Dislocations of a<100> type were observed in Ni-base superalloys after creep deformation at high temperatures and low stresses. They were formed in the γ/γ′ interfaces by a three step mechanism. First, primary dislocations with Burgers vector a/2<101> and 60° character were 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 a/2<110>. In the third step, new primary dislocations were knit into the already existing meshes of primary and secondary dislocations, which results in hexagonal misfit dislocation networks consisting of secondary dislocations a/2<110> and tertiary dislocations a<100>, both of edge type. This self-organisation process was explained by dislocation theory and crystallography. Creep deformation accelerates when the a<100> 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 a<100> super dislocations for creep deformation were discussed.

<100> Dislocations in Nickel-Base Superalloys - Formation and Role in Creep Deformation. T.Link, A.Epishin, M.Klaus, U.Brückner, A.Reznicek: Materials Science and Engineering A, 2005, 405[1-2], 254-65