Metallurgical assessment of a hypereutectic aluminum–silicon P/M alloy

The objective of this study was to perform a comprehensive assessment on the press-and-sinter P/M processing of a novel hypereutectic aluminum–silicon alloy known as Alumix-231 (Al–15Si–2.5Cu–0.5Mg). As this patented commercial product is relatively new, the amount of scientific data available in the literature is highly limited. To address this issue sintered products were evaluated by analyzing the density before and after sintering, apparent hardness, microstructural features, tensile properties, and finally the response to heat treatment. It was determined that the optimum processing route for Alumix-231 involved compaction at a pressure of 600 MPa followed by de-lubrication at 400 °C for 20 min before being sintered at 560 °C for a period of 60 min. The optimum heat treatment involved solutionizing the samples at 520 °C for 1 h, followed by water quenching, and artificially aging the samples at 160 °C for 8 h. The system proved highly responsive to this manner of processing attaining a sintered density on the order of 98% of theoretical and a UTS of 330 MPa. Based on a combination of DSC, XRD, and EPMA analyses it was concluded that θ-type phases were the dominate precipitates formed during heat treatment.