材料期刊网

EFFECT OF MICROSTRUCTURE ON FATIGUE CRACK INITIATION OF SHOT PEENED COPPER AND BRASS

K.W.Xu , N.S.Hu and J.W.He(State-Key Laboratory for Mechanical Behavior of Materials , Xi'an Jiaotong University , Xi'an 710049 , China Manuscript received 26 August 1996)

金属学报(英文版)

The effect of microstructure on fatigue crack initiation was considered in the shot peened surface layer by eliminating the influence of compressive residual stress. Results indicate that the drastically deformed structure by shot peening would keep the dislocations from moving out of the surface and hold the dislocations inside the cell structure of copper or the palling structure of brass. The fatigue damage of intrusion and extrusion type could thus be depressed and the fatigue life is enhanced.

关键词: :shot peening , null , null

S355J2W+N钢激光-MAG复合焊与MAG焊对比

谷晓鹏 , 段珍珍 , 邓钢 , 谷晓燕

材料工程 doi:10.11868/j.issn.1001-4381.2015.02.004

利用激光-MAG复合焊和MAG焊进行了厚板S355J2W+N低碳钢的焊接实验,分析了两种焊接方法接头的微观组织和力学性能.结果表明:复合焊和MAG焊焊缝接头均由焊缝区、过热区、重结晶区和不完全重结晶区构成,复合焊接头截面呈“高脚杯”状特点,焊缝填充量和热影响区宽度较MAG焊明显减小.复合焊由于冷却速率快,过热区魏氏组织略有增多,硬度高于MAG焊,抗拉强度和弯曲性能与MAG焊相比,无显著差异,均能够满足生产标准的要求.

关键词: S355J2W+N , 激光 , MAG , 复合焊 , 接头组织 , 性能

THE MECHANICAL BEHAVIOR OF LABORATORY CROSS-WELD SPECIMEN AND ITS RELATION WITH THE PRACTICAL CASES AT ELEVATED TEMPERATURE

Author S.T. TU , J.M. Gong and X. Ling Nanjing University of Chemical Technology , Nanjing 210009 , ChinaManuscript received 18 October 1998

金属学报(英文版)

In order to interpret the test results of crossweld specimens for application in practical welded components, the present paper studies the high temperature behavior of laboratory cross weld specimens in terms of the uniaxial material tests and numerical simulations. It is found that the crossweld specimen may be used for the high temperature strength assessment, but can hardly be used for life assessment of the practical welded components, which depends on the loading conditions of the components.

关键词: high temperature , null , null , null , null

Preparation and Arc Breakdown Behavior of Nanocrystalline W-Cu Electrical Contact Materials

Wenge CHEN

材料科学技术（英文）

Nanostructured (NS) W-Cu composite powder was prepared by mechanical alloying (MA), and nanostructured bulk of W-Cu contact material was fabricated by hot pressed sintering in an electrical vacuum furnace. The microstructure, electric conductivity, hardness, breakdown voltage and arcing time of NS W-Cu alloys were measured and compared to conventional W-Cu alloys prepared by powder metallurgy. The results show that microstructural refinement and uniformity can improve the breakdown behavior, the electric arc stability and the arc extinction ability of nanostructured W-Cu contacts materials. Also, the nanostructured W-Cu contact material shows the characteristic of spreading electric arcs, which is of benefit to electric arc erosion.

关键词: Nanostructured materials , null , null , null

S355J2W耐候钢的耐腐蚀性能

鲁二敬 , 卢峰华 , 许鸿吉 , 谢明 , 钮旭晶

机械工程材料

通过周期浸润腐蚀试验，对比研究了S355．12W耐候钢和Q345R低合金钢在NariSOs溶液中的耐腐蚀性能，并用扫描电镜对腐蚀产物进行了观察和分析。结果表明：在相同试验条件下，S355J2W耐候钢的腐蚀速率低于Q345R钢的；S355J2W耐候钢会在表面形成黑褐色锈层，而Q345R钢表面形成橘红色易剥落的疏松锈层；S355J2W耐候钢腐蚀产物微观形貌为沿放射性方向生长的针状晶体，Q345R钢为颗粒状聚合物堆积而成，形状无规则，颗粒之间有较大的空隙。

关键词: S355J2W耐候钢 , 周期浸润腐蚀试验 , 耐腐蚀性能

亚稳态He(23S)原子与N2H4分子传能产物的发光研究

胡义华 , 刘美希 , 陈丽 , 王小涓 , 储焰南 , 曹德兆

量子电子学报 doi:10.3969/j.issn.1007-5461.2001.04.008

本文在流动余辉装置上,研究了亚稳态He(23S)原子与N2H4分子碰撞传能,观察到了激发态产物NH(A3II→X3∑+)、NH(c1II→a1△)、NH2(A2A1→X2B1)的发射光谱,由相对光谱强度求得了形成各产物的通道比;分析NH(A3II,v＇=0)的转动分辨谱的结果表明,v＇=0能级上的转动布居是"双模”分布,激发态产物NH(A)、NH2(A)的形成机理可能是: He(23S)+N2H4→N2H4*→NH(A)+NH2(A)+H.

