Evolution of microstructures during dynamic recrystallization and dynamic recovery in hot deformed Nimonic 80a

Dynamic recrystallization and dynamic recovery were investigated in a hot deformed nickel based superalloy, Nimonic 80a, for different amounts of deformation and strain rates of 0.1, 1.0 and 5.0 s−1. The area fraction of dynamic recrystallization was determined and micro-hardness was measured in different regions within the deformed grains. Dislocation structures were examined using transmission electron microscopy and dislocation density was determined by X-ray line broadening analysis. Micro-hardness is generally higher at grain boundaries near dynamically recrystallized grains. The overall dislocation density is highest for the intermediate strain rate of 1.0 s−1, which is consistent with variances of the average micro-hardness. This experimental observation is ascribed to dynamic strain aging of the alloy.