Formation of bands of ultrafine beryllium particles during rapid solidification of Al-Be alloys: Modeling and direct observations

Journal Article · Fri Apr 01 04:00:00 EST 1994 · Acta Metallurgica et Materialia; (United States)

DOI:https://doi.org/10.1016/0956-7151(94)90124-4· OSTI ID:5121663

Elmer, J W; Tanner, L E; Smith, P M; Wall, M A ^[1]; Aziz, M J ^[2]

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1. Lawrence Livermore National Lab., CA (United States)
2. Harvard Univ., Cambridge, MA (United States). Div. of Applied Sciences

Rapid solidification of dilute hyper-eutectic and monotectic alloys sometimes produces a dispersion of ultrafine randomly-oriented particles that lie in arrays parallel to the advancing solidification front. The authors characterize this effect in Al-Be where Be-rich particles with diameters on the order of 10 nm form in arrays spaced approximately 25 nm apart, and they present a model of macroscopically steady state but microscopically oscillatory motion of the solidification front to explain this unusual microstructure. The proposed mechanism involves; (i) the build-up of rejected solute in a diffusional boundary layer which slows down the growing crystal matrix, (2) the boundary layer composition entering a metastable liquid miscibility gap, (3) homogeneous nucleation of solute rich liquid droplets in the boundary layer, and crystallization of these droplets, and (4) growth of the matrix past the droplets and its reformation into a planar interface. The size of the Be-rich particles is limited by the beryllium supersaturation in the diffusional boundary layer. A numerical model was developed to investigate this solidification mechanism, and the results of the model are in good agreement with experimental observations of rapidly solidified Al-5 at.% Be.

• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 5121663
• Journal Information: Acta Metallurgica et Materialia; (United States), Journal Name: Acta Metallurgica et Materialia; (United States) Vol. 42:4; ISSN 0956-7151; ISSN AMATEB
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360102* -- Metals & Alloys-- Structure & Phase Studies
ALLOY SYSTEMS
ALLOYS
ALUMINIUM ALLOYS
ALUMINIUM BASE ALLOYS
BERYLLIUM ALLOYS
BINARY ALLOY SYSTEMS
DATA
ELECTRON MICROSCOPY
EXPERIMENTAL DATA
INFORMATION
MATHEMATICAL MODELS
MICROSCOPY
MICROSTRUCTURE
NUMERICAL DATA
THEORETICAL DATA
TRANSMISSION ELECTRON MICROSCOPY