scholarly journals On the interest of microgravity experimentation for studying convective effects during the directional solidification of metal alloys

2017 ◽  
Vol 345 (1) ◽  
pp. 66-77 ◽  
Author(s):  
Henri Nguyen-Thi ◽  
Guillaume Reinhart ◽  
Bernard Billia
Keyword(s):  
Directional Solidification ◽  
Metal Alloys ◽  
Solidification Of Metal

Effect of Cooling Rate on the Structure of Rapidly Cooled Fe75Si15 B10

1983 ◽  
Vol 28 ◽  
Author(s):  
John L. Walter ◽  
Ami E. Berkowitz
Keyword(s):  
Cooling Rate ◽  
Melt Spinning ◽  
Structural Characteristics ◽  
Rapid Quenching ◽  
Metal Alloys ◽  
X Ray Diffraction ◽  
X Ray ◽  
Spark Erosion ◽  
Water Atomization ◽  
Solidification Of Metal

Solidification of metal alloys by rapid quenching can result in the formation of amorphous or microcrystalline solids, or materials with improved microstructural homogeneity, all with the view of forming new phases or obtaining improved properties. Some alloys may be cooled at high rates to achieve “microcrystallinity” but cannot be cooled rapidly enough to become amorphous. Other alloys may achieve both conditions depending on the cooling rate. We have examined the effects of cooling rate on the structure of one alloy that can, depending on the cooling rate, be made partially or completely amorphous. The alloy is Fe75Si15B10 (atom percent) which was formed as ribbon by melt spinning and as powder by spark erosion in dielectrics of different cooling characteristics and by gas-water atomization. The structural characteristics were determined by x-ray diffraction, measurements of magnetic properties and by optical and scanning electron microscopy.

The Effect of The Natural Convection on The Transition from Columnar to Equiaxed Crystals:

1981 ◽  
Vol 9 ◽  
Author(s):  
Hasse Fredriksson
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Solidification Front ◽  
Growth Process ◽  
Solidification Process ◽  
Temperature Gradients ◽  
Metal Alloys ◽  
Dendritic Solidification ◽  
Kinetics Of ◽  
Solidification Of Metal

ABSTRACTDuring dendritic solidification of metal alloys there normally occur temperature gradients in the liquid ahead of the solidification front. The gradient causes a natural convection ahead of the front. The natural convection causes a heat transfer from the interior of the liquid, which gives the possibility for crystals to grow ahead of the solidification front. The growth of these crystals is determined by the cooling rate and the kinetics of the solidification process. The paper will deal with the theory behind the growth of free crystals ahead of a solidification front. Some experimental results will be given. The effect of gravity on the growth process will. be discussed.

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.

Specimen Preparation of Near Surface Ion Irradiated Samples

1985 ◽  
Vol 43 ◽  
pp. 170-171
Author(s):  
K. F. Russell ◽  
L. L. Horton
Keyword(s):  
Radiation Damage ◽  
Heavy Ions ◽  
Target Material ◽  
Metal Alloys ◽  
Specimen Surface ◽  
Specimen Preparation ◽  
Particle Accelerators ◽  
Near Surface ◽  
Graaff Accelerator ◽  
Van De Graaff

Beams of heavy ions from particle accelerators are used to produce radiation damage in metal alloys. The damaged layer extends several microns below the surface of the specimen with the maximum damage and depth dependent upon the energy of the ions, type of ions, and target material. Using 4 MeV heavy ions from a Van de Graaff accelerator causes peak damage approximately 1 μm below the specimen surface. To study this area, it is necessary to remove a thickness of approximately 1 μm of damaged metal from the surface (referred to as “sectioning“) and to electropolish this region to electron transparency from the unirradiated surface (referred to as “backthinning“). We have developed electropolishing techniques to obtain electron transparent regions at any depth below the surface of a standard TEM disk. These techniques may be applied wherever TEM information is needed at a specific subsurface position.

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