Microstructural evolution and deformation mechanisms of an LPSO-containing Mg-Gd-Y-Zn-Zr alloy under pulsed current-assisted tension

Rare-earth magnesium alloys containing long-period stacking ordered (LPSO) phases are constrained by the hexagonal close-packed matrix, the LPSO phase, and the ability of the associated interfaces to accommodate strain, and therefore usually exhibit high deformation resistance and limited room-temperature plasticity. In this study, pulsed current-assisted tension was performed on an extruded Mg-Gd-Y-Zn-Zr alloy and compared with isothermal hot tension to clarify its plastic flow response, microstructural evolution, and deformation mechanisms under pulsed current loading. The results show that, at the same target temperature, pulsed current assistance further reduces the flow stress, indicating enhanced dynamic recovery and flow-softening tendency. EBSD analysis reveals that pulsed current reduces the intragranular orientation gradient, alleviates local stress concentration, suppresses the formation of intersecting twins, and makes the variant selection of {10−12} tensile twins more consistent with the Schmid-factor ranking. IGMA and TEM results further demonstrate that pyramidal <c + a> dislocations are more readily activated under pulsed current assistance, and that the associated lattice distortion can be continuously transmitted across the α-Mg/LPSO interface, indicating that the pulsed current promotes non-basal slip and interfacial strain accommodation. Multiphysics simulations show that the electrical-conductivity mismatch among the LPSO phase, grain boundaries, and α-Mg matrix induces local current concentration, thereby producing non-uniform Joule heating and an enhanced electron-wind effect near the interfaces. These results indicate that pulsed current induces flow softening and improves local deformation compatibility in the LPSO-containing Mg-Gd-Y-Zn-Zr alloy through the combined regulation of twinning behavior, promotion of non-basal slip, and enhancement of interfacial strain accommodation.