Successive strain hardening mechanisms induced by transformation induced plasticity in Fe60Mn20Co10Cr10high entropy alloys

Abstract

Transformation induced plasticity (TRIP) effect in high entropy alloys (HEAs) overcomes the strength-ductility "trade-off"and leads to the synchronous improvement of strength and ductility. In this work, we studied a TRIP Fe60Mn20Co10Cr10 HEA with a dual-phase structure consisting of face-centered cubic matrix and hexagonal close-packed (HCP) martensite. By warm-rolling and subsequent annealing, three samples with different recrystallization conditions and HCP phase volume fractions were obtained. The alloys exhibit a good combination of ultimate tensile strength (∼700-900 MPa) and elongation (∼45%-55%), representing sustainable strain hardening behavior over extended deformation regime. To reveal the deformation mechanism of the present TRIP HEA, the method to determine the stacking fault energy (SFE) via a regular solution model was discussed, and the SFE of Fe60Mn20Co10Cr10 alloys at 300 K was estimated as 15.3 mJ/m2. The low SFE promotes the formation and overlapping of stacking faults via dislocation interaction, which provides nucleation sites of HCP martensite and further contributes to the striking strain hardening capacity upon tension.