Shape Memory Properties Of Mg-Sc Alloy

Mg alloys have been attracting attention for next generation structural materials as the most light weight practical alloys with a low density of below 2 g/cm³. However, conventional Mg alloys have been used still only in a limited field because of their poor formability, which arises from the anisotropic hcp structure. Among Mg-X systems, only Mg-Li and Mg-Sc alloys have a bcc structure which is an isotropic structure in a Mg rich composition. Mg-Li alloys with bcc phase has already been reported to show a good formability. Thus, the utilization of bcc phase is a good way to improve the formability of Mg alloys. Our group has been focusing on Mg-Sc alloy. In Mg-Sc binary phase diagram, bcc and hcp two-phase boundary shifts towards higher Mg contents with increasing temperature, while the phase boundary almost vertical up to a high temperature in Mg-Li system. Therefore, in Mg-Sc alloy, microstructure can be easily controlled by changing temperatures. We have demonstrated that Mg-Sc alloy with bcc/hcp two-phase shows much a good valance of strength and elongation than conventional Mg alloys. Furthermore, recently, we found that a metastable bcc Mg-Sc alloy with a density of just 2 g/cm³ shows a superelasticity at low temperature [*]. This is a first report on the shape memory behavior in lightweight magnesium alloys.

In this presentation, we will discuss about the relationship between shape memory properties and testing temperature and also the martensitic transformation in bcc-type Mg-Sc alloy.

[*] Y. Ogawa et al., Science, 353 (2016) 368-370.