Diffusion bonding of titanium alloys

Microstructure from an electron beam diffusion bond in Ti-48Al-2Mn-2Nb alloy

Diffusion bonding of titanium alloys is an easy but comparatively slow joining technique. Work at TWI has shown that bonding using an electron beam to heat locally just the interface area considerably speeds up the process.

Usually a whole component and its jigging must be heated to temperature. However, a large thermal mass takes quite some time to cool down. With local heating, both the time at temperature and the cooling period are reduced, allowinga faster turn around. The flexibility of electron beam processing will also allow several joints to be welded at once, and gives a reduced energy consumption.

The process has been demonstrated by TWI for Ti6Al-4V and for several _γ -TiAl intermetallic alloys, including Ti-48Al-2Cr-2Nb and Ti-48Al2Mn-2Nb. In addition it can be used to join dissimilar titanium alloys. Microstructures across the welded area are essentially the same as those formed byconventional diffusion bonding.

Another advantage of using this process is that it operates at temperatures below those at which phase transformations occur.