A structural study of oxidation in a zirconia-toughened alumina fiber-reinforced Fe3Al composite

S. Nourbakhsh, O. Sahin, W. H. Rhee, H. Margolin

Research output: Contribution to journalArticle

Abstract

A zirconia-toughened alumina fiber-reinforced Fe3Al-based intermetallic composite was fabricated by pressure casting. The chemical stability of the composite at 1100 °C in vacuum and air was studied by optical, scanning, and transmission electron microscopy. Fiber/molten metal interaction during pressure casting resulted in the rejection of ZrO2 from the fiber into the molten metal. The fiber/matrix interface in the cast composite was in some areas covered with thin ZrC and Fe2AlZr layers. Vacuum annealing resulted in the dissolution of Fe2AlZr and precipitation of ZrC and (Ti, Nb)C particles within the matrix. The density of carbides was very low. Air annealing led to the oxidation of ZrC to ZrO2, Fe2AlZr to a mixture of A12O3 + ZrO2, and preferential growth of α-Al2O3 over the ZrO2. Depletion of Al from the matrix as a result of oxidation gave way to the precipitation of (a) coarse (Fe, Al)2(Nb, Al) particles and (b) fine cuboidal-shaped particles within the matrix during slow cooling from the oxidizing temperature. Oxidation of the matrix ended with the conversion of Fe(Al, Cr) into (Fe, Al, Cr)2O3. The Fe2O3 was observed to wet the grain boundaries of the A12O3 fiber, which resulted in the disintegration of the fiber. Zr-containing plate-like precipitates with a {10-14} habit plane were occasionally observed in Fe2O3. Diffusion of oxygen through the fiber and/or the fiber/matrix interface is believed to be responsible for the rapid oxidation of the composite.

Original languageEnglish (US)
Pages (from-to)435-443
Number of pages9
JournalMetallurgical Transactions A
Volume24
Issue number2
DOIs
StatePublished - Feb 1993

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Mechanics of Materials
  • Metals and Alloys

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