Chemical ordering induced elastic hardening and thermoelastic properties of β phase Mg1-xScx lightweight shape memory alloys

Abstract

The effect of chemical ordering on the thermoelastic properties of Mg-Sc light weight shape memory alloys are studied by the exact muffin-tinorbital method. Chemical ordering has significant hardening effect on elastic properties of Mg-Sc alloys, the C' is increased by 21% for Mg76Sc24 alloy, and the elastic hardening due to ordering can properly explain the increase in Vickers hardness observed in experiment. The quasi-harmonic Debye-Grüneisen model simulated the order–disorder transition temperature reasonably. The vibrational entropy increase due to elastic softening induced by disordering contributes considerably in driving the order–disorder transition. Mg-Sc alloys in ordered phase shows better thermoelastic stability over well-known commercial Mg alloys, therefore, ordering treatment of Mg-Sc are beneficial for structural application of this family of alloys. The Sc atoms (Mg atoms either) in bcc nearest neighboring lattice repel each other to form a B2-type ordered phase, and resultantly, the s-d and p-d hybridization between nearest neighboring Mg and Sc atoms is the main electronic reason for elastic hardening. The findings in current article not only give insight into understanding the strengthening mechanism during the ordering process of Mg-Sc alloys, but also provides a useful reference for the future development and modification of their shape memory effects.