Microstructure, mechanical properties, and brittle fracture of a cast nickel-aluminum-bronze (NAB) UNS C95800

Abstract

Nickel aluminum bronzes (NAB) are corrosion resistant alloys used in seawater environments as parts of valves, fittings, ship propellers, pumps, pump shafts, and heat exchangers. As many other alloys, NAB can be cast or wrought. More recently, additive manufacture methods have been studied for this class of materials. Corrosion problems are reported in the literature, and are related to the presence of β phase, de-alloying and low aluminum content. In this work, the mechanical behaviour of a cast NAB alloy was investigated by tensile and impact tests. The material has been heat treated to eliminate the deleterious β′ phase. Brittle fractures were observed in the tensile and Charpy impact tests, and the micro-mechanisms of these fractures were investigated by fractography in the scanning electron microscope (SEM). The true stress–strain curve of the tensile test was successfully modelled by Hollomon’s and Ludwik’s equations. The results are useful to the application of cast NAB UNS C95800 alloy.