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Efficient predictions of formation energies and convex hulls from density functional tight binding calculations

Journal of materials science & Technology 2023年第10期141卷 236-244页

作者： Anshuman Kumar Zulfikhar A.Ali Bryan M.Wong Materials Science&Engineering Program University of California-RiversideRiverside92521CAUSA Department of Physics&Astronomy University of California-RiversideRiverside92521CAUSA Materials Science&Engineering Program Department of Chemical&Environmental EngineeringDepartment of Physics&Astronomyand Department of ChemistryUniversity of California-RiversideRiverside92521CAUSA

Defects in materials significantly alter their electronic and structural properties,which affect the per-formance of electronic devices,structural alloys,and functional ***,calculating all the possible defects in complex materials with conventional Density Functional Theory(DFT)can be compu-tationally *** enhance the efficiency of these calculations,we interfaced Density Functional Tight Binding(DFTB)with the Clusters Approach to Statistical Mechanics(CASM)software package for the first *** SiC and ZnO as representative examples,we show that DFTB gives accurate results and can be used as an efficient computational approach for calculating and pre-screening formation ener-gies/convex *** DFTB+CASM implementation allows for an efficient exploration(up to an order of magnitude faster than DFT)of formation energies and convex hulls,which researchers can use to probe other complex systems.

关键词： CASM DFTB DFT Formation energy Convex hull

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Corrosion behavior of single-and poly-crystalline dual-phase TiAl–Ti3Al alloy in NaCl solution

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International Journal of Minerals,Metallurgy and materials 2023年第4期30卷 689-696页

作者： Dongpeng Wang Guang Chen Anding Wang Yuxin Wang Yanxin Qiao Zhenguang Liu Zhixiang Qi Chain Tsuan Liu School of Materials Science and Engineering Jiangsu University of Science and TechnologyZhenjiang 212100China Centre for Advanced Structural Materials Department of Mechanical and Biomechanical EngineeringCity University of Hong KongHong Kong 999077China Engineering Research Center of Materials Behavior and Design Ministry of EducationNanjing University of Science and TechnologyNanjing 210094China School of Materials Science and Engineering Dongguan University of TechnologyDongguan 523808China

To clarify the correlation of single-crystalline structure with corrosion performance in high-strength TiAl alloys, electrochemical and surface characterization was performed by comparing Ti–45Al–8Nb dual-phase single crystals with their polycrystalline counterparts in NaCl solution. Polarization curves show a lower corrosion rate and a higher pitting potential of ~280 mV for the dual-phase single crystals. Electrochemical impedance spectroscopy and potentiostatic polarization plots revealed a higher impedance of the charge transfer through the compact passive film. Surface composition analysis indicated a compact film with more content of Nb, as twice as that in the film on the *** results reflect that the dual-phase Ti–45Al–8Nb single crystals possess a higher corrosion resistance in NaCl solution, compared with their polycrystalline counterpart, arising from a more homogeneous microstructure and composition distribution.

关键词： titanium alloy single crystal corrosion X-ray photoelectron spectroscopy

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Multi-scale synergic optimization strategy for dielectric energy storage ceramics

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Journal of Advanced Ceramics 2023年第4期12卷 649-680页

作者： Xuhui Fan Jing Wang Hao Yua Zehan Zheng Ji Zhang Kongjun Zhu State Key Laboratory of Mechanics and Control of Mechanical Structures College of Aerospace EngineeringNanjing University of Aeronautics and AstronauticsNanjing 210016China School of Materials Science and Engineering Nanjing University of Aeronautics and AstronauticsNanjing 210016China Department of Materials Science and Engineering Southern University of Science and TechnologyShenzhen 518055China School of Materials Science and Engineering Nanjing University of Science and TechnologyNanjing 210094China

Dielectric capacitors,serving as the indispensable components in advanced high-power energy storage devices,have attracted ever-increasing attention with the rapid development of science and *** various dielectric capacitors,ceramic capacitors with perovskite structures show unique advantages in actual application,e.g.,excellent adaptability in high-temperature *** the optimization of their energy storage performance has become a hot research topic *** review presents the basic principles of energy storage in dielectric ceramics and introduces multi-scale synergic optimization strategies according to the key factors for superior energy storage *** summarizing the common points in numerous works,several universal modification strategies are reviewed,and future research on fatigue fracture of ceramic capacitors under multi-field including but not limited to force,electric,and thermal coupling conditions is also anticipated.

