15. Nucleation and Reaction of Dislocations in Some Metals and Intermetallic Compound TiAl

The shear deformation in selected metals and intermetallic compound TiAl under different conditions was investigated using molecular dynamics (MD) simulation with many-body interatomic potentials. The atomic-scale details of the dislocation nucleation were simulated with the GPU implementation of our Para MD program. For the homogeneous nucleation in perfect lattice, as the lattice strain increases, strain localization occurs during which the strain condenses gradually on a few lattice planes where the nucleation is finally achieved. The dislocations on different slip planes in the same slip system can react with each other if the slip planes are only a few interplanar-spacings apart, forming a variety of defects including vacancies, interstitial atoms and their clusters, small dislocation loops, etc., depending on the distance between the slip planes and the characteristics of the reacting dislocations. It was shown that the C1060 GPU has a substantial acceleration on MD simulation compared with conventional CPU, indicating therefore a method to reduce the total cost of MD simulations; however, for ultra-large atomic systems, the relatively small memory capacity on C1060 hinders further increase of the simulation size beyond a few million atoms, therefore expansion of the GPU memory, which meanwhile reduces the communication burden given the same simulation size, rather than the number of cores is more important for such simulations.