Multi-scale investigation on grain size effect of a powder metallurgy Ni-based superalloy based on simulation and experimental characterization

Abstract

In this work, the crystal plasticity finite element method (CPFEM) was employed to investigate the impact of grain sizes on the tensile properties of powder metallurgy (PM) Ni-based superalloy FGH4096 at room temperature. Combining simulations and experimental results, the consistency between the model framework and the actual tensile state of the material was confirmed, and the effect mechanism of fine grain strengthening in the material was revealed by various characterization methods. Finite element models are established with average grain sizes of 20 μm and 50 μm during the simulation process. The simulation results show that the Mises stress and cumulative shear strain for small grains are 9.2 % and 6.4 % higher, respectively, than for large grains at a plastic strain of 20 %, and the stress and strain concentration is more pronounced. The average grain sizes of 18.65 μm and 48.23 μm are obtained by experiment, and the yield strength (YS) and ultimate tensile strength (UTS) of small grains are increased by 29.67 % and 14.94 %, respectively. The analytical results illustrate that small grains have low dislocation density and precipitate size, high subgrain fraction and Schmid factor. Thus, the strength and plasticity of small grains is better than that of large grains.