Hot deformation behavior and processing map of a γ′-hardened nickel-based superalloy

The hot deformation behavior of a gamma'-hardened nickel-based superalloy was investigated by means of isothermal compression tests in the temperature range of 1010-1160 degrees C and strain rate range of 0.0011- 1 s(-1). The results show that the hot activation energy of the alloy is about 427.626 kj/mol. On the basis of experimental data, processing maps were developed by utilizing the principles of the dynamic materials model (DMM). The processing maps exhibit one domain with high efficiency of power dissipation. At the strain of 0.6, the domain occurs in the temperature range of 1105-1160 degrees C and strain rate range of 0.02-0.25 s(-1) with a peak efficiency of about 42.2%. Microstructure observations reveal that full dynamic recrystallization (DRX) occurred in the domain. In the processing maps, the curvature changes of the isoefficiency contours occur in the temperature range of 1080-1090 degrees C, which is at the dissolution temperature of gamma' phase in the alloy. Moreover, it can be found that the strain has an effect on the efficiency of power dissipation. The efficiency value increases with increasing strain in the high strain rate domain (0.1-1 s(-1)), while the efficiency value decreases with increasing strain in the high temperature (1080-1160 degrees C) and low strain rate (0.001-0.01 s(-1)) domain. The flow instability is predicted to occur in the high strain rate domain, which is manifested as adiabatic shear bands. (c) 2014 Elsevier B.V. All rights reserved.