关键词: 碰撞传能 , 化学发光 , NH(A3Ⅱ)的发射光谱

Novel hard materials with controlled (W_0.5Al_0.5)C grain shapes: in-situ high pressure preparation and mechanical properties

Zhuhui QIAO

金属学报(英文版)

A novel hard material with various (W_0.5Al_0.5)C grain shapes was successfully prepared through mechanical alloying and in-situ high-pressure sintering process. X-ray diffraction apparatus and scanning electron microscopy were used to characterize the phase and the microstructures of the samples. The novel hard materials with ``fibrous", ``rounded" and ``plate-like" grains, which do not contain sharp edges, have the improved mechanical properties. The bulk boundless (W_0.5Al_0.5)C hard material with various (W_0.5Al_0.5)C grain shapes possesses good mechanical properties and light weight. The formation mechanism for the non-equilibrium (W_0.5Al_0.5)C grains during in-situ high-pressure sintering is also discussed.

关键词: Novel hard material

SYNTHESIS AND SOLID STATE SINTERING OF W-Ni-Fe NANO-COMPOSITE POWDERS

X.H.Qu , J.L. Fan , Y.M. Li and B. Y Huang(The State Key Laboratory for Powder Metallurgy , Central South University of Technology , Changsha410083 , China)

金属学报(英文版)

The mixture of 90%W 7wt%Ni and 3wt%Fe elemental powders was milled in a planetary high-enerpy ball mill. The evolution of the structure during milling and the sintering behavior Of the milled powders were tested. The results showed that by mechanical alloying W(Ni, Fe) supersatumted solid solution with nano-meter size formed, which can enhance the sintering process. Ftilly dense alloy from the milled powders was obtained through solid state sintering. The tensile strength of the obtained alloy is over 900MPa which is comparuble to that of the alloy sintered by traditional liquid-phase sintering from un-milled powders of the same composition.

关键词: mechanical alloying , null , null , null

Evaluation of mechanical properties of structural materials by a spherical indentation based on the representative strain-an improved algorithm at great depth ratio

金属学报(英文版)

At great depth ratio, two methodologies based on the representative strain were improved to extract mechanical properties of metallic engineering structural materials from P-h curve of an indentation response. The improved aspects include: the combination of great ratio h(1)/R=0.1 and h(2)/R=0.4 replaced h(1)/R=0.01 and h(2)/R=0.06 (Cao's method) and h(1)/R=0.1 and h(2)/R=0.3 (Ogasawara's method); three types of metallic engineering structural materials with obviously different elastic modulus were dealt with to get their calculation parameters, respectively; a new parameter reflecting the effect of work-hardening exponent n was introduced to get the dimensionless function which is independent of n and a relationship between W/(h(3)sigma(r)S) and E*/(sigma(r)S) at great depth ratio. By using the results of finite element simulation, the efficiency and accuracy of the improved method have been proved, and it showed that the accuracy of the improved method is much better than the former method.

关键词: Spherical indentation;Representative strain;Metallic engineering;structural material;Mechanical property;Great depth ratio;measuring elastoplastic properties;energy-based method;plastic;properties;conical indentation;metal materials;hardness definitions;bulk materials;extract;tests

Bi2Sr2CaCu2O8单晶S-N转变的E-J特性

臧超飞 , 何豫生 , 沈庆飞 , 昌俊 , 李春光 , 张国华 , 罗胜 , 齐志 , 尹道乐 , 丁克俭

低温物理学报 doi:10.3969/j.issn.1000-3258.2001.04.008

我们应用脉冲电流的方法测量了Bi2Sr2CaCu2O8单晶在4特斯拉强场下的大电流时等温E-J特性.我们观察到在大电流时,样品电阻率ρ迅速增大,随着电流的继续上升,经过一段正曲率增长阶段,几乎达到饱和值,最后经过一段负曲率上升,达到正常态,显示出完整的S形.应用尹道乐等人的统一物质方程理论,给出了实验曲线较好的数值拟合.根据拟合结果,讨论了理论中各个参量的物理意义.

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