Irreversible phase transition of the Fe50Mn30Cr10Co10 high entropy alloy under stress

The Fe50Mn30Cr10Co10 high entropy alloy has attracted research interest in recent years due to its ability to overcome the strength-ductility trade-off. A recent study reported that a nanolaminate dual-phase microstructure, derived from the bidirectional transformation of Fe50Mn30Cr10Co10 alloy under stress, might be the main reason for its exceptional mechanical properties. Here, we report a unidirectional and irreversible phase transition from a face-centered-cubic to a hexagonal-close-packed (HCP) structure in the Fe50Mn30Cr10Co10 alloy under stress, using the in situ high-pressure x-ray diffraction method. An almost pure HCP phase is obtained at pressures exceeding 20 GPa. It remains stable in further loading and unloading processes. Transmission electron microscopy analysis indicates that dislocation motion along the {111}< 11 2 <overline> > slip system results in the irreversible phase transition and the formation of nanolamellar microstructures in the Fe50Mn30Cr10Co10 alloy. Our study provides insights into understanding the deformation mechanism of Fe50Mn30Cr10Co10 alloy and suggests the potential to design the alloy through high-pressure manufacturing.