1Cr_(18)Nl_9Ti钢的低周疲劳特性研究

通过对:Cr_(18)Ni_9Ti钢的低周疲劳循环试验,进行了试验结果的回归分析研究,给出了轴向总应变与循环寿命,以及总应变与循环至发生工程裂纹寿命的关系。     

1Cr18Ni9Ti焊缝疲劳短裂纹的形态演化

试验研究了1Cr18Ni9Ti焊缝光滑试样的单轴疲劳短裂纹形态演化规律.基于"有效短裂纹准则",把注意力放在"主导有效短裂纹(DESFC)"萌生及裂尖前沿区域.观测发现,ESFCs萌生于焊缝局部delta铁素体与奥氏体基质界面,取向在与加载轴垂直截面小于45°随机分布.之后,受微观结构约束,表面倾向于沿垂直于轴向不规则扩展;深度方向,裂纹初始与加载方向垂直,之后倾向于与柱状晶生长方向垂直.当若干取向基本一致,裂尖前沿相邻的ESFCs发生合并即形成真实DESFC,由微观结构短裂纹(MSC)阶段进入物理短裂纹(PSC)阶段.PSC阶段,表面DESFC近似与轴向垂直,在微观结构干扰下不规则扩展;深度方向,逐步演变与柱状晶生长方向垂直,后期及长裂纹阶段倾向于与加载轴成45°.最后,试样沿与加载轴垂直方向瞬时断裂.这说明了疲劳短裂纹与长裂纹形态变化具有明显差异.     

Zr—4／1Cr18Ni9Ti爆炸焊结合层的显微组织研究

对Ｚｒ－４／１Ｃｒ１８Ｎｉ９Ｔｉ异种金属爆炸焊结合层显微组织及机械性能进行了研究。用透射电镜观察的结果表明，爆炸焊结合层是由熔化和热扩散共同作用的冶金结合，具有良好的机械性能。     

氢在TiC膜-1Cr18Ni9Ti不锈钢中的渗透行为

用离子束辅助沉积法在1Cr18Ni9Ti不锈钢表面制备了TiC膜,并对其进行了XPS,SEM及SIMS等微观结构分析,测定了氢在有TiC膜的1Cr18Ni9Ti不锈钢中的渗透率.研究结果表明,制备的TiC膜致密性好且均匀,厚度约为15 μm; TiC膜中有大量的CH-4负离子存在,在473～773 K范围内,氢的渗透率降低了4～5个数量级.     

1Cr18Ni9Ti焊缝的物理疲劳短裂纹扩展实验

应用复型技术研究了1Cr18Ni9Ti管道焊缝金属的物理疲劳短裂纹行为。结果表明,依照“有效短裂纹准则”,在物理短裂纹（PSC）阶段,主导有效短裂纹（DESFC）扩展和有效短裂纹（ESFCs）的扩展及合并对疲劳损伤做出直接贡献,在DESFC裂尖前沿区域的ESFCs密度通过影响DESFC扩展,对疲劳损伤做出问接贡献。DESFC受到减弱的微观结构条件影响,逐渐演化为单条长裂纹扩展行为。ESFCs密度在微观结构短裂纹（MSC）阶段反映DESFC萌生区域、在PSC阶段反映其裂尖前沿的微观结构扩展条件,其统计演化特征与DESFC扩展率的统计演化特征一致。这说明了这一微观结构扩展条件的差异和演化,是随机疲劳性能与演化特性的本质原因。疲劳损伤是一个由初始混沌状态演化到MSC与PSC两阶段交界处独立无关的随机状态,然后到史相关随机状态的过程。     

1Cr18Ni9Ti焊缝的疲劳短裂纹扩展方程

基于“有效短裂纹准则”,研究了1Cr18Ni9Ti焊缝的疲劳短裂纹行为描述方法。与疲劳群体短裂纹演化行为机制一致,考虑了3个重要因素。首先,主导有效短裂纹（DESFC）行为是群体短裂纹交互作用与影响的结果,因而适于表征短裂纹扩展行为。其次,显著的微观结构短裂纹（MSC）和物理短裂纹（PSC）两阶段行为特征,说明扩展律方程应当揭示这一现象。第三,强烈的不规则扩展行为,说明单一循环应变或应力参量不宜表征疲劳短裂纹扩展行为。因此,以DESFC局部萌生区域（MSC阶段）及其裂尖前沿区域（PSC阶段）的局部应变能密度为驱动力,发展了以包容上述区域的应变能密度为驱动力计算参数的新短裂纹扩展律,试验结果分析验证了方法的有效性。     

