Interactions between SiC fibers and a titanium alloy during infrared liquid infiltration
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INTRODUCTION
TITANIUM matrix composites are strong candidates for applications in the aerospace industry primarily because of their high specific strength and modulus, good dimensional stability, and retention of strength at elevated temperatures. These composites are commonly fabricated by solid-state diffusion-bonding processes such as vacuum hot pressing or hot isostatic pressing. [1'2,31 However, long processing times at elevated temperatures in these processes often result in extensive interracial reactions in as-fabricated composites. Meanwhile, the high operating cost along with pressurizing and vacuum requirements make diffusion-bonded composites expensive materials. Liquid infiltration is a relatively low-cost technique for fabricating metal-matrix composites. However, because of severe reactions between liquid titanium and reinforcing fibers during fabrication, this technique has not received much attention in the manufacture of titanium-matrix composites. Toloui t4~attempted to lbroduce carbon fiber-reinforced titanium alloy composites using an induction heating method. Composites fabricated by this method revealed severely degraded fibers and poor mechanical properties. No other attempts to fabricate either carbon fiber or SiC fiber-reinforced titanium alloy composites by the liquid infiltration technique have been reported. Toloui's results E41suggest that in order to ensure the success of the liquid infiltration process, methods of minimizing the reaction at the interface during composite fabrication must be developed. These may include shortening the processing time, providing protective coating on the reinforcement fibers, or incorporating alloying elements that retard the reaction. In an effort to reduce the processing time, a rapid infrared manufacturing (RIM) process has been developed at the SUNIL G. WARRIER, Postdoctoral Fellow, and RAY Y. LIN, Professor, are with the Department of Materials Science and Engineering, University of Cincinnati, Cincinnati, OH 45221. Manuscript submitted February 28, 1994. METALLURGICALAND MATERIALSTRANSACTIONSA
University of Cincinnati, Cincinnati, OH. t5-1~ With this process, the alloy and the fibers can be heated in an infrared furnace under an argon atmosphere at rates in the order of 100 ~ to 200 ~ to temperatures above the melting point of the alloy. The entire composite fabrication process is typically completed in only I to 2 minutes, as opposed to several hours in conventional diffusion-bonding processes. Since the total time that the liquid alloy remains in contact with the fiber preform is very short, reactions at the fiber-matrix interface of highly reactive titanium-ceramic systems can be effectively controlled. Another major advantage of the fast heating rate is reduced metal oxidation that results in the enhancement of wetting and flow properties of the liquid alloy. The absence of thick oxide layers and the inherent low viscosity of liquid metals (typically around 10 -3 Pa s, similar to that of water) t111permit infiltration of 4-ply fiber pre
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