Onset of sidewise instability and cell–dendrite transition in directional solidification

2009 ◽  
Vol 57 (12) ◽  
pp. 3497-3508 ◽  
Author(s):  
J. Teng ◽  
S. Liu ◽  
R. Trivedi
Keyword(s):  
Directional Solidification ◽  
Cell Dendrite

scholarly journals A Simplified Scaling Law of Cell-Dendrite Transition in Directional Solidification

2019 ◽  
Vol 2019 ◽  
pp. 1-8
Author(s):  
Yaochan Zhu ◽  
Hua Qiu ◽  
Zhijun Wang ◽  
Eckart Schnack
Keyword(s):  
Directional Solidification ◽  
Phase Field ◽  
Thermal Gradient ◽  
Scaling Law ◽  
Primary Spacing ◽  
Cell Dendrite ◽  
Quantitative Phase ◽  
Physical Foundation ◽  
Pulling Velocity

To describe the cell-dendrite transition (CDT) during directional solidification, a new simplified scaling law is proposed and verified by quantitative phase field simulations. This scaling law bears clear physical foundation with consideration of the overall effects of primary spacing, pulling velocity, and thermal gradient on the onset of sidebranches. The analysis results show that the exponent parameters in this simplified scaling law vary within different systems, which mediates the discrepancy of exponent parameters in previous experiments. The scaling law also presents an explanation for the destabilizing mechanism of thermal gradient in sidebranching dynamics.

The effect of back-melting on the continuity of crystallographic orientation and composition in HgZnTe

1992 ◽  
Vol 50 (2) ◽  
pp. 1696-1697
Author(s):  
H.J. Zuo ◽  
M.W. Price ◽  
R.D. Griffin ◽  
R.A. Andrews ◽  
G.M. Janowski
Keyword(s):  
Directional Solidification ◽  
Space Shuttle ◽  
Solidification Process ◽  
Space Experiment ◽  
Infrared Detection ◽  
Directionally Solidified ◽  
Crystallographic Defects ◽  
Semiconducting Alloys ◽  
Uniform Composition ◽  
Growth Experiments

The II-VI semiconducting alloys, such as mercury zinc telluride (MZT), have become the materials of choice for numerous infrared detection applications. However, compositional inhomogeneities and crystallographic imperfections adversly affect the performance of MZT infrared detectors. One source of imperfections in MZT is gravity-induced convection during directional solidification. Crystal growth experiments conducted in space should minimize gravity-induced convection and thereby the density of related crystallographic defects. The limited amount of time available during Space Shuttle experiments and the need for a sample of uniform composition requires the elimination of the initial composition transient which occurs in directionally solidified alloys. One method of eluding this initial transient involves directionally solidifying a portion of the sample and then quenching the remainder prior to the space experiment. During the space experiment, the MZT sample is back-melted to exactly the point at which directional solidification was stopped on earth. The directional solidification process then continues.

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