Tailoring the microstructure of a non-equiatomic Fe40Mn27Ni26Co5Cr2 high-entropy alloy via friction stir processing

Abstract

High-entropy alloys (HEAs) with a face-centered cubic (FCC) lattice exhibit remarkable work-hardenability and high fracture toughness at cryogenic temperatures. However, in some non-equiatomic FCC HEAs, grain boundary melting defects may form during the homogenization process, which may lead to embrittlement of the grain boundaries. To address this issue, in this study, we propose the use of friction stir processing (FSP) to tailor the microstructure of a typical non-equiatomic Fe40Mn27Ni26Co5Cr2 HEA. After FSP, the mechanical properties of the non-equiatomic Fe40Mn27Ni26Co5Cr2 HEA were substantially improved. The study revealed that the improved mechanical properties could be attributed to the intense thermal-shear effect of FSP, which simultaneously eliminated grain boundary segregation and induced discontinuous dynamic recrystallization to refine grain size. Our findings not only shed light on understanding the embrittlement mechanism of homogenization treatment in non-equiatomic FCC HEAs, but also provide a useful route to improve the mechanical properties of FCC HEAs.

Keywords

• High-entropy alloys
• Homogenization treatment
• Friction stir processing
• Grain boundary melting defects
• Mechanical properties