材料期刊网

NUMERICAL SIMULATION METHODS AND THEIR APPLICATION IN MATERIAL HOT-WORKING

J. T. Niu , H. T. Li , X. D. Meng and P. Karjaleinen 1) Analysis and Measurement Center , Harbin Institute of Technology , Harbin 150001 , China 2) Department of Mechanocal Engineering , The University of Oulu , Finland

金属学报(英文版)

With the development of modern science and technology, especially computer science, the numerical simulation method has been widely used in material hot-working. Mary achievements have been made in this field by using the numerical simulation method. The numerical simulation method, especially finite element method fully described in this paper.Applications of the numerical simulation method in material hot-working are also discussed. Finally, the future of the numerical simulation method is outlined.

关键词: numerical simulation , null , null

Effect of carbon addition on hydrogen storage behaviors of Li-Mg-B-H system

International Journal of Hydrogen Energy

Various carbon additives were mechanically milled with LiBH(4)/MgH(2) composite and their hydrogen storage behaviors were investigated. It was found that most of the carbon additives exhibited prominent effect on the host material. Among the various carbon additives, purified single-walled carbon nanotubes (SWNTs) exhibited the most prominent effect on the kinetic improvement and cyclic stability of Li-Mg-B-H system. Results show that LiBH(4)/MgH(2) composite milled with 10 wt.% purified SWNTs additive can release nearly 10 wt.% hydrogen within 20 mm at 450 degrees C, which is about two times faster than that of the neat LiBH(4)/MgH(2) sample. On the basis of hydrogen storage behavior and structure/phase investigations, the possible mechanism involved in the property improvement upon carbon additives was discussed. (C) 2009 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.

关键词: Hydrogen storage;Lithium borohydride;MgH(2);Carbon;Mechanical;milling;arc-discharge method;libh4;nanotubes;composites;hydride

Effect of Li(3)N additive on the hydrogen storage properties of Li-Mg-N-H system

Journal of Materials Research

The effect of Li(3)N additive on the Li-Mg-N-H system was examined with respect to the reversible dehydrogenation performance. Screening Study with varying Li(3)N additions (5, 10, 20, and 30 mol%) demonstrates that all are effective for improving the hydrogen desorption capacity. Optimally, incorporation of 10 mol% Li(3)N improves the practical capacity from 3.9 wt% to approximately 4.7 wt% hydrogen at 200 degrees C, which drives the dehydrogenation reaction toward completion. Moreover, the capacity enhancement persists well over 10 de-/rehydrogenation cycles. Systematic x-ray diffraction examinations indicate that Li(3)N additive transforms into LiNH(2) and LiH phases and remains during hydrogen cycling. Combined structure/property investigations suggest that the LiNH(2) "seeding" should be responsible for the capacity enhancement, which reduces the kinetic barrier associated with the nucleation of intermediate LiNH(2). In addition, the concurrent incorporation of LiH is effective for mitigating the ammonia release.

关键词: complex hydrides;improvement;mixtures;imides;amide;h-2

EFFECT OF HOMOGENIZATION TREATMENT UNDER AN ELECTRIC FIELD ON T_1 DISTRIBUTION AND MECHANICAL PROPERTIES OF 2091 Al-Li ALLOY

LIU Wei , CUI Jianzhong(Northeastern University , Shenyang , ChinaManuscript received 10 November 1994)

金属学报(英文版)

Homogenization treatment under an electric field increases the distributive homogeneity of the T1 precipitation and improves the yield strength of 2091 Al-Li alloy.

关键词: :homogenization treatment , null , null , null

CONGRATULATIONS TO PROF. T. KO'S 90th BIRTHDAY Editorial Board of ACTA METALLURGICA SINICA

金属学报(英文版)

关键词:

2099-T83/2060-T8异质Al-Li合金搅拌摩擦焊搭接界面结构与力学性能

刘奋军 , 傅莉 , 张纹源 , 孟强 , 董春林 , 栾国红

金属学报 doi:10.11900/0412.1961.2014.00297

采用搅拌摩擦焊(FSW)对厚度为2mm的2099-T83与2060-T8 Al-Li合金进行搭接.利用OM和SEM等分析技术探讨搅拌头转速和搅拌针长度对搭接接头界面结构与力学性能的影响.结果表明,2099-T83/2060-T8搭接接头焊缝区可观察到明显的结合界面,焊缝区显微硬度低于母材,且在热机影响区与焊核区的过渡区硬度最低.当搅拌头转速由600 r/min增加到800 r/min,且搅拌针长度由3.0mm减小至2.5mm时,界面形貌由光滑界面转变成“锯齿状”咬合界面,焊缝区结合界面形貌主要受搅拌针长度影响,“锯齿状”咬合界面搭接接头平均破坏载荷为654N.搭接接头均在底部母材2060-T8侧热机影响区与焊核区的过渡区断裂,断裂特征为韧-脆混合断裂.“锯齿状”咬合界面搭接接头经150℃,保温20 h人工时效处理后,焊缝区显微硬度有所提升,接头承载能力较未经人工时效处理的降低了20％,断口呈现脆性断裂模式.

