Mechanism of dislocation shearing of gamma in fine precipitate strengthened superalloy

Abstract

The dislocation structure of a fine gamma precipitate strengthened nickel base superalloy during steady state creep has been studied. Extensive shearing of gamma particles by partial dislocations, creating stacking faults in both gamma and gamma phases, have been observed in specimens under stresses ranging from 120 to 250 MPa. Detailed analysis of the fault nature and dislocation dissociation revealed that a unit matrix dislocation of a2110 dissociated into two partials of a3112 and a6112. Extrinsic stacking faults were created in both gamma and gamma phases, presumably being created by the movement of the leading a3112 partial, while the movement of the a6112 partial eliminates the stacking fault in the matrix, but leaves a partial dislocation loop around the faulted gamma precipitates.