Microstructure and phase formation in Al–20Si–5Fe–3Cu–1Mg synthesized by selective laser melting

Abstract

The Al–20Si–5Fe–3Cu–1Mg alloy was fabricated using selective laser melting (SLM). The microstructure and the phase constitution of the SLM as well as the heat treated alloy were studied. It is found that SLM not only alters the morphology of the eutectic silicon phase from rod-like to dendrite as well as particle shapes, but also significantly refines the primary silicon and Al–Si–Fe compound compared with the corresponding cast alloy. The eutectic silicon becomes coarser, whereas the primary silicon phase, the Al–Si–Fe compound show little change after heat treatment. X-ray diffraction results show the presence of only δ-Al4FeSi2 phase in the SLM alloy, whereas, the heat treated SLM alloy consists of both δ-Al4FeSi2 and β-Al5FeSi phases. The DSC analysis reveals that no quasi-peritectic reaction occurs during cooling cycle on account of the high cooling rate as well as the large diffusion distances required by the large dimensions of the δ-Al4FeSi2 phase.