抄録
Sliding at grain boundary and shear of zone near grain boundary during a constant rate heating under various constant shear stresses of 10,000 g/sq.cm to 40,000 g/sq.cm were measured in high-purity aluminium bicrystals (99.999%) with a boundary misorientation angle of 26 deg. The amount of grain-boundary sliding increased with increasing shear stress up to 20,000 g/sq.cm, but when the stress increased to 30,000 g/sq.cm or 40,000 g/sq.cm, the amount of grain-boundary sliding became smaller than that for the shear stress of 20,000 g/sq.cm. A plot of the logarithm of the amount of grain-boundary sliding per unit temperature interval versus the reciprocal of absolute temperature was found to lie on a series of a straight line over the lower temperature range. This relationship was discussed by the relation between the amount of grain-boundary sliding per unit temperature interval and the rate of grain-boundary sliding, derived by the present authors. The activation energy thus obtained was 10,500 cal/mol for the test conducted in vacuum. According to the microscopic observation, grain-boundary sliding was found together with zone shear, but not vice versa.
In a macroscopic observation on the specimen heated up to 300°C under the constant shear stress of 30,000 g/sq.cm, a polygonized structure was found within a band region adjacent to the boundary. The formation of voids due to grain-boundary sliding was observed in original boundary, and their numbers were dependent upon the amount of sliding. These voids obstructed grain-boundary migration in the process of grain-boundary sliding.
