Intergrowth of C phase within μ phase in a Re-containing Ni-base single crystal superalloy

Precipitation of topologically close-packed phases in a Re-containing Ni-base single crystal superalloy was studied under elevated temperature by in situ transmission electron microscopy. Above 1150 °C, a new intergrowth structure called C phase was found within μ phase with a defined crystallographic orientation relationship. Elements mapping analysis reveals that C phase has a similar element composition as μ phase, but contains a lower level of Cr, W and Re. With increasing temperature, the proportion of C phase increases gradually. At 1250 °C, C phase becomes the dominant precipitate. It is demonstrated that C phase is more thermodynamically stable than μ phase above 1150 °C that leads to an intergrowth pathway from μ phase to C phase.