Interface characteristics in diffusion bonding of a γ-TiAl alloy to Ti-6Al-4V

In the present study, diffusion bonding of a gamma-TiAl alloy to a Ti-6Al-4V alloy at the different temperatures ranging from 1073 to 1173 K under an applied stress of 100 MPa for 2 h was investigated. The observation of the microstructure revealed that sound joints between the gamma-TiAl Alloy and the Ti-alloy without any pores or cracks could be achieved through diffusion bonding at temperatures over 1073 K under the applied stress of 100 MPa for 2 h. The bond was composed of two zones, and its width increases with the increase of the bonding temperature. The EDS chemical composition profiles indicated that there is a diffusion flux of Al-atoms from gamma-TiAl alloy towards the Ti-alloy and of Ti-atoms in the opposite direction. The microhardness of the diffusion bond was in the range of 310-450 HV, and increased monotonously from the side near the gamma-TiAl alloy to the side near the Ti-alloy. In this bonding process, the diffusion flux of Ti atoms in interface is mainly controlled by grain boundary diffusion.