Assessing the impact of texture and its gradients on the forming limits of an aa6xxx sheet alloy

Abstract

The automotive industry has long been interested in Al alloy sheet material for body construction to reduce weight. Nevertheless, it is important to get a deeper understanding of the formability of Al alloys to further this application. Previous studies have illustrated that the initial texture and its evolution during forming can significantly affect the formability. Here, the effect of texture gradients, within commercially processed AA6xxx series alloys sheets, on predicted forming limit curves (FLCs) is examined. Experimental measurements at the surface, 1/6th, 1/3rd and mid-plane reveal that all the materials examined possess recrystallization textures, with Sample #4 having the weakest and Sample #2 the strongest intensity. Sample #2 also exhibited the strongest texture gradient where the surface is comprised of strong cube texture while the interior also possesses a fibre texture with Goss component. The experimental textures were used as inputs to a Marciniak–Kuczynski (M–K) based viscoplastic self-consistent (VPSC) polycrystal plasticity code for FLC prediction. The absolute level of formability was observed to vary within the samples. Discrepancies on the stretching side are due to the deviation from proportional loading in the Nakajima test, which is not accounted for in the model. Simulations carried out using textures from specific sections confirm a previously observed phenomenon that the cube texture enhances the formability on the stretching side whereas the Goss component degrades it.