Effect of aging temperature on the microstructures and mechanical properties of ZG12Cr9Mo1Co1NiVNbNB ferritic heat-resistant steel

The effect of aging on the mechanical properties and microstructures of a new ZG12Cr9 MolColNiVNbNB ferritic heat resistant steel was investigated in this work to satisfy the high steam parameters of the ultra-supercritical power plant.The results show that the main precipitates during aging are Fe（Cr,Mo）23C6,V（Nb）C,and（Fe2Mo） Laves in the steel.The amounts of the precipitated phases increase during aging,and correspondingly,the morphologies of phases are similar to be round.Fe（Cr,Mo）23C6 appears along boundaries and grows with increasing temperature.In addition,it is revealed that the martensitic laths are coarsened and eventually happen to be polygonization.The hardness and strength decrease gradually,whereas the plasticity of the steel increases.What＇s more,the hardness of this steel after creep is similar to that of other 9%-12%Cr ferritic steels.Thus,ZG12Cr9 MolColNiVNbNB can be used in the project.

Coarsening behavior of MX carbonitrides in type 347H heat-resistant austenitic steel during thermal aging

In this work, the growth kinetics of MX （M - metal, X - C/N） nanoprecipitates in type 347H austenitic steel was systematically studied. To investigate the coarsening behavior and the growth mechanism of MX carbonitrides during long-term aging, experiments were performed at 700, 800, 850, and 900℃ for different periods （1, 24, 70, and 100 h）. The precipitation behavior of carbonitrides in specimens subjected to various aging conditions was explored using carbon replicas and transmission electron microscopy （TEM） observations. The corresponding sizes ofMX carbonitrides were measured. The results demonstrates that MX carbonitrides precipitate in type 347H austenitic steel as Nb（C,N）. The coarsening rate constant is time-independent; however, an increase in aging temperature results in an increase in coarsening rate of Nb（C,N）. The coarsening process was analyzed according to the calculated diffusion activation energy of Nb（C,N）. When the aging temperature was 800-900℃, the mean activation energy was 294 kJ·mol -1, and the coarsening behavior was controlled primarily by the diffusion of Nb atoms.

DETERMINATION AND APPLICATION OF LARSON-MILLER PARAMETER FOR HEAT RESISTANT STEEL 12CrlMoV AND 15CrMo

Based on the analysis and processing on relative empirical formula and data, C-values in Larson-Miller (P) expression, P= T(C + Igt), have determined for pearlitic heat resistant steel 12Cr1MoV and 15CrMo(20.62 and 20.30). The simulation experiments of high temperature aging, heated from 1.5 to 873 hours, have been designed and performed for its verification. And in combination with published information and the present nearly quantitative works, it has further been verified that both the degradations of microstructures and mechanical properties show a good accuracy and practicability using the Larson-Miller parameter with the present determined C-values. Finally, the effects of carbon content on C-value are analyzed by the empirical electron theory of solids and molecules (EET).

VARIATION OF SUBSTRUCTURES OF PEARLITIC HEAT RESISTANT STEEL AFTER HIGH TEMPERATURE AGING

The observations of dislocations, substructures and other microstructural details were conducted mainly by means of transmission electron microscope (TEM) and scanning electron microscope (SEM) for 12CrlMoV pearlitic heat-resistant steel. It is shown that during the high temperature long-term aging, the disordered and jumbled phase-transformed dislocations caused by normalized cooling are recovered and rearranged into cell substructures, and then the dislocation density is reduced gradually. Finally a low density linear dislocation configuration and a stabler dislocation network are formed and ferritic grains grow considerably.

STUDY OF DEGRADATION MECHANISM AND PACKAGING OF ORGANIC LIGHT EMITTING DEVICES

Organic Light Emitting Devices (OLED) have attracted much attention recently, for their applications in futureFlat Panel Displays and lighting products. However, their fast degradation remained a major obstacle to theircommercialization. Here we present a brief summary of our studies on both extrinsic and intrinsic causes for the fastdegradation of OLEDs. In particular, we focus on the origin of the dark spots by 'rebuilding' cathodes, which confirms thatthe growth of dark spots occurs primarily due to cathode delamination. In the meantime, we recapture the findings from thesearch for suitable OLED packaging materials, in particular polymer composites, which provide both heat dissipation andmoisture resistance, in addition to electrical insulation.