Fatigue-creep life prediction of Cr-1Mo steel under combined tension-torsion at 600°C

The results of fatigue-creep life prediction for Cr-1Mo steel under multiaxial stress conditions of combined tension-compression and cyclic torsion are summarized. This work was performed as the second task A-II of the cooperative project of phase 3 by the Subcommittee on Inelastic Analysis and Life Prediction of High Temperature Materials, JSMS. The ratios of axial to torsional strain range, Δε/Δ(γ/3^1/2), were set to be non-unity in these phase 3 tests for both in-phase and out-of-phase (with 90° phase difference) strain-controlled wave patterns, including pure torsion, while the ratios were unity in phase 2. By comparing the evaluated failure lives with the corresponding data of phase 2, some discussion on the effect of the wave patterns is presented and the validity of the life prediction methods is evaluated.     

1Cr18N19Ti钢在酸性高锰酸钾去污体系中的腐蚀行为研究

采用失重法、金相观察、电子扫描探针观测、电化学阻抗图谱测试等方法,研究了1Cr18Ni9Ti钢在不同浓度KMnO4+10%HNO3清洗条件下的腐蚀行为.结果表明,1Cr18Ni9Ti钢在该体系中发生晶间腐蚀,表面粗糙度增大,且随着KMnO4浓度的提高,腐蚀速度上升.当KMnO4浓度在0.5%时,腐蚀速度近80 nm/h,并发现电荷传递电阻下降,金属耐蚀性降低,晶间电阻减小,晶间腐蚀加剧,界面电容提高,金属表面形貌均匀性下降等现象.     

1Cr18Ni9Ti不锈钢低周疲劳随动硬化实验研究

为了研究单调加载对1Cr18Ni9Ti不锈钢材料后继循环塑性硬化和流动特性的影响,对该材料进行了带平均应变的低周疲劳实验研究.对不同应变幅值的对称应变及非对称的应变循环进行了屈服面半径和背应力演化分析,揭示了材料的随动硬化和各向同性硬化演化对应变幅值和平均应变的依赖性.实验结果为建立循环加载和单调加载耦合的复杂加载条件下的本构模型提供了实验基础.     

HEDP对硝酸去污体系中1Cr18Ni9Ti的腐蚀影响

采用失重腐蚀实验、电化学测试、金相及电子扫描探针观测,研究在硝酸清洗条件（浓度10%HNO3、温度50℃）添加HEDP对1Cr18Ni9Ti的腐蚀影响。结果表明：添加HEDP后1Cr18Ni9Ti在HNO3体系的耐点蚀性能进一步提高,且HNO3与HEDP的二次钝化现象有一定的协同作用,有利于1Cr18Ni9Ti在HNO3体系中钝化膜被破坏后的再修复。初步证明了添加HEDP到HNO3作为反应堆一回路管道拆除前非破坏性清洗去污试剂配方的可行性。     

Nb-1Zr与1Cr18Ni9Ti高温真空钎焊工艺研究

采用BNi-5钎料,对Nb-1Zr与1Cr18Ni9Ti高温真空钎焊工艺进行试验研究,对试验钎焊的接头进行了密封性能检验、抗热冲击性能试验、接头界面区微观分析以及钎缝拉伸强度试验.通过分析试验结果,确定了Nb-1Zr与1Cr18Ni9Ti高温真空钎焊工艺规范参数.     

