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利用高速摄影技术, 实时记录了功率超声作用下succinonitrile-8.3% Water(摩尔分数为8.3%)溶液凝固过程中稳态空化气泡与枝晶间的相互作用, 并结合数值模拟揭示了稳态空化对枝晶生长的影响机制. 结果表明, 稳态空化能够加速枝晶生长、促使枝晶臂断裂和吸附球状晶生长. 当气泡的迁移方向与枝晶生长方向一致时, 气泡振荡过程中产生的周期性高压导致周围熔体过冷, 从而加速枝晶生长. 当稳态空化气泡向固相内部迁移时, 其振荡引发枝晶臂内部产生大于屈服强度的应力, 促使枝晶臂变形和断裂. 同时悬浮于固-液界面前沿的稳态空化气泡能够在周围液相中产生局部的周期性变化流场和高剪切力, 使得邻近的枝晶碎片将吸附在其周围并以球状晶形态生长.Ultrasonic waves used in liquid alloys can produce refined grain structures, which mainly contributes to ultrasonic cavitation and acoustic streaming. According to the bubble lifetime and whether they are fragmented into “daughter” bubbles, acoustic cavitation can be divided into transient cavitation and stable cavitation. Compared with the transient cavitation, the interaction between stable cavitation bubbles and solidifying alloys have been rarely investigated previously . In this work, the effect of stable cavitation on the dendritic growth of succinonitrile (SCN)-8.3% (mole fraction) water organic transparent alloy is systematically investigated by high-speed digital image technique and numerical simulation. It is found that when the bubble migration direction is consistent with that of dendritic growth, the periodic high pressure generated in bubble oscillation process increases the local undercooling, speeding up the dendrites growth effectively. Meanwhile, the concentrated stress inside dendrites induced by the linearly oscillation of cavitation bubble can break up dendrites into fragments. Specifically, if there exist stable cavitation bubbles suspended around the liquid-solid interface, periodically alternating flow field and high shear force in their surrounding liquid phase is produced. As a result, the nearby dendritic fragments will be attracted to those bubbles and then transformed into spherical grains.
[1] Eskin G I, Eskin D G 2014 Ultrasonic Treatment of Light Alloy Melts (2nd Ed.) (London: CRC Press) pp32–43
[2] Hu Y J, Wang X, Wang J Y, Zhai W, Wei B 2021 Metall. Mater. Trans. A 52 3097
Google Scholar
[3] Feng X H, Zhao F Z, Jia H M, Zhou J X, Li Y D, Li W R, Yang Y S 2017 Int. J. Cast Metal. Res. 30 341
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[4] Yasui K 2018 Acoustic cavitation and bubble dynamics (Switzerland: Springer International) pp14, 15
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Google Scholar
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Google Scholar
[7] Koukouvinis P, Gavaises M, Supponen O, Farhat M 2016 Phys. Fluids 28 052103
Google Scholar
[8] Feng X H, Zhao F Z, Jia H M, Li Y J, Yang Y S 2018 Ultrason. Sonochem. 40 113
Google Scholar
[9] Chow R, Blindt R, Chivers R, Povey M 2005 Ultrasonics 43 227
Google Scholar
[10] Zhao Y, Zheng Q L, Liu Z W 2020 Mater. Lett. 274 128030
Google Scholar
[11] Shu D, Sun B D, Mi J W, Grant P S 2012 Metall. Mater. Trans. A 43 3755
Google Scholar
[12] Tan D Y, Mi J W 2013 Mater. Sci. Forum 765 230
Google Scholar
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Google Scholar
[14] Wang B, Tan D Y, Lee T L, Khong J C, Wang F, Eskin D, Connolley T, Fezzaa K, Mi J W 2018 Acta Mater. 144 505
Google Scholar
