An experimental and theoretical investigation of the rapid consolidation of continuously reinforced, metal-matrix Compos
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I.
INTRODUCTION
CONTINUOUSLY reinforced, titanium-matrix composites (TMCs) are potential candidates to replace monolithic materials in high-temperature applications, because they exhibit an attractive combination of properties such as low density, high strength-to-weight ratio, and excellent corrosion resistance. Because of the high reactivity of molten titanium, TMCs are generally fabricated by solid-state processing techniques. These methods include the foil/fiber/foil approach in which alternating layers of foil and fiber mats are stacked and hot isostatic pressed to give a fully dense product.m Similar techniques comprise the hot isostatic pressing (HIP) or vacuum hot pressing (VHP) ofmonotapes or coated fibers, which contain both matrix and reinforcement material and which are manufactured via plasma spraying,t2j tape casting,t3.4]physical vapor deposition, E51etc. The high costs associated with the starting materials, the use of specialized consolidation equipment, and the long consolidation cycle times (typically several to many hours) are among the reasons for the delayed introduction of TMCs into service as accepted engineering materials. By contrast, conventional forging as an alternate consolidation process is very attractive from a processing cost standpoint,
P.D. NICOLAOU, Visiting Scientist, and S.L. SEMIATIN, Senior Scientist, are with the Metals and Ceramics Division, Materials Directorate, Wright Laboratory, WL/MLLN, Wright-Patterson Air Force Base, OH 45433-7817. R.L. GOETZ, Scientist, is with the Materials Manufacturing and Processing Division, UES, Inc., Dayton, OH 454321894. Manuscript submitted April 12, 1995.
METALLURGICAL AND MATERIALSTRANSACTIONS A
because densification would be done in seconds rather than hours and conventional press equipment could be used. The objectives of the present work were to establish the feasibility of fabricating continuous-fiber, metal matrix composites via a forging approach; to identify the important design parameters for successful forge consolidation of these materials; and to determine the quality of the finished product by assessing the tensile properties of forge-consolidated composites and comparing them to the properties of materials processed by conventional routes. II.
PROCEDURES
A series of experimental and theoretical investigations was conducted to elucidate the critical issues during rapid consolidation of continuous-fber, metal matrix composites and to demonstrate that microstructures and properties equivalent to those from conventional processing approaches can be realized by this means. The experimental work consisted of rapid-consolidation trials based on a forging method followed by metallography and room-temperature tension testing. Lumped-parameter heat-transfer analysis and finite-element-method (FEM) analysis were conducted to obtain insight into temperature transients, consolidation pressures, and the occurrence of fiber fracture during the forging operation. A. Materials and Experimental Procedures
The metal-matrix composite sy
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