Effect of Ca Addition on the Intensity of the Rare Earth Texture Component in Extruded Magnesium Alloys

Extruded Mg alloys usually display strong basal fiber textures, which are related to poor formability. Inspired by the texture weakening effect of the addition of rare earths (RE) to Mg alloys, two Mg-Ca alloys were designed and a range of extrusion conditions were explored in attempts to reproduce this effect. Constant strain rate and strain rate change compression tests were performed on the specially prepared Mg-0.5Ca and Mg-1Ca alloys. Dynamic strain aging (DSA) was observed to take place in both alloys over a well-defined temperature and strain rate range. Seven extrusion trials were then carried out on the Mg-0.5Ca alloy within and external to the DSA range of conditions. From the resulting textures and microstructures, it is concluded that the 〈11−21〉 (RE) texture component is formed when extrusion is carried out while DSA is taking place. The occurrence of this type of texture weakening is attributed to the promotion of recrystallization within the shear bands formed when the rate sensitivity is negative. The latter in turn arises because of the DSA taking place in the presence of solute Ca.