An investigation of weld fracture surfaces and mechanical properties of two gamma titanium aluminide alloys

Abstract

Two gamma titanium aluminide sheet materials were investigated to characterize the fusion zone cracking and mechanical properties that occur for specimens subjected to gas tungsten arc welding (GTAW). The materials used in this study consisted of essentially the same composition; however, one was received in the primary annealed (PA) condition and the other in the designed fully lamellar (DFL) condition. For both materials, all of the specimens welded with a stationary torch (spot welds) cracked catastrophically immediately after welding. The PA specimens exhibited a different mechanism of fracture in the fusion zone compared with the DFL specimens. The fractures that occurred in the PA specimens followed an interdendritic path through regions that did not completely solidify prior to the occurrence of cracking, whereas for the DFL specimens the primary mechanism of fracture was cleavage. For the butt welded specimens, no cracking occurred. For both materials, specimens welded parallel to the rolling direction exhibited more distinct preferred growth of columnar grains than those welded perpendicular to the rolling direction. The weld structure/property relationship is also discussed.