On the formation of <010>-dislocations in the gamma'-phase of superalloy single crystals during high temperature low stress creep

The cutting of gamma'-particles by dislocations during shear creep deformation of CMSX 6 superalloy single crystals loaded on the macroscopic crystallographic shear system [110]{111} at T = 1025 degrees C and tau = 85 MPa is analysed using transmission electron microscopy (TEM). The formation of a [010]-dislocation in the gamma'-phase was observed and investigated by means of stereo microscopy, line trace and g.b-analysis. Two gamma-matrix channel dislocations with different Burgers vectors (b) of type a(0)/2[110] jointly shear the gamma'-particle where they form a superdislocation with a total Burgers vector of a(0)[010]. The present paper provides microstructural evidence for this high temperature cutting process. The results are discussed in relation to the evolution of the dislocation structure in the gamma-channels during primary creep. Peach-Koehler forces were calculated to explain the formation of the [010]-dislocation. (C) 1997 Acta Metallurgica Inc.