Strain Rate Effects on the Mechanical Properties of an AlCoCrFeNi High-Entropy Alloy

The effect of strain rate on the compressive properties of an AlCoCrFeNi high-entropy alloy (HEA) was investigated. Microstructure of the AlCoCrFeNi HEA was observed using scanning transmission microscopy (SEM) and transmission electron microscopy. The results showed formation of a homogeneous two-phase structure. Quasi-static compression was tested under initial engineering strain rates between 10(-4) and 10(-2) s(-1). Engineering compression stress of exceeding 2500 MPa and ductility of around 12% was achieved. Dynamic mechanical behavior at room temperature was characterized by a split-Hopkinson pressure bar under strain rates between 1350 and 4000 s(-1). The AlCoCrFeNi HEA exhibited high strain rate sensitivity, especially under dynamic compression. The fluctuation of yield strength and the variation of strain rate hardening with strain rate was investigated. The various parameters of a constitutive equation for deformation of the AlCoCrFeNi HEA were obtained from the experimental data. The constitutive equations can be applied to predict the strength of alloy under various stain rates.