Fine structure of a〈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 structure of a〈011〉 dislocations has been determined on several different length scales, using high resolution and weak-beam transmission electron microscopy. The observations indicate that a〈011〉 edge dislocations decompose into two separate a〈010〉 dislocations along the edge orientation, and that the overall shape of a〈011〉 dislocation loops is non-planar. The embedded atom method has been used to study the energy and stability of a〈011〉 edge dislocations, and the effects of the stress state and temperature on the dislocation core structure and mobility. A possible mechanism for the motion of a〈011〉 dislocations will be discussed, and related to the fracture and deformation behavior of NiAl in the hard orientation.