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学者姓名：刘克
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Abstract ：
In this study, we investigated the microstructures and mechanical properties of Mg-6Gd-1Er-0.5Zr (GE61K) sheets. The results show that the rolling temperature has a remarkable influence on microstructures, age-hardening responses and mechanical properties of GE61K sheets. The microstructures varies with the increase in rolling temperatures, i.e. microstructures were dominated by the mixture of dynamic re-crystallized (DRXed) grains and un-DRXed grains at 300 degrees C, by DRXed grains at 350 degrees C, and by un-DRXed grains at 400 degrees C and 450 degrees C. Rolling at 300 degrees C leads to a formation of the bimodal microstructure which contains equilibrium Mg-5(Gd, Er) precipitates and a large number of dislocations. These dislocations leads to a formation of novel chain-like precipitates which comprise dominant beta', beta'(F) (or beta'(T)), tail-like "hexagonal ring" layers, individual "zig-zag" chain and individual "hexagonal ring", eventually improving age-hardening responses. The chain-like precipitates are beneficial for achieving a good strength-ductility balance by dividing the matrix into nano-scale units and forming subsequent honeycomb structures. As a result, the R-300 degrees C sheet shows good mechanical properties, i.e. ultimate tensile strength (UTS) of 367 +/- 3 MPa, yield strength (YS) of 349 +/- 4 MPa and elongation (EL) of 9.1 +/- 1.5%, respectively. However, such strength-ductility balance is destroyed sharply as soon as the rolling temperature increases to 400 degrees C because of the microstructure variations. (C) 2021 Elsevier B.V. All rights reserved.
Keyword ：
Mg-Gd-Er-Zr sheets Mg-Gd-Er-Zr sheets Mechanical properties Mechanical properties Age-hardening response Age-hardening response Precipitate chain Precipitate chain
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| GB/T 7714 | Liu, Ke , Lou, Feng , Yu, Zijian et al. Microstructures and mechanical properties of Mg-6Gd-1Er-0.5Zr alloy sheets produced with different rolling temperatures [J]. | JOURNAL OF ALLOYS AND COMPOUNDS , 2022 , 893 . |
| MLA | Liu, Ke et al. "Microstructures and mechanical properties of Mg-6Gd-1Er-0.5Zr alloy sheets produced with different rolling temperatures" . | JOURNAL OF ALLOYS AND COMPOUNDS 893 (2022) . |
| APA | Liu, Ke , Lou, Feng , Yu, Zijian , Wang, Zhaohui , Li, Shubo , Du, Xian et al. Microstructures and mechanical properties of Mg-6Gd-1Er-0.5Zr alloy sheets produced with different rolling temperatures . | JOURNAL OF ALLOYS AND COMPOUNDS , 2022 , 893 . |
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Abstract ：
In this study, a high-performance Mg-8Gd-2Y-1Zn-6Li (wt%) alloy having a TYS of 202 +/- 2.6 MPa, UTS of 243 +/- 2.1 MPa and EL of 10.7 +/- 2.3% was successfully fabricated by casting, heat treatment and hot extrusion. The effects of intermetallic compounds on microstructure and mechanical properties were deeply investigated. The results show that the studied alloy consists of coarse deformed alpha-Mg grains with (0001) basal texture, fine recrystallized beta-Li grains with (002) texture and three Mg3RE phase variants, which are bulk Mg3RE phase with a size range of 10-30 mu m, spot Mg3RE phase with a size range of 1-2 mu m and spherical Mg3RE phase with a size range of 0.3-1 mu m, respectively. The spherical Mg3RE phase has a strong dispersion strengthening effect, while the bulk Mg3RE phase acts as crack resources and deteriorates the ductility. A novel island like beta(1R) phase (FCC, a = 0.78 nm) is found for the first time in the Mg-Gd-Li based alloys. It has a coherent ((1) over bar 12)beta(1R//)(10 (1) over bar0)(alpha) interface at the broad facet and a semi-coherent ((1) over bar 11)beta(1R)//(11 (2) over bar0)alpha interface at the end facet. The beta(1R) phase transforms from beta(H) phase at the semi-coherent interface by atomic shear of RE and Mg atoms. The beta(1R) phase provides a significant precipitation strengthening effect to the studied alloy, while the dissolution of beta(1R )phase results in the age-softening phenomenon. The high-performance of the studied alloy is mainly attributed to the alpha/beta( )duplex structure, three Mg3RE phase variants, and beta(1R )phase. (C) 2021 Elsevier B.V. All rights reserved.
