QUASICONTINUUM METHOD SIMULATION OF THE INITIAL PLASTIC DEFORMATION OF SINGLE CRYSTAL Cu IN NANOINDENTATION

采用准连续介质方法模拟了纳米压痕实验中单晶Cu初始塑性变形过程. 采用3种不同宽度的纳米尺度压头, 得到了载荷-压痕位移关系曲线, 确定了 3种不同宽度压痕下位错发射的临界载荷. 临界载荷的大小与能量理论的预测结果基本一致. 通过对压头下方位移场的分析, 揭示了加载过程中位错形核的力学特征和微观结构特征; 得到了压头下方几何必需位错密度增加的一般规律. 定性地分析了卸载过程中位错的运动与湮灭.     

纳米压痕过程的多尺度模拟与Rice-Thomson位错模型分析

采用多尺度准连续介质法（简称QC方法）对单晶Ag薄膜纳米压痕过程进行模拟,研究压头宽度对纳米压痕过程中接触应力分布、位错形核临界载荷以及纳米硬度的影响,并用Rice-Thomson位错模型（简称R-T位错模型）进行分析。结果表明,纳米压痕获得的载荷-位移曲线呈现出的不连续性与位错之间的协同作用密切相关;压头尺寸对纳米压痕过程中接触应力分布、位错形核临界载荷以及纳米硬度具有明显的影响：随着压头宽度的增加,法向和切向接触应力以及纳米硬度值递减,呈现出明显的压头尺寸效应;而压头下方薄膜内位错形核临界载荷却递增,且与压头半宽度的平方根成正比。模拟结果与相应实验结果以及R-T位错模型计算结果吻合     

Size Effects at Dwell Stage of Micro-Indentation for Pure Aluminum

以工业纯铝L2为研究对象就微压痕试验过程中保压阶段的尺度效应进行研究。研究发现微压痕试验过程中有保压台阶的瞬间形成,即在达到最大载荷后的保压段,虽然载荷不变,但压入深度却在增加,保压平台的出现和保压时间的关联性不大。随后通过采用带内禀长度微塑性本构方程的有限元模拟,并引入折合材料内禀长度,将模拟结果与相同保压时间、不同载荷压痕试验过程中的尺度效应进行对比分析,并解释了微纳米压痕试验保压平台的反常规律,获得反映材料尺度效应的内禀长度为5.09μm,以及反映微纳米压痕保压阶段尺度效应的材料折合内禀长度为4.90μm,研究表明:保压平台的产生来源于保压阶段应变梯度的减小,相当于几何必需位错密度降低到保压前的96.27%,这种保压平台的形成机理和微纳米压痕试验过程中的几何尺度效应与载荷尺度效应有关。     

纳米压痕实验中单晶Cu初始塑性变形的准连续介质模拟

采用准连续介质方法模拟了纳米压痕实验中单晶Cu初始塑性变形过程．采用3种不同宽度的纳米尺度压头,得到了载荷压痕位移关系曲线,确定了3种不同宽度压痕下位错发射的临界载荷．临界载荷的大小与能量理论的预测结果基本一致．通过对压头下方位移场的分析,揭示了加载过程中位错形核的力学特征和微观结构特征;得到了压头下方几何必需位错密度增加的一般规律．定性地分析了卸载过程中位错的运动与湮灭．     

2Cr13钢高周疲劳微塑性损伤特性研究

研究了２Ｃｒ１３马氏体不锈钢高周疲劳载荷作用下微观塑性变形的演变过程。在三种选定循环载荷作用下,在疲劳裂纹萌生前试样一直处于弹性变形阶段,而且弹性模量基本不变。在１／２寿命时,普遍观察到局部微观塑性变形特征。有些板条内存在含扭折对的平行螺位错束或十字交叉网状位错组态,一些细长碳化物周围塞积了棱柱或滑移型位错环。达到疲劳寿命时,有些区域内形成位错胞状结构。经过高周疲劳实验的薄膜试样在透射电镜下进行动态拉伸原位观察结果表明,微裂纹易在细长碳化物处萌生,沿位错胞壁或板条界扩展后与主裂纹汇合。高周疲劳过程中局部微观塑性耗散造成一定程度的微观结构损伤,裂纹穿过这些区域只需消耗很少的塑性功     

