An investigation of springback of TC4 alloy by triple-layer sheet hot stamping and cold die quenching process

In this paper, the springback behaviors of TC4 alloy under triple-layer sheet hot stamping forming (THF) process is studied. To verify the springback control ability of the process, the U-shaped part experiments were conducted, and the effects of forming temperatures and quenching times on springback is revealed. A finite element (FE) model is established to study the deformation characteristics of U-shaped parts and the stress relaxation (SR) behavior during the quenching process. The springback control mechanism of THF is analyzed. Finally, the forming experiments of typical aviation parts were carried out to verify the feasibility of this process. The study showed that the simulation results were consistent with the experimental results. The springback angle from 2.67° of 750°C to 0.46° of 900°C in the THF process. Compared with the results obtained by single-layer sheet hot stamping forming (SHF) process, the springabck angle decreases by 83.06% at 900°C. Meanwhile, the affected is much more by the quenching time than SHF. The springback angle decreases from 0.58° of 30s to 0.24° of 60s at 850°C. The thermal insulation effect of THF makes the SR of the parts more sufficient in the process of quenching, and the residual stress is fully released. In addition, it is found that the neutral layer shift in the fillet area at the bottom of THF parts is relatively small and is more sensitive to the effect of forming temperature. According to the FE simulation and microstructure analysis, it is jointly revealed that the inner and outer layers at the bottom fillet are close to the ideal state of tension-compression symmetry. The typical aviation parts have a high forming accuracy under THF processes. This research provides a new strategy for achieving high-precision forming of titanium alloy thin-walled parts in the aerospace industry.