| Abstract Scope |
Wire arc additive manufacturing (WAAM) is emerging as an attractive manufacturing route for large-scale nickel aluminum bronze (NAB) components used in demanding marine applications because of its high deposition rate, material efficiency, and potential to alleviate supply chain constraints. Although WAAM-processed NAB has demonstrated superior mechanical properties compared with conventionally cast material, the repeated thermal cycles inherent to layer-by-layer deposition generate complex thermal gyrations that can produce significant spatial variations in phase transformations, microstructure, and mechanical properties. Understanding these localized thermal effects is essential for achieving reliable qualification of WAAM components.
In this study, the influence of thermal gyrations on the microstructural evolution of WAAM-fabricated NAB was investigated through an integrated experimental and computational approach. Spatially resolved X-ray diffraction (XRD) was performed across the build to quantify variations in phase constituents, lattice spacing, peak broadening, and crystallographic texture. Automated microhardness mapping was conducted at 0.5 mm intervals to evaluate local mechanical property variations, while finite element thermal simulations using ABAQUS were employed to predict localized thermal histories during deposition.
The results reveal substantial microstructural heterogeneity throughout the deposit. Hardness mapping shows local variations approaching 85 HV, indicating pronounced differences in mechanical response. XRD measurements demonstrate spatial variations in κ-phase distribution, α-phase texture, lattice strain, and diffraction peak broadening, confirming that repeated reheating cycles significantly alter the local microstructure. A systematic left-to-right trend in lattice spacing suggests the presence of residual stress associated with the deposition direction. However, direct correlation between simulated reheat temperatures and measured microstructural or hardness variations remains inconclusive, indicating that multiple interacting thermal and metallurgical factors govern the evolution of the deposit.
Ongoing work will focus on refining thermal simulations, validating residual stress distributions, performing GleebleŽ based thermal cycle experiments, and conducting detailed SEM/TEM characterization of κ-phase morphology and chemistry. These efforts will establish quantitative relationships between thermal history, microstructure, residual stress, and local mechanical properties, providing the scientific foundation for microstructure-informed qualification and process optimization of WAAM-produced NAB components. |