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Microscopic strengthening and failure mechanisms of graphene/Al composite: A molecular dynamics study

Progress in Natural Science:Materials International 2024年第4期34卷 720-730页

作者： Huijuan Guo Xiaoyan Sun Liang Chen Yuhui Zhao Kaiqiang Shen Xiangshan Kong State Key Laboratory of Advanced Equipment and Technology for Metal Forming Shandong University Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials (Ministry of Education) Shandong University Intelligent Manufacturing Department Yantai Engineering and Technology College

This study focused on the microscopic strengthening and failure mechanisms of the Al matrix reinforced by graphene(Gr), and the effects of number of layers, chirality, and arrangement of Gr were calculated based on the molecular dynamics simulation. The results revealed that the Young's modulus and yield strength were significantly enhanced by the addition of Gr. In Gr/Al composites with monolayer Gr, the zigzag Gr exhibited a better ultimate strain than the armchair Gr, indicating that the plastic deformation was affected by the chirality, and the dislocation hindrance and load transfer were the dominated strengthening mechanisms. The crack in the armchair Gr was limited to follow straight paths, while that in zigzag Gr extended in a petal-like manner across multiple directions. In Gr/Al composite with multilayer Gr, the dispersing Gr showed a stronger strengthening effect than the stacking Gr, and the strengthening effect increased with increasing the volume fraction of Gr. The dispersing Gr strongly hindered the movement of dislocations, while the Al matrix in the composite with stacking Gr could retard the folding of Gr. Moreover, Gr nanosheets fractured layer by layer rather than simultaneously fractured in the Gr/Al composites with multilayer Gr.

关键词： Molecular dynamics Gr/Al composites Strengthening Failure

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Application of Rapid Manufacturing Process & equipment System for Large Complex Light Alloy Structural Components 75

Application of Rapid Manufacturing Process & Equipment Syste...

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75th World Foundry Congress, WFC 2024

作者： Hong, Haichun State Key Laboratory of Advanced Forming Technology and Equipment Beijing National lnnovation Institute of Lightweight Ltd. Beijing China

This paper introduces the key technologies of light alloy fire-retardant sand printing and forming processes, including material system optimization, feedstock ratios, mixing methods, and in-house developed additive manufacturing equipment. Through the shape-controllable composite mold technology, the challenges of matching and precise regulation between mold and casting properties have been addressed, enabling rapid manufacturing through mold-less composite forming. The impact of multi-material composite molds on the performance of castings has been investigated, leading to the invention of corresponding control principles and assembly methods. Furthermore, addressing the influence of sand parameters on forming quality and tool wear, formulas comprising materials such as quartz sand, zircon sand, and chromite sand have been devised, achieving synergistic optimization of mold properties. Finally, for future needs, ceramic core additive manufacturing equipment has been developed to further advance material forming technology. © 2024 75th World Foundry Congress, WFC 2024. All rights reserved.

关键词： Foundry sand

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Revealing effects of powder reuse for LPBF-fabricated NiTi shape memory alloys

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Frontiers of Materials Science 2024年第4期18卷 191-201页

作者： Xiang Li Meng Zhou Sihui Peng Xiaonan Chen Xueyuan Ge Bingmin Huang Lishan Cui Shijie Hao College of New Energy and Materials China University of PetroleumBeijing 102249China State Key Laboratory of Advanced Forming Technology and Equipment China Machinery Institute of Advanced Materials Co.Ltd.Zhengzhou 450001China Jiangsu Smart Advanced Material Technology Co. Ltd.Xuzhou 221000China

In metal-based additive manufacturing processes,such as laser powder bed fusion(LPBF),the powder utilization is often less than 50%.Considering the cost efficiency,powder reuse is needed for an economical and sustainable LPBF *** intermetallic compounds,LPBF-fabricated NiTi alloys are characterized with phase transformation behaviors,mechanical properties and functions that are very sensitive to possible changes in powder characteristics caused through reuse,but the exact effects are still poorly ***,the LPBF process has been repeated ten times using the virgin powder supplement *** show that the oxygen content of NiTi powders rises from 370 to 752.3 ppm with the enhancement of the reuse cycle *** oxidation enhances the laser absorptivity of the powder bed,leading to an increase in surface roughness and porosity of NiTi *** to the specimens made from virgin powders,the mechanical property and shape memory function of specimens made from reused powders are degraded,mainly attributed to the oxygen impurity and deteriorated forming *** study allows making better decisions with regard to powder reuse in the development of performance-critical NiTi parts fabricated through LPBF.

