材料期刊网

EFFECTS OF MICROSTRVCTURE ON FATIGUE CRACK GROWTH BEHMIOR IN Ni-BASE SUPERALLOY GH586

S.S. Xie , X.F. Pan , T.L. Wang , Z.X. Wang , H.C. Yang and Q. Wang ( School of Materials and Metallurgy , Northeastern Universityl Shenyang 110006 , China)( School of Materials and Metallurgy , Northeastern Universityl Shenyang 110006 , China)( School of Materials and Metallurgy , Northeastern Universityl Shenyang 110006 , China)( School of Materials and Metallurgy , Northeastern Universityl Shenyang 110006 , China)( Institute of Metal Research , The Chinese Academy of Science , Shenyang 110015 , China)( Liaoning Machinery Industry Foreign Trade Co. Ltd. , Shenyang 110002 , China)

金属学报(英文版)

Threshold stress values, muging from ～8 to 16MPa·m1/2 can be obtained in a Ni-base alloy GH586 by varying the microstructure through heat treatments. The threshold and low crack growth rate behaviors at room temperature, with varying groin size and γ'-distribution, have been investigated. The results indicate that grain size is an important microstructurol parameter that affects fatigue crack growth threshold and propagation behaviors, as the values of △Kth increase with increasing grain size, but the γ' -distribution also has important effect. Analyses show that the effects of groin size on threshold and low crack-growth rate behavior result from heterogeneous deformation and roughness-induced crack closure due to crystallographic slipping and cracking in coarse microstructure. The higher △Kth and lower fatigue crack growth rate with increasing amounts of fine γ' phases are closely related to less damage accumulation level in deformation zone of crack-tip resulted from heterogeneous deformation due to dislocations' shearing γ' precipitates.

关键词: superalloy GH586; fatigue crack growth; threshold; grain size;γ'-distribution

Workability Studies in Forming of Sintered Fe-035C Powder Metallurgy Preform During Cold Upsetting

S Narayan , A Rajeshkannan

钢铁研究学报(英文版)

An experimental investigation on the workability behaviour of sintered Fe-035C steel preforms under cold upsetting, have been studied in order to understand the influence of aspect ratio and lubrication condition on the workability process. The above mentioned powder metallurgy sintered preform with constant initial theoretical density of 84% of different aspect ratios, namely, 04 and 06 respectively were prepared using a suitable die-set assembly on a 1 MN capacity hydraulic press and sintered for 90 min at 1200 ℃. Each sintered preform was cold upset under nil/no and graphite frictional constraint, respectively. Under the condition of triaxial stress densification state, axial stress, hoop stress, hydrostatic stress, effective stress and formability stress index against axial strain relationship was established and presented in this work. Further more, attained density was considered to establish formability stress index and various stress ratio parameters behaviour.

关键词: powder metallurgy , failure analysis , plastic behaviour , workability

Q相-C2S-C4AF-C12A7系列水泥形成的研究

姜奉华 , 徐德龙

硅酸盐通报 doi:10.3969/j.issn.1001-1625.2004.06.006

通过研究Q相与C2S和Q相与C4AF的共存条件,构造Q相-C2S-C4AF水泥系统,对此系统水泥形成条件进行研究.研究表明:Q相与C2S和Q相与C4AF能够共存,可以组成Q相-C2S-C4AF-C12A7水泥系统.在Q相-C2S-C4AF-C12A7水泥系统中,Q相在1270℃开始生成,随着温度的升高,Q相的生成量逐渐增大;采用V2O5对β-C2S具有较好的稳定作用.随着C4AF量的增加,Q相的量也在增加,同时,烧成温度降低.

关键词: Q相 , Q相-C2S-C4AF水泥 , 形成条件 , 抗压强度

Mechanical alloying of Fe-Nb-C materials

Materials Letters

Mechanical alloying (MA) of elemental powder mixtures of Fe50Nb35C15, Fe60Nb30C10 and Fe50Nb40C10 was performed using a high energy ball mill. In the MA processing, ball milling first leads to a Fe-Nb-C amorphous phase and nanocrystalline NbC. Further milling results in the formation of a nanocrystalline solid solution of Fe(Nb, C) and nanocrystalline NbC in Fe50Nb35C15 and Fe60Nb30C10, while the final product for Fe50Nb40C10 is a mixture of amorphous Fe-Nb-C and nanocrystalline NbC.

