The transition from columnar to equiaxed dendritic growth in proeutectic, low-volume fraction copper, Pb−Cu alloys

Kim, Shin‐Woo; Grugel, R. N.

doi:10.1007/bf02804373

Cited by 8 publications

(7 citation statements)

References 25 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…[3][4][5][6][7][8] In the present report, the focus is on the directional solidification of Al-and Zn-based alloys and, more particularly, on the columnar, equiaxed growth, and columnar-to-equiaxed transition (CET). Experimental evidence of the CET has been reported in previous articles, [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25] and also a number of mechanisms for the phenomenon of the CET have been proposed. It has been demonstrated that the CET is influenced by casting size, composition, and constitution of the alloy system, melt superheat, stirring, heat-transfer coefficient at the metal mold interface, inoculation, cooling rate of the mold, temperature gradient, etc.…”

Section: Introductionmentioning

confidence: 93%

Influence of Solidification Thermal Parameters on the Columnar-to-Equiaxed Transition of Aluminum-Zinc and Zinc-Aluminum Alloys

Ares

Schvezov

2007

Metall Mater Trans A

View full text Add to dashboard Cite

Understanding the interaction between the parameters involved in the columnar-to-equiaxed transition (CET) has gained considerable attention over the last two decades in the study of the structure of ingot castings. The present investigation was undertaken to investigate experimentally the directional solidification of Al-Zn and Zn-Al (ZA) alloys under different conditions of superheat and heat-transfer efficiencies at the metal/mold interface. The CET is observed; grain sizes are measured and the observations are related to the solidification thermal parameters: cooling rates, growth rates, thermal gradients, and recalescence determined from the temperature vs time curves. The temperature gradient in the melt, measured during the transition, is between -0.338°C/mm and 0.167°C/mm. In addition, there is an increase in the velocity of the liquidus front faster than the solidus front, which increases the size of the mushy zone. The size of the equiaxed grains increases with distance from the transition, an observation that was independent of alloy composition. The observations indicate that the transition is the result of a competition between coarse columnar dendrites and finer equiaxed dendrites. The results are compared with those previously obtained in lead-tin alloys.

show abstract

Section: Introductionmentioning

confidence: 93%

Influence of Solidification Thermal Parameters on the Columnar-to-Equiaxed Transition of Aluminum-Zinc and Zinc-Aluminum Alloys

Ares

Schvezov

2007

Metall Mater Trans A

View full text Add to dashboard Cite

show abstract

“…It can be seen from Figure 3(a) that grain growth is initially very slow (until about 200 seconds), which can be attributed to the small values of the envelope area concentration (S e ) in Eq. [7]; note that S e ϳ 1/R f , according to Eq. [12].…”

Section: A Solutal Interactionsmentioning

confidence: 99%

“…This rapid increase in g can be attributed to S e in Eq. [7] and to the solutal undercooling in Eq. [8] for the dendrite tip velocity simultaneously reaching larger values.…”

Section: A Solutal Interactionsmentioning

confidence: 99%

“…The final equation derived by Hunt [6] states that the CET occurs or will have occurred when the following condition holds: [1] Kim and Grugel [7] and Ledgard and McCartney [8] conducted steady-state solidification experiments in a Bridgeman-type furnace with an approximately constant temperature gradient using Pb-Cu and Al-Si alloys, respectively. It was observed that an increase in the columnar front velocity promoted equiaxed solidification, as predicted by Hunt's [6] equation.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

A solutal interaction mechanism for the columnar-to-equiaxed transition in alloy solidification

Martorano

Beckermann

Gandin

2003

Metall Mater Trans A

237

217

View full text Add to dashboard Cite

A multiphase/multiscale model is used to predict the columnar-to-equiaxed transition (CET) during solidification of binary alloys. The model consists of averaged energy and species conservation equations, coupled with nucleation and growth laws for dendritic structures. A new mechanism for the CET is proposed based on solutal interactions between the equiaxed grains and the advancing columnar frontas opposed to the commonly used mechanical blocking criterion. The resulting differences in the CET prediction are demonstrated for cases where a steady state can be assumed, and a revised isotherm velocity (V T ) vs temperature gradient (G) map for the CET is presented. The model is validated by predicting the CET in previously performed unsteady, unidirectional solidification experiments involving Al-Si alloys of three different compositions. Good agreement is obtained between measured and predicted cooling curves. A parametric study is performed to investigate the dependence of the CET position on the nucleation undercooling and the density of nuclei in the equiaxed zone. Nucleation undercoolings are determined that provide the best agreement between measured and calculated CET positions. It is found that for all three alloy compositions, the nucleation undercoolings are very close to the maximum columnar dendrite tip undercoolings, indicating that the origin of the equiaxed grains may not be heterogeneous nucleation, but rather a breakdown or fragmentation of the columnar dendrites.

show abstract

“…The effect of temperature gradient on the columnar to equiaxed transition (CET) has been extensively studied by both well controlled unidirectional solidification experiments in Bridgman furnace and non-steady state directional solidification by chill casting methods [19][20][21][22][23][24], as well as modeling studies [25][26][27][28][29][30][31]. It is well understood that a lower temperature gradient in the melt promotes CET.…”

Section: Introductionmentioning

confidence: 99%

Revealing the heterogeneous nucleation behavior of equiaxed grains of inoculated Al alloys during directional solidification

Casari

Mathiesen

et al. 2018

Acta Materialia

View full text Add to dashboard Cite

An in-situ study on the directional solidification of an inoculated Al-20 wt%Cu alloy under well-controlled constant cooling rates and temperature gradients has been carried out using a microfocus X-radiography set-up. The influences of temperature gradient and cooling rate on the heterogeneous nucleation rate and growth kinetics of equiaxed grains have been studied quantitatively. It is shown that under the same cooling rate, the nucleation rate of grains decreases with increasing temperature gradient. A high temperature gradient also promotes preferential growth of dendrite arms along the temperature gradient direction, and therefore the formation of elongated grains.However, the temperature gradient effects on nucleation and grain growth decrease with increasing cooling rate. It is revealed that the propagation velocity of the nucleation front in directional solidification castings is approximately equal to the ratio between cooling rate Ṫ and temperature gradient . Based on the experimental observations, a novel numerical grain size prediction model has been proposed, in which the temperature gradient effect on the nucleation kinetics was rigorously treated by introducing two new concepts termed as 'inhibited nucleation zone'(INZ) and 'active nucleation zone'(ANZ). The model has been applied to simulate the present insitu solidification experiments. A good agreement was achieved between the predicted grain number density and the experimental measurements, showing the importance of including the temperature gradient effect on heterogeneous nucleation. Furthermore, the present model also has the capability to predict the temperature gradient necessary for the transition from equiaxed to columnar grain growth.

show abstract

The transition from columnar to equiaxed dendritic growth in proeutectic, low-volume fraction copper, Pb−Cu alloys

Cited by 8 publications

References 25 publications

Influence of Solidification Thermal Parameters on the Columnar-to-Equiaxed Transition of Aluminum-Zinc and Zinc-Aluminum Alloys

Influence of Solidification Thermal Parameters on the Columnar-to-Equiaxed Transition of Aluminum-Zinc and Zinc-Aluminum Alloys

A solutal interaction mechanism for the columnar-to-equiaxed transition in alloy solidification

Revealing the heterogeneous nucleation behavior of equiaxed grains of inoculated Al alloys during directional solidification

Contact Info

Product

Resources

About