Dynamic recrystallization of pure zinc during high strain-rate compression at ambient temperature

Due to limited slip systems, forming of Zn-based alloys is typically conducted at elevated temperatures which consumes energy and may degrade mechanical properties. The present study aims to investigate feasibility for processing of Zn-based alloys at relatively low or even ambient temperatures by developing fundamental understanding that can be applied to control dynamic recrystallization during forming. An as-cast pure zinc was compressed to various strains at a strain rate of 0.5 s(-1) under ambient temperature and the microstructures were studied by electron backscattered diffraction to gain insight into the microstructural evolution and dynamic recrystallization behaviours. Significantly, Zn remained intact up to very high true strains, above 161%, and the corresponding true stress-strain curve did not exhibit steady-state deformation behaviour. Extensive continuous and twin-induced dynamic recrystallization were revealed to effectively accommodate plastic strains and relieve local stress concentrations leading to this extraordinary plasticity. A strong dependence of basal slip and {101 square 2} compression twinning on the grain orientation resulted in remnant coarse-grained domains in the otherwise heavily refined deformation microstructures. Strain partitioning at large strains is proposed to lead to continuous reductions in the true stress beyond the peak and bimodal texture in the final microstructure.