The effect of multi-coupling of LPSO, γ'', and γ′ phases on the microstructural evolution and mechanical properties of Mg-Y-Ni alloys

Abstract

This study utilized powder metallurgy to prepare Mg-10Y-(0, 0.5, 1, 1.5) wt.% Ni alloys systematically investigated the grain size, precipitate characteristics, mechanical properties, and strengthening-toughening mechanisms. The results show that with increasing Ni content, the volume fraction of long-period stacking ordered (LPSO) phases in MgY-1.5Ni alloy increased to 15 %, accompanied by forming γ'' and γ′ phases. The multiphase coupling inhibited excessive grain growth during recrystallization and contributed to refining the grain size of the Mg-Y-Ni alloy. In particular, the extruded MgY-1.5 Ni alloy exhibited a significantly refined grain size of 670 nm, with tensile strength, yield strength, and elongation reaching 371 ± 1.5 MPa, 383 ± 6.9 MPa, and 14.5 ± 0.2 %, respectively, representing improvements of 46.6 %, 20.3 %, and 55.9 % compared to the Mg-10Y base alloy. The strength enhancement is attributed to kinking strengthening from LPSO phases and the hindrance of dislocation motion by γ'' and γ′ phases. The improvement in ductility is attributed to grain refinement and the activation of non-basal slip systems by LPSO phases. This study provides a theoretical basis for researching and applying Mg-RE alloys containing LPSO phases.