Project Title:

Chemical Vapor Deposition of Ti-Al Foils

04.03-7648
Chemical Vapor Deposition of Ti-Al Foils
MSNW, Inc.
PO Box 865
San Marcos, CA 92069
George H. Reynolds  (619-744-7648)
LaRC -- NAS1-18615

Abstract:

	 Effective use of intermetallic compounds in composite and honeycomb structures
will require high-strength, high-quality foils for starting materials. Direct fabrication
of titanium-aluminum (TiAl) foils by chemical-vapor deposition onto sacrificial tape
substrates was studied as a novel means to produced the desired starting materials.

	Two techniques, high-temperature, chemical-vapor deposition from mixed halide vapors
and low-temperature, chemical-vapor deposition from mixed organometallic gases, were
explored. In Phase I, a cold-wall, chemical-vapor-deposition apparatus was constructed,
and TiAl alloy films ranging in composition from essentially pure Ti to approximately
TiAl3 and from 5-40 microns in thickness were successfully deposited on molybdenum
substrates. As characterized by optical and scanning electron metallographic examinations,
X-ray diffraction, microchemical analysis, and micro-hardness testing, the films
were found to be chemically homogeneous and generally dense although some films contained
isolated porosity and exhibited microcracks. Deposition was in agreement with the
predictions of a preliminary chemical process model constructed to describe the chemical-vapor
synthesis of TiAl films from halide precursors.

Potential Commercial Application:

Potential Commercial Application: The product foils could be useful in preparation
of thin-gage tapes and complex, honeycomb structures of difficult-to-work materials.
Other applications might include intermetallic-matrix composites for hypersonic vehicle
structural elements, advanced propulsion system components, and space structures.