Study on mechanical and tribological performances of novel V-containing AlCrFeNiV high-entropy alloys and related self-lubricating composites

High-entropy alloys have been regarded as a groundbreaking development in the field of materials science since their discovery, as they possess extraordinary properties that surpass those of conventional engineering materials. Their exceptional properties are the consequence of their unique multi-element composition and high configurational entropy, which stabilize simple solid solution phases and reduce the formation of brittle intermetallic compounds, making them suitable for extreme environments. The addition of vanadium to HEA aims to enhance their thermal stability, facilitate the dispersion of nanoparticles, increase their strength at elevated temperatures, reduce their susceptibility to corrosion, and confer additional features such as magnetism and radiation resistance.

This work analyzes Al_0.5CrFeNiV_x-based HEA and their composites' phase composition, microstructure, mechanical characteristics, high-temperature tribological behavior, and wear processes. Arc-melted Al_0.5CrFeNiV_0.5 HEA exhibits a hardness of 520 HV and a compressive strength of 2476 MPa at room temperature, both of which remain stable up to 600 °C. Its friction coefficient remains steady at 0.4–0.5 over a temperature range from room temperature to 800 °C. The wear of the HEA increases monotonically with temperature and accelerates above 600 °C due to oxidation and surface deterioration.

The study further explored the effects of varying vanadium (V) content on Al_0.5CrFeNiV_x (x = 0.25-1.0) HEA. Increasing V concentration changed the microstructure from a single-phase body-centered cubic (BCC) to a dual-phase BCC/Laves structure with V-rich precipitates and dark secondary phases. This structural transition improved solid solution strengthening and phase stability, increasing hardness from 520 HV at V0.25 to 608 HV at V1.0 and compressive strength from 2476 MPa to 3241 MPa. Although mechanical improvements were made, fracture strain decreased from 34% to 22%, demonstrating that V0.5 and V0.75 compositions provide a balanced strength-ductility trade-off for high-temperature applications. V also made complex oxide layers, mostly vanadium oxides, a protective coating that increased thermal stability and wear resistance. Notably, at 700 °C, the alloy with V1.0 exhibited the lowest wear rate (18 × 10⁻⁵ mm³/Nm) and friction coefficient due to oxidative melt wear triggered by the low melting point of V₂O₅.