Hot deformation behavior and workability of a Ni-Co based superalloy

The hot deform ation behavior of a new N i-Co based alloy was investigated by the isothermal compression tests in a temperature range of 1060-1180 degrees C and a strain rate range of 0.01-10 s(-1) under a true strain of 0.693. The results show that the flow stress, corrected by friction and adiabatic heating, increases with the decreasing temperature and increasing strain rate. Considering the dissolution of the cprecipitates during hot deformation, the Arrhenius-type constitutive equations w ere established segmentally via fitting the corrected flow stress data. The activation energies for the gamma + gamma' dual-phase region and the gamma' single-phase region of the alloy are 671 and 391 kJ mol(-1), respectively. The reason for higher activation energy of the gamma + gamma' dual-phase region is that gamma' ((N i,Co)(3)(Al,Ti)) precipitates hinder dislocation slip and harden the alloys during hot deformation. The processing map based on the dynamic material model (DMM) was also constructed. According to the analysis of microstructural evolution, dynamic recrystallization (DRX) occurs under all deform ation conditions. The optim um hot deform ation processing conditions for the gamma + gamma' dual-phase region are 1060-1070 degrees C/0.01-0.02 s(-1) or 1070-1141 degrees C/ 0.01-1 s(-1). In addition, the optimal processing parameter for the gamma single-phase region is 1141-1175 degrees C/0.01-10 s(-1) (except a part of flow instability domain). (C) 2020 Elsevier B.V. All rights reserved.