In this article, we present a time-dependent deformation mechanism for f.c.c. metal single crystals in which the resulting deformation is produced by the cumulative effect of dislocation glide in each slip systems. This model presents a self-consistent micromechanical approach where both the time-dependent and independent deformations are linked together. The time-dependent mechanism considers that additional glide of a dislocation segment in a given slip system results by the net motion of forest obstacles at which the segment is detained. The net obstacle motion is then related to the dislocation climb rate. We consider that the obstacle velocity is a function of the rate at which jogs on the gliding plane and the forest plane meet. This approach requires the jog density evolution to be followed for all systems. Two main sources of jog production are considered in this article: cross-slip and dislocation intersection, both depending on the loading history of the material. The predictions of the theory are compared to creep tests. These tests are especially suited to studying the contribution of the time-dependent part since the time-dependent portion remains unaltered during testing. The proposed model captures the creep rate dependence with stress as well as several key micromechanical features such as the dislocation density evolution, the reduced creep rate for high initial dislocation density and the effect of stacking fault energy.
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Ceramics and Composites
- Polymers and Plastics
- Metals and Alloys