An investigation of cavity growth in a superplastic aluminum alloy processed by ECAP

Quantitative measurements were taken to evaluate the significance of cavitation in the tensile testing of a superplastic spray-cast Al-7034 alloy processed by equal-channel angular pressing (ECAP). Samples were processed by ECAP and then tested in tension at 673 K using strain rates from 10-3 to 10-1 s-1. For comparison purposes, similar tensile testing was conducted also on samples without ECAP processing. Inspection of polished sections after tensile testing revealed extensive internal cavitation in all samples. Measurements were taken to provide detailed information on the sizes and shapes of the cavities and these measurements were analyzed to determine the dominant cavity growth mechanisms. The results demonstrate the importance of superplastic diffusion growth in ultrafine-grained materials processed by ECAP.