The Morphology, Crystallography, and Chemistry of Phases in Wire-Arc Additively Manufactured Nickel Aluminum Bronze

A new Wire-Arc Additive Manufacturing (WAAM) technique is used to produce Nickel Aluminum Bronze (NAB) components for marine applications in view to mitigate the problems that typically arise in a cast microstructure. In cast condition, the alloy typically exhibits microstructure that consists of an FCC Cu-rich solid solution (or alpha-phase), some retained beta-phase, and several intermetallic phases collectively referred to as kappa-phase. This study aims to characterize the crystal structures of the various kappa-phases or precipitates, their distribution, morphology, orientation relationships with the alpha-matrix, and their chemical compositions in WAAM-NAB alloy using electron microscopy. The precipitation of kappa-phase differs in morphology and chemical composition to those present in a cast NAB. In addition, some uniaxial tensile coupons were machined out of the WAAM-NAB samples, where tensile mechanical properties are superior to those of cast NAB. The effects of microstructural differences in both alloys on the mechanical properties are correlated.