Keyword ：
Intermetallic compounds Intermetallic compounds Mg-Li alloys Mg-Li alloys Mechanical properties Mechanical properties Hot extrusion Hot extrusion
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| GB/T 7714 | Yu, Zijian , Liu, Linlin , Mansoor, Adil et al. Microstructures and mechanical properties of as-extruded Mg-8Gd-2Y-1Zn-6Li alloy [J]. | JOURNAL OF ALLOYS AND COMPOUNDS , 2021 , 864 . |
| MLA | Yu, Zijian et al. "Microstructures and mechanical properties of as-extruded Mg-8Gd-2Y-1Zn-6Li alloy" . | JOURNAL OF ALLOYS AND COMPOUNDS 864 (2021) . |
| APA | Yu, Zijian , Liu, Linlin , Mansoor, Adil , Liu, Ke , Li, Shubo , Du, Wenbo . Microstructures and mechanical properties of as-extruded Mg-8Gd-2Y-1Zn-6Li alloy . | JOURNAL OF ALLOYS AND COMPOUNDS , 2021 , 864 . |
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Abstract ：
In electromagnetic (EM) optimization of microwave design, a computationally bad starting point usually leads the local optimization process to be stuck into local optimum, which does not satisfy the design specifications. In this situation, global optimization methods can be an alternative to achieve the final optimal solution. However, global optimization methods always suffer from a relatively low convergence rate. To address this problem, we propose an efficient EM optimization technique with a novel parallel local sampling strategy and Bayesian optimization (BO) for microwave applications in this article. We develop a new parallel local sampling strategy to increase the exploitation ability near the potential optimal solution in each optimization iteration and improve the convergence of the entire optimization process. The local sampling range in each iteration is determined based on the derivative information of the current potential optimal solution. While conventional BO only uses the information of potential optimal solutions in each iteration during optimization, we propose to exploit both the generated local samples and the potential optimal solutions together to build a surrogate model and guide the optimization. Therefore, the exploration and exploitation during the proposed EM optimization are well balanced, and the entire EM optimization process is effectively accelerated in comparison to other existing global methods. Examples of EM optimizations of microwave components are used to demonstrate the proposed technique.
