Ductile fracture by vacancy condensation in f.c.c. single crystals

We explore the feasibility of vacancy condensation as the void-nucleating mechanism underlying ductile fracture by void growth and coalescence in single crystals at room temperature. Vacancies are presumed to be primarily generated by the dragging of intersection jogs. The equations governing the rate of growth of voids by vacancy condensation are derived. These equations are used to follow the evolution of vacancy concentrations and void sizes in the Wang and Anderson [Acta metall. 39, 779 (1991)] [1] Σ9 test. We find that, when pipe diffusions are taken into account, the time required for the nucleation of a macroscopic void in the near-tip region is of the order of one minute, which is well within the time-scale of quasistatic fracture tests.

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