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Towards designing high mechanical performance low-alloyed wrought magnesium alloys via grain boundary segregation strategy:A review

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Journal of Magnesium and Alloys 2024年第5期12卷 1774-1791页

作者： Zhi Zhang Jinshu Xie Jinghuai Zhang xu-sheng yang Ruizhi Wu Key Laboratory of Superlight Material and Surface Technology Ministry of EducationCollege of Materials Science and Chemical EngineeringHarbin Engineering UniversityHarbin 150001China State Key Laboratory of Ultra-Precision Machining Technology Department of Industrial and Systems EngineeringThe Hong Kong Polytechnic UniversityHung HomKowloonHong KongChina Hong Kong Polytechnic University Shenzhen Research Institute Shenzhen 518060China

Low-alloyed magnesium(Mg)alloys have emerged as one of the most promising candidates for lightweight ***,their further application potential has been hampered by limitations such as low strength,poor plasticity at room temperature,and unsatisfactory *** address these challenges,grain refinement and grain structure control have been identified as crucial factors to achieving high performance in low-alloyed Mg *** effective way for regulating grain structure is through grain boundary(GB)*** review presents a comprehensive summary of the distribution criteria of segregated atoms and the effects of solute segregation on grain size and growth in Mg *** analysis encompasses both single element segregation and multi-element co-segregation behavior,considering coherent interfaces and incoherent ***,we introduce the high mechanical performance low-alloyed wrought Mg alloys that utilize GB segregation and analyze the potential impact mechanisms through which GB segregation influences materials *** upon these studies,we propose strategies for the design of high mechanical performance Mg alloys with desirable properties,including high strength,excellent ductility,and good formability,achieved through the implementation of GB *** findings of this review contribute to advancing the understanding of grain boundary engineering in Mg alloys and provide valuable insights for future alloy design and optimization.

关键词： Magnesium alloys Grain boundary segregation High strength High plasticity High formability

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Significant annealing-induced hardening effect in nanolaminate d-nanotwinne d(CrCoNi)_(97.4)Al_(0.8)Ti_(1.8)me dium-entropy alloy by severe cold rolling

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Journal of Materials Science & Technology 2024年第3期170卷 156-166页

作者： Shuqing Yuan Hui Fu Lei Qian Chi Fai Cheung xu-sheng yang State Key Laboratory of Ultra-precision Machining Technology Department of Industrial and Systems EngineeringThe Hong Kong Polytechnic UniversityHung HomKowloonHong KongChina Hong Kong Polytechnic University Shenzhen Research Institute Shenzhen 518060China

Due to the easy coarsening caused by poor thermal stability,the verified annealing-induced hardening in nanograined metals can only maintain at a relatively low-temperature *** this study,a nanolam-inated(CrCoNi)_(97.4)Al_(0.8)Ti_(1.8)medium-entropy alloy with an average lamellae thickness of∼20 nm embedded by thinner nanotwins was fabricated by severe cold rolling to achieve superior thermal *** with the conventional nanotwinned CrCoNi with nanotwins inside ultra-fined grains,the hier-archical nanolaminated-nanotwinned(CrCoNi)_(97.4)Al_(0.8)Ti_(1.8) exhibits a significant annealing-induced hard-ening effect,i.e.,hardness increasing from∼250 HV in the original specimen to∼500 HV in the cold-rolled status and finally∼630 HV after annealing at 600℃for 1 *** microstructure characterizations reveal that the reduced dislocation density and formation of L1_(2)ordered domain are mainly responsible for such hardening effect,which is facilitated by the effectively suppressed coarsening with annealing temperature,i.e.,slow detwinning process and well-retained low-angle nanolamellar *** coarsening mechanisms from the cold-rolled nanolamellae to the fully recrystallized micro-equiaxed structures under the annealing temperatures ranging from 400 to 800℃ were also elucidated by atomic observations.

