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Microstructure, mechanical properties and wear resistance of an Al–Mg–Si alloy produced by equal channel angular pressing

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Progress in Natural Science:Materials International 2020年第4期30卷 485-493页

作者： Manping Liu jian Chen Yaojun Lin Zhoulei Xue hans j.roven P?l C.Skaret School of Materials Science and Engineering Jiangsu University School of Materials Science and Engineering Wuhan University of Technology Department of Materials Science and Engineering Norwegian University of Science and Technology (NTNU)

Microstructure, mechanical properties and wear resistance in an ultrafine-grained Al–Mg–Si alloy fabricated utilizing a combination of equal channel angular pressing(ECAP) and dynamic aging were investigated in this paper. The results indicated that the grain size of the ECAP alloy was significantly refined, i.e., to ～239 nm after three ECAP passes. Meanwhile, the yield and tensile strength of the ECAPed material reached 340 MPa and445 MPa, respectively, while maintaining a significant uniform elongation of 14%. Wear resistance results demonstrated that the wear rate, wear depth and width of the ECAPed material decreased in comparison with the solution-treated(SST) and peak-aged(T6) conditions under a load range of 5–25 N. The adhesive wear that occurs in the undeformed specimens at 10 N does not appear in the ECAPed specimen at the same load, indicating that the ECAPed specimen delay the appearance of more serious wear mechanisms under certain *** cooperative interaction of high density nano-scale β" precipitates and dislocations resulted in a combination of super-high strength and good work hardening ability which suppressed the extension of cracks between the friction layer and the plastic deformation zone. As a consequence, the combination of ECAP and dynamic aging brings a significant improvement for antifriction performance of the 6061 aluminum alloy.

关键词： Al–Mg–Si aluminum Alloy Equal channel angular pressing Dynamic aging Mechanical properties Wear resistance Wear mechanism Work hardening rate

Special nanostructures in Al-Mg alloys subjected to high pressure torsion

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Transactions of Nonferrous Metals Society of China 2010年第11期20卷 2051-2056页

作者：刘满平 hans j.roven 刘新涛 Maxim MURASHKIN Ruslan Z.VALIEV Tamas UNGáR Levente BALOGH National Engineering Research Center of Light Alloy Net Forming Shanghai Jiao Tong University Department of Materials Science and Engineering Norwegian University of Science and Technology Institute of Physics of Advanced Materials Ufa State Aviation Technical University Department of Materials Physics Etvs University

Deformation twins and stacking faults were observed in nanostructure A1-Mg alloys subjected to high pressure torsion. These observations are surprising because deformation twinnings have never been observed in their coarse-grained counterparts under normal conditions. Experimental evidences are introduced on non-equilibrium grain boundaries, deformation twinnings and partial dislocation emissions from grain boundaries. Some of these features can be explained by the results reported from molecular-dynamics simulations of pure FCC metals. Special emphasis is laid on the recent observations of high density hexagonal and rhombic shaped nanostructures with an average size of 3 nm in the A1-Mg alloys processed by high pressure torsion. A possible formation process of these nanostructures is proposed based on molecular-dynamics simulations.

关键词： aluminum alloys severe plastic deformation high pressure torsion grain boundary structure deformation twinning nanostructures

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 jarle HjELEN 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)

高压扭转大塑性变形Al–Mg合金中的晶界结构

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材料研究学报 2014年第5期28卷 371-379页

作者：蒋婷慧刘满平谢学锋王俊吴振杰刘强 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 挪威科技大学(NTNU)材料科学与工程学院

利用透射电镜和高分辨透射电镜(HRTEM)研究了高压扭转大塑性变形纳米结构Al–Mg合金中的位错和晶界结构。结果表明:对尺寸小于100 nm的晶粒,晶内无位错,其晶界清晰平直;而尺寸大于200 nm的大晶粒通常由几个亚晶或位错胞结构组成,局部位... 详细信息

利用透射电镜和高分辨透射电镜(HRTEM)研究了高压扭转大塑性变形纳米结构Al–Mg合金中的位错和晶界结构。结果表明:对尺寸小于100 nm的晶粒,晶内无位错,其晶界清晰平直;而尺寸大于200 nm的大晶粒通常由几个亚晶或位错胞结构组成,局部位错密度可高达1017m-2,这些位错往往以位错偶和位错环的形式出现。用HRTEM观察到了小角度及大角度非平衡晶界、小角度平衡晶界和大角度Σ9平衡晶界等不同的晶界结构。基于实验结果,分析了局部高密度位错、位错胞和非平衡晶界等在晶粒细化过程中的作用,提出了高压扭转Al–Mg合金的晶粒细化机制。

