CuTiNiZrV Amorphous Alloy Foils for Vacuum Brazing of TiAl Alloy to 40Cr Steel

Vacuum brazing of TiAl alloy to 40Cr steel sheets was conducted with newly developed CuTiNiZrV amorphous foils. It was found that a diffusion layer, filler metal and reaction layer existed in the brazed seam. The diffusion layer in the joint brazed with Cu43.75Ti37.5Ni6.25Zr6.25V6.25 (at.%) foil was flat and thin, containing Ti19Al6 and Ti2Cu intermetallic compounds; however, the diffusion layer brazed with Cu37.5Ti25Ni12.5Zr12.5V12.5 foil was uneven with bulges, consisting of essentially Ti-based solute solution. The foil with 12.5 at.% V showed inferior spreadability compared to that with 6.25 at.% V at brazing temperature. However, fracture happened along the diffusion layer with 6.25 at.% V foil due to the formation of brittle intermetallic phases, but the joints brazed with 12.5 at.% V foil failed through the TiAl substrate. These results show that designing amorphous alloy with less Ti and more V for brazing TiAl alloy to steel is appropriate.