Investigation on the σ-phase-related equilibria in Cr-Mn-Co system

The equilibrated microstructures in the Cr-Mn-Co ternary alloys annealed at 900, 1050, 1150, and 1200 °C were studied using X-ray diffraction (XRD) and electron probe micro analyzer (EPMA). The results are summarized as follows: (1) the σ phase has a wide solubility range from Cr-Co side to Cr-Mn side at all temperatures investigated; (2) the σ phase region becomes narrower as the temperature increases from 900 to 1200 ℃; (3) The (αCo) phase has a significant solubility for Cr which decreases with increasing Mn content; (4) the solubility of Co in the (Cr) phase decreases with the increasing Mn content at all temperatures investigated; (5) the solubility of Cr in the (βMn) phase slightly increases as the temperature increases from 900 to 1150 ℃, while the solubility of Co changes hardly. The experimental information obtained from this study is not only useful for the thermodynamic assessment of the Cr-Mn-Co ternary system, but also significant for the alloy design of high entropy alloy.