Effect of Melting Condition on Microstructure and Mechanical Properties of CoCrFeMnNi High Entropy Alloy

Abstract

The casting is one of the most widely used processes for manufacturing the high entropy alloy (HEA) and is also appropriate to the mass production of alloys. However, several kinds of defects such as segregation, micro-pores and non-metallic inclusions (NMI) are inevitable during melting and casting processes. It is well known that these process-induced defects deteriorate the mechanical properties of the final products. In this paper, therefore, the origin of NMI formation and its effect on the microstructure and mechanical properties of HEA manufactured under different melting conditions were investigated. Equiatomic CoCrFeMnNi HEA was melted under different atmospheric conditions, i.e., vacuum, highly purified argon and atmospheric (i.e., air exposure) condition. After melting, the amount of interstitial impurities such as C, S, N and O in the solidified samples was measured and the characteristics of NMIs such as size distribution, number density, area fraction/surface area, morphology and chemical composition were analyzed. The features of crystallographic structure of each inclusions was analyzed by XRD and TEM and their effect was confirmed. Finally, consequent mechanical properties were investigated.