| Summary: | Microstructure, mechanical properties, wear resistance, corrosion and corrosive wear resistance of AlCrFeNiW<sub>x</sub> (x = 0, 0.1, 0.2, 0.3 and 0.4) medium-entropy alloys (MEAs) prepared by vacuum arc melting process were investigated. Results of the study show that the microstructure of as-cast AlCrFeNiW<sub>x</sub> alloys is composed of one disordered Fe-Cr rich BCC phase (A2) and one ordered NiAl-rich (B2) phase when x = 0 and 0.1; W particles appear when x ≥ 0.2. Hardness and strength of AlCrFeNi alloy are markedly increased by the W addition. The strengthening mechanisms include solid-solution strengthening, nano-sized precipitation strengthening and second phase strengthening. The excellent ductility of AlCrFeNi is retained with minor W addition (x ≤ 0.2) but it considerably declines as more W is added, resulting from the precipitation of excessive large-sized W particles. W addition improves the pitting resistance and passivation property of AlCrFeNi HEA in 3.5 wt. % NaCl solution. It is shown that AlCrFeNiW<sub>0.3</sub> possesses the highest corrosion resistance, as reflected by the highest E<sub>corr</sub> and the lowest I<sub>corr</sub>. Tungsten notably enhances the resistance of this HEA to wear and corrosive wear. AlCrFeNiW<sub>0.4</sub> with the highest strength and hardness exhibits the lowest wear volume loss under both dry and corrosive wear conditions.
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