Oxidation of titanium aluminide and its XD composite. Final report 1988-1989

Technical Report · Thu Dec 20 00:00:00 EST 1990

OSTI ID:6359230

Lee, E U; Kircher, T; Waldman, J

Martin Marietta Lab. recently developed a unique technology, whereby reinforcement dispersoids can be introduced exothermically into a metal matrix. This special alloying approach, known as Exothermic Dispersion (XD) processing, produces a metal matrix composite with a fine dispersion of a high-modulus, high-strength compound, such as titanium boride, in titanium aluminide. This study was undertaken to characterize the oxidation behavior of a Ti-45 at % Al alloy and its XD composite with TiB2 reinforcement particles. These materials were found to oxidize in air at temperatures ranging from 400 to 1500 C. Oxidation was evidenced by surface discoloration, formation of an oxide scale and an interfacial zone, internal oxide precipitation, internal cracking, and weight gain. The oxide scale consisted of two layers; an inner TiO2 and Al2O3 mixture; and an outer TiO2 and Al2TiO5 mixture. A narrow zone along the oxide scale/base metal interface was depleted in Al, but enriched with O. In the Ti-45 at % Al alloy, an Al-rich oxide, presumably Al2O3, was precipitated in the TiAl plate and a Ti-rich oxide, presumably TiO2, was precipitated in the Ti3Al plate. In the XD composite, an Al-rich oxide was precipitated along the lamellar structure colony boundary, and a Ti-rich oxide was precipitated in the interior of the colony. During oxidation, internal cracking occurred along the boundary and in the interior of the TiAl and Ti3Al plates. In addition, voids were formed at the lamellar structure boundary of the XD composite. The specimen gained weight with increasing oxidation temperature. Activation energies for oxidation were determined to be 63 kcal/mol for the Ti-45 at % Al alloy, and 67 kcal/mol for the XD

• Research Organization: Naval Air Development Center, Warminster, PA (United States). Air Vehicle and Crew Systems Technology Dept.
• OSTI ID: 6359230
• Report Number(s): AD-A-240401/0/XAB; NADC-90122-60
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM ALLOYS
OXIDATION
TITANIUM BASE ALLOYS
TITANIUM BORIDES
ACTIVATION ENERGY
AIR
ALLOYS
ALUMINIUM OXIDES
COMPOSITE MATERIALS
CORROSION
CRACKS
DISPERSIONS
INTERFACES
INTERMETALLIC COMPOUNDS
LAYERS
MATRIX MATERIALS
METALS
OXIDES
PRECIPITATION
REINFORCED MATERIALS
SURFACES
TITANIUM OXIDES
WEIGHT
ALUMINIUM COMPOUNDS
BORIDES
BORON COMPOUNDS
CHALCOGENIDES
CHEMICAL REACTIONS
ELEMENTS
ENERGY
FLUIDS
GASES
MATERIALS
OXYGEN COMPOUNDS
SEPARATION PROCESSES
TITANIUM ALLOYS
TITANIUM COMPOUNDS
TRANSITION ELEMENT COMPOUNDS
360105* - Metals & Alloys- Corrosion & Erosion
360604 - Materials- Corrosion
Erosion
& Degradation