Research On Ultrasonic Detection Of Diffusion Bonding (DB) Of Titanium Alloy

Diffusion Bonding(DB), as a typical solid phase welding technology, has become one of the indispensable manufacturing technologies in the fields of Aeronautics and Astronautics. It can not only shape structure parts with complex shape but also can achieve firm connection between dissimilar materials. However, the existence of diffusion bonding defects have serious impact on the parts of the structure in service performance, and due to the defects are often located in the internal structure with micro and dispersed, there is not a systematic and practical method on the quality detection at present. Thus, it has great significance to carry out nondestructive detection technology research on the bonding defects for the diffusion bonding structure performance and security.In this paper, the diffusion bonding quality inspection of TC4 titanium alloy was studied through experiment research. Firstly, through the comparison of the several nondestructive detection technologies, and according to diffusion bonding process and defect characteristics, selected the ultrasonic test and studied the commonly used test method and principle. Then, prepared TC4 titanium alloy diffusion bonding specimens with different simulation defects by controlling the diffusion bonding process parameters, such as temperature, loading pressure, connection time. Through metallographic experiment preliminarily described five different types of microstructure characteristics of interfaces and defects, providing the necessary conditions of the research of the ultrasonic test. Finally, obtained the C-scan imges and A-scan waveform data of the the diffusion bonding samples by using ultrasonic C-scan imaging technology. After getting the location and type information of the defects, combing with the camparison of the interfacial microstructure and ultrasonic testing results, the four type characteristics of defects were expounded such as disconnected defects, kissing bond defects, microporous defects and close defects. In addition, basing on the research of the relationship between beginning and bottom wave, obtained the effect on the diffusion connection quality and the wave amplitude, thus put forward the rules of different kinds of defect detection and evaluation.According to the ultrasonic test results of the different types of diffusion bonding defects, the interface quality of the aero-engine hollow blades were tested by ultrasonic testing. At the same time, through the shear strength test and fracture morphology observation of TC4 titanium alloy diffusion bonding samples, verified the validity of the ultrasonic testing method in diffusion bonding quality detection, which offered the point of judging method of different kinds of defects. According to the ratio of the amplitude of the ultrasonic beginning and bottom wave, the diffusion bonding defect sizes decreased with the increasing of the ratio. Good connection interface the ratio reached 0.8, meanwhile the disconnected defects only 0.4.Through the research of TC4 titanium alloy diffusion bonding quality ultrasonic detection, systematically analyzed the using of ultrasonic detection technology of diffusion bonding defect identification and evaluation method, the conclusions could provide the reference to quality inspection of diffusion bonding, also through mastering the characteristics of the defect information can also help the diffusion bonding process improvements.