Effect of carbon content, deformation and annealing on the structure and properties of interstitial TRIP high-entropy alloys

Abstract

In this work, the effect of carbon content on the structure and mechanical properties of Fe(50-x)Mn30Co10Cr10Cx (x=0; 0.5; 1.0 at.%) interstitial high entropy alloys was studied. In the as-cast condition, the alloys were composed of the face centred cubic (fcc) and hexagonal close packed (hcp) phases; the amount of the hcp phase decreased from 46% to 20% as the carbon concentration increased from 0 to 1 at.%. The carbon content had a limited effect on the strength of the alloys, yet the ductility was enhanced significantly as the result of interstitial alloying. Furthermore, Fe49Mn30Co10Cr10C1 alloy was cold rolled to a reduction of 56% reduction and annealed at 700-900°C for 1 hour. After cold working, the alloy has attained almost fully the hcp structure. Annealing resulted in (i) transformation of the deformation-induced hcp phase into fcc; (ii) development of recovery and recrystallization; (iii) precipitation of Cr-rich M23C6 carbides. The cold-rolled alloy was very strong but brittle; annealing resulted in softening and increase of the ductility. The relationships between the chemical composition, structure and mechanical properties of the alloys are briefly discussed.