Dislocation Activity during Superplastic Flow in the Zn-22 Al Alloy

摘要

An investigation was conducted on the superplastic Zn-22% Al alloy that contained nanometer-scale dispersion particles, which were introduced into the microstructure by powder metallurgy. In the investigation, specimens were crept at a strain rate near the center of the superplastic region, which represents region II (the intermediate-stress region), in the sigmoidal plot between stress and strain rate that was reported for the alloy. Preliminary transmission electron microscopy (TEM) observations reveal evidence of lattice dislocation activity. This evidence is demonstrated by the presence of particle-dislocation interactions in the interiors of the grains of the alloy. The results are discussed with reference to various deformation mechanisms proposed for micrograin superplasticity.