Multidirectional compression and aging treatment overcoming the strength-ductility trade-off in ZK60 magnesium alloy

Severe plastic deformation (SPD) is widely regarded as an effective method to mitigate the strong anisotropy of magnesium alloys and significantly enhance their strength. However, SPD often leads to a substantial reduction in plasticity, which limits the simultaneous improvement of strength and plasticity. Achieving a balance between high strength and improved plasticity remains a critical scientific and technical challenge for the engineering applications of SPD magnesium alloys. In this context, the present study investigates the evolution mechanisms of microstructure and precipitation phase by introducing subsequent aging treatments at different temperatures (80°C, 120°C, 160°C, and 180°C) on ZK60 magnesium alloy pre-deformed by twelve passes of multidirectional compression. The study systematically explores the cooperative regulation of substructure and precipitate phases induced by pre-deformation. Using quasi-in-situ observation and texture characterization, the effects of second-phase precipitation and recrystallization mechanisms during aging on mechanical properties were analyzed. The results demonstrate that, within the aging temperature range of 120–180°C, a dense second phase preferentially precipitates along high-density twin boundaries and grain boundaries during aging, with precipitation prioritized over recrystallization. The uniformly dense second-phase precipitates at lower temperatures can enhance the strength of the material while maintaining high plasticity. Specifically, after aging for 10 hours at 120°C, the material achieves optimal strength-plasticity synergy, with yield strength, tensile strength, and elongation reaching 316.21 MPa, 437.73 MPa, and 18.12%, respectively, showing increases of 34.65%, 31.8%, and 11.37% compared to the as-received (AR) state. These results indicate that a well-designed SPD deformation path combined with low-temperature aging parameters can effectively activate the cooperative strengthening mechanism between deformation structures and precipitates, offering a promising and feasible approach to the fabrication of magnesium alloys with both high strength and high plasticity.