SHAO-PU TSAILin, Yu-ChuanYu-ChuanLinYou, Jhen-DeJhen-DeYouTsai, Chung-ChihChung-ChihTsaiHsueh, Chun-HwayChun-HwayHsueh2026-01-152026-01-152026-01-1509258388https://www.scopus.com/record/display.uri?eid=2-s2.0-105024919013&origin=resultslisthttps://scholars.lib.ntu.edu.tw/handle/123456789/735355This study investigates the microstructural evolution and mechanical performance of magnetron co-sputtered (CoCrNi)100–2xNbxVx (x = 0, 1, 2, 2.5, 3 and 4) medium entropy alloy films (MEAFs) by systematic and iterative tuning of deposition parameters. The films exhibited phase transitions from face-centered cubic (FCC) solid solution with nanotwins for x = 0, 1, and 2 to dual-phase FCC/hexagonal close-packed ε martensite structures for x = 2.5, followed by progressive amorphization for x = 3 and 4 due to severe lattice distortion and further microstructural refinement by twinning and ε martensite. Nanoindentation and micropillar compression tests revealed that the best wear resistance, with a hardness of 10.17 GPa, yield strength of 5.45 GPa, and enhanced damage tolerance, was achieved at x = 2.5. These optimal mechanical properties were attributed to synergistic solid-solution-, grain refinement-, FCC twinning- and ε martensite-strengthening. Our results demonstrate the efficacy of Nb/V co-doping in tailoring CoCrNi MEAFs for high-strength tribological applications.falseFCC solid solutionMedium entropy alloy filmsMicropillar compressionNanoindentationε martensitejournal article10.1016/j.jallcom.2025.1856122-s2.0-105024919013