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Transactions of Nonferrous Metals Society of China 2014年第7期24卷 2301-2306页

作者：查敏李彦军 Ragnvald MATHIESEN Ruben Bj.RGE hans j. roven Department of Materials Science and Engineering Norwegian University of Science and Technology Department of Physics Norwegian University of Science and Technology Center for Advanced Materials Qatar University

A binary Al-7Mg alloy was processed by equal channel angular pressing （ECAP） at room temperature via route Bc, combined with intermediate annealing. After 6 passes, a high hardness of HV218 is achieved. Transmission electron microscopy （TEM） observations demonstrate that ECAP leads to a significant grain refinement and ultrafine grains down to 100-200 nm are developed after 5 or 6 passes. X-ray diffraction （XRD） analysis indicates that the maj.r part of Mg atoms are in solid solution in the deformed material, and the possible strengthening effect of Mg solute atom clusters or precipitates is neglected. The high hardness of the 6 pass-treated materials comes mainly from grain boundary strengthening, which contributes about 41% to the total strength, while dislocations and Mg solid solution contribute about 24% and 35% to the remaining strength, respectively. Also, the thermal stability of this severely deformed material was investigated by hardness measurements. The material is relatively stable when annealed at a temperature lower than 250 ℃, while annealing at 300 ℃ leads to a rapid softening of the material.

关键词： Al-Mg alloys equal channel angular pressing (ECAP) as-deformed microstructure hardness evolution strengthening thermal stability

DSC analyses of static and dynamic precipitation of an Al–Mg–Si–Cu aluminum alloy

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Progress in Natural Science:Materials International 2015年第2期25卷 153-158页

作者： Manping Liu Zhenj.e Wu Rui Yang j.angtao Wei Yingda Yu P?l C. Skaret hans j. roven School of Materials Science and Engineering Jiangsu Province Key Laboratory of Materials Tribology Jiangsu University Department of Materials Science and Engineering Norwegian University of Science and Technology (NTNU)

In the present investigation, both static and dynamic precipitations of an Al–Mg–Si–Cu aluminum alloy after solid-solution treatment(SST)were comparatively analyzed using differential scanning calorimetry(DSC). Dynamic aging was performed in the SST alloy through equal channel angular pressing(ECAP) at different temperatures of room temperature, 110, 170, 191 and 300 1C. For comparison, static artificial aging was conducted in the SST alloy at 191 1C with two aging times of 4 and 10 h. The DSC analyses reveal that the dynamic precipitation has occurred in the ECAPed samples, while the activation energies associated with the strengthening precipitates in the dynamic samples are considerably higher than the energies in the SST and static aged samples. The higher activation energies are probably attributed to the smaller grains and higher dislocation density developed after ECAP. The results in the present investigation allow the prediction of the type of the dynamic precipitates to influence the strength of the ultrafine grained alloy during ECAP at various temperatures.

关键词： Differential scanning calorimetry Al–Mg–Si–Cu aluminum alloy Dynamic aging Precipitation behaviors Equal channel angular pressing Severe plastic deformation

等通道转角挤压Al-Mg-Si铝合金的动态时效特性和力学性能

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材料研究学报 2016年第10期30卷 721-730页

作者：刘满平韦江涛李毅超江家威姜奎 hans j.roven 江苏大学材料科学与工程学院江苏省高端结构材料重点实验室镇江212013 挪威科技大学材料科学与工程学院挪威特隆赫姆7491

在不同温度对固溶处理后的6061铝合金进行等通道转角挤压(ECAP),以实现动态时效处理。采用X射线衍射(XRD)、差示扫描量热法(DSC)、透射电镜(TEM)及拉伸测试,研究了6061 Al-Mg-Si铝合金的动态时效行为和力学性能。DSC分析结果表明,合金在... 详细信息