1Cr18Ni9Ti管道焊缝金属疲劳短裂纹萌生与早期扩展

复型研究了1Cr8N9Ti管道焊缝金属的疲劳短裂纹萌生与早期扩展特点，结果表明，有效短裂纹萌生于与管道内外表面一致的试样表面局部区域中delta铁素体与基质的界面，早期扩展具有显著微观结构效应特征，最大障碍尺度约为40μm，与焊缝金属特征微观组织结构――柱状晶中富delta铁素体带距离一致，该尺度范围。由于强微观结构约束，短裂纹密度较高并逐渐增加；尺度不规则扩展，直到若干较长短裂纹发生合并形成导致试样失效的主导短裂纹。这一过程通常称为“微观结构短裂纹（MSC）“阶段，主导短裂纹及其发路径上的短裂纹对疲劳损伤做出直接贡献，可分别称为“主导有效短裂纹（DESFC）“和“有效短裂纹（ESFCs）“，为描述该阶段不规则行为，有必要引入尺度等于ESFCs尺度均值的虚裂纹即MSC阶段DESFC的概念，该阶段DESFC尺度恒定增加，扩展率恒减小。     

平均应变对0Cr18Ni10Ti管道钢随机应变-疲劳寿命关系的影响规律

试验研究了平均应变对0Cr18Ni10Ti管道钢随机应变-寿命关系的影响规律从节约试样和试验费用角度,采用改进的极大似然疲劳试验法,应变比分别为-1、-0．52、-0．22、0．029、0．18和0．48的条件下,完成了104个试样的应变控制疲劳试验在材料具有完全平均应力松弛特征、现有平均应变理论无法表征其影响情况下,首先基于Coffin—Manson方程,应用广义极大似然法有效地测定出各应变比下材料的随机应变-寿命关系．通过比较各应变比下疲劳寿命均值、对数疲劳寿命均方差和概率疲劳寿命,揭示出0Cr18Ni10Ti管道钢高可靠性时,应变比大于0有大约1．3-1．6的正面效应,小于0为负面效应现有平均应变效应研究仅考虑疲劳寿命均值可能给出错误评价;必须综合考虑均值、均方差和样本量3因素才能给出合理评价。     

Thermodynamic properties of nonstoichiometric urania-gadolinia solid solutions in the temperature range 700–1100° C

Partial molar thermodynamic quantities for urania-gadolinia solid solutions of compositions U_1−yGd_yO_2+x, with y values of 0.04 to 0.27, have been obtained using a solid electrolyte galvanic cell technique. The measurements were made for O/M ratios ranging from near stoichiometry to 2.20, and for temperatures ranging from 700 to 1100°C. The results for pure UO_2+x are in accordance with data reported earlier. The oxygen potentials for U_1−yGd_yO_2+x are higher than for pure UO_2+x and increase positively with increasing Gd content or excess oxygen. They can be represented as a function of the mean U valence, except at the stoichiometric composition. Both the partial molar entropy and enthalpy increase negatively with increasing Gd content or excess oxygen.     

A swelling model for stoichiometric SiC at temperatures below 1000°C under neutron irradiation

A simple phenomenological model for the saturation swelling below 1000°C of neutron-irradiated silicon carbide (SiC) is presented in this paper. Under fast neutron irradiation, SiC is known to undergo volumetric expansion (swelling) which quickly saturates at a fast fluence of approximately 10²⁵ n/m² for irradiation temperatures below 1000°C. A previous model due to Balarin attributes swelling to lattice dilation as a result of single point defects. We show in this paper that the experimentally observed linear temperature dependence of saturation swelling can be explained in terms of the formation and growth of small interstitial clusters, resulting directly from collision cascades initiated by energetic neutrons. These loops grow by absorption of mobile carbon interstitials and their composition is subject to stoichiometry constraints, requiring absorption of slower silicon interstitials. Because of cascade re-solution events, the density of loops decreases sharply with temperature as a result of overlap of cascades with larger size loops at higher temperatures. The average radius of these loops increases with temperature. Volumetric swelling is shown to obey a linear temperature dependence as a consequence of the strong decrease in density and the simultaneous increase in average radius, and to saturate with fluence. The model is shown to be consistent with experimental observations. In the temperature range below 500–600°C, swelling seems to be dominated by single point defects, or defect clusters containing only a few atoms, in accordance with the explanation offered by Balarin.     

