Novelis is the world leader in rolled aluminium products and recycling, and the largest global producer of automotive sheet. To further weight saving initiatives from the automotive industry, Novelis is currently looking into roll forming as a potential manufacturing route for Al automotive parts. Roll forming is an incremental bend forming process and has been extensively studied to form high strength steel. However, very little work has been carried out on the roll formability of high strength aluminium alloys. Recent work performed by Deakin as part of a small- scale seed project with Novelis has revealed that conventional design rules developed for steel do not apply to Aluminium.
It was shown that here is a clear mismatch between the tensile Uniform Elongation/Total Elongation and the bend forming limit of high strength Aluminium. This suggests that to achieve high fracture limits in bending, the optimum alloy composition, heat treatment and microstructure is likely different to that required for high tensile ductility. In addition significant wrinkling occurred when roll forming the high aluminium alloys. This could not be reproduced by numerical models developed for steel. Initial results indicated that residual stresses and/or microstructure effects in the Aluminium strip reduce the bending yield strength and may lead to a lower buckling limit in the Aluminium compared to steel.
To enable widespread application of high strength, roll formed Aluminium components in the automotive industry new alloy design approaches need to be developed that target forming limits in bending instead of uniaxial tension. In addition to this reliable material models need to be established for CAD and FEA supported process design. For this the micromechanics that underpin fracture limits and wrinkling behaviour need to be understood.
The aim of this study is To develop the fundamental understanding of microstructure effects on the material behaviour and forming limits of Aluminium in bending dominated forming.
There are 3 major objectives:
1. Development of a fundamental understanding of the relationship between microstructure and fracture limits in bending, tension and roll forming.
2. Establishment of numerical and analytical models for process design.
3. Development of microstructure optimisation strategies to improve roll formability.
The study will establish the microstructural mechanisms that control the plane strain behaviour of 6xxx-series Al alloys. This knowledge will be used to better understand practical forming limits in the roll forming of aluminium alloys and will provide strategies to avoid defects such as wrinkling. https://www.deakin.edu.au/engineering/research/engineering-future-leaders