Cavitation damage in the superplastic Zn-22% Al-0.5% Cu alloy

A quantitative analysis of cavitation damage in a superplastic ZnAl alloy has been made, and results contrasted with theoretical models. Metallography indicates that cavities nucleate in Fe-rich particles and that fracture occurs at relatively low cavitation levels (6-12%) after local strains of about 6.5. The level of damage at any given strain is higher while cavities are larger and more round the lower the deformation rate. Experimental data can be reasonably fitted to mechanistic models for cavity growth assuming coupling between boundary diffusion and matrix plasticity as the mechanism of growth, if grain growth hardening and an enhancement of the diffusive contribution to growth due to the very small grain size are taken into account