Grain Boundary Sliding in High-Purity Aluminium Bicrystal and Al–Cu Solid Solution Bicrystal during Plastic Deformation

Grain boundary sliding and deformation of zone near grain boundary at various constant temperatures under constant load were observed in high-purity aluminium bicrystals and Al–Cu solid solution bicrystals, and then sliding at grain boundary during a constant rate heating under various constant compressive stresses of 20 to 35 kg/sq.cm were observed in high-purity aluminium bicrystals. The grain boundary sliding vs. time curve changes stepwise in the constant load test. When the amount of sliding increased, it was apparent that the sliding was accompanied by shear deformation in the narrow region adjacent to the boundary. It is considered, that the grain boundary migration is caused by the recovery of the deformation in the band region adjacent to the boundary. The addition of 0.2% Cu greatly affected the grain boundary sliding of pure aluminium, but the addition of 0.2∼0.5% Cu did not. The grain boundary sliding during the free compressive deformation was caused by the misorientation of the component crystal for external stress, and it has primarily no relation with the compressive stress on the whole. The activation energies for grain boundary sliding were calculated from the slope of the straight lines in the relative figure of temperature vs. sliding rate at the initial stage of the sliding. The behaviour of the deformation layer in the region adjacent to the grain boundary affected strongly the difference in activation energy for the grain boundary sliding by the compressive direction.