Al-TiC composites in situ -processed by ingot metallurgy and rapid solidification technology: Part II. Mechanical behavi
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ODUCTION
METAL matrices reinforced with ceramic particles have been developed in recent years for various automobile and other structural applications. Different particles such as SiC, Al2O3, TiB2, B4C, and TiC[1–5] have been recognized as potential reinforcements for metal, as the dispersion of these particles enhances the elastic modulus, hardness, tensile strength at room and elevated temperatures, and wear resistance of the alloys. The particle-reinforced composites are conventionally prepared either by powder technology or liquid metallurgy, where the ceramic particles are directly incorporated into solid or liquid matrices, respectively. However, metal matrices reinforced with ceramic particles formed in situ are an emerging group of discontinuously reinforced composites that have distinct advantages over the conventional composites.[6,7] Both liquid-phase and solid-phase processes are being studied to produce in situ particle composites based on metal matrices. In liquid-phase processes, a solid, liquid, or gaseous phase is introduced into a liquid metal/alloy to react with the base metal or its alloying elements and, hence, to produce reinforcement phases. In solid-phase processes, elements or elements/compounds are blended, compacted, and heated at a selected temperature to form the desired reinforcements. Both techniques produce very fine reinforcements in the matrices. The interfaces are clean and are semicoherent in some cases. The mechanical properties of in situ composites are comparable to or better than those of conventional composites. X.C. TONG, formerly Postdoctoral Student, Department of Materials Science and Engineering, Tsinghua University, is Research Fellow, Department of Materials Science and Engineering, University of Michigan, Ann Arbor, MI 48109-2136. H.S. FANG, Professor, is with the Department of Materials Science and Engineering, Tsinghua University, Beijing 100084, People’s Republic of China. Manuscript submitted February 13, 1997. METALLURGICAL AND MATERIALS TRANSACTIONS A
In the present work, we highlight a novel in situ process in which traditional ingot metallurgy (IM) plus rapid solidification (RS) techniques are used to produce Al-TiC composites with refined microstructures and enhanced dispersion hardening of the reinforcing phases. In Part I of this investigation,[8] the microstructural evolution of the in situ Al-TiC composites was examined. The purpose of the present study is to develop high-strength–type Al-Si/TiC composites and elevated-temperature-resistance–type Al-Fe(V-Si)/TiC composites based on the preparation of the in situ Al-TiC composites. In particular, the room- and elevatedtemperature mechanical behavior have been evaluated. II.
EXPERIMENTAL PROCEDURE
The materials and related parameters used in this study are summarized in Table I. Details of the material preparation procedure and the chemical composition, as well as microstructural characterization studies, are given in Part I of this investigation.[8] In Table I, the ribbons of RA20* and RAF2* were milled
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