Microstructure and Mechanical Properties of 6061 Al/AZ31 Mg Joints Friction Stir Lap Welded by a Tool with Variable-Pitch Thread Pin

Metals

Zhiqiang Zhang¹  Chengpeng Qiu¹  Hao Zhang¹  Gaowu Qin¹  Ni Tian¹  Changshu He¹  Jingxun Wei¹ 

[1] School of Materials Science and Engineering, Northeastern University, Shenyang 110819, China;

关键词: friction stir lap welding;    variable-pitch thread pin;    dissimilar metals;    metal flow;    intermetallic compounds;   

DOI  :  10.3390/met11010034

来源: DOAJ

【 摘 要 】

Sheets of 6061-T6 aluminum alloy (thickness = 3 mm) and AZ31 magnesium alloy were friction stir lap welded by a tool with a variable-pitch thread pin (coarse-threaded in the upper part and fine-threaded in the lower part). For the same rotation speed and welding speed, the heat input was higher in joints with an upper Al alloy (Configuration Al-Mg) than in those with an upper Mg alloy (Configuration Mg-Al). In Configuration Al-Mg, these two dissimilar metals were poorly mixed and Al dominated the stirred zone (SZ). Many intermetallic compounds (IMCs) of Al₃Mg₂ formed inside the SZ. In Configuration Mg-Al, Mg alloy bands, flocculent Al₁₂Mg₁₇ bands, and minor Al alloy bands intersected in the SZ, forming a complex onion-ring structure. Moreover, a complex mechanical interlocking structure developed at the bottom interface of the SZ. The maximum tensile shear strengths of the Al-Mg and Mg-Al lap configurations were 160.3 and 217 N/mm, respectively, at 700 rpm. The higher tensile shear strength of the Mg-Al configuration primarily represented less IMCs and complex mechanical interlocking structures in the SZ.

【 授权许可】

Unknown