关键词： Annealing-induced hardening Thermal stability Nanolaminated-nanotwinned structure CrCoNi Detwinning Grain boundary migration

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Atomistic simulations of the surface severe plastic deformation-induced grain refinement in polycrystalline magnesium:The effect of processing parameters

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Journal of Magnesium and Alloys 2022年第5期10卷 1242-1255页

作者： Xiaoye Zhou Hui Fu Ji-Hua Zhu xu-sheng yang Guangdong Province Key Laboratory of Durability for Marine Civil Engineering School of Civil EngineeringShenzhen UniversityShenzhenGuangdong 518060China State Key Laboratory of Ultra-precision Machining Technology Advanced Manufacturing Technology Research CentreDepartment of Industrial and Systems EngineeringThe Hong Kong Polytechnic UniversityHung HomKowloonHong KongChina Hong Kong Polytechnic University Shenzhen Research Institute ShenzhenChina

Magnesium(Mg)based alloys are promising candidates for many applications,but their untreated surfaces usually have low strength and *** this study,a single point diamond turning(SPDT)technique was applied to refine the grain size and improve the mechanical properties of the surface layers of Mg-Li *** refining grains in the topmost layer to the nanometer scale(~60 nm),the surface hardness was found to be enhanced by approximately 60%.The atomic plastic deformation process during the SPDT was then studied by the real-time atomistic molecular dynamics(MD)simulations.A series of MD simulations with different combinations of parameters,including rake angle,cutting speed and cutting depth,were conducted to understand their influences on the microstructural evolution and associated plastic deformation mechanisms on the surface layer of the *** MD simulation results suggest that using increased rake angle,cutting speed and cutting depth can help to achieve better grain *** simulation results,which provide atomic-level details of the deformation mechanism,can assist the parameter design for the SPDT techniques to achieve the high-performance heterogeneous nanostructured materials.

关键词： Mg alloy Grain refinement Surface severe plastic deformation MD simulations

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Atomic-scale dissecting the formation mechanism of gradient nanostructured layer on Mg alloy processed by a novel high-speed machining technique

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Journal of Materials Science & Technology 2021年第23期82卷 227-238页

作者： Hui Fu Xiaoye Zhou Bo Wu Lei Qian xu-sheng yang State Key Laboratory of Ultra-precision Machining Technology Advanced Manufacturing Technology Research CentreDepartment of Industrial and Systems EngineeringThe Hong Kong Polytechnic UniversityHung HomKowloonHong KongChina Hong Kong Polytechnic University Shenzhen Research Institute ShenzhenChina Guangdong Province Key Laboratory of Durability for Marine Civil Engineering School of Civil EngineeringShenzhen UniversityShenzhen 518060China

Severe plastic deformation(SPD)-induced gradient nanostructured(GNS)metallic materials exhibit superior mechanical performance,especially the high strength and good *** this study,a novel high-speed machining SPD technique,namely single point diamond turning(SPDT),was developed to produce effectively the GNS layer on the hexagonal close-packed(HCP)structural Mg *** high-resolution transmission electron microscopy observations and atomistic molecular dynamics simulations were mainly performed to atomic-scale dissect the grain refinement process and corresponding plastic deformation mechanisms of the GNS *** was found that the grain refinement process for the formation of the GNS Mg alloy layer consists of elongated coarse grains,lamellar fine grains with deformation-induced-tension twins and contraction twins,ultrafine grains,and nanograins with the grain size of~70 nm along the direction from the inner matrix to ***,experiment results and atomistic simulations reveal that these deformation twins are formed by gliding twinning partial dislocations that are dissociated from the lattice dislocations piled up at grain *** corresponding deformation mechanisms were evidenced to transit from the deformation twinning to dislocation slip when the grain size was below 2.45μ***,the Hall-Petch relationship plot and the surface equivalent stress along the gradient direction estimated by finite element analysis for the SPDT process were incorporated to quantitatively elucidate the transition of defo rmation mechanisms during the grain refinement *** findings have implications for the development of the facile SPD technique to construct high strength-ductility heterogeneous GNS metals,especially for the HCP metals.

