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grain size and temperature effect on the tensile behavior and deformation mechanisms of non-equiatomic fe(41)Mn(25)Ni(24)Co8Cr2high entropy alloy

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Journal of Materials Science & technology 2020年第7期42卷 190-202页

作者： H.t.Jeong W.J.Kim Department of Materials Science and Engineering Hongik UniversityMapo-guSangsu-dong 72-1Seoul121-791Republic of Korea

the effect of the grain size on the tensile properties and deformation mechanisms of a nonequiatomic fe(41)Mn(25)Ni(24)Co8 Cr2 high-entropy alloy was studied in the temperature range between 298 and 1173 K by preparing the samples with three different grain sizes through severe plastic deformation and subsequent annealing:ultrafine(sub)grain size(≤0.5μm),8.1μm and 590.2μ*** the temperature between 298 and773 K,the material with the large grain size of 590.2μm exhibited the largest tensile ductility(57%-82%)due to its high strain hardening associated with mechanical twinning,but it exhibited the lowest strength due to its large grain *** material with the ultrafine(sub)grain size exhibited the lowest tensile ductility(3%-7%)due to a greatly reduced strain hardening ability after severe plastic deformation,but it exhibited the highest strength due to the dislocation strengthening and grain refinement *** tensile testing at temperatures above 973 K,recrystallization occurred in the material with the ultrafine(sub)grains during the sample heating and holding stage,leading to the formation of fine and equiaxed grains with the sizes of 6.8-13.5μ*** deformation behavior of the fe(41)Mn(25)Ni(24)Co8 Cr2 with different grain sizes in the high temperature range between 973 and 1173 K,where pseudosteady-state flow was attained in the stress-strain curves,could be explained by considering the simultaneous contribution of grain boundary sliding and dislocation-climb creep to total plastic *** activation energies for plastic flow for the materials with different grain sizes were similar as^199 kJ/*** predicting the deformation mechanism,it was important to consider the change in grain size by rapid grain growth or recrystallization during the sample heating and holding stage because grain boundary sliding is a grain-size-dependent deformation *** sample with the ultrafine(sub)grains exhibited the large tensile elongations of 30%-85%due to it

关键词： High entropy alloys grain size High temperature deformation mechanism tensile behavior grain boundary sliding

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Effect of roll speed ratio on the texture and microstructural evolution of an FCC high-entropy alloy during differential speed rolling

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Journal of Materials Science & technology 2022年第16期111卷 152-166页

作者： H.t.Jeong W.J.Kim Department of Materials Science and Engineering Hongik UniversityMapo-guSangsu-dong 72-1Seoul 121-791Republic of Korea

A very coarse-grained(335μm)fe_(41)Mn_(25)Ni_(24)Co_(8)Cr_(2)high-entropy alloy with a single FCC phase was cold rolling to a 80%reduction in thickness using the differential speed rolling technique with various speed ratios(SRs)ranging between 1 and *** the SR was increased,the volume fraction of the region of high-density micro-shear bands increased to accommodate the higher shear *** SR=4,the entire thickness of the sheet was covered with micro-shear bands,and ultrafine(sub)grains with a size of1.4μm were uniformly formed along the shear bands.A continuous dynamic recrystallization(CDRx)mechanism occurred during rolling,and a higher SR accelerated the CDRx *** conventional rolling(at SR=1),a brasstorientation texture with minor components of Stand Cutorientations *** higher SRs,shear texture developed as the main type,while the development of rolling texture was *** microstructure at SR=4 obtained after annealing at973 K showed a fully recrystallized microstructure composed of a five times smaller grain size(4μm)with a higher intensity ofγfiber texture compared with that prepared by conventional *** samples processed with high SRs exhibited better tensile properties compared with the conventionally rolled sample in terms of strength and ductility after *** current results demonstrate that by using differential speed rolling with a high SR,one can achieve a significantly finer and more homogeneous microstructure,stronger shear texture,and superior tensile mechanical properties for an FCC high-entropy alloy compared to that obtained by conventional *** strength of the as-rolled and annealed samples was quantitatively explained by considering the contribution of grain size and dislocation density to strengthening.

关键词： High entropy alloys Differential speed rolling texture grain refinement Strength Severe plastic deformation

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A study on the grinding temperature field for titanium alloy

A study on the Grinding temperature field for Titanium alloy

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亚洲精密工程、微纳技术国际会议

作者： W.Li, t.xINg, BxQiu, g.x.Hu, Y.F.Jin ZHEJIANg UNIVERSItY OF tECHNOLOgY,No.6 Zhaohui District, Hangzhou 310014,P.R.China

A reasonable finite element (fe) model of grinding temperature field has been developed on the basis of analysis of transient temperature field. And three kinds of boundary conditions are loaded on the element of a moving heat source. the study, which is based on the finite element principle, has been carried out using the numerical simulation software ANSYS. Many results have been obtained including three dimensional temperature distribution map. the simulated results under different conditions show good agreement with experimental results. the temperature of the dry-grinding has been compared with that of the wet-grinding. It shows that the wet-grinding highly decrease the temperature of the workpiece. Finally, the variable coefficient of convective heat transfer and the different trapeziform heat source have been discussed in this paper.

