Consolidation of Ti-SiC particle-reinforced metal-matrix composites

Abstract

Discontinuously-reinforced metal-matrix composites (DMMC) have received an increasing amount of attention in recent years due to their improved strength, stiffness and wear characteristics. These benefits make DMMC quite appealing for many structural applications; however, limited ductility and toughness have prevented their widespread use. Limited ductility and toughness are not unique to this class of advanced materials and are shared by such systems as continuous fiber composites and monolithic ceramics. The introduction of weak microstructural features in these materials has long been known to enhance the overall fracture properties. These features have taken on many forms depending on the system involved; for example, microcracking grain boundaries in ceramics (1) and weakened interracial strengths in continuous fiber composites (2). This approach has proven to be quite effective for a wide variety of materials but remains relatively unexplored for DMMC. It has been assumed that the greatest interracial strength obtainable will produce an optimized mechanical response. This assumption has not been challenged to any significant degree mainly because of the experimental inability to effectively vary the interfacial characteristics using standard processing procedures. The ability to control the evolution of matrix-reinforcement interfaces in DMMC through various processing parameters is of critical importance for both scientific investigations and industrial applications. The extremely short time at the compaction temperature that can be achieved with shock consolidation make it a unique method for the minimization (and subsequent systematic variation) of interracial reactions. Because of the high reactivity of Ti with the readily available reinforcement particles, this system possesses significant potential for gain from improved interfacial control. The fundamental questions concerning the "optimum" interfacial strength for a given DMMC can be systematically investigated with these reactive composite materials. The objective of this study was to produce fully dense DMMC compacts comprised of a reactive particle-matrix combination with little or no interfacial reactions in the as-consolidated condition. This material can provide unique information regarding the role of interfaces in DMMC.

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