Surface tension determination of liquid ternary and sub-binary alloys in Mg–Al–RE (RE = La, Ce, Nd, Gd, Y) system

The surface tension of rare earth-magnesium alloys significantly influences its castability and mould-filling behaviour, whereas experimental measurements of such thermophysical properties remain challenging. In this study, the surface tension of liquid ternary and Sub-binary alloys in Mg–Al–RE (La, Ce, Nd, Gd, Y) system was determined by Butler equation combined with the thermodynamic parameters calculated by General Solution Model (GSM). The influence of temperature and composition on surface tension was studied systematically. The surface tension of magnesium alloy melts exhibits a strong negative temperature dependence, decreasing significantly with increasing temperature. For the Mg-RE binary systems, the surface tension increased with the addition of RE elements, while for the Al-RE binary systems, the surface tension exhibited maximum values in the composition range of mole Fraction of RE = 0.6–0.8. For various Mg-xAl (mole fraction of Al = 0.02, 0.06, 0.1)-RE ternary systems, the surface tension increased linearly with addition of RE content (mole fraction of RE = 0–0.5). The ternary surface tension contours in the whole composition range were also predicted by the present model, which can guide the design of novel Mg–Al–RE casting alloys.