Iron and nickel Aluminide composites

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Abstract
Iron and nickel aluminide intermetallics are not only oxidation and corrosion resistant, but also thermodynamically compatible with a wide range of ceramics. This makes them suitable as the matrix for a wide range of composite systems. Among the composites evaluated to date are combinations of FeAl or Ni3Al with WC, TiC, SiC, TiB2, and Al2O3, with ceramic volume fractions ranging from (5 to 90%. A variety of processing techniques has been employed, but conventional liquid phase sintering and pressureless melt infiltration appear to be the most successful ones. Recently, a novel one‐step melt infiltration procedure has been developed to fabricate composites with ceramic volume fractions approaching 90%. Room temperature flexure strengths as high as 1.8 GPa have been obtained. Both FeAl and Ni3Al composites exhibit fracture toughnesses similar to those of WC/Co. It is found that sufficiently thin (< 2 μm) ligaments of FeAl tend to fracture in a ductile manner. The absence of cleavage fracture in these thin ligaments is due to the unavailability of sufficiently long dislocation pile‐ups for nucleating cleavage cracks. In addition to the mechanical properties of FeAl and Ni3Al composites, other properties of interest such as wear and corrosion resistance are briefly discussed. The properties of FeAl and Ni3Al composites are seen to complement each other and may be of interest in those applications where WC/Co composites Have limitations.