Insight into the FCC→HCP Transformation in Co-Rich Co-Cr-Fe-Mn-Ni High-Entropy Alloys

The existence of an HCP phase in FCC-type high-entropy alloys can improve the alloy’s mechanical properties. In many cases, is induced by deformation. present work, FCC to transition was detected during cooling Co1.5CrFeMnNi0.5 and Co1.75CrFeMnNi0.25 alloys. Therefore, arc-melted annealed CoxCrFeMnNi2−x (x = 0.25–1.75) that were then subjected long-term vacuuming investigated using XRD, DSC, HT-XRD, thermodynamic calculation, first-principle calculation. It confirmed occurred at ~450 °C with x ≥ 1.5. volume fraction increased Co content. proven not stable above 600 °C. First-principle calculations further indicated structure more than for alloy, there a likelihood transition. Moreover, experimental tests microhardness alloy reached 213 HV because it contained substantial phase. This value much higher those other non-HCP-containing alloys, either their as-cast states or after annealing. These results provide guidance design desirable properties through strengthening.