A phase-field study on the peritectic phase transition in Fe-C alloys
A phase-field study on the peritectic phase transition in Fe-C alloys
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DOI：
10.1016/j.actamat.2017.04.053
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发表时间：
2017-06
期刊：
影响因子：
9.4
通讯作者：
S. Pan;M. Zhu;M. Rettenmayr
中科院分区：
文献类型：
--
作者：
S. Pan;M. Zhu;M. Rettenmayr
本文提出了一个定量的多相场模型，该模型考虑了反俘获电流和固体中的扩散作用，模拟了Fe-C合金的相变。采用新定义的阶跃函数的界面场法，建立了多相场变量的控制方程。所提出的模型被应用于模拟的γ-片晶尖端生长在周晶反应和随后的周晶转变（γ-片晶厚度增长）在大的计算域的实验长度尺度。发现三相点处的局部液相浓度L/δ/γ略高于与δ相平衡时的液相浓度，但低于与γ相平衡时的液相浓度。这导致在三接点附近的δ相轻微熔化，而γ-血小板生长继续。在较高的过冷度下，较高的尖端速度产生沿γ片晶厚度方向的较陡的碳浓度梯度，从而产生较高的厚度生长速度。研究还发现，随着过冷度的增加，γ-片晶的生长速率与厚度的比值增加，导致尖端半径和片晶厚度减小。模拟结果与文献报道的实验数据吻合良好，证明了所建模型的定量预测能力，并证实了在接近平衡条件下，扩散控制对相变的控制作用.
A quantitative multi-phase-field model, with an anti-trapping current and involving diffusion in the solid, is proposed to simulate the peritectic phase transition in Fe-C alloys. An interface field method with a newly defined step function is adopted to formulate the governing equation of the multi-phase-field variables. The proposed model is applied to simulate theγ-platelet tip growth during the peritectic reaction and the subsequent peritectic transformation (γ-platelet thickness growth) in large computational domains of the experimental length scale. It is found that the local liquid concentration at the triple junction pointL/δ/γis slightly higher than the liquid concentration in equilibrium with theδ-phase, but lower than the liquid concentration in equilibrium with theγ-phase. This leads to slight melting of theδ-phase in the vicinity of the triple junction, while theγ-platelet growth continues. Higher tip velocities at higher undercoolings produce a steeper carbon concentration gradient along theγ-platelet's thickness direction, and thus yield a higher thickness growth velocity. It is also found that the ratio of tip and thickness growth velocity of theγ-platelets increases at higher undercoolings, leading to decreasing tip radius and platelet thickness. Good agreement between the simulations and the experimental data reported in literature is achieved, demonstrating the quantitative prediction capabilities of the proposed model, and confirming the diffusion control for the peritectic phase transition close to equilibrium conditions.