Effects of Homogenized Treatment on Microstructure and Mechanical Properties of AlCoCrFeNi2.2 Near-Eutectic High-Entropy Alloy

A 4 kg AlCoCrFeNi2.2 near-eutectic high-entropy alloy ingot was prepared by vacuum medium frequency induction melting. The effects of homogenized treatment on microstructure and mechanical properties of AlCoCrFeNi2.2 were studied. The results showed that all the alloys consisted of the primary FCC phases and eutectic FCC/B2 phases. After homogenized treatment, lots of precipitated phases appeared in the primary phase. The hardness of the as-cast alloy was HV296. The hardness values of samples were decreased and were around HV250 after homogenized treatment. The tensile fracture strength of the as-cast alloy reached 900 MPa, while the elongation was 18%. After homogenized treatment at 900 °C, the alloy showed the most excellent mechanical properties with the fracture strength 880 MPa and the elongation was 29%, respectively. All the alloys displayed a mixture fracture mechanism, including ductile fracture in primary FCC phases and eutectic FCC phases, and brittle quasi-cleavage fracture in eutectic B2 phases. Through a simple heat treatment method, the strength of the alloy was not reduced but the plasticity was greatly enhanced, which was more conducive to the industrial application prospects.