中温低合金耐热钢蠕变行为及其微观机理

通过室温、高温拉伸、Gleeble热模拟试验,光学显微镜(OM)及高分辨透射电镜(HR-TEM)观察,研究了中温低合金(CrMo、Cr-Mo+微合金)耐热钢的拉伸、蠕变行为及其微观机理。结果表明,高温270℃下,低合金耐热钢拉伸应力-应变曲线的屈服平台消失,形成连续光滑的应变强化曲线。相比于C-Mn钢,低合金耐热钢的高温强度明显升高。高温350℃下,相比于C-Mn钢,低合金耐热钢的蠕变速率明显降低,其中Cr-Mo+微合金钢的蠕变速率最小。微合金元素形成的强碳化物抑制了Cr、Mo合金元素从基体中析出,Cr-Mo+微合金钢的蠕变抗力得到提高。     

元素Re对选区激光熔化GH4169合金组织与蠕变性能的影响

通过热处理、蠕变性能测试和组织形貌观察,研究了稀有元素Re对GH4169合金微观组织及蠕变性能的影响。结果表明:元素Re的添加对γ'相筏状组织起到细化作用,可促使δ相沿晶界析出抑制晶界滑移,可提高合金显微硬度。经过固溶和时效处理后合金组织细化明显,短针状δ相和长条状MC型碳化物减少。在蠕变期间,δ相的数量会影响合金的断裂方式。元素Re的添加可提高合金的高温蠕变性能。     

镍基单晶高温合金蠕变行为研究进展

从镍基单晶高温合金蠕变中γ'相定向粗化和筏化、蠕变各向异性、蠕变寿命预测及Re和Ru元素对蠕变性能的影响方面,综述了镍基单晶高温合金蠕变行为的研究进展,并对镍基单晶高温合金的发展方向进行了展望。     

Ru对镍基单晶高温合金微观组织的影响

为了提高镍基单晶高温合金的高温强度和其他综合性能,第四代合金中加入了铂族元素Ru。Ru的加入降低了γ相的堆垛层错能,减少了γ＇相的体积分数。作为一种有效的固溶强化元素,Ru对γ相和γ＇相的强化均起到了很显著的作用,提高了合金的蠕变性能,同时Ru也影响了难熔元素在合金中的偏析行为,降低了难熔元素在γ相中的过饱和度,并能抑制TCP相等有害相的析出,显著提高了合金的抗蠕变性能和合金显微组织的稳定性。综合分析了Ru的加入对镍基单晶高温合金微观组织结构的影响。     

低活化铁素体/马氏体钢搅拌摩擦焊接头的高温蠕变性能

对5 mm厚度的低活化铁素体/马氏体钢（Reduced activation ferritic/martensitic steel,RAFM）进行了搅拌摩擦焊接,通过焊接接头的高温蠕变实验,研究低活化钢搅拌摩擦焊接头的高温蠕变性能与失效机理。结果表明,低活化钢搅拌摩擦焊接头高温力学性能良好。合金元素W和Ta含量高的RAFM钢的接头高温蠕变寿命更长,原因是Ta和W在高温环境中形成了更多的析出相,包括MX相和Laves相,对位错滑移的阻碍作用更强。650℃的蠕变寿命远远短于600℃的原因可能是,高温使得位错非常容易发生滑移,在Laves相还没有长大、MX相对位错滑移的阻碍作用不够强的情况下,在某些部位形成了密集的蠕变孔洞,造成有效横截面积急剧减少,应力集中严重,引发裂纹导致断裂。     

协同Orowan绕过和攀移机制的镍基高温合金蠕变新模型（英文）

提出一种用于准确便捷预测析出相增强镍基高温合金稳态蠕变速率的蠕变新模型。基于析出相的空间分布,采用概率依赖的方法将位错-析出相交互作用中Orowan绕过和位错攀移机制的协同模式耦合到新的蠕变模型中。结果表明,新模型预测的稳态蠕变速率与实验数据吻合很好。此外,当前模型不再依赖于可调参数;同时,确定了阈值应力与温度的定量关系。这项工作为蠕变变形过程中位错-析出相交互作用提供新思路,并为设计具有更优异蠕变性能的析出强化合金提供有效模型。     

