MICROSTRUCTURE EVOLUTION MECHANISM BASED CRYSTAL-PLASTICITY CONSTITUTIVE MODEL FOR NICKEL-BASED SUPERALLOY AND ITS FINITE ELEMENT SIMULATION

The nickel-based superalloy has been widely used in turbine engines of aerospace and marine industries for its excellent strength and high resistance to creep and oxidation at elevated temperature. These excellent mechanical behaviors root in its unique two-phases microstructure. Based on the homogenization method and representative volume cell (RVC) model, a crystal-plasticity (CP) constitutive model with information of two-phases microstructure and disloca-tion evolution was developed for nickel-based superalloys. By introducing various dislocation densities as major internal variables, the present constitutive model fully considered a series of dislocation mechanisms, including octahedral glide, cubic slip, climb, cross slip and bowing-out in the γ phase, and precipitate shearing and the Kear-Wilsdolf lock formation in the γ' phase. Based on this, a user material subroutine (UMAT) for this CP constitutive model was realized in the FEM software ABAQUS. By using this UMAT module, the creep, monotonic and cyclic mechanical behaviors of single-crystalline and poly-crystalline nickel-based superalloys were modeled under different temperatures and various loading orientations. The computationally obtained results were in good accordance with the experimental data, indicating that the present CP constitutive model with information of microstructures and dislocations evolution could uniformly describe various mechanical behaviors of nickel-based superalloys under different temperatures and loadings, including the monotonic plasticity, creep and cyclic plasticity.