Probing the deformation and fracture properties of Cu/W nano-multilayers by in situ SEM and synchrotron XRD strain microscopy

When thin metallic multilayers deposited on a compliant polymer substrate are subjected to stretching, a “brick wall” fracture pattern arises that is associated with a non-uniform two-dimensional stress-strain state evolving as a function of the underlying substrate stretch. The present study is devoted to in situ mechanical microscopy of strain states in a copper/tungsten 18/6 nm multilayer using the combination of synchrotron Scanning X-Ray Diffraction Microscopy (SXDM) and Scanning Electron Microscopy (SEM), coupled with Digital Image Correlation (DIC). We demonstrate that these methods allow spatial variation of the coating strain to be mapped and compared with theoretical predictions based on shear lag theory, allowing the fracture properties of the multilayer to be extracted.