Mechanical properties of high-entropy alloys

This chapter reviews mechanical properties of high-entropy alloys (HEAs) in the fields of hardness, compression, tension, serration behavior, fatigue, and nanoindentation. It shows that the hardness of HEAs varies widely from 140 to 900 HV, highly depending on the alloy systems and related processing methods. The effects of annealing treatment, alloying, and structure on the hardness are discussed. The hardness at high temperatures is also summarized. For compression tests, several parameters of materials, such as Young’s modulus, compressive yield strength, elastic strain, and plastic strain, are determined and discussed. Various loading conditions, such as temperatures, Al contents, strain rates, sample sizes, and aging/annealing effects, are reported to have influence on the microstructural evolution during compression deformation. Microcompression experiments have been performed on HEAs. Even though the study of tensile properties of HEAs is limited to few alloy systems, the effects of structures, grain sizes, alloying elements, and processing parameters on the yielding stress, ductility, and shape of the stress–strain curve, and fracture behavior are discussed. The characteristic elastic behavior is studied by in situ neutron-diffraction techniques during tension. A mean-field theory (MFT) successfully predicts the slip-avalanche and serration statistics observed in recent simulations of plastic deformation of HEAs. Four-point-bending-fatigue tests are conducted on the Al0.5CoCrCuFeNi HEA at various applied loads and reveal that fatigue properties of HEAs could be generally better, compared with conventional alloys and bulk metallic glasses. Nanoindentation studies on the incipient plasticity and creep behavior are discussed. The future work related to mechanical properties of HEAs is suggested at the end.