Observation par met d'interactions de dislocations aux interfaces γ/γ′ d'un superalliage biphase

Abstract

Samples of the two-phase superalloy CMSX-2 are deformed by dynamical compression tests (1%, 900°C) along the 〈001〉 direction and observed in TEM. Some stacking faults and dislocations are identified by the numerical simulation technique of the contrasts in the two-beam dynamical theory. Results indicate the simultaneous presence, within the γ′ precipitates, of three slip systems: (111), 〈110〉; (111),〈112〉; (001),〈100〉. At the precipitate/matrix interfaces, identified dislocations have Burgers vectors (100), 1 2 〈110〉 and 1 6 〈112〉. Dislocations with Burgers vectors 1 2 〈112〉 have not been observed. Some shear mechanisms of the precipitates related to these slip systems are discussed, as well as the evolution of the dislocation reactions when the slip propagates. The analysis of an interfacial dislocation configuration leads to the conclusion that a ribbon of antiphase boundary with a displacement vector 1 2 〈112〉 is sometimes present in the γ′ phase. This ribbon is limited on one side by the interface γ γ′ and on the other side by a Shockley dislocation connected to a superlattice intrinsic stacking fault (SISF). A method is applied to evaluate the SISF energy. It makes benefit from the accidental presence of elastically interacting partial dislocations with Burgers vectors 1 3 〈112〉.