置氢Ti-6Al-4V合金组织演变与超塑性能

应用高温拉伸实验研究了氢对Ti-6Al-4V合金超塑变形行为的影响,借助于OM、SEM、TEM和XRD等分析手段,分析了氢对钛合金组织演变的影响. 结果表明:氢可促进合金中β相数量的增加,氢质量分数达到0.2%时合金出现马氏体组织,并随着氢含量的增加而逐渐粗化;适量的氢可以改善钛合金超塑变形行为,如降低流动应力和超塑变形温度、提高应变速率敏感指数m值;Ti-6Al-4V合金加入质量分数0.1%的氢,其峰值流动应力降低53%,变形温度降低约60℃,且由于氢的加入,使得超塑变形后的位错密度减少,说明氢促进了位错的运动.     

Ti-6Al-4V钛合金长寿命疲劳试验

研究了Ti-6Al-4V在室温空气环境下的疲劳性能,获得疲劳寿命为107下的Goodman曲线.结果表明,用简化的Goodman直线代替Goodman曲线对于Ti-6Al-4V钛合金偏于保守.对断口形貌的观察表明应力比R在0附近时裂纹萌生于内部,而当应力比接近-1和1时裂纹萌生于表面.另外,研究了估算Ti-6Al-4V在不同应力比的疲劳强度估算公式,得出Ti-6Al-4V厚板和挤压件缺口试样估算公式的系数,分别为1.422和1.042.     

氢在无序态和有序态Ni3Fe合金中的扩散行为

采用电解渗氢的方法研究室温下氢在无序态和有序态Ni₃Fe合金中的扩散行为.研究结果表明,在相同渗氢温度下,渗氢后的Ni₃Fe合金的延伸率随渗氢时间的增加而降低,拉伸断口上的沿晶断裂区(IG)的深度随渗氢时间的增加而增加;在相同渗氢时间下,合金拉伸断口上的沿晶断裂区的深度随渗氢温度的增加而增加.沿晶脆性断裂区的深度与渗氢温度和时间的关系符合菲克扩散方程的解.时间滞后法计算结果表明,氢在无序态Ni₃Fe合金中的表观扩散系数高于在有序态合金中的表观扩散系数.氢在无序态和有序态Ni₃Fe合金中的扩散激活能分别为44.9 kJ/mol和29.5 kJ/mol.     

Ti-6Al-4V合金置氢动力学与氢分布规律

通过Ti-6Al-4V合金750℃条件下的置氢实验,分析了置氢过程的动力学规律,利用光学金相显微镜和二次离子质谱仪研究了保温时间对氢分布的影响规律.结果显示,Ti-6Al-4V合金置氢动力学遵循二维扩散机制,满足Valensi方程g(α)=α+(1-α)ln(1-α),氢在试样径向方向的二维扩散是置氢反应的控制步骤.置氢保温时间大于60min时,氢压趋于稳定,氢在试样径向方向的二维扩散停止,试样中心的微观组织和氢离子强度与边缘的相一致,氢均匀分布于试样当中.     

形变TZM合金的拉伸性能和断口组织

采用粉末冶金方法制备出TZM合金并进行热轧处理,测试不同变形量TZM合金的拉伸性能,分析显微组织和断口形貌.结果表明,TZM合金无论变形与否拉伸断裂均含有沿晶脆性断裂;TZM合金随变形量的增加,加工态纤维组织增多,力学性能增强,断裂表现为由沿晶脆性断裂、解理断裂和穿晶解理断裂向沿晶韧性断裂和准解理断裂转变;随变形量的增加,TZM合金的碳化物相分散均匀、弥散度提高,晶界结合力增强,从而TZM合金的力学性能得以提高.     

铸态铝镁钪合金的热塑性

采用半连续铸锭冶金法制备一种成分为Al-6Mg-0.4(Sc+Zr)的合金,铸锭样品经均匀化退火后,测试其在250,300,350,400,450,475和500 ℃时的瞬时拉伸力学性能,借助扫描电镜(SEM)和透射电镜(TEM)的观察和分析,研究该合金的高温变形及断裂行为.结果表明:合金抗拉强度和屈服强度随温度的升高而降低,而其伸长率随温度的升高而增大;合金在300 ℃以下拉伸,断口为穿晶断裂型;在300 ℃以上拉伸,断口由穿晶断裂逐步向沿晶断裂转变;在400 ℃以上拉伸,断口基本上是沿晶断裂.在400 ℃以上变形,晶界区域有大量的强滑移带;在400 ℃以上晶内强度高于晶界强度,拉伸时变形优先在晶界区域发生,变形不均匀的结果导致铸坯热加工过程中开裂.Al-6Mg-0.4(Sc+Zr)合金铸坯的最佳热加工温度范围为350～400 ℃,在此条件下,合金的变形抗力较低,热塑性较好,又不出现热裂纹.     

