Solidification and phase formation of alloys in the hypoeutectic region of the Fe-C-B system
Solidification and phase formation of alloys in the hypoeutectic region of the Fe-C-B system
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DOI：
10.1016/j.actamat.2015.07.037
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发表时间：
2015-10-15
期刊：
影响因子：
9.4
通讯作者：
Theisen, Werner
中科院分区：
文献类型：
--
作者：
Lentz, Jonathan;Roettger, Arne;Theisen, Werner
在这项工作中，研究了来自铁-碳-硼（Fe-C-B）系统亚共晶富铁区域的合金的凝固和相形成。制造了碳含量恒定为 0.6 质量%、硼含量为 0.2 质量%、0.6 质量% 和 1.8 质量% 的实验室熔体，并进行了金相检查。此外，通过 CALPHAD 方法在平衡状态下研究微观结构，并通过多相场 (MPF) 方法来重现技术凝固的非平衡过程。分析了硼对凝固路径、显微结构结晶过程以及凝固相的形态和化学特征的影响。所研究的合金经历了奥氏体（γ-Fe）的初次结晶。由于B在初生相γ-Fe中的溶解度较低，B在熔体中强烈偏析，凝固路径偏向高B含量。因此，随着B含量的增加，共晶凝固顺序从富B的Fe2B相开始，并在后一个过程中继续形成富B的Fe-3(B,C)相。因此，在共晶反应过程中，熔体的 B 含量降低，并且共晶 Fe-3(B,C) 相在生长方向上表现出递减的 B 梯度。因此，Fe-C-B 体系的低熔点相是 Fe-3(B,C) 相，其 B 含量较低，其成分最接近其低熔点 B 含量 14.10 at.% B。合金成分中 B/(C + B) 比率的增加会提高 Fe-3(B,C) 相的平均 B 含量（高达 >20 at.% B），因此同时会增加合金的固相线温度。这些发现与化学成分 (WDX)、相分析（同步辐射衍射，EBSD）和热分析 (DTA) 的实验结果一致。 (C) 2015 年由 Elsevier Ltd. 代表 Acta Materialia Inc. 发布。
In this work, alloys from the hypoeutectic iron-rich region of the iron-carbon-boron (Fe-C-B) system were investigated with respect to the solidification and the phase formation. Laboratory melts with a constant carbon content of 0.6 mass% and boron contents of 0.2 mass%, 0.6 mass%, and 1.8 mass% were fabricated and metallographically examined. In addition the microstructures were investigated by CALPHAD method in the state of equilibrium and by multiphase-field (MPF) method to reproduce the non-equilibrium process of the technical solidification. The results were analyzed with respect to the effect of boron on the solidification paths, microstructural crystallization processes as well as the morphological and chemical characteristics of the solidified phases.The investigated alloys undergo primary crystallization of austenite (gamma-Fe). Due to the low solubility of B in the primary phase gamma-Fe, B is strongly segregated in the melt and the solidification paths are deviated to high B contents. Therefore, as the B content increases, the eutectic solidification sequence starts with the B-rich Fe2B phase and continues with the formation of the B-rich Fe-3(B,C) phase in the latter process. The B content of the melt thus decreases during the eutectic reaction, and the eutectic Fe-3(B,C) phase exhibits a decreasing B gradient in the direction of growth. Consequently, the low-melting phase of the Fe-C-B system is the Fe-3(B,C) phase with a low B content and a composition closest to its low-melting B content of 14.10 at.% B. Increasing B/(C + B) ratios of the alloy composition raise the average B content of the Fe-3(B,C) phase (up to >20 at.% B) and hence at the same time increase the solidus temperature of the alloy. These findings revealed consistency with experimental results for chemical composition (WDX), phase analysis (diffraction with synchrotron radiation, EBSD), and thermal analysis (DTA). (C) 2015 Published by Elsevier Ltd. on behalf of Acta Materialia Inc.