关键词： grinding temperature Field, Finite element, Computer Simulation, titanium alloy

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Effects of Heat treatment on Hardness and Dry Wear Properties of a Semi-Solid Processed fe-27 wt pct Cr-2.9 wt pct C Cast Iron

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Journal of Materials Science & technology 2008年第3期24卷 330-334页

作者： A.Wiengmoon t.Chairuangsri N.Chomsang N.Poolthong J.t.H.Pearce Department of Physics Faculty of ScienceNaresuan University Department of Industrial Chemistry and Electron Microscopy Research and Service Center Faculty of ScienceChiang Mai University Department of Physics Faculty of ScienceChiang Mai University Division of Materials technology School of EnergyEnvironmental and MaterialsKing Mongkut's University of Technology Thonburi National Metal and Materials technology Center

Effects of heat treatments on hardness and dry wear properties of a semi-solid processed fe-26.96 wt pct Cr- 2.91 wt pct C cast iron were studied. Heat treatments included tempering at 500℃, destabilisation at 1075℃ and destabilisation at 1075℃ plus tempering at 500℃, all followed by air cooling. Electron microscopy revealed that, in the as-cast condition, the primary proeutectic austenite was round in shape while the eutectic M7C3 carbide was found as radiating clusters mixed with directional clusters. tempering did not change the microstructure significantly when observed by scanning or transmission electron microscopy. Destabilisation followed by air cooling led to a precipitation of secondary M23C6 carbide and a transformation of the primary austenite to martensite. Precipitation behaviour is comparable to that observed in the conventionally cast iron. tempering after destabilisation resulted in a higher amount of secondary carbide precipitation within the tempered martensite in the eutectic structure. Vickers macrohardness and microhardness in the proeutectic zones were measured. Dry wear properties were tested by using a pin-on-disc method. the maximum hardness and the lowest dry wear rate were obtained from the destabilisation-plus-tempering heat treatment due to the precipitation of secondary carbides within the martensite matrix and a possible reduction in the retained austenite.

关键词： Semi-solid process High chromium cast iron Heat treatment Hardness Wear

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神奇的牙仙

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初中生 2021年第24期 6-7页

作者： Elias Hao fe Yun 不详

帮助孩子从小就爱护牙齿很重要。美国的民间传说里有一位"牙仙"。当孩子的乳牙脱落时,牙仙会把它们收集起来。牙仙工作很努力,每天晚上都要收集好几百颗牙齿。她把牙齿带回仙人居住的神奇国度里,用它们来建造美丽的城堡和宫殿。牙仙不... 详细信息

帮助孩子从小就爱护牙齿很重要。美国的民间传说里有一位"牙仙"。当孩子的乳牙脱落时,牙仙会把它们收集起来。牙仙工作很努力,每天晚上都要收集好几百颗牙齿。她把牙齿带回仙人居住的神奇国度里,用它们来建造美丽的城堡和宫殿。牙仙不喜欢坏牙,只要那些白白净净的乳牙。孩子在睡前把脱落的乳牙放在枕头下面,希望早上醒来时能看到牙仙留下的硬币或一份小礼物。对孩子来说,这是一个简单的"交易"。父母经常通过牙仙的故事来鼓励孩子爱护牙齿。

关键词：乳牙民间传说鼓励牙齿神奇爱护

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Studies of multilayer structure in depth direction by soft x-ray spectroscopy

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Nuclear Science and techniques 2006年第5期17卷 257-267页

作者： M. WAtANABE t. EJIMA N. MIYAtA t. IMAZONO M. YANAgIHARA Shanghai Dianji University Institute of Composite Materials Shanghai Jiaotong University Shanghai 200030 China Saga University Synchrotron Light Application Center Japan Institute of Multidisciplinary Research for Advanced Materials Tohoku University Japan Institute of Multidisciplinary Research for Advanced Materials Tohoku University

It is demonstrated that two kinds of soft x-ray spectroscopy are useful as nondestructive methods to in- vestigate multilayer structures modified by interdiffusion or by chemical reaction of adjoining layers in depth direc- tion. One is the total electron yield (tEY) spectroscopy involving angular dependence measurement. Using this method, it was found that in LiF/Si/LiF trilayers, the Si layers exhibited a characteristic similar to porous Si, and in CaF2/Si/CaF2 trilayers, it was found that CaF2 segregated through the Si layer. Moreover, it has been shown that the thickness of the top layer of a Mo/Si x-ray multilayer can be determined by analyzing tEY signals generated by the standing wave. the other is the soft x-ray emission spectroscopy involving spectral shape analysis. Using this method, it was found that in Mo/Si x-ray multilayers, the interdiffusion or chemical reaction giving rise to deterioration of re- flectance character occurs in as-deposited samples as well as in heated samples. In antiferromagnetic fe/Si multilay- ers, it was confirmed that there was no existence of pure Si layers, but insulating feSi2 layers were present. this result suggests that the source of antiferromagnetic coupling is not conduction electrons but quantum wave interference.