关键词: 2099-T83 Al-Li合金 , 2060-T8 Al-Li合金 , 搅拌摩擦焊接 , 人工时效处理 , 界面形貌 , 接头强度

Enhanced Hydrogen Storage Properties of Li-Mg-N-H System Prepared by Reacting Mg(NH(2))(2) with Li(3)N

Journal of Physical Chemistry C

The Li-Mg-N-H system was prepared by reacting magnesium amide [Mg(NH(2))(2)] with lithium nitride (Li(3)N) and investigated with regard to the hydrogen storage properties. Our study shows that the present method is superior to the conventional route in enhancing the reversible dehydrogenation properties. Through optimizing the Li(3)N:Mg(NH(2))(2) ratio in the starting materials, the reversible capacity of U-Mg-N-H system increases to 4.9 wt %, 18% higher than that typically obtained from the Mg(NH(2))(2) + 2LiH mixture at 200 degrees C. Furthermore, increasing the Li(3)N:Mg(NH(2))(2) ratio is effective for mitigating the ammonia release from thus-prepared samples. Combined property/structure investigations indicate that the obtained enhancements should be ascribed to the effects of LiNH(2) and LiH that were in situ generated from the excess Li(3)N. LiNH(2) may promote the dehydrogenation reaction via seeding the reaction intermediate. The concurrently generated LiH acts as an effective ammonia trapping agent. These findings highlight the potential of "intermediate seeding" as a strategy to enhance the reversible hydrogen storage properties of metal-N-H systems.

关键词: complex hydrides;ultrafast reaction;amide;improvement;desorption;linh2;destabilization;mechanism;mixtures;imides

Li-Mg-N-H储氢材料储氢性能测试方法研究

裴增文 , 刘晓鹏 , 黄倬 , 李志念 , 王树茂 , 蒋利军

稀有金属 doi:10.3969/j.issn.0258-7076.2010.04.013

采用等容法研究了机械球磨工艺制备的Li-Mg-N-H材料储氧性能,结果发现,在室温下采用氦气对样品室体积进行标定时,由于Li-Mg-N-H材料对氦气有一定量的物理吸附,造成准确Li-Mg-N-H材料样品体积标定误差,进而造成Li-Mg-N-H储氢材料在503 K下放氢容量随压力的降低而增加异常变化.为准确标定样品体积,通过对Li-Mg-N-H材料室温氮气吸附容量测定,并采用迭代计算方法获得准确的储氢材料样品体积,进而测定Li-Mg-N-H储氢材料503 K下放氢PCT曲线,其表现为放氢容量随压力降低而减小的正常变化规律.Li-Mg-N-H储氢材料503 K,9.6 MPa氢压下的最大储氢容量为4.81%(质量分数),放氢过程表现为单一放氢平台特性.

关键词: 轻质储氢材料 , Li-Mg-N-H , 储氢性能 , 等容测试方法

组成对Li-Mg-N-H系统储氢性能的影响

秦董礼 , 赵晓宇 , 张轲 , 鲁捷 , 张洪波 , 辛士刚

稀有金属

研究了2种不同组成(2LiNH2-1.1 MgH2和Mg(NH2)2-2.2LiH)的Li-Mg-N-H储氢材料系统储氢性能,通过P-C-T曲线以及脱氢反应动力学的测定,发现这2种组成的样品脱氢产物均为Li2Mg(NH)2,其在200℃以上具有良好的可逆性,可逆储氢量可达4.6％(质量分数)以上;2种组成的系统不同仅在于前者多余MgH2而后者多余LiH,其对系统脱氢反应的热力学性质如焓变、熵变以及自由能改变不大,但多余MgH2的样品较多余LiH的样品,系统脱氢反应的动力学较快,具有较低的活化能.

关键词: Li-Mg-N-H系统 , P-C-T曲线 , 脱氢反应动力学 , 储氢性能

Enhanced H-storage property in Li-Co-N-H system by promoting ion migration

Journal of Alloys and Compounds

Motivated by the ion migration mechanism proposed by David et al. [J. Am. Chem. Soc. 129 (2007) 1594-1601], we mechanically mill the Li3N/Co powder mixture to obtain defective Li3N-type structure with enhanced Li+ mobility. Compared with Li3N the hydrogen storage property of such defective phase is markedly improved, presumably due to the ion-migration-enhancing effect from the incorporation of Co and Fe (from milling utensils). During subsequent cycling, however, this effect cannot persist due to the precipitation of Co-Fe alloy upon hydrogenation. The close correlation between Co-Fe incorporation/precipitation and property variation of Li3N hydrogen storage material provides a preliminary evidence to support the ion migration mechanism. (C) 2007 Elsevier B.V. All rights reserved.

关键词: Hydrogen absorbing materials;Nitride materials;hydrogen-storage;lithium amide;mechanism;nitride;batteries;mixtures;hydride;imides;linh2;anode