Achieving excellent mechanical properties in Mg-Zn-Mn-Sn alloy via trace Sm and heat treatment process optimization

Developing cost-effective magnesium alloys with superior mechanical properties is critical for advancing large-scale industrial applications. This study presents a high-performance Mg-6Zn-1Mn-3Sn-xSm alloy fabricated through trace Sm addition and two-step aging optimization. Systematic investigations reveal that incremental Sm content refines the MgSnSm phase (reduced size, increased volume fraction). Through a tailored heat treatment process, the Mg-6Zn-1Mn-3Sn-0.5Sm alloy achieves exceptional strength with an ultimate tensile strength (UTS) of 418 MPa and a yield strength (YS) of 328 MPa. The MgSnSm phase has an orientation relationship with the β′ phase, which can act as a heterogeneous nucleation particle to promote the precipitation of the β′ phase during aging. Superior performance stems from the combined effects of the MgSnSm phase dispersion strengthening and high-density β’ precipitation hardening. This work provides a strategic pathway for designing high-strength magnesium alloys with minimal rare-earth (RE) additions.