Ternary Mg-Sc-based TRIP alloys: Design strategy based on Sc-equivalent

Abstract

This study addresses the transformation-induced plasticity (TRIP) effect observed in bcc single-phase Mg–Sc alloys, aiming to circumvent the strength-ductility tradeoff inherent in traditional Mg-based alloys. Introducing a third element (X = Zn, Y, Nd, Gd) significantly enhanced the strength of the binary Mg–Sc TRIP alloys, simultaneously preserving ductility due to the TRIP effect. Consequently, a ternary Mg–Sc–X TRIP alloy with a bcc single-phase, for instance, achieved an ultimate tensile strength of approximately 380 MPa and a fracture elongation of around 41%, surpassing the conventional tradeoff. Furthermore, we introduce the design strategy of Sc-equivalent (Sceq) to articulate the combined influence of Sc and X elements on the stability of the bcc phase. This novel approach demonstrates the room-temperature deformation behavior of the Mg–Sc–X ternary alloy can be predicted and modulated, showcasing superelasticity (17.5 < Sceq < 19.5) and TRIP effect (19.0 < Sceq < 21.0).