Screw dislocation core interaction with C or Nb in γ-TiAl: A multiscale study

The solute strengthening caused by the interaction between dislocations and solutes in random solid solution alloys has already been investigated widely provided that the solutes outside the dislocation core interact through nominally elastic interactions. However, the topological variation of dislocation core due to the solute segregation can influence the strengthening of system. We investigate the dislocation core reconstruction with solute C and Nb and their effects on dislocation glide in γ-TiAl by multiscale QM/MM scheme due to the long-range elastic field of a dislocation. The solutes doping in dislocation core region can influence the core energy and eventually cause a violation of Frank's rule. The contribution analysis of lattice distortion and chemical effect between dislocations and solutes is further investigated. The energy barriers of constriction and transition state in pure γ-TiAl and under solutes environment in the process of external stress reveal electronically the effects of alloying elements and heterogeneous mechanisms on cross-slip process. The carbon diffusion along and across dislocation core by the CI-NEB method are also investigated.