Role of SFE in the Interaction of Extended Dislocations With Nanovoids

Ashley Roach, University of California, Santa Barbara

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Voids are prolific in structural metals across fabrication techniques, compositions, and applications. In relevant materials and fabrication techniques, the void sizes are found to range from a few nanometers to a few hundred micrometers in diameter. Many think of voids as stress concentrators that grow and cause damage/failure, however when void dimensions are on the nanoscale they can instead act as dislocation obstacles, increasing the stress required for dislocation shearing and strengthening the metal. Intermediate length-scale, or “meso”-scale, models such as Phase Field Dislocation Dynamics (PFDD) offer a unique approach to nanovoid strengthening. PFDD is rich in physics with discretely defined dislocations that evolve simultaneously with voids in the material matrix, yet also allows for cell sizes large enough to be relevant to part performance. In this work, void strengthening and the influences of void size, void spacings, and material properties are investigated, with particular focus on stacking fault energy (SFE) for dislocations in fcc materials, many of which naturally dissociate into Shockley partials. The primary material response of interest is the critical stress for a dislocation to bypass a given void obstacle, which can be related to bulk material yielding response. In addition, dislocation bypassing behaviors and mechanisms were studied with climb and cross slip excluded.

Abstract Author(s): Ashley M. Roach, Shuozhi Xu, Daniel S. Gianola, Irene J. Beyerlein, D.J. Luscher