Dislocation self-interaction in TiAl:Evolution of super-dislocation dipoles revealed by atomistic simulations

摘要

As one of the fundamental outcomes of dislocation self-interaction,dislocation dipoles have an important influence on the plastic deformation of materials,especially on fatigue and creep.In this work,superdislocation dipoles inγ-TiAl andα_(2)-Ti_(3)Al were systematically investigated by atomistic simulations,with a variety of dipole heights,orientations and annealing tempe ratures.The results indicate that non-screw super-dipoles transform into locally stable dipolar or reconstructed cores at low temperature,while into isolated or interconnected point defect clusters and stacking fault tetrahedra at high temperature via short-range diffu sion.Non-screw super-dipoles inγ-TiAl andα_(2)-Ti_(3)Al exhibit similar features as fcc and hcp metals,respectively.Generally,over long-term annealing where diffusion is significant,60°superdipoles inγ-TiAl are stable,whereas the stability of super-dipoles inα2-Ti3 Al increases with dipole height and orientation angle.The influence on mechanical properties can be well evaluated by integrating these results into mesoscale or constitutive models.