Investigation of the Size Effect of Nickel-Base Superalloy Single Crystals Based on Strain Gradient Crystal Plasticity

Nickel-base superalloys consist of two phases, named the gamma phase of the nickel matrix and the gamma ' phase of precipitates, which are dispersed uniformly in the matrix. The gamma ' precipitates have strong effects on the mechanical properties of the alloys. In this article, the mechanism-based strain gradient crystal plasticity theory based on thermal activated theory has been developed. This theory is implemented into ABAQUS as an interface of user material (UMAT) to investigate the additional strengthening mechanism associated with the deformation gradients of the single crystal with dispersed inclusions. Four different precipitate sizes with the same volume fraction are studied using a unit-cell model of alloys. The results show a significant size effect of precipitates on nickel-base superalloys.