Matrix Channel Width Evolution of Single Crystal Superalloy Under Creep and Thermal Mechanical Fatigue: Experimental and Modeling Investigations

In this study, in the respect of rafting behavior of Ni-based single crystal (SC) superalloy under creep and thermal mechanical fatigue (TMF), an image processing program is developed to investigate the probability characteristic of γ channel width, and a channel width evolution model considering non-quasi-static modification is proposed. Firstly, the fractured and interrupted tests are conducted on SC superalloy. The channel width evolution behavior under different load conditions is observed via scanning electron microscope. Then, an image processing program based on image binarization is developed to conduct statistics on channel width. The statistical results show that the stress and temperature have significant effects on rafting rate, while the phase difference has a small effect. Meanwhile, the channel width obeys lognormal distribution, and the mean values follow linear relationship with standard deviations. In the modeling part, a static model is established to predict the mean value evolution of channel width under creep condition. To be generalized to TMF condition, the model is modified by considering the non-quasi-static effect. After that, the channel width evolution model is further derived to describe the probability density distribution of channel width. The predicted channel width evolutions are in good agreement with the experimental results. The statistical results and models can provide the basis for multiscale modeling of SC superalloy.