Fatigue of a sintered 2xxx series alloy

Fatigue of a sintered 2xxx series aluminium alloy has been investigated using a three point bend test and a stress ratio, R, of 0.1. Fatigue cracks invariably initiated at pores. Pore size measurements, in conjunction with fracture mechanics theory, were used to analyse the effects of density and initiating pore size. The fatigue life is inversely proportional to σ4ai, where σ is the stress amplitude and ai is the equivalent circle diameter of the fatigue initiating pore. Three distinct crack growth regions were observed on the fracture surface. Early crack propagation was transgranular, with a transition to an intergranular mechanism when the size of the cyclic plastic zone preceding the crack became comparable to the grain size. The third region was associated with final, fast fracture