GAMMA'-PHASE CUTTING DURING HIGH-TEMPERATURE SHEAR CREEP DEFORMATION OF CMSX6 SUPERALLOY SINGLE-CRYSTALS

The cutting of gamma'-particles during shear creep deformation on the macroscopic crystallographic {111} [110] shear system at T = 1025 degrees C and tau = 85 MPa is studied using transmission electron microscopy (TEM). It is observed that two matrix channel dislocations with different Burgers vectors join and form a superdislocation which cuts through the gamma'-phase. This superdislocation moves on the (101)-plane and has a total Burgers vector of a(0)[010]. The results of the present investigation can be rationalized on the basis of two core configurations of this superdislocation: (i) A compact core edge type superdislocation forms and moves through the gamma'-phase by noncompact slip. (ii) Two 60 degrees-superpartials with Burgers vectors of type (a(0)/2) [01 $$($) over bar 1] and (a(0)/2) [011] which are associated with the (111)- and the (1 $($) over bar$$ 11)-plane, respectively, move by a combined process of glide and climb. The experimental TEM images do not allow to differentiate between these two scenarios.