P92钢高温蠕变损伤分析

对650℃,100 MPa条件下蠕变1546.5 h的P92钢试样进行了组织热损伤及应变损伤观察,分析了蠕变孔洞形成机理。结果表明,分布于板条间的M23C6相的粗化不明显,保持较高的数量密度,晶界上粗大的M23C6相大部分消失,导致其体积分数明显减少。在晶界上析出密集分布的的Laves相,平均等效直径为320 nm,体积分数约为2.6%。在晶界上形成了单个分布的蠕变孔洞,蠕变孔洞的形成与晶界上析出Laves相密切相关。由于Laves相分布于晶界,其沉淀强化作用不大,使基体合金元素贫化,促进蠕变孔洞的形成而降低P92的蠕变断裂强度。要进一步提高新型马氏体热强钢蠕变性能的关键是抑制Laves相在晶界的析出。     

ZG35Cr26Ni12WNRE奥氏体耐热钢的研制

在ZG35Cr26Ni8NRE炼镁还原罐用耐热钢的基础上,开发了ZG35Cr26Ni12WNRE奥氏体耐热钢,并研究了新研制耐热钢的组织结构和蠕变性能。结果表明,新研制耐热钢的奥氏体基体固溶有较多的碳元素,含有较少的大尺寸(几十微米)颗粒状和蠕虫状碳化物相,在高温条件下会析出较多的超细颗粒(1微米左右)碳化物相;新研制耐热钢在1 000℃、16 MPa条件下的蠕变第二阶段蠕变速率为0.000 2%·h~(-1),仅是ZG35Cr26Ni8NRE的1/7,高温蠕变性能大幅提高。     

镍基单晶高温合金的小角度偏离[001]取向对蠕变性能的影响

小角度偏离[001]取向的镍基单晶高温合金的蠕变性能受温度、γ?尺寸的大小和应力条件的影响。本文综述了镍基单晶高温合金的[001]取向小角度偏离对蠕变性能的影响。不同程度的偏离引起的不同蠕变性能变化,源于不同的蠕变变形机制。不同的蠕变变形机制对应着引起蠕变率发生的不同临界应力。在中温(760℃-850℃),合金的蠕变性能对[001]取向的角度偏离很敏感,即使角度有一点变化也会引起蠕变性能的很大的差异,但是在温度高于850℃以上小角度的取向偏离对蠕变性能影响不大。γ?尺寸的大小对小角度偏离的合金的蠕变性能的影响受温度的制约。在中温,γ?尺寸的大小变化影响着不同的小角度偏离是否引起蠕变性能的变化,但是在高温γ? 相快速伐化,变形机制和γ?尺寸变化无关。     

镍基单晶高温合金的小角度偏离[001]取向对蠕变性能的影响（英文）

小角度偏离[001]取向的镍基单晶高温合金的蠕变性能受温度、γ'尺寸和应力条件的影响。本文综述了镍基单晶高温合金的[001]取向小角度偏离对蠕变性能的影响。不同程度的偏离引起的不同蠕变性能变化,源于不同的蠕变变形机制。不同的蠕变变形机制对应着引起蠕变发生的不同临界应力。在中温(760～850°C),合金的蠕变性能对[001]取向的角度偏离很敏感,即使角度有轻微变化也会对蠕变性能有明显影响,但是温度高于850°C时,小角度的取向偏离对蠕变性能影响不大。γ'尺寸对小角度偏离的合金蠕变性能的影响受温度制约。在中温,γ'尺寸的变化影响着小角度偏离引起的蠕变性能变化,但是在高温γ'相快速伐化,变形机制和γ'尺寸变化无关。     

高铬耐热钢蠕变过程中的组织演化行为

结合国内外对高铬耐热钢的最新研究成果,从强化机制出发,总结分析了高铬耐热钢在蠕变过程中微观组织的演化行为。长时蠕变过程中由于M₂₃C₆碳化物和Laves相的粗化,高铬耐热钢性能下降,通过调整元素含量及改进热处理工艺可提高高温组织的稳定性。Z相的形成与MX相的消耗密切相关,目前对于Z相的成核机理尚不能达成一致,因此生成足够量的MX碳氮化物并保持高温长时作用下组织的稳定性是提高高铬耐热钢高温性能的有效途径。     

