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Thermal Analysis of Laser Chemical Machining: Part I: Static Irradiation

Materials Sciences and Applications 2017年第10期8卷 685-707页

作者： Hamza Messaoudi sandro eckert Frank Vollertsen BIAS—Bremer Institut für angewandte Strahltechnik Bremen Germany Faculty of Production Engineering-Mechanical Engineering & Process Engineering University of Bremen Bremen Germany

The laser chemical machining is a non-conventional substractive processing method. It is based on the laser-activation of a material dissolution of metals in electrolyte ambient via local-induced temperature gradients and allows a gentle and smooth processing of especially temperature-sensitive metals. However, the material removal is characterized by a narrow process window and is restricted by occurring disturbances, which are supposed to be related to the localized electrolyte boiling. In order to control the removal quality and avoid disturbances, the correlation between the laser-induced temperatures and the resulting removal geometry has to be better understood. In this work an analytical modeling of the laser-induced temperatures at the surface of titanium based on a Green-function approach is presented. The main influencing factors (laser, electrolyte, material) as well as possible heat transfer into the electrolyte are included and discussed. To verify the calculated temperatures, single spot experiments are performed and characterized for titanium in phosphoric acid solution within laser irradiation of 1 s. The correlation between the temperature distribution and the resulting removal geometry is investigated based on a spatial superposition. Thereby, the bottom limit temperature is found to range between 63°C and 70°C whereas the upper limit is related to the nucleate boiling regime. Based on the performed correlation an indicator is identified to predict the ruling removal regime and thereby to reduce the experimental expenditure.

关键词： Laser Micro Machining Laser Chemical Removal Modeling Temperature Process Stability Titanium

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Recent advancements in thermal conductivity of magnesium alloys

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Journal of Magnesium and Alloys 2024年第5期12卷 1687-1708页

作者： Hao Lv Jun Tan Qian Yuan Fanglei Wang Yunxuan Zhou Quan Dong Aitao Tang Jürgen eckert Bin Jiang Fusheng Pan National Engineering Research Center for Magnesium Alloys College of Materials Science and EngineeringChongqing UniversityChongqing 400044China National Key Laboratory of Advanced Casting Technologies Chongqing UniversityChongqing 400044China Department of Materials Science Chair of Materials PhysicsMontanuniversität LeobenJahnstraße 12Leoben A-8700Austria Erich Schmid Institute of Materials Science Austrian Academy of SciencesJahnstraße 12Leoben A-8700Austria

As highly integrated circuits continue to advance,accompanied by a growing demand for energy efficiency and weight reduction,materials are confronted with mounting challenges pertaining to thermal conductivity and lightweight *** virtue of numerous intrinsic mechanisms,as a result,the thermal conductivity and mechanical properties of the Mg alloys are often inversely related,which becomes a bottleneck limiting the application of Mg *** on several effective modification methods to improve the thermal conductivity of Mg alloys,this paper describes the law of how they affect the mechanical properties,and clearly indicates that peak aging treatment is one of the best ways to simultaneously enhance an alloy's thermal conductivity and mechanical *** the most frequently used Mg alloy,cast alloys exhibit substantial potential for achieving high thermal ***,recent reports indicate that hot deformation can significantly improve the mechanical properties while maintaining,and potentially slightly enhancing,the alloy's thermal *** presents a meaningful way to develop Mg alloys for applications in the field of small-volume heat dissipation components that require high *** comprehensive review begins by outlining standard testing and prediction methods,followed by the theoretical models used to predict thermal conductivity,and then explores the primary influencing factors affecting thermal *** review summarizes the current development status of Mg alloys,focusing on the quest for alloys that offer both high thermal conductivity and high *** concludes by providing insights into forthcoming prospects and challenges within this field.

