Precipitation behavior of. delta. prime in a binary Al-Li alloy

Journal Article · Sun Sep 01 04:00:00 EDT 1991 · Scripta Metallurgica; (United States)

OSTI ID:5703575

Mahalingam, K; Mahadev, V; Liedl, G L ^[1]; Sanders, Jr, T H ^[2]

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1. Purdue Univ., Lafayette, IN (United States). School of Materials Engineering
2. Georgia Inst. of Tech., Atlanta, GA (United States). School of Material Engineering

The precipitation of {delta}{prime} in binary Al-Li alloys has been a subject of many investigations due to its role as the strengthening phase. The results of these investigations and the current level of understanding of the precipitation process in binary Al-Li alloy has been reviewed. Early studies have identified that the {delta}{prime} is ordered and has L1{sub 2} structure, and that the misfit strain associated with its formation is very small (0.18%). These studies show that the precipitate particles are coherent with the matrix and spherical in shape. Further, the interfacial energy of the precipitate-matrix interface is estimated to be 0.015 J/m{sup 2}. A number of investigations by TEM have shown that the aging kinetics follows the Ostwald coarsening kinetics with the coarsening rate constant increasing with an increase in either the aging temperature or the Li content of the alloy. The activation energy for the coarsening process is estimated to be 135-140 kJ/mol in the temperature range 450-500K. Since conventional TEM methods have problems resolving particles in the initial stage of the precipitation, these studies have been conducted for relatively long aging times when the {delta}{prime} particle sizes may be measured accurately. Consequently, very little quantitative information is available for these studies concerning the aging kinetics during the initial stages of aging. The results from these studies when extrapolated to lower aging times indicate that the Ostwald ripening kinetics is obeyed very early in the aging process. Recent studies by SAXS lend support to this view. This paper provides information on the early aging kinetics using X-ray diffraction particle size broadening measurements. comparison with the results obtained in TEM studies are made through the use of samples known to fit the coarsening regime.

• OSTI ID: 5703575
• Journal Information: Scripta Metallurgica; (United States), Journal Name: Scripta Metallurgica; (United States) Vol. 25:9; ISSN 0036-9748; ISSN SCRMB
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360102* -- Metals & Alloys-- Structure & Phase Studies
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400101 -- Activation
Nuclear Reaction
Radiometric & Radiochemical Procedures
AGING
ALLOY SYSTEMS
ALLOYS
ALUMINIUM ALLOYS
BINARY ALLOY SYSTEMS
CHEMICAL REACTION KINETICS
COHERENT SCATTERING
DIFFRACTION
ELECTRON MICROSCOPY
KINETICS
LITHIUM ALLOYS
MICROSCOPY
PARTICLE SIZE
PHASE STUDIES
PRECIPITATION
REACTION KINETICS
SCATTERING
SEPARATION PROCESSES
SIZE
TRANSMISSION ELECTRON MICROSCOPY
X-RAY DIFFRACTION