Influence of carbon content and thermomechanical treatment on structure and properties of Fe-Co-Ni-Cr-C system high-entropy alloys

Abstract

The effect of carbon content on structure and mechanical properties of Fe65(CoNi)25Cr10 and Fe65(CoNi)25Cr9.5 C0.5 high-entropy alloys was studied. In addition, the effect of thermomechanical treatment on structure and properties of the Fe65(CoNi)25Cr9.5C0.5 alloy was investigated. Microstructure of the alloys in the as-cast conditions had a two-phase structure consisting of a face-centered cubic (fcc) and a body-centered (bcc) phases. An increase in the carbon content from 0 to 0.5 at % led to a decrease in the bcc phase amount from 90 to 35%. Besides the carbon addition resulted in higher plasticity without significant loss in strength. Cold rolling of the Fe65(CoNi)25Cr9.5C0.5 alloy to 80% thickness reduction leads to an increase in the bcc phase amount up to 40%. Subsequent annealing at 700-900°C for 10 min led to the development of a recrystallized microstructure with an increased volume fraction of the bcc phase, and the precipitation of M23C6-type carbides. Relationships between the chemical composition, processing, structure and mechanical properties of alloys are briefly discussed.