Free energy of dislocation nucleation from grain boundary at finite temperature

有限温度における粒界からの転位核生成に関する自由エネルギー

Tirtom, I.; Wang, Y.*; 尾方 成信*

Tirtom, I.; Wang, Y.*; Ogata, Shigenobu*

Nanocrystalline materials are single-phase or multi-phase polycrystals, with the approximately 1-100 nm crystal size at least in one dimension. Bulk nano crystalline metals, which are approximately equiaxed crystallites (3D), show different deformation behavior than their bulk form under the tensile testing. Ideal nanostructured materials, characterized by a high density of interfaces and nearly defect-free grain interiors and a lack of the necessary mobile dislocations to support the plastic deformation. This study focus on mechanistic models that seek to computationally determined activation energy and volume associated with the strain rate sensitivity of nanocrystalline metals in a way that comparable with the experimental time scale. The minimum free energy path searching at finite temperature and accelerated molecular modeling techniques are applied to the atomic grain boundary model of FCC Cu. Activation volumes are calculated from the activation free energy determined from computer simulations. It is expected that the activation volumes will decrease monotonically with increasing loading.