Transformation processes and microstructural instability in a beta titanium alloy

Thesis/Dissertation · Fri Jan 01 04:00:00 EST 1988

OSTI ID:5217248

Chun, C H

The transformation processes and microstructural instability were examined in a {beta} titanium alloy, Ti-15V-3Cr-3Al-3Sn, over the temperature range 250 to 500{degree}C, for times up to 1000 hours. The role of the {omega} phase as a precursor to the {alpha} phase was examined in Ti-15-3 alloy aged at 250 or 275{degree}C where the {omega} and {alpha} phase coexist. The {omega} particles provide preferential nucleation sites for {alpha}phase, thereby promoting a uniform dispersion of fine {alpha} precipitates. The effect of cold work prior to aging on the aging kinetics was examined in Ti-15-3 alloy cold rolled up to 60% and aged at temperatures in the range 200 to 350{degree}C. Cold deformation prior to aging accelerates the formation of {omega} phase when it is the sole aging product. However, when {omega} and {alpha} coexist, cold deformation suppresses the formation of the {omega} phase and favors the direct precipitation of the {alpha} phase for the aging condition employed. The kinetics of {alpha} precipitation in the Ti-15-3 alloy aged below 400{degree}C were also examined. The activation energy for the formation of {alpha} phase decreases with the fraction transformed. This result is consistent with the enhancement of heterogeneous nucleation of the {alpha} phase by an increasing volume fraction of {omega} particles as the fraction transformed increases.

• Research Organization: Washington Univ., Seattle, WA (USA)
• OSTI ID: 5217248
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360102* -- Metals & Alloys-- Structure & Phase Studies
AGING
ALLOYS
ALUMINIUM ALLOYS
CHROMIUM ALLOYS
CRYSTAL STRUCTURE
MICROSTRUCTURE
PHASE STUDIES
TEMPERATURE EFFECTS
TIN ALLOYS
TITANIUM ALLOYS
TITANIUM BASE ALLOYS
VANADIUM ALLOYS