Microstructural Evolution And Flow Characteristics Of Mg-10Gd-3Y-0.5Zr Alloy During Hot Compression

Mg-Gd-Y-Zr series alloys are promising structural materials for their excellent mechanical properties at room and elevated temperature.The microstructural evolution and flow characteristics of Mg-10Gd-3Y-0.5Zr alloy during hot compression with temperature 350?⁴50?and strain rate 10^-1s^-110^-4s^-1 were systematically investigated by optical microscopy,transmission electron microscopy,scanning electron microscopy and electron back-scattered diffraction,etc.The dynamic recrystallization and dynamic precipitation process were studied in detail.The strain-stress curve of the alloy showed single peak indictive of dynamic recrystallization.The peak stress?10²30Mpa?and peak strain?0.02⁰.2?decreased with temperature and increased strain rate.A constitutive equation to describe the deformation process was established based on the hyperbolic sine function.The stress exponent n and apparent activation energy Q were determined to be 3.02 and 203.92kJ/mol,respectively.Dynamic recrystallization occurred during all the studied compression conditions and the dynamic recrystallization mechanism was related closely to deformation mechanism.Dislocation slip was the main deformation mechanism and continuous recrystallization nucleated by dislocation arrays is dominant accordingly.During high speed compression,twinning occurred to coordinate deformation and twining induced recrystallization took place by correlation of twinning and dislocation.Grain boundary migration became an main deformation mechanism and continuous dynamic recrystallization was nucleated by local grain boundary bulging when alloy was compressed at 450?10^-3s^-1 and 10^-4s^-1.The DRXed grain size and volume fraction increased with temperature and decreased with strain rate.Massive irregular?precipitates formed in the recrystallized region at temperature lower than 400 ^oC,especially along the recrystallized grain boundaries.The size of precipitates was increased with temperature and decreased with strain rate.The average diameter of precipitates in the alloy deformed at 400?10^-4s^-1 could be above 1?m.Dynamic precipitation and dynamic recrystallization developed inwards from grain boundaries with strain simultaneously during compression.Strain induced precipites promoted the recrystallization nucleation and refined the DRXed grains effectively.Meanwhile,dynamic recrystallization impoved the formation of precipitates by providing more nucleation locations for precipitation.