基于分子动力学单晶硅的纳米压痕过程研究

基于分子动力学的基本理论,在微纳米尺度下建立了单晶硅的纳米压痕分子动力学模型。研究了在纳米压痕过程中单晶硅基体的变形机理、势能变化和温度变化。研究发现:在纳米压痕过程中基体上出现了位错、空位及滑移带,基体两侧有凸起现象。当压头撤离时,基体与压头间存在颈缩现象。在系统达到平衡时系统的势能出现不同,这是因为原子位错运动使得系统增加的势能小于压头原子所做的功。温度的变化与位错变形的程度相关,位错变形越剧烈系统温度升高的越快。     

亚微米厚铜薄膜的微观结构及疲劳损伤行为

在具有高弹性和力学稳定性的柔性基底上，用磁控溅射系统制备了亚微米厚铜薄膜，利用透射电镜（TEM）、扫描电镜（SEM）电子背散射成像及X射线衍射（XRD）对铜薄膜进行了微观结构表征．采用恒载荷幅控制研究了亚微米厚度铜薄膜的疲劳损伤行为．结果表明：退火后的铜薄膜呈现强烈的（111）织构，薄膜中存在大量的微米、纳米尺度孪晶．在恒载荷幅作用下，亚微米厚的薄膜不易产生疲劳挤出和微裂纹，疲劳裂纹容易在界面处萌生，孪晶附近的位错塞积及界面附近变形的不协调性导致了疲劳裂纹的产生．而亚微米厚铜薄膜疲劳强度的提高来源于薄膜厚度、晶粒尺寸和孪晶尺寸三个微尺度的约束．     

Al薄膜纳米压痕过程的多尺度模拟

采用多尺度准连续介质法分别模拟无缺陷和具有初始缺陷两种状态下,单晶Al薄膜纳米压痕初始塑性变形过程,得到载荷-位移响应曲线和应变能-位移变化曲线.研究了初始缺陷对纳米压痕过程中位错形核与发射、Peierls应力以及位错发射.临界载荷的影响.结果表明,在整个纳米压痕过程中出现了多次位错形核与发射现象,初始缺陷对第1和第3对位错的形核与发射影响较小,而对第2对位错的形核与发射具有明显的推迟作用,并伴随有裂纹扩展现象;由于初始缺陷引起薄膜材料内部严重的晶格畸变,导致系统应变能和位错运动的Peierls应力增加;裂纹扩展前,发射第2对位错需要的临界载荷增加,裂纹失稳后,位错发射需要的临界载荷下降.模拟获得的纳米硬度和Peierls应力与实验结果吻合.     

基于球面触点接触模式的铜膜纳观变形探析

对微机电系统金属铜膜接触变形特征的了解和位错原子迁演的寻迹对改善工况接触质量极为重要。基于分子动力学法,对球面触点与微器件铜膜的接触变形展开研究,分析铜膜力-位移曲线对应构型演变特征,用WSDA法描述接触变形特性,并比对触点轮廓对铜膜内、外表面的变形差异。研究表明:弹性接触时,力-位移曲线的Hertz理论与MD结果吻合,而接触区铜膜两侧的位错环凸显是塑性变形始发源与侧面滑移带产生的萌芽端,也是弹性阶段后的Hertz理论与MD的力-位移曲线不吻合主因。受载铜膜的位错原子会演化为位错环,位错环构型演变有4个动态阶段:位错环萌芽期、生长增大期、繁衍增殖期、维持稳定期。随着触点轮廓增加,位错环构型也相应扩张,而位错环演化4个阶段不受外围轮廓影响。另外,受载铜膜接触区两侧滑移带蔓延处的应力较集中,亚表层应力集中度强烈依赖于触点外围轮廓尺寸。验证了WSDA法可有效描述铜膜受载时的变形特征,并随触点轮廓增加而迅速向两侧蔓延传播,与受载铜膜的应力、应变趋势获得一致。研究结果将对微观金属弹塑性变形转化的微观临界态揭示中有着重要参鉴价值。     

