Computer simulation for Ni-Cr-Al alloy during early ordering

The aging behavior of Ni-Cr-Al ternary alloy are studied at temperature 1123 K, the early ordering process are simulated at atomic-scale with microscopic phase-field model. Precipitation mechanism of low supersaturated alloy Ni-15at.%Cr-10.5at.%Al is non-classical nucleation and growth, the precipitation process include three stages, i.e. the nucleation and growth of D0₂₂ ordering phase, nucleation of Ll₂ ordering phase and transmit of Ll₂ ordering phase from D0₂₂ ordering phase. The occupation possibilities of Al and Cr in L1₂ ordering phase are similar because of substitution behavior of Cr atom, Ni₃(Cr_xAl_1-x structure are formed and coexist with D0₂₂ ordering phase, high supersaturated alloys show the congruent ordering and spinodal decomposition mechanism and the process of the ordering and clustering are precedent to low supersaturated alloys.