材料期刊网

SELECTING CLUSTER MODEL IN Sn - BASED SOLDER ALLOY DESIGN WITH DV - X_α CALCULATION METHOD

C. Q. Wang and W. F. Feng National ho. of Advanced welding Technolgy , HIT , Harbin 150001 , China

金属学报(英文版)

Applying calculation method in alloy design should be an important tendency due to its characters of inexpensive cost, high efficiency and prediction. DOS calculations of AuSn, AsSn and SbSn Sn- based alloys have been investigated by employing DV - Xa method, in which different cluster models were adopted to calculate electron structure.It is proved that some regulations must be taken into ac- count in order to carry out alloy design calculation successfully,which are described in this paper in detail.

关键词: Cluster model , null , null , null

C_f/SiC复合材料与Ti合金的AgCuTi-W复合钎焊

熊进辉 , 黄继华 , 薛行雁 , 张华 , 赵兴科 , 林国标

航空材料学报 doi:10.3969/j.issn.1005-5053.2009.6.010

本文利用AgCuTi-W复合钎料作中间层,在适当的工艺参数下真空钎焊C_f/SiC复合材料与Ti合金,利用SEM,EDS,XRD分析接头微观组织结构,利用剪切试验检测接头力学性能.研究结果表明:钎焊时,复合钎料中的Ti借助Cu-Ti液相与C_f/SiC复合材料反应,在C_f/SiC复合材料与连接层界面形成Ti3SiC2,Ti3Si和少量TiC化合物的混合反应层.复合钎料中的Cu与Ti合金中的Ti发生互扩散,在连接层与Ti合金界面形成不同成分的Cu-Ti化合物过渡层.钎焊后,形成W颗粒强化的致密复合连接层,W颗粒主要分布在Cu-Ti相中.W的加入缓解了接头的残余热应力,C_f/SiC/AgCuTi-W/TC4接头剪切强度明显高于C_f/SiC/AgCuTi/TC4接头.

关键词: C_f/SiC , Ti合金 , 钎焊 , AgCuTi-W

Development of an advanced A-TIG (AA-TIG) welding method by control of Marangoni convection

Materials Science and Engineering a-Structural Materials Properties Microstructure and Processing

A new type of tungsten inert gas (TIG) welding has been developed, in which an ultra-deep penetration is obtained. In order to control the Marangoni convection induced by the surface tension gradient on the molten pool, He gas containing a small amount of oxidizing gas was used. The effect of the concentration Of O-2 and CO2 in the shielding gas on the weld shape was studied for the bead-on-plate TIG welding of SUS304 stainless under He-O-2 and He-CO2 mixed shielding gases. Because oxygen is a surface active element for stainless steel, the addition of oxygen to the molten pool can control the Marangoni convection from the outward to inward direction on the liquid pool surface. When the oxygen content in the liquid pool is over a critical value, around 70ppm, the weld shape suddenly changes from a wide shallow shape to a deep narrow shape due to the change in the direction of the Marangoni convection. Also, for He-based shielding gas, a high welding current will strengthen both the inward Marangoni convection on the pool surface and the inward electromagnetic convection in the liquid pool. Accordingly, at a welding speed of 0.75 mm/s, the welding current of 160 A and the electrode gap of I mm under the He-0.4%O-2 shielding, the depth/width ratio reaches 1.8, which is much larger for Ar-O-2 shielding gas (0.7). The effects of the welding parameters, such as welding speed and welding current were also systematically investigated. In addition. a double shielding gas method has been developed to prevent any consumption of the tungsten electrode. (c) 2008 Elsevier B.V. All rights reserved.

关键词: Weld shape;Oxygen;Helium;Marangoni convection;Electromagnetic;convection;Double shielding gas;gas tungsten arc;shape variations;oxide fluxes;penetration;parameters

Ho∶ BaY2F8晶体生长及其光谱研究

罗辉 , 亓鲁 , 朱世富 , 官周国 , 张志斌 , 曾彬 , 郭春艳

人工晶体学报

本文采用液相合成方法合成了掺钬氟化钇钡(分子式:Ho3+ ∶BaY2F8,简称Ho∶ BYF)多晶原料,使用提拉法生长了掺钬氟化钇钡(Ho∶ BYF)激光晶体,晶体生长参数:拉速0.5～1mm/h,转速10 r/min.XRD测试表明:该晶体属于单斜晶系,空间群C2/m.测试了晶体的吸收及荧光光谱,同时计算了Ho离子对889nm泵浦光的吸收系数及吸收截面,分别为4.84 cm-1、1.26× 10-21 cm2.该吸收对应于Ho3+从基态5I5到激发态5I6的跃迁,可实现3.9 μm激光输出.

关键词: 晶体生长 , 氟化钇钡 , 荧光光谱

A_2W_3O_(12)(A=Y, Er, Ho, Yb)型稀土钨酸盐的高温XRD研究及结构精修

黄远辉 , 杨海涛 , 尚福亮 , 吴国根 , 汪晓

稀有金属材料与工程

用高温固相反应法制备出A_2W_3O_(12) 型稀土钨酸盐材料(A=Y,Er,Ho,Yb),用室温及高温XRD测定其在不同温度下的结构、晶胞参数及晶胞体积,并用TOPSA软件对其结构进行精修.发现除HO_2W_3O_(12)外,都具有较大的负热膨胀系数.据A. W. Sleight预测,HO_2W_3O_(12)具有较大的负热膨胀特性,但本实验却发现它并没有负热膨胀性,反而具有非常大的正热膨胀系数.

