Abstract
A mechanism of intergranular wedge crack nucleation in polycrystalline materials is the piling up of extrinsic grain boundary dislocations around triple lines. In this paper, an approximate theoretical analysis is carried out to compare nucleation at the I-, U- and amorphized triple lines due to edge dislocations having Burgers vectors tangential to the grain boundary planes. The analysis is based on an energy approach of fracture mechanics. Numerical results for aluminium show that: (l) the overall pile-up equilibrium configurations of the dislocations are insignificantly affected by the type of triple line, (2) two types of cracks, sub-microscopic (G 0.05 μm) and microscopic (10–20 μm), are predicted, depending on the strength of the disclination defects at the triple line, and (3) the pile-up populations and the Burgers vectors of the dislocations can significantly influence the nucleation characteristics.
Published Version
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