关键词： laser powder bed fusion NiTi shape memory alloy powder reuse microstructure mechanical property

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Determination of interfacial heat transfer coefficient at the frozen sand mold casting process of ZL101 alloy

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Journal of Materials Science & technology 2024年第27期194卷 28-42页

作者： Shijie Dong Zhongde Shan Feng Lin Haoqin Yang Xiao Liang Department of Mechanical Engineering Tsinghua UniversityBeijing 100084China State Key Laboratory of Advanced Forming Technology and Equipment China Academy of Machinery Science and TechnologyBeijing 100037China Key Laboratory for Advanced Materials Processing Technology Ministry of Education of ChinaBeijing 100084China College of Mechanical and Electrical Engineering Nanjing University of Aeronautics and AstronauticsNanjing 210016China College of Material Science and Technology Nanjing University of Aeronautics and AstronauticsNanjing 210016China

Compared to the resin sand mold casting process, frozen casting is more environmentally friendly, providing a better working environment and enhanced supercooling degree. The interfacial heat transfer coefficient (IHTC) between frozen sand mold and metal is an important parameter that significantly influences the final mechanical properties and microstructure of the castings. This paper solved the inverse heat conduction problem using the finite difference method (FDM). In addition, the conjugate gradient method (CGM) was adopted to calculate the temperature distribution and heat flux in the molten metal. At the same time, the particle swarm optimization algorithm (PSO) was used in temperature distribution determination in frozen sand mold. The interfacial heat transfer coefficient (IHTC) was estimated during the solidification of ZL101. The results showed a good agreement between calculated and experimental data, obtaining accurate casting interface temperature Tm, frozen sand mold interface temperature Ts, heat flux q, and IHTC. The analysis of the IHTC variation revealed a water content value within the range of 4 wt.% to 5 wt.% resulted in IHTC in two types of interpretation, called ‘fluctuation type’ and ‘turning type’.

关键词： Frozen sand mold Interfacial heat transfer coefficient(IHTC) Finite difference method(FDM) Conjugate gradient method(CGM) Particle swarm optimization(PSO)

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Finite element simulation of wear-resistant steel ball forging process 5

Finite element simulation of wear-resistant steel ball forgi...

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2024 5th International Conference on advanced Materials and Intelligent Manufacturing, IcamIM 2024

作者： Pan, Peng Ge, Feng Yang, Ming Yu, Jinxi Zuo, Lingli Beijing National Innovation of Lightweight Ltd. Beijing101400 China State Key Laboratory for Advanced Forming Technology and Equipment China Academy of Machinery and Technology Beijing101400 China

Deform-3D software was used to analyse the forming characteristics of wear-resistant steel balls, material fluidity, stress-strain distribution, load-time curve, and break coefficient of three kinds of forging billets in the forging process. It was concluded that with the reduction of the height of the original billet, the damage coefficient of the middle position of the billet decreased during the final stage of billet forming. The forging ratio of the blank should be appropriately reduced to reduce the risk of forming defects in the forging process. 2025 Published under licence by IOP Publishing Ltd.

