Triple junction motion in aluminum tricrystals

The results of an investigation of the steady-state motion of grain boundary systems with triple junctions in high-purity aluminum are presented. In particular, the migration of systems with 111> and 110> tilt boundaries was studied. The experimental results demonstrate that the motion of grain boundary systems with triple junctions in aluminum can be controlled by slowly moving triple junctions. The influence of triple junctions depends on temperature, and it is particularly strong at low temperatures. In the high- temperature regime the motion of a connected grain boundary system is less affected by the triple junction, and, therefore, effectively controlled by the grain boundary mobility. The experiments reveal a drastic differ- ence between activation enthalpy of grain boundary and triple junction motion. Therefore, there is a tempera- ture below which triple junctions govern the motion of the connected boundary system. This temperature was found to depend on the particular grain boundary and triple junction geometry.  2001 Acta Materialia Inc. Published by Elsevier Science Ltd. All rights reserved.