Study Of The Dislocation Dynamics In The Plastic Deformation

The influence of the dislocation geometric morphological, interaction with alloys and moving on the material mechanical behavior is extraordinary great. In the plastic deformation, dislocation configuration is related to multiplication and annihilation mechanism, which is dynamical course. The paper uses dislocation dynamics model in Micro-Meso scale to investigate the change of dislocation configuration and its density, and the average dislocation velocity is also discussed. With the model used, the analysis of the characteristics of the serrated yielding has been reported. The main contents are as follows:1) In the single crystal deforming, both the density and the velocity are in fluctuation under the combination of multiplication and annihilation. On the whole, the velocity increases with increasing external stress and temperature, while the density increases with increasing stress and decreasing temperature. Moreover, the result showed that temperature makes the cross slip probability increase, and dislocation configuration evolves from wall to cell. Strain rate makes the cross slip probability decrease, the configuration evolves from cell and wall to high density stacking fault.2) In the static simulation, there is a Cottrell atmosphere around the dislocation core. For the solute volume dilation greater than zero, the atoms gather under the positive dislocation, but overhead the negative one.3) In the dynamical simulation, three types of interactions between dislocation and solutes were obtained:at low external stress, the dislocation is effectively pinned by its condensed solute cloud and hardly slip. At high external stress, the unpinning effect predominates and dislocation moves at high velocity with little solute disturbance. While at the intermediate stress, the aging and unpinning effect takes place alternately and dynamic strain ageing operates, and the dislocation move with bifurcation.4) When the serrated yielding occurs by intermediate stress, as the aging and unpinning effect takes place alternately,both the dislocation density and velocity are in fluctuation state.5) In the simulation, dislocation velocity and pinning force can be affected by the solute concentration and dilation. On the whole, the velocity decrease with increasing solute concentration and dilation, while pinning force increases with their increasing.