Dendritic structure in unidirectionally solidified cyclohexanol

Okamoto, Takuya; Kishitake, Katsuhiko; Bessho, Isamu

doi:10.1016/0022-0248(75)90216-x

Cited by 61 publications

(31 citation statements)

References 6 publications

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“…7) Murakami et al reported that the deflection angle of dendrites in an Al-Cu alloy increased with increase in flow velocity and initial solute content. 8,9) Esaka et al also reported that the deflection angle of dendrites in steel increased with increase in initial carbon content.…”

Section: Introductionmentioning

confidence: 99%

“…It is well known that dendrites growing in a flowing melt tend to incline toward the upstream direction, and several mechanisms for dendrite deflection have been proposed. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] In an experiment using ice, Miksch found that the primary spine of the ice crystal was deflected toward the upstream direction and that the growth of secondary spines on the upstream side was markedly accelerated. 1) As a possible mechanism of ice dendrite deflection, Miksch suggested that a growing ice crystal is cooled at the upstream side by flowing cold water and is warmed at the downstream side by latent heat, resulting in growth of the crystal toward the upstream direction of the low temperature side.…”

Section: Introductionmentioning

confidence: 99%

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Investigation of the Mechanism of Alloy Dendrite Deflection due to Flowing Melt by Phase-Field Simulation

2002

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Phase-field simulation of the dendrite growth of an Fe-0.15 mass%C binary alloy with fluid flow was carried out, and the mechanism of deflection of dendrites in the alloy system was examined. In the simulation, the primary arms growing in a flowing melt inclined toward the upstream direction, and the deflection angle increased with increase in flow velocity. Decrease in deflection angle with increase in growth velocity of the dendrite tip and accelerated growth of side branches were also observed in the simulation. These results of simulation were in good agreement with experimental results. The simulation showed that the change in the thermal field has little effect on the deflection and that the change in the solutal field is the main factor responsible for the deflection of a dendrite in an alloy system. The maximum deflection angle of a single dendrite in the simulation was less than 15 • . The large deflection angles of grains (more than 20 • -30 • ) in the experiments were thought to have been caused by nucleation in front of the dendrites and the subsequent competitive growth.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Investigation of the Mechanism of Alloy Dendrite Deflection due to Flowing Melt by Phase-Field Simulation

2002

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“…[1][2][3] Through decreasing the thickness of boundary layer around dendritic grain and prompting the mass transfer in upstream direction, the fluid flow causes the dendrites to grow inclined toward the upstream direction and consequently modifies the preferred growth direction. It is found in unidirectional solidification experiments of Cyclohexanol that dendrites perfectly aligned with thermal gradient in the absence of fluid flow are deflected a few degrees by forced flow perpendicular to the growth direction, and the deflection angle of primary dendrite arms is dependent on the growth rate.…”

Section: Introductionmentioning

confidence: 99%

“…It is found in unidirectional solidification experiments of Cyclohexanol that dendrites perfectly aligned with thermal gradient in the absence of fluid flow are deflected a few degrees by forced flow perpendicular to the growth direction, and the deflection angle of primary dendrite arms is dependent on the growth rate. 1) Also in casting experiments of steel, this mechanism is responsible for the tendency of columnar grains growing toward upstream direction, and the deflection angle is deduced as a function of flow velocity and solidification rate. 2,3) To understand the formation of dendritic grain structure in solidification processes, Cellular Automaton (CA) model has been developed in parallel to experimental techniques.…”

Section: Introductionmentioning

confidence: 99%

Influences of Flow Intensity, Cooling Rate and Nucleation Density at Ingot Surface on Deflective Growth of Dendrites for Al-based Alloy

Zhang¹,

Nakajima

Wang³

et al. 2009

ISIJ Int.

