Optimizing the mechanical properties of a Mg–Y–Nd–Zn–Zr alloy via interrupted compression with an intermediate annealing

Abstract

This work proposed a practical method, interrupted compression with an intermediate annealing, for optimizing the mechanical properties of Mg–4Y-2Nd-0.2Zn-0.5Zr alloy. This method contained the first compressive step for an interrupted strain of 0.25, the intermediate annealing for 5 min, and the second compressive step for a total true strain of 1.6. The temperatures for the two steps of hot compression and intermediate annealing were the same. The obtained sample was named IC sample. As a comparison, the continuous compression was also performed (CC sample). During hot compression, the work softening of the CC sample was dominated by the rotational dynamic recrystallization (rDRX) and the twin-assisted DRX (tDRX). With the strain increasing, the rDRX acted a more dominant role compared to the tDRX. In the IC sample, the intermediate annealing triggered the formation of deformation bands. During the second compressive step of the IC sample, the work softening was dominated by the DRX assisted by deformation bands besides the rDRX. As a result, the volume fraction of ultra-fine grains (V UFG ) was much higher in comparison to the CC sample. Compared to the grain size of UFGs (D UFG ) and the basal pole distribution, the V UFG had a more important role in the resultant mechanical properties. The higher V UFG of the IC sample led to the better combination of strength and ductility at each compressive temperature. Comparing the IC sample to the CC sample after compressing at temperatures from 420 °C to 510 °C, the increments of the UTS were 7.4%, 2.4%, 1.2% and 0.4%, and the increments of the FE were 4.0%, 13.9%, 22.8% and 21.3%. The interrupted compression with an intermediate annealing had a deep potential in applying to other Mg alloys despite the initial texture. • Both continuous compression (CC) and interrupted compression (IC) are performed. • In CC sample, work softening is controlled by both rDRX and tDRX. • Intermediate annealing triggers the formation of deformation bands in IC sample. • In IC sample, work softening is dominated by the DRX assisted by deformation bands. • Interrupted compression successfully improves DRX degree and mechanical properties.