T6热处理与焊接顺序对A356铝合金搅拌摩擦焊接头组织和力学性能的影响

Effect of Sequence of T6 Heat Treatment and Welding on Microstructure and Mechanical Properties of Friction Stir Welding Joints of A356 Al Alloy

研究了A356铝合金在T6热处理后进行搅拌摩擦焊(T6-FSW)和搅拌摩擦焊后进行T6热处理(FSW-T6)2种不同工艺下的接头组织及力学性能。结果表明,T6-FSW接头的焊核区由细小的动态再结晶晶粒构成,但析出相发生溶解或粗化,接头横向拉伸时抗拉强度和延伸率分别为214 MPa和5.3%,平均硬度为76HV_(0.5),焊核区抗拉强度和延伸率分别为236 MPa和12.5%,接头冲击韧性为12.10 J;FSW-T6接头的焊核区发生异常晶粒长大,但具有高密度的细小析出相,接头横向拉伸的抗拉强度和延伸率分别为254 MPa和8.5%,平均硬度为96HV_(0.5),焊核区抗拉强度和延伸率分别为297 MPa和7.0%,接头冲击韧性为8.23 J。

The microstructure and mechanical properties of A356 aluminum alloy joints were studied after they were processed with technique of T6 heat treatment followed by friction stir welding(T6-FSW)and technique of friction stir welding followed by T6 heat treatment(FSW-T6)respectively.It is found that the nugget zone of T6-FSW joint is composed of dynamically recrystallized fine-grains,but the precipitates are dissolved or coarsened.The transverse tensile strength and elongation of T6-FSW joint are 214 MPa and 5.3%respectively,and an average hardness is 76HV_(0.5).The tensile strength and elongation of the nugget zone are 236 MPa and 12.5%respectively,and the impact toughness of the joint is 12.10 J.Abnormal grain growth occurs in the nugget zone of FSW-T6 joint,where fine precipitates with high density are formed.The transverse tensile strength and elongation of FSW-T6 joint are 254 MPa and 8.5%respectively,and an average hardness is 96HV_(0.5).The tensile strength and elongation of the nugget zone are 297 MPa and 7.0%respectively,and the impact toughness of the joint is 8.23 J.