Tailoring microstructure and local mechanical properties of wire arc additively manufactured CuAl9Fe4 aluminum bronze alloy via heat treatment optimization

This study investigates the microstructure and local mechanical properties of wire arc additive-manufactured (WAAM) aluminum bronze (CuAl9Fe4) alloy in the as-fabricated and heat-treated conditions. A response surface methodology-central composite design (RSM-CCD) of experiments was used to model and statistically analyze Vickers and nanoindentation hardness as response variables, in relation to two key heat treatment parameters: annealing temperature and time. Microstructural analyses revealed that heat treatment facilitated grain refinement, the formation of Fe-enriched precipitate-like features, an increase in high-angle grain boundary fraction, and a reduction in dislocation density. These transformations contributed to enhanced hardness, elastic modulus, and deformation resistance, as well as improved elastic compliance. Overall, the optimized heat-treatment conditions enhanced the microstructural stability and mechanical performance of the WAAM-fabricated CuAl9Fe4 alloy. In contrast, excessive temperatures or prolonged exposure led to grain coarsening and consequent material softening.