Stress‐Induced Microcracking at Second‐Phase Inclusions

The critical inclusion size for microcracking due to an applied stress for an inclusion that has a residual stress field is estimated using fracture mechanics. In particular, an analysis is presented for both circumferential and radial crack formation at spherical inclusions that have a uniform misfit strain compared to the matrix. It is found that the critical size can be greatly reduced below that for spontaneous microcracking when the applied stress is of the order of the residual stress. It was predicted that the applied stress would cause extensive micro‐cracking when the local fracture toughness is low and when the size of the inclusions approaches the critical size for spontaneous microcracking.