Experimental investigations on friction stir assisted single point incremental forming of low-ductility aluminum alloy sheet for higher formability with reasonable surface quality

Formability of metallic sheet has always been a research focus in incremental sheet forming (ISF), especially for lower-ductility materials. Friction stir assisted ISF (FS-ISF) can effectively improve the local temperature of the sheet and formability. However, high-speed friction between the tool and the deforming sheet metal might cause bad surface quality, and process parameters have contradictory effects to formability and surface quality. To solve this puzzle, the effects of four factors on forming temperature and surface quality were analyzed by orthogonal experiments for FS-ISF of a truncated cone with constant wall angle of AA2024-T. Two surface defects of FS-ISF were analyzed and a process window for FS-ISF was proposed for higher forming temperature with reasonable surface quality. The applicability of process window proposed was verified by FS-ISF of another truncated cone with varied wall angle using AA2024-T and AA5052-H32. Through process optimization, the formability has been greatly improved while ensuring reasonable surface quality at the same time.