Thermal stability of rare-earth oxides in Ti when annealed above the. cap alpha. /. beta. transus

Journal Article · Mon Jun 01 04:00:00 EDT 1987 · Scr. Metall.; (United States)

DOI:https://doi.org/10.1016/0036-9748(87)90337-1· OSTI ID:5830899

Lofvander, J P.A.; Court, S A; Kirchheim, R; Fraser, H L

In most cases the thermal stability has been demonstrated by restricting annealing to the temperature range corresponding to ..cap alpha..-Ti. Since many Ti alloys make use of processing and heat-treatments when the matrix is ..beta..-Ti, it is of interest to determine the stability of these rare-earth oxides when annealed above the ..cap alpha beta.. transus. The paper describes the results of annealing a Ti-0.7Er alloy which has been rapidly solidified and heat-treated subsequently so that it contains a refined dispersion of Er/sub 2/O/sub 3/. The alloy composition was chosen so that a slight excess of Er remains in the matrix following oxide formation. In this way, since Er is not known to be either an ..cap alpha..- or ..beta..-Ti stabilizer, it has been assumed that the transus temperature is that of pure Ti, and the presence of a two-phase (..cap alpha..+..beta..) field, such as would occur with an excess of oxygen is avoided. It has been shown that when a refined dispersion of rare earth oxides is annealed above the ..cap alpha beta.. transus the average particle diameter coarsens from approx. =50nm to approx. = 0.5..mu..m. It is concluded that Ostwald ripening is effected mainly by enhanced diffusion along the migrating interphase boundaries during the transformation of ..cap alpha..- to ..beta..-Ti.

• Research Organization: Dept. of Materials Science and Engineering, Univ. of Illinois, 1304 W. Green Street, Urbana, IL 61801
• OSTI ID: 5830899
• Journal Information: Scr. Metall.; (United States), Journal Name: Scr. Metall.; (United States) Journal Issue: 6 Vol. 21:6; ISSN SCRMB
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360101* -- Metals & Alloys-- Preparation & Fabrication
360102 -- Metals & Alloys-- Structure & Phase Studies
360202 -- Ceramics
Cermets
& Refractories-- Structure & Phase Studies
360204 -- Ceramics
Cermets
& Refractories-- Physical Properties
ALLOYS
ANNEALING
CHEMICAL COMPOSITION
CRYSTAL STRUCTURE
CRYSTAL-PHASE TRANSFORMATIONS
DIFFUSION
GRAIN BOUNDARIES
HEAT TREATMENTS
HIGH TEMPERATURE
METALLURGICAL EFFECTS
MICROSTRUCTURE
PHASE TRANSFORMATIONS
PHYSICAL PROPERTIES
RARE EARTH COMPOUNDS
SOLIDIFICATION
STABILITY
THERMAL DIFFUSION
THERMODYNAMIC PROPERTIES
TITANIUM ALLOYS