Abstract
Thermodynamic calculations were employed to estimate activities and phase composition of the oxide layer for ternary dilute aluminum magnesium alloys; Al–Mg–M (M = Si, Zn, Zr, Ti, Be, or Ca). Previously, it has been reported that adding a ternary element modifies the vapor phase of Mg above the melt surface. When Be or Ca was added, a strong reduction of Mg partial pressure was recorded for small concentrations of the ternary element, in contrast with Si or Zn, where the effect was orders of magnitude smaller. This study aims to use Thermo-Calc simulations to reveal the distribution of alloying elements between the liquid metal, oxide layer, and vapor phase and predict the phase composition of oxide layers. The variation of the Mg vapor phase can be linked, at least in part, to the formation of oxide layers on the melt surface that may inhibit the diffusion of Mg.