Effect of sintering temperature on the microstructure and properties of powder metallurgy Hf0.5Nb0.5Ta0.5Ti1.5Zr refractory high-entropy alloy

Abstract

The present work is focused on the synthesis and mechanical properties evaluation of non-equiatomic Hf0.5Nb0.5Ta0.5Ti1.5Zr Refractory High-Entropy Alloy (RHEA). For the alloy production, a combination of mechanical alloying (MA) process in a planetary ball mill and hot pressing (HP) for powder densification was utilized. The effect of different sintering temperatures was explored in a temperature range of 1200 °C up to 1600 °C. The bulk material was then subject to investigation in terms of its microstructural features, elemental and phase composition and basic mechanical properties by scanning electron microscopy (SEM), X-ray diffraction (XRD), as well as hardness testing, density determination by Archimedes’ principle. The results show that very hard fine grained bulk materials were achieved in all microstructures, with an average hardness of (784 ± 5) HV0.2, (793 ± 3) HV0.2 and (814 ± 5) HV0.2 for the sintering temperatures of 1200 °C, 1300 °C and 1600 °C respectively. The slightly minimum increase in hardness might be attributed to the partial dissolution of a second-phase triggered by the increase in temperature.