Quantitative Phase Field Study on the Precipitation Dynamics of γ′ Phase in Ni-Based Superalloys with Different Concentration

Abstract

A quantitative phase field simulation was performed on the dynamics evolution of γ′ (L12-Ni3X) phase in Ni-based superalloys, the microstructure, the volume fraction and the particle size distribution (PSD) of γ′ phase for Ni-Al alloys aged at 1173K with the Al concentration c=0.178, 0.180 and 0.182 were investigated, and the results were compared with Lifshitz-Slyozov-Wagner (LSW) theory and Brailsford-Wynblatt (BW) theory. As the Al concentration increases the γ′ phase morphology changed from the separated cuboidal shape to the connected rectangle shape, the nucleation and growth of γ′ phase became faster and the volume fraction of the γ′ phase increased. The average particle radius <r> of γ′ phase and the aging time t has a exponent relationship <r> ~ tn at the coarsening stage with the exponents n=0.313, 0.235 and 0.204 for c=0.178, 0.180 and 0.182, respectively. The peaks of the fitted PSDs are less than the predicted value from the LSW theory and the fitted PSDs are wider than that of LSW predicted, while they are similar to that of the BW theory as the Al concentration increases. The peaks appear at a smaller r/<r> than the predictions of the LSW and BW theories.