Thermodynamics and kinetics of isothermal precipitation in magnesium alloys

Abstract

As the lightest structural metal materials, Mg alloys are promising for wider applications but are limited by low strength and poor corrosion resistance. Precipitation is an effective way to improve the strength and other performance of Mg alloys. Facing the extremely complex precipitation process, the crystal structures of precipitates, precipitation sequence, and precipitation thermodynamic and kinetics behaviors have stimulated extensive research interests. Precipitation kinetics, which connects composition, aging processes, and precipitate microstructure, is pivotal in determining the performance of age-hardening Mg alloys. Despite numerous studies on this topic, a comprehensive review remains absent. This work aims to bridge that gap by analyzing precipitation from thermodynamic and kinetic perspectives. Thermodynamically, the stability of precipitates, nucleation driving forces, and resistances of precipitation are discussed. Kinetically, the various kinetic theories including semi-empirical models, mean-field models, phase-field model, and atomistic approaches and their applications in Mg alloys are systematically summarized. Among these, mean-field models emerge as particularly promising for accurately predicting precipitation processes. Finally, the framework for property prediction based on precipitation kinetics is introduced to illustrating the role of integrated computational materials engineering (ICME) in designing advanced Mg alloys.