关键词： Mg alloy Thermal conductivity Mechanical properties Solute atom Second phase

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Localization of rare earth ions in an inhomogeneous magnetic field toward their magnetic separation

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Journal of Rare Earths 2022年第10期40卷 1598-1605页

作者： Barbara Fritzsche Zhe Lei Xuegeng Yang Kerstin eckert TU Dresden Institute of Process Engineering and Environmental Technology01062DresdenGermany Helmholtz-Zentrum Dresden-Rossendorf(HZDR) Institute of Fluid DynamicsBautzner Landstrasse 40001328DresdenGermany

Efficient extraction and recycling methods are an important issue for rare earth elements(REE). The significant differences in their magnetic moments make magnetic separation a promising step. Although the magnetic field gradient manipulation of ions seemed to be impossible, the robust enrichment of some paramagnetic RE ions was found in the vicinity of the magnet. The studies in recent years resolved the physical paradox of why, despite the Brownian motion of the ions, there is a reproducible enrichment of RE ions in magnetic field gradients. The existence of trigger process and energy barrier was ***, these studies usually used only high paramagnetic ions, e.g., Dy(Ⅲ) or Ho(Ⅲ). This work verifies the theory of the possible magnetic separation for 8 different rare earth ions, respectively. For this purpose, concentration distribution in rare earth chloride solutions were measured using a MachZehnder interferometer. The magnetic field was assured by a Halbach configuration to enhance the effect. The results show the classification of RE solutions into 2 classes: Class I contains the REs with low magnetic moment, whereas Class II includes the REs of high magnetic moment. Only the latter group shows the enrichment of ions in the vicinity of the magnet which encourages the implementation of magnetic separation into existing hydrometallurgical technology to enhance the selectivity of REE.

关键词： Magnetic separation Paramagnetic rare earth ions Enrichment Halbach array Interferometry Aqueous solution

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Selective Laser Melting of Al-7Si-0.5Mg-0.5Cu:Effect of Heat Treatment on Microstructure Evolution,Mechanical Properties and Wear Resistance

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Acta Metallurgica Sinica(English Letters) 2022年第3期35卷 389-396页

作者： Pei Wang Sijie Yu Jaskarn Shergill Anil Chaubey Jürgen eckert Konda Gokuldoss Prashanth Sergio Scudino Additive Manufacturing Institute College of Mechatronics and Control EngineeringShenzhen UniversityShenzhen 518060China Institute for Complex Materials IFW DresdenHelmholtzstraBe 2001069 DresdenGermany Institute of Minerals and Materials Technology(IMMT) Bhubaneshwar 751013OrissaIndia Erich Schmid Institute of Materials Science Austrian Academy of SciencesJahnstraBe 128700 LeobenAustria Department of Materials Science Chair of Materials PhysicsMontanuniversitat LeobenJahnstraBe 128700 LeobenAustria Department of Mechanical and Industrial Engineering Tallinn University of TechnologyEhitajete tee 519086 TallinnEstonia CBCMT School of Mechanical EngineeringVellore Institute of TechnologyVellore.Tamil Nadu 632014India Adjunct With National University of Science and Technology aMISi Sa Leninsky Prosp..4.119049 MoscowRussia

Al-7Si-0.5Mg-0.5Cu alloy specimens have been fabricated by selective laser melting(SLM).In this study,the effects of solution treatment,quenching,and artifi cial aging on the microstructural evolution,as well as mechanical and wear properties,have been *** as-prepared samples show a heterogeneous cellular microstructure with two different cell sizes composed ofα-Al and Si *** solution-treated and quenched(SQ)heat treatment,the cellular microstructure disappears,and coarse and lumpy Si phase precipitates and a rectangular Cu-rich phase were *** aging after solution-treated and quenched(SQA)heat treatment causes the formation of nanosized Cu-rich *** asprepared SLMs sample has good mechanical properties and wear resistance(compressive yield strength:215±6 MPa and wear rate 2×10^(-13)m^(3)/m).The SQ samples with lumpy Si particles have the lowest strength of 167±13 MPa and the highest wear rate of 6.18×10^(1-13)m^(3)/*** formation of nanosized Cu-rich precipitates in the SQA samples leads to the highest compressive yield strength of 233±6 MPa and a good wear rate of 5.06×10^(-13)m^(3)/m.