[15] Todaro C J, Easton M A, Qiu D, Zhang D, Bermingharm M J, Lui E W, Brandt M, Stjohn D H, Qian M 2020 Nat. Commun. 11 142
Google Scholar
[16] 徐珂, 许龙, 周光平 2021 70 194301
Google Scholar
Xu K, Xu L, Zhou G P 2021 Acta Phys. Sin. 70 194301
Google Scholar
[17] Omoteso K A, Roy-Layinde T O, Laoye J A, Vincent U E, McClintock P V E 2021 Ultrason. Sonochem. 70 105346
Google Scholar
[18] Lofstedt R, Barber B P, Putterman S J 1993 Phys. Fluids A 5 2911
Google Scholar
[19] Lin H, Storey B D, Szeri A J, Andrew J S 2002 J. Fluid Mech. 452 145
Google Scholar
[20] Murakami K, Yamakawa Y, Zhao J Y, Johnsen E, Ando K 2021 J. Fluid Mech. 924 A38
Google Scholar
[21] Wang S, Guo Z P, Zhang X P, Zhang A, Kang J W 2019 Ultrason. Sonochem. 51 160
Google Scholar
[22] Koss M B, LaCombe J C, Tennenhouse L A, Glicksman M E, Winsa E A 1999 Metall. Mater. Trans. A 30 3177
Google Scholar
[23] Shang S, Han Z Q 2019 J. Mater. Sci. 54 3111
Google Scholar
[24] Cattaneo C A, Evequoz O P E, Bertorello H R 1994 Scripta Metall. Mater. 31 461
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[25] Cain J B, Clunie J C, Baird J K 1995 Int. J. Thermophys. 16 1225
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[26] 高学鹏, 李新涛, 郄喜望, 吴亚萍, 李喜孟, 李廷举 2007 56 1188
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[29] Longuet-Higgins M S 1998 P. Roy. Soc. A-Math. Phy. 454 725
Google Scholar
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图 1 SCN-H2O溶液的超声凝固观测实验以及数值模型示意图 (a) 单轴超声凝固原位观测装置示意图; (b) SCN-8.3%H2O溶液在SCN-H2O平衡相图中的位置, 图中S表示固态, L表示液态; (c) 气泡稳态振荡作用下枝晶内部应力分布的数值模型示意图
Fig. 1. Schematic of experiment and numerical model: (a) In situ observation experiment setup of uniaxial ultrasonic solidification; (b) position of SCN-8.3% H2O solution in equilibrium phase diagram; (c) numerical model of stress distribution inside dendrite under a stable bubble oscillation. a stable bubble oscillation.
图 2 稳态空化气泡作用下枝晶生长过程 (a) t = 0 s; (b) t = 1.02 s; (c) t = 2.96 s; (d) t = 5.94 s
Fig. 2. In situ observation of dendritic growth under the action of stable cavitation: (a) t = 0 s; (b) t = 1.02 s; (c) t = 2.96 s; (d) t = 5.94 s.
图 3 气泡稳态振荡过程中枝晶生长速率的变化规律 (a) 枝晶主干长度L随时间t的变化; (b) 一个振荡周期内过冷度随时间的变化; (c) LKT模型拟合的枝晶生长速率与过冷度的关系
Fig. 3. Influence of dendritic growth velocity induced by a stable cavitation bubble: (a) Evolution of primary dendritic length with time; (b) variation of local undercooling in one oscillation period; (c) relationship between dendritic growth velocity and undercooling by LKT model.
图 4 向固相内部迁移的气泡与枝晶生长的相互作用 (a) t = 0 s; (b) t = 0.24 s; (c) t = 0.82 s; (d) t = 5.04 s; (e) t = 7.42 s; (f) t = 11.26 s
Fig. 4. Images of the interaction between the stable bubble migrating into solid phase and growing dendrites: (a) t = 0 s; (b) t = 0.24 s; (c) t = 0.82 s; (d) t = 5.04 s; (e) t = 7.42 s; (f) t = 11.26 s.
图 5 空化气泡稳态振荡导致与其接触的二次枝晶臂根部弯曲、断裂的动态过程 (a) t = 0 ms; (b) t = 2.34 ms; (c) t = 4.68 ms; (d) t = 8.19 ms; (e) t = 9.36 ms; (f) t = 10.11 ms
Fig. 5. Continuous bending until fragmentation of the secondary dendritic arm induced by the stable oscillation bubble: (a) t = 0 ms; (b) t = 2.34 ms; (c) t = 4.68 ms; (d) t = 8.19 ms; (e) t = 9.36 ms; (f) t = 10.11 ms.
