EFFECT OF DOPANT AND HEAT TREATMENT ON THE MICROSTRUCTURE AND MECHANICAL PROPERTIES OF NICKEL-ALUMINUM BRONZE

The effect of dopant and heat treatment on the microstructure and mechanical properties of Nickel-aluminum bronze (Cu-10%Al-5%Ni-5%Fe-x%Mo) were extensively investigated. The cast samples were heat treated through different processes, including solutionizing, quenching, and aging; their microstructures were examined using an optical microscope, scanning electron microscopy and energy dispersive spectroscopy analysis and their mechanical properties determined. The microstructure of the as-cast samples consisted of Cu-rich 'alpha-phase, 'kappa-phases and small volume fraction of beta'-phase while solutionizing transformed the beta'-phase to a homogenous beta-phase, alpha, and kappa phases. Quenching transformed all beta phase to beta'-phase, however, aging the alloy precipitated fine dispersive strengthening kappa-phases from the quenched microstructure. The results of the mechanical tests showed that the aged samples had improved excellent mechanical properties compared to the as-cast samples. Compared to the base alloy, the tensile strength and hardness of the aged 2% Mo sample increased by 58% and 55%, respectively while the impact strength and elongation decreased by 27% and 22%, respectively. Similarly, the tensile strength and hardness of the aged 3% Mo sample increased by 44% and 49%, respectively, while the impact strength and % elongation decreased by 23.9% and 24.9%, respectively.