基于分子动力学单晶硅的纳米压痕过程研究（英文）

基于分子动力学的基本理论,在微纳米尺度下建立了单晶硅的纳米压痕分子动力学模型。研究了在纳米压痕过程中单晶硅基体的变形机理、势能变化和温度变化。研究发现:在纳米压痕过程中基体上出现了位错、空位及滑移带,基体两侧有凸起现象。当压头撤离时,基体与压头间存在颈缩现象。在系统达到平衡时系统的势能出现不同,这是因为原子位错运动使得系统增加的势能小于压头原子所做的功。温度的变化与位错变形的程度相关,位错变形越剧烈系统温度升高的越快。     

新型的治疗阿尔茨海默氏症药物(1-二甲基磷酰基-2,2,2-三氯)-乙基-1-醇烟酸醋对体外神经细胞的作用

目的: 观察本实验室合成的一种治疗阿尔茨海默氏症(AD)的药物(1-二甲基磷酰基-2, 2, 2 -三氯)-乙基^-1-醇烟酸醋(NMF),对体外培养的皮层神经细胞活性的影响以及对海人藻酸(KA)所致的神经损伤的保护作用。方法: 采用体外培养皮层神经元的方法,解剖分离 15 d胚胎小鼠皮层神经细胞, 接种于 96孔板,48 h 后加药并培养 72 h,以 MIT 法 观察 NMF 对小鼠皮层神经细胞活性的影响;同时将接种于 24 孔板的细胞预先给予 NMF,d 3 时加或不加KA处理后,以台盼蓝染色鉴别并计数死、活细胞,可得出细胞的存活率。结果: NMF 明显促进胎鼠皮层神经元活性,其中 NMF1、0. 1、10nmol·L^-1促进神经元活性增殖率分别高达 34.7%、37.4%、36. 7%, NMF 明显促进正常胎鼠皮层神经元存活卒,与对照组比较,10nmol·L^-1 NMF 对皮层神经元的存活率分别提高 39.3%、73.5%。 NMF能显著 对抗 KA 所致的神经元损伤,与 KA 损伤组相比, NMF0.1、10、10nmol·L^-1对损伤皮层神经元的保护率分别为 77.30%、80.10%、84.15%。结论: NMF 明 显促进胎鼠皮层神经元的洁性、提高正常皮层神经元,的存活卒,并能有效地保护KA所致的神经元损伤,提示 NMF 是一种很有潜力的治疗 AD 的药物。     

Three-Dimensional Growth of Coherent Ferrite in Austenite: A Molecular Dynamics Study

Coherent second phase often exhibits anisotropic morphology with specifi c orientations with respect to both the second and the matrix phases. As a key feature of microstructure, the morphology of the coherent particles is essential for understanding the second-phase strengthening eff ect in various industrial alloys. This letter reports anisotropic growth of coherent ferrite from austenite matrix in pure iron based on molecular dynamics simulation. We found that the ferrite grain tends to grow into an elongated plate-like shape, independent of its initial confi guration. The fi nal shape of the ferrite is closely related to the misfi t between the two phases, with the longest direction and the broad facet of the plate being, respectively, consistent with the best matching direction and the best matching plane calculated via the Burgers vector content(BVC) method. The strain energy calculation in the framework of Eshelby's inclusion theory verifi es that the simulated orientation of the coherent ferrite is energetically favorable. It is anticipated that the BVC method will be applicable in analysis of anisotropic growth and morphology of coherent second phase in other phase transformation systems.     

