Influence of Process Parameters on Twin Roll Cast Strip of the Alloy AZ31

Reducing vehicle weight and emissions by lightweight design is a major goal of the automotive industry. Magnesium as the lightest structural metal offers a significant weight saving potential compared to steel and aluminium. Cast magnesium components are widely used, e.g. as engine blocks or gear box housings. The application of magnesium sheets is currently hampered by the low formability of magnesium which means that a large number of rolling passes is required to roll a DC cast slab to final gauge sheet. This large number of rolling steps is the main reason for the high cost of magnesium sheets. Twin-roll casting (TRC) is an alternative, economic production process for the generation of fine-grained feedstock materials that subsequently can be warm rolled to thin sheets. It therefore receives attention in actual research and development projects for the application of magnesium alloys as prospective light metal solutions. This production process for thin strips combines solidification and rolling into one single production step and therefore saves a number of rolling and annealing passes in comparison to the conventional rolling process. The main goal of the activities at the Magnesium Innovation Centre MagIC of the Helmholtz-Centre Geesthacht (HZG) is the development of wrought magnesium alloys and their introduction into industrial, structural applications. The current focus of the research work is on alloy design and their processing for magnesium sheets produced by twin roll casting. In order to understand the influence of process parameters on the microstructure and texture the first twin roll casting experiments were performed with the alloy AZ31 (Mg-3Al-1Zn-Mn) as benchmark. As an example, the influence of melt temperature on the microstructure of the strip is presented and discussed with respect to arising material properties. Optimisation of process parameters of twin roll casting and the subsequent rolling of the sheets, offers the possibility to produce high quality sheet material.