thickness direction of the test piece if the lengths of the long side and short side or the long axis and short axis are equal; and then an actual test piece for evaluating joint strength is cut from the intermediate test piece so as to include the central part of the intermediate test piece and along a plurality of cross-sections extending in the thickness direction of the intermediate test piece. A method for testing dissimilar aluminum joint materials, wherein the joint strength is evaluated by applying a shear force to the joint surface of the obtained test specimen.

2. The method for testing dissimilar aluminum joint materials according to claim 1, wherein the flat test piece is rectangular in plan view, and the compressive force is applied by a mold that applies the compressive force while constraining the deformation of the test piece in the direction of the long side.

3. The method for testing dissimilar aluminum joint materials according to claim 1 or claim 2, wherein the surface roughness Ra of the surfaces to be joined before joining in the test specimen is 0.01 μm or more and 30 μm or less.

4. A method for testing a dissimilar aluminum joint material according to any one of claims 1 to 3, wherein the reduction ratio when applying the compressive force in the thickness direction of the test piece to form the dissimilar aluminum joint material is 2% or more and 20% or less.

5. A method for testing dissimilar aluminum joint materials according to any one of claims 1 to 4, wherein at least one change is made from among changing the composition of a plurality of test pieces, changing the reduction ratio, and changing the heating temperature, the effect of the change on the test results of the joint strength is determined, and the dissimilar aluminum joint material is manufactured based on one or more conditions from among the composition, reduction ratio, and heating temperature that yielded good joint strength.

6. The method for manufacturing a dissimilar aluminum joint according to claim 5, wherein the dissimilar aluminum joint is a dissimilar aluminum joint having a two-layer to four-layer structure in which any two to four types of test pieces made of pure aluminum or aluminum alloy are joined, and at least one of the two to four types of test pieces is made of pure aluminum or aluminum alloy with a different composition from the other test pieces.

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