Hot deformation characterization of nickel-based superalloy UNS10276 through processing map and microstructural studies

The deformation characteristics of nickel-based superalloy UNS10276 at elevated temperature were investigated by employing hot compression tests at temperatures of 950 °C-1250 °C and strain rates between 0.01 s−1 and 10 s−1. The microstructures of all samples deformed were characterized by electron backscatter diffraction (EBSD) to evaluate the softening mechanisms of alloy UNS10276. Both peak flow stress and peak strain were found to increase with increasing Zener-Hollomon parameter. The average activation energy was determined as 480 kJ/mol. Processing maps at true strains of 0.1-0.9 were developed using the experimental flow stress data. To maintain relatively lesser extent of instability, the amount of strain for hot working of alloy UNS10276 should be controlled in the range of 0.2-0.5. Based on processing map and microstructural observation, the optimum hot working window, in which the alloy UNS10276 exhibited a significant dynamic recrystallization (DRX), was identified as 1000-1220 °C and 0.07-2.2 s−1. Two instability domains were delineated in the processing map. The first one occurred at temperatures lower than 1180 °C and strain rates higher than 5 s−1 and was manifested in the form of microbands, deformation twins and lower degree of DRX. The second one occurred at temperatures ranging from 1035 °C to 1250 °C and strain rates below 0.06 s−1, for which the occurrence of dynamic strain aging (DSA) and secondary work hardening were responsible.