Search

A series of TiZrV 0.5 Nb 0.5 Al x refractory high entropy alloys were prepared by arc-metling, aiming to solve the problems of high density, poor oxidation and wear resistance of refractory high entropy alloys at elevated temperature. The microstructure, mechanical and tribological properties were investigated. The results indicate that the increase in Al addition could promote precipitation of Laves phase in the BCC matrix, thus regulation the mechanical properties. The tribology behavior is strongly dependent on the temperature. Below 400 °C, the wear mechanism is dominated by mechanical wear. In this case, the TiZrV 0.5 Nb 0.5 Al 0.25 alloy with high strength and good ductility at the same time, exhibits optimal wear resistance. When the temperature increases above to 600 °C, the coefficient of friction and the corresponding wear rate dramatically decrease with Al addition, which could be attributed to the preformed formation of dense and stable oxide glazed-layer before wear. Accordingly, the main wear mechanism changes from mechanical wear to oxidation wear. This study provides an effective strategy for improving wear resistance and oxidation resistance of refractory high entropy alloys in a wide temperature range. • Al-containing alloys hardly wear at 600 °C and 800 °C. • The high temperature worn surface of Al-containing alloy has a dense oxide layer. • The Al0.25 alloy has unique needle-like Laves phase and the best wear resistance. [ABSTRACT FROM AUTHOR]

The wear behaviors of γ-TiAl alloy with two typical microstructures, i.e., the lamellar colony microstructure (denoted as the HIPed sample) and the fine equiaxed microstructure (denoted as the heat-treated sample), were thoroughly studied during dry sliding test to resolve the microstructural feature dependence of wear mechanisms. Special efforts have been made to the subsurface stability during sliding by using electron backscatter diffraction (EBSD) techniques. It is demonstrated that both cases present a similarity in the friction coefficients but a disparity in the wear loss. The lower wear loss was achieved in the case of HIPed sample. This can be attributed to the various directions in the local strain induced by plastic deformation during sliding, the crystallographic structure and the coherent interface in the lamellar colony, leading to high resistance ability to the wear. For the case of heat-treated sample, the high plastic deformation ability in the α 2 grains along the surface and the equiaxed morphology generate to high ability to plastic deformation and sliding during friction, contributing to the high wear loss. However, the heat-treated sample presents a high subsurface structure stability according to the local misorientation analysis. The present results provide new information on wear mechanisms of γ-TiAl alloy and may offer a method to enhance its wear resistance by tailoring the microstructural features. • The wear loss in a dry sliding of a γ-TiAl alloy is evidenced to connect with microstructural feature. • Special efforts have been made to the subsurface stability during sliding by using EBSD techniques. • The lower wear loss was achieved in the case of the lamellar colony microstructure. • The fine globular microstructure presents a high subsurface structure stability. [ABSTRACT FROM AUTHOR]