关键词： Gradient nanostructured Mg alloy High-speed machining Deformation twinning High-resolution transition electron microscopy Hall-Petch relationship

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超越“服务”与“引领”:数字化时代职业教育与社区教育虚拟一体化发展模式探索

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广东开放大学学报 2024年第3期33卷 1-6页

作者：刘楚佳梁鹏徐胜阳广州城市职业学院广东广州511370 华南师范大学广东广州510631 广州市教育研究院广东广州510030

探索职业教育和社区教育机构汇聚融通,是建设学习型社会与学习型城市的应有之义。目前,学界对职业教育与社区教育的关系定位主要集中在职业教育“服务”或“引领”社区教育方面。然而,无论是服务还是引领,都未能充分理解数字时代的“大... 详细信息

探索职业教育和社区教育机构汇聚融通,是建设学习型社会与学习型城市的应有之义。目前,学界对职业教育与社区教育的关系定位主要集中在职业教育“服务”或“引领”社区教育方面。然而,无论是服务还是引领,都未能充分理解数字时代的“大教育”概念及技术可能性。基于此,可探索职业教育与社区教育虚拟一体化融合模式,依托数字化技术与平台,形成“一套基本人马,两项主要职能”的组织样态,搭建居中协调机构,形成以项目为引领的资源开发、教育教学、学校管理整体运行机制,最终实现职业教育与社区教育的融合。

关键词：社区教育职业教育高职院校教育数字化融合模式

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Interactions between Pre-strain and Dislocation Structures and Its Effect on the Hydrogen Trapping Behaviors

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Acta Metallurgica Sinica(English Letters) 2023年第7期36卷 1193-1202页

作者： Rongjian Shi Yanqi Tu Liang yang Saiyu Liu Shani yang Kewei Gao xu-sheng yang Xiaolu Pang Beijing Advanced Innovation Center for Materials Genome Engineering School of Materials Science and EngineeringUniversity of Science and Technology BeijingBeijing100083China School of Mathematics and Physics University of Science and Technology BeijingBeijing100083China Department of Industrial and Systems Engineering The Hong Kong Polytechnic UniversityHung HomKowloonHong KongChina Hong Kong Polytechnic University Shenzhen Research Institute Shenzhen518057China Key Laboratory for Advanced Materials of Ministry of Education School of Materials Science and EngineeringTsinghua UniversityBeijing100084China

This work investigated the effect of pre-strain and microstructures and their interactions on hydrogen trapping behaviors in case of 1-GPa high-strength martensitic steel Fe-0.05C-0.30Si-1.10Mn-3.50Ni-0.53Cr-0.50Mo-0.03 V(wt%).We found that the trapped reversible and trapped irreversible hydrogen contents increased significantly after applying a pre-strain of 5%,with an increase in the trapped reversible hydrogen content from 0.6 ppm in the original sample to 2.1 *** hydrogen desorption activation energy also showed a slight *** microstructural evolution revealed that the concomitant dislocation cell-twin duplex microstructure with high-density tangled dislocations after pre-strain substantially increased the trapped reversible hydrogen ***,the tangled dislocations pinned by the nanoprecipitates acted as deep irreversible hydrogen traps,increasing the trapped hydrogen at high temperatures after applying 5%*** findings provide an expanded understanding of the hydrogen trapping behaviors of pre-strained microstructures.

关键词： Hydrogen embrittlement Hydrogen trapping Pre-strain Deformed microstructure High-strength steel

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Enhancing (de)hydrogenation kinetics properties of the Mg/MgH_(2) system by adding ANi_(5)(A=Ce,Nd,Pr,Sm,and Y) alloys via ball milling

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Journal of Rare Earths 2021年第8期39卷 1010-1016页

作者： Wenfang Liao Wenbin Jiang xu-sheng yang Hui Wang Liuzhang Ouyang Min Zhu Guangdong Provincial Key Laboratory of Advanced Energy Storage Materials School of Materials Science and EngineeringSouth China University of TechnologyGuangzhou 510641China China-Australia Joint Laboratory for Energy&Environmental Materials Key Laboratory of Fuel Cell Technology of Guangdong ProvinceGuangzhou 510641China Advanced Manufacturing Technology Research Centre Department of Industrial and Systems EngineeringThe Hong Kong Polytechnic UniversityHung HornKowloonHong KongChina Hong Kong Polytechnic University Shenzhen Research Institute Shenzhen 518057China

