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 behavior 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 remarkable elongation by recrystallization of the base metal. Elongation of the as-welded TZM with annealing before welding was significant. Behavior described by an effective strain rate demonstrated that deformation at a very low strain rate induced a ductility of the welds. Carburization was also effective to enhance the intergranular cohesion by additional segregation and precipitation. As a result, it was found that dispersion and composition of segregates and precipitates along grain boundaries contributed to the intergranular cohesion, indicating that intergranular embrittlement can be suppressed by controlling chemical bonding at grain boundaries.