Alloys of cast gamma TiAl were butt-welded using traveling autogenous gas tungsten arc (GTAA) welding. Postweld heat treatment (PWHT) was used to optimize mechanical properties of the fusion zone. Microstructural examination of the aswelded condition revealed a nearly lamellar microstructure in the base metal and a dendritic structure with presence of interdendritic gamma phase in the fusion zone. This fusion zone microstructure yielded a reduction of ductility relative to the base metal as suggested by the results of microhardness profiles. Postweld heat treatments performed at 1000 deg C and 1200 deg C proved to be beneficial for decreasing the fusion zone hardness. This reduction of hardness was related to microstructural transformations occurred upon postweld heat treatment in the gamma+alpha_2 and gamma+alpha fields. The dendritic microstructure of the aswelded fusion zone was transformed into a variety of microstructures dependingupon the temperature and duration of the heat treatment. Best results were achieved when the fusion zone microstructure exhibited an equiaxed gamma structure together with fine lamellar grains.
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