【作者】 季波；

【导师】 沈寅忠；

【作者基本信息】 上海交通大学 ， 核能与核技术工程， 2013， 硕士

【摘要】 第四代反应堆系统具有高温、强辐射、强腐蚀的极端工况，现有水冷堆燃料包壳材料锆合金在这样的工况下，其力学性能、抗中子辐照能力和化学性能已经无法满足第四代反应堆对包壳及堆芯材料的性能要求。发展第四代反应堆，首先面临的严重挑战就是燃料包壳及堆芯结构材料。9-12%铬铁素体/马氏体钢具有优良的综合性能：良好的导热性能；较小的热膨胀系数；优良的高温（400-550oC）抗辐照能力；良好的耐高温腐蚀性能；较好的高温强度和蠕变持久强度；较好的经济性。因此，9-12%铬铁素体/马氏体钢成为第四代反应堆燃料包壳及堆芯结构的候选材料。本论文借助于光学显微镜、扫描电镜、透射电镜，研究了新型11Cr铁素体/马氏体钢高温蠕变前后的微观组织，同时利用高温拉伸试验机，并结合位错相关理论，研究了新型11Cr铁素体/马氏体钢的力学性能及应力锯齿流动行为的微观机理。微观组织分析结果表明,蠕变前后11Cr铁素体/马氏体钢组织主要为马氏体，也有少量δ-铁素体。蠕变前11Cr铁素体/马氏体钢主要存在两种析出相，分别为富Nb的MX相和富Cr的M23C6相。蠕变后部分MX相的化学成分发生三点明显的变化:Nb元素少量下降，其它金属元素少量增加；Nb元素较大下降，而Ta和W元素较大增加,变成富Ta的MX相；Nb元素较大下降，而Cr和V元素较大增加。蠕变后M23C6相化学成分基本没有变化，但析出量增加，且颗粒尺寸变大。11Cr铁素体/马氏体钢经高温蠕变后，在δ-铁素体中有Laves相或者Fe₃W₃C相析出。首次在正火回火态高Cr铁素体/马氏体钢中发现长片状可能为M₅C₂的富Fe、Cr相，经高温蠕变后该相消失。拉伸实验结果表明：11Cr铁素体/马氏体钢在600℃、625℃和650℃拉伸条件时，随着应变速率的降低，应力锯齿流动越来越明显，但在700℃时，应力锯齿流动随着应变速率的降低基本没有变化。11Cr铁素体/马氏体钢拉伸中出现的应力锯齿流动属于反常应力锯齿流动，且产生应力锯齿流动的激活能约为43KJ/mol。可能是间隙原子C或N通过位错管扩散与运动位错发生交互作用，引起动态应变时效，从而导致应力锯齿流动现象的产生。更多还原

【Abstract】 Reactors of Generation Ⅳ have extreme working conditions of hightemperature、tense radiation and strong corrosion, in such conditionsmechanical property、anti-irradiation property and chemical property ofthe existing fuel cladding material Zr alloy of water cooled reacter can’tmeet the need of reactors of Generation Ⅳ. The first serious challengecome from fuel cladding and core structural materials for thedevelopment of reactors of Generation Ⅳ.9%-12%Cr ferrite/martensitesteel possesses excellent comprehensive properties: good thermalconductivity; small coefficient of thermal expansion; excellentanti-irradiation property in high temperature（400-550oC）; goodresistance to high temperature corrosion; good high temperature strengthand creep strength; good economy. Therefore,9%-12%Crferrite/martensite steel has become one candidate material of reactor fuelcladding and core structural materials.Microstructure of11Cr ferritic/martensitic steel before and after high temperature creep was investigated using optical microscope、scanning electron microscope and transmission electron microscope, andmeanwhile mechanical property and microcosmic mechanism of serratedflow of11Cr ferritic/martensitic steel were investigated using hightemperature tensile testing machine with relevant dislocation theory.Experimental results of microstructure show that11Crferritic/martensitic steel before and after creep consists of martensite anda little δ-ferrite.11Cr ferritic/martensitic steel before creep contains twokinds of precipitate phases, which are Nb-rich MX phase and Cr-richM₂₃C₆phase. Some of MX phase appear three obvious changes aftercreep: Nb decreases slightly and other metallic elements increase slightly;Nb decreases obviously，while Ta and W increase obviously, changinginto Ta-rich MX phase; Nb decreases obviously，while Cr and V increaseobviously. Chemical composition of M23C6phase does not on the wholechange, meanwhile the amount and the size of the M₂₃C₆phase increaseafter creep. Laves phase or Fe3W3C phase is precipitated in δ-ferrite afterhigh temperature creep. A kind of long flaky precipitated phase whichmay be Fe-Cr-rich M₅C₂phase is found in normalized and tempered highCr ferritic/martensitic steel for the first time, and the phase disappearsafter high temperature creep.Tensile test results show that the serrated flow becomes moreobvious when the strain rate becomes lower when11Cr ferritic/martensitic steel is stretched at600℃、625℃and650℃, but at700℃the serrated flow don t change basically when the strain ratebecomes lower. The serrated flow in tensile of11Cr ferritic/martensiticsteel belongs to abnormal serrated flow and effective activation energyfor its generation is about43KJ/mol. The serrated flow is generated dueto the dynamic strain aging which may be caused by the interactionbetween interstitial atom C or N diffusing by dislocation pipe anddislocations.更多还原