Microstructure and Mechanical Properties of Electron Beam Welded Titanium Alloy Ti-6246

Electron beam welding(EBW) was applied to a 10-mm-thick plate cut from Ti-6246 compressor disk.The microstructural characteristics, microhardness and room temperature tensile properties were investigated. Microstructure observations indicated that there existed plenty of thin needle-like α platelets studding in the matrix of the columnar β grains in the as-welded fusion zone(FZ). Post-weld heat treatment(PWHT) led to the precipitation of small secondary α platelets in the β matrix in heat affected zone and FZ. The thickness and the density of α platelets increased as the temperature of PWHT increased from545 to 645°C. The microhardness across the Ti-6246 EBW joint exhibited a nonuniform distribution. The hardness increased with the decrease of distance to the weld center, and reached the maximum of 467 HV in FZ when PWHT was carried out at 595°C. All the weldments tested with tension were fractured at the base material(BM) and exhibited a ductile fracture mode. The major deformation barrier in BM was the platelet α/β interfaces, however, the major deformation barrier in FZ was found to be β grain boundaries and secondary α/β interfaces. The BM with thicker platelet α phases had lower strength than the other two zones in the joint, and the BM deformed first and led to fracture in this zone.