Effect of blank size on impact hydroforming of 2195 Al-Li alloy half-tube part with curvature

Abstract

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.