Shen P.-KLiu H.-CHuang C.-YYen H.-WYeh J.-WTsai C.-W.HUNG-WEI YEN2022-03-222022-03-22202210445803https://www.scopus.com/inward/record.uri?eid=2-s2.0-85122615489&doi=10.1016%2fj.matchar.2021.111713&partnerID=40&md5=e14620e966b9379467e68f0b510f6150https://scholars.lib.ntu.edu.tw/handle/123456789/598385Medium-entropy alloys (MEAs) have attracted considerable research attention because of their excellent mechanical properties. In these, the γ’ phase has been utilized as a strengthening phase. However, the η phase has not been widely investigated. Herein, we explain the precipitation behavior of the η phase in a non-equimolar CoCrNiTi MEA. The MEA adopts a face-centered cubic (FCC) matrix upon Ni3Ti η phase precipitation. Various characterization techniques were used to analyze the microstructure, phase structure, and phase composition of the as-prepared MEA. The grain size and volume fraction of the η phase were ~ 70 nm and ~ 35%, respectively. The FCC-η interface exhibited semi-coherence, adopting an interplanar angle of 23°. Upon precipitation strengthening, the MEA exhibited a yield strength of ~1.7 GPa, an ultimate tensile strength of ~2 GPa, and an elongation of ~2.87%. This work facilitates a novel approach to ultrahigh-strength alloy production. ? 2022 Elsevier Inc.DuctilityMedium-entropy alloysNanostructured materialsPrecipitationBinary alloysChromium alloysCobalt alloysDensity (specific gravity)EntropyHigh strength alloysHigh-entropy alloysMicrostructureTensile strengthTitanium alloysCharacterization techniquesCubic matrixFace-centred cubicGrainsizeMedium entropyMedium-entropy alloyMicrostructures and mechanical propertiesPhase precipitationsPrecipitation behaviourStrengthening phasisPrecipitation (chemical)journal article10.1016/j.matchar.2021.1117132-s2.0-85122615489