Microstructures and Mechanical Properties of Transient Liquid-Phase Diffusion-Bonded Ti3Al/TiAl Joints with TiZrCuNi Interlayer

Transient liquid-phase diffusion bonding of Ti3Al-based alloy to TiAl intermetallics was conducted using Ti-13Zr-21Cu-9Ni (wt pct) interlayer foil. The joint microstructures were examined using a scanning electron microscope (SEM) equipped with an electron probe micro-analyzer (EPMA). The microhardness across the joint was measured and joint strengths were tested. The results show that the Ti3Al/TiAl joint mainly consists of Ti-rich phase, Ti2Al layer, α 2-Ti3Al band, and residual interlayer alloy dissolved with Al. The amount of residual interlayer at the central part of the joint is decreased with the increase of the bonding temperature, and meantime the Ti2Al and α 2-Ti3Al reaction bands close to the joined Ti3Al-based alloy become thickened gradually. Furthermore, the central part of the joint exhibits the maximum microhardness across the whole joint. The joints bonded at 1193 K (920 °C) for 600 seconds with a pressure of 2 MPa presented the maximum shear strength of 417 MPa at room temperature, and the strength of 234 MPa was maintained at 773 K (500 °C).