Al-1.98Li-1.78Cu-1.30Mg-0.10Zr合金微观组织、拉伸性能和断裂行为的研究

文中报道了对Al-1.98Li-1.78Cu-1.30Mg-0.10Zr合金组织、机械性能和断裂行为进行的研究。结果表明,合金在170℃/2h 190℃时效时有硬度双峰,屈服强度和抗拉强度也有类似的双峰,这主要是由δ′(Al_3Li)和S′(Al_2CrMg)的析出引起的。合金的强化相为δ′,S′和T_1(Al_2CuLi)。在欠时效阶段,析出的主要是δ′和少量沿位错析出的S′。在峰时效阶段,除析出δ′外,还有S′和T_1在基体中均匀析出,并且有晶间PFZ存在。拉伸试样的断裂以沿晶为主,但有少量由粗大第二相粒子诱发的韧窝存在于断裂表面上。     

快速凝固Al-Li-Cu-Mg-Zr合金的时效特征

本文采用力学性能试验和透射电镜分析相结合的方法,探讨了一种快速凝固(RS)Al-2.28Li-1.70Cu-l.05Mg-0. 32Zr合金在时效处理中力学性能和微观组织变化的特征。结果表明:合金的硬度及强度在时效处理中会迅速达到峰值,延伸率却同时降至最低值。另外,析出相δ′(A1_3Li)很快长大,其直径与对应的时效时间的1/3次方成正比,无析出区(PFZ)在晶界产生并逐渐宽化,其宽度与时效时间的1/3次方成线性关系,过时效处理后一部分δ′相被“复合析出物”Al_3(Li,Z_r)所取代,在晶界或位错等处还析出S′(Al_2CuMg)相。     

1460铝锂合金的力学性能与微观组织

采用金相观察、拉伸性能测试及透射电镜分析等手段研究1460铝锂合金的铸态组织、薄板T6态单级时效(160℃)及T8态双级时效(5%预变形,130℃+160℃时效)处理时力学性能及微观组织的演化。研究结果表明:添加微量Sc元素时,凝固时形成Al_3(Sc,Zr)初生相粒子,1460铝锂合金铸锭树枝晶组织被消除,晶粒呈等轴状,粒度较小(20~50mm);而冷轧薄板固溶处理后为细小的带状晶粒组织;1460铝锂合金主要时效析出强化相为d′相(Al_3Li),其次为T1相(Al_2Cu Li),但在时效过程中可能形成q″(q′)(Al_2Cu)过渡相;在时效过程中,时效前期快速析出d￠相;随时效时间延长,d′相长大,并析出q￠￠(q′)过渡相;随着时效时间进一步延长,T1相析出,而q″(q′)过渡相消失;与T6态时效相比,T8态时效时T1相尺寸降低但密度增大,强度提高。     

预时效对高强铝锂合金2A97组织和性能的影响

以高强Al-Cu-Li-X铝锂合金2A97为研究对象,采用拉伸试验、TEM和SEM等手段测试分析了带有预时效双级时效合金组织和性能.结果表明:淬火后的双级时效和淬火变形后的双级时效,由于在终时效前增加预时效,使合金塑性提高,但强度略有下降.淬火变形后预时效过程形成的位错环和变形导致的位错有相同的作用,增加基体T1(Al2CuLi)相数量,使T1分布更均匀,淬火变形后双级时效获得T1,θ′和δ′的混合组织,同时预时效减小晶界T1尺寸.淬火后预时效导致的空位团和位错环增加基体δ′和T1形核,但数量有限,预时效有利于促进溶质原子团簇形成,增加δ′(Al3Li)和θ″(Al2Cu)析出相形核,并有利于...     

时效处理对新型超高强Al-Cu-Li-X合金薄板的力学性能和微观组织的影响

通过力学性能测试和透射电镜(TEM)观察研究热处理制度对新型超高强Al-Cu-Li-X合金2 mm厚薄板的力学性能和微观组织的影响。研究结果表明:T8态较T6态时效的合金具有更高的强度和更好的塑性;超高强铝锂合金的时效析出相包括大量T1相(Al2Cu Li)、较多的θ′相(Al2Cu)、一定的δ′相(Al3Li)以及极少量S′相(Al2Cu Mg);T8态时效时引入预变形抑制δ′相和S′相形成,同时促进T1相和θ′相形核析出,但对θ′相的作用效果小于对T1相的作用效果;当预变形量为6%~8%时,合金能获得较高的强度与伸长率,8%预变形后峰时效时拉伸强度达616 MPa,伸长率达12%。     

8090A1合金的时效析出

本文研究了8090铝合金(Al-Li-Cu-Mg-Zr)时效过程中的δ′相和PFZ(无析出区)长大规律,发现它们与时间的1/3次方成正比。同时讨论了时效对变形机制的影响,即位错从切过δ′相到绕过的转变;并讨论了时效对材料塑性的影响及其原因。     

1420铝锂合金回归再回火析出δ′相行为

采用小角X射线散射技术研究了回归再回火处理1420铝锂合金δ′相的形成和粗化. 结果表明, 再回火5 h析出的δ′相与基体之间存在过渡区， 该过渡区经再回火48 h处理后消失; 之后δ′相粒子的粗化是通过互相吞并形成的.     

热处理对CuNi2Si合金组织和性能的影响

研究了不同预冷变形条件下时效温度及时间对CuNi2Si合金组织和性能的影响.结果表明:合金在880 ℃×2.5 h固溶,经不同预冷变形后时效,具有较强的时效强化特性;同时预冷变形能够促进时效过程中第二相的析出,并具有晶界析出倾向;当预冷变形达40%,500 ℃×1 h时效,合金布氏硬度(HB)达193,抗拉强度(R_m)达765 MPa,伸长率达11%,与未进行预冷变形的合金相比,可获得较高的硬度、强度及较好的综合性能.合金热处理后的拉伸断口为韧性断裂,形貌特征为沿晶型韧窝,这与析出相具有晶界析出倾向的特性一致.     

2A66铝锂合金时效行为的研究

通过DSC分析、硬度测试、拉伸测试、SEM和TEM检测等手段,研究了2A66铝锂合金时效组织和性能的变化.研究结果表明:对于同一时效温度,随着时效时间的延长,强度出现峰值;时效温度越高,出现峰值的时间越短.2A66铝锂合金最佳的峰值时效制度为165℃保温64h,此时合金获得了良好的强塑性结合,硬度为146 HB,抗拉强度为526.5MPa,屈服强度为448.9 MPa,延伸率为10.1%.165℃时效过程中合金的主要强化相为δ',θ'和T_1相,时效初期合金的主要强化来源为GP区、δ'和θ'相,峰值时效时合金的主要强化相为θ'和T_1相.     

热暴露过程中7050铝合金的微观组织与性能的研究

采用透射电子显微镜和拉伸实验研究了不同热暴露条件下7050-T7651铝合金微观组织和拉伸力学性能.结果表明：未经热暴露的7050-T7651铝合金中主要析出相为Guinierprestonzone（GP区）和η′相,其中η′相与基体的取向关系为[0001]η′//[11]Al,（100）η′//（110）Al.随后7050-T7651铝合金在不同温度下分别热暴露500h,随着热暴露温度的提高,合金中析出相长大越明显,晶界附近无沉淀析出带（PFZ）宽化也越明显 热暴露温度提高,合金强度下降越多.7050-T7651铝合金经过长时间热暴露后强度下降、塑性提高的主要原因是晶内主要强化相GP区和η′相的长大粗化以及晶界附近无沉淀析出带（PFZ）宽化.     

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