平均应变对0Gr18Ni10Ti钢随机循环应力-应变关系的影响规律

试验研究了平均应变对0Cr18Ni10Ti管道钢随机循环应力-应变关系的影响规律.从节约试样和试验费用角度,提出了改进的极大似然疲劳试验法,以应变比分别为-1、-0.52、-0.22、0.029、0.18和0.48完成了104个试样的应变控制疲劳试验.揭示出材料具有Masing行为和完全平均应力松弛特征,现有平均应变理论无法表征其影响.因此,首先基于Ramberg-Osgood方程,应用广义极大似然法有效地测定出各应变比的材料随机循环应力-应变关系.通过比较各应变比的循环应力幅均值、循环应力幅均方差和概率循环应力幅,揭示出高可靠性管理时,平均应变具有降低循环应力幅作用,应变比接近0时最显著,偏离逐渐减弱.说明了研究平均应变效应,仅考虑均值,可能给出错误评价;必须综合考虑均值、均方差和样本量3因素才能给出合理评价.     

Creep rupture of a 9Cr1MoNbV steel at 500 °C: Base metal and welded joint

ASME Grade 91 steel base metal and a similar weld were tested under creep at 500 °C for rupture time up to 18,000 h. Creep failure of cross-weld specimens occurs in the weld metal at this temperature. No significant microstructural changes were observed after creep. Analysis of creep deformation of smooth creep bars, welded joints and slightly notched bars indicated an apparent creep stress exponent of 19. For the creep conditions considered, failure of the material can be explained by the viscoplastic instability of the specimens without significant damage development. This allowed to develop a simple analysis for time to failure prediction.     

0Cr18Ni10Ti不锈钢源壳TIG焊接温度场数值模拟及试验验证

针对0Cr18Ni10Ti不锈钢放射源源壳钨极氩弧焊(TIG)焊接过程,采用ANSYS有限元软件对焊接温度场进行数值模拟分析,建立了非稳态TIG焊接熔池形态的数值分析模型,分析中引入了热焓和表面分布高斯电弧热源模型,初步计算了焊接电流和焊接速度对焊接温度场分布的影响。通过比较焊缝有效熔深的测量结果和计算结果,验证了所建模型的正确性和可靠性。以计算结果为基础,对焊接工艺参数进行优化,建立了0Cr18Ni10Ti不锈钢放射源源壳的焊接工艺路线。     

0Cr18Ni12Mo2Ti奥氏体不锈钢的疲劳性能测试和S—N曲线的验证

０Ｃｒ１８Ｎｉ１２Ｍｏ２Ｔｉ奥氏体不锈钢是核电工业，石油化工生产中常用的合金钢之一。但是对它的实际疲劳有测试在国内未见报导。本文按照美国ＡＳＴＭ有关标准和我国的相关国家标准通过应变控制实测了０Ｃｒ１８Ｎｉ１２Ｍｏ２Ｔｉ的应变疲劳性能。得到了０Ｃｒ１８Ｎｉ１２Ｍｏ２Ｔｉ奥氏何不锈钢在常温条件下的疲劳裂纹扩展速率计算公式，对轴向疲劳试验结果应用美国ＡＳＭＥＳｅｅⅢ 疲劳分析为基础的设计方法进行了处理，     

Evaluation of inelastic constitutive models under plasticity-creep interaction for steel at 600°C

Uniaxial tests to identify plasticity-creep interaction in steel at 600°C were carried out as the Benchmark Project by the Subcommittee on Inelastic Analysis and Life Prediction, JSMS. The purpose of this paper is to present recent experimental data and predictions of constitutive models obtained in the project. Ten types of constitutive models were utilized to compare analytical predictions to sixteen benchmark experiments which are grouped into four categories: (I) tensile and creep tests under monotonic loading, (II) mixed mode tests under plastic and creep loading, (III) ratcheting deformation tests under program loads, and (IV) cyclic deformation tests under the combination of different strain rates. The benchmark tests in Group IV are used to estimate the creep-fatigue life of steel; the results will be published in a separate paper.