Achieving strength-ductility synergy in rare earth Mg alloy via IMDF-induced texture weakening and LPSO phase tuning

Abstract

Magnesium alloys face the inherent challenge of the strength-ductility trade-off due to their limited room-temperature ductility and pronounced processing texture. To address this issue, this study employs isothermal multidirectional forging to synergistically regulate the basal texture and long-period stacking ordered phase in a Mg-7Y-2.5Zn-0.5Zr-0.1V alloy by introducing a dynamic multi-axial strain field. The microstructures, deformation mechanisms and room-temperature mechanical properties of the alloys processed by IMDF at different temperatures (370 °C, 420 °C and 470 °C) were systematically investigated. Results demonstrate that IMDF can significantly weaken the basal texture, optimize the morphology and distribution of the LPSO phase, and refine the grains simultaneously. The IMDF–420 alloy achieves an optimal balance of strength and ductility, with superior room-temperature tensile properties (YS: 335.6 MPa, EL: 27.2%). Its strengthening mechanisms include Hall-Petch strengthening from grain refinement, accumulation of GNDs and back-stress hardening induced by misorientation of grains, as well as the synergistic strengthening and toughening effects of multi-scale second phases (LPSO phase and short-range ordered (SRO) structure). In contrast, the excellent ductility originates from the combined activation of multi-slip systems induced by weak texture, grain refinement and dispersed LPSO phases. Specifically, the extensive activation of pyramidal ⟨c+a⟩ slip lays the foundation for macroscopic high ductility, while the twinning-slip transition, kinking and breaking of the LPSO phase, and intergranular slip transfer collectively form an efficient strain release system, which avoids severe strain localization and premature damage. This work provides important theoretical basis and process guidance for the design of high-performance magnesium alloys via multi-directional deformation processes.