热循环、腐蚀和自然时效对2024铝合金搅拌摩擦焊接头力学性能的影响

Effects of Thermal Cycles,Corrosion,and Natural Aging on the Mechanical Properties of Friction Stir Welded Al2024 Joints

研究了焊接过程中热循环、焊后腐蚀和自然时效对2024铝合金搅拌摩擦焊(FSW)接头力学性能的影响。结果表明,同一焊缝不同位置的力学性能存在一定的差异,靠近插入点位置的屈服强度和抗拉强度明显低于其他位置,之后不断升高,趋于稳定,屈服强度和抗拉强度的最大值分别约为310 MPa和415 MPa;随着自然时效时间的增加,接头屈服强度和抗拉强度在前2个月增长较快,增长率最大分别为2%和1.5%,之后趋于稳定,而伸长率的增长率先较快,增长率最大为6%,之后变缓;在不同的自然时效时间下,腐蚀均明显降低2024铝合金FSW接头的屈服强度、抗拉强度和伸长率,减小率的最大值分别为6.5%,6.1%和19.8%;随着自然时效时间的增加,腐蚀后接头的力学性能下降更严重。

ABSTRACT:The influence of welding thermal cycle and the interaction of post-weld corrosion and natural aging on me-chanical properties of Al2024 joints welded by friction stir welding ( FSW) were studied. The results show that the mechan-ical properties at different positions of the same weld are different. The yield stress and ultimate tensile strength ( UTS) are lower in the starting position of the welded joint compared with other parts of the joint, and then they increase in the advan-cing direction of the stir tool, finally they keep stable at the last welding stage. The maximum values of yield stress and UTS are approximately 310 MPa and 415 MPa, respectively. The yield stress and UTS of the joints significantly increase during the first two months of natural aging and tend to be stable after that, the maximum values of growth rate are approxi-mately 2% and 1. 5%, respectively. While the elongation increases at first, and then is stable, the maximum growth rate of elongation is approximately 6%. After corrosion, the yield stress and UTS of joints are decreased at different natural ag-ing times as well as the elongation. The maximum values of reducing rate are approximately 6. 5%, 6. 1%, and 19. 8%, respectively. The tensile properties of Al 2024 joints after corrosion decrease with increasing the natural aging time.