Intergrowth structure of Laves within μ phases in Co–Al–W base superalloy

• Published in: Journal of alloys and compounds 2020-12, Vol.844, p.155822, Article 155822
• Main Authors: Liu, L.R., Zhou, B.X., Wang, Q.F., Yang, Y.H., Yu, J.J., Sun, B.Z.
• Format: Article
• Language: English
• Subjects: Chromium; Co-Al-W base Superalloy; Displacements (lattice); Electrons; Intergrowth; Laves phase; Microscopes; Molybdenum; Mu phase; Quaternary compounds; Scanning transmission electron microscopy; Substitutes; Substitution; Superalloys; Topologically close-packed phases; Transmission electron microscopy; Tungsten
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2020.155822

In a Co–Al–W base superalloy, two types of topologically close-packed (TCP) phases, μ and Laves phases, were investigated by high-resolution transmission electron microscopy, scanning transmission electron microscopy and energy dispersive X-ray spectroscopy. It is found that an intergrowth structure of Laves within μ phases can be formed and both have a completely coherent interface relationship. With the aid of image simulation, both μ and Laves phases are identified as the quaternary compounds containing Co, Cr, W and Mo. Compared to Co7W6-type μ phase, W1 and W3-sites are the preferred sites of substitution by Mo atoms and Co1-site is a preferred site of substitution by Cr atoms in the quaternary μ phase, leading to the atomic displacement and an alteration of lattice parameter. In contrast to Co2W-type Laves phase, the newly formed quaternary Laves phase can maintain the C14-type Laves structure although Co and W are substituted partially by Cr and Mo respectively. An intergrowth structure of Laves within μ phases has occurred in a Co–Al–W base superalloy, and both μ and Laves phases can be identified as the quaternary compounds containing Co, Cr, W and Mo. [Display omitted] •An intergrowth of Laves within μ phases is formed in Co–Al–W base superalloy.•Laves and μ phases are the quaternary compounds containing Co, Cr, W and Mo.•Mo occupies preferentially W2 and W3-sites in the quaternary μ phase.