Understanding creep of a single-crystalline Co-Al-W-Ta superalloy by studying the deformation mechanism, segregation tendency and stacking fault energy

A systematic study of the compression creep properties a single-crystalline Co-base superalloy (Co-9Al-7.5W-2Ta) was conducted at 950, 975 and 1000°C to reveal influence temperature resulting diffusion velocity solutes like Al, W Ta on deformation mechanisms. Two rate minima are observed all temperatures indicating that mechanisms causing these quite similar. Atom-probe tomography analysis reveals elemental segregation stacking faults, which had formed in γ′ phase during creep. Density-functional-theory calculations indicate fault an associated considerable reduction energy. Since diffuse faster higher temperature, can take place more quickly. This results significantly softening alloy, since cutting precipitate by partial dislocations is facilitated through already early stages confirmed transmission electron microscopy analysis. Therefore, not only smaller fraction responsible for worse properties, but also diffusion-assisted shearing dislocations. The understanding will help future alloy development offering new design criteria.