Index of content:
Volume 35, Issue 11, November 2009
- LOW-TEMPERATURE PHYSICS OF PLASTICITY AND STRENGTH
35(2009); http://dx.doi.org/10.1063/1.3266927View Description Hide Description
The influence of the grain size on the dislocation interaction mechanisms that control the deformation of aluminum in the temperature range is studied. For this, samples of coarse-grain (CG) and ultrafine-grain (UFG) aluminum obtained by equi-channel angular pressing were deformed by stretching at constant rate as well as in the rate-cycling regime along the deformation curve. The effects of temperature on strain hardening and the stain-rate sensitivity of the flow stress of CG and UFG material are compared. It is shown by means of thermal-activation analysis of the experimental data that the dependence of the rate sensitivity parameter on the grain size and temperature of the aluminum is explained by a change of the dislocation mechanisms controlling the plastic deformation of the aluminum. In the temperature interval the plastic deformation of the UFG and CG aluminum is due to a single mechanism of intersection of forest dislocation. In the interval for CG and for UFG aluminum the increase in the parameter is explained by the activation of the mechanism of transverse slip of dislocations. At temperatures above the high rate sensitivity of the stress and low rate of strain hardening of UFG aluminum can be due to the activation of the grain-boundary diffusion and grain-boundary slip-through.