Controlling of the Solidification Structure for Recycling by Ultrasonic Vibration

摘要

The production of aluminum scrap is expected to exceed the domestic demand in japan around the year 2010. The key to the establishment of a "resource recycling-based society" is the zero emission process. However, recycling materials will produce an amount of scrap that cannot be recycled and will become waste. A design that considers the intended usages and includes recycling should be incorporated into the materials development to reduce as much waste as possible. Mixing iron impurities with aluminum leads to the formation of coarse needle-shaped intermetallic compounds during solidification and hinders the recycling capacity of the finished product. The application of ultrasonic vibration during solidification was carried out in this work with the aim of controlling the morphology of the material. Experiments were performed by melting an Al-Si alloy containing 4 mass% Fe (hereafter, mass% is abbreviated by %). The primary crystals formed from the liquidus line of this alloy were intermetallic compounds identified as Al_3Fe, α-AlSiFe (Al_(7.4)SiFe_2) and P-AlSiFe (Al_9Si_2Fe_2). A coarse needle-like intermetallic compound was formed in the Al-6Si-4Fe and Al-12Si-4Fe alloys, but the application of ultrasonic vibration resulted in the formation of a fine grained structure. In the Al-18Si-4Fe alloy, the structure could be modified from a coarse needle-like structure into a fine grained structure.