Simulation Study on the Isothermal Aging Precipitation Process of Al3Sc in Al-Sc Alloys Using a High-Resolution Population Dynamics Model

Al-Sc alloys are widely applied in aerospace and automotive lightweighting owing to the excellent performance imparted by nano-sized Al3Sc precipitates. Accurate simulation of the full-cycle precipitation kinetics is critical for optimizing aging heat treatment processes, but the traditional Lifshitz-Slyozov-Wagner (LSW) theory is only applicable to the coarsening stage, while the conventional Kampmann-Wagner-Numerical (KWN) model suffers from severe numerical diffusion and fails to correct errors caused by discontinuous precipitate size distributions. To address these issues, a high-resolution population dynamics model based on the Van Leer limiter was established in this study, which is an improved KWN model that simultaneously considers interfacial energy transition during nucleation and coarsening and the effect of precipitate volume fraction on particle growth rate. Isothermal aging precipitation of Al3Sc in Al-0.2 wt.% Sc and Al-0.3 wt.% Sc alloys at 350 °C was systematically simulated, and key kinetic parameters including nucleation rate, critical nucleation radius, average precipitate radius, and normalized size distribution were calculated. The results show that the simulated average radius and normalized size distribution are in excellent agreement with experimental data, and the model accurately captures the plateau characteristic of average radius evolution during aging. Increasing Sc content significantly shortens the nucleation-growth stage and advances the onset of coarsening by approximately one order of magnitude. Compared with the LSW theory, the proposed model achieves second-order accuracy in smooth regions and suppresses spurious oscillations in discontinuous regions, fully reproducing the incubation, nucleation-growth, and coarsening stages of precipitation. This high-resolution model provides reliable theoretical support for the aging process optimization of Al-Sc alloys and offers an effective numerical method for precipitation kinetics simulation of other dilute binary alloys.