Influence of hot rolling strategies on the microstructure and mechanical properties of a twin-roll cast WZ73 alloy

Abstract The effects of rolling temperature, intermediate heat treatment, equivalent strain, equivalent strain rate, and number of passes on the microstructure and mechanical properties of Mg alloys containing block-shaped long period stacking ordered (LPSO) phases were systematically investigated. Hot rolling at 500 °C and 520 °C produced predominantly recrystallized microstructures, with higher temperatures increasing the dynamic recrystallized (DRX) fraction (from 89% to 94%) and reducing grain size (11 μm to 10 μm). Block-shaped LPSO phases at higher temperatures promoted particle-stimulated nucleation (PSN), while lamellar LPSO at lower temperatures exerted a pinning effect. Single-pass high equivalent strain deformation ( $$\:{\varphi\:}_{\text{v}}$$ = 0.97, $$\:{\dot{\varphi\:}}_{\text{v}}$$ = 70 s⁻¹) yielded fine, homogeneous grains (1 μm) with extensive DRX and 25% LPSO fraction. Intermediate heat treatments influenced LPSO dissolution and reprecipitation, with longer holding times enhancing ultimate tensile strength (UTS) and ductility through higher DRX fractions and PSN effects. Multi-pass rolling partially suppressed DRX at lower equivalent strains but refined grains at higher equivalent strains, with fragmented LPSO phases facilitating DRX and lamellar phases potentially delaying it through kinking. Mechanical testing revealed that the yield tensile strength (YTS) is mainly influenced by the number of rolling passes and the equivalent strain distribution, while UTS and elongation at fracture (A) were sensitive to all the investigated parameters and the corresponding microstructural evolution. These results demonstrate that careful control of rolling temperature, equivalent strain path, and intermediate heat treatment enables optimization of the strength – ductility balance in LPSO-containing Mg alloys.