关键词：金属材料高压扭转大塑性变形铝合金晶界结构非平衡晶界位错

Finite element analysis of strain distribution in ZK60 Mg alloy during cyclic extrusion and compression

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Transactions of Nonferrous Metals Society of China 2012年第8期22卷 1902-1906页

作者：林金保王渠东刘满平陈勇军 hans j.roven 太原科技大学应用科学学院太原030024 上海交通大学轻合金精密成型国家工程研究中心上海200240 挪威科技大学材料科学与工程学院特隆赫敏7491挪威

Finite element method was used to study the strain distribution in ZK60 Mg alloy during multi-pass cyclic extrusion and compression （CEC）. In order to optimize the CEC processing, the effects of friction condition and die geometry on the distribution of total equivalent plastic strain were investigated. The results show that the strain distributions in the workpieces are inhomogeneous after CEC deformation. The strains of the both ends of the workpieces are lower than that of the center region. The process parameters have significant effects on the strain distribution. The friction between die and workpiece is detrimental to strain homogeneity, thus the friction should be decreased. In order to improve the strain homogeneity, a large corner radius and a low extrusion angle should be used.

关键词： cyclic extrusion and compression finite element method friction ZK60 magnesium alloy strain homogeneity

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

Deformation defects and electron irradiation effect in nanostructured Al-Mg alloy processed by severe plastic deformation

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Transactions of Nonferrous Metals Society of China 2012年第8期22卷 1810-1816页

作者：刘满平孙少纯 hans j.roven 于瀛大张桢 Maxim MURASHKIN Ruslan Z.VALIEV 江苏大学材料科学与工程学院镇江212013 Department of Materials Science and Engineering Norwegian University of Science and Technology(NTNU)NO-7491TrondheimNorway Department of Materials Science and Engineering Norwegian University of Science and Technology(NTNU)NO-7491TrondheimNorway Institute of Physics of Advanced Materials Ufa State Aviation Technical UniversityUfa 450000Russia

In order to explore the exact nature of deformation defects previously observed in nanostructured Al-Mg alloys subjected to severe plastic deformation, a more thorough examination of the radiation effect on the formation of the planar defects in the high pressure torsion （HPT） alloys was conducted using high-resolution transmission electron microscopy （HRTEM）. The results show that high density defects in the HRTEM images disappear completely when these images are exposed under the electron beam for some duration of time. At the same time, lattice defects are never observed within no-defect areas even when the beam-exposure increases to the degree that holes appear in the areas. Therefore, it is confirmed that the planar defects observed in the HPT alloys mainly result from the significant plastic deformation and are not due to the radiation effect during HRTEM observation.

关键词： Al-Mg alloy severe plastic deformation high pressure torsion electron irradiation deformation defects transmission electron microscopy

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

Grain refinement of magnesium alloys processed by severe plastic deformation

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Transactions of Nonferrous Metals Society of China 2014年第12期24卷 3747-3754页

作者：陈勇军王渠东林金保刘满平 jarle HjELEN hans j.roven 上海交通大学轻合金精密成型国家工程研究中心上海200030 Department of Materials Science and Engineering Norwegian University of Science and Technology ERC for Revolutionizing Metallic Biomaterials North Carolina A&T State University 太原科技大学应用科学学院太原030024 江苏大学材料科学与工程学院镇江212013 Center for Advanced Materials Qatar University

Grain refinement of AZ31 Mg alloy during cyclic extrusion compression （CEC） at 225-400 ℃ was investigated quantitatively by electron backscattering diffraction （EBSD）. Results show that an ultrafine grained microstructure of AZ31 alloy is obtained only after 3 passes of CEC at 225 ℃. The mean misorientation and the fraction of high angle grain boundaries （HAGBs） increase gradually by lowering extrusion temperature. Only a small fraction of {101^-2} twinning is observed by EBSD in AZ31 Mg alloys after 3 passes of CEC. Schmid factors calculation shows that the most active slip system is pyramidal slip {101^-1}〈1120〉and basal slip {0001}〈1120〉 at 225-350 ℃ and 400 ℃, respectively. Direct evidences at subgrain boundaries support the occurrence of continuous dynamic recrystallization （CDRX） mechanism in grain refinement of AZ31 Mg alloy processed by CEC.

关键词： magnesium alloys grain refinement continuous dynamic recrystallization (CDRX) electron backscattering diffraction(EBSD) cyclic extrusion compression (CEC)