Prediction for the Early Precipitation Process of Ni75AlxV25-X System with Lower Al Concentration by the Phase-Field Model
相场法预测低铝合金Ni75AlxV25-x的早期沉淀过程

The microscopic phase--field approach was used in modeling the early precipitation process of Ni75AlxV25-x alloy with lower Al concentration on an atomic scale through the simulation of atomic pictures, calculation of order parameter profiles and change of volume fraction of the ordered phases. The results show that ordered phases precipitated and formed a pseudobinary system; precipitated earlier than g phase by a congruent ordering + spinodal decomposition (CO+SD) mechanism and thus produced a nonstoicheometric ordered phase, then the nonstoicheometric g phase precipitated by a non--classical nucleation and growth (NCNG) mechanism at the boundaries of phases, meanwhile, both of them transformed to stoicheometric ordered phases. With the increase of Al composition, the congruent ordering process of phase becomes more slow, and g phase precipitation becomes earlier, the occupation percentage of gincreased and that of phase decreased.