Study on the effect of room temperature cross-compression passes on the microstructure evolution and strengthening-toughening mechanism of ZK60 magnesium alloy

Magnesium alloys hold great promise for applications in the field of lightweight design, and the room-temperature multi-directional cross-compression (MDC) technique offers a novel approach to resolving the trade-off between strength and ductility. This study investigates hot-rolled ZK60 magnesium alloy sheets, subjecting them to 1, 2, 3, 6, and 12 passes of room-temperature MDC deformation. The evolution of the alloy’s microstructure, texture transformation, and local strain distribution were systematically investigated. As the number of compression passes increased, the twin plate layers gradually transformed from coarse, parallel distributions to fine, dense, and intersecting plate structures. At the same time, the strong basal-plane texture gradually weakens and shifts from a single ND orientation to a dispersed RD/ND orientation, significantly improving the asymmetry between tensile and compressive properties. Mechanical property test results indicate that as the number of MDC passes increases, the alloy’s strength and hardness improve significantly. Specifically, the 12MDC sample achieved yield and tensile strengths of 392.51 MPa and 489.93 MPa, respectively, representing increases of 67.18% and 37.44% compared to the AR sample; the 6MDC sample exhibited a more optimal strength-ductility balance, with yield strength, tensile strength, and elongation of 369.28 MPa, 465.91 MPa, and 17.40%, respectively. SEM-DIC results showed that as the number of compression passes increased, the degree of strain localization significantly decreased, and local plastic deformation tended to become more uniform. The strengthening after MDC treatment is mainly attributed to the combined effects of increased dislocation density and twin-boundary-induced grain refinement., while texture weakening and grain refinement help alleviate strain concentration, improve deformation coordination, and maintain plasticity. The 6MDC condition achieves the optimal balance between strengthening effects and plasticity retention.