Modified Johnson-Cook description of wide temperature and strain rate measurements made on a nickel-base superalloy

In this study, uniaxial compression experiments of a Nickel-base superalloy is conducted over a wide range of temperatures (298-1073K) and strain rates (0.1-5200/s) to obtain further understandings of the plastic flow behaviours. The temperature and strain rate effects on the plastic flow behaviour are analysed. The flow stress decreases with increasing temperature below 673K. Within the temperature range of about 673-873K, the flow stress varies indistinctively, and even increases slightly with increasing temperature. As the temperature further increases, the flow stress decreases again. The flow stress of the Nickel-base superalloy displays insensitive to strain rate below 800/s and an enormous increase with increasing strain rate in excess of 800/s. Then the effects of temperature and strain rate on the microstructure are discussed. The result shows that high strain rate and high temperature may make the grain boundary of Nickel-base superalloy frail. Taking into account the anomalous temperature and strain rate dependences of flow stress, modified J-C constitutive model is developed. The model is shown to be able to accurately predict the plastic flow behaviour of Nickel-base superalloy over a wide range of temperatures and strain rates.