TA15 钛合金双层中空结构 SPF / DB 成形性能及力学性能研究

TA15 titanium alloy rolled sheets were taken as the research objects to investigate the superplastic forming / diffusion bonding (SPF/ DB) process for double-layers hollow structures. The optimal superplastic deformation conditions of TA15 alloy were obtained through high-temperature tensile tests, which were 900 ℃ / 1×10^-3 s^-1, with the elongation reaching 1340%. Microstructural observations after deformation show that with the decrease of strain rate and the increase of temperature, the α phase coarsens while the content of β phase increases, and the phase morphology remains equiaxed after deformation. Finite element software was used to analyze the equivalent stress and wall thickness distribution of the sheets during the SPF/ DB forming process of the TA15 titanium alloy double-layers hollow structure. The forming effect is favorable at 5400 s, with the minimum wall thickness at the fillet regions of the double upright stiffener and thinning rate of 57. 5%. SPF/ DB forming tests were carried out based on the finite element simulation parameters, and TA15 titanium alloy double-layers hollow structures with stiffeners of different geometric shapes were successfully fabricated. The mechanical properties of the double-layers hollow structures were measured by the three-point bending method: the ω-shaped stiffener (97. 7 MPa) and double upright stiffener (100. 8 MPa) exhibit relatively high bending strength, whereas the M-shaped and П-shaped stiffeners show lower bending strength. In addition, the influence law of geometric shapes on the bending properties of double-layers hollow structures was studied by means of finite element and tested analysis, and the bending failure modes and fracture positions in the tests were basically consistent with the simulated results.