Hot deformation behavior and processing workability of a Ni-based alloy

In the present work, the high-temperature deformation behavior of a U720LI alloy was investigated by means of hot compression tests at temperatures of 1060-1180 degrees C, strain rates of 0.001-10s(-1) under true strain of 0.8. The Arrhenius-type model, considering the dissolution of gamma' precipitates, was established on the basis of the friction and adiabatic heating corrected flow stress data. The hot deformation activation energies for quasi-gamma phase and gamma+gamma' dual-phase microstructures were determined as 417 kJ mol(-1) and 687 kJ mol(-1), respectively. The high activation energy for gamma+gamma' dual-phase microstructures was mainly attributed to the precipitation hardening effect of gamma' (Ni-3(Al,Ti)) particles which hindered dislocation slip via the pinning effect during hot deformation. The processing map was developed based on the dynamic material model. According to the detailed microstructural investigations, the optimum hot deformation domains of U720LI alloy were identified as 1080-1100 degrees C/0.01-0.3s(-1) for gamma+gamma' dual-phase microstructure and 1140-1160 degrees C/0.01-0.1s(-1) for quasi-gamma phase microstructure, respectively. (C) 2018 Elsevier B.V. All rights reserved.