Effect of single and double stage homogenization treatments on microstructure and properties of wire + arc additively manufactured 2319 Al alloy

Abstract

In this study, the effect of homogenization treatments (single and double stage) on the wire + arc additively manufactured (WAAM) 2319 aluminum (Al) alloy were analyzed. This involved an in-depth study on the diffusion and dissolution of eutectic phases (α(Al) + θ(Al₂Cu)) in the matrix using microstructural characterization techniques (DSC, XRD, optical and electron microscopy). Homogenization treatment parameters (temperature and time) were pre-determined based on DSC analyses. These parameters were later confirmed using homogenization kinetics calculations. A single-stage homogenization at 530 °C/24 h facilitated an almost complete diffusion of θ phase, but some of them remained undissolved at the grain boundaries. This treatment resulted in the reduction of hardness, ultimate tensile strength and yield strength by 26.0 %, 28.5 % and 28.8 %, respectively. A double-stage homogenization at 480 °C/8 h + 530 °C/24 h facilitated diffusion of Cu and dissolution of θ phases. This treatment improved the elongation (by 2.8 %), while the hardness, ultimate tensile strength and yield strength was still reduced by 28.7 %, 28.3 % and 26.2 %, respectively. θ phase at the grain boundaries almost disappeared, with several small θ phase particles remained within the grain. The homogenization treatments eliminated the segregation of θ phase and Cu element formed during the additive manufacturing (AM) process, improved the homogeneity of the WAAM 2319 Al alloy microstructures but with a compromise in the mechanical properties.