Minimum interface misfit criterion for the precipitation morphologies of TCP phases in a Ni-based single crystal superalloy

The precipitation and growth morphology of topologically close-packed (TCP) phases in a Re-containing Ni-based single crystal superalloy during thermal exposure were studied. The alloy was found to develop acicular-shaped coherent μ phase particles along γ directions of the matrix after exposure at 950 °C. P phase precipitates were found to form with increased time and at higher temperatures, and in different morphologies, including acicular shaped particles along γ and γ directions, and plate-like particles in {110}γ planes of the matrix. The different P phase precipitates were found to have different lattice constants and different lattice correspondences with the matrix. The μ phase precipitate was also found to have different lattice correspondences with those reported in the literature. The multiplicity of lattice correspondences for the same TCP phase is attributed to the different lattice parameters, which render the precipitates to have different coherency relationships with the matrix. [Display omitted] •The lattice correspondences of the topologically close packed μ and P phases were determined.•Acicular μ phase needles were found to form along γ with 1.6% misfit with the matrix.•The P phase was found to form in two different morphologies and lattice correspondences.•A minimum interface misfit criterion is established for the formation of various morphologies.