Mechanical, wear and corrosion properties of refractory high-entropy alloys based on different Al and Hf contents

TiZrHfNb-based refractory high-entropy alloys (RHEAs) possess promising comprehensive properties, yet the high cost of Hf restricts their engineering applications. In this study, Ti 30 Zr 30 Hf (16-x) Nb 24 Al x (x = 0, 2, 4, 6, 8) RHEAs prepared via vacuum arc melting were investigated. This study aimed to clarify how low-cost Al substitution for Hf affects the microstructure, wear resistance and corrosion resistance of the alloys. The results showed that the alloys were composed of equiaxed grains. With increasing Al content, the average grain size increased from 260.81 μm to 298.96 μm and then decreased to 209.93 μm. When the Al content reached 2 at.%, a coexistence of BCC and B2 phases was observed. Appropriate addition of Al (x ≤ 4 at.%) promoted the balance between the yield strength and ductility of the alloys. The primary strengthening mechanism was solid-solution strengthening. Following the trend of mechanical properties, the Ti 30 Zr 30 Hf 14 Nb 24 Al 2 alloy exhibited enhanced wear resistance, reflected in the lowest wear volume and wear rate. Compared with the Ti 30 Zr 30 Hf 16 Nb 24 alloy, these values were reduced by 50.4% and 50.5%, respectively. It also exhibited a low corrosion current density (0.03 μA cm −2 ) and a broad passivation region (ΔE = 1.513 V). This work provides valuable guidance for the preparation of TiZrHfNb RHEAs with excellent mechanical properties, wear and corrosion resistance.