Enhancing strength and ductility of low-cost rare earth Mg-5Y-Ni alloy containing LPSO phase fabricated via multi-pass rolling based on dislocation regulation and grain refinement

Abstract

A low-cost rare earth Mg-5Y-Ni alloy containing LPSO phase was fabricated via multi-pass rolling in this work, and strength and ductility were enhanced based on dislocation regulation and grain refinement at various rolling temperatures. The alloy was designed to contain about 9.6% lamellar 18R-LPSO phase after homogenization. All alloys were completely recrystallized after rolling, and the alloy rolled at 450 °C (450R) achieved the finest recrystallized grains with an average size of 3.97 μm. The {0002} basal texture intensity decreased and average Schmid factors of non-basal slips increase with increasing rolling temperature. 450R alloy exhibits the highest strength and that rolled at 500 °C (500R) exhibits the best strength-ductility synergy and work hardening capability. Accumulation of dislocations and stacking faults promotes uniform and complete recrystallization. Dislocation and grain refinement strengthening effects provide most strength increments. High-density dislocations promote dynamic recovery process during tensile deformation and results in a rapidly decrease in stage I and a low level in stage III of work hardening rates. Grain refinement induced by dislocation accumulation, dynamic recovery process promoted by high-density dislocations and high dislocation activity of non-basal slips improve the ductility. This work illustrates the feasibility of dislocation regulation to synergistically enhance the strength and ductility of Mg alloys.