喷射成形7055超高强铝合金锻件开裂原因

Cracking reasons of spray forming 7055 super high strength aluminum alloy forgings

某航空机轮用喷射成形7055超高强铝合金锻件在静压试验中提前开裂。结合锻件的热加工锻造工艺、热处理工艺和静压试验条件,采用宏观观察、电导率测试、力学性能测试、低倍组织检验、金相检验、断口及有限元模拟分析等方法,分析了锻件开裂的原因。结果表明:该锻件在静压试验中开裂的失效模式属于一次性的过载断裂;由于其定位孔较深、根部直角应力集中,在螺栓定位孔径根部萌生裂纹,尖角处机轮锻件流线对裂纹的形成与扩展有促进作用。减小定位孔深度、增加孔径根部圆弧过渡处圆角、优化热处理工艺可以有效地提升该锻件静压试验的失效强度,使其满足验收要求。

A spray forming 7055 ultra-high strength aluminum alloy forging for an aviation wheel product cracked early in the static pressure test.Combined with the hot working forging process,heat treatment process and static pressure test conditions of the forging,the cracking reasons of the forging were analyzed by means of macroscopic observation,electrical conductivity test,mechanical property test,metallographic examination,microstructure observation,fracture analysis and finite element simulation analysis.The results show that the failure mode of static pressure test cracking of the forging belonged to one-time overload fracture.Due to the deep positioning hole and the right angle stress concentration at the root of the forging,cracks initiated at the root of the bolt positioning hole,and the streamline of the wheel forging at the sharp corner promoted the formation and propagation of the cracks.The failure strength of the forging hydrostatic test could be effectively improved by reducing the depth of the positioning hole,increasing the fillet of the circular arc transition at the root of the hole,and optimizing the heat treatment process to meet the acceptance requirements.