Understanding the influence of Ti content on mechanically alloyed and sintered CoCrFeNiTix high entropy alloy

The influence of a wide range of Ti content on the microstructure and properties of CoCrFeNiTi x alloy prepared by mechanical alloying and spark plasma sintering was investigated. The content of Ti ranged from x = 0.44-2.15. A gradual change in the phase composition from sole FCC solid solution to fully intermetallic alloy, comprising (Co, Ti)-rich Laves and (Fe, Cr)-rich σ phases, was observed during the increasing Ti content. The Ti showed major FCC solid solution strengthening at 10 at.% and secondary phase strengthening after the partial formation of intermetallic phases at the content of 15 at.%, reaching compressive yield strength of 2157 ± 70 MPa and hardness of 968 ± 10 HV1. Higher amounts of Ti led to further strengthening, increasing the hardness at the expense of ductility. The wear resistance followed the hardness and increased with Ti content, reaching 2,7⸱10 -5 mm 3 ⸱N -1 ⸱m -1 for the CoCrFeNiTi 2.15 . The Ti content also affected the mechanism of wear shifting from mainly adhesive to abrasive wear, showing the presence of oxide debris and cracks, directly pointing to oxidation wear and thermal fatigue.