Microstructure evolution of aluminum alloy under quasi-static, mechanical dynamic, and electromagnetic dynamic deformation

It has been widely confirmed that the formability of lightweight but difficult-to-form metals is significantly improved during electromagnetic forming. However, the physical nature of the improvement for material formability is controversial. This work applied quasi-static, mechanical dynamic, and electromagnetic dynamic loading to 2219 aluminum alloy to partially decouple the relevant mechanisms during electromagnetic forming. The specific influence of strain, strain rate and inertial effect, pulsed magnetic field and eddy current on the microstructure evolution were analyzed. The results show that compared with quasi-static deformation, the uniaxial tensile limit strain of material is increased by 26% under mechanical dynamic deformation and 41% under electromagnetic dynamic deformation. The inertial effect during high-speed deformation scatters the development of defects and the local instabilities, thus improving the formability of the material. In addition, as strain increases, the material's microstructure evolves through dislocation multiplication, grain refinement, increased low angle grain boundary, geometrically necessary dislocation density and texture intensity, decreased Schmidt factor, and formation of numerous dislocation cells. The pulsed magnetic field and induced eddy current can promote the transformation from dislocation cells to sub-grains, which further improves the deformation coordination and the formability of material.