FINE-STRUCTURE OF ALPHA[011] DISLOCATIONS AND THE MECHANICAL-PROPERTIES OF NIAL IN THE HARD ORIENTATION

The motion of a(011) dislocations is thought to play an important role in the deformation of NiAl single crystals when oriented along a (100 ) crystal direction (''hard'' orientation). in the present work, the s tructure of a(011) dislocations has been determined on several differe nt length scales, using high resolution and weak-beam transmission ele ctron microscopy. The observations indicate that a(011) edge dislocati ons decompose into two separate a(010) dislocations along the edge ori entation, and that the overall shape of a(011) dislocation loops is no n-planar. The embedded atom method has been used to study the energy a nd stability of a(011) edge dislocations, and the effects of the stres s state and temperature on the dislocation core structure and mobility . A possible mechanism for the motion of a(011) dislocations will be d iscussed, and related to the fracture and deformation behavior of NiAl in the hard orientation.