图 6 稳态空化气泡对枝晶臂弯曲角度及内部应力-应变影响 (a) 二次枝晶臂弯曲角度随时间的变化规律; (b) 一个周期内初始半径为35 μm的气泡振荡过程中半径及压强随时间的变化; (c) 二次枝晶臂内部不同位置的应力分布
Fig. 6. Effect of a stable oscillation bubble on stress-strain distribution inside the secondary dendritic arm: (a) Bending angle of the secondary dendritic arm changing over time; (b) radius and pressure calculated by Rayleigh-Plesset equation in one period with an initial bubble radius of 35 μm; (c) stress distribution at different positions inside the secondary dendritic arm.
图 7 液-固界面处的游离碎片被邻近的稳态空化气泡吸引并形成球状晶的演化过程, 其中(a) t = 0 s, (b) t = 2.42 s, (c) t = 5.20 s, (d) t = 6.08 s, (e) t = 8.40 s; (f) 气泡振荡过程中半径及吸附层厚度随时间的变化规律
Fig. 7. Evolution process of the free fragments attracted by a neighboring stable bubble at liquid-solid interface with a transformation into spherical grains: (a)–(e) Images of real-time observation at t = (a) 0 s, (b) 2.42 s, (c) 5.20 s, (d) 6.08 s, (e) 8.40 s. (f) The bubble radius and adsorbed layer thickness over time.
图 8 气泡稳态振荡吸引枝晶碎片并形成球状晶的原理 (a) 超声波作用下气泡的稳态振荡过程; (b) 枝晶碎片被气泡吸引并形成球状晶的示意图
Fig. 8. Principle of dendritic fragments attracted to a stable cavitation bubble with transformation into spherical grains: (a) Linearly oscillation of a steady-state bubble under the ultrasonic wave; (b) dendritic fragments attracted to a bubble and transformed into spherical grains.
表 1 数值模拟中用到的物理量数值
Table 1. Values of parameters in numerical simulation.
物理量 数值 单位 气泡初始半径 R0 45 μm 液体介质密度 ρ0 970 [21] kg/m3 饱和蒸汽压 Pv 2330 [20] Pa 表面张力 σ 3.85×10–2 [21] N/m 液体介质黏度 μ 2.66×10–3 [21] Pa·s 液体介质静压力 P0 1.013×105 [20] Pa 声压幅值 Pa 6.59×104 Pa 超声频率 f 20 kHz 气体比热系数 γ 1.4 [20] / 液体介质声速 c0 1500 [4] m/s 液体介质熔点 TL 316 K 凝固潜热 ∆Hf 3700 [23] J/mol 体积变化 ∆V 2.23×10–6 [22] m3/mol 熔化熵 ∆S 11.67 [23] J/(m–3·K–1) 液相比热容 Cp 188.1 [22] J/(mol–1·K–1) 热扩散系数 DT 1.134×10–7 [22] m2/s 平衡液相线斜率 m 1.42 K/at.% 溶质浓度 C0 8.3 at.% 溶质分配系数 ke 0.65 [24] / 溶质扩散系数 DL 8.33×10–10 [25] m2/s 液-固界面能 σSL 8.94×10–3 [22] J/m2 Gibbs-Thomson系数 Γ 6×10–8 m·K 
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[1] Eskin G I, Eskin D G 2014 Ultrasonic Treatment of Light Alloy Melts (2nd Ed.) (London: CRC Press) pp32–43
[2] Hu Y J, Wang X, Wang J Y, Zhai W, Wei B 2021 Metall. Mater. Trans. A 52 3097
Google Scholar
[3] Feng X H, Zhao F Z, Jia H M, Zhou J X, Li Y D, Li W R, Yang Y S 2017 Int. J. Cast Metal. Res. 30 341
Google Scholar
[4] Yasui K 2018 Acoustic cavitation and bubble dynamics (Switzerland: Springer International) pp14, 15
[5] Gielen B, Jordens J, Janssen J, Pfeiffer H, Wevers M, Thomassen L C J, Braeken L, Van Gerven T 2015 Ultrason. Sonochem. 25 31
