低碳微量铌钢过冷奥氏体形变过程中的碳氮化物析出

利用透射电镜研究了低碳微量铌钢过冷奥氏体形变过程中的碳氮化物析出,运用Gladman晶粒粗化机制讨论了析出相颗粒的平均直径、体积分数和铁素体晶粒尺寸的关系.实验结果表明:实验用钢中的微量Nb在1 200℃时完全固溶,并在760℃变形前的冷却过程中无Nb(CN)析出.在形变过程中Nb(CN)的析出同样需要孕育期,但与等温过程相比大大提前.当变形量积累到一定值(本实验条件下ε=0.69)时,大量动态析出的Nb(CN)颗粒弥散分布在晶界以及位错线上.Nb(CN)析出随着应变量的增加而增加,但颗粒长大不明显,计算得到的铁素体晶粒平均截径与实际测得的铁素体晶粒吻合得较好.     

含Cu-Cr微合金钢650℃回火时第二相析出强化的研究

将含Cu-Cr微合金钢 930℃保温 30min淬火至室温，随后 650℃回火 10min~10h。利用光学显微镜（OM）和透射电子显微镜（TEM）研究不同回火时间条件下，样品中组织演变和第二相析出行为。结果表明：回火过程中组织从马氏体和贝氏体逐渐向针状铁素体和多边形铁素体演变；硬度变化曲线上出现2个二次硬化峰值，分别为回火1h和4h是的硬化峰，前者是V和Mo的碳化物析出强化结果，后者是由富Cu相的析出强化所致，V和Mo的碳化物强化产生的硬度值增量大于富Cu相；Cr的碳化物在回火过程中析出长大速度较快，析出强化能力较弱。     

形变对板条马氏体回火组织的影响

对Q235级低碳钢板条马氏体在550 ℃多道次单向压缩变形后退火和室温大塑性变形轧制后在此温度退火的显微组织演变规律进行了对比研究,结合未变形板条马氏体在此温度的回火组织演变,讨论了变形对马氏体分解过程、铁素体再结晶晶粒尺寸和析出碳化物形貌的影响. 实验结果表明,变形显著影响马氏体分解过程,促进渗碳体的析出和铁素体回复及再结晶. 热变形组织铁素体再结晶晶粒尺寸在0.5 μm左右;渗碳体形貌从细棒状向球状转变,随变形量增大渗碳体尺寸增大,继续保温60 min导致铁素体晶粒长大到1 μm左右,晶粒内部的渗碳体消失,原先在铁素体晶界析出的渗碳体球化、粗化. 冷轧试样在550 ℃退火保温时间在30 min内得到0.3～0.4 μm超细晶粒和尺度小于150 nm的弥散渗碳体颗粒组织;随退火保温时间延长到60 min,铁素体再结晶晶粒长大到1.9 μm,渗碳体颗粒尺寸约160 nm.     

低碳微合金钢回火过程的组织演变规律

采用膨胀实验和差式扫描量热实验,结合SEM、TEM和显微硬度测试,研究了低碳微合金钢700L在回火过程中的组织演变规律。结果表明,700L钢回火过程包括5个阶段:渗碳体I的析出(50～200℃)、残余奥氏体的分解(200～300℃)、渗碳体II的析出(250～400℃)、合金碳化物的析出(450～580℃)和Mn的分配(580～650℃)。在2℃/min的升温速率下,钢中渗碳体析出、合金碳化物析出及Mn分配三个阶段存在明显的硬度改变,而且合金碳化物析出阶段试样的体积改变最显著,这可能是影响钢中残余应力演变的重要阶段。     

回火对Q460E低合金结构钢组织与性能的影响

研究了回火温度对正火Q460E低合金结构钢的力学性能与组织影响.结果表明,在200℃到500℃范围内回火,力学性能相对较为稳定且具有较高的强韧性,而且屈强比也比较低,回火温度升高到600℃,力学性能虽相对较低,但钢的强韧性要比GB/T1591-1994(国标)规定的要高.分析认为:600℃回火强韧性降低幅度相对大的原因主要是粒状贝氏体的分解,碳化物的析出长大球化且分布在条状铁素体边沿,犹如上贝氏体,以及碳化物在原奥氏体晶界分布.200℃回火能够获得较高的强度和突出的韧性.回火过程就是粒状贝氏体分解变化,碳化物析出长大球化过程.     

回火温度对Q960钢析出物组织特征的影响

利用透射电镜、能谱仪(EDX)及多功能内耗仪系统地研究了在相同成分、轧制工艺、淬火工艺和不同回火温度条件下Q960钢组织中析出物的形态、分布和组成,给出了回火温度对析出物组织特征的影响规律.结果显示:回火温度低于400℃时,马氏体内固溶碳量下降趋势较剧烈;回火温度高于400℃时,马氏体内固溶碳量下降非常缓慢.此外,大量细小且平行析出的θ--碳化物溶解并最终被沿马氏体板条界析出的Cr的碳化物代替.随着回火温度的升高,Nb、V和Ti的复合碳氮化物长大,形状也由方形向椭圆形演变.     

