Using C to enhance the wear resistance of AlCrFe2Ni4Ti2 high-entropy alloy via replacing brittle phases by in-situ formed TiC in a matrix with improved ductility

The wear resistance of high-entropy alloy (HEA), AlCrFe2Ni4Ti, can be enhanced by increasing the Ti content, which raises the hardness of the alloy due to the formation of harder phases, including an L21 phase with disordered-BCC nano-precipitates, a eta-Ni3Ti hexagonal phase, and a MgZn2-type Fe2Ti Laves phase. However, these hard but relatively brittle phases have negative influences on the wear resistance of the alloy if their amount exceeds a certain level, especially when large impact forces or large fluctuations in wearing force are involved. In this work, we added carbon to AlCrFe2Ni4Ti2 to reduce the Ti-containing brittle phases and form in situ TiC particles in the metallic matrix with improved ductility. Samples of AlCrFe2Ni4Ti2CX (x = 0, 0.5 and 1.0, in molar ratio) were fabricated by arc melting. The fabricated HEA-matrix with in situ TiC particles showed improved ductility, e.g., the compressive ductility was increased by up to 30%, along with increased ultimate compressive strength, although the yield strength was slightly decreased, compared with the alloy without carbon addition. Wear tests demonstrated that the HEA with in situ TiC particles showed consequently enhanced wear resistance (10%-19% higher). This study demonstrates an effective approach to modify the high-entropy alloy for enhanced wear resistance by eliminating or minimizing Ti-containing brittle phases using carbon to react with Ti, forming in situ TiC particles in a HEA matrix with improved ductility.