scholarly journals Rod eutectic growth in bulk undercooled melts

2021 ◽  
Author(s):  
Junfeng Xu ◽  
Tao Zhang ◽  
Peter Galenko
Keyword(s):  
Bessel Function ◽  
Model Calculation ◽  
Analytical Model ◽  
Growth Velocity ◽  
Growth Models ◽  
High Growth ◽  
Eutectic Growth ◽  
Lamellar Eutectic ◽  
Undercooled Melt ◽  
Undercooled Melts

This article proposes an analytical model to understand the rod-growth of eutectic in the bulk undercooled melt. Based on the previous derivations of the lamellar eutectic growth models, relaxing the assumptions of small Peclet numbers, the model is derived by considering melt kinetic and thermal undercoolings. The intent of this model is to predict the transitions in eutectic pattern for conditions of the low and high growth velocity. In addition to investigation of the transition between lamellar and rod eutectic pattern, mathematical simplifications of solving Bessel function are presented as well, which is the most important priority to model calculation.

Nucleation and Dendritic Growth in Undercooled Melts

1995 ◽  
Vol 398 ◽  
Author(s):  
Dieter M. Herlach
Keyword(s):  
Crystal Growth ◽  
Growth Velocity ◽  
Dendritic Growth ◽  
Magnetic Ordering ◽  
Containerless Processing ◽  
Magnetic Alloys ◽  
Dendrite Growth Velocity ◽  
Direct Measurements ◽  
Undercooled Melt ◽  
Undercooled Melts

ABSTRACTTechniques of containerless processing are applied to undercool and solidify metals and alloys. These techniques allow direct measurements of both the undercooling and the crystal growth velocity. Experimental results are presented for studies of nucleation of metastable crystalline phases and quasicrystals. Measurements of the dendrite growth velocity as a function of undercooling are exemplified for dilute Ni-based alloys and intermetallics. The results are analysed within current theories of rapid crystal growth. Their consequences on the formation of grain refined microstructures are highlighted. In addition, recent experiments on the undercooling of magnetic alloys are discussed revealing the existence of long-range magnetic ordering in an undercooled melt.

The Contribution of Diffusion Coefficient to the Eutectic Instability and Amorphous Phase Formation

2010 ◽  
Vol 654-656 ◽  
pp. 1355-1358 ◽  
Author(s):  
Nan Wang ◽  
Xiao Wang ◽  
Wen Jing Yao
Keyword(s):  
Diffusion Coefficient ◽  
Amorphous Phase ◽  
Growth Velocity ◽  
Diffusion Length ◽  
Eutectic Growth ◽  
Maximum Growth ◽  
Interface Growth ◽  
Maximum Undercooling ◽  
Experimental Values ◽  
Amorphous Phase Formation

The diffusion coefficient D decides the diffusion length of solute boundary and plays a key role in the microstructure selection. This paper examines quantitatively the contribution of diffusion coefficient to the eutectic instability and amorphorization ability. The maximum growth velocity Vmax and the maximum undercooling Tmax as functions of activation energy Q in strong liquids are deduced theoretically based on eutectic growth model by separating Q from D. It reveals that the larger the Q, the smaller the Tmax and Vmax, which shows the same tendency as experimental values in some Al-based alloys and glass formers. This indicates that it is the sluggish movement of atoms that makes the transition from eutectic to others structural morphologies, even to amorphous phase, occur at smaller interface growth velocity or undercooling, which is the main contribution of the diffusion coefficient to the amorphorization ability.

Technical Progress and Structural Change in Jean Fourastié’s Theory of Development

2020 ◽  
Vol 52 (1) ◽  
pp. 101-133
Author(s):  
Alain Alcouffe ◽  
David le Bris
Keyword(s):  
World War Ii ◽  
Technical Progress ◽  
Manufacturing Industry ◽  
Structural Changes ◽  
Growth Models ◽  
Social Scientist ◽  
High Growth ◽  
New Era ◽  
Statistical Series ◽  
High Level

The social scientist Jean Fourastié introduced his model of economic development in a book published in 1949. He based his analysis on a statistical series he had collected, which established two principles: technical progress is not uniformly distributed across industries (it is higher in manufacturing industry than in services) and human demand for both agricultural and manufactured goods does not grow continuously and may be saturated. These two principles allowed him to propose a model which attempted to predict the high growth observed after World War II (a period that he later called the Glorious Thirty) as well as the following rise of services, leading to a new era of stagnation at the turn of the millennium. His model emphasizes the role of technical progress while growth models focus on capital and labor. Fourastié’s work was initially reviewed by sociological and economic scholars interested in structural changes. As high-level advisor for various French governments and a bestselling author, Fourastié remained at the margin of the economic profession. However, an important legacy is the concept of cost disease developed by William Baumol, which is one implication of Fourastié’s more general model.

