Deformation mechanisms and mechanical properties of metastable (Fe60Co10Cr10Mn10Ni10)100-xCrx high-entropy alloy

Deformation mechanisms and mechanical properties of the face-centered cubic (FCC) metastable high-entropy alloy (HEA) Fe60Co10Cr10Mn10Ni10 (Fe60) with varying Cr content are systematically investigated. The metastable deformation mechanism in the as-cast Fe60 alloy is FCC to hexagonal close-packed (HCP) phase transformation, in contrast to FCC to body-centered cubic (BCC) transformation reported in additively manufactured Fe60 alloy. As the Cr content increases to 19%, the alloy retains a single FCC phase, and the FCC-HCP transformation is promoted during deformation, leading to simultaneous improvements in both tensile strength (from 367 MPa to 507 MPa) and uniform elongation (from 53% to 71%). However, further increasing Cr content to 23.5% enhances strength but severely reduces ductility due to the formation of BCC phase. Additionally, grain size plays a crucial role in determining the deformation mechanism of the Fe60 HEA, with grain refinement shifting the dominant mode from FCC-HCP transformation to deformation twinning.