A study of the spinodal decomposition of AgC u alloy films using in situ transmission electron microscopy

We performed in situ transmission electron microscopy (TEM) investigations to understand spinodal decomposition in Ag Cu alloy thin films. The decomposition of a homogeneous nanocrystalline morphology into a heterogeneous two-phase structure when annealed in situ from room temperature to 400 °C was investigated with different imaging modes in the TEM. These studies reveal phase transformation proceeds in stages: between 180 and 200 °C, onset of phase separation via spinodal decomposition is observed. Then, prominent phase separation occurs between 200 and 250 °C with minimal grain growth. Next, between 250 and 300 °C, grain growth primarily occurs via coalescence, with no apparent phase separation. From 300 to 350 °C, we observe significant phase separation and Ostwald Ripening. Finally, between 350 and 400 °C, further coarsening occurs via coalescence. STEM-HAADF mode reveals the onset of phase separation from domains as small as 5 nm and these results are also supported by electron diffraction and compositional mapping. Summary of the study carried out, the image shown at the centre is of the in-situ TEM holder used in this study, and the images on the left are the micrographs and profile of the diffraction ring before heating, and the images on the right are corresponding images after in-situ heating. Using this approach, we gain insights into tuning the microstructure and thereby the properties of alloy thin-films. • Spinodal decomposition of Ag 53 Cu 47 alloy thin films is visualised in great detail using in situ TEM. • Events such as phase separation, coalescence, grain growth, and Ostwald ripening are captured in real-time. • Scanning transmission electron microscopy (STEM mode) is vital to visualise several key transformations. • Our approach paves the way for a faster determination of the interaction between local compositions, heat treatments, microstructure, and properties of newer alloys as well.