TOPOLOGICALLY CLOSE PACKED PHASES IN AN EXPERIMENTAL RHENIUM-CONTAINING SINGLE CRYSTAL SUPERALLOY

The kinetics, morphology and composition of the formation of TCP phases in an experimental alloy containing no tungsten is studied. At high temperature P phase forms after 20 h, whereas below 950°C the phases p and R occur. At lower temperatures a polycrystalline form of cr phase is observed which is meta-stable but acts as a nucleation site for the other phases. The phase occurrence and compositions are compared with a thermodynamic model using a rhenium-containing database, and reasonable agreement is found for the P, R and cs phases. However the model underestimates the stability of the p phase.