Atomistic insights into structural ordering effects on martensitic transformations in Mg-Sc shape memory alloys

초록

Mg-Sc shape memory alloys exhibit exceptionally low density but suffer from very low transformation temperatures. Here, we combine first-principles calculations, phonon analysis, molecular dynamics simulations, and hybrid Monte Carlo/molecular dynamics to uncover the atomic-scale mechanisms governing phase transformations in Mg-Sc alloys. Our results reveal that partial atomic ordering is essential for reversible martensitic transformations, with partially ordered B2 austenite and B19 martensite structures being thermodynamically favored over their disordered counterparts across compositions of 15-25 at.% Sc. This ordered transformation pathway exhibits remarkable composition sensitivity: reducing Sc content progressively stabilizes martensite relative to austenite, driving increases in the transformation temperature consistent with reported experimental trends. This comprehensive atomistic understanding provides a clear strategy for developing ambienttemperature lightweight SMAs through compositional optimization and controlled ordering.

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