Magnesium(Mg)-based alloys have already been widely studied as the hydrogen storage materials because of their high reversible hydrogen storage capacity,low cost,light weight,***,the poor de/hydrogenation kinetic properties dramatically hinder the practical *** this work,the MgH_(2)-ANi_(5)(A=Ce,Nd,Pr,Sm,and Y) composites were prepared by a high-energy ball milling *** can effectively refine the particle size thus improving the kinetic *** results reveal that the MgH_(2)-ANi_(5) composites mainly consist of Mg_(2)NiH_(4),MgH_(2) and rare earth(RE) hydride,which will be dehydrogenated to form Mg_(2)Ni,Mg and stable RE hydride ***,the asmilled MgH_(2)-ANi_(5)(A=Ce,Nd,Pr,Sm,and Y) composites with various A-elements can respectively contribute to a reversible hydrogen storage capacity of 6.16 wt%,5.7 wt%,6.21 wt%,6.38 wt%,and 6.5 wt%at a temperature of 300℃,and show much better kinetic properties in comparison to the pure MgH_(2) without any ***-situ formed Mg_(2) Ni and stable RE hydride(such as CeH_(2.73) and YH_(2)) might act as effective catalysts to significantly improve the hydrogen storage properties of MgH_(2).The present work provides a guideline on improving the kinetic properties of the Mg-based hydrogen storage alloys.

关键词： Mg-based hydrogen storage alloy Kinetic properties ANi_(5) Additives Rare earths

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Laser surface treatment-introduced gradient nanostructured TiZrHfTaNb refractory high-entropy alloy with significantly enhanced wear resistance

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Journal of Materials Science & Technology 2022年第15期110卷 43-56页

作者： Jiasi Luo Wanting Sun Ranxi Duan Wenqing yang K.C.Chan Fuzeng Ren xu-sheng yang Department of Industrial and Systems Engineering Advanced Manufacturing Technology Research CentreThe Hong Kong Polytechnic UniversityHung HomKowloonHong KongChina Department of Materials Science and Engineering Southern University of Science and TechnologyShenzhen 518055China The Hong Kong Polytechnic University Shenzhen Research Institute Shenzhen 518060China

Heterogeneous gradient nanostructured metals have been shown to achieve the strength-ductility synergy, thus potentially possessing the enhanced tribological performance in comparison with their homogeneous nanograined counterparts. In this work, a facile laser surface remelting-based surface treatment technique is developed to fabricate a gradient nanostructured layer on a TiZrHfTaNb refractory highentropy alloy. The characterization of the microstructural evolution along the depth direction from the matrix to the topmost surface layer shows that the average grain size in the ~100 μm-thick gradient nanostructured layer is dramatically refined from the original ~200 μm to only ~8 nm in the top surface layer. The microhardness is therefore gradually increased from ~240 HV in matrix to ~650 HV in the topmost surface layer, approximately 2.7 times. Noticeably, the original coarse-grained single-phase bodycentered-cubic TiZrHfTaNb refractory high-entropy alloy is gradually decomposed into TiNb-rich bodycentered-cubic phase, TaNb-rich body-centered-cubic phase, ZrHf-rich hexagonal-close-packed phase and TiZr Hf-rich face-centered-cubic phase with gradient distribution in grain size along the depth direction during the gradient refinement process. As a result, the novel laser surface treatment-introduced gradient nanostructured TiZrHfTaNb refractory high-entropy alloy demonstrates the significantly improved wear resistance, with the wear rate reducing markedly by an order of magnitude, as compared with the as-cast one. The decomposed multi-phases and gradient nanostructures should account for the enhanced wear resistance. Our findings provide new insights into the refinement mechanisms of the laser-treated refractory high-entropy alloys and broaden their potential applications via heterogeneous gradient nanostructure engineering.

关键词： Laser surface treatment Refractory high-entropy alloy Gradient nanostructure Wear resistance High-resolution transmission electron microscopy

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In situ formed ultrafine metallic Ni from nickel(Ⅱ) acetylacetonate precursor to realize an exceptional hydrogen storage performance of MgH_(2)-Ni-EG nanocomposite

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Journal of Magnesium and Alloys 2023年第9期11卷 3174-3185页

作者： Shaoyang Shen Liuzhang Ouyang Jiangwen Liu Hui Wang xu-sheng yang Min Zhu School of Materials Science and Engineering and Key Laboratory of Advanced Energy Storage Materials of Guangdong Province South China University of TechnologyGuangzhou510641China China-Australia Joint Laboratory for Energy&Environmental Materials Key Laboratory of Fuel Cell Technology of Guangdong ProvinceGuangzhouGuangzhou510641China Advanced Manufacturing Technology Research Centre Department of Industrial and Systems EngineeringThe Hong Kong Polytechnic UniversityHung HomKowloonHong KongChina Research Institute for Smart Energy The Hong Kong Polytechnic UniversityHung HomKowloonHong KongChina

