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

For a decade, modern synthesis methods, such as severe plastic deformation, were developed and applied on metallic lamellar composites in order to reduce their layer width to less than 100 nm. Nowadays, these new nanostructured materials then offer outstanding mechanical properties which are partly attributed to the role increasingly played by interfaces in their plastic behavior. This role is crucial in the nanolamellar Ag/Cu composite. Indeed, silver is known to twin easily under mechanical stresses whereas copper needs more specific conditions to do so. In the Ag/Cu composite, experimental studies by transmission electron microscopy showed that the deformation twins coming from silver layers may readily cross some interfaces and spread in copper layers. In that respect, it extends the spectrum of the mechanical conditions for twinning in copper. Although these observations were then completed by atomistic simulation studies several questions for a better understanding of elementary mechanisms remain unanswered.
Atomistic simulation, and mainly molecular dynamics, fit particularly well to the nanometric scale and to the study of elementary mechanisms. In this kind of studies twins are introduced via indirect ways in nanolamellar Ag/Cu composite. In many of them, one introduces defects onto surfaces which then act as nucleation sites for twinning. These surfaces, which are fewer in the real material than in simulations, interact consistently with twins and the found elementary mechanisms depend a lot on their presence. In our study, performed on a similar nanostructured Ag/Cu material, we consider a higher ratio of interfaces and we observe the nucleation and the growth of twins, not only from surfaces but from interfaces between both metals. I will present to you this elementary mechanism and then discuss its characteristics.