Melt-infiltration processing of TiC/Ni 3 Al composites
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Melt-infiltration processing of TiCyyNi3 Al composites K. P. Plucknett, P. F. Becher, and R. Subramanian Metals and Ceramics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (Received 13 January 1997; accepted 17 March 1997)
A simple melt-infiltration processing route has been developed for the fabrication of TiCyNi3 Al ceramic/intermetallic composites, which involves a combination of infiltration and subsequent liquid phase sintering. For Ni3 Al contents from 8 to 25 vol. %, densities in excess of 98% of theoretical are readily obtained when processing at 1450 ±C. TiC and Ni3 Al are the only phases detected in the densified materials. Ni3 Al ductility is retained after processing, leading to the possibility of ductile phase toughened TiC composites for elevated temperature applications (up to ,1100 ±C).
The fracture resistance of brittle ceramics can be significantly increased by the incorporation of ductile metal reinforcements.1,2 A favorable processing route for preparing these ceramic/metal composites is meltinfiltration,3–6 which can be either “pressureless,” in the case of wetting systems,3–5 or pressure-assisted for poorly wetting systems.6 Understandably, the former approach is the most favorable for commercial processing, and is commonly used for the fabrication of siliconized silicon carbide (Si–SiC).7 For wetting systems, where the contact angle of the molten metal on the ceramic is considerably less than 90±, capillary pressure provides the infiltration driving force.8,9 Pressureless meltinfiltration studies have been performed on a number of “model” ceramic/metal systems, including the infiltration of Al into TiC4,9 and AlN,3 as well as infiltration of Al2 O3 by Cu(O) alloys.5 Due to the use of Al or Cu infiltrants, these systems are limited to relatively low-temperature applications (,700 ±C). In the present work, fabrication of TiCyNi3 Al composites by melt infiltration is described. This is a wetting system, with a contact angle of 10 to 20±.10,11 Additionally, TiCyNi3 Al composites have the potential for applications up to ,1100 ±C and can be electro-discharge machined. This approach has been used to fabricate materials with Ni3 Al contents from 4 to 25 vol. %, and is similar to the route recently reported for TiCyFeAl composites.12 Composites have been prepared using a commercially available TiC powder (Kennametal, Latrobe, PA), with a measured particle size range of 0.5 to 5 mm. The Ni3 Al “infiltrant” powder (alloy IC-50, classified to 260y1325 mesh, Homogeneous Metals, Inc., Clayville, NY), contained principal alloying additions (in at. %) of ,77.83 Ni, 21.73 Al, 0.34 Zr, and 0.10 B. TiC preforms were uniaxially cold pressed at ,90 MPa, followed by cold-isostatic pressing at ,285 MPa, giving a green density of ,63% of theoretical. Compacts were placed on high purity alumina powder (99.99%) J. Mater. Res., Vol. 12, No. 10, Oct 1997
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in an alumina crucible, which in turn was
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