Bending in aluminium alloys AA 6111 and AA 5754 using the cantilever bend test

Abstract

Bendability is an important forming parameter in many applications, but particularly in automotive parts where the formed parts in structures can be quite complex, and where outer skins are joined to inner panels through the hemming process. In this paper the bend performance of two aluminium based automotive alloys, the heat treatable skin alloy, AA 6111 and the non-heat treatable structural alloy AA 5754, are assessed by the cantilever bend test. This test enables the loadndash;bend angle relationship to be monitored, and provides a bend surface that can be examined for different bend angles, since the bending pin does not contact the specimen surface in the local region of the bend. The results demonstrate that the cantilever bend test can differentiate between different bend performance, and the differences relate to the damage process involved in bending. In the heat treatable AA 6111 the bendability is dependent on the alloy temper, which controls the bend angle at which large surface cracks appear on the surface. This fracture process is a result of differences in the development of surface topography and surface damage with bending strain. The AA 5754 alloy has similar behaviour, but the performance is superior to the best of the AA 6111 tempers, and reflects a lower rate of surface topography development, and an absence of significant surface cracking over the bend angle range investigated.