Metastable phases in the Ti{sub 3}Al-Nb system

Journal Article · Tue Aug 01 04:00:00 EDT 1995 · High Temperature and Materials Science

OSTI ID:218629

Levin, L; Ginzburg, A; Katsman, A ^[1]

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1. Technion, Haifa (Israel). Dept. of Materials Engineering

A ternary Ti-Al-Nb alloy containing 24 at% Al and 11 at% Nb was studied after {beta}-solution vacuum-heat treatment followed by cooling to room temperature at different rates, namely, furnace cooling, water quenching (WQ), oil quenching (OQ), and annealing at different temperatures. After these treatments, microstructure and phase composition were examined by optical and scanning electron microscopy, X-ray diffractometry, and DTA. The obtained phases were as follows: (1) The stable phases: {alpha}{sub 2}-(Ti,Nb){sub 3}Al and {beta}-Ti(Al,Nb); (2) The metastable phases: O-Ti{sub 2}AlNb, {sigma}-(Ti,Nb){sub 2}Al, and {omega}-Ti{sub 4}Al{sub 3}Nb; their stability decreases in the following sequences: O, {sigma}, {omega}. The {omega}-phase (hP3) was found only in the WQ specimen; the {sigma}-phase (tP30) does exist in the WQ and OQ specimens. Both phases disappear during aging (even at room temperature). The O-phase (oC16) was identified in the as-received state and in the quenched specimens, as well as in those annealed at 800 C. It disappears during high temperature (900 C) annealing.

• OSTI ID: 218629
• Report Number(s): CONF-940468--
• Journal Information: High Temperature and Materials Science, Journal Name: High Temperature and Materials Science Journal Issue: 1-3 Vol. 34; ISSN 1080-1278; ISSN HTMSFP
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM ALLOYS
DIFFERENTIAL THERMAL ANALYSIS
HEAT TREATMENTS
INTERMETALLIC COMPOUNDS
MICROSTRUCTURE
NIOBIUM ALLOYS
PHASE STUDIES
TITANIUM BASE ALLOYS