High-entropy alloy (HEA) coatings of CoCrFeNiTiAl_x (x = 0, 0.5, 1, 1.5, 2) were prepared on the surface of AISI1045 steel by laser cladding. The effects of the Al content on the microstructure, composition, phase constitution, and wear and corrosion resistance of the coatings were investigated. The results showed that when increasing the Al element content from 0 to 0.5, the phase constitution of the CoCrFeNiTiAl_x coating changed from a single Face-centered cubic (FCC) phase to Body-centered cubic 1 (BCC1) and Body-centered cubic 2 (BCC2) phases, with a small amount of Laves phase, which obviously improved the friction and corrosion resistance of the coating. With further enhancing of the Al content, the amount of BCC1 phase increased, while the BCC2 phase and the Laves phase decreased. The CoCrFeNiTiAl₂ HEA coating transformed into a single BCC1 phase, with retrogressive wear and corrosion resistance. It was found that the Al_0.5 alloy coating exhibits excellent wear resistance, high hardness, and corrosion resistance in a 3.5 wt.% NaCl solution. Furthermore, the effect of the Al content on the microstructure, phase, and the relating properties of the CoCrFeNiTiAl_x HEA coatings is also discussed.

Semi-solid processing (SSP) is a popular near-net-shape forming technology for metals, while its application is still limited in titanium alloy mainly due to its low formability. Recent works showed that SSP could effectively enhance the formability and mechanical properties of titanium alloys. The processing parameters such as temperature and forging rate/ratio, are directly correlated with the microstructure, which endow the alloy with different chemical and physical properties. Specifically, as a key structural material for the advanced aero-engine, the burn resistant performance is a crucial requirement for the burn resistant titanium alloy. Thus, this work aims to assess the burning behavior of Ti14, a kind of burn resistant alloy, as forged at different semi-solid forging temperatures. The burning characteristics of the alloy are analyzed by a series of burning tests with different burning durations, velocities, and microstructures of burned sample. The results showed that the burning process is highly dependent on the forging temperature, due to the fact that higher temperatures would result in more Ti₂Cu precipitate within grain and along grain boundaries. Such a microstructure hinders the transport of oxygen in the stable burning stage through the formation of a kind of oxygen isolation Cu-enriched layer under the burn product zone. This work suggests that the burning resistance of the alloy can be effectively tuned by controlling the temperature during the semi-solid forging process.