Author J.H. Lee 1)
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K.B. Yoon2)
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Y.J. Kim3)and U.B. Baek4) 1) Engineering Research Department
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Korea Institute of Nuclear Safety
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P.O. Box 114
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Yoosung
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Taejon 305600
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Korea2) Department of Mechanical Engineering
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Chung Ang University
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221 Huksuk
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Dongjak
,
Seoul 156756
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Korea3) Department of Mechanical Engineering
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Sungkyunkwan University
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300 Chunchun
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Jangan
,
Suwon 440746
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Korea4) Failure Prevention Research Center
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Korea Research Institute of Standards and Science
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P.O. Box 102
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Yoosung
,
Taejon 305600
,
KoreaManuscript received 18 October 1998
金属学报(英文版)
Most of the assessment equations for Ct which is a wellknown fracture parameter characterizing high temperature crack growth rates, have limited applicability to constant load conditions after sudden loading. However, crack growth due to creep can also occur under load varying conditions when load rising time is so long that accumulated creep deformation near the crack tip is not negligible.In this paper, the estimation equation of the Ctparameter which can be applied to the case of slow load rising, i.e., (Ct)r, is explained. And the correlation between (Ct)r at the end of the load increasing period and Ct at the beginning of the succeeding load hold period is discussed. Finite element analyses of several cases with various loading conditions were performed and results were presented to show the effectiveness of the proposed Ct estimation scheme. The general applicability of the equation is also discussed.
关键词:
creep
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null
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null
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null
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null
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null
陈篪
金属学报
<正> 目前,J_(Ⅰc)的测试引起了国内外的厂泛重视。三点弯曲试样得到了最广泛的应用。我们曾导出 J=(2U/B(W-a) (1)的关系,式中U是试样的应变能。Rice等在[2]中所建议的是另一关系 J=2/(B(W-a)integral from n=0 to △aPd△_a (2)其中 △_a=△-△_0 (3)△_0是同尺寸的无裂纹试样加载到同一载荷P时的位移。(1)和(2)式虽形式相近但内容不同究竟何者更为正确,很有必要加以澄清。 我们的推导是以U=B(W-a)~2f(△)或其等效关系P=B(W-a)~2φ(△)为出发点的,这里不再重复。Rice则假定
关键词:
Journal of Alloys and Compounds
(Ca(1-x-y),Ln(y))MoO(4): xEu(3+) (Ln = Y, Gd) red phosphors were prepared by co-precipitation method with NH(4)HCO(3)-NH(3)center dot H(2)O system as the precipitating agent. X-ray diffraction (XRD), Fourier transform infrared spectrometer (FT-IR), and energy-dispersive X-ray spectrometer (EDS) were used to characterize the structure and composition of the phosphors. The synthesized (Ca(1-x-y),Ln(y))MoO(4): xEu(3+) have scheelite structure with pure phase. FT-IR spectra show strong absorption peaks between 914 and 730 cm(-1) which are assigned to the vibration of O-Mo-O in MoO(4)(2-) tetrahedron. The EDS analysis reveals that the red phosphors have been successfully prepared by co-precipitation method according to theoretic ratio. Photoluminescence spectra show a red emission around 614 with 394 and 464 nm excitation, which is match well with the output wavelength of commercial ultraviolet and blue LED chips. The luminescent intensity of (Ca,Ln)MoO(4): Eu(3+) is obviously higher than that of CaMoO(4): xEu(3+). Crown Copyright (C) 2010 Published by Elsevier B.V. All rights reserved.
关键词:
Co-precipitation;Red phosphor;Photoluminescence;(Ca(1-x-y),Ln(y))MoO(4): xEu(3+) (Ln = Y Gd);hydrothermal synthesis;camoo4;eu3+;luminescence
史菲
,
王春青
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郭学锋
稀有金属材料与工程
采用普通凝固技术制备了含有长周期堆垛有序(long period stacking ordered,LPSO)结构相的Mg92Zn4Y4和Mg92Zn4Y3Gd1合金.通过OM、SEM、EDS、XRD和TEM分析了合金中各相形貌、微区成分及结构.结果表明:Zn/RE原子比为l的2种铸态镁合金中均存在14H-LPSO结构相;在Mg-Zn-Y合金中添加稀土元素Gd增加了合金的形核质点并促进了长周期堆垛有序结构相的形成,14H-LPSO相体积分数由l2.1％增至30.4％;LPSO结构相在高温形成时分割了α-Mg树枝晶,基体平均晶粒尺寸由50 μm降至10 μm以下;铸态Mg92Zn4Y4合金的凝固组织为α-Mg固溶体+Mg12ZnY+Mg3Zn3Y2+Mg-Y;铸态Mg92Zn4Y3Gd1合金的凝固组织主要为α-Mg固溶体+Mg12Zn(Y,Gd)+Mg3Zn3(Y,Gd)2;室温条件下,Mg92Zn4Y4和Mg92Zn4Y3Gd1合金的压缩率达到12.4％和15.5％,热导率分别为99.233和88.639W·(m·K)-1.