Keyword ：
Bayes methods Bayes methods Wireless communication Wireless communication Bayesian optimization (BO) Bayesian optimization (BO) Optimization Optimization Data models Data models electromagnetic (EM) optimization electromagnetic (EM) optimization Optimization methods Optimization methods Probabilistic logic Probabilistic logic Microwave theory and techniques Microwave theory and techniques microwave applications microwave applications parallel local sampling parallel local sampling
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| GB/T 7714 | Na, Weicong , Liu, Ke , Cai, Haocheng et al. Efficient EM Optimization Exploiting Parallel Local Sampling Strategy and Bayesian Optimization for Microwave Applications [J]. | IEEE MICROWAVE AND WIRELESS COMPONENTS LETTERS , 2021 , 31 (10) : 1103-1106 . |
| MLA | Na, Weicong et al. "Efficient EM Optimization Exploiting Parallel Local Sampling Strategy and Bayesian Optimization for Microwave Applications" . | IEEE MICROWAVE AND WIRELESS COMPONENTS LETTERS 31 . 10 (2021) : 1103-1106 . |
| APA | Na, Weicong , Liu, Ke , Cai, Haocheng , Zhang, Wanrong , Xie, Hongyun , Jin, Dongyue . Efficient EM Optimization Exploiting Parallel Local Sampling Strategy and Bayesian Optimization for Microwave Applications . | IEEE MICROWAVE AND WIRELESS COMPONENTS LETTERS , 2021 , 31 (10) , 1103-1106 . |
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Abstract ：
The influence of primary and secondary extrusion on the microstructure and mechanical properties of the Mg-12Gd-2Er-0.4Zr alloy was investigated. After the primary extrusion, incomplete dynamic recrystallization (DRX) had led to the formation of non-homogenous grain structure with fine equiaxed grain and coarse grains, while the secondary extrusion refined the microstructure remarkably and further improved the mechanical properties. Moreover, the secondary phases were broken into small particles and distributed along the extrusion direction (ED). The secondary extruded (EX2) alloy had the smallest grain size similar to 3.0 mu m and exhibited the best balance of strength and elongation (ultimate tensile strength (UTS) of 305 +/- 5.7 MPa, tensile yield strength (TYS) of 258 +/- 10 MPa, and elongation (EL) of 31 +/- 2.4%). The excellent EL was mainly ascribed to the fully refined dynamic recrystallized (DRXed) grains after the secondary extrusion. Furthermore, the aged EX2 alloy (AEX2) exhibited an excellent balance of strength and elongation (TYS of 382 +/- 11 MPa, UTS of 423 +/- 6.2 MPa, and EL of 7.6 +/- 0.9%). The alloy strengthening was mainly attributed to the refined grains and strong precipitation strengthening.
Keyword ：
age hardening age hardening secondary extrusion secondary extrusion mechanical properties mechanical properties microstructure microstructure magnesium alloy magnesium alloy
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| GB/T 7714 | Mansoor, Adil , Du, Wenbo , Yu, Zijian et al. Effect of Secondary Extrusion on the Microstructure and Mechanical Properties of Mg-12Gd-2Er-0.4Zr Alloy [J]. | JOURNAL OF MATERIALS ENGINEERING AND PERFORMANCE , 2021 , 30 (12) : 8996-9007 . |
| MLA | Mansoor, Adil et al. "Effect of Secondary Extrusion on the Microstructure and Mechanical Properties of Mg-12Gd-2Er-0.4Zr Alloy" . | JOURNAL OF MATERIALS ENGINEERING AND PERFORMANCE 30 . 12 (2021) : 8996-9007 . |
| APA | Mansoor, Adil , Du, Wenbo , Yu, Zijian , Ding, Ning , Fu, Junjian , Jia, Linyue et al. Effect of Secondary Extrusion on the Microstructure and Mechanical Properties of Mg-12Gd-2Er-0.4Zr Alloy . | JOURNAL OF MATERIALS ENGINEERING AND PERFORMANCE , 2021 , 30 (12) , 8996-9007 . |
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Abstract ：
In this study, the Mg-4Y-1Gd-1Nd-xCa-1Zn-0.3Zr (x = 0 and 0.4 wt%) cast alloys with low rare earth concentration were prepared in different routes of heat treatments, and their microstructures and mechanical properties were investigated. The Mg-4Y-1Gd-1Nd-1Zn-0.4Ca-0.3Zr cast alloy with ultimate tensile strength (UTS) of 264 +/- 7.8 MPa, tensile yield strength (TYS) of 153 +/- 1.2 MPa and elongation to failure (EL) of 17.2 +/- 1.2% was successfully developed by appropriate heat treatment. The improved mechanical performance was attributed to the combined strengthening effects of fine grains, -Mg24RE5, beta', beta(1), gamma' and LPSO phases. In the heat treatment process, cooling method of T4 treatment affected the microstructure, which consequently determined the mechanical properties air cooling, rather than water cooling, gave rise to the formation of gamma' phase in the alloy without Ca addition. However, Ca addition facilitated the formation of gamma' phase, and the gamma' phase precipitated in the alloy after T4 treatment either by water cooling or by air cooling, but the air cooling increased the number density of gamma' phase in comparison to the water cooling. Although the gamma' phase strengthened the studied alloys, the formation of gamma' phase inhibited the precipitatition of beta' and beta(1) phases in the following T6 treatment, and consequently reduced the strengthening effect of beta' and beta(1) phases. The results showed that the mechanical performance of the studied alloys was largely determined by the precipitation of gamma' phase, which was regulated by the Ca addition and the cooling method of T4 treatment.
