DISLOCATION REACTIONS AT GAMMA GAMMA'-INTERFACES DURING SHEAR CREEP DEFORMATION IN THE MACROSCOPIC CRYSTALLOGRAPHIC SHEAR SYSTEM (001)[110]OF CMSX6 SUPERALLOY SINGLE-CRYSTALS AT 1025-DEGREES-C/

Reactions between dislocations and between dislocations and gamma'-par ticles are studied in CMSX6 single crystals which were subjected to sh ear creep deformation in the macroscopic crystallographic shear system (001)[110] at T = 1025 degrees C and tau = 85 MPa, Experiments compri se high resolution shear creep testing and transmission electron micro scopy. Emphasis is placed on the formation of dislocation networks and on rafting. The number of activated crystallographic glide systems in creases during creep. A number of dislocation reactions which rational ise the features of the observed dislocation networks is identified. I n secondary creep a (microscopic) slip system of type (001)[110] start s operating. Moreover experimental evidence for a new type of interact ion between interface dislocations and the coarsening process of the g amma'-particles is provided. The explanation is based on three element s: (i) the stress fields of the interface dislocations result in local differences in chemical potential; (ii) the interface dislocations pr ovide pipe diffusion paths from one gamma'-surface to another; (iii) d islocation climb directly and indirectly (tube/sandbox-analogon) contr ibutes to this interaction. (C) 1998 Elsevier Science S.A. All rights reserved.