Ti-6Al-4V合金电弧熔丝增材的组织性能研究进展

Ti-6Al-4V钛合金具有密度低、高温下组织稳定、强度高的特点,被广泛应用于机翼翼梁、起落架支撑肋等航空工业关键零部件的制造。电弧熔丝增材技术研究始于20世纪80年代,该技术具有成型效率高、原材料利用率高、设备简单等优势。目前,学界对Ti-6Al-4V合金电弧熔丝增材技术开展了广泛研究并已取得一定成果。笔者综述了电弧熔丝增材制造技术的发展历史及研究热点,并整合了国内外Ti-6Al-4V合金电弧熔丝增材技术的最新研究及应用情况,对电弧熔丝增材制造Ti-6Al-4V合金的组织性能特性及调控工艺进行了总结与展望。     

Cr和Mn元素强化的α钛合金的制备及其组织性能

在前人已经优化评估的Ti-Al-Cr-Mn四元热力学数据库的基础上,设计了一种新型α钛合金Ti-6Al-3Cr-1Mn,并利用分瓣式水冷铜坩埚成功制得了该合金。该合金在770℃下经轧机轧制成6mm厚的板材,然后于750℃保温90min进行真空退火热处理,出炉后置于空气中冷却。通过组织观察,发现无论是铸锭还是退火后的板材,室温下均为α型钛合金,与设计相符。室温力学性能试验表明,Ti-6Al-3Cr-1Mn合金的力学性能良好,平均屈服强度为894.9MPa,抗拉强度为926.7MPa,断后延伸率为15.2%。Ti-6Al-3Cr-1Mn合金与典型的α型钛合金TA15相比,室温强度相当,但塑性更好,成本更低。Ti-6Al-3Cr-1Mn合金的自腐蚀电位为-0.21V,自腐蚀电流密度为7.7×10-7 A·cm-2,耐腐蚀性能良好。     

置氢TC4粉末模压成形-烧结后的组织性能

采用置氢TC4钛合金粉末室温模压成形+保护气氛下烧结工艺,研究了置氢TC4合金粉末模压成形-烧结后合金组织性能的变化规律.结果表明:随着置氢量的增加,置氢TC4合金粉末模压成形烧结体致密度基本呈现逐渐增高趋势,模压成形烧结体由魏氏体组织向双态的过渡状组织转化,模压成形烧结体退火后组织较退火前发生了明显的破碎和细化;烧结体退火后压缩屈服强度基本呈逐渐增大趋势,且烧结体真空退火后氢含量可达到安全状态,其中,置氢量0.42%(质量分数)TC4合金粉末烧结体致密效果好、综合力学性能高.     

基于摩擦和温度修正的Ti-6Al-4V钛合金热变形本构模型建立

Ti-6Al-4V是民航客机应用最广泛的中高强度钛合金, 在锻造领域, 数值模拟准确性依赖于高准确度的材料模型. 本工作基于热压缩模拟方法, 在不同变形温度（750、800、850、900和950 ℃）和应变速率（0.001、0.01、0.1、1和5 /s）下, 针对变形量为60%的Ti-6Al-4V合金, 考虑鼓度因素影响, 对真实应力-真实应变曲线进行了摩擦和温度修正, 并进一步构建了该工况条件下的本构模型. 对比实验结果, 修正后的流变应力值低于实际测量值, 且随着应变量和应变速率的提高、变形温度的降低, 二者之间的差值也逐渐增大. 本工作分别建立了Ti-6Al-4V双曲正弦式以及用Z参数表达的材料本构模型. 真实应力应变曲线的摩擦和温度修正对提高材料模型的准确性具有指导意义, 同时对提高数值模拟精度具有参考价值.     

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.     

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     

Call for Papers

<正>"The Journal of Shanghai Normal University:Mathematics"is published by Shanghai Normal University as regular issues of The Journal of Shanghai Normal University each year from 2014 in English.The editors-in-chief of the issues are professors Yuhao Cong and Maoan Han.The Journal of Shanghai Normal University was started in 1958 with     

Journal of Donghua University ( English Edition) Contents of Volume 31

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