Microstructure and mechanical properties of a high entropy alloy with a eutectic composition (AlCoCrFeNi2.1) synthesized by mechanical alloying and spark plasma sintering

Eutectic high entropy alloys synthesized via conventional casting have been intensely studied recently owing to their superior mechanical properties. In the current work, AlCoCrFeNi2.1 eutectic high entropy alloy has been synthesized for the first time via a combination of mechanical alloying and spark plasma sintering (MA-SPS) route. The alloy primarily showed FCC and B2 phases in addition to minor secondary phases. As opposed to previous literature on MA-SPS, WC contamination from milling media was eliminated by adopting a shorter milling time. Apart from the elimination of WC, the adopted strategy is an effective method to obtain a heterogeneous microstructure, which has been demonstrated to enhance both strength and compressive strain to failure. Heat treatment of the alloys for a short duration of 10 min at 1200 °C was found to improve both strength and compressive plasticity. This was attributed to the reprecipitation of secondary phases and the presence of heterogeneous microstructure. [Display omitted] •Minimum WC contamination due to shorter milling durat.•MA+SPS resulted in bimodal (hierarchical) microstructure (FCC, B2,carbides).•Bimodal and multiphase microstructure resulted in superior strength but brittle carbide and oxides limited the plasticity.•Heat treatment of MA+SPS resulted in increase in strain to failure.•Strengthening contributions was quantified and the prime strengthening factor was found to be grain refinement.