Induction melting of an Al-50Cu alloy for improved homogeneity required for powder spheroidisation

Abstract

Copper alloys are typically produced by conventional casting processes, including spark plasma sintering (SPS), which often produce inhomogeneous mixtures of Cu or Al precipitates and unwanted intermetallic phases in solid products. Induction melting should provide good mixing, controlled heating and melt stirring, potentially improving homogeneity. Homogeneous melts should produce homogeneous powders, giving better properties in additive manufacturing (AM). To ascertain homogeneity, a density test was developed. After comminution, homogeneous powders can be used to produce high quality components. To manufacture dense AM components, spheroidised powders are needed because they increase particle packing and powder flow. An Al-50Cu (at.%) button was produced by high-frequency (HF) induction melting, to give better mixing and hence phase distributions. To identify the phases and their distributions, the as-cast sample was studied using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD), as well as absolute density using helium pycnometry. Results indicated inhomogeneity in the samples, due to Al loss, complex solidification and the densest phase settling at the bottom of the button.