Effect of Ti Content Upon the Microstructure, Mechanical Properties and Wear Behaviors of TixNi0.6CoFe1.4Nb0.05 Medium-Entropy Alloys

The effects of Ti content on the microstructural evolution, mechanical properties and wear behaviors of TixNi0.6CoFe1.4Nb0.05 (x = 0, 0.1 and 0.2, in molar ratio) medium-entropy alloys (MEAs) were systematically studied. The results show that all alloys exhibit a typical duplex microstructure consisting of BCC and FCC phases. With the increase of Ti content, the fracture strength first increases and then decreases, while the fracture elongation monotonically decreases. Among them, Ti-0.1 MEA shows the excellent mechanical properties with the hardness, ultimate tensile strength and total elongation of 605.1 +/- 11.5 HV, 1075.4 +/- 58.2 MPa and 19.2 +/- 3.1 pct, respectively. The wear behaviors show that both the coefficient of friction and wear weight loss decrease with the increase of Ti content. The improvement of wear resistance is mainly attributed to the increase of alloy hardness. The wear mechanism of TixNi0.6CoFe1.4Nb0.05 MEAs are the abrasive wear and oxidation wear.