Effect of boron and carbon addition on microstructure and mechanical properties of the aged gamma-prime strengthened alumina-forming austenitic alloys

The goal of this work was to understand the effects of aging at 800 °C on the microstructures and mechanical properties of two recently-developed AFA stainless steels based on Fe-14Cr-32Ni-3Nb-3Al-2Ti (wt.%), one of which contained small additions of boron and carbon. To that end both the size distributions and growth kinetics of the B2, Laves phase, L1₂ precipitates present were quantified. While the lattice parameter, morphology, size and coarsening behavior of the L1₂ precipitates was the same in both AFA alloys, the B and C enhanced the grain boundary coverage by both Laves phase and B2-NiAl precipitates, but suppressed their coarsening. These interstitial additions also suppressed the formation of twins and discontinuous precipitation, which were observed in the B and C-free material. It is shown that the yield strength at 700 °C is largely controlled by the size of the L1₂ precipitates, with the largest strengthening effect obtained after aging for 2.4 h for both AFA alloys. Longer aging time led to a loss of strength mainly due to the coarsening of the L1₂ precipitates.     

胎盘组织核因子-κB与妊娠并发症关系研究进展

核因子-κB（NF-κB）是一种细胞内重要的转录因子,调控包括炎症、凋亡在内多种基因的表达,在胎盘中分布广泛。本文对胎盘组织中NF-κB与先兆子痫、HELLP综合征和胎膜早破等妊娠并发症的关系研究进行综述,概括了胎盘NF-κB在这些妊娠并发症发生过程中的作用以及依赖NF-κB途径治疗相关疾病的研究进展,为胎盘相关疾病的深入研究奠定基础,为妊娠并发症疾病的诊治提供新思路。     

New martensitic steels for fossil power plant: Creep resistance

In this paper, we consider the origin of high-temperature strength of heat-resistant steels belonging to martensitic class developed on the basis of the Fe—9%Cr alloy for the boiler pipes and steam pipelines of power plants at steam temperatures of up to 620°C and pressures to 300 atm. In addition, we give a brief information on the physical processes that determine the creep strength and consider the alloying philosophy of traditional heat-resistant steels. The effect of the chemical and phase composition of heat-resistant steels and their structure on creep strength is analyzed in detail. It is shown that the combination of the solid-solution alloying by elements such as W and Mo, as well as the introduction of carbides of the MX type into the matrix with the formation of a dislocation structure of tempered martensite, ensures a significant increase in creep resistance. The steels of the martensitic class withstand creep until an extensive polygonization starts in the dislocation structure of the tempered martensite(“troostomartensite”), which is suppressed by V(C,N) and Nb(C,N) dispersoids. Correspondingly, the service life of these steels is determined by the time during which the dispersed nanocarbonitrides withstand coalescence, while tungsten and molybdenum remain in the solid solution. The precipitation of the Laves phases Fe₂(W,Mo) and the coalescence of carbides lead to the development of migration of low-angle boundaries, and the steel loses its ability to resist creep.     

Al元素对Ti-V-Cr系阻燃钛合金热强性影响的研究

制备了Ti-25V-15Cr-0．2Si和Ti-25V-15Cr-2Al-0．2Si2种阻燃钛合金，分别测试其在不同热暴露和蠕变工艺条件下的热稳定性能和蠕变性能，并观察了组织。结果表明，Al元素提高了Ti—V-Cr系阻燃钛合金的室温力学性能，降低了热稳定性能和抗蠕变性能；在实验的热稳定和蠕变工艺参数下，2种合金中只存在a相和Ti5Si3相，没发现其他过渡相和中间化合物；在热暴露和蠕变过程中，组织稳定性降低，Al元素的添加促进了a相和Ti5si，相的析出，降低了Ti-V-Cr系阻燃钛合金抗蠕变性能和热稳定性能。     