在不同温度对固溶处理后的6061铝合金进行等通道转角挤压(ECAP),以实现动态时效处理。采用X射线衍射(XRD)、差示扫描量热法(DSC)、透射电镜(TEM)及拉伸测试,研究了6061 Al-Mg-Si铝合金的动态时效行为和力学性能。DSC分析结果表明,合金在ECAP过程中发生动态时效析出。XRD,DSC和TEM的分析结果均表明,合金在动态时效过程中生成了大量的位错和β″析出相。在不同温度进行ECAP动态时效,制备出几种高韧性(均匀伸长率大于10%)和高强度兼备的6061铝合金。ECAP动态时效铝合金的最高抗拉强度和屈服强度,分别为450 MPa和425 MPa。ECAP铝合金的高强高韧,可归因于ECAP后极细的β''析出相和高密度位错的交互作用。

关键词：金属材料等通道转角挤压大塑性变形 Al-Mg-Si铝合金动态时效力学性能强韧性

高压扭转大塑性变形Al-Mg铝合金中的层错和形变孪晶

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中国有色金属学报 2014年第6期24卷 1383-1392页

作者：刘满平王俊蒋婷慧吴振杰谢学锋刘强 hans j. roven 江苏大学材料科学与工程学院江苏省高端结构材料重点实验室镇江212013 Department of Materials Scienceand Engineering Norwegian University of Science and TechnologyTrondheim 7491Norway

利用高分辨透射电镜研究高压扭转大塑性变形纳米结构Al-Mg铝合金中的位错、层错和形变孪晶。结果表明:在纳米晶和超细晶内均存在高密度的层错和形变孪晶;形成层错的Shockley部分位错可分别由0°纯螺型位错和60°混合位错分解得到;纳米... 详细信息

利用高分辨透射电镜研究高压扭转大塑性变形纳米结构Al-Mg铝合金中的位错、层错和形变孪晶。结果表明:在纳米晶和超细晶内均存在高密度的层错和形变孪晶;形成层错的Shockley部分位错可分别由0°纯螺型位错和60°混合位错分解得到;纳米孪晶既可由晶内层错动态叠加而形成,也可由晶界向晶内不断发射部分位错而向晶内长大,从而分别实验证实了分子动力学模拟预测的均质和非均质形核长大的孪生机制;观察到了由4层层错动态叠加而形成的特殊纳米孪晶。此外,高分辨透射电镜观察表明:在不同滑移面上的层错相交时,形成层错而产生的拖曳部分位错相遇可反应生成压杆位错和Lomer-Cottrell位错锁。依据经典位错理论和晶界发射部分位错的机制,提出了描述超细晶面心立方金属和合金中层错和形变孪晶形核长大的新模型。

关键词：铝合金高压扭转形变孪晶层错位错

Microstructural Characterization of an Al-Mg-Si Aluminum Alloy Processed by Equal Channel Angular Pressing

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Microstructural Characterization of an Al-Mg-Si Aluminum All...

Recycling of automotive aluminum

中国材料大会2012

作者： Zhen Zhang Manping Liu Yingda Yu Pl C. Skaret hans j. roven School of Materials Science and Engineering Jiangsu University Department of Materials Science and Engineering Norwegian University of Science and Technology (NTNU)

ISBN: (纸本)9783037856079;3037856076

In the present work, a peak-aged 6061 Al-Mg-Si aluminum alloy was subj.cted to equal channel angular pressing （ECAP） at 110℃. The microstructure of the sample was characterized by high-resolution transmission electron microscope and weak-beam dark-field method. It was shown that the dislocation density in some local areas is much lower than the average dislocation density expected in the usual alloys processed by severe plastic deformation. High-resolution transmission electron microscope observations indicated that many full dislocations were dissociated into partial dislocations connected by stacking faults. In addition, a Z-shaped defect （i.e., a type of dislocation locks） probably formed by the reactions of the partials in different {111} planes was first observed in the ECAPed alloy. Furthermore, the precipitation behavior and sequence in the present ECAPed sample were identified by high-resolution transmission electron microscopy.

