Microstructure and Texture of MX20 after Conventional Rolling and Rolling from Twin Rolled Cast Strip

Abstract

Two main impediments are currenty discussed with respect to the industrial application of magnesium sheets. First, the low formability of magnesium sheets requires many rolling passes to roll cast slabs to final gauge, which leads, second, to high costs for the production of magnesium sheets. An alternative cost-saving process chain for magnesium sheets with enhanced properties is the feedstock production by twin roll casting (TRC). In the TRC process, liquid metal proceeds from a furnace over a pipe into a crucible and then flows between a pair of counter rotating, internally cooled rolls. The metal solidifies upon touch with the cooled rolls and gets rolled to a strip. This paper refers to the comparison of the two processing routes on the example of the aluminum-free magnesium alloy MX20 (2 wt% Mn and 0.5 wt% Ca). Both kinds of production processes like casting and twin roll casting have an influence on the microstructure and texture of the feedstock material for the subsequent rolling process. The paper reports on the results of casting and twin roll casting experiments of this alloy. Furthermore, rolling trials are conducted and the deformation behavior of the sheets are presented and discussed with respect to the developed microstructures and textures. The different morphology of precipitates in the cast and twin roll cast feedstock material is used to improve the ductility of the magnesium alloy MX20.