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.
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 316 Ti and 15-15 Ti,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 316 Ti and 15-15 Ti to LBE.However,as ferrite-forming elements,the influences of Cr and Si on the microstructural stability of 316 Ti and 15-15 Ti are still unclear.In this work,316 Ti-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 ofδ-phase.For alloy 18 Cr-2.0 Si-15 Ni,the maximum contents of Cr and Si are determined to be no more than 18.8%and 2.55%,respectively,which hindersδ-phase precipitation.In the ingot of 20 Cr-2.0 Si,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 18 Cr-2.5 Si,δ-phase precipitates between dendrites,with a volume fraction of 3.4%.Moreover,this work also evaluates two kinds of austenitic stainless steel solidification path criteria.
作者
易昊钰
陈思含
王旻
梁田
马颖澈
YI Hao-yu;CHEN Si-han;WANG Min;LIANG Tian;MA Ying-che(China Nuclear Power Technology Research Institute,Shenzhen 518000,China;CAS Key Laboratory of Nuclear Materials and Safety Assessment,Institute of Metal Research,Chinese Academy of Sciences,Shenyang 110016,China)
出处
《工程科学学报》
EI
CSCD
北大核心
2020年第2期179-185,共7页
Chinese Journal of Engineering
基金
辽宁省自然科学基金资助项目(2019-BS-248).
关键词
奥氏体不锈钢
热力学模拟
凝固组织
Δ相
硅元素
austenitic stainless steel
thermodynamic simulation
solidification microstructure
delta phase
silicon