GH4169合金与S31042钢线性摩擦焊接头组织及力学性能

使用25 Hz振动频率、2 mm振幅、100 MPa摩擦压力和150 MPa顶锻压力的工艺参数对GH4169合金和S31042钢进行线性摩擦焊连接,通过OM、SEM和TEM分析异质接头的组织特征,并进行拉伸、硬度和蠕变实验测试异质接头在室温和高温环境下的力学性能。结果表明,GH4169合金与S31042钢的连接界面在线性摩擦焊过程中发生动态再结晶,形成无孔无裂纹的冶金结合,同时焊缝区在高温和应力作用下形成大量弥散分布的强化相颗粒。通过细晶强化和析出强化的综合作用,异质接头的抗拉强度高于S31042钢,焊缝区的硬度明显高于2种母材。     

The effect of W and N addition on the mechanical properties of 10Cr steels

The effect of W and N on the creep properties and microstructural degradation in 10Cr steels was studied. Creep testing was performed to determine the creep rupture strength and minimum creep rate. Transmission electron microscopy was used to observe the microstructural degradation during the creep deformation. W and N which were added to the 10Cr steel increased the creep rupture strength and decreased the minimum creep rate. As W and N were added, the thermal stability of the subgrain and carbide was improved, thus the growth of the subgrain and carbide during creep deformation was restricted. In W added steel, the Laves phase played an important role in increasing creep rupture strength. But the impact toughness was rapidly degraded by the addition of W after aging at 600°C for 5000 hours. So one must evaluate more accurately the effect of the Laves phase on long term creep and impact properties. In N added steel, V(C, N) was precipitated in the lath boundary and within the lath. The size of the precipitates was 20–50 nm. The increase of creep rupture strength in N added steel may be due to the precipitate of the V(C, N). Future tests are required to clarify the effect of N on creep and impact properties.     

EFFECT OF W ON MECHANICAL PROPERTIES OF 12%Cr HEAT-RESISTANT STEEL

The effect of W on mechanical properties of 12% Cr-W-V-Nb heat resistant steel at hightemperatures and room temperature is reported.The experimental results indicated that if theW content was about 2.2—3.0 wt-%,there was no obviously change of R.T.tensile strength,but impact toughness decreased with the rise of W content.On the other hand,the increase ofW content enhanced the short time stress rupture strength,but did not for the long time one.The increase of W have two effects on the precipitation behavior,promoting Laves formationof type Fe_2W,increasing the precipitated phase amount and speeding up the coarsening pro-cess of precipitated phase at high temperatures.The effect of W on the mechanical propertiesis closely associated with precipitation behaviors.When the rupture life is short,there has noenough time to coarsen the precipitated phases,so the increase of precipitated phases results instrengthening effect,i.e.the W increases the high temperature strength.After prolonged expo-sure,the evident coarsening took plaee,that decreased the effect of precipitation.     

Creep in grain coarsened ODS MA NiAl

NiAl based oxide dispersion strengthened (ODS) intermetallic alloys have been produced by mechanical alloying (MA) and consolidated by hot extrusion. Subsequent isothermal annealing was carried out to induce normal grain growth (NGG), and a thermomechanical treatment was performed to induced secondary recrystallization (SRx). SRx resulted in pronounced elongated grain growth without dispersoid coarsening, whereas concurrent equiaxed coarsening of grains and dispersoids occurred in NGG specimens. Creep properties of grain coarsened ODS MA NiAl were investigated, and the associated creep mechanisms were evaluated. The creep properties of SRxed MA NiAl are compared with those of as-consolidated MA NiAl and other counterparts. It has been shown that SRx results in improved creep resistance compared to NGG mechanism. The apparent activation energy and the stress exponent for creep indicate that SRx MA NiAl exhibits intermediate creep behavior of the two limiting dislocation creep modes; climb, controlled and viscous glide controlled. However, a grain size dependent creep has been shown, indicating that grain boundary sliding mechanism contributes to the overall deformation in MA NiAl.     

工模具钢和铁素体耐热钢的合金化设计概要

应用材料科学的基本原理,总结了合金元素加入钢中的作用要点,提出了加入钢中的合金元素的交互作用对钢的组织和性能的影响与其钢在使用条件下的性能要求相平衡的合金化设计原则,并以热作模具钢H13和铁素体耐热钢等为例作了说明.