Experimental investigations on deformation characteristics in microstructure level during incremental forming of AA5052 sheet

Revealing the deformation mechanism of incremental sheet forming (ISF) in microstructure level is crucial in verifying the enhanced formability, which is helpful for fabricating the panels with low-ductility materials or with complex geometry. In the present work, grain fragmentation, grain orientation, void evolution and dislocation accumulation during ISF were observed by EBSD, SEM, TEM and X-Ray microscope. Results show that the grains are elongated along the meridianal direction with obvious grain fragmentation, and the special grain gradient along thickness direction was observed. The distinct grain orientation along <110> {111} are gradually accumulated with the increasing of plastic deformation. Meanwhile, the voids are coalesced and elongated basically along meridianal direction into strip-shaped voids. The observation of TEM micrographs shows that coarse grains are transformed into fine sub-grains/grains with obvious misorientation. Multiple sets of dislocation pile-up stacked at the sub-grain boundaries is believed to increase stress concentration and tendency of micro-crack.