The influence of warm forming in natural aging and springback of Al-Mg-Si alloys

Warm forming is a very interesting solution to improve formability and reduce springback. Natural aging is an open issue for heat treatable aluminum alloys, since it causes variability in sheet metal forming operations, namely in the parts shape, as well as in-service behavior. Therefore, this work aims to study the contribution of warm forming to minimize the variability caused by natural aging and reduce the springback in sheet metal forming operations. The thermo-mechanical behavior of two Al-Mg-Si alloys, EN AW 6016-T4 and EN AW 6061-T6, is studied in function of temperature (from 22 to 300 °C) using uniaxial tensile tests, cylindrical cup tests and split ring (springback) tests. Moreover, for the EN AW 6016-T4, the study was also performed in function of the storage time (from 1 to 18 months). At 22 °C, the increase of the storage time leads to a clear increase of the yield stress and of the work hardening and, consequently, of the springback. Warm forming at temperatures between 200 and 250 °C, using a short exposure time, reduces the yield stress and the work hardening and, consequently, springback for both alloys. Moreover, the effect of natural aging is minimized. Thus, warm conditions can be used as an effective solution to minimize the variability caused by the natural aging and reduce the springback in forming operations of heat treatable aluminum alloys.