Influence of γ？ volume fraction on creep of Ni-based superalloy through phase-field simulations
(State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi’an 710072, China)
Abstract: γ？ volume fraction (fv) plays a critical role in the mechanical properties of Ni-based single-crystal superalloys. A creep phase-field model is utilized to simulate the microstructure evolution and creep performance during creep under different fv conditions. The influence mechanism of fv on creep properties is investigated based on the analysis of evolutions of internal stress and strain fields. As fv increases, the morphology of γ？ rafts changes from discontinuous to continuous, while the morphological change of γ channels is opposite, the inclination of γ channels from the [010] direction to á011？ directions during tertiary creep first decreases and then increases, the creep life first increases and then decreases, and the main distribution of creep damage shifts from γ？ to γ？/γ interfaces and γ channels. The longest creep life under fv of 0.65 can be attributed to the stable γ？ raft structure, the lowest stress and strain in γ channels, and the slowest damage accumulation.
Key words: phase-field simulation; internal stress; internal strain; creep behavior; single-crystal superalloys