Z.K. Sallom, SINTEF, Trondheim (Norway); O.M. Akselsen (Sp), C. van der Eijk, SINTEF, Trondheim (Norway); C. Li, Chalmers Technical University, Gothenburg (Sweden); J. Zhang, CISRI, Beijing (China)
|
| Gamma titanium aluminide, -TiAl, is an attractive material for high temperature applications due to low weight and reasonable high temperature strength. However, there is still a barrier towards practical applications due to the high cost of processing. Moreover, techniques for joining of these materials, both to themselves and to other metals, must be developed. Thus, in the present investigation, -TiAl has been subjected to brazing, using microwave heating furnace with Ag-Ti and Ag-Cu-Ti filler metals and reducing atmosphere of Ar-H2. The results show that it is possible to join this alloy to itself and to other engineering alloys such as H13 tool steel and superalloys with no cracks in the joint. In addition, the diffusion layers are well identified in the brazed area, indicating that different phases form with different chemical composition. This observation coincides with the variations in the micro-hardness values measured in the diffusion area. The thickness of the diffusion area is the range of few microns, increasing from 2 µm at 875ºC/5 min to 12 µm at 925ºC/20 min. The formation of these thin layers can be attributed to the fast heating rate and short dwell time at the brazing temperature. Thus, the microwave joining of metals and alloys is very promising since high heating rates can be obtained and heating can be adjusted to the joining zone only, so avoiding any undesirable overheating of the adjacent areas. |
