Transmisson electron microscopy of phase composition and lattice misfit in the Re-containing nickel-base superalloy CMSX-10

Phase compositions of matrix and γ′ phase in the third-generation superalloy CMSX-10 containing 6 wt.% Re were measured locally by energy dispersive X-ray spectroscopy in a transmission electron microscope. The corresponding lattice misfits between matrix and γ′ phase were determined by convergent beam electron diffraction. All measurements were performed in dendrites and interdendritic regions. Comparing the as-cast condition to the standard heat treated condition, remarkable enrichments of Re in the γ′ phase of dendrites and segregation of W and Ta in the matrix are detected. After standard heat treatment, an enrichment of Re remains in the matrix of dendrites. This results in differences in amount and sign of lattice misfit. Coherency stresses were calculated using the Finite Elements Method.