FABRICATION AND MECHANICAL PROPERTIES OF MICRO-POROUS METAL COMPOSITES BY MIM-BASED POWDER SPACE HOLDER METHOD

摘要

A novel production method for the metal components with micro-sized porous structures has been developed by applying powder space holder (PSH) method to metal powder injection moulding (MIM) process. The representative materials are stainless steels, aluminium, copper, titanium, nickel and their alloy. This production method can comply with widespread applications with high functionality such as heat sinks, electrodes and medical implants and so on. Those applications welcome the advantages that this method proposed is capable of producing the micro-porous metal components with complicated shapes using most kinds of metal powder. The aim of this study is to clarify the effects of material combinations on the pore formation and some physical properties of sintered porous specimens. The green compacts were molded by uniaxial hot pressing for simplification using various porous compounds which were prepared with changing the combinations in size of metal powder and space holding particle, and were sintered at various temperatures. It was confirmed that the size of metal powder and space holding particle in addition to sintered temperature was main factors affecting significantly for the pore size, porosity, surface area and shrinkage of sintered porous specimens. Furthermore, the effective method to compensate the deficiencies on the mechanical property of porous metals was investigated in comparison with mechanical properties of the materials with homogeneous dense and porous structure. Co-sintering process was applied to form the graded porous structures after each porous compound was consolidated by sequential hot press moulding. The multilayer metals were obtained by changing the stacking sequence in co-sintering process. The skin layer and core were formed with high dense structure and micro-porous structure, respectively and conversely. It was confirmed that the method proposed was useful in producing the metal components with micro-sized porous and high functionally graded porous structures.