Mg-Sn合金化与固溶-时效行为的研究现状

作为具备良好发展前景的可时效强化镁合金,Mg-Sn合金通过Mg₂Sn相析出强化、固溶强化与细晶强化获得了优异的性能。与Mg-Zn、Mg-Al主要镁合金相比,Sn在Mg中的固溶度较好,析出强化效果优异;另外,Mg₂Sn相的熔点高达771.5 ℃,使Mg-Sn合金成为非稀土系列的低成本耐热镁合金。从合金化、固溶-时效处理工艺分析总结了可时效强化Mg-Sn合金的研究进展,分析Mg-Sn合金时效行为的重要参数及其影响因素,主要目的为细化Mg₂Sn析出相或增加Mg₂Sn析出相数量;同时,对添加到Mg-Sn合金中的合金元素的固溶效果、细晶效果与形成三元强化相效果进行系统总结与分析,为Mg-Sn合金成分的设计和性能改善提供重要参考。     

Al涂层/AZ91镁合金复合铸造界面的研究

对型芯预喷涂一层Al涂层,将AZ91镁合金液浇注到铸型中实现基体和涂层的结合,对凝固后的结合界面组织和相组成进行分析。结果表明,AZ91镁合金液和Al涂层表面的氧化物发生反应,实现了界面间的润湿,形成冶金结合界面。该界面包含3个扩散层:镁合金基体一侧为(Al₁₂Mg₁₇+δ_Mg)共晶组织;中间层为Al₁₂Mg₁₇金属间化合物;Al涂层一侧为Al₃Mg₂金属间化合物,并弥散分布着一些氧化物。试验结果证明,通过复合铸造的方法可以实现Al涂层和镁合金基体的冶金结合。     

机械合金法制备高生物相容性镁基非晶合金粉末

选择具有高生物相容性的Mg₆₅Zn₃₀Ca₃Si_1.766Zr_0.234合金体系作为研究对象,从原料单质粉末开始,采用雾化制粉、球磨制得该合金的非晶粉末,再通过X射线衍射（XRD）、差示扫描量热法（DSC）、电化学测试等手段,研究了球磨所制得粉末的非晶程度、非晶合金的热力学性能以及该体系镁基非晶合金的耐腐蚀性能.研究表明,经过80 h以上的球磨,可以使该体系下的镁基合金完全转变为非晶态,并且其耐腐蚀性能在相同情况下较ZK61晶态合金更为良好.     

Mg-3.0Li-2.0Al-2.0Sn-1.0Y-0.5Er合金力学性能与组织演变

为了提高合金的力学性能,通过微合金化的方法设计了一种新型超轻Mg-3.0Li-2.0Al-2.0Sn-1.0Y-0.5Er合金,通过熔铸、均匀化、多向锻造和异步轧制工艺获得了细晶镁合金板材。采用光学显微镜、X射线衍射仪、扫描电子显微镜、能谱仪等表征手段研究了合金微观组织的演变,利用拉伸试验机测试了合金变形前后的室温拉伸性能,研究了不同状态下合金的力学性能,讨论了合金力学性能与微观组织转变的影响因素。结果表明,在铸态Mg-3.0Li-2.0Al-2.0Sn-1.0Y-0.5Er合金中存在着α-Mg基体和Mg₂Sn、AlLi、Al₂Y和Al₂Er等第二相颗粒,多向锻造和异步轧制组合工艺有效地细化了Mg-3.0Li-2.0Al-2.0Sn-1.0Y-0.5Er合金的晶粒,使合金的平均晶粒尺寸减小到7.15 μm,室温下的抗拉强度、屈服强度和伸长率分别提高至255 MPa、220 MPa 和24.9%。     

Mg-Zn-Ce非晶合金力学与耐蚀性能的研究

镁合金作为生物可降解材料具有很多优势,但传统多晶镁合金腐蚀速率过快的问题限制了其更广泛的应用。与多晶镁合金相比,非晶态镁合金因具有独特的无定形结构,使其耐腐蚀能力比多晶镁合金的要好。采用铜辊甩带法制备得到了新型Mg_70−xZn₃₀Ce_x（x=2, 4, 6和8）非晶镁合金,并对其进行了力学性能和耐腐蚀性能的研究。结果表明：x为4和6时,Mg-Zn-Ce非晶合金的非晶形成能力最好;Ce的添加可以有效改善镁基非晶合金的脆性,使其弹性模量低于60 MPa,与人骨相似,从而能有效避免植入后因弹性模量过大导致的应力遮蔽效应的产生;同时,Ce的添加显著地提高了合金的耐腐蚀性,使其开路电位达到-0.2 V,腐蚀电流密度低至10^-6 A/cm²。     

