HRTEM investigation of diffusion in metallic-glass multilayer films
Here we present a data set on our research of diffusion in metallic glass multilayers. In the present data set we combined raw data from nanoindentation, SEM and TEM experiments. Lack of plasticity is one of the main disadvantages of metallic glasses. One of the solutions to this problem can be composite materials. Diffusion bonding is promising for composite fabrication. In the present work the diffusion process in glassy multilayer films was investigated. A combination of advanced TEM methods and precision sputtering techniques allows visualization and study of diffusion in amorphous metallic layers with high resolution. Multilayered films were obtained by RF sputter deposition of Zr-Cu and Zr-Pd. The multilayers were annealed under a high vacuum (10‒5 Pa) for 1 and 5 hours at 400oC, i.e. well below the crystallization temperatures but very close to the glass-transition temperatures of both types of glassy layer. The structural evolution in the deposited films was investigated by high-resolution transmission electron microscopy. It was observed that despite the big differences in the atomic mass and size, Pd and Cu have similar diffusion coefficients. Surprisingly, 1 hour of annealing results in formation of metastable copper nanocrystals in the Zr-Cu layers which, however, disappear after 5 h of annealing. This effect may be connected with nanovoid formation under a complex stress state evolving upon annealing, and is related to the exceptionally slow relaxation of the glassy layers sealed with a Ta overlayer.