Modeling of convection, temperature distribution and dendritic growth in glass-fluxed nickel melts
Modeling of convection, temperature distribution and dendritic growth in glass-fluxed nickel melts
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DOI：
10.1016/j.jcrysgro.2016.11.069
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发表时间：
2017-08-01
影响因子：
1.8
通讯作者：
Alexandrov, Dmitri V.
中科院分区：
文献类型：
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作者：
Gao, Jianrong;Kao, Andrew;Alexandrov, Dmitri V.
熔体流动常被认为是低过冷时枝晶生长动力学实验与理论不一致的原因。但这种流动效应不适用于流场较弱的玻璃熔体。在本工作中，我们通过磁流体力学计算模拟了玻璃熔剂镍样品的热历史、流动模式和枝晶结构。首先，通过再现凝固前试样的热历史，模拟了熔融和过冷熔体中的温度分布和流动结构。然后对重熔样品的枝晶结构和表面温度进行了模拟。这些模拟揭示了穿过样品的大热梯度，这导致了对样品体积中枝晶生长的实际过冷程度的低估。考虑到这种低估，我们使用三维对流枝晶生长理论重新计算了玻璃熔剂镍熔体中的枝晶尖端速度，并得出了实验和理论之间的改进的一致性。
Melt flow is often quoted as the reason for a discrepancy between experiment and theory on dendritic growth kinetics at low undercoolings. But this flow effect is not justified for glass-fluxed melts where the flow field is weaker. In the present work, we modeled the thermal history, flow pattern and dendritic structure of a glass-fluxed nickel sample by magnetohydrodynamics calculations. First, the temperature distribution and flow structure in the molten and undercooled melt were simulated by reproducing the observed thermal history of the sample prior to solidification. Then the dendritic structure and surface temperature of the recalescing sample were simulated. These simulations revealed a large thermal gradient crossing the sample, which led to an underestimation of the real undercooling for dendritic growth in the bulk volume of the sample. By accounting for this underestimation, we recalculated the dendritic tip velocities in the glass-fluxed nickel melt using a theory of three-dimensional dendritic growth with convection and concluded an improved agreement between experiment and theory.