New configuration of a [001] superdislocation formed during high-temperature creep in the γ′ phase of a single-crystal superalloy TMS-138

A new configuration of a superdislocation in the γ′ phase of a fourth-generation single-crystal TMS-138 superalloy was found after creep rupture in a [001] tensile test at 1150 °C and 137 MPa. The segments of the superdislocation lie in four directions, i.e., [110], [110], [100], and [010], strictly on a (001) plane with a Burgers vectorb= [001]. This superdislocation is pure edge in character and does not dissociate into superpartials. Microstructural evidence shows that this kind of superdislocation is formed by combination of two interfacial dislocations with different Burgers vectors, i.e., 1/2[011] + 1/2[011] → [001].