Solid state recycling from green wastes to aluminum alloys with high material efficiency

All recyclable materials such as the used mechanical parts or home-housing members are melt, solidified and wrought to down-graded materials in the conventional recycling. Solid-state recycling is a promising approach to accept the mechanical chips and wastes generated in production as input and to yield the upgraded alloys and compounds as output. This new approach requires innovative processing to fabricate the targeting products via in-process refinement and control of microstructure as needed from the product design. In the present paper, the bulk mechanical alloying process is used for solid state recycling to make microstructure refinement from the mechanical chips to a dense powder compact. In experiment, Al-Si system is employed as a typical material for automotive parts, which must satisfy the requirement of fine Si-particulate size in the final product. Together with refinement experiment, the plastic power history imposed to a sample is continuously monitored during bulk mechanical alloying to be compared with the total energy consumption in the commercial production line from atomizing process to preliminary sintering. The number of cycles required to attain the largest Si-size demand of 7 μm was only 100, so that the energy consumption could be reduced from that needed by the conventional powder metallurgy process working in industry. The present method is robust in processing even when varying the morphology and Si concentration in the input materials.