Enhancing Aluminum Alloy Brazing Joint Strength by Using Zn-Al-Cu Filler Metal

It is difficult to select a suitable filler for brazing of 6XXX series aluminum alloys due to their low solidus temperature. In this paper, five kinds of Zn-Al-Cu filler alloys were developed for high-frequency induction brazing of 6A02-T6 aluminum alloy. The nominal liquidus of filler metals ranges from 465.6 to 509.3 degrees C. The phase compositions of the filler metal are Al + Zn, CuAl2, CuZn4, and Al4.2Cu3.2Zn0.7. The results show that reliable joining of 6A02 aluminum alloy is achieved with novel Zn-Al-Cu filler metal under suitable processing parameters. A transition layer was formed at the brazing interface due to the interdiffusion of Zn and Al, which was the reason for metallurgical bonding. The addition of Cu to form intermetallic compounds was found to contribute to the improvement of joint strength. But too much Cu will increase the brittleness of the joint. The optimal composition of filler metal in this study is Zn-36Al-22.7Cu (wt.%). The maximum shear strength of the joint reached 101.3 MPa when brazing at 530 degrees C for 90 s with the Zn-36Al-22.7Cu (wt.%) filler metal.

Automated summary

Five kinds of Zn-Al-Cu filler alloys were developed for high-frequency induction brazing of 6A02-T6 aluminum alloy in this study. Reliable joining of 6A02 aluminum alloy was achieved with novel Zn-Al-Cu filler metal under suitable processing parameters. The optimal composition of filler metal in this study is Zn-36Al-22.7Cu (wt.%).