Tailoring Microstructure and Performance of CMT-WAAM Deposited Al 4047 Alloy Wall Through Interlayer Addition of Rare Earth La2O3 Nanoparticles

Abstract The present work investigates the effect of rare earth Lanthanum oxide (La2O3) nanoparticles on the microstructure, mechanical properties, and residual stress of Al 4047 alloy wall fabricated via cold metal transfer-based wire and arc additive manufacturing (CMT-WAAM). Results from microstructural analyses reveal that without La2O3 nanoparticles, the structure consists of coarse columnar crystals and dendrites, while the addition of La2O3 nanoparticles leads to significant refinement, promoting fine equiaxed dendrites and a reduction in pores. Energy dispersive spectroscopy (EDS) mapping confirms the uniform distribution of La2O3 nanoparticles, which aids in enhancing nucleation during solidification. Mechanical results show that walls with nano-La2O3 exhibit a uniform and increased microhardness and tensile strength, with improvements being more pronounced in the deposition direction than in the build direction. Although the presence of nanoparticles led to reduced ductility, as evidenced by lower elongation and finer, more uniformly distributed dimples were observed in the fractographic analysis. Adding La2O3 nanoparticles decreased residual stress in the wall, with higher compressive stress in the bottom layers from repeated heating, while the top layers experienced tensile stress from rapid cooling.