Identification of parameter to assess cracking resistance of asphalt mixtures subjected to aging and moisture conditioning

This study comprehensively evaluated different parameters based on tensile strength testing to assess the cracking resistance of asphalt mixtures subjected to aging and moisture conditioning.For this purpose,two sources of aggregates were selected to produce hot and warm mix asphalt mixtures.Asphalt mixtures were subjected to short term and long term aging,three levels of moisture conditioning(freeze thaw cycles),and tested at two temperatures(15℃and 25℃).The load-displacement data was used to determine the fracture work density,fracture energy,toughness index,cracking resistance index,cracking tolerance index,and rate dependent cracking index.It was noticed that moisture conditioning increased the variability of the different parameters.The cracking tolerance index and rate dependent cracking index parameter had a much higher coefficient of variation(Co V)with a maximum value close to 50%.Indirect tensile strength,fracture energy,and fracture work density appropriately captured the effect of moisture on cracking resistance of mixtures.The cracking resistance index,cracking tolerance index,and rate dependent cracking index increased with an increase in the moisture conditioning level.The Statistical analysis showed that tensile strength,fracture work density,and fracture energy were significantly influenced by different aging and moisture conditions evaluated.Fracture energy showed better association with fatigue life of asphalt mixtures subjected to three freeze-thaw cycles compared to tensile strength.Further,the fatigue life prediction models showed that both indirect tensile strength and fracture energy significantly influence the fatigue life of asphalt mixtures subjected to aging and moisture conditioning.

Structure and Property of AgLaY Alloy

The structure of RE-Ag alloy was observed and analyzed using electron probe. The property changes of the alloy containing two rare earth elements AgLaY during cold forming and the high temperature softening-resistance during annealing were studied using Vickers hardness tester. The distribution and action of the rare earth elements in Ag-alloy were also analyzed. Experimental results show that AgLaY alloy has more remarkable work-hardening effect than AgLa and pure silver, and it also has better thermal-resistance. The effects of RE elements, La and Y, on the properties of Ag-alloy are attributable to their symbiotic distribution and complementary function. Because of the common properties of La and Y as RE elements, they have the completely similar distribution in Ag-alloy. At the same time, La and Y make full use of complementary role in the alloy since they belong to different periods in periodic table and have differences in atomic structure and properties.

A STUDY OF TRANSMISSION OF MOISTURE THROUGH FABRICS

Based on the Dynamic Dress Model which can simulate the body core temperature and skintemperature,as well as body sweating,this paper holds a further inquiry into the new method formeasuring heat resistance of fabrics and moisture transmission in terms of“clo”unit andpermeability index“im”.It is found out that the values of Tex of warp and weft have the greatestinfluence on permeability index im and when the thread count increases to a certain limit,thepermeability index“im”is in direct proportion to thread count.

Characterization and numerical simulation of nucleation-growth-coarsening kinetics of precipitates in G115 martensitic heat resistance steel during long-term aging

The service performance of heat resistance steels is largely determined by the precipitation kinetics.The nucleation-growth-coarsening behaviors of precipitates in G115 martensitic heat resistance steel during long-term aging at 650℃ have been systemically investigated.The microstructural characteristics,precipitate morphology and alloying element distribution were studied by scanning electron microscopy,transmission electron microscopy and scanning transmission electron microscopy.The lognormal distribution fitting combined with the multiple regression analysis was adopted to evaluate the precipitate size distributions.Laves phase has longer incubation time,and its coarsening rate is almost one order of magnitude higher in comparison with that of M_(23)C_(6) carbide.Furthermore,the nucleation rate,number density,average radius,and volume fraction of two precipitates are simulated based on the classical nucleation theory and the modified Langer-Schwartz model.The precipitation behavior of Laves phase can be well explained with the Fe-W system as the interfacial energy takes 0.10 J/m^(2).In contrast,the simulation results of M_(23)C_(6) carbide in the Fe-Cr-C system are significantly overestimated,which results from the inhibitory effect of boron on coarsening.

丁腈橡胶耐石油开采介质影响因素分析

研究了结合丙烯腈含量、硫化体系、增强体系和增塑体系对丁腈橡胶(NBR)耐石油开采领域中常见化学介质腐蚀规律的影响。结果表明,随着结合丙烯腈含量的增加,NBR硫化胶的物理机械性能及耐热空气老化性能均提高,耐煤油、海底控制液等非极性介质的性能较好,耐甲醇、蒸馏水和乙二醇水溶液的性能逐渐下降,耐酸碱盐水溶液的性能相差不大;硫化体系主要影响NBR硫化胶的物理机械性能及耐热空气老化性能,对NBR硫化胶耐各种石油开采介质的影响则相差不大;对于高硬度NBR硫化胶,当增强体系采用小粒径炭黑时,NBR硫化胶的物理机械性能最好,不同增强体系对NBR硫化胶耐热空气老化性能的影响并不明显,但当增强体系采用大粒径炭黑时,NBR硫化胶具有更好的耐甲醇和煤油的性能,同时要求选用惰性填料进行增强;添加了大分子酯类增塑剂的NBR硫化胶较添加小分子酯类增塑剂、液体NBR增塑剂的物理机械性能更为优异,耐热空气老化性能相差不大,但耐各种石油开采介质的体积变化均偏大,耐甲醇、煤油及10%氢氧化钠水溶液的性能较差,而耐其他石油开采介质的影响则较小。