It has been well known that doping nano-scale catalysts can significantly improve both the kinetics and reversible hydrogen storage capacity of MgH_(2) . However, so far it is still a challenge to directly synthesize ultrafine catalysts(e.g., < 5 nm), mainly because of the complicated chemical reaction processes. Here, a facile one-step high-energy ball milling process is developed to in situ form ultrafine Ni nanoparticles from the nickel acetylacetonate precursor in the MgH_(2) matrix. With the combined action of ultrafine metallic Ni and expanded graphite(EG), the formed MgH_(2)-Ni-EG nanocomposite with the optimized doping amounts of Ni and EG can still release 7.03 wt.% H_(2) within 8.5 min at 300 ℃ after 10 cycles. At a temperature close to room temperature(50 ℃), it can also absorb 2.42 wt.% H_(2) within 1 h. It can be confirmed from the microstructural characterization analysis that the in situ formed ultrafine metallic Ni is transformed into Mg_(2)Ni/Mg_(2)NiH_4 in the subsequent hydrogen absorption and desorption cycles. It is calculated that the dehydrogenation activation energy of the MgH_(2)-Ni-EG nanocomposite is also reduced obviously in comparison with the pure MgH_(2) . Our work provides a methodology to significantly improve the hydrogen storage performance of MgH_(2) by combining the in situ formed and uniformly dispersed ultrafine metallic catalyst from the precursor and EG.

关键词： Hydrogen storage Magnesium hydride Nickel precursor Size effect Expanded graphite

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An extraordinary-performance gradient nanostructured Hadfield manganese steel containing multi-phase nanocrystalline-amorphous core-shell surface layer by laser surface processing

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Journal of Materials Science & Technology 2023年第3期134卷 209-222页

作者： Wanting Sun Jiasi Luo Yim Ying Chan J.H.Luan xu-sheng yang Research Institute for Advanced Manufacturing Department of Industrial and Systems EngineeringThe Hong Kong Polytechnic UniversityHung HomHong KongChina Hong Kong Branch of National Rail Transit Electrification and Automation Engineering Technology Research Center The Hong Kong Polytechnic UniversityHung HomHong KongChina Department of Materials Science and Engineering City University of Hong KongHong KongChina

Reducing grain size(*** the fraction of grain boundaries)could effectively strengthen nanograined metals but inevitably sacrifices the ductility and possibly causes a strengthening-softening transition below a critical grain *** this work,a facile laser surface remelting-based technique was employed and optimized to fabricate a∼600μm-thick heterogeneous gradient nanostructured layer on an austenitic Hadfield manganese steel,in which the average grain size is gradually decreased from∼200μm in the matrix to only∼8 nm in the nanocrystalline-amorphous core-shell topmost ***-scale microstructural characterizations dissected the gradient refinement processes along the gradient direction,*** from the dislocations activities and twinning in sub-region to three kinds of martensitic transformations,and finally a multi-phase nanocrystalline-amorphous core-shell structural *** tests(***,bulk-specimen tensile,and micro-pillar compression)were conducted along the gradient *** confirms a tensile strength of∼1055 MPa and ductility of∼10.5%in the laser-processed ***,the core-shell structural surface maintains ultra-strong(tensile strength of∼1.6 GPa,micro-pillar compressive strength of∼4 GPa at a strain of∼8%,and nanoindentation hardness of∼7.7 GPa)to overcome the potential strengthening-softening *** significant strengthening effects are ascribed to the strength-ductility synergetic effects-induced extra work hardening ability in gradient nanostructure and the well-maintained dislocation activities inside extremely refined nanograins in the multi-phase nanocrystalline-amorphous core-shell structural surface,which are evidenced by atomic-scale observations and theoretical *** study provides a unique hetero-nanostructure through a facile laser-related technique for extraordinary mechanical performance.

关键词： Laser surface processing Hadfield manganese steel Gradient nanostructure Nanocrystalline-amorphous Martensitic transformation

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