Effects of initial grain size and orientation on the twin behavior in ZK60 Mg alloy

Abstract

To investigate the microstructures evolution of the hot-extruded Mg-5.1 wt% Zn-0.18 wt% Zr alloy (denoted as ZK60) fabricated via powder metallurgy route and to reveal the deformation mechanism, the microstructures of the ZK60 alloy hot-extruded at 623 K (denoted as 623 K ZK60), the ZK60 alloy hot-extruded at 673 K (denoted as 673 K ZK60) and the ZK60 alloy hot-extruded at 623 K subsequent compressed by 2% was analyzed and compared. It was find that the microstructure and texture of the 623 K ZK60 alloy subsequent compressed by 2% at room temperature were similar to the initial microstructure and texture of the 673 K ZK60. In addition, the twinning process was delayed before the yield points (σ0.2) by initial grain size and strong pyramidal preferred orientation in both the tensile and compressive tests. Compared with the 673 K ZK60 alloy, the 623 K ZK60 alloy with bimodal-grained structure (BGS) showed stronger strength, better ductility and lower tensile/compressive yield asymmetries compared with the FG samples due to the twinning suppressed in the BGS before the yield points.