Grain boundary sliding and accommodation mechanisms during superplastic deformation of ZK40 alloy processed by ECAP

Controlling mechanism during superplastic deformation of ZK40 alloy processed by ECAP was identified. Effects of twinning and dynamic strain ageing (DSA) on superplasticity were analyzed. Amplitude in stress oscillation was correlated with solute atom concentration theoretically. Twinning can be an enhancing factor in grain boundary sliding and DSA had apparent influence on stress fluctuation; they were accommodation mechanisms for superplastic deformation through grain reorientation and interaction between solute atoms and dislocations, respectively. The interaction between mobile and forest dislocations played a dominant role for the occurrence of DSA, when dislocation density was relatively low in large grains. The effect of DSA became more active with increasing temperature, although grain boundary sliding (GBS) was the controlling mechanism throughout the whole process of superplastic deformation under elevated temperatures. (c) 2006 Springer Science + Business Media, Inc.