Monte-Carlo simulation of regular lamellar eutectic growth in binary systems

2002 ◽  
Vol 336 (1-2) ◽  
pp. 129-134
Author(s):  
Wei-Min Wang ◽  
J.-M. Liu ◽  
X.M. Pan ◽  
Zhiguo Liu
Keyword(s):  
Monte Carlo Simulation ◽  
Monte Carlo ◽  
Binary Systems ◽  
Eutectic Growth ◽  
Lamellar Eutectic

Broken lamellar eutectic growth; Structure of the silver-bismuth eutectic

1968 ◽  
Vol 3-4 ◽  
pp. 666-673 ◽  
Author(s):  
M.R. Taylor ◽  
R.S. Fidler ◽  
R.W. Smith
Keyword(s):  
Eutectic Growth ◽  
Lamellar Eutectic ◽  
Growth Structure

Modelling Eutectic Growth in Unmodified and Modified Near-Eutectic Al-Si Alloy

2013 ◽  
Vol 765 ◽  
pp. 160-164
Author(s):  
Niels Skat Tiedje ◽  
Jesper Henri Hattel ◽  
John A. Taylor ◽  
Mark A. Easton
Keyword(s):  
Numerical Model ◽  
Growth Velocity ◽  
Alloy Composition ◽  
Growth Parameters ◽  
Eutectic Growth ◽  
Nucleation And Growth ◽  
Cooling Conditions ◽  
Nucleation Model ◽  
Primary Aluminium ◽  
Modified Forms

A numerical model that describes solidification of primary aluminium grains and nucleation and growth of eutectic cells is used to analyse the solidification of an Al-12.5wt% Si alloy. Nucleation of eutectic cells is modelled using an Oldfield-type nucleation model where the number of nuclei in the melt is determined by the amount of active nuclei and the local undercooling from the surface to the centre of a plate casting. Eutectic grains are modelled as spheres growing between the dendrites. The growth velocity of the eutectic cells is a function of undercooling. Experimentally determined growth parameters from the literature that depend on the type of modification (unmodified, Na-modified or Sr-modified) are used to describe differences in growth of the alloys. Modelling results are compared with solidification experiments where an Al-12.5wt%Si alloy was cast in unmodified, Na modified and Sr modified forms. The model confirms experimental observations of how modification and alloy composition influence nucleation, growth and finally the size of eutectic cells in the alloys. Modelling results are used to explain how cooling conditions in the casting act together with the nuclei density in the liquid and the growth velocity of the eutectic cells to determine the size and distribution of eutectic cells in the solidified material.

Impact of Material Crystallization Characteristics on the Switching Behavior of the Phase Change Memory Cell

2006 ◽  
Vol 918 ◽  
Author(s):  
Thomas Gille ◽  
Ludovic Goux ◽  
Judit Lisoni ◽  
Kristin De Meyer ◽  
Dirk J. Wouters
Keyword(s):  
Phase Change ◽  
Growth Models ◽  
Horizontal Cell ◽  
Phase Change Memory ◽  
High Growth ◽  
Switching Behavior ◽  
Horizontal Line ◽  
The Impact ◽  
Change Memory ◽  
Vertical Cell

AbstractThe impact of material crystallization characteristics on the switching behavior of phase change memory cells has been investigated using finite element simulation. Both a conventional vertical cell and a horizontal line cell have been analyzed, using the widely used Ge2Sb2Te5 (GST) which is a nucleation dominated material for the vertical cell, and Ag5.5In6.5Sb59Te29 (AIST) which is a growth dominated material for the horizontal cell. Nucleation and growth models were implemented for both materials. Both RESET and SET program cycles were simulated. From these simulations, it was shown that the crystallization models gave realistic results for switching voltages, currents and switching times for the two different cell types. It is found that for GST, both nucleation (at lower voltages) and growth (at higher voltages) can play an important role in the crystallization. However, for AIST, crystal growth from non-amorphized crystal regions dominated over nucleation for all program conditions. The high growth rate of AIST moreover is shown to allow much shorter SET times in the line cell compared to that of GST in the vertical cell.

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