A novel cobalt-free oxide dispersion strengthened medium-entropy alloy with outstanding mechanical properties and irradiation resistance

A novel cobalt-free oxide dispersion strengthened (ODS) equiatomic FeCrNi medium entropy alloy (MEA) was successfully fabricated through mechanical alloying and hot extrusion (HE). The ODS FeCrNi MEA is composed of a single face-centered cubic (FCC) matrix, in which highly dispersed oxide nanoparticles, including Y2Ti2O7, Y2TiO5 and Y2O3, are uniformly distributed. Compared with the FeCrNi MEA, the ODS FeCrNi MEA exhibits the improved yield strength (1120 MPa) and ultimate tensile strength (1274 MPa) with adequate ductility retention (12.1%). Theoretical analysis of the strengthening mechanism indicates that the high strength is mainly attributed to the grain-boundary strengthening caused by fine grains and the precipitation strengthening resulted from the oxide nanoparticles. Meanwhile, the matrix that easily activates mechanical twinning during the deformation process is the main reason to ensure moderate ductility. In addition, the introduction of high-density oxide nanoparticles can disperse the defect distribution and suppress the defect growth and irradiation-induced segregation, leading to the excellent irradiation resistance. These findings provide innovative guidance for the development of high-performance structural materials for future nuclear energy applications with balanced strength and ductility.