关键词： Billets (metal bars)

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Numerical Simulation and Experimental Investigation on Friction and Lubrication Behaviors of Chevron Micro-Textured Valve Plate/Cylinder Block Interface With Various Area Densities

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Journal of Tribology 2025年第7期147卷 072201页

作者： Chen, Luanxia Liu, Zhanqiang Huang, Haihong Zhu, Yingying School of Mechanical Engineering Hefei University of Technology Hefei230009 China Key Laboratory of Green Design and Manufacturing of Mechanical Industry Hefei University of Technology Hefei230009 China School of Mechanical Engineering Shandong University Jinan250061 China State Key Laboratory for High-end Equipment and Advanced Technology of Metal Forming Shandong University Jinan250061 China

As the critical friction pairs of swashplate-type axial piston pumps, the cylinder block/valve plate lubricating interface is the primary source of friction, wear, and leakage in axial piston pumps. Surface micro-texturing has been widely employed in cylinder block/valve plate conjunctions to ameliorate tribological performance. However, little research has been conducted to investigate the influence of chevron micro-texture area density on the tribological behaviors and lubricating properties of cylinder block/valve plate interface both experimentally and numerically. In this article, the chevron micro-textures with various area densities were manufactured on H62 brass by micro-milling and subsequently characterized with a laser scanning confocal microscope (LSCM). The friction and wear performance of H62 brass/38CrMoAl conjunctions were obtained via disc-on-disc tribological tests to simulate the cylinder block/valve plate lubricating interface. Moreover, the load-carrying capacity of untextured and chevron micro-textured samples was numerically investigated under hydrodynamic lubrication. It was found that the chevron micro-textured surface with an area density of 30.1% displayed the lowest friction coefficient and the shallowest wear depth. Although the load-carrying capacity of chevron micro-textured samples with a high dimple area density was larger, the severe stress concentration induced by the reduced micro-texture spacing caused the increment and large fluctuations of friction coefficient. Copyright © 2024 by ASME.

关键词： Friction

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Effect of tempering temperature on microstructure and mechanical properties of 4Cr13VTi steel 9

Effect of tempering temperature on microstructure and mechan...

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2023 9th International Forum on Manufacturing technology and Engineering Materials, ICMTEM 2023

作者： Pan, Peng Wang, Jinnan Yang, Ming Beijing National Innovation of Lightweight Ltd. Beijing101400 China State Key Laboratory for Advanced Forming Technology and Equipment China Academy of Machinery and Technology Beijing101400 China

To optimize the tempering process of 40Cr13VTi steel containing V and Ti, the effect of tempering temperature on microstructure, precipitation, and properties of 40Cr13VTi stainless steel has been studied. Optical microscope (OM), scanning electron microscopy (SEM), and energy dispersive spectrometer (EDS) were used to analyze microstructure and precipitates. Tensile, impact, and hardness testing tests were performed to test the mechanical properties of 40Cr13VTi martensitic stainless steel. The research results indicate that as the increase of tempering temperature, the carbides precipitated gradually increase, and the shape gradually changes from particle to flake, which is consistent with the direction of the original martensite flat surface, and most of them concentrate at the martensite boundary. When the tempering temperature is 350°C, 40Cr13VTi martensitic stainless steel obtains the best comprehensive properties, strength, impact toughness (IT), and hardness which are 1360 MPa, 1717 MPa, 8.5 J/cm2, and 45.1 HRC respectively. © Published under licence by IOP Publishing Ltd.

关键词： Martensite

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稀有金属材料与工程 2025年第2期54卷 311-318页

作者： Zhang Wenxin Zhang Xiankun Shi Lei Li Shengli Jiang Yuanning Wu Chuansong State Key Laboratory of Advanced Equipment and Technology for Metal Forming Shandong UniversityJinan 250061China Key Laboratory for Liquid-Solid Structure Evolution&Processing of Materials Ministry of EducationShandong UniversityJinan 250061China

Friction stir lap welding of AA2195 Al-Li alloy and Ti alloy was conducted to investigate the formation,microstructure,and mechanical properties of the *** show that under different welding parameters,with the decrease in welding heat input,the weld surface is *** Ti/Al joint interface is flat without obvious Ti and Al mixed structure,and the hook structure is not formed under optimal *** to the enhanced breaking effect of the stirring head,the hook structural defects and intermetallic compounds are more likely to form at the Ti/Al interface at high rotational speed of 1000 r/min,thereby deteriorating the mechanical properties of *** the heat input is beneficial to hardness enhancement of the aluminum alloy in the weld nugget *** the optimal parameters of rotation speed of 800 r/min and welding speed of 120 mm/min,the maximum tensile shear strength of joint is 289 N/mm.