Keyword ：
Mechanical properties Mechanical properties Magnesium alloy Magnesium alloy Microstructure Microstructure Rare earth Rare earth Heat treatment Heat treatment
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| GB/T 7714 | Yu, Zijian , Xu, Xi , Du, Baotian et al. Precipitate Characteristics and Mechanical Performance of Cast Mg-6RE-1Zn-xCa-0.3Zr (x=0 and 0.4 wt%) Alloys [J]. | ACTA METALLURGICA SINICA-ENGLISH LETTERS , 2021 , 35 (4) : 596-608 . |
| MLA | Yu, Zijian et al. "Precipitate Characteristics and Mechanical Performance of Cast Mg-6RE-1Zn-xCa-0.3Zr (x=0 and 0.4 wt%) Alloys" . | ACTA METALLURGICA SINICA-ENGLISH LETTERS 35 . 4 (2021) : 596-608 . |
| APA | Yu, Zijian , Xu, Xi , Du, Baotian , Shi, Kang , Liu, Ke , Li, Shubo et al. Precipitate Characteristics and Mechanical Performance of Cast Mg-6RE-1Zn-xCa-0.3Zr (x=0 and 0.4 wt%) Alloys . | ACTA METALLURGICA SINICA-ENGLISH LETTERS , 2021 , 35 (4) , 596-608 . |
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Abstract ：
Mg-Zn-Zr (ZK60) alloys reinforced by ultra-low content (< 0.1 wt%) of graphene nanoplatelets (GNPs) were fabricated via stirring cast and extrusion processes. In composites, GNPs thoroughly dispersed and continuously combined with Mg matrix at the interface, beneficial for the load and heat transfer of composites. The static and dynamic mechanical properties of GNP/ZK60 composite were investigated and respectively compared with those of ZK60 alloy. With only 0.04 wt% addition, GNP nanofillers improved the impact toughness twice that of ZK60 matrix up to 17 J cm(-2). In tensile test, GNP(0.04)/ZK60 composite performed enhanced tensile yield strength of 256 MPa, improved by 62% than ZK60 alloy. Although grain boundary is commonly considered as defect to deteriorate transport property, GNP(0.04)/ZK60 composite with largely refined grain size conducted superior thermal conductivity of 139.4 W.(mK)(-1) than ZK60 alloy (132.2 W.(mK)(-1)) at room temperature. The dispersed GNPs in matrix provide beneficial networks for efficient load and heat transfer. This work explores that graphene reinforcement is an effective way to simultaneously improve the mechanical and thermal properties of Mg alloys for enlarged applications.
