Mechanical properties of AlCoFeCrVNi and AlCoFeCrVTi high-entropy alloys obtained by sintering under pressure

Abstract

The complex of mechanical characteristics, such as microhardness, HV, plasticity characteristic, d_H, yield strength, s_s, and elastic limit, s_е, of equi-atomic AlCoFeCrVNi and AlCoFeCrVTi high entropy alloys obtained by mechanical alloying and subsequent sintering under pressure was determined. After mechanical alloying of the powder mixtures of the starting components, nanostructured alloys are formed, which mainly consist of a bcc solid solution, a small amount of fcc solid solution, and tungsten carbide in the form of small particles due to milling. After sintering under pressure of 5 GPa at a temperature of 800 °C, the alloys contain solid solutions with a bcc and fcc structure and a small amount of WC carbide, however, the main phase in both alloys is a fcc solid solution. The mechanical characteristics of the alloys were determined by microindentation technique under static indentation. The microhardness number, HV, and the plasticity characteristic δ_H were calculated from the results of measurements of impressions obtained by the Vickers pyramid. The yield strength s_s and the elasticity limit s_е were determined from the “stress-strain” curves, which were constructed using a set of trihedral indenters with different sharpening angles. After sintering under pressure, the alloys have high strength characteristics due to the effects of solid-solution strengthening, strong distortion of the crystal lattice, and dispersion hardening by tungsten carbide particles. The microhardness numbers, HV, of AlCoFeCrVNi and AlCoFeCrVTi alloys are 11.7 GPa and 13.7 GPa, and the yield strength ss are 3.45 GPa and 4.1 GPa, respectively. The addition of Ti instead Ni of into the alloy shows the best strengthening effect in our experiments.