关键词： Selective laser melting Al-Si-Cu-Mg alloy Heat treatment Microstructure Mechanical properties Wear properties

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Orientation-dependent Hydrodynamic Instabilities from Chemo-Marangoni Cells to Large Scale Interfacial Deformations

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Chinese Journal of Chemical Engineering 2007年第5期15卷 748-753页

作者：石英 Kerstin eckert State Key Laboratory of Multiphase Flow in Power Engineering Xi＇an Jiaotong University Xi＇an 710049 China Institute for Aerospace Engineering Technische Universitat Dresden D-01062 Dresden Germany

在化学和 interfacial-tension-driven 水动力学不稳定性之间的相互影响试验性地被学习了。系统手头上由分开的二不能混合的液体组成一开始界面的反应在发生在 situ 生产表面活化剂的飞机接口。系统的动力学关于严肃的向量取决于 Hele ... 详细信息

在化学和 interfacial-tension-driven 水动力学不稳定性之间的相互影响试验性地被学习了。系统手头上由分开的二不能混合的液体组成一开始界面的反应在发生在 situ 生产表面活化剂的飞机接口。系统的动力学关于严肃的向量取决于 Hele 杂木林房间的取向，这被识别。如果 Hele 杂木林房间垂直地被放，有精力旺盛的传送对流的 Marangoni 房间沿着一个将近平面的接口在两个阶段发展。然而，如果 Hele 杂木林房间被倾斜离开严肃，在系统的不稳定性被大规模描绘有和 chemo-Marangoni 传送对流的时间空间的频率的界面的变丑。焦点在从细胞的模式的转变的探索上到大规模界面的变丑。

关键词： Marangoni 对流胞元大尺度界面变形动力学不稳定性

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Micro-annulus generation under downhole conditions: Insights from three-dimensional staged finite element analysis of cement hardening and wellbore operations

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Journal of Rock Mechanics and Geotechnical Engineering 2020年第6期12卷 1185-1200页

作者： Weicheng Zhang Andreas eckert Department of Geosciences and Geological and Petroleum Engineering Missouri University of Science and TechnologyRollaMOUSA

A micro-annulus(MA)is defined as a high permeability zone or gap initiating/occurring at the casingcement and cement-formation interfaces during the wellbore life *** MA can significantly compromise wellbore integrity by establishing enhanced fluid flow *** study uses a staged finite element approach to simulate wellbore integrity during various loading steps of wellbore operations under downhole *** emphasis is placed on the processes of cement poro-elastic property evolution,volume variation,and pore pressure variation as part of the cement hardening *** resulting state of stress during the life cycle of a typical injection well(***,completion,and injection)is analyzed to assess the onset and evolution of micro-annuli at various interfaces of the composite wellbore system under downhole *** results show that cement shear failure is observed at the casing-cement interface during pressure testing(excessive wellbore pressure);and tensile debonding failure initiates at the cement-formation interface due to cement shrinkage during hardening and injection-related cooling(thermal cycling).Sensitivity analyses considering several parameters show that:(1)the degree of poro-elastic bulk shrinkage has significant implications for both shear and tensile failure initiation e the less the cement shrinks,the less likely the failure initiation is;(2)cement integrity increases with increasing depth;(3)cement pore pressure evolution has significant implications for tensile failure e if cement pore pressure decreases more,higher temperature differences can be sustained before an MA occurs;and(4)cement temperature fluctuations during hardening promote initiation of debonding *** summary,the results presented indicate that establishing downhole conditions to quantitatively analyze MA generation is *** results are different compared to laboratory studies without considering/simulating downhole *** kno

关键词： Micro-annulus Debonding Staged finite element analysis Cement hardening Poro-elastic bulk shrinkage Pore pressure Temperature fluctuation

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Experimental and theoretical studies on two-dimensional vanadium carbide hybrid nanomaterials derived from V_(4)AlC_(3) as excellent catalyst for MgH_(2)

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Journal of Magnesium and Alloys 2023年第10期11卷 3790-3799页

作者： Zhiqiang Lan Huiren Liang Xiaobin Wen Jiayang Hu Hua Ning Liang Zeng Haizhen Liu Jun Tan Jürgen eckert Jin Guo Guangxi Novel Battery Materials Research Center of Engineering Technology Guangxi Colleges and Universities Key Laboratory of Novel Energy Materials and Related TechnologySchool of Physical Science and TechnologyGuangxi UniversityNanning 530004PR China College of mathematics and Physics Guangxi Minzu UniversityNanning 530006PR China College of Materials Science and Engineering Chongqing UniversityChongqing 400044PR China Erich Schmid Institute of Materials Science Austrian Academy of SciencesJahnstraße 12Leoben A-8700Austria Department Materials Physics Montanuniversität LeobenJahnstraße 12Leoben A-8700Austria National University of Science and Technology«MISiS» LeninskyProsp.4Moscow 119049Russia

