Containerless Processing in the Study of Metastable Solids from Undercooled Melts

2014 ◽  
Vol 526 ◽  
pp. 21-27 ◽  
Author(s):  
Dieter Herlach
Keyword(s):  
High Speed ◽  
Growth Dynamics ◽  
High Growth ◽  
Dendrite Growth ◽  
Crystal Nucleation ◽  
In Situ Observation ◽  
Containerless Processing ◽  
Equilibrium Solidification ◽  
Undercooled Melts ◽  
Non Equilibrium

An undercooled melt possesses an enhanced free enthalpy that enables to crystallize metastable solids in competition with their stable counterparts. Crystal nucleation selects the crystallographic phase whereas the growth dynamics controls microstructure evolution. We apply containerless processing such as electromagnetic and electrostatic levitation to containerlesss undercool and solidify metallic melts. Heterogeneous nucleation on container-walls is completely avoided leading to large undercooling with the extra benefit that the freely suspended drop is direct accessible for in situ observation of crystallization far away from equilibrium. Results of investigations of maximum undercoolability on pure zirconium are presented showing the limit of maximum undercoolability set by the onset of homogeneous nucleation. Rapid dendrite growth is measured as a function of undercooling by a high-speed camera and analysed within extended theories of non-equilibrium solidification. In such both supersaturated solid solutions and disordered superlattice structure of intermetallics are formed at high growth velocities. A sharp interface theory of dendrite growth is capable to describe the non-equilibrium solidification phenomena during rapid crystallization of deeply undercooled melts.

scholarly journals A Three Dimensional Cellular Automata Model for Dendrite Growth in Non-Equilibrium Solidification of Binary Alloy

2015 ◽  
Vol 86 (12) ◽  
pp. 1490-1497 ◽  
Author(s):  
Yan Zhao ◽  
Rongshan Qin ◽  
Dengfu Chen ◽  
Xinming Wan ◽  
Yang Li ◽  
...  
Keyword(s):  
Cellular Automata ◽  
Binary Alloy ◽  
Three Dimensional ◽  
Dendrite Growth ◽  
Cellular Automata Model ◽  
Equilibrium Solidification ◽  
Non Equilibrium

scholarly journals Non-equilibrium solidification and microsegregation in centrifugally cast high speed steel for rolls

2018 ◽  
Vol 54 (1) ◽  
pp. 59-66 ◽  
Author(s):  
U. Klancnik ◽  
B. Kosec ◽  
P. Mrvar ◽  
J. Medved
Keyword(s):  
Electron Microscopy ◽  
High Speed ◽  
Light And Electron Microscopy ◽  
High Speed Steel ◽  
Scanning Calorimetry ◽  
Centrifugally Cast ◽  
Eutectic Carbides ◽  
Thermo Calc Software ◽  
Equilibrium Solidification ◽  
Non Equilibrium

When regarding as-cast microstructures of highly alloyed metals, microsegregation of alloying elements is a common feature resulting from non-equilibrium conditions during solidification. The aim of this work is to predict the occurrence and severity of microsegregation in highly alloyed, centrifugally cast high speed steel used for rolls. The prediction was performed using thermodynamic Scheil-Gulliver modelling with Thermo-Calc software. The modelled predictions were then compared with differential scanning calorimetry, X-ray diffraction, light and electron microscopy with energy dispersive spectroscopy, all performed on an as-cast roll shell. Results show that chromium, molybdenum and vanadium have the highest tendency to microsegregation. Vanadium tends to form negative microsegregation, while molybdenum and chromium form positive microsegregation. Scanning electron microscopy revealed the presence of complex eutectic carbides, confirming the Scheil-Gulliver non-equilibrium solidification path via two main successive eutectic reactions.

Non-Equilibrium and Near-Equilibrium Solidification of Undercooled Melts of Ni- and Al-based Alloys

2008 ◽  
Vol 10 (5) ◽  
pp. 444-452 ◽  
Author(s):  
D. M. Herlach ◽  
R. Lengsdorf ◽  
P. Galenko ◽  
H. Hartmann ◽  
C.-A. Gandin ◽  
...  
Keyword(s):  
Equilibrium Solidification ◽  
Undercooled Melts ◽  
Non Equilibrium

scholarly journals Crystal growth kinetics in undercooled melts of pure Ge, Si and Ge–Si alloys

2018 ◽  
Vol 376 (2113) ◽  
pp. 20170205 ◽  
Author(s):  
Dieter M. Herlach ◽  
Daniel Simons ◽  
Pierre-Yves Pichon
Keyword(s):  
Crystal Growth ◽  
Growth Kinetics ◽  
High Speed ◽  
Growth Dynamics ◽  
Electromagnetic Levitation ◽  
Electron Microscopic ◽  
Interface Theory ◽  
Crystal Growth Kinetics ◽  
Scanning Electron Microscopic ◽  
Undercooled Melts

