The SPF/DB process of ultra-thin hollow four-layer structure was investigated by using TA15 titanium alloy hot rolled sheet. Firstly

the superplastic deformation behavior of TA15 titanium alloy in the process temperature range was studied by tensile test

and the corresponding stress–strain curves were obtained. Then

finite element software was used to simulate the design of the four-layer longitudinal reinforcement structure with thin-walled transverse local penetration

and the distribution of wall thickness reduction and stress concentration during the forming process is determined

which provides effective guidance for the subsequent diffusion bonding test. Finally

an ultra-thin hollow fourlayer structure with good vertical ribs and a triangular zone width of only 0.9 mm was successfully prepared. The maximum thinning rate of the panel was 18.6%

the maximum thinning rate of the core plate was 55.1%

and the bonding rate of the diffusion bonding area between the core plate and the panel was 92.1% – 98.5 %. The original microstructure of TA15 sheet for forming is fine

broken and equiaxed

the average grain size is less than 5 μm. After long-term superplastic deformation and thermal exposure

the grain size grows significantly.