Effect of hot Working Temperature on the Weldability of Ti-6AI-4V Alloy

The resulting microstructure and mechanical properties of Ti-6A1-4V alloy depend to a great extent on the temperature at which working is carried out. Two components namely 650mm diameter Rings and 650mm diameter Hemispherical Shells have been processed at temperatures about 50°C below and 100°C above the beta-transus temperature respectively. These components have been evaluated for their microstructures, mechanical 'properties, fracture toughness and weldability. The microstructure of the rings which have been rolled at 950°C reveals the presence of equiaxed primary alpha in the matrix of transformed beta. On the other hand, the microstructure in the case of hemispherical shells forged at 1100°C, is 100 percent transformed beta. The tensile ductility of the rings is found to be higher than that of the hemispherical shells. However, the fracture toughness of hemispherical shells is much superior to the rings. The samples cut from these components are machined to 12mm thickness and electron beam welded for their comparative property evaluation. It is seen that the welded samples reflect and retain almost the same tensile properties as the parent material except for the impact toughness at the fusion zones.