Ghosh Supriyo, Ma Li, Ofori-Opoku Nana, Guyer Jonathan E
Materials Science and Engineering Division, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA.
Theiss Research, La Jolla, CA 92037, USA.
Model Simul Mat Sci Eng. 2017;25(6). doi: 10.1088/1361-651x/aa7369.
In this study, an alloy phase-field model is used to simulate solidification microstructures at different locations within a solidified molten pool. The temperature gradient and the solidification velocity are obtained from a macroscopic heat transfer finite element simulation and provided as input to the phase-field model. The effects of laser beam speed and the location within the melt pool on the primary arm spacing and on the extent of Nb partitioning at the cell tips are investigated. Simulated steady-state primary spacings are compared with power law and geometrical models. Cell tip compositions are compared to a dendrite growth model. The extent of non-equilibrium interface partitioning of the phase-field model is investigated. Although the phase-field model has an anti-trapping solute flux term meant to maintain local interface equilibrium, we have found that during simulations it was insufficient at maintaining equilibrium. This is due to the fact that the additive manufacturing solidification conditions fall well outside the allowed limits of this flux term.
在本研究中，采用合金相场模型来模拟凝固熔池内不同位置的凝固微观组织。温度梯度和凝固速度通过宏观传热有限元模拟获得，并作为相场模型的输入。研究了激光束速度和熔池内位置对一次枝晶间距以及Nb在胞状晶尖端偏析程度的影响。将模拟的稳态一次间距与幂律模型和几何模型进行比较。将胞状晶尖端成分与枝晶生长模型进行比较。研究了相场模型的非平衡界面偏析程度。尽管相场模型有一个旨在维持局部界面平衡的抗俘获溶质通量项，但我们发现在模拟过程中，它在维持平衡方面并不充分。这是因为增材制造的凝固条件远远超出了该通量项的允许极限。
