Dynamics of grain boundaries under applied mechanical stress

Recent results of experimental research into stress-induced grain boundary migration in aluminum bicrystals are reported. Boundary migration under a shear stress was observed to be coupled to a lateral translation of the grains for planar symmetrical 〈100〉 tilt boundaries. This coupling proved to be the typical migration mode of any 〈100〉 tilt boundary, no matter whether low- or high-angle, low Σ CSL coincidence or non-coincidence boundary. The measured ratios of normal boundary motion to the tangential displacement of grains are in an excellent agreement with theoretical predictions. The migration-shear coupling is also observed for asymmetrical 〈100〉 boundaries. Measurements of the temperature dependence of coupled boundary migration revealed that there is a specific misorientation dependence of migration activation parameters. Grain boundaries can act during their motion under the applied stress as sources of lattice dislocations that leads to the generation and growth of new grains in the boundary region. The rate of stress-induced boundary migration decreases with increasing solute content in aluminum. Both the migration activation enthalpy and the pre-exponential mobility factor were found to increase with rising impurity concentration.