Effect of Mo additions on microstructure and tensile behavior of a Co–Al–W–Ta–B alloy at room temperature

Phase constitutions, microstructures and room-temperature tensile behavior of Mo-doped Co–9Al–(9 − x)W–2Ta–0.02B–xMo alloys (where x = 0, 2, 4, 6, 9 at.%) are investigated. After aging treatment, the microstructure is composed of γ matrix and nanoscale cuboidal γ′ precipitates, with Mo contents of 0–4 at.%; however, a needle-like cellular κ-Co3Mo phase is additionally found in the γ′/γ microstructure, with Mo contents of 6–9 at.%. The pure γ′/γ microstructure exhibits better room-temperature tensile strength and elongation than the γ/γ′/κ microstructure.