Powder Injection Molding of Al-(Steel and Magnet) Hybrid Components
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Powder injection molding (PIM) enables manufacture of complex, net shaped parts from metals, ceramics, or composite materials.[1–7] It involves mixing powders and polymer binders together to prepare feedstock. The binders enable the fine powders to be shaped using conventional plastic injection molding technology. After molding, the polymer binder is removed and the powders sintered to near full density. The PIM offers the capabilities of mass production and geometrical complexity inherent to plastic injection molding, with the material flexibility and property range available to powder processing technologies. Injection molding is among the most important techniques for commercial methods of plastics processing, and one of the rapidly expanding fields is multimaterial injection molding.[8] Multimaterial injection molding techniques can be used in conjunction with PIM to produce components specifically tailored to their function. Provided they are compatible, materials with completely different compositions can be molded and assembled at the green stage and physically bound by sintering. Recently, powder conjection molding was used to produce surface engineered components.[5–7] Two different kinds of feedstock were injected sequentially so that one formed the core of the component and the other formed the skin, such that a functionally Z.Y. LIU, formerly Research Fellow, with the School of Mechanical and Mining Engineering, ARC Centre of Excellence for Design in Light Metals, The University of Queensland, is R&D/Engineering Manager, Dou Yee Technologies Pte Ltd, Singapore, Singapore. D. KENT, Research Fellow, and G.B. SCHAFFER, Professor and Executive Dean, Faculty of Architecture, Engineering, and Information Technology, are with the School of Mechanical and Mining Engineering, ARC Centre of Excellence for Design in Light Metals, The University of Queensland, Qld 4072, Australia. Contact e-mail: [email protected] Manuscript submitted May 6, 2009. Article published online October 10, 2009 METALLURGICAL AND MATERIALS TRANSACTIONS A
graded material was produced. Another commonly used injection molding technique is overmolding, whereby plastic is injected around an insert placed into the mold cavity, which can be metal, ceramic, or another plastic material. Until now, overmolding of inserts has not been used in conjunction with PIM, as the required sintering temperatures are typically too high in relation to the properties of the insert. Potential problems include melting of metallic inserts, degradation of the properties of the insert, cracking of the components due to the coefficient of thermal expansion mismatch, and severe interfacial reactions between the insert and host material. Recently, the authors successfully developed a PIM process for the production of aluminum and Al-AlN composite components.[4,5] The relatively low sintering temperature (630 C) required to sinter aluminum presents the opportunity to use PIM in conjunction with overmolding of inserts. In this research, we explore the use of aluminum PIM with a v
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