Abstract:Phase relation of the aluminium-magnesium-scandium system in the Al-rich range at 430℃ was investigated by means of multiphase diffusion couples along with electron probe microanalysis, X-ray diffraction and electron microscopy techniques. It consists of five single-phase fields, four 2-phase fields and one 3-phase field. The maximum solid solubilities of Mg and Sc in α(Al) solid solution at 430℃ are about 15.27%Mg(mole fraction) and 0.33%Sc, respectively. The maximum solid solubilities of Sc in Mg₂Al₃ and Mg₁₇Al₁₂ are about 1.08% and 0.03% at the same temperature. The diffusion path at 430℃ was constructed and interpreted by means of the Al-Mg-Sc equilibrium phase diagram assuming that local equilibrium is established at the phase boundaries.

Key words: Al-Mg-Sc; diffusion couple; isothermal section; diffusion path