Effects of vacuum heat treatment on microstructures and mechanical properties of Al CoCrCuFeNi high-entropy alloys fabricated by spark plasma sintering

This study aims to provide insights into improving the performance of ultrafine WC-based cemented carbides with AlCoCrCuFeNi (x is molar ratio) high-entropy alloy (HEA) binders through heat treatment. The mechanical alloyed AlCoCrCuFeNi HEA powders were densified by spark plasma sintering (SPS), followed by vacuum heat treatment at 500–800 °C for different durations to investigate microstructures and mechanical properties. A Fe-Cr structural BCC phase transforms to a Fe-Ni structural FCC phase in the AlCoCrCuFeNi system after the SPS process, and the FCC phase becomes predominant at Al content less than x = 1.5. The increase in heat treatment temperature, holding time, and Al content raises the fraction of the BCC phase for the HEAs at the expense of the FCC phase. The mechanical properties of the heat-treated AlCoCrCuFeNi HEAs are mainly determined by the solid solution strengthening effect of Al atoms, the proportion of FCC/BCC phase, and the Cu-rich nano precipitates. After heat treatment at a low temperature of 500 °C for 1 h, the AlCoCrCuFeNi HEA achieves a balanced mechanical property, combining high hardness and strength with significantly improved ductility. The findings support that tailoring the properties of ultrafine WC-HEA cemented carbides that depend on HEA binder by heat treatment is feasible.