6061铝合金FSW焊缝时效组织与力学性能研究

Microstructure and Mechanical Properties of 6061 Aluminum Alloy Weld by Friction Stir Welding

研究了6061铝合金搅拌摩擦焊接(FSW)焊缝单级时效和二级时效处理后组织与力学性能变化,结果表明:6061铝合金FSW焊缝固溶后自然时效处理,硬度为52HV,抗拉强度200 MPa;6061铝合金FSW焊缝固溶后再经(180℃×6 h)单级峰时效(T6态),硬度为93HV,抗拉强度为320 MPa,伸长率为12%;6061铝合金FSW焊缝经120℃×4 h+180℃×4 h二级峰时效处理后,硬度为112HV,抗拉强度为375 MPa,伸长率为11%。二级峰时效的试样组织中出现了条絮状析出相,并与针状析出相发生缠结,对位错移动产生阻碍,这是铝合金FSW焊缝经二级峰时效后强度和硬度比单级峰时效更高的重要原因。

After two groups of 6061 aluminum alloy were processed by friction stir welding(FSW)and then treated by single-stage aging and two-stage aging,the variation in the microstructure and mechanical properties of welds was investigated.The results show that after being treated by FSW and aged at room temperature,the 6061 aluminum alloy weld can have the hardness of 52HV and tensile strength of 200 MPa.After being treated by FSW and then subjected to single-stage aging at 180℃for 6 h,6061 aluminum alloy weld can have the hardness of 93HV,tensile strength of 320 MPa and elongation of 12%;while being treated by FSW and then subjected to two-stage aging at 120℃for 4 h and 180℃for 4 h,the 6061 aluminum alloy weld can have the hardness of 112HV,tensile strength of 375 MPa and elongation of 11%.The flocculent precipitates are found in the microstructure of the specimens after two-stage peak aging treatment,which entangles with the needle precipitates and can hinder the dislocation movement.This is the important reason why the strength and hardness of aluminum alloy weld of FSW after two-stage aging are higher compared with that after single-stage aging.