变形量对(CoNiV)97Al3中熵合金组织和力学性能的影响

高强度和高塑性的中熵合金,相较于传统合金能够满足更多的实际应用。通过在CoNiV合金中掺入微量Al,经过退火处理来提高其力学性能。制备了不同Al含量的铸态(CoNiV)_100-xAl_x（x为1、2、3、4、5,原子分数/%）合金。采用万能试验机、维氏硬度计、X射线衍射仪、光学显微镜、扫描电子显微镜、透射电子显微镜,研究了退火温度、Al含量及拉伸变形量对合金力学性能、显微组织的影响。实验结果表明,随着Al含量的增加,合金的伸长率提升到30%以上,维氏硬度从755.8降低到375.6。经过1 000 ℃退火处理后的合金达到更高的强度?塑性平衡,伸长率可达到35%以上,拉伸屈服强度较高（超过950 MPa）。实验选择(CoNiV)₉₇Al₃（Al3）中熵合金作为研究对象,将系统分析拉伸变形量（50%、100%）对Al3合金微观组织及力学性能的影响。Al3合金在拉伸变形过程中,位错滑移主导变形,孪晶增加位错存储量,促进位错滑移堆积,该合金变形?断裂过程的主要为位错与孪晶的协同作用。     

Mg含量对可降解Zn-Ag-Mg合金的微观组织、力学性能、耐蚀性及细胞毒性的影响

制备了不同Mg含量的铸态Zn-5Ag-xMg(x=0,0.5,1,1.5,质量分数/%)合金。采用X射线衍射仪、光学显微镜、扫描电子显微镜、万能试验机、维氏硬度计、电化学工作站和CCK-8（Cell Counting Kit-8 试剂）等,研究了Mg含量对合金的显微组织、力学性能、耐蚀性能和细胞毒性的影响。结果表明,Zn-5Ag合金的第二相为ε-AgZn₃,而Mg的加入细化了合金的晶粒并新生成了Mg₂Zn₁₁相。随着Mg含量的增加,合金的抗压屈服强度从218 MPa提高到309 MPa,维氏硬度从71.4提高到131.9。电化学测试和体外浸泡实验表明,由于Mg含量的增加导致合金的耐蚀性能下降,体外降解速率由0.08 mm/a提高到0.16 mm/a。细胞毒性结果表明,Mg的添加可以提高小鼠胚胎成骨细胞（mouse embryonic osteoblasts cells,MC3T3-E1）的活力,所有合金表现出良好的生物相容性。     

静态再结晶处理对Co36Fe36Cr18Ni8Ti2合金力学性能与耐腐蚀性的影响

对冷变形后的Co₃₆Fe₃₆Cr₁₈Ni₈Ti₂合金在700 ℃和800 ℃下再结晶退火,制备成具有高强度及良好耐蚀性的多主元合金。采用电子背散射衍射（electron back-scattered diffraction, EBSD）表征了合金的相分布、再结晶组织以及晶界分布等微观结构特征,采用静态拉伸试验测试了合金的力学性能。结果表明,700 ℃退火的合金断后伸长率较低,但其抗拉强度与屈服强度分别达到了1 038和956 MPa。采用电化学工作站与扫描电子显微镜（scanning electron microscope, SEM）表征了合金在模拟体液中的耐蚀性。结果表明,700 ℃退火的样品具有较好的耐蚀性,腐蚀后的样品表面较为均匀。结合力学性能可知,700 ℃退火的样品具有作为新型医用金属材料的潜力。     

轧制处理对生物医用Zn-Mg合金组织和性能的影响

采用金相显微镜、X射线衍射仪、扫描电子显微镜、万能材料试验机和电化学工作站等设备,分析和研究了轧制变形对生物医用Zn-Mg合金的显微组织及力学性能的影响。结果表明：铸态、轧制态的合金均由Zn和Mg₂Zn₁₁两相组成;在轧制变形过程中,物相未发生改变,抗拉强度逐渐提高,伸长率先提高后降低,耐腐蚀性能逐渐下降;随着轧制变形量的增加,晶粒沿轧制方向的变形程度逐渐增大,直至出现纤维状组织。在相同的退火条件下,轧制变形量越大的Zn-Mg合金,再结晶晶粒尺寸越细小、均匀。     

多向锻造道次对Mg-5.21Li-3.00(Al-Si)-2.16Sn-1.90Y-0.93Er合金组织性能的影响

为了提高镁锂合金强度,采用多向锻造制备了一种新型Mg-5.21Li-3.00(Al-Si)-2.16Sn-1.90Y-0.93Er合金,采用光学显微镜、X射线衍射仪与拉伸试验机研究其组织与性能。研究表明：多向锻造可以有效提高该合金的综合力学性能。通过拉伸实验可知,该合金经过9道次多向锻造,极限抗拉强度、屈服强度、伸长率分别为239 MPa、165 MPa、26.2%。经过9道次的多向锻造后实现最佳晶粒细化,9道次下的晶粒尺寸同铸态相比细化了95%。在多向锻造后的该合金中观察到D型和D+C型Portevin-Le Chatelier效应,并讨论了Portevin-Le Chatelier效应与孪晶之间的关系。X射线衍射分析表明,该合金在室温下存在α-Mg相、Al₂Y、AlLi、Mg₂Si和Mg₂Sn金属间化合物。     

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.     

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     

On the Thermodynamic Limit for Responses to Static Electromagnetic Fields

For molecular systems,the quantum-mechanical treatment of their responses to static electromagnetic fields usually employs a scalar-potential treatment of the electric field and a vector-potential treatment of the magnetic field.Although the potential for each field separately is associated with the choice of an(unphysical)origin,the precise choice of the origin for the electrostatic field has little consequences for the results.This is different for the