Quantitative modeling and experimental verification of carbide precipitation in a martensitic Fe-0.16 wt%C-4.0 wt%Cr alloy
Quantitative modeling and experimental verification of carbide precipitation in a martensitic Fe-0.16 wt%C-4.0 wt%Cr alloy
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DOI：
10.1016/j.calphad.2016.03.001
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发表时间：
2016-06-01
影响因子：
2.4
通讯作者：
Odqvist, Joakim
中科院分区：
文献类型：
--
作者：
Hou, Ziyong;Hedstrom, Peter;Odqvist, Joakim
通过实验分析和定量模拟研究了马氏体Fe-0.16 wt% C-4.0 wt% Cr合金回火过程中碳化物的析出。在700℃回火过程中，M7C3和M23C6在马氏体的低角和高角晶界以及马氏体单个板条内的位错处形成。应用Kampmann-Wagner数值（KWN）模型，利用CALPHAD热力学和动力学数据库，结合局部平衡和恒定系线的假设，捕捉了沉淀的主要特征：亚稳M23C6的瞬时形成；以M7C3为稳定碳化物。预测的体积分数和粒径与M7C3的萃取实验结果吻合较好。然而，对于亚稳少数碳化物M23C6，模型低估了尺寸，高估了瞬态时间内的体积分数。采用的简化建模方案具有完善的热力学数据库和物理参数输入，是材料设计和优化的宝贵工具。此外，通过更严格地处理相界面的条件，可以解释不同的沉淀机制，例如，非分配局部平衡，这在间隙元素扩散速度比替代元素快得多的系统中可能很重要。(C) 2016 Elsevier Ltd.版权所有。
Precipitation of carbides during tempering of a martensitic Fe-0.16 wt% C-4.0 wt% Cr alloy has been investigated by experimental analysis and quantitative modeling. It is found that both M7C3 and M23C6 form, at low- and high-angle grain boundaries in the martensite, as well as, at dislocations inside individual laths of martensite, during tempering at 700 degrees C. The applied Kampmann-Wagner numerical (KWN) modeling, utilizing CALPHAD thermodynamic and kinetic databases together with an assumption of local equilibrium and a constant tie-line, captures the main features of the precipitation, with a transient formation of metastable M23C6, and with M7C3 as the stable carbide. The predicted volume fraction and size are in reasonable agreement with extraction experiments for M7C3. However, for the metastable minority carbide M23C6, the modeling underestimates the size and overestimates the volume fraction within the transient time. With sound thermodynamic databases and physical parameter input, the adopted simplified modeling scheme is a valuable tool for materials design and optimization. Furthermore, by treating conditions at the phase interface more rigorously it is possible to account for different mechanisms of precipitation, such as e.g., non-partitioning local equilibrium, which could be important in systems where interstitial elements diffuse much faster than the substitutional ones. (C) 2016 Elsevier Ltd. All rights reserved.