Hydrogen is considered one of the most ideal future energy *** safe storage and convenient transportation of hydrogen are key factors for the utilization of hydrogen *** the current investigation,two-dimensional vanadium carbide(VC) was prepared by an etching method using V_(4)AlC_(3) as a precursor and then employed to enhance the hydrogen storage properties of MgH_(2).The studied results indicate that VC-doped MgH_(2) can absorb hydrogen at room temperature and release hydrogen at 170℃. Moreover,it absorbs 5.0 wt.%of H_(2) within 9.8 min at 100℃ and desorbs 5.0 wt.% of H_(2) within 3.2 min at 300℃.The dehydrogenation apparent activation energy of VC-doped MgH_(2) is 89.3 ± 2.8 kJ/mol,which is far lower than that of additive-free MgH_(2)(138.5 ± 2.4 kJ/mol),***-initio simulations showed that VC can stretch Mg-H bonds and make the Mg-H bonds easier to break,which is responsible for the decrease of dehydrogenation temperature and conducive to accelerating the diffusion rate of hydrogen atoms,thus,the hydrogen storage properties of MgH_(2) are remarkable improved through addition of VC.

关键词： MgH_2 Two-dimensional Hydrogen storage material Density functional theory

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Mechanical behavior and deformation mechanism of shape memory bulk metallic glass composites synthesized by powder metallurgy

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Journal of Materials Science & Technology 2022年第19期114卷 42-54页

作者： Tianbing He Tiwen Lu Daniel Sopu Xiaoliang Han Haizhou Lu Kornelius Nielsch Jürgen eckert Nevaf Ciftci Volker Uhlenwinkel Konrad Kosiba Sergio Scudino Leibniz IFW Dresden Institute for Complex MaterialsHelmholtzstraße 2001069 DresdenGermany Guangdong Key Laboratory for Advanced Metallic Materials Processing South China University of TechnologyGuangzhou 510640China Erich Schmid Institute of Materials Science Austrian Academy of SciencesJahnstraße 12Leoben A-8700Austria Leibniz IFW Dresden Institute for Metallic MaterialsHelmholtzstraße 2001069 DresdenGermany TU Dresden Institute of Materials Science01062 DresdenGermany TU Dresden Institute of Applied Physics01062 DresdenGermany Department Materials Physics Montanuniversität LeobenJahnstraße 12A-8700 LeobenAustria Leibniz Institute for Materials Engineering IWT 28359 BremenGermany University of Bremen Faculty of Production Engineering28359 BremenGermany

The synthesis of martensitic or shape-memory bulk metallic glass composites(BMGCs)via solidification of the glass-forming melts requires the meticulous selection of the chemical composition and the proper choice of the processing parameters in order to ensure that the glassy matrix coexists with the desired amount of austenitic ***,a relatively limited number of such systems,where austenite and glassy matrix coexist over a wide range of compositions,is ***,we study the effective-ness of powder metallurgy as an alternative to solidification for the synthesis of shape memory ***_(48)Cu_(36)Al_(8)Ag_(8)matrix composites with different volume fractions of Ni_(50.6)Ti_(49.4)are fabricated using hot pressing and their microstructure,mechanical properties and deformation mechanism are investigated employing experiments and *** results demonstrate that shape-memory BMGCs with tun-able microstructures and properties can be synthesized by hot *** phase stability of the glass and austenitic components across a wide range of compositions allows us to examine fundamental as-pects in the field of shape memory BMGCs,including the effect of the confining stress on the martensitic transformation exerted by the glassy matrix,the contribution of each phase to the plasticity and the mechanism responsible for shear band *** present method gives a virtually infinite choice among the possible combinations of glassy matrices and shape memory phases,expanding the range of accessible shape memory BMGCs to systems where the glassy and austenitic phases do not form simul-taneously using the solidification route.

