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

Journal Article · Wed Jun 01 00:00:00 EDT 1994 · Metallurgical Transactions, A (Physical Metallurgy and Materials Science); (United States)

DOI:https://doi.org/10.1007/BF02652303· OSTI ID:7174391

Nourbakhsh, S; Sahin, O; Margolin, H ^[1]

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1. Polytechnic Univ., Brooklyn, NY (United States). Dept. of Materials Science and Engineering

A composite of NiAl reinforced with continuous zirconia-toughened alumina (PRD-166) fibers was fabricated by pressure casting. The chemical stability of the composite at 1,100 C in vacuum and air was investigated by optical and transmission electron microscopy and energy-dispersive spectroscopy (EDS). Exposure of the fiber to the molten metal caused ZrO[sub 2] particles in the fiber to move to the surface, thus permitting dissolution of ZrO[sub 2] into the molten metal. The dissolved Zr reacted with Al[sub 2]O[sub 3] Of the fiber and formed ZrO[sub 2] particles in some regions at the fiber/matrix interface. Vacuum annealing did not result in any noticeable change in the microstructure. Air annealing led to the precipitation of ZrO[sub 2] within the matrix near the fiber/matrix interface. A thin layer of Al[sub 2]O[sub 3] was observed to envelop the ZrO[sub 2] particles and cover the fiber. During air annealing, Al oxidized preferentially, thereby continually reducing the Al content of the [beta]-NiAl. This caused a progressive change in the microstructure of the matrix from [beta]-NiAl to premartensitic microstructure, to martensitic structure, followed by nucleation and growth of Ni[sub 3]Al, to the development of a two-phase microstructure consisting of Ni[sub 3]Al cuboids dispersed in a disordered [alpha]-Ni(Al) and, subsequently, the formation of single-phase [alpha]-Ni(Al). The orientation relationship between Ni[sub 3]Al and NiAl was [l brace]110[r brace][sub NiAl]//[l brace]111[r brace][sub Ni[sub 3]Al], <1[bar 1]1>[sub NiAl]//<0[bar 1]1>[sub Ni[sub 3]Al]. Internal oxidation of [alpha]-Ni(Al) led to precipitation of A1203 particles which subsequently reacted with Ni, in the presence of O, to form NiO[center dot]Al[sub 2]O[sub 3] spinel. The Ni was oxidized to form [beta]-NiO. Titanium containing, platelike precipitates with a [l brace]111[r brace] habit plane were occasionally observed in NiO. Some larger NiTiO[sub 3] particles were also formed within NiO.

• OSTI ID: 7174391
• Journal Information: Metallurgical Transactions, A (Physical Metallurgy and Materials Science); (United States), Vol. 25:6; ISSN 0360-2133
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM ALLOYS
MICROSTRUCTURE
OXIDATION
ALUMINIUM OXIDES
COMPOSITE MATERIALS
NICKEL BASE ALLOYS
ZIRCONIUM OXIDES
EXPERIMENTAL DATA
NICKEL OXIDES
TITANIUM OXIDES
ALLOYS
ALUMINIUM COMPOUNDS
CHALCOGENIDES
CHEMICAL REACTIONS
DATA
INFORMATION
MATERIALS
NICKEL ALLOYS
NICKEL COMPOUNDS
NUMERICAL DATA
OXIDES
OXYGEN COMPOUNDS
TITANIUM COMPOUNDS
TRANSITION ELEMENT COMPOUNDS
ZIRCONIUM COMPOUNDS
360604* - Materials- Corrosion
Erosion
&amp; Degradation
360602 - Other Materials- Structure &amp; Phase Studies