Superplasticity in A Zn-1·1 wt. % Al alloy

Abstract

In the paper the results of the deformation behaviour study in a fine-grained Zn-1·1 wt. % Al alloy are presented. The influence of strain rate ranging from 4·2×10⁻⁵ to 4·2×10⁻² s⁻¹ on the true stress — true strain curves, ductility and strain rate sensitivity was investigated at temperatures 295 K and 375 K. At both temperatures the superplastic behaviour was observed. The increase in temperature improved the superplastic properties and shifted the region of the superplastic behaviour to higher strain rates. The maximum values of ductilityA=700% and strain rate sensitivity parameter m=0·48 were established at 375 K at strain rates$\dot \varepsilon \cong 10^{ - 2} s^{ - 1}$. The true stress — true strain curves were found to be influenced by a grain growth taking place during the deformation. The grain growth was also found to be responsible for significant differences in the parameterm values obtained from the log${{\log \sigma } \mathord{\left/ {\vphantom {{\log \sigma } {\log \dot \varepsilon }}} \right. \kern-\nulldelimiterspace} {\log \dot \varepsilon }}$ plots and from the strain rat-changes.