Preparation of in situ Cu-Nb composite sheet and wire for TEM analysis

Cu-Nb in situ composites attain anomolous increases in strength upon mechanical deformation. The unique filamentary microstructures that evolve during processing (cold rolling and/or wire drawing) are the source of the strengthening. Results from transmission electron microscopy characterization studies have played a key role in the understanding of the relationships between structure and properties. However, the fabrication of reliable TEM samples has been extremely challenging for the following reasons: traditional electrochemical techniques are not suitable for the two-phase microstructure, preparation of longitudinal and transverse sections of fine (--150 μm diameter wires) and thin (--60 μm thick) sheet is tedious, and it is necessary to avoid excessive heat (< 300C) during sample preparation to preserve the metastable structural arrangements. This paper reviews the procedures used to prepare TEM specimens from bulk wire and sheet samples as well as from extracted Nb filaments. Proper techniques for plating, mounting, sectioning, polishing, and ion-thinning are discussed