Hardness and strength enhancements of CoCrFeMnNi high-entropy alloy with Nd doping

Designing an alloy with both high strength and high ductility is a daunting challenge for structural materials. CoCrFeMnNi high-entropy alloy with FCC structure has been proven to be an ultra-ductile but low-strength alloy. Precipitation hardening is an effective way to solve this problem. However, the precipitation mechanisms are generally complex during the solidification process because of the composition with five or more elements in high-entropy alloys. We reported a designing concept that the liquid phase separation was used to simplify the mechanism of precipitates formation. The doped Nd separated from the matrix and precipitated with Ni and Mn because of the negative mixing enthalpy. Precipitation occurred randomly at grain boundaries and in the interior of grains. Compared to the single-phase FCC matrix, the hardness of HCP precipitates was three times of the matrix. The alloys were strengthened with good ductility and it was demonstrated by uniaxial tension tests.