Interfacial behaviors and mechanism of ZrC-SiC composite and Ti system under pulsed electric current

The interfacial behaviors and mechanism of ZrC–SiC and Ti system under pulsed electric current were systematically analyzed in this study. The results showed that the dominant products of Ti and ZrC–SiC composite interface were TiCx and Ti3Zr3Si3. The former was originated from the interaction of Ti and interfacial ZrC, while the latter resulted from the grain-boundary diffusion of inner Si and Zr atoms towards Ti interlayer. Meanwhile, the reaction of Ti and interfacial SiC produced TiCx and Ti5Si3C, and Ti5Si3C would transform into Ti5Si3 and TiCx in the Ti-enriched environment. More interestingly, pulsed current could significantly promote the interfacial reactions, the combination of experimental analysis and theoretical calculation indicated that the current-related mechanisms involved (i) quick grain-boundary diffusion of Zr and Si benefited from the local joule-heating, (ii) strengthened volume diffusion of C element by the increasing lattice defects and (iii) additional diffusion flux towards Ti interlayer induced by the temperature gradient in micro-scale. Additionally, the coupled influence of skin effect and electromigration were studied, the results revealed the skin effect caused a local high current density at the sample edge, which triggered the directional movement of carbon vacancies thus the preferential growth of TiCx phase in the anode, but the microstructure was homogenous in the majority area due to the exponential distribution of current.