Investigation of slip systems activity and grain boundary sliding in fine-grained superplastic zinc alloy

Abstract

Zn alloys are desirable candidates for biodegradable materials due to their great biocompatibility and sufficient mechanical properties. Nevertheless, the most popular strengthening method by grain refinement after cold processing is usually ineffective in Zn alloys. Besides highly anisotropic deformation through a dislocation slip, grain boundary sliding (GBS) plays an important role in total deformation in fine-grained Zn alloys at room temperature (RT). Herein, Zn–0.5Cu (wt. %) alloy is fabricated by RT equal channel angular pressing, and its deformation mechanisms in tension were systematically analyzed at strain rates from 10–4 s−1 to 100 s−1. GBS contribution in total deformation was measured using surface markers and atomic force microscopy. In addition, dislocation slip activity was evaluated via electron-backscattered diffraction-based slip trace analysis. As a result, investigated alloy presents the GBS contribution in a total deformation at RT from 35% at the strain rate 100 s−1 to 70% at 10–4 s−1. Simultaneously, the number of slip-deformed grains decreased from 97.5% to 8%. Moreover, the basal slip system was dominant at all strain rates, while the prismatic and the pyramidal < c + a > slip systems were activated at the higher strain rates. The results presented here for the first time clearly show the complexity of deformation mechanisms in fine-grained Zn–0.5Cu, at significantly different strain rate conditions.