Abstract
High-purity aluminum bicrystal specimens having boundaries with an angle of 45 deg. to the tensile axis were prepared by the recrystallization method.
During the creep test and the constant rate heating test in argon atomosphere at high temperatures under constant tensile load, grain boundary sliding and shear deformation near the boundary were observed in these specimens.
The grain boundary sliding vs. time curve changes stepwise in the tensile creep tests. The grain boundary sliding was accompanied by crystal shear deformation near the boundary, and the observed grain boundary displacement had no relation with the boundary misorientation angle θ, but with the angle αA or αB between the crystal slip plane trace and the boundary trace at the observed plane of the bicrystal specimen. The contribution of grain boundary sliding to the deformation amount of the specimen became larger with the testing time at 300° and 350°C, and the maximum value was found to be about 36% at 400°C for 300 minutes. Grain boundary migration of the common boundary proceeded in the direction to release the strain energy of plastic deformation that occurred locally from the boundary irregulalities to the component crystals. The initial grain boundary displacement was proportional to heating temperature, and the obtained activation energy for the boundary sliding of the specimens with misorientation angles αA+αB of 18∼71 deg. was 11600∼26400 cal/mol, respectively.
