EFFECT OF HEAT-TREATMENT ON THE MICROSTRUCTURE AND THE MECHANICAL-BEHAVIOR OF TZM ALLOY

The effect of heat treatment on the microstructure and the tensile beh avior of the TZM alloys welded by an electron beam process was studied . Strength of the as-welded samples, exhibited a considerable increase . Deformation was concentrated in the weld metal and the heat affected zone due to strain localization. Postweld annealing induced a remarka ble elongation by recrystallization of the base metal. Elongation of t he as-welded TZM with annealing before welding was significant. Behavi or described by an effective strain rate demonstrated that deformation at a very low strain rate induced a ductility of the welds. Carburiza tion was also effective to enhance the intergranular cohesion by addit ional segregation and precipitation. As a result, it was found that di spersion and composition of segregates and precipitates along grain bo undaries contributed to the intergranular cohesion, indicating that in tergranular embrittlement can be suppressed by controlling chemical bo nding at grain boundaries.