耦合热力学相变路径预测Fe-C包晶合金宏观偏析  

Prediction of Macrosegregation of Fe-C Peritectic Alloy Ingot Through Coupling with Thermodynamic Phase Transformation Path

作　　者：冯苗苗 张红伟[1,2] 邵景霞 李铁 雷洪 王强[1,2] FENG Miaomiao;ZHANG Hongwei;SHAO Jingxia;LI Tie;LEI Hong;WANG Qiang(Key Laboratory of Electromagnetic Processing of Materials,Ministry of Education,Northeastern University,Shenyang 110819,China;School of Metallurgy,Northeastern University,Shenyang 110819,China)

机构地区：[1]东北大学材料电磁过程研究教育部重点实验室,沈阳110819 [2]东北大学冶金学院,沈阳110819

出　　处：《金属学报》2021年第8期1057-1072,共16页Acta Metallurgica Sinica

基　　金：国家自然科学基金项目Nos.51574074、51425401;国家自然科学基金钢铁联合研究基金项目Nos.U1460108、U1560207;辽宁省教育厅基金项目No.L20150183。

摘　　要：针对Fe-0.1%C(质量分数)包晶合金冷却过程中多固相共存及界面分配系数实时变化的情况,由杠杆定律结合热力学平衡计算(LR-TEC)获得合金由液相冷却至室温的相变路径,制成相变路径数据表,由成分与热焓线性插值获得相应温度、相质量分数、相成分和相焓,以及凝固潜热释放量和比热容随多固相析出以及成分和温度的变化关系,与连续介质宏观传输模型相结合,预测了铸锭宏观偏析形成过程。模型采用经典的Sn-5%Pb合金凝固基准实验进行了验证。在随温度和溶质成分即时变化的分配系数及多固相的影响下,预测的Fe-0.1%C合金截面偏析变得更为严重。计算结束时,采用LR-TEC耦合宏观传输预测的最大负偏析在距铸锭左侧x=16 mm、距底面y=45 mm处,偏析率为-2.22%;而杠杆定律解析式(LR Analytical)预测的最大负偏析位于y=55 mm左侧壁面处,偏析率为-1.78%。2者预测的最大正偏析都位于铸锭右侧贴壁区域,合金冷却过程中的相变路径采用LR-TEC比LR Analytical预测的偏析率大1.13%。凝固计算结束时区域内仍多固相共存,其中α、γ两固相,α、渗碳体(CEM)两固相及α、γ、CEM三固相分别共存于铸锭左侧x<0.0342 m的低温区域,δ、γ两固相共存于区域右侧x>0.0858 m的高温区域。The phase transformation path is vital to enclosing the macroscopic transport equations for predicting alloy macrosegregation.However,the analytical approximations for micro-segregation,such as the lever rule(LR),are invalid because an actual alloy is a multi-component system with several coexisting solids.The LR only expresses the phase transformation between a single solid phase and a liquid phase and adopts a constant solute partition coefficient,which is insufficient for microsegregation.In this study,a model combining the thermodynamic phase transformation path calculation with the macroscopic transport was adopted to predict the macrosegregation formation in an Fe-0.1%C(mass fraction)peritectic alloy,which considers the coexistence of multi-solids and the variance of the local partition coefficient at the solid/liquid and solid/solid phase interface with a solidification process.The phase transformation path from the liquid state cooling to room temperature within a certain range of the solute concentrations was obtained using the LR approximation combined with the thermodynamic equilibrium calculation(LR-TEC).By tabulating the phase transformation path and interpolating the local concentration and enthalpy,the corresponding temperature,phase fraction,phase concentration,and phase enthalpy required in the continuum macroscopic transport model were achieved.The latent heat released and the specific heat corresponding to the amounts of the two solid phases at the peritectic or eutectic phase transformation zone were updated along with their dependence on the local concentration and temperature.This method was validated through the benchmark macrosegregation test of the binary Sn5%Pb alloy.Regarding the Fe-0.1%C alloy,the varied local partition coefficients and the other thermodynamic parameters with multi-solids precipitating during solidification resulted in a more severe macrosegregation profile in the ingot.At the end of the solidification calculation,the predicted minimum relative solute concentration for

关 键 词：Fe-0.1%C合金 宏观偏析 热力学相变路径 多固相 线性插值 

分 类 号：TG111.4[金属学及工艺—物理冶金]