Effect of induced screw twisted strain on the twin orientation regulation and the ductility of pre-twined ZM21 Mg alloys

Abstract

A novel twist strain-induced twin orientation regulation (TITOR) has been developed to modify the basal texture of Mg alloys. Firstly, the {10–12} tensile twins are pre-set by pre-compression on the ZM21 Mg alloy along the extrusion direction (ED), and then the TITOR process is adjusted to regulate the twins’ orientation. The results show that the orientation of some twins deviated by 30° from the ED direction to the transverse direction (TD) direction after introducing twist strain. The introduction of multiple passes of twist strain will result in almost all grains transforming into dynamic recrystallization (DRX) grains. And the generation of DRX behavior will be updating the microstructure. The mechanism in the TITOR process is continuous dynamic recrystallization (CDRX), which does not alter the orientation of the grains. When the PT samples undergo multiple passes TITOR treatments, the orientation of the DRX grains shifts towards the twisted plane (grain c-axis deviates by ∼ 30° from ED to TD direction). The formation of twist texture results in a larger value of SF, which is beneficial for the basal slip. Compared with the extruded Mg alloys, the TITOR-8P sample fracture elongation (FE) has been increased from 14.3 % to 30.6 % due to the promotion of basal slip activities and grain refinement. The ultimate tensile strength (UTS) has been increased from 243.5 MPa to 375.5 MPa. The newly proposed TITOR scheme is of great significance for promoting the application of Mg alloys.