Influence of welding parameters and heat treatments on the structure and properties of joints of niobium alloys of the system Nb-W-Mo-Zr-C

The results are presented of the investigations into the welding thermal cycle effect on the structure and properties of the Nb-W-Mo-Zr-C alloy system. The heat treatment of the initial sheet material has been carried out conforming to two regimes. A study has been made of the tensile strength, yield strength, relative elongation and fracture toughness dependence on the annealing temperature of the base metal. The electron microscopy study of the structure is carried out on binary carbon replicas. The results of studies show that a preliminary heat treatment of the base metal of the Nb-W-Mo-Zr-C alloy system does not influence the mechanical properties and fracture toughness of the weld metal. A considerable increase in the strength, plasticity and fracture toughness of the weld metal is achieved after a final heat treatment within the temperature range 1200 to 1300 deg C with a hold-up time of one hr. The structure obtained after a heat treatment conforming to both modes causes no anisotropy of the mechanical properties