Effect of Remelting and Heat Treatment on the Microstructure and Mechanical Properties Alcocrfeni2.1 Eutectic High Entropy Alloy

Abstract

In this paper, the remelting and heat treatment technology is used to treat the AlCoCrFeNi2.1 eutectic high entropy alloy (EHEA) waste to improve the mechanical properties, and realizes waste reuse. The investigation result indicated that after remelting, AlCoCrFeNi2.1 EHEA is composited of FCC(L12)+B2(BCC) eutectic structure and primary FCC phase. And the volume fraction of primary FCC phase in the remelting alloy sample is significantly higher than that in as-cast alloy, while the size of eutectic structure decreases compared to the as-cast alloy. The tensile fracture strength, tensile strain and Vickers hardness of the remelting AlCoCrFeNi2.1 EHEA respectively are 1061 MPa, 24.8%, and 334 HV, which higher than that of the as-cast AlCoCrFeNi2.1 EHEA. After heat treatment of AlCoCrFeNi2.1 EHEA, the Al,Ni-riched BCC needle-like precipitates appear in the primary FCC phase. With the increase of heat treatment temperature and time, the size of the needle-like precipitates gradually increase, and the volume fraction gradually decreases. After remelting and heat treatment of AlCoCrFeNi2.1 EHEA, the morphology of Cr-rich particles in the eutectic B2 phase changes from spherical to rod-like. After 1000°C/4 h heat treatment, the Cr-rich precipitated particles disappear. The compressive fracture strength of 900 °C/4 h heat treatmented sample reaches a maximum of 2950 MPa and the compressive strain is 45.8%. The existence of needle-like precipitates greatly improves the compressive fracture strength of the AlCoCrFeNi2.1 EHEA after heat treatment with almost no sacrifice of plasticity.

Keywords: Eutectic high-entropy alloy, Remelting, Heat treatment Microstructure, Mechanical property