关键词： dielectric capacitors high-power energy storage multi-scale

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Combined anisotropic and cyclic constitutive model for laser powder bed fusion fabricated aluminum alloy

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Chinese Journal of Aeronautics 2025年第1期38卷 165-184页

作者： Fei-Fan LI Jihong ZHU Weihong ZHANG Shifeng WEN Jingwen SONG Jun MA Gang FANG State IJR Center of Aerospace Design and Additive Manufacturing School of Mechanical EngineeringNorthwestern Polytechnical UniversityXi’an 710072China Research&Development Institute of Northwestern Polytechnical University in Shenzhen Shenzhen 518063China School of Materials Science and Engineering Northwestern Polytechnical UniversityXi'an 710072China Department of Mechanical and Industrial Engineering Norwegian University of Science and TechnologyTrondheim 7491Norway State Key Laboratory of Tribology in Advanced Equipment Department of Mechanical EngineeringTsinghua UniversityBeijing 100084China

This study presents new methods to effectively model the anisotropic yielding and hardening behavior of laser powder bed fusion fabricated aluminum alloy under both monotonic and cyclic loading *** proposed model combines the yield surface-interpolation method to accurately describe the anisotropic hardening rates in various directions,with the Chaboche kinematic hardening rule to precisely reflect the cyclic *** numerical implementation of the combined anisotropic and cyclic constitutive model,a fully implicit stress integration algorithm based on return mapping method is ***,the multiple parameters associated with the model are categorized and identified in an uncoupled *** isotropic and cyclic hardening parameters are determined by an inverse method,and the stability of the optimization outcomes is validated by applying different starting points for the ***,the back-stress effect on the identification of anisotropic parameters associated with the stress invariant-based Hill48 yield function is considered for the first *** consideration leads to an improved prediction accuracy compared to the identification of anisotropic parameters without considering back-stress *** combined anisotropic and cyclic constitutive model,along with the calibrated parameters,are proven capable of accurately reproducing the intricate deformation behavior of laser powder bed fusion fabricated AlSi10Mg.

关键词： Constitutive models Anisotropy Kinematic hardening Laser powder bed fusion Aluminum alloys

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Morphological Characterization and Tribological Properties of TiCoNi Alloy Coatings on Ti–6Al–4V Alloy via Laser Deposition

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Journal of Bio- and Tribo-Corrosion 2024年第4期10卷 1-14页

作者： Adesina, Olanrewaju Seun Farotade, Gabriel Ayokunle Obadele, Babatunde Abiodun Sanyaolu, Olufemi Oluseun Ikubanni, Peter Pelumi Sanyaolu, Modupe Eunice Adediran, Adeolu Adesoji Adeleke, Adekunle Akanni Department of Mechanical Engineering Redeemer’s University Ede Nigeria Department of Chemical Metallurgical and Materials Engineering Tshwane University of Technology P.M.B. X680 Pretoria0001 South Africa Chemical Materials & ampMetallurgical Engineering Botswana International University of Science and Technology Palapye Botswana Department of Mechanical Engineering Landmark University Omu-Aran Nigeria Department of Physical Science Redeemer’s University Ede Nigeria Department of Mechanical Engineering Nile University of Nigeria Abuja Nigeria

