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- Deformation mechanisms (1) (entfernen)
α(1 0 0) Dislocations are observed in nickel-base superalloys after creep deformation at high temperatures and low stresses. They are formed in the γ/γ´ interfaces by a three step mechanism. First, primary dislocations with Burgers vector α/2(1 0 1) and 60° character are left behind in the interfaces when dislocation loops glide through the γ channels. The 60° dislocations move into edge orientation and react forming secondary dislocations α/2(1 1 0). In the third step, new primary dislocations are knit into the already existing meshes of primary and secondary dislocations, which results in hexagonal misfit dislocation networks consisting of secondary dislocations α/2(1 1 0) and tertiary dislocations α(1 0 0), both of edge type. This self-organisation process is explained by dislocation theory and crystallography.
Creep deformation accelerates when the α(1 0 0) interfacial dislocations enter the γ´ phase. During their climb towards the opposite interface, they attain a characteristic rectangular shape. This shape and the importance of the α(1 0 0) super dislocations for creep deformation are discussed.