Shock Hugoniot of an equiatomic high-entropy alloy NbMoTaW up to 143 GPa

Abstract

The equations of state and phase stabilities of high-entropy alloys (HEAs) under high-pressure and high-temperature conditions are of paramount importance for engineering applications. However, few reports exist on the high-pressure–temperature properties of the HfNbMoTaWV HEA system. Herein, we synthesized a NbMoTaW HEA using the vacuum arc melting method and measured its Hugoniot up to 143 GPa and ∼6200 K. A linear relationship [US = 2.61 (7) + 1.59 (5) UP] between the shock (US) and particle (UP) velocities was observed for UP > 0.7 km/s, suggesting that the NbMoTaW HEA is likely stable within the pressure–temperature range of the current study. Using the Debye–Mie–Grüneisen model and Birch–Murnaghan equation of state (EOS), we discussed the EOS of the NbMoTaW HEA. The bulk modulus (K0) and its pressure derivative (K0′) were determined to be 238 GPa and 3.3, respectively. We also found that the Hugoniot compression curve of the NbMoTaW HEA could be evaluated using the mixture rules with the Hugoniot data of the compositional elements.