Chemical corrosion resistance mechanism of titanium alloy radiation rods with self-protected structure.

The chemical corrosion of the TC4 radiation rod surface (TRRS) during the ultrasonic casting process has the potential to significantly impair the smooth conduction of ultrasonic waves. However, in the later stages of corrosion, a self-protected structure (TSPS) emerges under the ultrasonic cavitation effect, which serves to impede the chemical corrosion of the TRRS and markedly reduce the rate of mass loss of the radiation rod. This ensures the smooth ultrasonic conduction of the radiation rod during operation. In this paper, an analysis of the microstructure of TSPS was conducted. The surface energy ratio at different crystal planes in TC4 and the self-diffusion coefficient for two phases of Ti in TC4 were calculated. The results indicated that TSPS is characterized by α-Ti grain basal planes concentrated parallel to the TRRS, higher α phase content, and fewer crystal defects. TSPS not only inhibits Ti dissolution and delays the onset of chemical corrosion, but also reduces the chemical corrosion rate.