STABLE AND METASTABLE PHASE-EQUILIBRIA IN MGZN2-ZN AND MG2SN-MGZN2-SN-ZN ALLOYS

The stable and metastable binary MgZn2-Zn and ternary Mg2Sn-MgZn2-Sn-Z n alloys are reexamined using thermal and microstructure analysis. Ver y thin-walled silica ampoules are positioned directly on top of the th ermocouple to perform the differential thermoanalysis (DTA). The ampou les can be removed and quenched in water from any temperature. Microst ructural changes can be therefore compared directly with the correspon ding DTA effect. Metastable states in MgZn2-Zn and Mg2Sn-MgZn2-Sn-Zn a lloys and their transitions into the stable equilibria are demonstrate d. For both systems, in addition to the stable phase equilibria also m etastable ones are presented in which, due to nucleation problems, the Mg2Zn11 phase does not appear.