关键词: 稀土钨酸盐 , 高温XRD , HO_2W_3O_(12)

AN UNIDENTIFIED MAGNETIC TRANSITION IN R2FE14X COMPOUNDS (R = SM, TB, DY, HO, ER, AND TM - X = B OR C)

Journal of Applied Physics

In Ho2Fe14B and Ho2Fe14C the temperature dependence of the ac initial susceptibility between 4.2 and 300 K shows two peaks. The peak at the lower temperature can be explained by a well-known spin reorientation transition (at 62 K for Ho2Fe14B and at 40 K for Ho2Fe14C). The peak at the higher temperature (at 245 K for Ho2Fe14B and at 265 K for Ho2Fe14C) disappears when the external field is applied parallel or perpendicular to the preferential direction of a magnetically aligned sample. The similar peak was also traced for R2Fe14X compounds (R = Sm, Tb, Dy, Ho, Er, and Tm; X = B or C). Searching for the nature of this peak traced by measuring the temperature dependence of the ac susceptibility for 3d-4f compounds is still under progress.

关键词:

THE CHANGING ROLE OF THE NATIONAL LABORATORIES IN MATERIALS RESEARCH

WADSWORTH Jeffrey and FLUSS Michael(Chemistry and Materials Science Directorate , Lawrence Livermore National Laboratory , Livermore , CA 94551)

金属学报(英文版)

The role of the National Laboratories is summarized from the era of post World War II to the present time. The U.S. federal government policy for the National Laboratories and its influence on their materials science infrastructure is reviewed with respect to .determining overall research strategies, various initiatives to interact with industry (especially in recent years),building facilities that serve the nation, and developing leading edge research in the materials sciences. Despite reductions in support for research in the U.S. in recent years, and uncertainties regarding the specific policies for Research &Development (R&D) in the U.S., there are strong roles for materials research at the National Laboratories. These roles will be centered on the abilities of the National Laboratories to field multidisciplinary teams, the use of unique cutting edge facilities, a focus on areas of strength within each of the labs,increased teaming and partnerships, and the selection of motivated research areas. It is hoped that such teaming opportunities will include new alliances with China, in a manner similar, perhaps, to those recently achieved between the U.S. and other countries.

关键词: : U.S. Materials Science. U.S. National Laboratories and Facilities , null

Effect of  WC/W₂C on the microstructure and abrasion resistance of high-boron hardfacing alloys

Jianxun GONG

金属学报(英文版)

High boron hardfacing alloys reinforced with primary M₂B phases on Q235 steel plates were prepared by the method of flux-cored wire submerged arc welding. The microstructure and boride morphology were investigated using optical microscopy (OM), scanning electron microscopy (SEM) and X-ray diffraction (XRD). The effect of WC/W₂C on the microstructure was discussed. It indicated that the volume fraction of primary M₂B phases has increased due to good nucleated cores of incompletely molten W₂C particles provided by casting tungsten carbide or decarburizing reaction of WC powders. Abrasion resistance was evaluated by wet sand rubber wear tests and the wear mechanism was studied using SEM. It shows that primary M₂B grains play a key role in improving abrasion resistance.

关键词: primary M2B phases , null , null , null

Ho掺杂对Pt-Ru/C电催化氧化甲醇的性能影响

刘世斌 , 王秀光 , 李一兵 , 郝晓刚 , 张忠林 , 段东红 , 孙彦平

稀有金属材料与工程

采用脉冲电沉积法制备了碳载的Pt-Ru-Ho电催化剂,循环伏安法(CV)和交流阻抗法(EIS)测定催化剂的甲醇电氧化活性,用XRD、EDS和XPS表征电催化剂的物性结构、表面元素组成和价态形式.结果表明,电催化剂中Pt,Ru,H0 3种元素以合金的形式存在,在合金表面有HoO存在,合金微粒粒径为3.5 nm,比表面积为73.3 m2.g-1;掺杂适量稀土金属Ho对Pt-Ru合金的活性有明显影响,其中原子比为npt:nRu:nHo=1:1:0.2时,Pt-Ru-Ho/C中Ho的含量较为适宜,电催剂的Tafel常数α减小,反应活化能低于Pt-Ru/C,为28.4 kJ·mol-1,催化活性明显高于Pt-Ru/C,但Ho含量过高Pt-Ru-Ho/C的活性低于Pt-Ru/C:Pt-Ru-Ho0 .2/C甲醇的反应级数为0.17级.

关键词: 脉冲电沉积 , 电催化剂 , 电催化氧化 , 稀土元素

冷轧Q195F钢种退火工艺制度的优化

崔勇 , 李驭 , 佟强

物理测试 doi:10.3969/j.issn.1001-0777.2000.06.007

介绍了从德国引进的全氢罩式退火炉的特点，结合本钢冷轧厂的生产实际情况，分析了影响Q195F钢种退火工艺的多种因素，对主要产品Q195F钢种的退火工艺制度进行了优化。

关键词: 罩式炉 , 退火 , 工艺优化