Fabrication of Intermetallic Fiber/Metal Matrix Graded and/or Smart Composites by a Reaction at Narrow Holes Method

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The reaction at narrow holes method (RANH method) has been proposed as a method for fabricating an intermetallic compound fiber/metal matrix composite. Narrow holes having a small diameter are drilled in a metal matrix A. Metal fibers B are inserted into these narrow holes. The assembly comprising the metal matrix A and metal fibers B is heated at elevated temperatures to obtain molten metal B in the narrow holes. Then, the reaction of mA+nB→AmBn should occur at least in the narrow holes. After the processing, the assembly is cooled to ambient temperature. Consequently, the intermetallic compound AmBn fiber/metal matrix A composite can be fabricated.In this study, a nickel-aluminides fiber/nickel composite and a copper-aluminum system composite are fabricated by the novel method, RANH method. The results are summarized as follows.Nickel-aluminides fiber/nickel composite1)Reacted region is limited to the fiber shaped region, since the nickel-aluminide replaces the pure aluminum maintaining its fiber shape surrounded by the nickel matrix.2)High hardness could be achieved for specimens beat-treated at 1000 ℃.3)Specimens heat-treated at 1000 ℃ and 1200 ℃ have lots of pores.Copper-aluminum system composite1)Double annular regions are formed around the hole by heating at a temperature less than about 700 ℃. The inner annular region consists of γ1 intermetallic compound in a single phase having very high hardness. The outer annular region consists of Al-Cu solid-solution having a mid-level hardness. The annular regions may work as a reinforcing metal fiber in FRM.2)When the annular region is formed with a constant width along the edge of the hole, the resultant specimen has the hole maintaining its circular section shape of the original narrow hole.