Solid-state recycling from machined scraps to a cellular solid
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Cellular solids were processed from machined scraps of a medium carbon steel by sintering. Mechanical properties of the cellular solids were investigated by compressive tests from the viewpoint of effects of high dislocation density in the machined scraps on the solid-state bonding. The flow stress in the plateau region for the cellular solid made of the as-machined scraps was higher than that of the one made of the annealed scraps. Clearly, the bonding strength between scraps was increased by the high dislocation density in the as-machined scraps.
Recycling of metals is one of the most important technologies for materials circulation because of their large consumption.1 At the present time, a typical recycling process for metals is a remelting process by using redox reaction. For the remelting process, a large energy consumption is needed. Furthermore, metals recycled by the remelting process show poorer properties than virgin ones due to contaminations of oxide inclusions and tramp elements.2–4 The desirable recycling involves recycling from scraps to high-performance materials with lowenergy consumption. One of the solutions for such low-energy recycling is application of the internal energy stored in scraps. In this communication, we show recycling from machined-steel scraps to a cellular solid exhibiting the high-energy absorption potential by application of the internal energy stored in scraps without the remelting process. Cellular solids are superlight materials exhibiting unique properties5–10 such as high-energy absorption ability5 and nonlinear damping properties.7 Applications of cellular solids occur in a wide range of impact absorbers, engine exhaust mufflers, and so on. To date, some manufacturing methods11–13 for cellular metals have been developed, for example, the gas releasing particle decomposition in melt and investment casting. However, these manufacturing processes are very complicated, resulting in high cost. Cellular solids have a lot of pores. The pores are considered to be large defects. This means that cellular solids have inherent defects. Hence, even if defects such as contaminations are contained during the recycling process, mechanical properties of a cellular solid are
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Address all correspondence to this author. e-mail: [email protected] J. Mater. Res., Vol. 17, No. 11, Nov 2002
hardly affected by the acquired defects. This gives rise to an idea of low-cost recycling from scraps to highperformance cellular solids. Also, recycling with steel scraps largely contributes to materials circulation in a global level. In this investigation, cellular solids are processed from machined scraps of a commercial medium carbon steel by sintering the chips and mechanical properties of the cellular solids are investigated by compressive tests from the viewpoint of effects of high dislocation density in the machined scraps on the solid-state bonding. Machined scraps of a commercial medium carbon steel (Fe–0.45 mass% C) were used. The scraps were remnants after machining the steel. The external a
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