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金属学报  2019, Vol. 55 Issue (5): 593-600    DOI: 10.11900/0412.1961.2018.00506
  本期目录 | 过刊浏览 |
Mn含量对Fe-Cu-Mn合金纳米富Cu析出相影响的相场法研究
赵宝军,赵宇宏(),孙远洋,杨文奎,侯华
1. 中北大学材料科学与工程学院 太原 030051
Effect of Mn Composition on the Nanometer Cu-Rich Phase of Fe-Cu-Mn Alloy by Phase Field Method
Baojun ZHAO,Yuhong ZHAO(),Yuanyang SUN,Wenkui YANG,Hua HOU
1. School of Materials Science and Engineering, North University of China, Taiyuan 030051, China
引用本文:

赵宝军,赵宇宏,孙远洋,杨文奎,侯华. Mn含量对Fe-Cu-Mn合金纳米富Cu析出相影响的相场法研究[J]. 金属学报, 2019, 55(5): 593-600.
Baojun ZHAO, Yuhong ZHAO, Yuanyang SUN, Wenkui YANG, Hua HOU. Effect of Mn Composition on the Nanometer Cu-Rich Phase of Fe-Cu-Mn Alloy by Phase Field Method[J]. Acta Metall Sin, 2019, 55(5): 593-600.

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摘要: 

采用相场法模拟了Fe-Cu-Mn合金在823 K时效时富Cu析出相的三维组织演化图像、体积分数、数量密度和平均颗粒半径随时效时间的变化等。相场模拟研究表明:相分离早期阶段通过失稳分解机制形成富Cu相;同时Mn原子也在富Cu相的中心发生偏聚,在富Cu相开始Ostwald粗化的过程中,Mn原子又从其核心处偏聚到富Cu相和基体的界面处,最终在富Cu相外部形成富Mn环。富Mn环的存在会抑制富Cu相的扩散长大和粗化;富Cu相在时效前期是球状的bcc结构,随着不断长大,转变为椭球形或棒状的fcc结构;提高Mn含量可以加快富Cu相的析出,有利于富Cu相的粗化。

关键词 Fe-Cu系合金纳米富Cu相RPV钢相场模型失稳分解    
Abstract

The precipitation of nanometer Cu-rich phase can be observed in Fe-Cu alloy systems during isothermal ageing. The existence of Cu-rich phase is one of the reasons for the embrittlement of reactor pressure vessel (RPV) steel. The phase-field method applies a set of field variables defined by functions of space and time to describe the temporal evolution of composition and structural parameter, characterizing microstructure evolution during phase transformation. This work uses phase-field model to simulate the three-dimensional morphology, the volume fraction, number density and average particle radius of Cu-rich phase in Fe-Cu-Mn alloy at 823 K. The chemical free energy is derived from the thermodynamic database of the calculated phase diagram (CALPHAD), so the microstructure evolution of precipitation changes are directly corresponded to phase diagram of the real alloy system. The simulation results show that nanometer Cu-rich phase are formed by the spinodal decomposition mechanism in the early stage of phase separation. Meanwhile, Mn atoms segregate to the center of the Cu-rich phase. During the process of Ostwald coarsening, Mn atoms migrate from core to the interface of Cu-rich phase, finally forming Mn-rich ring distributed in the exterior of Cu-rich phase. Its existence can decrease the rates of diffusion growth and coarsening of Cu-rich phase. The Cu-rich phase is bcc structure and disperses in the matrix with spherical shape in the early stage of ageing. As the Cu-rich phase continues to grow, it will transform into fcc structure with ellipsoid or rod shapes. Meanwhile, increasing Mn content of Fe-Cu-Mn alloy accelerates the precipitation of Cu-rich phase and facilitates the growth and coarsening of Cu-rich phase.

Key wordsFe-Cu alloy system    nanometer Cu-rich phase    RPV steel    phase-field simulation    spinodal decomposition
收稿日期: 2018-11-07     
ZTFLH:  TG292  
基金资助:国家自然科学基金项目(U1610123);国家自然科学基金项目(51674226);国家自然科学基金项目(51574206);国家自然科学基金项目(51774254);国家自然科学基金项目(51701187);山西省科技重点项目(MC2016-06)
作者简介: 赵宝军,男,1992年生,硕士生
ParameterValueUnit
kc,kηkc=5.0×10-15,kη=1.0×10-15J·m2·mol-1
Vm7.09×10-6m3·mol-1
T823K
Y214GPa
Lx×Ly×Lz32×32×32nm3
SiSCu=3.29×10-2,SMn=5.22×10-4
W5.0×103J·mol-1

Di0,φφ=α,γ

DCu0,α=4.7×10-5,DCu0,γ=4.3×10-5

DMn0,α=1.49×10-4, DMn0,γ=1.78×10-5

m2·s-1

Qi0,φφ=α,γ

QCu0,α=2.44×105, QCu0,γ=2.80×105

QMn0,α=2.33×10-5, QMn0,γ=2.64×105

J·mol-1

表1  相场模拟中所使用的参数值[31]
图1  时效温度为823 K时Fe-Cu-Mn合金中Mn含量分别为1%、3%和5%条件下时效不同时间对应的三维富Cu相演化图
图2  时效温度为823 K时Fe-Cu-Mn合金中Mn含量分别为1%、3%和5%条件下时效t*=3000时指定水平直线上对应的Cu和Mn的浓度分布曲线
图3  时效温度为823 K时Fe-Cu-Mn合金中Mn含量分别为1%和5%条件下时效不同时间时指定水平线上对应的Cu析出相的浓度分布曲线
图4  时效温度为823 K时Fe-Cu-Mn合金中Mn含量分别为1%、3%和5%条件下时效不同时间时指定水平线上对应的富Cu相结构序参数
图5  时效温度为823 K时,Fe-Cu-Mn合金中Mn含量分别为1%、3%和5%条件下,纳米富Cu相体积分数随时间的变化
图6  时效温度为823 K时,Fe-Cu-Mn合金中Mn含量分别为1%、3%和5%条件下,纳米富Cu相数量密度随时间的变化
图7  时效温度为823 K时,Fe-Cu-Mn合金中Mn含量分别为1%、3%和5%条件下,纳米富Cu相数量密度随时间的变化
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