Simultaneous enhancement of strength and ductility in a Fe49Mn30Co10Cr10C1 high entropy alloy via cryo-rolling and annealing

The effects of cryo-rolling and annealing on the microstructure and tensile properties of a transformation-induced plasticity high entropy alloy (TRIP-HEA) with a nominal composition of Fe 49 Mn 30 Co 10 Cr 10 C 1 were investigated. The cryo-rolled (CR) specimen mostly consisted of a hexagonal close-packed (HCP) phase (~90 vol. %), with a minor fraction of the face-centered cubic (FCC) phase. The annealed specimen had a partially recrystallized microstructure, dominated by the FCC phase (80 vol. %), with a minor fraction of the HCP (20 vol. %) phase. The CR sample subjected to heat treatment at 650 °C for 10 min. exhibited a yield strength of 1100 MPa along with a uniform elongation of 31%, outperforming all the other tested conditions. Microstructural analysis was performed using electron backscattered diffraction (EBSD) and transmission electron microscopy (TEM) and revealed that this optimal balance of strength and ductility resulted from a combination of mechanisms, including grain boundary strengthening, precipitation strengthening (from M 23 C 6 -type carbides), TRIP, and twinning-induced plasticity (TWIP). This study shows a pathway to achieve high strength and ductility in HEAs through interstitial alloying and cryo-rolling and annealing in TRIP-HEAs for advanced structural applications.