Mikrostruktura a mechanické vlastnosti nanostrukturních kovových materiálů.

Bajtošová, Lucia

This work integrates in-situ transmission electron microscopy mechanical testing with large-scale molecular dynamics (MD) simulations to establish a unified mechanistic un- derstanding of how nanoscale metals deform and how these mechanisms govern their mechanical response. The study focuses on single-crystal and polycrystalline nanopar- ticles and polycrystalline thin films across FCC, BCC, and HCP systems. FCC metals (Cu, Ag, Ni) exhibit very high strengths but deform through intermittent dislocation bursts and rapid surface-mediated defect annihilation, with polycrystalline nanoparticles showing lower strengths due to grain-boundary-dominated processes. Multiply twinned particles display smooth, sustained plastic flow enabled by mobile growth twin networks. In nanocrystalline FCC films, strength arises from a balance between constrained dis- location nucleation and limited grain-boundary accommodation. BCC Fe nanoparticles reach near-ideal strengths, observed both by in-situ compression and MD. Fe films likewise show high strength but greater ductility than FCC films, deforming through widespread dislocation activity. HCP Ti nanoparticles undergo deformation dominated by ordinary dislocation slip, with neither twinning nor phase transformation playing a significant role. MD simulations incorporating...

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