Springback is a tough issue in sheet forming, and always leads to dimensional inaccuracy of formed parts. Titanium alloy selected as desired light-weight alloy has been playing significant roles in aerospace industry because of its good comprehensive performance. Whereas, titanium alloy components manufactured always exhibit severe springback at room temperature, which greatly restrict their application. To explore the possibility of reducing springback, rectangular lath-shaped parts with Ti-6Al-4V alloy sheet were fabricated by impact hydroforming (IHF) with self-designed equipment. Consequently, much lower springback is obtained using IHF with high strain rate than that formed by conventional stretch-bending with low strain rate. Great efforts are paid to clarify the mechanism of springback restriction under IHF. Different from traditional forming methods, more complex and high-speed interaction behavior between liquid and Ti-6Al-4V alloy sheet occurs. It considerably increases the difficulty for analyzing the deformation process of sheet under IHF. Thus, a novel solid-liquid coupling numerical simulation technology for IHF was developed. To validate the simulation accuracy, experiments with different forming processes and parameters were performed. Given the combined analysis of experimental and simulation results, it is found that distinctive forming paths are introduced between stretch-bending and IHF. Specifically, the preferred deformation region of sheet transfers from middle region for conventional stretch-bending to end regions under IHF, which mainly attributes to the unique loading behavior of liquid at high strain rate.

Aluminum-Lithium (Al-Li) alloy has excellent properties such as low density, high elastic modulus and high specific strength, and it is considered as the most ideal structural material in aerospace. However, due to the low plasticity of Al-Li alloy at room temperature, it is easy to crack during cold forming, so its application and development have been limited. In order to explore the possibility of improving the plasticity of 2195 Al-Li alloy at room temperature, a half-tube part with curvature and deep cavity structure was formed by using impact hydroforming (IHF) technology. In this paper, the process route of half-tube part was optimized and four sizes of blank were designed. Through finite element numerical simulation and analysis, it was found that the F area was prone to wrinkle defects when there was less material at the inner arc position, and the most serious thinning occurred in the design margin area. After analysis and comparison, the blank size with drawing ratio of 2.22 was finally selected. Based on the verification experiment, it was found that due to the material properties of Al-Li alloy and the characteristics of IHF, one-step forming was difficult, and the forming of half-tube part was prone to insufficient drawing depth or large area fracture; Although the part obtained by two-step forming also had cracks, the overall forming quality of the part would not be affected because they were located in the design margin area to be removed later. In addition, it was observed that the surface quality of the part removed the design margin area were free of wrinkles and cracks, which meets the objective design requirements.