关键词:
铸态Mg-Zn-Y(-Gd)合金
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长周期堆垛有序结构
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稀土
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热导率
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压缩塑性
Journal of Physics and Chemistry of Solids
The layered ternary ceramics Ti3SiC2 and Ti3AlC2 are isostructural and can form Ti3Si1-xAlxC2 solid solutions combining the advanced properties of both compounds [H.B. Zhang, Y.C. Zhou, Y.W. Bao, M.S. Li, Improving the oxidation resistance of Ti3SiC2 by forming a Ti3Si0.90Al0.1C2 solid solution, Acta Mater. 52 (2004) 3631-3637; E.D. Wu, J.Y. Wang, H.B. Zhang, Y.C. Zhou, K. Sun, Y.J. Xue, Neutron diffraction studies of Ti3Si0.9Al0.1C2 compound, Mater. Lett. 59 (2005) 2715-2719; J.Y. Wang, Y.C. Zhou, First-principles study of equilibrium properties and electronic structure of Ti3Si0.75Al0.25C2 solid solution, J. Phys.: Condens. Matter 15 (2003) 5959-5968; Y.C. Zhou, J.X. Chen, J.Y. Wang, Strengthening of Ti3AlC2 by incorporation of Si to form Ti3Al1-xSixC2 solid solutions, Acta. Mater. 54 (2006) 1317-1322]. In the present work, the solid solutions of Ti3Si1-xAlxC2 (x = 0, 0.25, 0.33, 0.5, 0.67, 0.75, 1) are investigated by first-principle calculations based on pseudo-potential plan-wave method within the density functional theory framework. The results show that as Al content increases in the solid solution, all the bonds have weakened to certain extents, which lead to an unstable structure both energetically and geometrically. The calculated results are compared and discussed with the reported data for the Ti3Si1-xAlxC2 solid solutions. (c) 2007 Elsevier Ltd. All rights reserved.
关键词:
ceramics;ab initio calculations;electronic structure;electrical;conductivity;oxidation behavior;mechanical-properties;ti3sic2;temperature;ti3alc2;air;si
Andrej Atrens
材料科学技术（英文）
Corrosion research by Atrens and co-workers has made significant contributions to the understanding of the service performance of engineering materials. This includes: (1) elucidated corrosion mechanisms of Mg alloys, stainless steels and Cu alloys, (2) developed an improved understanding of passivity in stainless steels and binary alloys such as Fe-Cr, Ni-Cr, Co-Cr, Fe-Ti, and Fe-Si, (3) developed an improved understanding of the melt spinning of Cu alloys, and (4) elucidated mechanisms of environment assisted fracture (EAF) of steels and Zr alloys. This paper summarises contributions in the following: (1) intergranular stress corrosion cracking of pipeline steels, (2) atmospheric corrosion and patination of Cu, (3) corrosion of Mg alloys, and (4) transgranular stress corrosion cracking of rock bolts.
关键词:
Stress corrosion cracking
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null
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null
张军
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孙学峰
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赵霞
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李晓光
低温物理学报
doi:10.3969/j.issn.1000-3258.1999.04.010
本文研究了Hg0.7Cr0.3Sr2Ca2Cu3Oy, HgBa2Ca2Cu2.9Re0.1Oy, HgSr2Ca3Cu3.8}Re0.2Oy的磁性,发现Re的掺入会改变U-J关系.由驰豫测量结果分析得到Hg(Re)-1223,Hg(Re)-1234具有对数钉扎势U=U0H-nln(Jc0/J),其中对Hg(Re)-1223在20K～60K范围里U0和Jc0近似与温度无关; 对Hg(Re)-1234,U0和Jc0与磁场和温度有关.而Hg-1223具有幂次方钉扎势U=U0(Jc0/J)μ.另外,由磁化曲线M(H)的测量得到临界电流密度随磁场的变化关系.结果表明Hg(Re)-1223在20K～90K、Hg(Re)-1234在20K～70K的温度范围内,临界电流密度随磁场的变化关系均可以用由对数钉扎势得出的Jc(H)关系很好地描述.我们认为Re掺入引起的体系的各向异性的减小和岛状钉扎中心,使得材料钉扎能力增强并引起U-J关系的变化.
关键词:
谭友宏
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刘敏
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马文有
材料保护
目前,有关稀土氧化物粉末粒度大小及含量对激光陶瓷合金化层裂纹及耐磨性能影响的研究较少.以近纳米级Y2O3-WC-B4C粉末对60CrMnMo钢表面进行激光陶瓷合金化,以提高其耐磨性能.采用金相显微镜、扫描电镜、X射线衍射仪、显微硬度计、轮式磨耗试验机分析、考察了Y2O3含量对合金化层的组织、物相、硬度及耐磨性能的影响.结果表明:Y2O3使合金化层表面更加平整、光滑,表面裂纹减少、变细;合金化层硬度随着Y2O3含量增加而降低;合金化层物相主要有Fe-Cr,Cr23 C6,B2W,B13C2等;随Y2O3含量增加,树枝晶减少,合金化层组织更均匀致密,磨损量先减小后增大;Y2O3含量为4％时,合金化层组织最细、耐磨性最好.
关键词:
激光合金化
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Y2O3-WC-B4C粉末
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60CrMnMo钢
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裂纹
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耐磨性能
