Deformation mechanism and microstructure evolution of spray formed GH738 alloy fabricated by hot extrusion
【Abstract】The research on hot deformation including flow behavior, microstructure evolution via EBSD method, and the constitutive characteristic model of the spray formed GH738 alloy fabricated by hot extrusion is conducted using Gleeble-3500TM simulator in the temperature range of 950 °C–1 150 °C, strain rate range of 0.001–1 s−1, and engineering strain of 50%. The results show that the flow stress decreases with the increase in the deformation temperature and the decrease in the strain rate. The peak flow stress of the as-forged GH738 alloy with coarse grains is higher than that of the spray formed GH738 alloy with fine grains fabricated by hot extrusion. The activation energy Q of the latter is 651.08 kJ·mol−1 and its activation energy Q of hot deformation is tending to increase with the decrease in the as-received average grain size. The microstructure evolves from the as-received stretched grains to equiaxed grains with the increasing deformation temperature through the onset of recrystallization. The fully dynamic recrystallization microstructure is obtained at the temperature above 1 000 °C and the microstructure tends to coarsen with the higher deformation temperature.
【Keywords】 GH738 superalloy; spray forming; hot extrusion; constitutive equation of hot deformation; recrystallization microstructure;
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