Microstructure difference of 5052 aluminum alloys under conventional drawing and electromagnetic pulse assisted incremental drawing

In the electromagnetic pulse assisted incremental drawing (EMPAID) process, the sheet metal was alternatively deformed under quasi-static and high speed conditions, whereas the formed cylindrical cup height increased remarkably. In order for the sheet metal plastic properties increase reasons and the deformation mechanism to be understood, in this work, the deformation behavior and the microstructure evolution of 5052 aluminum alloys were compared with the conventional drawing by micro hardness analysis, the electron back scattering diffraction (EBSD) observations and the transmission electron microscopy (TEM) studies. The results demonstrated that under the EMPAID, the cylindrical cup micro hardness exceeded the conventional drawing micro hardness. The EBSD observations displayed that in the EMPAID process, the grain shapes apparently changed: among these observations, under the uniaxial tensile stress, the grains in the cylindrical wall region were elongated; whereas in the region of the die corner and the end of the flange, the grains became flat under the axial and radial compressive stress. The TEM observations demonstrated that the plastic deformation mechanism of the 5052 aluminum alloys was the dislocation-slip under both conditions. Furthermore, the dislocation density significantly increased subsequently to EMPAID, whereas the corresponding distribution was quite uniform. Also, the slip bands and the equiaxed grains also appeared in the local area and consequently the plasticity of the formed part could be improved.