Deformation behavior and formability of solid solution state Al–Li alloy in electromagnetic forming

Abstract

The combination of electromagnetic forming (EMF) and heat treatment is expected to solve a series of forming problems of Al–Li alloys with high stiffness and low density, and to improve the material strength while avoiding the accuracy deviation of components caused by quenching distortion. This paper investigates the microscopic deformation behavior and clarifies the formability improvement mechanism of solid solution state 2195 Al–Li alloy (2195-SSS) in EMF with different forming voltages and strains by means of mechanical property test and microscopic characterization. The results show that the yield strength and tensile strength of 2195-SSS are 61% and 96% higher than those of annealed state, respectively, with a better work hardening rate. The elongation after fracture of EMF for 2195-SSS is 35%, which is 52% higher than that of quasi-static tensile. In the EMF process, dislocations are prone to multi-system cross slip and sub-grains or grains have a higher degree of rotation accompanied by a slight increase in grain size. EMF forms a uniformly distributed deformation sub-structure and improves the deformation coordination ability of grain boundaries, which disperses the strain localization and effectively improves the formability of 2195-SSS. Finally, the multi-physics coupling effects of the pulsed magnetic field, pulsed electric field and high strain rate on deformation behavior are further discussed.