Phase equilibria in Al-rich Al-Mg-Sc-Zn alloys at 430 and 300°C

Optical microscopy and X-ray diffraction and electron microprobe analyses are used to study Al-Mg-Sc-Zn alloys annealed at 430 and 300°C. The Al-based solid solution is found to be in equilibrium only with binary and ternary phases of the corresponding systems; these are Al₃Sc, β(Al₃Mg₂), η(MgZn₂), and τ(Al₂Mg₃Zn₃). Sections are constructed for the isothermal tetrahedra of the Al-Mg-Sc-Zn phase diagram that correspond to a scandium content of 0.5% and magnesium and zinc contents of up to 20%.