NASA Logo

NTRS

NTRS - NASA Technical Reports Server

Back to Results
Dynamic Instability of Solidification Fronts and Formation of Transverse Layered StructuresA plane front of crystallization in a unidirectional process of solidification of a binary melt or a solution is shown to be unstable with respect to virtual perturbations of the front velocity within some region of physical and operating parameters. This dynamic instability has nothing in common with morphological instability of the front also possible under certain conditions. It gives rise to the origination of a self-oscillating regime of solidification. The oscillations of the front velocity are accompanied by oscillations of other relevant variables, such as the melt concentration and temperature at the front. What is most important is that this provides for a natural explanation of phenomena of the formation of ordered striations commonly observed when producing alloys and withdrawing crystals. A theory of nonlinear instability of the solidification front is developed which also allows for properties of both self-oscillating regimes of solidification and transverse layered structures it allows to be described in an explicit form, without introducing any additional hypotheses and empirical parameters. Apart from other things, the properties are strongly dependent on convective transport originated in consequence of a difference between the densities of the liquid melt and solid alloy. The theory results in a remarkably good agreement with experimental evidence on crystal withdrawal obtained in normal gravity and under space flight conditions. The problem of interplay between modes of the dynamic and morphological types of instability is also discussed. There are parametric regions in which either only one of these types occurs or both of them arise simultaneously.
Document ID
20020014839
Acquisition Source
Ames Research Center
Document Type
Conference Paper
Authors
Buyevich, Yu A.
(National Academy of Sciences - National Research Council Moffett Field, CA United States)
Mansurov, Valery V.
(Urals A. M. Gorky State Univ. Sverdlovsk, USSR)
Webbon, Bruce W.
Date Acquired
August 20, 2013
Publication Date
January 1, 1995
Subject Category
Solid-State Physics
Meeting Information
Meeting: 1995 National Heat Transfer Conference
Location: Portland, OR
Country: United States
Start Date: August 5, 1995
End Date: August 9, 1995
Funding Number(s)
PROJECT: RTOP 199-61-62
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

Available Downloads

There are no available downloads for this record.
No Preview Available