关键词： Al–Mg-Si aluminum alloy Severe plastic deformation Dislocation Z-shaped defects Stacking faults Precipitation

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Transactions of Nonferrous Metals Society of China 2010年第11期20卷 2057-2063页

作者： j.rang CUI hans j.roven Department of Materials Science and Engineering Norwegian University of Science and Technology(NTNU)

With the global warming of concern,the secondary aluminum stream is becoming an even more important component of aluminum production and is attractive because of its economic and environmental *** this work,recycling of automotive aluminum is reviewed to highlight environmental benefits of aluminum recycling,use of aluminum alloys in automotive applications,automotive recycling process,and new technologies in aluminum scrap *** survey shows that newly developed techniques such as laser induced breakdown spectroscopy(LIBS) and solid state recycling provide promising alternatives in aluminum scrap *** with conventional remelting and subsequent refinement,solid state recycling utilizing compression and extrusion at room or moderate temperature can result in significant energy savings and higher metal yield.

关键词： recycling automotive aluminum sorting mechanical separation solid state recycling

Application of EBSD technique to ultrafine grained and nanostructured materials processed by severe plastic deformation:Sample preparation, parameters optimization and analysis

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Transactions of Nonferrous Metals Society of China 2012年第8期22卷 1801-1809页

作者：陈勇军 j.rle Hj.LEN hans j.roven 挪威科技大学材料科学与工程系特隆赫姆7491挪威

With the help of FESEM, high resolution electron backscatter diffraction can investigate the grains/subgrains as small as a few tens of nanometers with a good angular resolution （~0.5°）. Fast development of EBSD speed （up to 1100 patterns per second） contributes that the number of published articles related to EBSD has been increasing sharply year by year. This paper reviews the sample preparation, parameters optimization and analysis of EBSD technique, emphasizing on the investigation of ultrafine grained and nanostructured materials processed by severe plastic deformation （SPD）. Detailed and practical parameters of the electropolishing, silica polishing and ion milling have been summarized. It is shown that ion milling is a real universal and promising polishing method for EBSD preparation of almost all materials. There exists a maximum value of indexed points as a function of step size. The optimum step size depends on the magnification and the board resolution/electronic step size. Grains/subgrains and texture, and grain boundary structure are readily obtained by EBSD. Strain and stored energy may be analyzed by EBSD.

关键词： electron backscatter diffraction (EBSD) sample preparation parameters optimization step size severe plastic deformation (SPD)

Neighbour effects on plant biomass and its allocation for forbs growing in heterogeneous soils

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j.urnal of Plant Ecology 2024年第4期17卷 90-99页

作者： Yongj.e Liu Chunyan Ma Shiting Liu Mingrui Liu Hui Li Mingxia Wang Guoe Li hans j.De Boeck Fuj.ang Hou Zhanhui Tang Zhenxin Li State Key Laboratory of Herbage Improvement and Grassland Agro-ecosystems Key Laboratory of Grassland Livestock Industry InnovationMinistry of Agriculture and Rural AffairsCollege of Pastoral Agriculture Science and TechnologyLanzhou UniversityLanzhou 730020China School of Ecology and Environmental Sciences Yunnan UniversityKunming 650091China Plant and Ecosystems(PLECO) Department of BiologyUniversity of AntwerpWilrijk B-2610Belgium State Environmental Protection Key Laboratory of Wetland Ecology and Vegetation Restoration School of EnvironmentNortheast Normal UniversityChangchun 130117China Key Laboratory of Biodiversity and Environment on the Qinghai-Tibet Plateau Ministry of EducationLhasa 850011China