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The dendrite tip growth kinetics in the flow field and the decentred quadrilateral growth algorithm for describing the evolution of grain growth are combined in Cellular Automaton model to predict the deflective growth of dendrites inclined toward upstream direction. The influences of flow intensity, cooling rate (or solidification rate), nucleation density at ingot surface on the deflective growth of dendrites are discussed. The increase of flow intensity dominantly forces the dendrites to grow in upstream direction; on the contrary, the increases of nucleation density at ingot surface and cooling rate suppress slightly this deflective growth. The relations predicted among deflection angle, flow intensity and solidification rate for Al-Si alloy and Al-Cu alloy show the same tendency as that in Okano et al.'s empirical expression deduced from experiments on steel. The deflection angle predicted for Al-Cu alloy fits well with previous experimental results.KEY WORDS: dendrite tip growth kinetics; decentred quadrilateral growth algorithm; Cellular Automaton; deflective growth of dendrites; flow intensity; cooling rate; nucleation density.quadrilateral growth algorithm are combined in two dimensional (2D) CA model to describe the deflective growth behaviors of dendrites in a flow field. Dendrite Tip Growth Kinetics in the Presence ofFluid Flow (the GGAN Model) The presence of fluid flow remarkably influences the dendrite tip growth kinetics by prompting the mass transfer in the boundary layer and consequently increasing the constitutional undercooling in the upstream direction ahead of the dendrite tip. Here, the dendrite tip growth kinetics (the GGAN model) 7) based on Stokes flow approximation is adopted to describe the steady state growth of a paraboloidal dendrite in an undercooled melt in the presence of fluid flow. The dimensionless supersaturation, W, is written as a function of the growth Peclet numbers, P v , the Reynolds number, Re 2r and the Schmidt number, Sc: where P u is the flow Peclet number, v tip is the dendrite tip growth rate, u is the relative velocity of liquid with respect to solid dendrite tip, n is the kinematic viscosity, D L is the diffusion coefficient of solute in liquid, q is the angle in radians between dendrite tip growth direction and flow direction. The constants in Eq. (1) are set as Aϭ0.5773, Bϭ 0.6596 and Cϭ0.5249. The exponential integral function,{exp(Ϫt)/t}dt, is estimated by polynomial interpolations. 8)In an undercooled melt, the local dendrite tip undercooling, DT, can be written as follows by neglecting the contributions of thermal undercooling and kinetics undercooling: (3) where C* is the local concentration in liquid at solid/liquid (S/L) interface.The dendrite tip radius is dependent on the dendrite tip growth rate following the marginal stability criterion 9) by ignoring the effect of the thermal gradients on each side of the solid-liquid interface, 10) .................. (4) where the stability constant, s*, is approximately taken as ( 4p 2 ) Ϫ1 . The dendrite tip ...

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“…It has now been well established that convection influences the planar-to-cellular transition [1][2][3][4] and the primary cellular/dendritic spacings. [5,6,7] During upward directional solidification, the thermal profile in the melt provides stability against convection because the melt density decreases with increasing temperature. However, the solutal profile in the melt is stabilizing only for those alloys where the increased solute content results in increased melt density, for example, hypoeutectic aluminum-copper alloy.…”

Section: Introductionmentioning

confidence: 99%

Effect of crucible diameter reduction on the convection, macrosegregation, and dendritic morphology during directional solidification of Pb-2.2 wt pct Sb alloy

Tewari

Magadi

deGroh

2003

Metall Mater Trans A

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Dendritic structure in unidirectionally solidified cyclohexanol

Cited by 61 publications

References 6 publications

Investigation of the Mechanism of Alloy Dendrite Deflection due to Flowing Melt by Phase-Field Simulation

Investigation of the Mechanism of Alloy Dendrite Deflection due to Flowing Melt by Phase-Field Simulation

Influences of Flow Intensity, Cooling Rate and Nucleation Density at Ingot Surface on Deflective Growth of Dendrites for Al-based Alloy

Effect of crucible diameter reduction on the convection, macrosegregation, and dendritic morphology during directional solidification of Pb-2.2 wt pct Sb alloy

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