The goal of this work is to improve the Ti–6Al–4V alloy's hardness and tribological behavior. Coaxial laser surface cladding was used to develop intermetallic layers of nickel (Ni), cobalt (Co), and titanium (Ti). Laser power of 900 W, beam spot size of 3 mm, powder feed rate of 1.0 g/min, and gas flow rate of 1.2 L/min are the optimized parameters used for laser depositions. The laser scan speeds were adjusted between 0.6 and 1.2 m/min. Investigations were conducted into the effects of powder admixture and laser parameters on the fabricated coatings' microstructure, tribological behavior and hardness. X-ray diffractometry (XRD), energy dispersive spectroscopy (EDS) with Scanning electron microscopy (SEM) was employed for the characterization of the microstructural evolution and phase identification, respectively. Additionally, the tribological experiment was conducted via UMT-2 –CETR reciprocating tribometer, and the coatings’ micro-hardness characteristics were examined using EmcoTEST DURASCAN. The micrographs exhibit no signs of porousness, cracks, or stress introduction, according to the results. For every manufactured sample, good metallurgical adhesion was obtained. By comparing the hardness of the ternary coating (Co–Ni–10Ti deposited at a scan speed of 1.2 m/min, with a hardness of 980 HV) to the substrate (Ti–6Al–4V, with a hardness of 330 HV), a hardness increase of approximately 2.96 times was observed. Furthermore, the Co–Ni–10Ti coating, deposited at a scan speed of 1.2 m/min, demonstrated a 51.1% reduction in the coefficient of friction (COF) compared to the base alloy, indicating superior anti-wear performance. The enhanced properties are attributed to the formation of hard intermetallic compounds such as Ti–Co, Co2Ti, Al5Co2, and Ni3Ti, along with their uniform distribution and finely tuned grain sizes. © The Author(s) 2024.

关键词： Microhardness

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Simultaneous enhancement of strength and ductility via microband formation and nanotwinning in an L1_(2)-strengthened alloy

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Fundamental Research 2024年第1期4卷 147-157页

作者： Lu Yang Dingshan Liang Zhuo Cheng Ranxi Duan Chuanxin Zhong Junhua Luan Zengbao Jiao Fuzeng Ren Department of Materials Science and Engineering Southern University of Science and TechnologyShenzhen 518055China Department of Materials Science and Engineering City University of Hong KongHong Kong 999077China Department of Mechanical Engineering The Hong Kong Polytechnic UniversityHong Kong 999077China

Metallic alloys with high strength and large ductility are required for extreme structural ***,the achievement of ultrahigh strength often results in a substantially decreased ***,we report a strategy to achieve the strength-ductility synergy by tailoring the alloy composition to control the local stacking fault energy(SFE)of the face-centered-cubic(fcc)matrix in an L1_(2)-strengthened superlattice *** a proof of concept,based on the thermodynamic calculations,we developed a non-equiatomic CoCrNi_(2)(Al_(0.2)Nb_(0.2))alloy using phase separation to create a near-equiatomic low SFE disordered CoCrNi medium-entropy alloy matrix with in situ formed high-content coherent Ni_(3)(Al,Nb)-type ordered nanoprecipitates(∼12 nm).The alloy achieves a high tensile strength up to 1.6 GPa and a uniform ductility of 33%.The low SFE of the fcc matrix promotes the formation of nanotwins and parallel microbands during plastic deformation which could remarkably enhance the strain hardening *** work provides a strategy for developing ultrahigh-strength alloys with large uniform ductility.

关键词： L1_(2)-strengthened superlattice alloy Stacking fault energy Nanotwins Microbands Strain hardening

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Exceptional strength paired with increased cold cracking susceptibility in laser powder bed fusion of a Mg-RE alloy

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材料科学技术（英文版） 2025年第10期213卷 300-314页

作者： Qingchen Deng Fan Chen Lu Wang Ziyi Liu Qianye Wu Zhiyu Chang Yujuan Wu Wentao Yan Liming Peng Wenjiang Ding National Engineering Research Center of Light Alloy Net Forming and State Key Laboratory of Metal Matrix Composites School of Materials Science and EngineeringShanghai Jiao Tong UniversityShanghai 200240PR China Department of Mechanical Engineering National University of Singapore117575Singapore