We report on measurements of crystal growth dynamics in semiconducting pure Ge and pure Si melts and in Ge 100− x Si x ( x  = 25, 50, 75) alloy melts as a function of undercooling. Electromagnetic levitation techniques are applied to undercool the samples in a containerless way. The growth velocity is measured by the utilization of a high-speed camera technique over an extended range of undercooling. Solidified samples are examined with respect to their microstructure by scanning electron microscopic investigations. We analyse the experimental results of crystal growth kinetics as a function of undercooling within the sharp interface theory developed by Peter Galenko. Transitions of the atomic attachment kinetics are found at large undercoolings, from faceted growth to dendrite growth. This article is part of the theme issue ‘From atomistic interfaces to dendritic patterns’.

scholarly journals A numerical study of dendrite growth and microstructure transition in a non-equilibrium solidification

2021 ◽  
Vol 1939 (1) ◽  
pp. 012018
Author(s):  
Xiaohuia Ao ◽  
Huanxiong Xia ◽  
Jianhua Liu ◽  
QiYang He ◽  
Shengxiang Lin
Keyword(s):  
Numerical Study ◽  
Dendrite Growth ◽  
Equilibrium Solidification ◽  
Non Equilibrium

GROWTH OF PIKE-PERCH SANDER LUCIOPERCA (L., 1758) (PERCIDAE) IN RESERVOIRS OF K. SATPAYEV’S CHANNEL

2018 ◽  
pp. 59-68
Author(s):  
Saule Zhangirovna Asylbekova ◽  
Kuanysh Baibulatovich Isbekov ◽  
Vladimir Nickolaevich Krainyuk
Keyword(s):  
Growth Rates ◽  
Growth Dynamics ◽  
High Growth ◽  
Water Bodies ◽  
Volga River ◽  
Trophic Resources ◽  
Pike Perch ◽  
The Amur River ◽  
Back Calculation ◽  
Abiotic And Biotic Factors

Pike-perch is an invader for the water basins of Central Kazakhstan. These species have stable self-reproductive populations in the regional waters. Back calculation method was used to investigate pike-perch growth rates in reservoirs of K. Satpayev’s channel. For comparison, the data from the other water bodies (Vyacheslavsky and Sherubay-Nurinsky water reservoirs) were used, as well as literature data. Pike-perch species from the investigated waters don’t show high growth rates. The populations from the reservoirs of K. Satpayev’s channel have quite similar growth rates with populations from the Amur river, from a number of reservoirs in the Volga river basin and from the reservoir in Spain. Sexual differences in growth have not been observed. Evaluating possible influence of various abiotic and biotic factors on the growth rate of pike-perch in the reservoirs of K. Satpayev’s channel was carried out. It has been stated that the availability of trophic resources cannot play a key role in growth dynamics because of their high abundance. Morphology of water bodies also does not play a role, as well as chromaticity, turbidity and other optical water indicators. It can be supposed that the main factor influencing growth of pike perch is the habitat’s temperature. This factor hardly ever approaches optimal values for the species in reservoirs of K. Satpaev’s channel. The possible influence of fishing selectivity on pike-perch growth rates was also evaluated. Currently, there has been imposed a moratorium on pike-perch catch. However, pike-perch is found in by-catches and in catches of amateur fishermen. It should be said that such seizures have an insignificant role in the dynamics of growth rates.

In Situ Observation Method for Quantitative Evaluation of Solidification Phenomena and Solidification Cracks during Welding

2014 ◽  
Vol 782 ◽  
pp. 3-7
Author(s):  
Kenji Shinozaki ◽  
Motomichi Yamamoto ◽  
Kohta Kadoi ◽  
Peng Wen
Keyword(s):  
High Speed ◽  
Video Camera ◽  
Solidification Cracking ◽  
In Situ Observation ◽  
High Speed Video Camera ◽  
Varestraint Test ◽  
Solidification Cracks ◽  
Observation Method ◽  
Solidification Crack

Solidification cracking during welding is very serious problem for practical use. Therefore, there are so many reports concerning solidification cracking. Normally, solidification cracking susceptibility of material is quantitatively evaluated using Trans-Varestraint test. On the other hand, local solidification cracking strain was tried to measure precisely using in-situ observation method, called MISO method about 30 years ago. Recently, digital high-speed video camera develops very fast and its image quality is very high. Therefore, we have started to observe solidification crack using in site observation method. In this paper, the local critical strain of a solidification crack was measured and the high temperature ductility curves of weld metals having different dilution ratios and different grain sizes to evaluate quantitatively the effects of dilution ratio and grain size on solidification cracking susceptibility by using an improved in situ observation method.

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