The Effect of Solute Distribution on Creep Fracture in a Ni Alloy

Creep cavitation is a heterogeneous process. Thus, cavities coalesce locally to form microcracks long before final fracture. This process has been studied in a Ni-1% Sn alloy whereby macrosegregation of the tin during casting produces an inhomogeneous distribution of cavities and microcracks. The result is an increase in both strength and ductility, as compared to the same alloy with a homogeneous distribution of solute. This is because, while cavities and microcracks form readily in the Sn-rich regions, failure requires the propagation of cracks through regions with low Sn content where the creep ductility is high.