工程科学学报.第42卷，第2期：179-185.2020年2月 Chinese Journal of Engineering,Vol.42,No.2:179-185,February 2020 https://doi.org/10.13374/j.issn2095-9389.2019.02.24.003;http://cje.ustb.edu.cn C和Si元素对奥氏体不锈钢组织构成及凝固路线的影响 易昊钰，陈思含2》，王旻2)四，梁田，马颖澈2) 1)中广核研究院有限公司.深圳5180002)中国科学院金属研究所核用材料与安全评价重点实验室，沈阳110016 ☒通信作者，E-mail:minwang@imr.ac.cn 摘要以3I6Ti奥氏体不锈钢为基础，设计不同Cr和Si元素含量的合金成分，结合Thermal-.Calc热力学模拟计算与合金铸 锭凝固组织形貌、成分分析，研究了Cr和S元素对合金凝固组织构成的影响.研究结果表明，热力学计算能够获得奥氏体不 锈钢中析出δ相的临界Cr和Si含量.合金凝固时的元素偏析和冷却过程中的“δ→y”相变可对δ相析出预测产生一定影响. 此外，本工作还针对δ相析出评价了两种凝固路线判据. 关键词奥氏体不锈钢：热力学模拟：凝固组织：δ相：硅元素 分类号TG142.71 Effects of Cr and Si on the microstructure and solidification path of austenitic stainless steel YI Hao-yu,CHEN Si-han),WANG Min,LIANG Tian),MA Ying-che2 1)China Nuclear Power Technology Research Institute,Shenzhen 518000,China 2)CAS Key Laboratory of Nuclear Materials and Safety Assessment,Institute of Metal Research,Chinese Academy of Sciences,Shenyang 110016, China Corresponding author,E-mail:minwang @imr.ac.cn ABSTRACT The lead-cooled fast reactor(LFR),which features advanced technical maturity and enhanced safety,is an important part of the fourth-generation nuclear power system of China.The superior safety of the LFR results from the choice of a relatively inert coolant,the lead or lead-bismuth eutectic (LBE),which can be rather corrosive to common metallic structural materials.Furthermore, there is basically no cladding material available for the LFR.Austenitic stainless steels feature a combination of excellent corrosion resistance,proper strength,and good workability,and materials such as 316Ti and 15-15Ti,which have been used in the sodium-cooled fast reactor(SFR),are viewed as promising candidate materials for LFR cladding applications.Elements of Cr and Si have been found capable of improving the corrosion resistance of 316Ti and 15-15Ti to LBE.However,as ferrite-forming elements,the influences of Cr and Si on the microstructural stability of 316Ti and 15-15Ti are still unclear.In this work,316Ti-based materials with various Cr and Si contents were studied through thermodynamic simulation and microstructural characterization.Specifically,the equilibrium phase constitutions of the austenitic stainless steels were investigated by thermodynamic simulation using Thermo-Calc.The solidification microstructures and precipitates of Cr-and Si-bearing austenitic stainless steels were studied by optical microscopy (OM),scanning electronic microscopy (SEM),electronic differential system (EDS),and X-ray diffraction(XRD).The results show that Cr and Si can decrease the solidus and liquidus temperatures of alloys and induce the precipitation of 8-phase.For alloy 18Cr-2.0Si-15Ni,the maximum contents of Cr and Si are determined to be no more than 18.8%and 2.55%,respectively,which hinders 8-phase precipitation. In the ingot of 20Cr-2.0Si,8-phase is found to be located within dendrites in a skeleton morphology,with a volume fraction of 8.6%, whereas in the ingot of 18Cr-2.5Si,8-phase precipitates between dendrites,with a volume fraction of 3.4%.Moreover,this work also 收稿日期：2019-02-24 基金项目：辽宁省自然科学基金资助项目(2019-BS-248)Cr 和 Si 元素对奥氏体不锈钢组织构成及凝固路线的影响 易昊钰1)，陈思含2)，王    旻2) 苣，梁    田2)，马颖澈2) 1) 中广核研究院有限公司，深圳 518000    2) 中国科学院金属研究所核用材料与安全评价重点实验室，沈阳 110016 苣通信作者，E-mail：minwang@imr.ac.cn 摘    要    以 316Ti 奥氏体不锈钢为基础，设计不同 Cr 和 Si 元素含量的合金成分，结合 Thermal-Calc 热力学模拟计算与合金铸 锭凝固组织形貌、成分分析，研究了 Cr 和 Si 元素对合金凝固组织构成的影响. 