Research On Process Of Four-Sheet Superplastic Forming/Diffusion Bonding Primary Structure With Enhancement Plates Of TA15Titanium Alloy

Superplastic forming/diffusion bonding (SPF/DB) is regarded as a pioneering modern aviationmanufacturing technology, it greatly improves the stock utilization as well as the structural reliabilityand maintainability. As an advanced manufacturing technology, the process of SPF/DB, which is abreakthrough compared with the traditional sheet metal forming methods, can save costs, reduceweight and realize the near net shape forming, and it is particularly applicable when manufacturingcomplicated parts and multilayer structures. Along with the expanding of the scope of the technologyapplication, the SPF/DB structures evolve from non-structural components, secondary structures toprimary structures. To satisfy requirements of connection and load-bearing in realistic application,SPF/DB structures must achieve the forming of the multilayer sheet-structures and diffusion bondingbetween the sheets and enhancement plates simultaneously.In this paper, the four-sheet TA15titanium alloy SPF/DB primary structure with enhancementplates was studied. Compared with conventional multilayer SPF/DB structures, the four-sheetSPF/DB primary structure increased the forming of the enhancement plates and the reinforcementsheets. The diffusion bonding quality with the four-sheet structure directly affected the performance ofconnecting and bearing. Firstly, this paper studied on the superplastic deformation behavior of TA15titanium alloy in a particular temperature and analyzed the influence of local superplastic strain on thegrain growth behavior. Secondly, this paper simulated the forming of four-sheet SPF/DB primarystructure by means of numerical simulation technique. According to the simulation results, theforming of the four-sheet SPF/DB primary structure with enhancement plates was accomplishedsuccessfully in a hot forming/superplastic forming machine. Finally, metallographic observational,focusing on the quality of the diffusion bonding in the key positions of enhancement plates, wasperformed for the formed four-sheet SPF/DB primary structure with enhancement plates.The superplastic tensile tests indicated that in the temperature of930℃the optimal superplasticdeformation condition of TA15titanium alloy is at the strain rate of5.25×10-4s-1. In this circumstance,the superplastic constitutive equation is=8100.56, and the metallurgical analyses reveal the grainsizes increasing with the local strain. The internal cross ribs of the formed four-sheet SPF/DB primarystructure have a good forming quality, and the grooves appeared near the addendum surface.According to metallographic observational in the key positions of enhancement plates, the diffusionbonding between the coarse-grained enhancement plates and the fine-grained panel is in good qualityand attains the metallurgical connection.