Fatigue-Crack Initiation and Propagation in Iron and Iron–Silicon Alloys

Abstract

Fatigue-crack initiation and propagation has been studied by both optical and scanning electron metallography in a series of polycrystalline irons and iron–silicon alloys fatigued in reverse-plane bending. The role of extremely small amounts of oxygen in promoting intergranular weakness in unidirectionally deformed iron is enhanced by the application of an alternating stress. Addition of silicon to iron results in a transition from intergranular to transgranular fatigue cracking of the type commonly associated with f.c.c. materials.