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

关键词:  激光焊|后热处理|7075Al|力学性能|断裂行为

Key words:  laser welding|post-heat-treatment|7075 aluminum alloy|mechanical properties|fracture behavior

摘要:

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.

Abstract:

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.