Additive manufacturing(AM)of high-strength metallic alloys frequently encounters detrimental distor-tion and cracking,attributed to the accumulation of thermal *** issues significantly impede the practical application of as-printed *** study examines the Mg-15Gd-1Zn-0.4Zr(GZ151K,wt.％)alloy,a prototypical high-strength casting Mg-RE alloy,fabricated through laser powder bed fusion(LPBF).Despite achieving ultra-high strength,the GZ151K alloy concurrently exhibits a pronounced cold-cracking *** as-printed GZ151K alloy consists of almost fully fine equiaxed grains with an average grain size of merely 2.87 μ*** direct aging(T5)heat treatment induces the forma-tion of dense prismatic β'***,the LPBF-T5 GZ151K alloy manifests an ultra-high yield strength of 405 MPa,surpassing all previously reported yield strengths for Mg alloys fabricated via LPBF and even exceeding that of its extrusion-T5 ***,as-printed GZ151K samples with a build height of 2 mm exhibit no cracking,whereas samples with build heights ranging from 4 to 18 mm demonstrate severe cold *** stress simulation also suggests that the cold cracking susceptibility increases significantly with increasing build *** combination of high thermal stress and low ductility in the as-printed GZ151K alloy culminates in a high cold cracking *** study offers novel insights into the intricate issue of cold cracking in the LPBF process of high-strength Mg alloys,highlighting the critical balance between achieving high strength and mitigating cold cracking susceptibility.

关键词： Laser powder bed fusion Mg-RE alloy Cold cracking High strength Build height Thermal stress simulation

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Enhancing corrosion resistance of MAO coatings on Al alloy LY12 through in situ co-doping with zinc phosphate and cerium phosphate

Corrosion Communications

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Corrosion Communications 2025年第1期17卷 35-43页

作者： Chao Yang Tao Ying Aihui Huang Jian Huang Pinghu Chen Paul K.Chu Xiaoqin Zeng National Engineering Research Center of Light Alloy Net Forming School of Materials Science and Engineering Shanghai Jiao Tong University Shanghai Key Laboratory of Advanced High-Temperature Materials and Precision Forming School of Materials Science and Engineering Shanghai Jiao Tong University Department of Chemistry University of Munich(LMU) College of Mechanical Engineering Key Laboratory of Hunan Province of Equipment Safety Service Technology under Extreme Environment University of South China Department of Physics Department of Materials Science&Engineering and Department of Biomedical Engineering City University of Hong Kong

Corrosion of aluminum（Al） alloys during service limits many applications. Micro-arc oxidation（MAO） coatings can enhance corrosion resistance, but porous defects in the films undermine their effectiveness. Here, by mixing a phosphate electrolyte with soluble Zn and Ce salts, zinc phosphate and cerium phosphate co-doped MAO corrosion-resistant coating is prepared on Al alloy LY12. Zinc phosphate and cerium phosphate are incorporated in situ to form an amorphous encapsulated nanocrystalline structure. During long-term corrosion, Zn2+is released and deposited as corrosion products Zn（OH）2to cover weak corrosion micro-regions in the coating. Simultaneously, Ce3+released from MAO coating co-doped with zinc phosphate/cerium phosphate forms Zn（OH）2/Ce（OH）3due to the small solubility product Kspto further enhance corrosion resistance. Compared to pristine Al alloy,corrosion potential increases from -1.306 to -0.819 VSCE, and corrosion current density decreases by 4 orders of magnitude from 2.6 × 10-6to 2.5 × 10-10A·cm-2. Co-doped MAO coating significantly enhances corrosion resistance of Al alloy LY12 and shows great potential for a wide range of applications.

