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 gamma matrix and nano-scale cuboidal gamma' precipitates, with Mo contents of 0-4 at.%; however, a needle-like cellular kappa-Co3Mo phase is additionally found in the gamma'/gamma microstructure, with Mo contents of 6-9 at.%. The pure gamma'/gamma microstructure exhibits better room-temperature tensile strength and elongation than the gamma/gamma'/kappa microstructure. (C) 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.