基于三维LBM-CA模型模拟Al-4.7%Cu合金的枝晶形貌和成分分布

发布时间：2018-05-18 02:14

本文选题：数值模拟 + 枝晶生长　；参考：《材料导报》2017年20期

【摘要】：建立了三维格子玻尔兹曼方法(LBM)-元胞自动机(CA)耦合数值模型,并用该模型模拟研究了Al-4.7%Cu(质量分数)固溶体合金的凝固过程。该耦合模型采用元胞自动机方法模拟枝晶的生长,同时采用基于分子动力学理论的格子玻尔兹曼方法模拟合金凝固过程中的温度场、流场以及溶质场。模拟结果再现了合金凝固过程中的三维枝晶形貌变化以及溶质富集过程,并将三维流场因素考虑进去,定量研究了自然对流、过冷度对单枝晶形貌和成分分布的影响。研究表明,在纯扩散条件下,枝晶呈现对称的生长现象,模拟自由枝晶稳态生长的尖端速度、尖端半径和过冷度的关系与Lipton-Glicksman-Kurz(LGK)理论模型吻合得较好。在自然对流条件下,枝晶的生长形貌呈现不对称性,即枝晶生长在迎流方向上得到了促进,在顺流方向上受到了抑制。熔体过冷度对枝晶生长的影响较大,过冷度的增加导致枝晶生长加快,二次枝晶增多且呈现出粗化现象,枝晶尖端固液界面处的溶质浓度偏高,加重了溶质偏析。
[Abstract]:A three dimensional lattice Boltzmann method coupled with LBMG-Cellular Automata (CAA) was established and the solidification process of Al-4.7Cu (mass fraction) solid solution alloy was simulated by the model. The coupling model uses cellular automata to simulate dendritic growth, and lattice Boltzmann method based on molecular dynamics theory to simulate the temperature field, flow field and solute field during solidification. The simulation results show that the three-dimensional dendritic morphology and solute enrichment process are reproduced during solidification, and the effects of natural convection and undercooling on the morphology and composition distribution of single branches are quantitatively studied by taking into account the three-dimensional flow field factors. The results show that the dendrite grows symmetrically under pure diffusion condition, and the relationship between the tip velocity, tip radius and undercooling of the steady state growth of free dendrite is in good agreement with the Lipton-Glicksman-Kurzman LGK model. Under the natural convection condition, the morphology of the dendrite is asymmetrical, that is, the dendritic growth is promoted in the direction of welcome flow and restrained in the direction of downstream flow. The effect of melt undercooling on dendritic growth is great. The increase of undercooling leads to the increase of dendritic growth, the increase of secondary dendrite and the coarsening of secondary dendrite. The solute concentration at the solid-liquid interface at the tip of dendrite is higher than that at the tip of dendrite, which exacerbates the solute segregation.
【作者单位】：河北工业大学材料科学与工程学院;
【基金】：国家自然科学基金(51475138)
【分类号】：TG146.21

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