Evolution and analysis of TCP phase in a single crystal nickel-based superalloy containing Re during aging

Abstract

By means of the aging treated for longer time at 1100 °C and microstructure observation, an investigation has been made into the evolution of TCP phase in a superalloy. Results show that the elements W and Re may promote the precipitation of TCP phase in the superalloy. After aged for longer time at 1100 °C, TCP phase is precipitated in the form of the slice-like along {111} planes and 〈110〉 orientation, and the TCP phase is determined as μ phase. The observed strip-like μ phase may be at the angle of 60° or vertical to each other on the different crystal planes. The slice-like μ phase coarsens gradually as the aging time prolongs, and the groove appears in the two sides of the strip-like μ phase until the dissolving up to abruption, in the further the μ phase are transformed into the spheroidized morphology. The free energy of the elements congregated during aging reduces with the increase of the element Re, which makes that the strip-like μ phase coarsens and the unevenness feature appears in the interfaces of the μ/γ′ phases. In the further, the additive pressure is generated in the regions with the smaller curvature radius to enhance the chemical potential of the solute elements in the μ phase. This is thought to be the main reason of resulting in the gradual decomposition and spheroidized of the μ phase.