Oxide-stabilized microstructure of severe plastically deformed CuCo alloys

Nanocrystalline materials are well known for their beneficial mechanical and physical properties. However, it is of utmost importance to stabilize the microstructure at elevated temperatures to broaden the window of application e.g. by pinning grain boundaries through impurities or oxides. CuCo alloys, severe plastically deformed using high-pressure torsion, were used to investigate the evolution of oxides upon annealing. These investigations were performed using electron microscopy, synchrotron high-energy X-ray scattering and atom probe tomography. Monitoring the evolution of oxides by in-situ small angle scattering investigations indicates the growth of primary oxides as well as the formation of another species of oxide at elevated temperatures. Slightly different coarsening can be observed in heat-treated samples, which can be traced back to the influence of different oxide amounts. The initially supersaturated CuCo matrix changes by the decomposition process as well as Co-and Cu-based oxides formation and growth. It has been found that the major number of oxides which are present after annealing, can already be found in the starting materials. (c) 2022 The Author(s). Published by Elsevier B.V. CC_BY_NC_ND_4.0

Automated summary

Nanocrystalline materials with beneficial mechanical and physical properties need stable microstructures at elevated temperatures to broaden their application. This study focuses on investigating the evolution of oxides in CuCo alloys after annealing, which were severely plastically deformed using high-pressure torsion. The results show the growth of primary oxides and the formation of another species of oxide at elevated temperatures. The coarsening observed in heat-treated samples can be attributed to different oxide amounts. The study also reveals that the majority of oxides present after annealing are already present in the starting materials.