要約

The weldability of a forged Ti−45Al−8.5Nb−0.2W−0.2B−0.02Y alloy was investigated using the autogenous gas tungsten arc welding process. The results show that sound welds can be achieved for butt-joint welding of a 2.5-mm-thick sheet at a welding current of 80 A without preheating or post-welding heat treatment. Microstructure analyses show that the forged alloy exhibits an equiaxed duplex microstructure, with an average grain size of 8.5 µm, containing a 51% γ phase, 6.5% β(B2) phase, and short boride ribbons. After welding, the microstructure exhibited 300−500-µm-thick columnar dendritic structures near the fusion boundary and equiaxed dendritic structures in the majority of the weld bead. The dendritic crystals are composed of fine lamellar colonies as the major constituent and γ and β(B2) phases as the minor constituent. Long curvy borides exist in the interdendritic zones. The Vickers hardness of the fusion zone is 560−582 HV, which is higher than that of the base alloy (378 HV). This is attributed to the high volume fraction of the α₂ phase in the weld. The appearance and the microstructure of the weld show that the forged Ti−45Al−8.5Nb−0.2W−0.2B−0.02Y alloy has good weldability.