CALPHAD-Based Modelling of Microstructural Evolution during D.C. Casting and Homogenization of AA3003 Aluminium Alloy

Microstructural evolution during D.C. casting and subsequent homogenization of non-heat-treatable aluminium alloys involves complex phenomena, including micro-segregation of alloying elements and intermetallic phase selection during solidification as well as phase transformations of both primary (constituents - intergranular) and secondary (dispersoids - intragranular) intermetallic phases. In this study, we simulated the microstructural evolution of AA3003 using a CALPHAD-based modelling framework implemented in ThermoCalc®. The framework integrates a Scheil-Gulliver solidification model coupled with a 1-D micro-segregation alleviation and diffusional phase transformation model (DICTRA®) and a Kampmann-Wagner Numerical (KWN) model for dispersoid precipitation (TC-PRISMA®). According to this approach, the development of a robust computational methodology is aimed at accurately predicting the influence of homogenization cycles on dispersoid precipitation, which in turn affects recrystallization behaviour via the well-known Smith-Zener drag phenomenon. Additionally, these CALPHAD-based simulations facilitate the assessment of impurity content effects on dispersoid precipitation, considering the increasing use of scrap in the fabrication of non-heat-treatable aluminium alloys. Furthermore, they provide precise estimates of Smith-Zener pinning forces as inputs for downstream mesoscale full-field process models, contributing to a holistic through-process modelling approach.