AA6082铝合金搅拌摩擦焊接头疲劳扩展速率

Fatigue crack growth rate in friction stir welded joint of AA6082 alloy

研究了6082-T6铝合金搅拌摩擦焊接头不同位置的疲劳裂纹扩展速率,并分析了接头的组织及疲劳断口形貌。试验结果表明,疲劳裂纹扩展速率最快的区域为接头焊核细晶区;当裂纹在热影响区扩展时,在较小的应力强度因子范围(ΔK)条件下,裂纹的扩展速率低于其在母材中的扩展速率,伴随着ΔK的逐渐增加,裂纹的扩展速率明显加快并高于其在母材中的扩展速率。断口形貌表明,疲劳裂纹在焊核区扩展主要由脆性的准解理断裂形貌组成,扩展速率较快;而热影响区及母材区的断口形貌主要由光滑的疲劳条纹组成。

Fatigue crack growth rates( FCWR) at different locations in FSWed joint of A6082 alloy were investigated. The microstructures and fatigue fracture morphology were analyzed. The results showed that the highest FCWR appears in the nugget zone. At lower ΔK range,the FCPR in heat affected zone is lower than that in base metal. At higher ΔK range,the FCPR in the heat affected zone increases,which is higher than that in base metal. The fatigue fracture showed that fatigue crack propagates in the nugget zone in the form of brittle quasi-cleavage mode,the resistance of fatigue crack propagation was reduced. While the typical plastic fatigue striation was the fracture mode of crack propagated in the heat affected zone and base metal.