Morphological stability during directional solidification into an oscillatory molten zone

Chung, C. A.; Ho, K.H.; Chou, Ping-Yao

doi:10.1016/j.jcrysgro.2004.11.322

Cited by 3 publications

(3 citation statements)

References 27 publications

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“…Still the convection pattern and the temperature field alter periodically. Effect of vibration on the morphological stability and microstructure has not been well understood, but it is certain that the vibration can affect solidification microstructure, and enhance the morphological stability during the directional solidification process of alloys [14][15][16]. The vibration pattern caused by SSC may be more favorable to the stability of the S/L interface than that of ECP.…”

Section: Periodic Characteristic Of Currentsmentioning

confidence: 99%

Effect of currents on the microstructure of directionally solidified Al–4.5 wt% Cu alloy

Song¹,

Guo²,

Zhang³

et al. 2011

Journal of Crystal Growth

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Section: Periodic Characteristic Of Currentsmentioning

confidence: 99%

Effect of currents on the microstructure of directionally solidified Al–4.5 wt% Cu alloy

Song¹,

Guo²,

Zhang³

et al. 2011

Journal of Crystal Growth

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“…ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 134.129.120 3. Downloaded on 2015-05-26 to IP…”

mentioning

confidence: 99%

“…1,2 In their pioneering studies, they showed that the morphological instability sets in when the destabilizing surface-concentration gradient overcomes the stabilizing surface tension. Since then, the Mullins-Sekerka-type criterion has played a standard role in the studies on the evolution of surface irregularity, such as directional solidification, 3 chemical vapor deposition, 4 and electrochemical deposition. 5 In practice, it is important to control the surface roughness in the manufacturing process.…”

mentioning

confidence: 99%

Effect of Buoyancy on Morphological Instability during Electrochemical Deposition

Chung

Kim

Yoon

et al. 2007

J. Electrochem. Soc.

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In the present study, the morphological instability during an electrochemical deposition is considered with a linear stability analysis, and also the effect of buoyancy-driven convection on the evolution of surface unevenness is tested. In the absence of buoyant forces, the surface concentration gradient enhanced the surface roughness while the surface tension stabilized the growth of protuberances on the surface, which is in good agreement with the existing results. Near the onset of convective motion, the surface irregularity is damped by an increase in the buoyant force. As the buoyancy is further strengthened, the phase transition from a stationary behavior to an oscillating one is observed.Many studies on morphological instability have been done since the original works of Mullins and Sekerka. 1,2 In their pioneering studies, they showed that the morphological instability sets in when the destabilizing surface-concentration gradient overcomes the stabilizing surface tension. Since then, the Mullins-Sekerka-type criterion has played a standard role in the studies on the evolution of surface irregularity, such as directional solidification, 3 chemical vapor deposition, 4 and electrochemical deposition. 5 In practice, it is important to control the surface roughness in the manufacturing process. 6 The electrochemical deposition system is very popular due to its simple process and low cost, but there is still a serious problem that involves the unavoidable appearance of morphological irregularities.Aogaki et al. 5 analyzed the powder crystal formation on the electrode surface under pontentiostatic conditions, and also focused systematically on the mechanism of morphological instability under the galvanostatic condition. 7,8 After these studies, much critical research was conducted on the effective factors that influence the onset of morphological instability, for example, the absence of ohmic potential, the variation of boundary-layer thickness, the effect of supporting electrolyte, the capillary effect, and the effect of additives. On the basis of the Mullins-Serkerka criterion, 1,2 they are well summarized by Schwarzacher. 9 In the electrochemical deposition system, another physical phenomenon is the onset of buoyancy-driven convection. If the upward facing cathode is located below the downward facing anode in the electrolyte-saturated cell, the electrodissolution and deposition of metal ion will proceed on the upper and lower electrodes with an external potential supply. Gradually, the concentration of electrolyte near the upper electrode becomes higher than that near the lower electrode. This causes such a buoyancy-driven convection as the Rayleigh-Bénard convection. 10 In the presence of buoyancy, the convection can lead to unexpected redistribution of concentration field near the growth front. The convective motion can be readjusted by moving the diffusion boundary layer, and therefore, the coupling behavior between convection and morphological change is very complicated. In case of the coupled morphologic...

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Morphological Instabilities in Time Periodic Crystallization

2007

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A linear stability analysis is performed on the interface that forms during directional solidification of a dilute binary alloy in the presence of time-periodic growth rates. The basic state, in which the flat crystal-melt interface advances at a steady rate with an oscillation superimposed, is solved analytically by expanding the governing equations in terms of the assumed-small amplitude of modulation. We find that there is a frequency window of stabilization, in which the Mullins-Sekerka instability can be stabilized synchronously. Outside of the window, large input frequencies may destabilize the Mullins-Sekerka mode. The subharmonic mode, which occurs with small wave numbers, is stabilized with increasing the frequency. As for the modulation amplitude, larger amplitude tends to reduce the synchronous mode while enhance the subharmonic mode.

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Morphological stability during directional solidification into an oscillatory molten zone

Cited by 3 publications

References 27 publications

Effect of currents on the microstructure of directionally solidified Al–4.5 wt% Cu alloy

Effect of currents on the microstructure of directionally solidified Al–4.5 wt% Cu alloy

Effect of Buoyancy on Morphological Instability during Electrochemical Deposition

Morphological Instabilities in Time Periodic Crystallization

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