Phase-field simulation of evolution kinetics of second γ′ phase in Ni-Al alloy under tensile stress

The precipitation and evolution of secondary y'-Ni3Al phase under the tensile stress in Ni17at. %Al alloy were studied by using phase-field simulation. The coarsening of secondary y' phase via the Ostwald ripening and coalescence coarsening is revealed in system of bimodal y' precipitates, and the concentration inhomogeneity inside of the primary and secondary y' phase is clarified under the influence of tensile stress. The y' phase presents a high concentration at the boundary regions of y' phase under the tensile stress, the tensile stress induces a high diffusion potential and drives the directional diffusion of Al, the Al concentration in y' phase reduces parallel to the tensile stress, while it rises in direction perpendicular to the tensile stress, which produces the N-type rafting. In addition, the tensile stress accelerates the dissolution of small y' phase, results in the increase of the volume fraction and radius of primary y' phase, while that of secondary y' phase decreases. The cube of average radii of primary and secondary y' phase follows a linear relationship with time in the early stage of precipitation, while a sharp rise happens for large tensile stress at later coarsening stage.(c) 2022 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).