Effects of initial microstructure on creep properties of Mg-8Gd-2Y-0.5Zr alloys

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Effects of initial microstructure on creep properties of Mg-8Gd-2Y-0.5Zr alloys

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WANG Meiling / CHANG Hai

The present research investigated the creep properties of the Mg-8Gd-2Y-0.5Zr alloys with different microstructures (as-cast, as-solution, T6 and as-extruded) after creeping at 200 ℃/70 MPa for 100 hours. Effects of the microstructures, including grain size, Mg5(Gd, Y) phase in cast alloy, β′ phase on creep properties were studied. The as-extruded alloy shows the worst creep resistance due to the refined grains caused by dynamic recrystallization resulting from the extrusion process. Although the Mg5(Gd, Y) phase located at the grain boundary can improve the creep properties of the cast alloy in the early stage creep, the precipitates of β′ phase in T6 alloy and those formed during the creep process in as-solution alloy, which can effectively inhibit the dislocation gliding, can be attributed as an important factor in improving the high temperature creep performance of the alloys. Consequently, the alloy after T6 treatment exhibited the lowest creep rate and the as-solution alloy possessed a better creep resistance than that of the cast alloy during the steady-state creep.