Evaluation of Various Intermetallic Matrix - Ceramic Particle Systems for Melt Processing of Metal Matrix Composites
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EVALUATION OF VARIOUS INTERMETALLIC MATRIX - CERAMIC PARTICLE SYSTEMS FOR MELT PROCESSING OF METAL MATRIX COMPOSITES S. Sen, B. K. Dhindaw and D. M. Stefanescu Solidification Laboratory, Metallurgical and Materials Engineering, The University of Alabama, Tuscaloosa, Al 35487
ABSTRACT The possibility of incorporating SiC or TiC particulate reinforcements in a Ni 3 Al matrix through the melt processing route was examined. Interface bonding and thermal stability of SiC and surface treated SiC in Ni 3 Al has been investigated through sessile drop and DTA experiments. Feasibility of various processing techniques such as the mechanical mixing method and the vacuum infiltration method was also explored.
INTRODUCTION Aluminum based intermetallic compounds inherently possess low density, high melting temperature, superior high temperature strength, and oxidation resistance. Consequently they are potential materials for high temperature structural and propulsion applications. The intergranular brittleness found in the majority of the polycrystalline aluminides has to a certain extent been overcome by micro and macro alloying, and grain refinement [1,2]. A typical example is the Ni 3 Al system. Addition of 0.08 wt.% B to an alloy of Ni - 24 at. % Al yielded tensile elongation of up to 50% [3]. Hence it can be envisioned that introduction of ceramic reinforcements in such intermetallic systems would produce a composite with lower density, improved tensile strength, and stiffness. In this respect intermetallic matrix strengthened with fibrous or particulate reinforcements has recently been an area of considerable interest. The majority of the intermetallic matrix composite systems that have been investigated to date were fabricated by conventional powder metallurgy routes involving mechanical alloying, sintering, HIPing, and extrusion[4]. Limited efforts have also been directed towards production of intermetallic mairix composites by the pressure casting route [5]. While developing a melting and casting route for such composites, one has to consider the physico-chemical characteristics of the particles in relation to the matrix for evaluating the processing feasibility, i.e., the ease with which the reinforcements can be incorporated in the liquid metal, their subsequent distribution in the matrix and the reinforcement - matrix bonding. The ease of incorporation and bonding is both related to the wettability and the extent of reaction taking place between the matrix material and the reinforcement. Wettability is quantitatively described by the contact angle between the molten metal and the reinforcements [6]. A reaction zone between the matrix and the reinforcement is desirable to a certain extent to ensure superior bonding between Mat. Res. Soc. Symp. Proc. Vol. 273. ©1992 Materials Research Society
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the two. However, excessive chemical reaction between the reinforcements and the matrix may result in detrimental effects on the mechanical properties of the composite. Previous works have reported the characteristics of t
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