Microstructure and creep behaviour of Mg-12Gd-3Y-1Zn-0.4Zr alloy

Microstructure and creep behaviour of Mg-12Gd-3Y-1Zn-0.4Zr alloy prepared by squeeze casting were investigated. Transmission electron microscope (TEM) observation revealed that a kind of lamellar-shaped morphologies 14 h long-period stacking order structure (LPSO) and dense beta'-phase precipitates were formed by heat treatment. The alloy exhibited good creep resistance. It was shown that the creep-resistant performance kept stable because of the restriction of dense beta'-phase precipitates and LPSO phases to the movement of dislocations, and the formation of beta-phase plates took responsibility for the softening of material during creep. Stress and temperature dependence of the steady-state creep rate were studied over stress range of 50-100 MPa and a temperature range of 250-300 degrees C, and a dislocation creep mechanism was proposed for the alloy.