Formation and microstructure of shear bands during hot rolling of a Mg–6Zn–0.5Zr alloy plate with a basal texture

Abstract

A Mg–6Zn–0.5Zr alloy (ZK60) plate with a strong basal texture was rolled at 400°C to reductions of 9–48%. Microstructure and texture of the hot-rolled plates were systematically studied with the aim to disclose the formation mechanism of shear bands during hot rolling. Our results show that dynamic recrystallization (DRX) prefers to occur at grain boundaries in a large amount at low rolling reductions. With increasing reductions, the DRXed regions cluster and widen by consumption of the parent grains. Finally, large shear bands appear in the form of symmetric pairs, inclining at an angle of±40° from the rolling direction (RD). Both equiaxed and elongated DRXed grains in submicron scale exist in the shear bands. Deformation twins mainly appear in the regions outside of the shear bands. Both micron-scaled and submicron-scaled {101¯1} contraction twins or {101¯1}-{101¯2} double twins are detected. It seems that those deformation twins do not play an important role in the formation of shear bands during hot-rolling at 400°C. The DRXed grains in the vicinity of grain boundaries have similar orientations to that of their parent grains, while basal poles of the DRXed grains in double twins greatly incline from that of their parent twins. The hot rolling results in scattering of basal poles toward the transverse direction (TD). The maximum intensity of basal poles varies with rolling reductions.