固溶时效处理对不同状态7075铝合金搅拌摩擦焊接头组织和力学性能的影响

Influence of Solutionizing and Aging Treatment on the Microstructure and Mechanical Properties of AA7075 Friction Stir Welded Joints in Different Conditions

对于可热处理强化铝合金,焊后热处理是解决搅拌摩擦焊接头软化和提升力学性能常用的方法之一,对7075-T6与7075-O铝合金接头进行T6(固溶处理+人工时效)处理,研究T6处理对不同材料状态7075铝合金搅拌摩擦焊接头微观组织与力学性能的影响。结果表明,两种接头经T6处理后焊核区均出现不同程度的异常晶粒长大(Abnormal grain growth,AGG),且T6-T6接头AGG区域占比明显高于O-T6接头;力学性能实验表明,T6处理不仅能够有效解决焊态下的接头软化问题,而且能够提升接头整体硬度,两种接头平均硬度均在180 HV以上,其硬度分布均呈直线分布;AGG能够直接影响接头拉伸性能,O-T6接头强度与塑性均明显高于T6-T6接头,强度可达575.5 MPa,伸长率为7.1%。

For heat-treatable strengthened aluminum alloys,post-weld heat treatment stands out as a prevalent method to mitigate the softening of friction stir-welded joints and augment their mechanical characteristics.This investigation applies the T6 treatment(solution treatment and artificial aging)to joints formed from AA7075-T6 and AA7075-O,examining the impact of T6 treatment on the microstructure and mechanical properties of the joints.The findings reveal that both joints display varying degrees of abnormal grain growth(AGG)in the weld nugget zone,with the AGG area percentage notably higher in the T6-T6 joint as compared to the O-T6 joint.Concerning mechanical performance,the T6 treatment not only effectively resolves the softening issue in the welded state but also heightens the overall hardness of the joint.The average hardness consistently exceeds 180 HV,displaying a linear trend in hardness distribution.AGG significantly influences the tensile properties of the joints,wherein the O-T6 joint exhibits substantially greater strength and plasticity than the T6-T6 joint,achieving a strength of 575.5 MPa and an elongation of 7.1%.