Quantitative Phase Field Simulation of α Particle Dissolution in Ti–6Al–4V Alloys Below β Transus Temperature

Abstract

A quantitative phase field method of multi-component diffusion-controlled phase transformations coupled with the Kim–Kim–Suzuki model was applied to study the effect of initial particle size distribution (PSD) in 3D and space distribution in 2D on dissolution of α particles in Ti–6Al–4V alloy below β transus temperature in real time and length scale. The thermodynamic and mobility data were obtained from Thermo-Calc and DICTRA softwares, respectively. The results show that the volume fractions of α particles decay with time as: $$ f = f_{\text{eq}} + (f_{0} - f_{\text{eq}} )\exp ( - Kt^{n} ) $$ for four cases of PSD. The sequence of dissolution kinetics from fast to slow is: uniform PSD, normal PSD, lognormal PSD and bimodal PSD. The space distribution is found to be a major factor affecting the dissolution kinetics and the microstructures. When the distance of the particles is less than critical value, the dissolution rates reduce with the decrease in distance. The Al and V concentration fields around the particles appear more obvious soft impingement.