UKAEA-CCFE-PR(23)126

Nanoscale speckle patterning for high resolution strain mapping of environmentally sensitive materials

Scanning electron microscopy-based is now an established technique, providing full-field strain and displacement measurement at the microscale. Techniques for generating speckle patterns for sub-micron strain mapping are highly substrate dependent but typically rely on applying aggressive conditions which may alter the microstructure of interest or damage the substrate. We detail a modified patterning procedure, compatible with metallic materials that are particularly sensitive to the application of heat or corrosive media. Nanometre-thick silver films, applied with physical vapour deposition, are remodelled using NaBr in non-aqueous isopropanol, forming a uniform dispersion of silver islands highly suitable for DIC measurement. The entire procedure is performed at ambient temperature. We find that the DIC pattern is suitably electron transparent to allow electron backscatter diffraction (EBSD) measurements without pattern removal, producing diffraction patterns of sufficient quality for cross-correlation based high-angular resolution EBSD. This property facilitates simultaneous EBSD and DIC mapping experiments, providing deeper insights into the kinematics of plastic deformation in crystalline materials. Sub-100 nm islands are achieved through control of the sputter coating parameters, resulting in DIC cross-correlation with a 50% overlap. This resolution is sufficient to capture the fine detail of strain localisation phenomena during plastic deformation, demonstrated here with a case study in CuCrZr, a precipitation-hardened heat sink material for application in nuclear fusion components.

 

 

Collection:
Journals
Journal:
Strain
Publisher:
Wiley Online Library