Simultaneous enhancement of strength and ductility in an AlCoCrFeNi2.1 eutectic high-entropy alloy via friction stir processing

Lamellar eutectic structure of as-cast AlCoCrFeNi2.1 was tailored by friction stir processing (FSP). During FSP, lamellar B2 phase was broken into ultrafine-grained particles, with dissolution of Cr-rich precipitates in B2 and formation of Al-rich precipitates in FCC (L12). Dynamic recrystallization of FCC/L12 and B2 reduced grain size to less than ∼0.5 μm. The combined effect of microstructural evolution in the processed region improved the ultimate tensile strength from ∼1000 MPa to 1360 MPa, the ductility from ∼6.5% to 10%, and the microhardness from ∼300 HV0.2 to 450 HV0.2.