Grain boundary migration mechanisms in FCC metals under mechanical and capillary driving forces

The physical and mechanical properties of polycrystalline metals are significantly influenced by the average grain size and crystallographic texture. These characteristics change during grain growth, which is a process mediated by the migration of grain boundaries (GBs). The main driving force for GB migration in grain growth is often assumed to be the curvature of the GB. However, recent studies have shown that grain boundary migration in polycrystals is much more complex than the migration of GBs towards their center of curvature. Furthermore, studies in bicrystals have shown that the motion normal to grain boundaries can be accommodated by the tangential translation of grains and/or shear deformation of the lattice traversed by the grain boundary. However, the exact conditions at which these mechanisms are activated are not yet well understood. It has been hypothesized that the driving forces behind the migration may play a role. In this thesis, atomistic simulations are used to investigate the kinetics and mechanism of curvature and stress-driven GB migration in both bicrystalline and nano-sized Al polycrystals to understand the influence of the driving force. Furthermore, the associated grain growth kinetics in the polycrystal is thoroughly studied. To this aim, novel analytical tools are developed to enable a detailed analysis of microstructure development in polycrystals using data generated from atomistic simulations. The findings of this study are expected to provide insights into the effects of high-temperature annealing and stress on microstructure evolution and facilitate the development of accurate microstructure-based models for grain growth in polycrystals, which are crucial for designing advanced materials for various engineering applications.

Date

2024-05-15

Resource Type

Text

Resource Subtype

Dissertation

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