Abstract:The 430℃ isothermal section of the Al-4Mg-Sc-Zr quaternary system in the Al-rich range was determined by means of equilibrium alloys with the use of microstructure, X-ray diffraction analysis and electron probe microanalysis. There coexist three single-phase fields, two two-phase fields and one three-phase field. It is established that the phase Al₃Sc_1-0.5Zr_0-0.5 with L1₂ structure and Al₃Zr_1-0.8Sc_0-0.2 with DO₂₃ structure are in equilibrium with the α solid solution, Zr being dissolved in Al₃Sc, further substituting for about 50% Sc(mole fraction) whilst Sc is present in the phase Al₃Zr and the maximum substitution for Zr is about 20%.

Key words:  Al-4Mg-Sc-Zr phase diagram; isothermal section;intermetallis compound