Simultaneous effects of deformation-induced plasticity and precipitation hardening in metastable non-equiatomic FeNiCoMnTiSi ferrous medium-entropy alloy at room and liquid nitrogen temperatures

In the present work, the mechanical properties of a newly developed metastable 65Fe-15Ni-8Co-8Mn-3Ti-Si (at%) ferrous medium-entropy alloy were investigated at 298 K and 77 K. The short-time annealing followed by aging treatment is employed to gain heterogeneous microstructure containing fine-and coarse-grains decorated with nanometric precipitates. The yield strength of the alloy enhances substantially from 0.9 GPa at 298 K and 1.3 GPa at 77 K in the annealed state, respectively, to 1.1 GPa and 1.5 GPa after the aging treatment, while the total elongation sustains more than 20%. This extraordinary improvement results from the synergistic effect of hetero-deformation-induced strengthening, mechanical nano-twins, and martensitic phase transformation along with precipitation strengthening of the well-distributed nano-scale Fe2SiTi and Ni3Ti precipitates during tensile deformation of the aged alloy. Therefore, the corresponding ferrous MEA can be considered as a promising candidate for ultra-high-strength components at extreme service conditions. (C) 2021 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Automated summary

The mechanical properties of a newly developed metastable 65Fe-15Ni-8Co-8Mn-3Ti-Si ferrous medium-entropy alloy were significantly enhanced after short time annealing and aging treatment, showing high yield strength and total elongation at 298K and 77K. This improvement is attributed to synergistic strengthening mechanisms and the contribution of nano-scale precipitates during tensile deformation.