Crack resistance of the near-weld region of welded joints of titanium and aluminum alloys

Abstract

We studied the crack resistance Kc (KIc) of the near-weld region of welded joints of VT3-1 and VT14 titanium alloys and AMg6NPP, 12401, and 1420 high-strength aluminum alloys under fatigue and static loading. By the methods of fracture mechanics and according to the results of testing cylindrical specimens with external circular cracks initiated in the weld metal, fusion zone, zone of thermal influence, and parent material, we established that the minimum crack resistance is observed in the fusion zone and the maximum crack resistance in the parent material. The weld metal and the zone of thermal influence are characterized by intermediate values of crack resistance both under fatigue and static loading. By using 1402 high-strength aluminum alloy as an example, we studied the influence of the texture, procedure of welding, modes of thermal hardening, and scaling factor on the character of brittle fracture of the metal in the near-weld region. To enhance the characteristics of crack resistance of the near-weld region of welded joints in its weakest zones (weld and fusion zone), we propose efficient methods for welding these alloys, e.g., electron-beam welding together with the efficient choice of the modes of thermal hardening instead of argon-arc welding. This enables one to improve the purity and homogeneity of the structure of the metal in the molten-metal bath in the process of welding by decreasing its porosity and the number of inclusions and cracks appearing in these zones.