关键词： Ti/Al dissimilar welding friction stir lap welding Ti alloy Al-Li alloy interface bonding mechanical property

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The Vibration Characteristics Analysis on Operating Arm of Rectangular Coordinate Robot 2

The Vibration Characteristics Analysis on Operating Arm of R...

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2nd International Conference on Mechanical Engineering, Intelligent Manufacturing and Automation technology, MEMAT 2022

作者： Han, Wei Wang, Shaozong Zhang, Qian Li, Zhou He, Qin State Key Laboratory of Advanced Forming Technology and Equipment China Academy of Machinery Science and Technology Beijing China

ISBN: (纸本)9783800757619

The operating arm of rectangular coordinate robot is the key component to perform tasks. Its vibration characteristics have an important impact on the operation accuracy and work efficiency of the robot, so it is worth studying and analysing. Based on the deformation displacement relationship of robot operating arm under different time states, this paper proposed the kinematic description method of radial motion of operating arm, and established the dynamic control model of radial motion operating arm by using Hamilton variational principle and modal superposition method. This model focused on the relationship between the driving acceleration, load mass and the vibration characteristics of the operating arm. Through the analytical calculation and finite element analysis of the dynamic model, the influence of these two factors on the vibration amplitude, modal frequency and other modal characteristics of the robot operating arm were explored respectively. The results provided a theoretical basis for the vibration control of the robot operating arm. © VDE VERLAG GMBH ∙ Berlin ∙ Offenbach.

关键词： Robots

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Effect of Ag coatings prepared by magnetron sputtering on the wear properties of Ti6Al4V alloy 11

Effect of Ag coatings prepared by magnetron sputtering on th...

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2024 11th International Conference on advanced Manufacturing technology and Materials Engineering, AMTME 2024

作者： Huang, Xinyu Rong, Wenjuan Wang, Jialin Beijing National Innovation Institute Lightweight. Ltd. Beijing10140 China State Key Laboratory of Advanced Forming Technology and Equipment China Academy of Machinery Science and Technology Beijing101400 China

Ag coatings were prepared on the surface of Ti6Al4V alloy by magnetron sputtering technique, and the effects of different Ag target power and sputtering time on the coating properties were investigated. The coating thickness was firstly measured by a step meter, and then the coatings obtained under different parameters were characterized by Vickers hardness tester, scratch tester, and friction wear tester. The variation in the furnace temperature had a significant effect on the hardness of the coatings: the coating thickness increased slightly with increasing temperature, but the increase was not dramatical. The Vickers hardness of the coatings showed a tendency to increase and then decrease with increasing temperature, reaching a peak at 150 ℃. The hardness of the coatings was found to increase with increasing temperature and then decrease with increasing temperature. Scratch tests further showed that the coatings prepared in the range of 150 ℃ to 180 ℃ exhibited superior bond strength with the substrate. The wear morphology of the coatings showed that the coatings prepared at 150 ℃ had the best wear resistance. At this temperature, the flaking of the coating due to adhesive wear was significantly reduced, and the depth of scratches due to abrasive wear was also reduced. The variation of the Ag target power also had a significant effect on the hardness of the coatings. As the target power increases, the coating thickness increases significantly, and the Vickers hardness increases and then decreases, reaching a maximum at 12 W. The coatings prepared at 10 W show better performance in terms of scratch and wear patterns. These experimental results provide strong data support for the subsequent preparation of Ti6Al4V joint prostheses. © 2024 Institute of Physics Publishing. All rights reserved.

关键词： Bond strength (materials)

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