关键词：软x射线能谱多层结构景深方向总电子流量驻波硅化合物

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High-frequency induction heated sintering of ball milled fe-WC nanocomposites

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International Journal of Minerals,Metallurgy and Materials 2013年第7期20卷 693-699页

作者： M. Zakeri t. Zanganeh A. Najafi Ceramic Department Materials and Energy Research Center P.O. Box 31787/316 Karaj Iran Department of Materials Saveh Branch Islamic Azad University Saveh Iran

fe-WC nanocomposites were successfully fabricated by high-frequency induction heated sintering of ball milled nanostructure powders. the ball milled powders were characterized by x-ray diffraction. Density measurements by the Archimedes method show that all sintered samples have the relative density higher than 95%. Studies on the effects of WC content, milling speed, and milling time indicate that a higher milling speed and a more WC content lead to the improvement of mechanical properties. there is a very good distribution of WC particles in the fe matrix at the milling speed of 650 r/rain. For the sintered sample 20-5-650 （20wt% WC, milling time of 5 h, and milled speed of 650 r/min）, the maximum Brinell hardness and yield stress are obtained to be 3.25 gPa and 858 MPa, respectively. All sintered samples have brittle fracture during compression test except the sample 20-5-650.

关键词： nanocomposites metallic matrix composites iron tungsten carbide induction heating sintering mechanicalproperties

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糖分少一点,牙齿好一点

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初中生 2021年第24期 10-11页

作者： Elias Hao fe Yun 不详

在中世纪(从公元5世纪后期到公元15世纪中期)以及之前的好几百年,口腔卫生根本就不是英国人关注的重点。人们疲于奔命,根本没有时间和精力去操心如何保持牙齿的清洁和健康,更别提矫正牙齿了。如今,英国的情况发生了很大的变化。人们对... 详细信息

在中世纪(从公元5世纪后期到公元15世纪中期)以及之前的好几百年,口腔卫生根本就不是英国人关注的重点。人们疲于奔命,根本没有时间和精力去操心如何保持牙齿的清洁和健康,更别提矫正牙齿了。如今,英国的情况发生了很大的变化。人们对自己的牙齿是否健康和美观越来越感兴趣。大多数人都期待拥有一个"更好的微笑"。因此,个人用于改善牙齿状况的支出大幅增加。

关键词：口腔卫生牙齿 15世纪微笑健康英国人中世纪

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迪士尼让人们成为更好的自己

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初中生 2020年第15期 12-13页

作者： fe Yun Elias Hao 不详

华特·迪士尼没有建造一个只是为了满足儿童幻想而存在的主题公园。他创造了一个我们相信的世界,以及一段能成为更好的自己的旅程。有人说,华特建造了一座房子,让现代情感有了被展示之处。华特布置了这座房子,挂上了合适的窗帘,还给冰... 详细信息

华特·迪士尼没有建造一个只是为了满足儿童幻想而存在的主题公园。他创造了一个我们相信的世界,以及一段能成为更好的自己的旅程。有人说,华特建造了一座房子,让现代情感有了被展示之处。华特布置了这座房子,挂上了合适的窗帘,还给冰箱装满了食物。久而久之,他的力量照亮了大厅,点燃了孩子们的思想之光。他伸出手,带领人们去相信,这地球就是我们想要的世界:去爱各种颜色.

关键词：迪士尼主题公园华特房子建造

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迪士尼游轮:人人都可以尽情欢乐

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初中生 2020年第15期 8-9页

作者： fe Yun Elias Hao 不详

游轮已经成为很多家庭度假的首选,原因很美好。坐游轮的话,一家人在一个假期内可以游览好几个不同的地方。而且,食物是免费的。出门旅行,不需要担心做饭或者每顿饭都要掏钱买,谁不喜欢呢?迪士尼游轮是无数家庭共度美好时光的最佳场所。... 详细信息

游轮已经成为很多家庭度假的首选,原因很美好。坐游轮的话,一家人在一个假期内可以游览好几个不同的地方。而且,食物是免费的。出门旅行,不需要担心做饭或者每顿饭都要掏钱买,谁不喜欢呢?迪士尼游轮是无数家庭共度美好时光的最佳场所。它几乎包括了每个人希望拥有的一切——甚至更多。比如说,大部分游轮都收取高额费用才提供客房服务,但在迪士尼游轮上,客房服务对所有家庭都是免费的。

关键词：客房服务迪士尼游轮家庭最佳场所免费美好时光出门旅行

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