Influence of crystallography upon critical nucleus shapes and kinetics of homogeneous f. c. c. -f. c. c. nucleation-V. The origin of GP zones in Al-Ag and Al-Cu alloys

Journal Article · Mon Oct 01 04:00:00 EDT 1984 · Acta Metall.; (United States)

DOI:https://doi.org/10.1016/0001-6160(84)90244-X· OSTI ID:6060266

Le Goues, F K; Aaronson, H I; Lee, Y W; Wright, R N

GP zone formation in aluminum-base alloys has been proposed, by previous investigators, to take place by spinodal decomposition or by homogeneous nucleation and growth. The possibilities of these two mechanisms are examined here for two alloy systems, Al-Ag and Al-Cu, representing two extreme cases, a narrow and a (potentially) very wide miscibility gap, respectively, resulting in low and high interphase boundary energies. The coherent spinodal and the temperature-composition curve corresponding to abundant homogeneous f.c.c.-f.c.c. nucleation were calculated for both systems. In Al-Ag alloys, the nucleation barrier is so low that negligible undercooling is needed to achieve abundant nucleation. Hence cooling into the spinodal region with ordinary quenching rates is virtually impossible. In Al-Cu, however, the inverse situation is present and GP zone formation by (or aided by) spinodal decomposition should be feasible if the diffusivity remains sufficiently high in the spinodal region. Detailed evaluation of the latter proposal is prevented, however, by the incompleteness of thermodynamic information on f.c.c. Al-Cu alloys.

• Research Organization: Department of Metallurgical Engineering and Materials Science, Carnegie-Mellon University, Pittsburgh, PA
• OSTI ID: 6060266
• Journal Information: Acta Metall.; (United States), Journal Name: Acta Metall.; (United States) Vol. 32:10; ISSN AMETA
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360102* -- Metals & Alloys-- Structure & Phase Studies
ALLOY SYSTEMS
ALLOYS
ALUMINIUM ALLOYS
BINARY ALLOY SYSTEMS
COPPER ALLOYS
CRYSTAL GROWTH
CRYSTAL LATTICES
CRYSTAL STRUCTURE
CRYSTALLOGRAPHY
CUBIC LATTICES
DIFFUSION
FCC LATTICES
GUINIER-PRESTON ZONES
KINETICS
MORPHOLOGY
NUCLEATION
QUENCHING
REACTION KINETICS
SILVER ALLOYS
TEMPERATURE DEPENDENCE
TEMPERATURE EFFECTS
ZONES