Anomalous behaviors of a single-crystal Nickel-base superalloy over a wide range of temperatures and strain rates

Abstract

This study is concerned with the plastic behaviors of a newly developed single-crystal Nickel-base superalloy over a temperature range of 293–1273 K and over a strain-rate range of 0.001–4000/s. Both static and dynamic loading tests were conducted to study the true stress–true strain behaviors of the superalloy along the nominal orientation [001]. Anomalous high temperature peak of the flow stress and the property of tension/compression asymmetry were noticed in the tests. Investigation on the experimental results was carried out to study the strain-rate effect on the temperature-dependent anomalies of the flow stress. It was found that the peak of the flow stress shifts to a higher temperature as the applied strain rate increases. Subsequent study of the temperature-dependent rupture property of the material revealed that the path of the crack propagation is dependent on the temperature. The strengthening and failure mechanisms of the material were established based on the experimental observations. Finally, a constitutive model was developed to describe the temperature and strain-rate effects on the material's yield behavior. The model is able to capture the anomalous temperature peak of the yield strength, which is dependent on the applied strain rate. It was demonstrated that the yield behavior of the superalloy can be adequately predicted over a wide range of temperatures and strain rates.