Al-Li alloys are attractive for military and aerospace applications because their properties are superior to those of conventional Al alloys. Their exceptional properties are attributed to the addition of Li into the Al matrix, and the technical reasons for adding Li to the Al matrix are presented. The developmental history and applications of Al-Li alloys over the last few years are reviewed. The main issue of Al-Li alloys is anisotropic behavior, and the main reasons for the anisotropic tensile properties and practical methods to reduce it are also introduced. Additionally, the strengthening mechanisms and deformation behavior of Al-Li alloys are surveyed with reference to the composition, processing, and microstructure interactions. Additionally, the methods for improving the formability, strength, and fracture toughness of Al-Li alloys are investigated. These practical methods have significantly reduced the anisotropic tensile properties and improved the formability, strength, and fracture toughness of Al-Li alloys. However, additional endeavours are required to further enhance the crystallographic texture, control the anisotropic behavior, and improve the formability and damage tolerance of Al-Li alloys.
Since AA2060-T8 was introduced in the past few years, investigating the mechanical response, fracture mechanisms, and anisotropic behaviour of AA2060-T8 sheets under high strain rate deformation has been crucial. Thus, uniaxial tensile tests were performed under quasi-static, intermediate, and high strain rate conditions using universal testing machines as well as split Hopkinson tensile bars. The experimental results showed that the ductility of AA2060-T8 sheets was improved during high strain rate deformation because of the adiabatic softening and the inertia effect which contribute to slow down the necking development, and these results were verified by the fracture morphologies of high strain rate tensile samples. Furthermore, the strain rate hardening influence of AA2060-T8 was significant. Therefore, the Johnson-Cook constitutive model was modified to consider the effects of both strain and strain rates on the strain hardening coefficient. The results obtained from the improved Johnson-Cook constitutive model are in remarkable accordance with those obtained from experimental work. Thus, the improved Johnson-Cook model can predict the flow behavior of AA2060-T8 sheets at room temperature over a wide range of strain rates. The results of the present study can efficiently be used to develop a new manufacturing route based on impact hydroforming technology (IHF) to manufacture sound thin-walled-complex shape components from AA2060-T8 sheets at room temperature.
30 August 2018 in The International Journal of Advanced Manufacturing Technology
Titanium alloy sheets present inferior formability and severe springback in conventional forming processes at room temperature which greatly restrict their applications in complex-shaped components. In this paper, deformation characteristics and formability and springback behaviors of titanium alloy sheet at room temperature are systematically reviewed. Firstly, deformation characteristics of titanium alloys at room temperature are discussed, and formability improvement under high-rate forming and other methods are summarized, especially the impacting hydroforming developed by us. Then, the main advances in springback prediction and control are outlined, including the advanced constitutive models as well as the optimization of processing paths and parameters. More importantly, notable springback reduction is observed with high strain rate forming methods. Finally, potential investigation prospects for the precise forming of titanium alloy sheet in the future are suggested.