A comparative study of a solid solution hardening in carbon-alloyed FeMnCrNiCo0.95C0.05 high-entropy alloy subjected to different thermal–mechanical treatments

Abstract

Different thermal–mechanical processing regimes were used to provide a precipitate-free austenitic structure in interstitial FeMnCrNiCo0.95C0.05 high-entropy alloy containing 1.07 at. % of carbon. Relative to interstitial-free FeMnCrNiCo alloy (a = 0.3599 nm), an expanded FCC crystal lattice (a = 0.3602–0.3603 nm) is typical of as-cast and solution-treated specimens, but grain-boundary carbides are also observed in them. Near complete carbon dissolution in austenite of FeMnCrNiCo0.95C0.05 high-entropy alloy was achieved utilizing two multistage thermal–mechanical processing regimes, which included the combinations of (i) a high-temperature anneal (25 h total), hot forging and cold rolling, and (ii) cold rolling with intermediate high-temperature anneals (6 h total). Despite the fact that both processing regimes provided high solid-solution hardening of austenite (a = 0.3611 nm) and complete dissolution of grain-boundary precipitates, some individual coarse carbides were identified in microstructure of the alloy. Both processing regimes enhanced the mechanical properties of the alloy.