Effect of Surface Coarse Grain on Fatigue Property of 7A04 Aluminum Alloy

Surface coarse grain structure occurs during thermal process of high strength aluminum alloy. There are different mechanical properties between surface coarse and internal grain structure, which would affect the service performance. In this paper, sample including surface coarse grain is prepared from 7A04 aluminum forgings. The fatigue properties of the both grain size sample are studied through the four-point bending fatigue test, and the results show that surface coarse grain structure reduces the resistance of persistent slip bands those lead to fatigue crack more easily in the surface coarse grain structure and reduce the fatigue property.