5083铝合金搅拌摩擦焊缝多区域力学性能研究

Study on Multi-Zone Mechanical Properties of Friction Stir Weld of 5083 Aluminum Alloy

对12 mm厚的5083铝合金双轴肩搅拌摩擦焊接头不同区域进行金相组织观察、拉伸试验、硬度测试和疲劳试验,对疲劳试验后的试样断口进行SEM观察。结果表明:焊核区晶粒明显细化,热影响区晶粒粗化,热机影响区晶粒发生严重变形并带有方向性。接头整体硬度近似呈非对称的“W”形分布。从母材到焊核区硬度先减小后增大。母材硬度值最高,焊核区次之。母材、焊核区、热影响区的疲劳寿命差别较大,母材疲劳性能最好,焊核区次之,热影响区最弱。各区的疲劳裂纹源位于疲劳试样的表面,扩展区中可以看到疲劳条带,瞬断区断裂形式均为韧性断裂。

Microstructure observation,tensile test,hardness test and fatigue test were carried out for different areas of the 12 mm thick 5083 aluminum alloy bobbin tool friction stir welding joint.The fracture of the specimens after fatigue test was observed by SEM.The results show that the grains in the weld nugget area are obviously refined,the grains in heat affected zone are coarsened,and the grains in heat-mechanical affected zone are severely deformed and have directionality.The overall hardness distribution of the joint is approximately asymmetric W-shaped.The hardness from the base metal to the weld nugget zone is first reduced and then increased.The hardness of the base metal is the highest,followed by the welding nugget zone.The fatigue life of the base metal,the weld nugget zone,and the heat affected zone are quite different.The fatigue performance of the base metal is the best,that of the weld nugget zone is the second,and that of the heat affected zone is the weakest.The source of fatigue cracks in each zone is generated on the surface of the fatigue specimen.Fatigue bands can be seen in the expansion zone,and the fracture mode of the instantaneous fracture zone is ductile fracture.