THE FORMATION OF STRIATION-TYPE SUBSTRUCTURE IN ALUMINUM

Striations are one type of substructure which can form in metals as they solidify from the melt. The formation of striations is dependent upon the rate of crystal growth, the purity, and the crystallographic orientation. In aluminum single crystals, it was found that striation boundaries tended to approach a preferred (100) growth direction with increasing rate of growth and with increasing solute concentration. With different types of solute, it appears that similar values of the average concentration of solute in the liquid at the solid–liquid interface (C0/k) produced the same effect on striation direction.The number of striations found in any sample appeared to be a complex function of the purity, the orientation, and the rate of growth.

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Study on the Natural Convection and Formation of Periodic Diphase Dendrite in Al-La Alloys

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.129-131.1308 ◽

2010 ◽

Vol 129-131 ◽

pp. 1308-1312

Author(s):

Ya Hong Zheng ◽

Yan Lin Wang ◽

Zi Dong Wang

Keyword(s):

Crystal Growth ◽

Natural Convection ◽

Concentration Distribution ◽

Concentration Field ◽

Growth Direction ◽

Liquid Interface ◽

Dendrite Morphology ◽

Solid Liquid Interface ◽

Solid Liquid ◽

Interface Edge

In the crystal growth process, the temperature distribution and concentration distribution at the solid-liquid interface edge are always the hot problems. In this paper, we study the concentration distribution at the solid-liquid interface edge under the natural convection conditions, we find that the concentration field is oscillating exponential decline or rose along the crystal growth direction. We also study the dendrite morphology of Al-La alloys using the experimental method, the results show that the microstructure of Al-35%La alloys is different from the common microstructure of hypereutectic alloy during the conventional casting process, the first crystalline phase is Al11La3, which composition is discontinuous along the growth direction, the main dendrite is composed of α-Al alternating with Al11La3, the results of SEM and XRD show that the chemical composition along the main dendrite exhibits periodic behavior, therefore, this microstructure is named as periodic diphase dendrite structure.

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Mechanics of shaped crystal growth from the melt

Journal of Materials Research ◽

10.1557/jmr.1996.0276 ◽

1996 ◽

Vol 11 (9) ◽

pp. 2163-2176 ◽

Cited By ~ 11

Author(s):

John C. Lambropoulos ◽

Chien-Hsing Wu

Keyword(s):

Crystal Growth ◽

Dislocation Density ◽

Growth Parameters ◽

Growth Direction ◽

Liquid Interface ◽

Dislocation Generation ◽

Crystalline Anisotropy ◽

Initial Dislocation Density ◽

Solid Liquid Interface ◽

Solid Liquid

We present the numerical formulation of the thermal stress driven steady-state dislocation generation during the growth of shaped crystals from the melt, with Czochralski (CZ) growth of solid cylinder III–V compound semiconductors as an example. We use and compare the Haasen–Alexander model, coupling dislocation multiplication and creep strain rates, and the Jordan model, based on thermoelastic stresses. Growth parameters may be chosen so as to produce an overall approximately flat interface, leading to reduced dislocation density in the majority of the crystal's cross section. Calculation of final dislocation density requires the initial dislocation density and all stress components along the solid-liquid interface, microstructural features which depend on the physical processes leading to solidification. The final dislocation density is not sensitive to the initial dislocation density along the solid-liquid interface, but strongly depends on the interface stress. Significant stress relaxation at the interface is required to produce experimentally observed “W” shaped dislocation patterns. Crystal growth direction and crystalline anisotropy couple elastic (lattice) and plastic (slip systems) crystalline anisotropy.

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Numerical Analysis of Difficulties of Growing Large-Size Bulk β-Ga2O3 Single Crystals with the Czochralski Method

Crystals ◽

10.3390/cryst11010025 ◽

2020 ◽

Vol 11 (1) ◽

pp. 25

Author(s):

Xia Tang ◽

Botao Liu ◽

Yue Yu ◽

Sheng Liu ◽

Bing Gao

Keyword(s):

Crystal Growth ◽

Single Crystals ◽

Czochralski Method ◽

Liquid Interface ◽

Spiral Growth ◽

Growth Time ◽

Large Size ◽

Crystal Diameter ◽

Solid Liquid Interface ◽

Solid Liquid

The difficulties in growing large-size bulk β-Ga2O3 single crystals with the Czochralski method were numerically analyzed. The flow and temperature fields for crystals that were four and six inches in diameter were studied. When the crystal diameter is large and the crucible space becomes small, the flow field near the crystal edge becomes poorly controlled, which results in an unreasonable temperature field, which makes the interface velocity very sensitive to the phase boundary shape. The effect of seed rotation with increasing crystal diameter was also studied. With the increase in crystal diameter, the effect of seed rotation causes more uneven temperature distribution. The difficulty of growing large-size bulk β-Ga2O3 single crystals with the Czochralski method is caused by spiral growth. By using dynamic mesh technology to update the crystal growth interface, the calculation results show that the solid–liquid interface of the four-inch crystal is slightly convex and the center is slightly concave. With the increase of crystal growth time, the symmetry of cylindrical crystal will be broken, which will lead to spiral growth. The numerical results of the six-inch crystal show that the whole solid–liquid interface is concave and unstable, which is not conducive to crystal growth.

