An investigation of Ti-43Al-9V/Ti-6Al-4V interface by diffusion bonding

Ti-43Al-9V/Ti-6Al-4V joints were fabricated by vacuum hot pressing under 920 °C/45 MPa/2 h. After fabrication the joints were thermally exposed in vacuum at 920 °C for 5 h and 17 h, and at 1100 °C for 1 h. The interfaces of both the as-prepared and the thermally exposed joints were analyzed by means of optical microscope, scanning electron microscope, electron backscatter diffraction system and energy dispersive spectrometer. The results indicate that sound joints can be achieved under 920 °C/45 MPa/2 h, and the interfacial phase sequence of the as-prepared joints was identified as Ti-43Al-9V/γ(TiAl)/B2 (the ordered form of β-Ti phase)/α2(Ti3Al)/α(Ti)/Ti-6Al-4V. The thickness of the interfacial zone increased with the duration of thermal exposure at 920 °C. Furthermore, the interfacial zone thickened rapidly when the joints were thermally exposed at temperature above the phase transformation point (α-Ti → β-Ti) of Ti-6Al-4V. In this paper, the interface growth way was also discussed based on the locations of the refractory phase YAl2 and microvoids. The analysis of the thermally exposed joints confirmed the correctness of the interface growth way. Moreover, elemental diffusion mechanism was discussed in this paper.

► Sound TiAl/TC4 joint was achieved with hot pressing parameters 920 °C/45 MPa/2 h.
► The interfacial phase sequence of the as-prepared joint is TiAl/γ/B2/α2/α/TC4.
► Interface growth way was established using the tags of YAl2 and microvoids.
► The interface intruded into the TiAl with a higher thickening speed.