New technology of ultrasonic processing across different phases in laser welding for damage repairing of thin-walled structure in military aircraft

A new technology of ultrasonic processing across different phases based on laser welding (UPPW) was proposed to control residual stress and distortion of thin-wall structure in military aircraft. In the process of laser welding, ultrasonic vibration was applied to specimen, by virtue of impact including a few key across state transition phases such as formation, flow and solidification of laser molten pool and stage of high temperature superplastic solid-state phase transformation for welded joints can be affected, the weld solidification organization was improved and joint residual stress was released and joint mechanical properties was improved and deformation was controlled and cracks defects was reduced. Experiments show that the residual stress and distortion of thin-walled structure can be reduced significantly by UPPLW. With the appropriate process parameters, the residual deformation of TC4 titanium alloy with the thickness of 1.5 mm can be reduced by approximately 50% compared with that of the conventional welding and the grain size can be fined by about one level and much more uniform.