Journal ArticleDOI
Modification in the aluminum silicon system
TLDR
In this paper, it was shown that the structural modification in furnace cooled ingots, as in directionally grown samples, is primarily caused by modified growth of silicon, and the mechanism(s) for such modification are briefly discussed.Abstract:
Alloys in the range 0 to 24 wt pct Si have been examined by careful thermal analysis, macroand microscopical study with modification by a mixed alkali fluoride flux, and by separate additions of sodium, potassium, lithium, and strontium. Sodium and strontium exert similar effects and potassium and lithium differing and minor effects; with a mixed alkali flux the influence of sodium is dominant. The normal and modified eutectic arrests in the presence of primary aluminum both show comparable supercoolings and recalescence behavior relative to the horizontal growth temperatures, but this is not observed in hypereutectic alloys containing primary silicon. Both normal and modified eutectics grow radially inward from crucible walls, but the details of the growth fronts are very different: there is no nucleation from the bulk liquid in modified alloys and it is uncertain if this occurs in normal alloys. It is concluded that the structural modification in furnace cooled ingots, as in directionally grown samples, is primarily caused by modified growth of silicon. The mechanism(s) for such modification are briefly discussed.read more
Citations
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The mechanism of silicon modification in aluminum-silicon alloys: Impurity induced twinning
Shu Zu Lu,A. Hellawell +1 more
TL;DR: In this paper, the atomic positions which attend the formation of growth twins on {111} planes are investigated and it is shown that adsorbed impurity atoms of suitable size, on the solid-liquid interface, could be responsible for changing the stacking sequence, so promoting impurity induced twinning.
Journal ArticleDOI
Modification of eutectic silicon in Al-Si alloys
TL;DR: In this paper, a review of various aspects of modification, including mechanism, interaction of defects and non-destructive assessment by thermal analysis is presented, where the deviation from the standard curve in thermal analysis helps in assessing the level of refinement of the Si structure.
Journal ArticleDOI
Eutectic nucleation and growth in hypoeutectic Al-Si alloys at different strontium levels
TL;DR: In this article, the effects of different levels of strontium on nucleation and growth of the eutectic in a commercial hypoeutective Al-Si foundry alloy have been investigated by optical microscopy and electron backscattering diffraction (EBSD) mapping by scanning electron microscopy (SEM).
Journal ArticleDOI
The aluminum–silicon eutectic reaction: mechanisms and crystallography
M.M. Makhlouf,H.V. Guthy +1 more
TL;DR: The evolution of the contemporary theory for the formation and chemical modification of the aluminum-silicon eutectic is reviewed in this article, where the work of Hellawell et al., which laid the foundation for the present day understanding of this technologically important reaction, is critically examined and certain inconsistencies are shown to exist between the contemporary theories and more current concepts.
Journal ArticleDOI
Refinement of eutectic silicon phase of aluminum A356 alloy using high-intensity ultrasonic vibration
TL;DR: In this paper, the eutectic silicon in A356 alloy can be refined and modified using either chemical, quench, or superheating modification using high-intensity ultrasonic vibration.
References
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Journal ArticleDOI
Transformation pseudoelasticity and deformation behavior in a Ti-50.6at%Ni alloy
Journal ArticleDOI
Propagation Mechanism of Germanium Dendrites
TL;DR: The role of the twin planes in the rapid dendritic propagation of germanium crystals is examined on the basis of corner nucleation in this article, and it is shown that at least two twin planes must be present for continued easy propagation in directions.
Journal ArticleDOI
A theory of branching limited growth of irregular eutectics
D.J. Fisher,Wilfried Kurz +1 more
TL;DR: In this paper, a first attempt is made to incorporate the various disparate facts concerning their growth into a coherent growth model in particular, the usual minimum undercooling criterion is abandoned in favour of one based on the morphological instability and branching of the phases Despite numerous approximations, the correct order of magnitude of spacing and under cooling is predicted, as is the effect of the imposed temperature gradient.
Journal ArticleDOI
Modification of Al-Si eutectic alloys with Na
S. C. Flood,J. D. Hunt +1 more
TL;DR: In this paper, it is suggested that the change in Si growth morphology may be the result of non-faceted Si growth at high velocities or in the presence of Na.
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The mechanism of silicon modification in aluminum-silicon alloys: Impurity induced twinning
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