Analysis of microstructure and microhardness of aluminum alloy melt for grain refinement by twin-roll casting

Abstract

This study examines sheets produced using twin-roll casting (TRC) and melt conditioned twin-roll casting (MCTRC) to evaluate the effect of melt conditioning on segregation pattern and grain refinement. To produce sheets through the MTCRC technique, melt conditioning using high shear technology (high-speed rotor) was applied to Al-5 Mg alloys, before subjecting the melt to TRC. A low shear slope was used to prepare a commercially pure aluminum ingot. The mean grain size obtained for slope processed samples with vibration at a pouring temperature of 780°C is 69.4 µm, decreasing to 62.5 µm with a 20°C decrease in pouring temperature. Samples prepared without vibration at temperatures of 780°C and 760°C exhibit grain sizes of 85.172 and 77.8 µm, respectively. Additionally, the average grain size of Al-5 Mg alloy sheets produced using TRC is around 270 µm, which decreases to 230 µm for sheets produced using MCTRC. The grain size data comparison of the samples prepared using high shear technology and those with a low shear slope indicate successful results of grain refinement in both cases. However, it is advantageous to produce sheets using the low shear slope method as compared to the high shear technology, because of the low setup costs.