Google Scholar
[6] 吴文华, 翟薇, 胡海豹, 魏炳波 2017 66 194303
Google Scholar
Wu W H, Zhai W, Hu H B, Wei B B 2017 Acta Phys. Sin. 66 194303
Google Scholar
[7] Koukouvinis P, Gavaises M, Supponen O, Farhat M 2016 Phys. Fluids 28 052103
Google Scholar
[8] Feng X H, Zhao F Z, Jia H M, Li Y J, Yang Y S 2018 Ultrason. Sonochem. 40 113
Google Scholar
[9] Chow R, Blindt R, Chivers R, Povey M 2005 Ultrasonics 43 227
Google Scholar
[10] Zhao Y, Zheng Q L, Liu Z W 2020 Mater. Lett. 274 128030
Google Scholar
[11] Shu D, Sun B D, Mi J W, Grant P S 2012 Metall. Mater. Trans. A 43 3755
Google Scholar
[12] Tan D Y, Mi J W 2013 Mater. Sci. Forum 765 230
Google Scholar
[13] Wang F, Eskin D, Mi J W, Wang C N, Koe B, King Andrew, Reinhard C, Connolley T 2017 Acta Mater. 141 142
Google Scholar
[14] Wang B, Tan D Y, Lee T L, Khong J C, Wang F, Eskin D, Connolley T, Fezzaa K, Mi J W 2018 Acta Mater. 144 505
Google Scholar
[15] Todaro C J, Easton M A, Qiu D, Zhang D, Bermingharm M J, Lui E W, Brandt M, Stjohn D H, Qian M 2020 Nat. Commun. 11 142
Google Scholar
[16] 徐珂, 许龙, 周光平 2021 70 194301
Google Scholar
Xu K, Xu L, Zhou G P 2021 Acta Phys. Sin. 70 194301
Google Scholar
[17] Omoteso K A, Roy-Layinde T O, Laoye J A, Vincent U E, McClintock P V E 2021 Ultrason. Sonochem. 70 105346
Google Scholar
[18] Lofstedt R, Barber B P, Putterman S J 1993 Phys. Fluids A 5 2911
Google Scholar
[19] Lin H, Storey B D, Szeri A J, Andrew J S 2002 J. Fluid Mech. 452 145
Google Scholar
[20] Murakami K, Yamakawa Y, Zhao J Y, Johnsen E, Ando K 2021 J. Fluid Mech. 924 A38
Google Scholar
[21] Wang S, Guo Z P, Zhang X P, Zhang A, Kang J W 2019 Ultrason. Sonochem. 51 160
Google Scholar
[22] Koss M B, LaCombe J C, Tennenhouse L A, Glicksman M E, Winsa E A 1999 Metall. Mater. Trans. A 30 3177
Google Scholar
[23] Shang S, Han Z Q 2019 J. Mater. Sci. 54 3111
Google Scholar
[24] Cattaneo C A, Evequoz O P E, Bertorello H R 1994 Scripta Metall. Mater. 31 461
Google Scholar
[25] Cain J B, Clunie J C, Baird J K 1995 Int. J. Thermophys. 16 1225
Google Scholar
[26] 高学鹏, 李新涛, 郄喜望, 吴亚萍, 李喜孟, 李廷举 2007 56 1188
Google Scholar
Gao X P, Li X T, Qie X W, Wu Y P, Li X M, Li T J 2007 Acta Phys. Sin. 56 1188
Google Scholar
[27] Trivedi R, Lipton J, Kurz W 1987 Acta Metall. 35 965
Google Scholar
[28] Lipton J, Kurz W, Trivedi R 1987 Acta Metall. 35 957
Google Scholar
[29] Longuet-Higgins M S 1998 P. Roy. Soc. A-Math. Phy. 454 725
Google Scholar
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