关键词： Metallic glass composites Niti alloys Mechanical properties Shear bands Martensitic transformation

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Mechanical Properties,Damage and Fracture Mechanisms of Bulk Metallic Glass Materials

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Journal of Materials Science & Technology 2007年第6期23卷 I0003-I0006,747-767页

作者： Zhefeng ZHANG Fufa WU Guo HE eckert Shenyang National Laboratory for Materials Science Institute of Metal Research Chinese Academy of Sciences Shenyang 110016 China School of Materials Science and Engineering Shanghai Jiaotong University Shanghai 200030 China IFW Dresden Institute for Complex Materials P.O. Box 270116 D-01171 Dresden Germany TU Dresden Institute for Materials Science D-01062 Dresden Germany

The deformation, damage, fracture, plasticity and melting phenomenon induced by shear fracture were investigated and summarized for Zr-, Cu-, Ti- and Mg-based bulk metallic glasses （BMGs） and their composites. The shear fracture angles of these BMG materials often display obvious differences under compression and tension, and follow either the Mohr-Coulomb criterion or the unified tensile fracture criterion. The compressive plasticity of the composites is always higher than the tensile plasticity, leading to a significant inconsistency. The enhanced plasticity of BMG composites containing ductile dendrites compared to monolithic glasses strongly depends on the details of the microstructure of the composites. A deformation and damage mechanism of pseudo-plasticity, related to local cracking, is proposed to explain the inconsistency of plastic deformation under tension and compression. Besides, significant melting on the shear fracture surfaces was observed. It is suggested that melting is a common phenomenon in these materials with high strength and high elastic energy, as it is typical for BMGs and their composites failing under shear fracture. The melting mechanism can be explained by a combined effect of a significant temperature rise in the shear bands and the instantaneous release of the large amount of elastic energy stored in the material.

关键词： Bulk metallic glasses (BMGs) criterion Plastic deformation Mechanical properties Shear fracture Failure Melting phenomenon

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Enhanced mechanical performance of gradient-structured CoCrFeMnNi high-entropy alloys induced by industrial shot-blasting

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Rare Metals 2023年第3期42卷 982-993页

作者： Ming-Zhi Zhang Kun Zhang Kai-Kai Song Xiao-Yu Zou Wei-Dong Song Ke-Feng Li Li-Na Hu Ze-Qun Zhang Jürgen eckert Shenzhen Research Institute of Shandong University Shenzhen 518057China CAS Key Laboratory of Microgravity(National Microgravity Laboratory) Institute of MechanicsChinese Academy of SciencesBeijing100190China State Key Laboratory of Explosion Science and Technology Beijing Institute of TechnologyBeijing 100081China School of Mechanical Electrical and Information EngineeringShandong UniversityWeihai 264209China Guangdong Institute of Materials and Processing Guangdong Academy of SciencesGuangzhou 510650China Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials(Ministry of Education) Shandong UniversityJinan 250061China Erich Schmid Institute of Materials Science Austrian Academy of SciencesLeoben 8700Austria Department of Materials Science Montanuniversitat LeobenLeoben 8700Austria

In this study,CoCrFeMnNi high-entropy alloys(HEAs)with a surface gradient nanostructure were produced using industrial shot blasting,which improved their mechanical properties compared to the untreated *** severely plastically deformed(SPD)surface layer had a multi-scale hierarchical structure with a high density of stacking faults,deformation nanotwins,and amorphous *** depth of the SPD layer steadily increased as the shot-blasting time *** differences in the microhardness and tensile strength before and after shotblasting demonstrated the significant effect of the SPD layer on the mechanical *** microhardness of the homogenized HEA was~5 *** comparison,the maximum microhardness of the specimens after 20 min of shot blasting was~8.0 GPa at the *** yield strength also improved by 178%,and a large ductility of~36%was *** nanograin boundary,stacking fault,and twin strengthening within the gradientnanostructured surface layer caused the strength to *** tensile deformation,strain concentration began at the surface of the specimen and gradually spread to the ***,the gradient-nanostructured surface layer with improved strain hardening can prevent early necking and ensure steady plastic deformation so that high toughness is achieved.

关键词： High-entropy alloy Shot blasting Gradient structure Mechanical property Deformation mechanism

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