Effect of Short-Time Aging on the Pitting Corrosion Behavior of a Novel Lean Duplex Stainless Steel 2002

The effect of short-time aging in the temperature range between 400 and 1000 °C on the pitting corrosion behavior and mechanical property of a novel lean duplex stainless steel(LDSS) 2002 was investigated through the potentiostatic critical pitting temperature(CPT) tests and the Charpy impact tests. Both the pitting corrosion resistance and the toughness of aged specimens degraded due to the precipitation of detrimental secondary phases and the most significant reduction of CPT and impact energy emerged at 650 °C concurrently. The CPT of LDSS 2002 specimen aged at 650 °C decreased by 28 °C, and the impact energy dropped from 69 to 29 J/cm~2 compared with the solution-annealed sample. Transmission electron microscopy characterization showed that the main precipitates in LDSS 2002 were Cr_2N and M_(23)C_6 along the ferrite–austenite grain boundaries.     

INTRODUCTION TO PATENTS

The invention provides a method of making a mold which can reduce SOx generation rate while preventing decrease in hardening rate in the case of using sulfuric acid for a hardener composition. The method has a mixture step in which fire-resistant particles, a hardener composition and a binder composition are mixed to obtain a composition for a mold. The hardener composition contains sulfuric acid. In the mixture step, sodium carbonate is added. A molar ratio of the sulfuric acid to the sodium carbonate is 0.5 or more and 4.0 or less.     

China Foundry Week 2014

China Foundry Week, hosted by the Foundry Institution of Chinese Mechanical Engineering Society （FICMES） each year, is a large academic event in China. It is one of the ten high-impact activities sponsored by the Chinese Mechanical Engineering Society.     

17th Conference of Hydrodynamic and Electromechanical Control Engineering Call for papers

正1.Contents In order to promote the academic exchanges and technical communication of the research in the field of fluid power transmission and control,fluid control engineering specialized committee of the Chinese Society of Theoretical and Applied Mechanics will hold the 17th Conference of Hydrodynamic and Electromechanical Control Engineering on July 27-29,2014 in Tibet,Lhasa city.     

Information for Contributors

正The Transactions of Nonferrous Metals Society of China,founded in 1991 and sponsored by The Nonferrous Metals Society of China,is published monthly now and mainly contains reports of original research which reflect the new progresses in the field of nonferrous metals science and technology,including mineral processing,extraction metallurgy,metallic materials and heat treatments,metal working,physical metallurgy,powder metallurgy,with the emphasis     

Preface

<正>We are pleased to present this Special Issue of Transactions of Nonferrous Metals Society of China containing selected papers from the First Asian Conference on Aluminum Alloys(ACAA-2013),held in Beijing,China,13–17 October 2013.This conference has been initiated,with approval of     

Information for Contributors

The Transactions of Nonferrous Metals Society of China, founded in 1991 and sponsored by The Nonferrous Metals Society of China, is published monthly now and mainly contains reports of original research which reflect the new progresses in the field of nonferrous metals science and technology, including mineral processing, extraction metallurgy, metallic materials and heat treatments, metal working, physical metallurgy, powder metallurgy, with the emphasis on fundamental science. It is the unique preeminent publication in English for scientists, engineers, under/post-graduates on the field of nonferrous metals industry. This journal is covered by many famous abstract/index systems and databases such as SCI Expanded, Ei Compendex Plus, 1NSPEC, CA, METADEX, AJ and JICST.     

Rheology Feature of Simple Metal Melt

The rheology feature of Sb, Bi melt and alloys was studied using coaxial cylinder high-temperature viscometer. The results showed that the curve of torsion-rotational speed for Sb melt presents a linear relation in all measured temperature ranges, whereas for the Bi melt, the curve presents obvious non-Newtonian feature within the low temperature range and at relative high shear stress. The rheology feature of Sb80Bi20 and Sb20Bi80 alloy melts was well correlated with that of Sb and Bi, respectively. It is considered that the rheology behavior of Sb melt plays a crucial role in Sb80Bi20 alloy and that of Bi melt plays a crucial role in Sb20Bi80 alloy.