关键词： Aluminum alloys Micro-arc oxidation coating Corrosion resistance Zinc phosphate Cerium phosphate

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Coherent and semicoherent α/β interfaces in titanium: structure, thermodynamics, migration

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npj Computational materials 2023年第1期9卷 146-156页

作者： Siqi Wang Tongqi Wen Jian Han David J.Srolovitz Department of Materials Science and Engineering City University of Hong KongHong Kong SARChina Department of Mechanical Engineering The University of Hong KongPokfulam RoadHong Kong SARChina

Theα/βinterface is central to the microstructure and mechanical properties of titanium *** investigate the structure,thermodynamics and migration of the coherent and semicoherent Tiα/βinterfaces as a function of temperature and misfit strain via molecular dynamics(MD)simulations,thermodynamic integration and an accurate,DFT-trained Deep *** structure of an equilibrium semicoherent interface consists of an array of steps,an array of misfit dislocations,and coherent *** determines the dislocation and step(disconnection)array structure and habit *** MD simulations show the detailed interface morphology dictated by intersecting disconnection *** steps are shown to facilitateα/βinterface migration,while the misfit dislocations lead to interface drag;the drag mechanism is different depending on the direction of interface *** results are used to predict the nature ofαphase nucleation on cooling through theα-βphase transition.

关键词： semicoherent microstructure interface

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Ultra-strong and ductile precipitation-strengthened high entropy alloy with 0.5%Nb addition produced by laser additive manufacturing

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Journal of materials science & Technology 2024年第20期187卷 195-211页

作者： Wei Zhang Ali Chabok Hui Wang Jiajia Shen J.P.Oliveira Shaochuan Feng Nobert Schell Bart J.Kooi Yutao Pei Advanced Production Engineering Engineering and Technology Institute GroningenFaculty of Science and EngineeringUniversity of GroningenNijenborgh 49747 AGthe Netherlands Nanostructured Materials and Interfaces Zernike Institute for Advanced MaterialsFaculty of Science and EngineeringUniversity of GroningenNijenborgh 49747 AGthe Netherlands UNIDEMI Department of Mechanical and Industrial EngineeringNOVA School Science and TechnologyUniversidade NOVA de LisboaCaparica 2829-516Portugal CENIMAT/I3N Department of Materials ScienceNOVA School of Science and TechnologyUniversidade NOVA de Lisboa2829-516 CaparicaPortugal School of Mechanical Engineering University of Science and Technology BeijingBeijing 100083China Institute of Materials Physics Helmholtz-Zentrum HereonMax-Planck-Str.1GeesthachtD-21502Germany

Achieving a superior strength-ductility combination for fcc single-phase high entropy alloys(HEAs)is *** present work investigates the in-situ synthesis of Fe_(49.5)Mn_(30)Co_(10)Cr_(10)C_(0.5)interstitial solute-strengthened HEA containing 0.5 wt.%Nb(hereafter referred to as iHEA-Nb)using laser melt-ing deposition(LMD),aiming at simultaneously activating multiple strengthening *** effect of Nb addition on the microstructure evolution,mechanical properties,strengthening and deformation mechanisms of the as-deposited iHEA-Nb samples was comprehensively *** levels of het-erogeneity were observed in the LMD-deposited microstructure,including different grain sizes,cellular subgrain structures,various carbide precipitates,as well as elemental *** incorporation of Nb atoms with a large radius leads to lattice distortion,reduces the average grain size,and increases the types and fractions of carbides,aiding in promoting solid solution strengthening,grain boundary strengthening,and precipitation *** test results show that the Nb addition significantly increases the yield strength and ultimate tensile strength of the iHEA to 1140 and 1450 MPa,respectively,while maintaining the elongation over 30%.Deformation twins were generated in the tensile deformed samples,contributing to the occurrence of twinning-induced *** outstanding combination of strength and ductility exceeds that for most additively manufactured HEAs reported to date,demon-strating that the present in situ alloying strategy could provide significant advantages for developing and tailoring microstructures and balancing the mechanical properties of HEAs while avoiding conventional complex thermomechanical *** addition,single-crystal micropillar compression tests revealed that although the twining activity is reduced by the Nb addition to the iHEA,the micromechanical prop-erties of grains with different orientations were signi

关键词： Laser additive manufacturing High entropy alloy In situ alloying Precipitation strengthening Deformation mechanism mechanical properties

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