Phase-field modeling of θ′ precipitation kinetics in 319 aluminum alloys

Understanding the morphological evolution of precipitates is critical for evaluating their hardening effects and therefore improving the yield strength of an alloy during aging. Here we present a three-dimensional phase-field model for capturing both the nucleation and the growth kinetics of the precipitates and apply it to modeling theta' precipitates in 319 aluminum alloys. The model incorporates the relevant thermodynamic data, diffusion coefficients, and the anisotropic misfit strain from literature, together with the anisotropic interfacial energy from first-principles calculations. The modified classical nucleation theory is implemented to capture the nucleation kinetics. The model parameters are optimized by comparing the simulation results to the experimentally measured peak number density, average diameters, average thicknesses and volume fractions of precipitates during isothermal aging at 463 K (190 degrees C), 503 K (230 degrees C) and 533 K (260 degrees C). Further model improvements in terms of prediction accuracy of the precipitate kinetics in 319 alloys and the remaining challenges are discussed.