关键词: mechanical alloying;Fe;Fe, Nb and C powders;amorphous;nanocrystalline;solid solution

Q460C热处理挽救工艺

刘军刚

物理测试

Q460C钢板由于冶炼和轧制工艺不稳定,经常出现伸长率不合格的问题.论述了不同的热处理工艺对Q460C性能的影响.研究表明:Q460C经过正火后,强度明显降低.经过正火控冷后,强度、韧性均满足生产要求,提高了产品合格率.

关键词: Q460C , 热处理 , 力学性能

Q460C连铸板坯的高温塑性

段双霞 , 孙建林 , 李志恩 , 富平原 , 雷爱民

钢铁研究学报

在Gleeble-1500热模拟机上测定了Q460C连铸坯的热塑性,深入分析了钢Q460C的高温脆化机理,确定了连铸坯的最佳矫直温度.结果表明,钢Q460C高温脆化受变形速率的影响较大,在第Ⅲ脆性区变形速率越低脆化越严重,实验用钢Q460C的低塑性区确定在660～985℃,连铸坯顶弯、矫直温度应高于985℃,有利于提高塑性,避免连铸坯表面裂纹的产生.

关键词: Q460C连铸板坯 , 热模拟 , 高温塑性

Q460C连铸板坯的高温塑性

段双霞 , 孙建林 , 李志恩 , 富平原 , 雷爱民

钢铁研究学报

在Gleeble1500热模拟机上测定了Q460C连铸坯的热塑性，深入分析了钢Q460C的高温脆化机理，确定了连铸坯的最佳矫直温度。结果表明，钢Q460C高温脆化受变形速率的影响较大，在第Ⅲ脆性区变形速率越低脆化越严重，实验用钢Q460C的低塑性区确定在660~985 ℃，连铸坯顶弯、矫直温度应高于985 ℃，有利于提高塑性，避免连铸坯表面裂纹的产生。

关键词: Q460C连铸板坯;热模拟;高温塑性

Effect of different types of carbon on microstructure and arcing behavior of Ag/C contact materials

Ieee Transactions on Components and Packaging Technologies

Silver-carbon (Ag/C) contact materials with different types of carbon, including diamond, graphite, carbon black, and carbon nanotubes were,fabricated by high-energy ball milling and hot-pressing. Their microstructures, arcing properties, and stability of the carbon structures were investigated. The results show that Ag/C nanotubes material displays a scallop-like morphology, which is significantly different from the microstructure of other Ag/C materials with dispersed particles. During the process of discharge, the diamond and carbon black in Ag/C materials are partially graphitized, while the morphology and crystal structure of graphite component have little change, indicating the graphite structure of Ag/C materials is the most stable of all.

关键词: electrical contacts;Raman spectra;silver-carbon (Ag/C) black;silver-carbon (Ag/C) nanotubes;silver-diamond (Ag/diamond);silver-graphite (Ag/graphite);nanotubes;raman

Improved hydrogen storage performance of Li-Mg-N-H materials by optimizing composition and adding single-walled carbon nanotubes

International Journal of Hydrogen Energy

A systematic investigation on the hydrogen storage properties of Li-Mg-N-H materials with various compositions was performed. Li-Mg-N-H hydrogen storage materials were prepared by mechanically milling LiNH2/MgH2 mixtures with initial molar ratios ranging from 1.5:1 to 3: 1, followed by de/rehydriding at 200 degrees C. It was found that the hydrogen storage capacity of the system was highly dependent on the initial phase ratio of the LiNH2/MgH2 mixture. An optimum hydrogen capacity of about 5 wt% was achieved in the 2.15:1 LiNH2/MgH2 mixture. Different carbon materials, such as the single-walled carbon nanotubes (SWNTs), multi-walled carbon nanotubes, graphite and activated carbon, were used as additive to improve the hydrogen storage performance. It was found that the dehydriding kinetics of the Li-Mg-N-H material could be markedly improved by adding a small amount of SWNTs, especially in the as-prepared state. (c) 2006 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.

关键词: hydrogen storage;dehydriding kinetics;carbon nanotubes;arc-discharge method;system;microstructure;desorption;absorption;behaviors;property;imides

Q345C钢板表面裂纹金相分析

潘红涛

物理测试 doi:10.3969/j.issn.1001-0777.2007.01.012

文章对Q345C钢板表面产生的裂纹进行了宏观和光学显微镜分析.结果显示:裂纹产生的原因是加热之后在轧制过程中形成的折叠,1号裂纹上出现的大型杂质有可能是压入的氧化铁皮.

关键词: 表裂 , 形状 , 组织