Abstract
Abstract We present atomistic simulations of the crack tip configuration in single crystals and bicrystals of B2 NiAl. The simulations were carried out using molecular statics and embedded-atom potentials. The cracks are stabilized near a Griffith condition and the process of dislocation emission from the crack tip was studied. The behaviour of a semi-infinite crack was studied under mode I loading for different crack tip geometries. While [001](110) and [110](110) mode I cracks cleave near the Griffith value of loading, dislocation emission is observed from [010](100) and [011](100) crack tips. Dislocations emitted from the [011](100) crack are observed to move far away from the tip. However, the dislocations emitted from the [010](100) crack are observed to be considerably less mobile and they remain in the immediate vicinity of the crack tip after emission. The results indicate that for some orientations the fracture process in NiAl has dislocation emission characteristics typical of ductile fracture. ...
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