Research On The Superplastic Forming And Diffusion Bonding Technology Of Titanium Alloy

The technology of superplastic forming (SPF) and superplastic forming combined with diffusion bonding (SPF/DB) in titanium alloy allows for the manufacturing of complex shapes, and embodies advantages in the aspects of cost and weight saving. So it has been paid significant attention in aviation and spaceflight fields by many countries. With the development of Hight-speed and large aircraft, SPF/DB has been one of the key technologies in aerospace manufacturing industry. Further more, the practical application of SPF/DB technology has been the research hotspot.In this thesis, combining with application of typical structure, the SPF/DB technology of TC4 titanium alloy was studied as following:1. According to relevant theories, the formability of TC4 and the behavior of metal atom diffusion were detailed analysed. By the use of finite element analytical software MARC, the process of superplastic forming of single layer partial reinforced structure and two layers box-shaped structure were simulated, so the shape and size of the structure were predicted. Meanwhile, the pressure vs. time curve at a constant strain rate was obtained through the self-adapting control, which provided a reference to the practical pressure control in the experiments.2. Design the die needed after finite element simulation, and the technology parameters such as temperature, pressure and time were obtained through a series of experiments.3. Research on the SPF/DB technology of TC4 titanium alloy. The optimal parameters of diffusion bonding were obtained after microstructure analyse of the diffusion bonding interface.Through upwards research, the following results under this experiment condition can be concluded:1. The optimal parameters of superplastic forming of TC4 titanium alloy are: temperature is 920℃, maximum gas pressure is 1.5MPa, forming time is 40min.2. The optimal parameters of diffusion bonding are:the vacuum is higher than 10-2Pa, the bonding temperature is 920℃, the bonding pressure is 3.0 MPa and the bonding time is 90min.3. The grain size of TC4 titanium alloy grew heavily after SPF/DB experiment. Lastly, analysis and suggestions were given for the present problems with the SPF/DB technology.