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基于耦合流场的Wheeler模型,采用有限差分法,对纯镍单枝晶和多枝晶生长过程进行模拟,研究了强制对流对枝晶形貌、温度分布及枝晶臂尖端生长行为的影响。结果表明,在流速为14.76 m/s的垂直强制对流作用下,单枝晶生长时逆流枝晶臂生长迅速,其尖端稳态生长速度比纯扩散时增加了47.14%;顺流枝晶臂生长缓慢,其尖端稳态生长速度比纯扩散时减小了49.72%。模拟结果与Ivanstov理论及试验结果一致。多枝晶生长时,受强制流动、晶体结构特征和生长空间的共同作用,仅有指向逆流侧外部区域的优先生长方向上的枝晶臂生长受到促进,主枝和侧枝发达,其他优先生长方向的枝晶臂生长均受到抑制,主枝和侧枝退化。
Based on Wheeler model of coupled flow field, the growth process of single dendrites and dendrites in pure nickel was simulated by finite difference method. The effects of forced convection on dendrite morphology, temperature distribution and dendrite arm tip growth behavior were studied. The results show that the countercurrent dendrite arm grows rapidly when the single dendrite grows at the vertical forced convection velocity of 14.76 m / s, and the tip steady growth rate increases by 47.14% compared with pure diffusion. The dendrite arm growth Slow, its tip steady-state growth rate than the pure diffusion reduced by 49.72%. The simulation results are consistent with Ivanstov’s theory and experimental results. In the case of multidendritic growth, the dendrite growth in the preferential growth direction is promoted only by the forced flow, the crystal structure and the growth space. The main branch and the branch are developed, and other preferential growth directions Dendrite arm growth were inhibited, the main branch and collateral degeneration.