后热处理对激光焊接7075铝合金显微组织与力学性能影响

Effect of post-weld heat treatment on microstructure and mechanical properties of laser welded 7075Al alloy

采用激光自熔焊接技术制备7075高强铝合金接头,研究了后热处理对接头显微组织与拉伸性能的影响.采用SEM与EBSD系统表征了后热处理对7075Al接头显微组织演变与拉伸断裂行为的影响.结果表明,焊缝中心到母材依次存在等轴晶区域、柱状晶区域、胞状晶区域与母材轧制态区域,并且胞状晶区域与等轴晶区域为接头薄弱区域.与未后热处理接头相比,后热处理接头平均抗拉强度达到475 MPa,同比提升约59%.后热处理构筑的纳米沉淀相触发了第二相强化机制,这是提升接头抗拉强度的主要因素.

7075 high-strength aluminum alloy joints were prepared by laser self-fusion welding technology, and the effect of post-heat treatment on the microstructure and tensile properties of the joints was studied. The microstructure evolution and tensile fracture behavior of 7075 joints after post-heat treatment were characterized by SEM and EBSD systems. The results show that there are equiaxed grain regions, columnar grain regions, cellular grain regions and base metal as-rolled regions from the center of the weld to the base metal. The cellular and equiaxed grain regions are weak areas of the joint.Compared with the unheat-treated joint, the average tensile strength of the post-heat-treated joint reached 475 MPa, an increase of about 59%. The nano-precipitated phase constructed by the post-heat treatment triggered the second-phase strengthening mechanism, which was the main factor to improve the tensile strength of the joint.