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Metachromasy in clay dye systems: the adsorption of acridine orange by Na-beidellite

Clay Minerals ◽

10.1180/000985599546361 ◽

1999 ◽

Vol 34 (3) ◽

pp. 459-467 ◽

Cited By ~ 17

Author(s):

D. Garfinkel-Shweky ◽

S. Yariv

Keyword(s):

Acridine Orange ◽

Interlayer Space ◽

Degree Of Saturation ◽

Visible Spectroscopy ◽

Absorption Bands ◽

Colloidal Properties ◽

Different Types ◽

Solid Liquid Interface ◽

Solid Liquid ◽

Absorbance Curve

AbstractThe adsorption of the metachromic dye acridine orange (AO) by Na-beidellite was investigated by visible spectroscopy. Different types of clay-AO association were identified from the appearance and location of absorption bands α or β. The colloidal properties were determined from curves of the absorbance vs. the degree of saturation. Three regions were identified in the absorbance curve. In the first region beidellite is peptized with small amounts of AO and the dye penetrates into the interlayer space where it undergoes metachromasy due to π interactions between the aromatic entity and the oxygen plane of the clay. With larger amounts of AO (second region), the clay flocculates due to the aggregation of the dye cations in the interparticle space of the flocs. In excess AO (third region), beidellite is gradually peptized, forming small tactoids with monomeric AO in the interlayer space and at the same time adsorbing dimeric and polymeric AO cationic species at the solid-liquid interface. Compared with the other smectites, AO shows the greatest tendency to undergo metachromasy in the presence of beidellite.

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Solidification parameters of the solid-liquid interface in crystal growth in response to vibration

Journal of Materials Science ◽

10.1007/bf00355960 ◽

1994 ◽

Vol 29 (15) ◽

pp. 3997-4000 ◽

Cited By ~ 12

Author(s):

Wang Fengquan ◽

Chen Shiyu ◽

He Deping ◽

Wei Bingbo ◽

Shu Guangji

Keyword(s):

Crystal Growth ◽

Liquid Interface ◽

Solidification Parameters ◽

Solid Liquid Interface ◽

Solid Liquid

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Crystal Growth Mechanism of YBCO Superconductors Prepared by Unidirectional Solidification Method

Materials Science Forum ◽

10.4028/www.scientific.net/msf.546-549.2085 ◽

2007 ◽

Vol 546-549 ◽

pp. 2085-2090

Author(s):

En Zhi Gao ◽

Jin Shan Li ◽

Rui Hu ◽

Hong Chao Kou ◽

Hai Tao Cao ◽

...

Keyword(s):

Crystal Growth ◽

Growth Mechanism ◽

Structural Characteristics ◽

Solid State Reaction Method ◽

Optical Microscope ◽

Unidirectional Solidification ◽

Ybco Superconductor ◽

Crystal Growth Mechanism ◽

Solid Liquid Interface ◽

Solid Liquid

Y123 and Y211 powders were synthesized by solid-state reaction method. YBCO superconductor specimens were prepared by unidirectional solidification technique. The microstructure and the structural characteristics were observed by means of the optical microscope, X-ray diffraction (XRD), scanning electron microscope (SEM). The results showed that the specimen have a highly aligned structure, it was observed obvious laminated structure of Y123 crystal. Crystal growth mechanism of YBCO was investigated. Jackson's factor of Y123 crystal was calculated. Interface form was judged tentatively theoretically. The specimen was rapidly quenched by quick pulling. Solid/liquid interface structure was observed. It was concluded that a-b plane was faceted grow forms and layer growing along c-axial on a-b plane.

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Resistivity Distribution Characteristics of Metallurgical Silicon Ingot after Directional Solidification

Materials Science Forum ◽

10.4028/www.scientific.net/msf.675-677.109 ◽

2011 ◽

Vol 675-677 ◽

pp. 109-112

Author(s):

Shu Ang Shi ◽

Wei Dong ◽

Shi Hai Sun ◽

Yi Tan ◽

Guo Bin Li ◽

...

Keyword(s):

Directional Solidification ◽

Vertical Section ◽

Growth Direction ◽

Silicon Ingot ◽

Metallurgical Silicon ◽

High Impurity ◽

Polarity Transition ◽

High Impurity Concentration ◽

Solid Liquid Interface ◽

Solid Liquid

The distribution of resistivity, impurity and polarity in multicrystalline silicon ingot prepared by directional solidification method was detected. The effect of impurity distribution on resistivity was also researched. The results show that the shapes of equivalence line of resistivity in the cross section and vertical section of the silicon ingot depend on the solid-liquid interface. The resistivity in the vertical section increases with the increasing of solidified height at the beginning of solidification and reaches to maximum at the polarity transition point, then decreases rapidly with the increasing of solidified height and tends to zero on the top of the ingot because of the high impurity concentration. Study proves that the variation of resistivity in the vertical section is mainly relevant to the concentration distribution of the impurities such as Al, B and P in the growth direction.

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