两种焊后处理工艺对铝合金焊接头力学性能的影响

Effects of two post-weld treatments on mechanical properties of aluminum alloy welded joint

研究激光冲击处理(LSP)和固溶-时效两种焊后处理工艺对7075铝合金等离子弧焊接头微观组织和力学性能的影响规律。通过固溶-时效处理工艺优化设计,确定焊接头的最佳热处理工艺为固溶(575℃,2 h)、时效(140℃,2 h),并与激光冲击处理工艺进行了对比。结果表明:焊接头经2次激光冲击后,表层焊缝区的显微硬度提高23.3%,残余应力由拉应力9 MPa变为压应力23 MPa;在热影响区,显微硬度提高44.4%,残余应力提高42.8%,抗拉强度达到607.89 MPa,与未处理样品相比提高61.96%;固溶-时效在硬度的影响层深度、断面收缩率方面优于激光冲击,而激光冲击导致裂纹源萌生于次表层,提高了焊接头的抗拉性能。

The effects of laser shock peening（LSP） and solution and aging treatment on the microstructure and mechanical properties of plasma arc welded joints of 7075 aluminum alloy were studied.The process of the solution and aging treatment was optimized and the optimum process was selected as solid solution treated at （575 ℃,2 h） and aged at （140 ℃,2 h）.Then the effect of solution and aging treatment was compared with that of LSP.The results show that,in the weld zone of crown surface,the microhardness of welded joint with LSP 2 times is increased by 23.3%,and the residual stress is changed from tensile stress of 9 MPa to compressive stress of 23 MPa;in the heat affected zone,the microhardness is increased by 44,4%,the residual compressive stress is improved by 42.8%,the tensile strength is enhanced to 607.89 MPa,increased by 61.96% compared with untreated;the solution and aging treatment process is better than LSP on the depth of influence and the contraction ratio of section.While LSP makes the cracks mainly initiate at the subsurface thus improves the tensile strength of 7075 aluminum alloy resultant joint.