The new die cast (HPDC) wheel alloy has been developed using recycled aluminum to attain considerable reduction of energy at the time of material production to make large contribution to the reduction of CO2 emissions.
The material for motorcycle body parts, especially for wheels, requires a sufficient elongation property. However, when recycled aluminum, which contains large amount of impurities, is used as main raw material, the intermetallic compounds crystalize out and the elongation property is deteriorated. Accordingly, we firstly made the investigations on the elements contained in a recycled aluminum and it was clarified that the elongation property was correlated to the shape of crystallized iron-based intermetallic compounds. Next, it also clarified that addition of manganese (Mn) improved the elongation property by changing the shape of crystallized iron-based intermetallic compounds from the plate form to the clumped form, followed by determination of the optimum content of Mn to prevent coarsening of the compounds. Additionally, it was clarified that the shape and size of crystalized iron-based intermetallic compounds significantly influenced by the solidification rate when casting products. To analyze the solidification process, we developed a simulation method to estimate the size of metal structures. Through this method, it was made possible to determine the casting design and the casting conditions in actual productions.
As a result, 97% reduction of CO2 emission in the material production was achieved with recycled alloy compared to virgin ingots.