Focal plants are considerably affected by their neighbouring plants,especially when growing in heterogeneous soils.A previous study on grasses demonstrated that soil heterogeneity and species composition affected plant biomass and above-and belowground allocation *** now tested whether these findings were similar for *** forb species(*** anglica,Limonium bicolor and Suaeda glauca)were grown in pots with three levels of soil heterogeneity,created by alternatively filling resource-rich and resource-poor substrates using small,medium or large patch *** compositions were created by growing these forbs either in monocultures or in *** showed that patch size×species composition significantly impacted shoot biomass,root biomass and total biomass of forbs at different ***,at the pot scale,shoot biomass,root biomass and total biomass increased with increasing patch *** the substrate scale,shoot biomass and total biomass were higher at the large patch size than at the medium patch size,both in resource-rich and resource-poor ***,at the community scale,monocultures had more shoot biomass,root biomass and total biomass than those in the two-or three-species *** results differ from earlier findings on the responses of grasses,where shoot biomass and total biomass decreased with patch size,and more shoot biomass and total biomass were found in resource-rich than resource-poor *** further elucidate the effects of soil heterogeneity on the interactions between neighbour plants,we advise to conduct longer-term experiments featuring a variety of functional groups.

关键词： biomass allocation neighbour effect patch size soil heterogeneity shoot biomass

Novel method of screw extrusion for fabricating Al/Mg(macro-) composites from aluminum alloy 6063 and magnesium granules

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Transactions of Nonferrous Metals Society of China 2014年第12期24卷 3886-3893页

作者： Kristian Gr tta SKORPEN Eirik MAUL Oddvin REISO hans j. rgen roven Department of Materials Science and Engineering Norwegian University of Science and Technology R&D Materials Technology Hydro Aluminium AS Center for Advanced Materials Qatar University

A novel method of screw extrusion was used for producing a bimetal composite Al/Mg from granules containing aluminium alloy 6063 （AA6063） and commercial pure magnesium. Up to 12.5%（mass fraction） pure magnesium was added to the aluminium alloy. In general, the material consisted of a fine grained microstructure. In addition to the phases originating from the input materials, intermetallic phases were observed as islands consisting of the Al2Mg3 phase surrounded byγ-Mg17Al12, throughout the microstructure. The mechanical properties of the extruded material showed a gradual increase in strength with increasing the addition of Mg. The highest registered UTS, well above 350 MPa, was observed for the material containing 10%Mg. Examinations of the fracture surfaces indicated that increasing the magnesium content led to a higher degree of brittle fracture and a gradual change of the fracture micro-mechanisms. The optimization of the post-extrusion processing conditions is still ongoing.

关键词： Al/Mg composites extrusion microstructure mechanical properties

Microstructure evolution and dislocation configurations in nanostructured Al-Mg alloys processed by high pressure torsion

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Transactions of Nonferrous Metals Society of China 2014年第12期24卷 3848-3857页

作者：刘满平蒋婷慧谢学锋刘强李雪峰 hans j.roven 材料科学与工程学院江苏省材料摩擦学重点实验室镇江212013 Department of Materials Science and Engineering Norwegian University of Science and Technology Center for Advanced Materials Qatar University

Microstructure evolution and dislocation configurations in nanostructured Al–Mg alloys processed by high pressure torsion （HPT） were analyzed by transmission electron microscopy （TEM） and high-resolution TEM （HRTEM）. The results show that the grains less than 100 nm have sharp grain boundaries （GBs） and are completely free of dislocations. In contrast, a high density of dislocation as high as 1017 m^-2 exists within the grains larger than 200 nm and these larger grains are usually separated into subgrains and dislocation cells. The dislocations are 60° full dislocations with Burgers vectors of 1/2〈110〉and most of them appear as dipoles and loops. The microtwins and stacking faults （SFs） formed by the Shockley partials from the dissociation of both the 60° mixed dislocation and 0° screw dislocation in ultrafine grains were simultaneously observed by HRTEM in the HPT Al–Mg alloys. These results suggest that partial dislocation emissions, as well as the activation of partial dislocations could also become a deformation mechanism in ultrafine-grained aluminum during severe plastic deformation. The grain refinement mechanism associated with the very high local dislocation density, the dislocation cells and the non-equilibrium GBs, as well as the SFs and microtwins in the HPT Al-Mg alloys were proposed.

关键词： Al-Mg aluminum alloy severe plastic deformation high pressure torsion dislocation configurations grain refinement deformation mechanism