Joining phenomena and tensile strength of friction welded joint between pure aluminum and pure copper

Abstract

This paper describes the joining phenomena and the tensile strength of friction welded joint between type 1070 pure aluminum (CP-Al) and oxygen free copper (OFC). When the joint was made at a friction pressure of 30 MPa with a friction speed of 27.5 s −1 , the upsetting (deformation) occurred at the CP-Al side. When the joint was made at a friction time of 2.0 s, the whole weld interface on the OFC side had the transferred CP-Al, and it was obtained approximately 30% joint efficiency. Then, the joint efficiency increased with increasing friction time, and it was obtained approximately 63% joint efficiency at a friction time of 12.0 s. The joint fractured at the weld interface, which had a CP-Al adhering to the weld interface on the OFC side. When the joint was made with friction times of 2.0 s and 6.0 s, the joint efficiency increased with increasing forge pressure and then the joint was obtained the CPAl side fracture at a forge pressure of 135 MPa or higher. However, the joint did not achieve 100% joint efficiency because the adjacent region of the weld interface at the CP-Al side was softened. In addition, the joint at a friction time of 2.0 s had no intermetallic compound (IMC) layer at the weld interface although the not-joined region was slightly observed. On the other hand, the joint at a friction time of 6.0 s did not have the not-joined region at the weld interface although the IMC layer was slightly observed. In conclusion, to obtain higher joint efficiency with fracture on the CP-Al side, the joint should be made with higher forge pressure, and with the suitable friction time at which the entire weld interface of the OFC side had the transferred CP-Al. IntroductionBecause an expansion in the use of dissimilar metal joints (referred to as dissimilar joints) is expected and widely used in various component parts, easily welding method for dissimilar metal joints is required. On the other hand, dissimilar welding operations have several severe problems in industrial usage. One problem will occur when the dissimilar joints are welded by using fusion welding processes which conventionally produce intermediate layer (interlayer) consisting of brittle intermetallic compound (IMC) at the joint interface of both base metals to be joined. The interlayers usually give detrimental damages on mechanical and metallurgical properties of dissimilar joints (For example, American Welding Society, 1982). In particular, fusion welded joints between aluminum or its alloys (referred to as the Al-system material) and copper or its alloys (referred to as the Cu-system material) have also some problems, e.g. the generation of blowholes and cracks at the joint interface (For example, Mizuno et al., 1999). Therefore, a welding process is urgently required, which will reduce the degradation of the mechanical and metallurgical properties of the joints between Al-system material and Cu-system material. 1

Effects of friction welding conditions on tensile strength of friction welded joint between 5052 Al alloy and pure copper

“…5. A similar mechanically mixed layer was also observed even in several friction welded joints for dissimilar materials combination as reported by many researchers (Ruge, et al, 1986;Yilmaz, et al, 1996;Fuwano, et al, 2000;Straffelini, et al, 2004;Meshram, et al, 2007;Arivazhagan, et al, 2008;Kimura, et al, 2011) in addition to CP-Al/OFC joint (Aritoshi, et al, 1991;Kimura, et al, 2015). Figure 8 shows the cross-sectional appearances of the weld interfaces of joints at various friction times.…”

“…Also, the friction torque maintained nearly constant from (4). The initial peak torque was approximately 13 Nm, and the elapsed time for the initial peak was about 1.4 s. The numerical values of the elapsed time for the initial peak were almost similar to those of CP-Al/OFC joint (Kimura, et al, 2015) at the same friction pressure, although the initial peak torque differed. Additionally, the joining behavior also resembled those with such another friction pressure as 20 or 60 MPa, although the change of the friction torque varied (data not shown due to space limitations).…”

“…This result resembled the transitional changes of the weld interface of the joint between Al-Zn-Mg alloy (JIS A7075) and OFC (Kimura, et al, 2003) as well as CP-Al/OFC joint (Kimura, et al, 2015) at the same friction pressure although the friction time differed. Additionally, the transitional changes of the weld interface also resembled those with such another friction pressure as 20 or 60 MPa, although the friction time was different.…”

“…7b). Hence, it is desirable to be set of an opportune friction time which generate less mechanically mixed layers of the joint because that layer will be affected to the joint strength (Aritoshi, et al, 1991;Kimura, et al, 2011Kimura, et al, , 2015 in addition to the IMC interlayer as reported by some researchers (Nakanishi, et al, 1976;Lee, et al, 2005;Chen, et al, 2006;Saeid, et al, 2010;Wei, et al, 2016). However, all joints fractured from the weld interface as shown in Fig.…”

“…In addition, the experimental methods of (2) and (3) were used to obtain the joint without braking deformation. The details of these methods were described in the previous report (Kimura, et al, 2015).…”