强磁场对高铬钢中碳化物低温回火析出的影响

借助透射电镜、维氏硬度仪及计算机模拟,研究了外加强磁场对高铬钢中碳化物低温回火析出的影响。结果表明,试验钢分别在无磁场及外加磁场强度为12T的条件下于200℃回火60min时均有M3C型碳化物析出;在外加磁场作用下,试验钢中析出的M3C型碳化物数密度相比无外加磁场作用时的相应值显著增加,但试验钢显微硬度未发生明显改变。     

965 MPa级低合金Cr-Mo-V钢调质工艺优化实验研究

采取正交实验、极差分析等方法对Cr-Mo-V钢调质965 MPa级进行实验,研究淬火及回火工艺对组织及力学性能的影响。实验结果表明:Cr-Mo-V钢经910 ℃淬火,660 ℃+120 min回火后力学性能和韧性匹配最佳;在实验钢的力学性能中,强度和延伸率的主要影响因素为回火温度,冲击韧性的主要影响因素为回火时间;在回火温度660 ℃+保温60 min时,碳化物开始析出,且碳化物的析出量随回火时间的增加而增加。由于在析出物中有许多细小弥散分布的碳化物,并且尺寸适中、圆整度高、均匀分布,减小了冲击时的应力集中,因此韧性得到提高;当回火时间到180 min,析出的碳化物开始聚集长大,韧性略有下降。     

低合金高强钢焊缝金属针状铁素体的高温回火性能研究

采用OM、SEM、EBSD、TEM等表征技术,并结合拉伸、冲击和硬度测试等手段,对低合金高强钢焊缝金属中针状铁素体经640℃高温回火前后的显微组织和力学性能进行研究,并借助热力学计算,探讨了针状铁素体回火组织稳定性的微观机制。结果表明,低合金高强度钢焊缝金属经不同时间高温回火后,组织均由体积分数约90%的针状铁素体和少量晶界铁素体构成,无明显的晶粒粗化现象,保持了针状铁素体基体的高位错密度。在回火1 h后,焊缝金属的强度和硬度显著提高;随着回火时间的延长,其强度和硬度略有下降,但整体仍维持在较高水平,这主要归因于短时回火(不超过2 h)期间,大量碳化物的析出产生了显著的析出强化作用;随着回火时间延长,析出物的类型和数量变化不大,这与热力学计算结果相吻合。     

均热时间对含Ti、Nb微合金元素高强钢固溶规律的影响

采用相分析和X射线衍射技术,研究了含Ti、Nb等微合金元素的高强钢中碳氮化物的溶解行为. 结果表明,加热到1 250 ℃,未均热时,主要是面心立方结构的Ti(CN)、(TiNb)(CN)、TiC析出相;均热时间为45 min,部分Ti和Nb继续溶解,析出相转为Ti(CN)、TiC为主,平均颗粒尺寸由300 nm增大为323 nm,此时Ti、Nb固溶已经达到平衡,固溶率分别为64.2%和85.8%. 当保温80 min时,析出相含量基本没有变化,但颗粒尺寸有所增加.     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

Features of Women's language

Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women＇s language from these perspectives： pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women＇s language, more attention should be paid to language use in social context. What＇s more, the linguistic phenomena in a speaking community can be understood more thoroughly.     

An Analysis of Catherine＇s Character——Wuthering Heights

Wuthering Heights, Emily Bronte＇s only novel, was published in December of 1847 under the pseudonym Ellis Bell. The book did not gain immediate success, but it is now thought one of the finest novels in the English language. Catherine is the key character of this masterpiece, because everybody and everything center on her though she had a short life. We can understand this masterpiece better if we know Catherine well.     

Lower Paleozoic oil relationships within Williston Basin, Canada

The Williston Basin is a significant petroleum province, containing oil production zones that include the Middle Cambrian to Lower Ordovician, Upper Ordovician, Middle Devonian, Upper Devonian and Mississippian and within the Jurassic and Cretaceous. The oils of the Williston Basin exhibit a wide range of geochemical characteristics defined as "oil families", although the geochemical signature of the Cambrian Deadwood Formation and Lower Ordovician Winnipeg reservoired oils does not match any "oil family". Despite their close stratigraphic proximity, it is evident that the oils of the Lower Palaeozoic within the Williston Basin are distinct. This suggests the presence of a new "oil family" within the Williston Basin. Diagnostic geochemical signatures occur in the gasoline range chromatograms, within saturate fraction gas chromatograms and biomarker fingerprints. However, some of the established criteria and cross-plots that are currently used to segregate oils into distinct genetic families within the basin do not always meet with success, particularly when applied to the Lower Palaeozoic oils of the Deadwood and Winnipeg Formation.     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.     

Design and analysis of generic LBS application developing platform

Location based services is promising due to its novel working style and contents.A software platform is proposed to provide application programs of typical location based services and support new applications developing efficiently. The analysis shows that this scheme is easy implemented, low cost and adapt to all kinds of mobile nework system.     

Achieving Unusual States of Matter Under High Pressure

正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula-     

Exchange-Correlation and Electronic Excitation Energies from Pairing Matrix Fluctuations

We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re-     

Density Functional Theory for the Response of Periodic Systems to Electric Fields Based on the Vector Potential Approach

正The electronic and nuclear(structural/vibrational)response of 1D-3D nanoscale systems to electric fields gives rise to a host of optical,mechanical,spectral,etc.properties that are of high theoretical and applied interest.Due to the computational difficulty of treating such large systems it is convenient to model them as infinite and periodic(at least,in first approximation).The fundamental theoretical/computational problem in doing so is that