The effect of porosity on the fatigue life of cast aluminium-silicon alloys

Fatigue strength optimization of cast aluminium alloys requires an understanding of the role of micropores resulting from the casting process. High cycle fatigue tests conducted on cast A356-T6 show that the pore size and proximity to the specimen surface significantly influence fatigue crack initiation. This is supported by finite element analyses (both elastic and elastic-plastic) which demonstrate that high stress/strain concentration is induced by pores which are both large and near to the specimen surface. A new pore-sensitive model based on a modified stress-life approach has been developed which correlates fatigue life with the size of the failure-dominant pore. The model prediction is in good agreement with experimental data.