Study On The Preparation Of Single Crystal Silver And Microstructure Of Cold Drawn Single Silver

Single crystal silver wire is an ideal material for the preparation of ultrafine bonding wire due to the effect of grain boundary on deformation, so it has very important theoretical and practical significance to research systematically on the deformation behavior of cold drawn single silver. In the present paper, the main work includes:1) electrolytic polishing process of silver specimen;2) preparation of single crystal silver by seed crystal method;3) the evolution of microstructure and textures of cold drawn single silver with<110> initial orientation.Research of electrolytic polishing has showed that electrolyte for silver sample consists of50mL sulfuric acid,115mL glacial acetic acid,350mL methyl alcohol,6mL perchloric acid,12g oxalic acid and77g thiourea. The polishing process parameter for transmission electron microscopy is temperature of0～25℃and voltage of15～20V. The polishing process parameter for electron backscattered diffraction is temperature of0～25℃and voltage of5to25V for3-5minutes.In the preparation process of single crystal silver with different orientations, seed crystal plays a very important role in the solidification process. Success rate of preparation of single crystal with different orientations mainly depended on the stability of solid-liquid interface, which is not only affected by temperature gradient, traction rate and cooling power of liquid alloy but also its heat transfer rate and traction rate. If the temperature is controlled at1450±5℃for1h, traction rate is5μm/s and the silver is reasonably rapidly quenched before running, the single crystal silver with different orientation can be effectively prepared.The cold drawing texture of<110> single crystal silver sample mainly is<100> and <111>. At low strains,<111> texture components mainly come from<110> texture components, at moderate strains,<100> texture component mainly come from the<110> and <111> texture components, and at high strains,<100>,<111> and other texture have almost equal content. The evolution of deformed microstructure has three steps. At strains lower than0.94, the microstructure can be characterized as two types of crystallographic dislocation boundaries and a few twinned grains. As the strain increased, the number of twinned grains increased and the angle between dislocation and twin interface and cold drawing direction decreased. When the strains are between0.94and4.16, a typical S-type characteristics interface occurred. At strains more than4.16, deformed microstructure showed as fiber structure parallel to the cold drawing direction. Mis-orientation distribution of boundaries is double-peak in drawn<110> orientation single crystal silver sample. As strain increased, the number of low-angle interface gradually reduced, high-angle interface became more.