Investigation on Fatigue Damage and Fracture of Al-5Zn-2Mg high strength Aluminum Alloy

摘要

The tensile properties and fatigue properties were tested, and the fatigue fracture and damage behaviore of Al-5Zn-2Mg high strength aluminum alloy was investigated by means of optical microscope (OM) and scanning electron microscope (SEM). The results show that the grain of the Al-5Zn-2Mg high strength aluminum alloy is elongated after rolling deformation. The tensile strength of the Al-5Zn-2Mg aluminum alloy is 470MPa. The fatigue life is 6.4×10~4 cycle in R=0.1, f=99Hz, and σ_(max)=210MPa. The average rate is 0.08μm per cycle from micro crack formed to 8mm of fatigue crack length. The fatigue crack forms in the surface. There are the fatigue striations in the fatigue crack propagation area. The crack velocity is about 2μm per cycle in propagation area. The damaged microstructure with the fatigue loading is loose, that indicates the micro cracks progressively emerge.