抗氧剂对石油树脂性能的影响

采用共混的方式制备了一系列添加抗氧剂的石油树脂,通过红外光谱仪、色度仪以及热重分析仪进行表征,并对石油树脂的抗老化性能进行评价。结果表明:温度的升高会促进石油树脂的老化,抗氧剂的加入能够一定程度抑制石油树脂的老化;添加抗氧剂B 215的石油树脂抗老化性能与C 100-W接近;抗氧剂B 215能够明显改善石油树脂的耐热性能。

新型耐热合金C-HRA-3高温时效过程析出相成分特征分析

针对C-HRA-3耐热合金在700℃和750℃时效后的试样研究了M_(23)C_(6)碳化物和γ′相化学相组成变化规律。结果表明:C-HRA-3合金经高温时效后析出M_(23)C_(6)碳化物和γ′相,其中M_(23)C_(6)碳化物中合金元素M为Cr、Mo、Ni和Co,γ′相中合金元素有Ni、Co、Al、Ti、Mo、Cr和Nb,时效至8000 h后,700℃时效后M_(23)C_(6)碳化物析出量约0.978%,γ′相析出量约9.5%;750℃时效后,M_(23)C_(6)碳化物析出量约1.023%,γ′相析出量约6.753%,随时效温度升高,M_(23)C_(6)碳化物析出量增加约4.6%,γ′相析出量减小约28.9%。

硅油/PBAT复合材料的制备及耐热性能研究

聚己二酸-对苯二甲酸丁二醇酯(PBAT)作为生物可降解材料在包装领域应用广泛,但存在耐热稳定性差、易受环境影响发生老化等问题。本文采用熔融共混的方法,制备了不同添加比的端羟基硅油(SO)/PBAT复合材料,探讨耐热添加助剂对PBAT热稳定性和可降解性能的影响。结果表明,复合材料具有更好的耐热性,当SO质量分数达0.6%时,最终分解温度提高到411.02℃,热分解速率较纯PBAT降低了10.34%。SO的添加显著延缓了PBAT的热氧老化,SO/PBAT降解稳定性得到提升,热氧降解30 d后0.6%SO/PBAT的拉伸强度保持率较纯PBAT提高了27.48%,质量损失率较纯PBAT降低了20.78%。此外,复合材料的分子量下降幅度减缓,低场核磁反演曲线说明SO的添加并未改变PBAT的热氧老化机理。

不同老化阶段的锂离子电池热特性研究进展

研究锂离子电池不同老化阶段的热特性对于锂离子电池全寿命周期安全运行控制具有重要意义。首先梳理了不同老化阶段电池本征热特性参数和产热特性参数的实验研究进展,厘清相关参数随电池老化阶段变化的规律和内在机理;结合锂离子电池热特性研究的电模型、热模型和老化模型的全面综述与分析,总结了锂离子电池不同老化阶段的产热及温升随环境温度和倍率的变化规律。相关工作可为锂离子电池全生命周期热特性变化和热管理策略研究提供参考。

防热复合材料湿热老化行为与贮存寿命研究

目的研究装备用防热复合材料在贮存条件下的性能变化规律和寿命评估。方法在90℃/90%RH、80℃/90%RH、70℃/90%RH和80℃/80%RH共4个试验条件下,对玻璃纤维增强酚醛树脂防热复合材料开展加速湿热老化试验,借助红外光谱分析、扫描电镜、导热系数和力学性能测试研究老化过程中材料的质量、导热系数、力学性能、化学组分、微观形貌的变化规律,使用Peck模型对材料的贮存寿命进行计算。结果材料在老化初期吸湿后,质量快速增加,吸湿趋于饱和后,质量达到最大值。随着老化时间的延长,材料的质量呈缓慢下降趋势。不同湿热条件下,材料的导热系数未出现性能退化现象,材料的拉伸强度均出现退化现象,老化温度越高,性能下降越明显。在90℃/90%RH条件下,老化时间为80d时,材料强度大约下降到初始性能的53.4%。湿热老化过程中,红外光谱中960cm^(‒1)处特征峰逐渐减弱,直至完全消失,1098cm^(‒1)处特征峰相对强度逐渐变强。湿热老化后,材料部分玻璃纤维与基体间界面有微裂纹产生,拉伸断裂后,大部分纤维从树脂基体中拔出,表面平整光滑,黏连树脂较少。结论防热复合材料的老化是由氧化反应的化学老化与湿热条件导致界面脱黏、基体开裂、微裂纹等物理老化综合作用的结果。防热复合材料在20℃/60%RH条件的贮存寿命为36.3a,满足实际构件的设计寿命。

