| Superplastic Forming and Diffusion Bonding (SPF/DB) process is one of the most important research subjects in the area-space engineering field. The titanium alloy multilayer sandwich structure is an important application in SPF/DB because of its perfect frame, low weight and few components. At present, the titanium alloy SPF/DB process has been taken into applied use in China, but there is a great gap compared with developed countries in the SPF/DB technology. So the research for titanium alloy and other advanced materials is carried out with SPF/DB process, which has extraordinarily magnitude significance to reduce costs, improve component performance and increase the aircraft thrust-weight ratio. In this thesis, the SPF/DB for three-sheet structure of Ti-6Al-4V titanium alloy was investigated combining numerical simulation by the method of SPF after DB.Beginning with mechanism and deforming path of SPF/DB were investigated. Then the experimental project about the SPF/DB for three-sheet structure of Ti-6Al-4V was established, the method of microstructure analysis for the area-bonding ratio and grain side was advanced and the factors influencing process was discussed in this thesis.Based on the theoretic and experiment, finite element simulation for SPF process was carried out on the software MARC which could optimize the forming part structure and predict the thickness distribution. The impact of strain rate on forming results and forming time was discussed, which also showed 1x10-3 s-1 was the best value of optimal strain rate. At the same time, the optimal SPF pressure-time curve was generated with the maximum constant strain rate control.The SPF/DB for three-sheet structure of Ti-6Al-4V was investigated. The thickness distribution and forming result was analyze. The impact of different transmutation on grain side was discussed. At one time, the area-bonding ratio and grain side was computed. The results show that the thickness of forming part is uniformity on the whole and the maximum thinning rate is 32%. The area-bonding ratio is grate overall and the maximum value is 100%. Compared with the formed grain side, the original one is much smaller. The grain side of the left or right rib of the middle sheet and the forming fillet is least. The quality for the upper sheet of forming part is very good, while the lower sheet takes on mark-off and the profile of the middle sheet is perfect. In the end, comparing the numerical simulation result with the forming one, it proved that the numerical simulation was correct. |
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