Deformation mechanism and microstructure evolution of hot extruded GH738 alloy fabricated by spray forming

The research on hot deformation including flow behavior, microstructure evolution via EBSD method and the constitutive characteristic model of hot extruded GH738 alloy fabricated by spray forming was conducted by using Gleeble-3500TM simulator at the temperature range of 950~1150 ℃, strain rate range of 0.001~1 s–1 and engineering strain of 50%. The results show that the flow stress decreases with increasing of the deformation temperature and decreasing of the strain rate. The peak flow stress of coarse grain GH738 is higher than that of fine grain within the extruded GH738 alloy. The activation energy Q of extruded GH738 alloy is 651.08 kJ·mol–1. The hot deformation activation energy Q of GH738 alloy is tending to increasing with the decreasing of the original average grain size. The microstructure evolutes from original stretched grain to equiaxed grain with the increasing deformation temperature through the onset of recrystallization. The full dynamic recrystallization microstructure is obtained at the temperature above 1000 ℃ and the microstructure tend to coarsen with the higher deformation temperature.