Mn含量对Fe-Cu-Mn合金纳米富Cu析出相影响的相场法研究  

Effect of Mn Composition on the Nanometer Cu-Rich Phase of Fe-Cu-Mn Alloy by Phase Field Method

作　　者：赵宝军 赵宇宏[1] 孙远洋[1] 杨文奎 侯华[1] ZHAO Baojun;ZHAO Yuhong;SUN Yuanyang;YANG Wenkui;HOU Hua(School of Materials Science and Engineering,North University of China,Taiyuan 030051,China)

机构地区：[1]中北大学材料科学与工程学院

出　　处：《金属学报》2019年第5期593-600,共8页Acta Metallurgica Sinica

基　　金：国家自然科学基金项目Nos.U1610123;51674226;51574206;51774254和51701187;山西省科技重点项目No.MC2016-06~~

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。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.

关 键 词：Fe-Cu系合金 纳米富Cu相 RPV钢 相场模型 失稳分解 

分 类 号：TG292[金属学及工艺—铸造]