低压干燥条件下热湿氧协同输送管道摩擦阻力特性

青藏高原低压缺氧干燥的特殊气候条件使建筑室内有加湿增氧的需求,而现有研究未考虑低压和加湿增氧导致空气组分变化对管道摩擦阻力特性的影响。本文以输送热湿氧直管道为对象,研究了大气压力、入口流速、湿氧浓度、管径、壁面粗糙度等因素对摩擦阻力的影响。结果表明:当管道仅送热时,5 km海拔下管道单位管长摩擦阻力约为常压下的62%;当热湿氧协同输送时,供氧浓度升高可使管道单位管长摩擦阻力增大约8.4%,而增大相对湿度对单位管长摩擦阻力影响较小,仅减小2%;单位管长摩擦阻力随入口流速的增大而增大,最大可增大约16倍;在壁面粗糙度较小时(K=0.03~0.20 mm),处于水力光滑区,阻力不随粗糙度的增大而变化;当进入混合摩擦区(K>0.40 mm)时,阻力开始随粗糙度的增大而增大,最大可增大约45%。最后给出了低压条件下热湿氧协同输送管道在不同工况下的摩擦阻力推荐值。

衣康酸单乙酯钆改性天然胶乳防热氧老化研究

为提高天然橡胶的热氧老化性能,利用衣康酸单乙酯和氧化钆为原料在天然胶乳中生成衣康酸单乙酯钆,研究了在过二硫酸钾引发下对天然橡胶接枝改性及其改性后热氧老化性能。结果表明,衣康酸单乙酯钆盐成功接枝到天然橡胶。衣康酸单乙酯的加入削弱了热氧老化对橡胶材料力学性能的影响。改性橡胶的初始降解温度和最大降解速率对应的温度较天然橡胶分别提高了35.6℃和23.8℃。作为新型橡胶助剂,衣康酸单乙酯钆有望改善橡胶防老剂对环境的影响。

Al-Cu-Mn-Fe-Ag-Zr合金的微观组织与室温和高温性能研究

Al-Cu合金具有低密度、耐热性好和潜在的高温稳定性等优点,广泛应用于汽车和航空航天等领域。为提高Al-Cu基铸造合金的耐热性能,本文制备了质量分数为Al-4%Cu-0.5%Mn-0.1%Fe-0.4%Ag-0.3%Zr(简称AC)的合金。采用OM和SEM分析了合金的微观形貌及化学成分,采用XRD分析了合金的物相结构,采用EBSD研究了晶粒形态与尺寸分布,采用TEM分析了合金在时效处理后的微观组织和析出相形态,采用高低温拉伸试验机进行了室温和高温力学性能测试。结果表明,AC合金在铸造过程中形成的金属间化合物主要包括Al_2Cu和Al_7Cu_2Fe,其中,Al_2Cu相在固溶处理后溶入基体中,并在时效处理后重新沉淀为θ′相,成为主要的强化相。此外,经T6热处理后,合金中还包含着T_(Mn)(Al_(20)Cu_2Mn_3)相,Ag元素固溶于铝基体中,而Zr元素则使得合金析出L1_2-Al_3Zr纳米相,其与θ′相存在位向关系。测试了合金在室温和高温(200、300和400℃)下的拉伸性能,对应屈服强度可分别达236、155、129和61 MPa。

高温时效粗、细晶TP347HFG耐热钢管的显微组织与力学性能对比研究

目的揭示奥氏体晶粒粗化对该钢管服役可靠性的影响。方法采用预变形加固溶处理工艺制备粗晶试样,以模拟长期高温服役TP347HFG钢管中奥氏体晶粒异常长大状态。开展650℃直至3600 h时效后的粗、细晶TP347HFG钢试样显微组织及力学性能的对比研究。结果高温时效过程中,粗、细晶试样奥氏体晶粒大小基本保持不变,孪晶密度降低。第二相颗粒析出行为没有明显差异,M_(23)C_(6)相颗粒优先在奥氏体晶界析出、粗化,但粗晶试样中的M_(23)C_(6)相析出更快,粗化更明显。随时效时间延长,粗、细晶试样的室温、高温拉伸力学性能变化趋势基本一致,室温、高温强度变化不明显,但塑性相差较大。经650℃时效3600 h后,粗晶试样600℃拉伸时的断后伸长率较细晶试样显著下降了30.4%。结论粗晶TP347HFG钢管的高温塑性应受到重点关注。