Changes in the Microstructure and Element Composition of Titanium Waveguides During Ultrasonic Welding of Plastic Products

The results of the study of changes in the microstructure and elemental composition of titanium waveguides made of BT3-1 alloy (Ti—6 Al—2 Sn—4 Zr—2 Mo), which are used for ultrasonic welding of plastic products, are presented. Using a combination of methods, including optical, confocal scanning laser microscopy, raster and transmission electron microscopy, as well as energy-dispersive X-ray microanalysis, the morphology of the surface and the structure of the near-surface layers of the waveguides were studied. The processes of cavitation erosion, which lead to the formation of pores and a regular topography on the contact surface, were identified. In the near-surface layer, the development of the process of grinding the grain structure with the formation of nanosized crystallites (about 50 nm in diameter) with the formation of a surface amorphous layer (about 4 μm thick) enriched with carbon, oxygen, and silicon has been detected. It has been established that these changes are caused by the simultaneous effect of mechanical stress, high-frequency ultrasonic vibrations, local heating, and chemical interaction with the material of the welded parts, including the transfer of plastic components (such as SiO2) into the waveguide material.