Abstract: Linear friction welding (LFW) is a key manufacture technology for dissimilar materials and dissimilar quality materials blisk. The microstructure and properties of the welded joint are determined by the formation process and mechanism of the weld zone microstructure during linear friction welding, which are also the main research topics to study the bonding mechanism of LFW. The microstructures of the welded joints are obtained by stopping the vibration at different time instants during the LFW of dissimilar quality titanium alloy TC17(α+β)/ TC17(β), they are observed and analyzed by scanning electron microscope(SEM) and electron back Scatter Diffraction (EBSD). The weld zone dynamic recrystallizations and texture changes during the welding are studied. The results show that when the friction time is only 0.5s, dynamic recrystallization has occurred in the central area of the welding interface and metastable β grains have been formed. As the friction continues, even after stopping vibration and upsetting, the width of the fine grain zone gradually narrows, the grain orientation distribution becomes more and more concentrated, the proportion of the small-angle grain boundary increases, the proportion of the large-angle grain boundary decreases, and the area of the dynamic recrystallization grain gradually increases. Finally, three textures,{112} <111>, {110} <111> and {123} <111>, are formed in the weld zone, which corresponds to the three BCC slip systems. The main mechanism of this texture formation is friction pressure, instead of friction shear. When the joint is subjected to axial tension, the shear plastic deformation is easily produced in the texture grain, which will reduce the strength of the joint.

Key words: linear friction welding, titanium alloy, ebsd, dynamic recrystallization, texture