MANUFACTURING OF CERAMIC PREFORMS FOR ALMMC

摘要

Aluminum Metal Matrix Composites (AlMMC) is an important class of composite materials.AlMMC’s has been gaining more interest and acceptance during the past 30 years. A sub-category of thismaterial class is Discontinuous Reinforced Aluminum (DRA). These AlMMC materials contain analuminum matrix reinforced with ceramic particles, whiskers, or short fibers. The DRA AlMMC has beensuccessfully used in the aerospace, automotive, electronic packaging, and recreational product markets. TheDRA AlMMC is an interesting material because it offers a unique set of materials characteristics. Thesecharacteristics include low density; higher wear resistance than steel, a coefficient of thermal expansion(CTE) that can be tailored and finally high stiffness, on the order of titanium. The process of making DRAALMMC components includes the manufacture of a ceramic preform followed by the infiltration of thepreform with molten aluminum alloy. As interesting as theses materials properties are however, thesematerials have only been used in niche applications.One of the major barriers that limited the growth of the DRA AlMMC market is the inability to obtainreliable, high quality, cost effective source of ceramic preforms. Traditional ceramic forming methodsinclude slip casting, uni-axial pressing, and cold iso-static pressing. Each of these processes is wellestablished in the ceramic forming industry and each offers it own set of unique advantages anddisadvantages with respect to DRA AlMMC preform manufacture. However these traditional formingmethods do not offer the ability to produce high volume, complex shape, near net shape components. TheSpringboard CIM process is capable of meeting and exceeding these requirements. It also allows one theability to design components with multiple materials in one component, and a host of unique materialsmicrostructural features.To date, the typical CIM process has been used with limited success due to both the poor economics andinability to manufacture large (I.e. larger than a golf ball) complex shape (three dimensional), high qualitypreforms. The economics are limited by the debinding stage. Namely, unless one can injection mold apreform component, place it on a plate or setter plate and subsequently debind and sinter it in the sameoperation without handling, dangerous solvents etc., it is very difficult to envision that this process willever become a viable option for manufacturing high volume, complex shape DRA AlMMC preforms.Springboard CIM has identified the needs of this industry and has developed a process that is robust, costefficient, and last but not least, capable of meeting the high quality standards required to move this industryforward. In this paper, we will review the Springboard CIM process and describe the advantages that thisprocess has to offer over the existing CIM technologies. A detailed discussion of the Springboard CIMmaterials, equipment, processing conditions, and dimensional tolerances will be presented.