Keyword ：
Graphene Graphene Mechanical property Mechanical property Impact toughness Impact toughness Interface Interface Thermal conductivity Thermal conductivity Magnesium Magnesium
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| GB/T 7714 | Du, Xian , Du, Wenbo , Wang, Zhaohui et al. Simultaneously improved mechanical and thermal properties of Mg-Zn-Zr alloy reinforced by ultra-low content of graphene nanoplatelets [J]. | APPLIED SURFACE SCIENCE , 2021 , 536 . |
| MLA | Du, Xian et al. "Simultaneously improved mechanical and thermal properties of Mg-Zn-Zr alloy reinforced by ultra-low content of graphene nanoplatelets" . | APPLIED SURFACE SCIENCE 536 (2021) . |
| APA | Du, Xian , Du, Wenbo , Wang, Zhaohui , Liu, Ke , Li, Shubo . Simultaneously improved mechanical and thermal properties of Mg-Zn-Zr alloy reinforced by ultra-low content of graphene nanoplatelets . | APPLIED SURFACE SCIENCE , 2021 , 536 . |
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Abstract ：
Magnesium alloys, as a new type of biodegradable medical metal material, have a promising application in the field of vascular stents. However, the poor deformability of Mg alloys due to hexagonal close-packed (hcp) structure makes it difficult to fabricate their thin tube. In this study, the micro-tubes of Mg-4Zn-0.2Mn-0.2Ca alloy, a new type of degradable magnesium alloy, with 3.1 similar to 3.6 mm in outer diameter and 0.25 similar to 0.4 mm in wall thickness were prepared by hot extrusion-drawing composite process. The microstructure evolution and mechanical properties of the one with 3.6 mm in outer diameter, 0.4 mm in wall thickness show that the crystal slip, twins and recrystallization occur during the plastic deformation of the tubes, and the work hardening is significant. This drawn tube exhibits a tensile strength of 427.3 MPa, yield strength of 383.4 MPa, and elongation of 5.2%. After annealing at 300 degrees C for 30 min, the microstructure becomes uniform and the elongation increases to 18.0%, which is conducive to the fabrication of vascular stents.
Keyword ：
drawing drawing extrusion extrusion mechanical properties mechanical properties Mg-Zn-Mn-Ca alloy Mg-Zn-Mn-Ca alloy microstructure evolution microstructure evolution
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| GB/T 7714 | Fu Junjian , Du Wenbo , Du Xian et al. Fabrication and Properties of Magnesium Alloy Microtubes for Vascular Stent [J]. | RARE METAL MATERIALS AND ENGINEERING , 2020 , 49 (10) : 3576-3581 . |
| MLA | Fu Junjian et al. "Fabrication and Properties of Magnesium Alloy Microtubes for Vascular Stent" . | RARE METAL MATERIALS AND ENGINEERING 49 . 10 (2020) : 3576-3581 . |
| APA | Fu Junjian , Du Wenbo , Du Xian , Liu Ke , Li Shubo , Fu Jinlong et al. Fabrication and Properties of Magnesium Alloy Microtubes for Vascular Stent . | RARE METAL MATERIALS AND ENGINEERING , 2020 , 49 (10) , 3576-3581 . |
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Abstract ：
Existing photonic couplers are limited by either large footprint or long interaction length. Here a highly efficient and ultracompact three-port trench-based coupler (TBC) is proposed on an InP platform in terms of the frustrated total internal reflection principle. A single slash-shaped narrow trench located at the "T" intersection of two InP/InGaAsP multiquantum well ridge waveguides forms the coupler. The finite-difference time-domain numerical method is utilized to optimize the parameterization of the couplers, such as splitting ratios and efficiency versus trench widths, lengths, locations, and angles. A single-mode 2 mu m wide ridge waveguide coupler having a high aspect ratio trench filled with Al2O3 was fabricated and characterized at 1.55 mu m wavelength. The "trench-first" fabrication process is optimized to reduce its inherent insertion loss (IL), showing the IL within a range of 0.3-0.5 dB. The devices can outperform the state-of-the-art trench couplers by >= similar to 24 times the figure of merit. These TBCs are thus promising candidates for applications in the next generation of photonic integrated circuits. (C) 2020 Optical Society of America
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| GB/T 7714 | Zhang, Chenglong , Guan, Baolu , Qi, Bing et al. Highly efficient and ultracompact InP/InGaAsP three-port trench-based couplers [J]. | APPLIED OPTICS , 2020 , 59 (3) : 825-832 . |
| MLA | Zhang, Chenglong et al. "Highly efficient and ultracompact InP/InGaAsP three-port trench-based couplers" . | APPLIED OPTICS 59 . 3 (2020) : 825-832 . |
| APA | Zhang, Chenglong , Guan, Baolu , Qi, Bing , Liu, Ke . Highly efficient and ultracompact InP/InGaAsP three-port trench-based couplers . | APPLIED OPTICS , 2020 , 59 (3) , 825-832 . |
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Abstract ：
主要介绍近年来北京工业大学在高强韧稀土镁合金的研究进展,通过添加稀土元素铒(Er)和钆(Gd)开发系列耐热Mg-Zn-Er合金以及高强韧Mg-Gd-Er(-Zn)-Zr合金.研究获得Mg-Zn-Er合金中I相和W相的形成范围及其对合金抗蠕变性能的影响规律;通过成分优化和复合加工方式改善Mg-Gd-Er(-Zn)-Zr合金的力学性能,为设计和制备高性能镁合金材料提供参考依据.
