2019 Volume 60 Issue 1 Pages 86-92
The objective of the present study was to investigate the suppression of grain-boundary sliding and its accommodation at triple junctions. Tricrystals of pure aluminum and pure copper having 〈110〉-tilt Σs = 3, 3, and 9 boundaries were grown. Creep tests were carried out at temperatures above 0.8TM, where TM is the melting point on the absolute temperature scale. In all specimens, boundary sliding occurred only in the Σ9 boundary. In aluminum tricrystals, sharp folds formed as a result of the suppression of Σ9 boundary sliding at the triple junction. Slip lines parallel to the trace of the (100) plane were observed in the fold. In copper tricrystals, no fold formed but a wedge crack was initiated at the triple junction and extended along one of the Σ3 boundaries aligned perpendicularly to the tensile axis. These results suggest that the ease or difficulty of fold formation affects crack formation during creep.