Effect of thermo-mechanical treatment on cryogenic mechanical properties of a medium-entropy Fe65Co12.5Ni12.5Cr9.5C0.5 alloy produced by the laser-based powder bed fusion

Microstructure and mechanical properties of the Fe65Co12.5Ni12.5Cr9.5C0.5 (in at.%) medium-entropy alloy obtained by the laser-based powder bed fusion (PBF-LB) was investigated in the as-produced condition and after (i) annealing in the interval 800–1100 °C or (ii) cold rolling followed by annealing at 800 °C. The as-produced microstructure was found to be surprisingly stable; noticeable recrystallization occurred only after annealing at 1100 °C. Cold rolling resulted in the formation of typical deformed microstructure, while further annealing led to the formation of a fine-grained recrystallized microstructure. A considerable improvement in cryogenic mechanical properties was obtained after some thermo-mechanical treatments due to the transformation-induced plasticity (TRIP) effect. The cold-rolled alloy had the best cryogenic strength characteristics; yield strength and ultimate tensile strength were found to be 1740 MPa and 2235 MPa, respectively. High strength was combined with a pronounced value of elongation to fracture of 24 %. Detailed analysis of microstructure and corresponding mechanical behavior changes caused by various processing of the as-produced alloy are presented.