Effect of titanium grain orientation on the growth of compounds at diffusion bonded titanium/steel interfaces

Commercial pure titanium plates with different grain orientations were successfully bonded to carbon steel plates by diffusion bonding. The Ti/steel interfaces were carefully characterized by scanning electron microscopy, energy-dispersive spectroscopy, electron backscattered diffraction, and X-ray diffraction. The results revealed that TiC was generated at the Ti/steel interface during the diffusion bonding process. The thickness of the TiC layer increased with increasing diffusion temperature and holding time. Furthermore, the orientation of the Ti grains influenced the activation energy for the growth of TiC and affected the thickness of the TiC layer at the Ti/steel interface. The anisotropic growth of the TiC layer was explained by the interstitial diffusion mechanism of C atom in alpha-Ti. Moreover, the TiC layer acted as a barrier layer at Ti/steel interface, inhibiting the diffusion of Fe atoms into alpha-Ti. An increased diffusion temperature reduced this barrier effect, leading to the formation of FeTi and Fe2Ti at TiC/Ti interface.