EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

It is known for almost two decades that grain boundaries in nanostructured metals are not static objects but can migrate during loading. This has been evidenced for almost any loading situation ranging from indentation to fatigue testing and from cryogenic to moderately enhanced temperatures. Certainly such structural instabilities can drastically affect the mechanical performance and an in-depth knowledge about the mechanisms is mandatory in order to reliably predict properties of nanometals. Based on bicrystal experiments performed, indicating that the boundary velocity is proportional to the applied shear stress, these grain growth phenomena have been termed ‘stress-driven’ or shear coupled boundary migration. However, we will present experimental results on UFG nickel, proving the opposite – a clear acceleration of grain growth in highly strained regions, while in similarly stressed regions with extremely limited plasticity grain growth remained negligible. Bridging the gap between the stress and the strain driven findings will be the center of discussion. Moreover, as strain triggers grain growth, we will also show that this has an impact on crystallographic texture evolving during growth but also the opposite, that crystallographic texture can determine the extent of grain growth.