Interface Reaction in SiC Reinforced Al 3 Ti-Based Intermetallic Matrix Composites
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INTERFACE REACTION IN SiC REINFORCED AhsTi-BASED INTERMETALLIC MATRIX COMPOSITES JIAN WANG, QIAN WANG, SHIPU CHEN, JIAN SUN AND GENGXIANG HU Department of Materials Science, Shanghai Jiao Tong University, Shanghai 200030, China ABSTRACT The AhTi-based L1 2 intermetallic alloy Al.eFeeTi2 6 has shown low density, high oxidation resistance, good strength and appreciable compression ductility at room temperature. To explore the approach of combined toughening and strengthening of this alloy, composites are being studied. The interface reactions between A16 6FevTi25 matrix and SiC reinforcement material during different fabrication processes were investigated using SEM, EDS, EPA and X-ray diffraction analyses. The extent of reaction was determined and the reaction products were identified. It was found that SiC is chemically incompatible with the A16 6FegTi2 6 matrix, strong interfacial reactions occurred during fabrication and the formation of ternary compounds leads to the deterioration of the matrix alloy. INTRODUCTION Although the DO 22 intermetallic compound AhTi has attractive characteristics such as low density, excellent oxidation resistance and relatively good strength, it is extremely brittle at ambient temperature[l]. A generally accepted approach to improve the ductility of the compound is to change its DO 22 tetragonal structure to the cubic L1 2 structure by alloying with Fe, Mn, Cr, Cu etc [2-4]. The L1 2 AlhTi-based intermetallic alloys have shown appreciable compression ductility at room temperature, while they are still brittle in tension [5,61. Therefore, further investigations are being carried on to explore the approach of combined toughening and strengthening for these alloys. In addition to research on monolithic L1 2 AhTi alloys [61, composites of A1sTi-based alloys are also under investigation in our laboratory. It is known that the interfacial reactions between reinforcement and matrix during fabrication, or at elevated service temperatures, play an important role in the mechanical properties of metal matrix composites. The purpose of the present paper is to address the interfacial reactions in the SiC/Al1sFegTi 26 composites and the effects of consolidation process on the reactions, so as to provide information required for the development of AhTi-based intermetallic matrix composites. EXPERIMENTAL The matrix alloy is a Liz structure AhTi-based compound with nominal composition AloFeoTi 2s(at.%), which was prepared by arc-melting in argon on a water-cooled copper hearth. The cast buttons were used as master material for fabricating the composites. The composites were fabricated by different techniques for comparison: (1) Pieces of A1 6 FegTi 2s alloy mixed with tiny SiC crystallites (-imm) were arc-remelted in argon on the water-cooled copper hearth. The reason for using SiC crystallites instead of particulates is that a larger area of interface can be obtained for the convenience of inspection. (2) AI 6 FeTi 25 powders (-320 mesh) produced by ball-milling were mechanically blended into a mixt
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