Effect of the Surface Defects on Hydroformability of Aluminum Alloys

Extruded aluminum alloys, which are highly versatile, have relatively modest prototyping cost, good strength and corrosion resistance. Because there is no weld seam, the circumferential mechanical properties may be uniform and advantageous for hydroforming. However, surface defects such as die lines and pick-up can be generated during the extrusion especially due to imperfections on the die surface. In this study, the extent of the crack propagation caused by die lines is evaluated according to the deformed shape of the tube in hydroforming process. And when forming a extruded aluminum tube, the deformed surface of the tube frequently becomes rougher with increasing plastic strain. This is well known as orange peel phenomenon and it has a significantly effect not only on the surface quality of a final product but also on the forming limit. To evaluate the effects of the orange peel on the hydroformability, the inter-stage polishing has been performed. Through the several tests including hydroforming test, the effect of surface defects on the hydroformabilities are well defined.