A statistical TEM investigation of dislocation channeling mechanism in neutron irradiated zirconium alloys.

Plastic deformation in irradiated zirconium alloys occurs in a very heterogeneous manner at the grain scale by the clearing up of radiation-induced prismatic loops by gliding dislocations and the channeling of these dislocations inside narrow bands of the grain. A statistical TEM investigation of this mechanism has been performed on neutron irradiated recrystallized Zr alloys tested at 350 degreesC. Due to the strong anisotropy of plastic deformation, different loading conditions have been investigated. It is shown that for transverse tensile tests and closed end burst tests, only basal channels are observed, whereas for axial tensile tests, prismatic and pyramidal channels are observed. This phenomenon can be understood in terms of texture and interactions between dislocations and irradiation induced loops. From Schmid factor calculations, we have also been able to prove that irradiation leads to a higher increase of critical resolved shear stresses for prismatic and pyramidal slip systems than for basal slip system