Melt infiltration casting of bulk metallic-glass matrix composites
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Melt infiltration casting of bulk metallic-glass matrix composites R. B. Dandliker, R. D. Conner, and W. L. Johnson W. M. Keck Laboratory of Engineering Materials, Mail Code 138-78, California Institute of Technology, Pasadena, California 91125 (Received 5 May 1997; accepted 5 January 1998)
The authors describe a technique for melt infiltration casting of composites with a metallic-glass matrix. We made rods 5 cm in length and 7 mm in diameter. The samples were reinforced by continuous metal wires, tungsten powder, or silicon carbide particulate preforms. The most easily processed composites were those reinforced with tungsten and carbon steel continuous wire reinforcement. The Zr41.2 Ti13.8 Cu12.5 Ni10.0 Be22.5 matrix was quenched to a glass after infiltrating the reinforcement. We analyzed the microstructure of the composites by x-ray diffraction and scanning electron microscopy. The measured porosity was less than 3% and the matrix was about 97% amorphous material.
I. INTRODUCTION
II. EXPERIMENTAL
Metallic glasses are usually made by rapidly solidifying certain alloys. Most alloys investigated require cooling rates of 105 Kys or higher to freeze from the melt to the metastable amorphous state. The high heat transfer rate required limits these metallic glasses to thin samples produced by such techniques as splat quenching or melt spinning.1,2 The melt spinning technique has often been used to make amorphous metal matrix composites. Particulate reinforcements have been added to a liquid glass-forming metal alloy and processed with a number of techniques to make composite ribbons.3 –7 Wire and continuous fiber reinforcement of metallic glass ribbons have also been reported, although the best results have yielded a ribbon reinforced with only two continuous wires.5,8,9 So-called “bulk” metallic glasses, alloys with critical cooling rates of 102 Kys or less, are much more promising as potential matrix materials for composites. These glass-forming alloys are not limited to thin geometries.10 –14 One of the most highly processible of these alloys is Zr41.2 Ti13.8 Cu12.5 Ni10.0 Be22.5 , which has a critical cooling rate of about 1 Kys with no fluxing required.15 Fully amorphous rods of this alloy of up to 5 cm in diameter have been cast. This amorphous alloy has a yield point of about 1.9 GPa, which is substantially higher than most crystalline metals. In addition, it exhibits approximately 2% elastic strain, again far greater than crystalline materials. These superior mechanical properties and the low critical cooling rate of this bulk metallic glass are the primary reasons for its promise as a new engineering material.16 –19 This study reports a technique for successfully using the alloy Zr41.2 Ti13.8 Cu12.5 Ni10.0 Be22.5 as a matrix material for composites. The low critical cooling rate of this alloy allows amorphous metal matrix composites to be made in bulk form.
In this study we used exclusively the Zr41.2 Ti13.8 Cu12.5 Ni10.0 Be22.5 (trade name VitreloyTM 1) devel
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