Microscopic phase-field calculate on aging behavior of Ni₇₅Al_21.5Ti_3.5 alloy

The aging behavior of Ni₇₅Al_21.5Ti_3.5 alloy at 873 K was studied by microscopic phase-field model. Based on the analysis of atom figures, the average diameters and number of order phase, and the evolution of atom occupied probabilities, the problems about the ordering and cluster of Al and Ti, the nucleation mechanism of ordered phases, coarsening behavior, and atom preferential occupation were investigated. The results show that the nucleation mechanism of order phase is spinodal decomposition, and the final order degree of Al atoms approximates 1 which also accompanies the Ni-Al anti-site. Ti atoms don't reach ordering wholly and prefer to occupy Al site. During the growth of order phase, the dynamic exponent of the particles coarsening approaches 1/2 at the early stage, but falls to 2/5 at the late stage.