研究结果表明，热力学计算能够获得奥氏体不 锈钢中析出 δ 相的临界 Cr 和 Si 含量. 合金凝固时的元素偏析和冷却过程中的“δ→γ”相变可对 δ 相析出预测产生一定影响. 此外，本工作还针对 δ 相析出评价了两种凝固路线判据. 关键词    奥氏体不锈钢；热力学模拟；凝固组织；δ 相；硅元素 分类号    TG142.71 Effects of Cr and Si on the microstructure and solidification path of austenitic stainless steel YI Hao-yu1) ，CHEN Si-han2) ，WANG Min2) 苣 ，LIANG Tian2) ，MA Ying-che2) 1) China Nuclear Power Technology Research Institute, Shenzhen 518000, China 2) CAS Key Laboratory of Nuclear Materials and Safety Assessment, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China 苣 Corresponding author, E-mail: minwang@imr.ac.cn ABSTRACT    The lead-cooled fast reactor (LFR), which features advanced technical maturity and enhanced safety, is an important part of  the  fourth-generation  nuclear  power  system  of  China.  The  superior  safety  of  the  LFR  results  from  the  choice  of  a  relatively  inert coolant, the lead or lead-bismuth eutectic (LBE), which can be rather corrosive to common metallic structural materials. Furthermore, there  is  basically  no  cladding  material  available  for  the  LFR.  Austenitic  stainless  steels  feature  a  combination  of  excellent  corrosion resistance, proper strength, and good workability, and materials such as 316Ti and 15-15Ti, which have been used in the sodium-cooled fast reactor (SFR), are viewed as promising candidate materials for LFR cladding applications. Elements of Cr and Si have been found capable of improving the corrosion resistance of 316Ti and 15-15Ti to LBE. However, as ferrite-forming elements, the influences of Cr and Si on the microstructural stability of 316Ti and 15-15Ti are still unclear. In this work, 316Ti-based materials with various Cr and Si contents  were  studied  through  thermodynamic  simulation  and  microstructural  characterization.  Specifically,  the  equilibrium  phase constitutions  of  the  austenitic  stainless  steels  were  investigated  by  thermodynamic  simulation  using  Thermo-Calc.  The  solidification microstructures  and  precipitates  of  Cr-  and  Si-bearing  austenitic  stainless  steels  were  studied  by  optical  microscopy  (OM),  scanning electronic microscopy (SEM), electronic differential system (EDS), and X-ray diffraction (XRD). The results show that Cr and Si can decrease  the  solidus  and  liquidus  temperatures  of  alloys  and  induce  the  precipitation  of  δ-phase.  For  alloy  18Cr−2.0Si−15Ni,  the maximum contents of Cr and Si are determined to be no more than 18.8% and 2.55%, respectively, which hinders δ-phase precipitation. In the ingot of 20Cr−2.0Si, δ-phase is found to be located within dendrites in a skeleton morphology, with a volume fraction of 8.6%, whereas in the ingot of 18Cr−2.5Si, δ-phase precipitates between dendrites, with a volume fraction of 3.4%. Moreover, this work also 收稿日期: 2019−02−24 基金项目: 辽宁省自然科学基金资助项目（2019-BS-248） 工程科学学报，第 42 卷，第 2 期：179−185，2020 年 2 月 Chinese Journal of Engineering, Vol. 42, No. 2: 179−185, February 2020 https://doi.org/10.13374/j.issn2095-9389.2019.02.24.003; http://cje.ustb.edu.cn