Keyword ：
塑性变形 塑性变形 显微组织 显微组织 稀土元素 稀土元素 镁合金 镁合金 相 相 高性能 高性能
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| GB/T 7714 | 杜文博 , 贾林玥 , 王朝辉 et al. 北工大高强稀土镁合金研究进展 [J]. | 北京工业大学学报 , 2020 , 46 (6) : 710-718 . |
| MLA | 杜文博 et al. "北工大高强稀土镁合金研究进展" . | 北京工业大学学报 46 . 6 (2020) : 710-718 . |
| APA | 杜文博 , 贾林玥 , 王朝辉 , 刘轲 , 李淑波 , 杜宪 . 北工大高强稀土镁合金研究进展 . | 北京工业大学学报 , 2020 , 46 (6) , 710-718 . |
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Abstract ：
An extruded Mg-4Zn-0.2Mn-0.2Ca alloy was developed as potential biodegradable bone-plate due to its excellent biocompatibility. Long term in vitro immersion in Hank's solution and bending test were used to evaluate the degradability and the mechanical integrity of the alloy. The results revealed that the degradation rate of the bone-plate increased in the first 7 days and then decreased with the prolonged immersion time before it finally reached a steady stage (about 0.84 mm/a) after immersion for 90 days. The bending strength after immersion for 60 days was 67.6 MPa, indicating that the bone-plate could support certain mechanical load after long term degradation. The formation of corrosion pits after degradation stemmed from the separation of the continuously distributed second phases from Mg matrix under the action of micro-galvanic couples. As a result, the mechanical performance of Mg-4Zn-0.2Mn-0.2Ca alloy was aggravated owing to the corrosion holes on its surface.
Keyword ：
in vitro degradation in vitro degradation corrosion behaviors corrosion behaviors bending strength bending strength bone-plate bone-plate magnesium alloys magnesium alloys
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| GB/T 7714 | Cheng, Yuan-fen , Du, Wen-bo , Liu, Ke et al. Mechanical properties and corrosion behaviors of Mg-4Zn-0.2Mn-0.2Ca alloy after long term in vitro degradation [J]. | TRANSACTIONS OF NONFERROUS METALS SOCIETY OF CHINA , 2020 , 30 (2) : 363-372 . |
| MLA | Cheng, Yuan-fen et al. "Mechanical properties and corrosion behaviors of Mg-4Zn-0.2Mn-0.2Ca alloy after long term in vitro degradation" . | TRANSACTIONS OF NONFERROUS METALS SOCIETY OF CHINA 30 . 2 (2020) : 363-372 . |
| APA | Cheng, Yuan-fen , Du, Wen-bo , Liu, Ke , Fu, Jun-jian , Wang, Zhao-hui , Li, Shu-bo et al. Mechanical properties and corrosion behaviors of Mg-4Zn-0.2Mn-0.2Ca alloy after long term in vitro degradation . | TRANSACTIONS OF NONFERROUS METALS SOCIETY OF CHINA , 2020 , 30 (2) , 363-372 . |
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