A study of fiber coating in Al sub 2 O sub 3 fiber-reinforced NiAlFe matrix composites

The effectiveness of using oxide coating to modify the interface in the Al sub 2 O sub 3 fiber-reinforced NiAlFe matrix composites was studied. ZrO sub 2 , Y sub 2 O sub 3 -stabilized ZrO sub 2 , and yttrium aluminum garnet (i.e. Y sub 3 Al sub 5 O sub 12 ) coatings were applied onto the Al sub 2 O sub 3 fibers by the sol-gel process, and the composites with various coated fibers were consolidated by using a tape-casting/hot isostatic pressing technique. The interface morphology and integrity of the coating layer, as well as the chemical compatibility and thermal stability with the matrix were characterized by scanning electron microscopy, energy dispersive spectroscopy, and scanning Auger electron spectroscopy. Transverse tensile and flexural strengths of the uncoated and coated composites were determined at 980 deg C and room temperature, respectively, to evaluate the effect of coating on their mechanical properties and failure behavior. Critical issues on tailoring a functional interface using fiber coatings to control interdiffusion between the fiber and matrix, and improving the mechanical behavior of the Al sub 2 O sub 3 /NiAlFe composite were discussed.