Soft impingement in diffusion-controlled growth of binary alloys: moving boundary effect in one-dimensional system

The impact of soft impingement on the kinetics of diffusion-controlled growth of binary alloys is investigated. An analytical approach is developed which takes into account the process of island growth, that is the time dependence of the position of the nucleus/parent phase interface. The concentration profile, the growth law, and the kinetics of the fraction of transformed phase are computed and compared with those attained for point islands. At odd with the point island approach the local kinetics of growth depends on initial supersaturation. On the other hand, the whole transformation kinetics is in good agreement with that of the point island model with an Avrami exponent close to the theoretical value n = 0.5. The concentration profile is well described by a polynomial function in the whole spatial domain, with an exception for the initial stage of the phase separation. The effect of the spatial distribution of the nuclei on the kinetics is also studied in the model case of hard-core correlation among nuclei.