Fracture toughness of friction stir welded titanium alloy joints was investigated using Compact tension (CT) impact specimens. The fracture toughness slightly decreases to about 90% of the fracture toughness. The fracture surface was mainly ductile fracture mechanism with a large number of dimples. The crack propagation path was straight and mixed with intergranular and transgranular fracture. The stir zone of joint has a large number of fine ɑ grains with some dislocations. For texture, The stir zone has hard orientation {0002} <11$2(-)$0>, the directions of cylinder and plate thickness are parallel. The reduction of fracture toughness in the stir zone is mainly related to microstructure and texture.

使用紧凑张力（CT）冲击试样研究了搅拌摩擦焊接钛合金接头的断裂韧性。断裂韧性稍微降低至断裂韧性的约90％。断裂面主要为韧性断裂机制，有大量凹坑。裂纹的传播路径是笔直的，并且混合有晶间和跨晶的断裂。节理的搅拌区有许多细小的with晶粒，并具有一些位错。对于纹理，搅拌区具有硬取向{0002} <11$2（-）$0>，圆柱体和板厚方向平行。搅拌区断裂韧性的降低主要与显微组织和织构有关。