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Near-microscopic Grain boundary facilitates fatigue crack propagation in a polycrystalline Al–Zn–Mg–Cu alloy

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Progress in Natural Science:Materials International 2023年第1期33卷 120-125页

作者： Kai Wen Xiwu Li Baiqing Xiong Haitao Lin Qinghong Wen Yanan Li Hongwei Yan Lizhen Yan Yongan Zhang Zhihui Li Hongwei Liu State Key Laboratory of Nonferrous Metals and Processes China GRINM Group Co. LTD. GRIMAT Engineering Institute Co. LTD. General Research Institute for Nonferrous Metals Southwest Aluminum(Group) Co. Ltd.

In present study, grain characteristics with sizes within 10–30 μm were fabricated from a same Al–Zn–Mg–Cu alloy, FCP behaviors of the alloys with small grain(SG alloy), medium grain(MG alloy) and large grain(LG alloy)were investigated and related fatigue fracture morphology was analyzed. With the enhancement of stress intensity factor range(ΔK), the alloy with larger grains possessed faster FCP rate, which were successively arranged as SG alloy > MG alloy > LG alloy at initial stage while turned to LG alloy > MG alloy > SG alloy at final stage for the stable expanding region. Except for conventional characteristics of striations, tearing ridges, secondary cracks,second phases, voids and dimples, more prominent Grain boundary features appeared on fracture surface, especially for MG and LG alloy. The calculation of cyclic plastic zone(CPZ) sizes proved that Grain boundary participated and promoted FCP behavior when CPZ covered grain and Grain boundary together.

关键词： Fatigue crack propagation grain size Grain boundary Cyclic plastic zone Al–Zn–Mg–Cu alloy

In-plane Grain boundary induced defect state in hierarchical NiCo-LDH and effect on battery-type charge storage

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Nano Research 2023年第4期16卷 4908-4916页

作者： Jinjin Ban Xiaohan Wen Honghong Lei Guoqin Cao Xinhong Liu Chunyao Niu Guosheng Shao Junhua Hu School of Materials Science and Engineering Industrial Technology Research Institute of Resource and Materials of Henan ProvinceZhengzhou UniversityZhengzhou 450001China State Center for International Cooperation on Designer Low-carbon&Environmental Materials(CDLCEM) Zhengzhou University100 Kexue AvenueZhengzhou 450001China Henan Provincial Key Laboratory for Metal Fuel Battery Foguang Power Generation Equipment Co.Ltd50 Holly StreetZhengzhou 450000China International Laboratory for Quantum Functional Materials of Henan School of Physics and MicroelectronicsZhengzhou UniversityZhengzhou 450001China

Domain boundaries are regarded as the effective active sites for electrochemical energy storage materials due to defects enrichment therein.However,layered double hydroxides(LDHs)tend to grow into single crystalline nano sheets due to their unique two-dimentional(2D)lattice structure.Previously,much efforts were made on the designing hierarchical structure to provide more exposed electroactive sites as well as accelerate the mass transfer.Herein,we demonstrate a strategy to introduce low angle Grain boundary(LAGB)in the flakes of Ni/Co layered double hydroxides(NiCo-LDHs).These defect-rich nano flakes were self-assembled into hydrangea-like spheres that further constructed hollow cage structure.Both the formation of hierarchical structure and grain boundaries are interpreted with the synergistic effect of Ni2+/Co2+ratio in an“etching-growth”process.The domain boundary defect also results in the preferential formation of oxygen vacancy(Vo).Additionally,density functional theory(DFT)calculation reveals that Co substitution is a critical factor for the formation of adjacent lattice defects,which contributes to the formation of domains boundary.The fabricated battery-type Faradaic NiCo-LDH-2 electrode material exhibits significantly enhanced specific capacitance of 899 C·g^(−1)at a current density of 1 A·g^(−1).NiCo-LDH-2//AC asymmetric capacitor shows a maximum energy density of 101.1 Wh·kg^(−1)at the power density of 1.5 kW·kg^(−1).

关键词： sacrificial template Grain boundary oxygen vacancy(Vo) hierarchical structure

Transfer or blockage:Unraveling the interaction between deformation twinning and Grain boundary in tantalum under shock loading with molecular dynamics

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Journal of Materials Science & Technology 2023年第25期156卷 118-128页

作者： Z.C.Meng M.M.Yang A.H.Feng S.J.Qu F.Zhao L.Yang J.H.Yao Y.Yang Q.B.Fan H.Wang Interdisciplinary Centre for Additive Manufacturing (ICAM) School of Materials and ChemistryUniversity of Shanghai for Science and TechnologyShanghai 200093China Institute of Metal Research Chinese Academy of SciencesShenyang 110016China School of Materials Science and Engineering University of Science and Technology of ChinaShenyang 110016China School of Materials Science and Engineering Tongji UniversityShanghai 201804China Academy for Advanced Interdisciplinary Studies Southern University of Science and TechnologyShenzhen 518055China National Key Laboratory of Science and Technology on Materials Under Shock and Impact School of Materials Science and EngineeringBeijing Institute of TechnologyBeijing 100081China Beijing Institute of Technology Chongqing Innovation Center Chongqing 401135China

The interaction between{112}deformation twinning and Grain boundary in coaxial polycrystalline tantalum under shock compression was studied with molecular dynamics simulation under different grain pair misorientation angles(MA)and geometric compatibility factor(m’).Generally,in the coaxial polycrystal,the value of MA determines the occurrence of twin transfer(TT)or twin blockage(TB),i.e.,twin transfer occurs at MA≤29°with twin blockage otherwise.Under TT,the value of m’affects the selection of twin variants.,i.e.,the twin system with a larger m’is easier to active.The morphology of twin pairs is ruler-shaped and lenticular under TT and TB,respectively,with different thickening mechanisms,including Grain boundary dislocation emission.

关键词： Plasticity Grain boundary Twin Atomistic simulation Tantalum

Stabilizing nanograined Fe-Cr alloy by Si-assisted Grain boundary segregation

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Journal of Materials Science & Technology 2023年第3期134卷 223-233页

作者： X.F.Xu X.Y.Li B.Zhang Shenyang National Laboratory for Materials Science Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China School of Materials Science and Engineering University of Science and Technology of ChinaHefei 230026China

Intentional solute segregation at Grain boundary(GB)can effectively stabilize the nanograined alloys by reducing the excess energy and mobility of GB,but it usually works for binary alloys with sufficient GB segregation tendency.Here,we found that the segregation of Cr can be enhanced in a nanostruc-tured Fe-8Cr alloy with insufficient GB segregation tendency through the interaction of another solute Si(1.0 wt.%).After surface mechanical grinding treatment and subsequent annealing,the nanograined Fe-8Cr-1Si is more thermally stable than the nanograined Fe-8Cr,which is mainly attributed to the Si-enhanced Cr segregation as observed by Super-X energy-dispersive X-ray spectroscopy(EDS)mapping system.With the grain refinement to nanoscale,the thermal stability is further improved due to the in-crease of Cr content at GBs and the precipitates formed at appropriate high temperatures.The present finding provides guidance for the development of advanced nanostructured ternary alloys.

关键词： Segregation Grain boundary Fe-Cr-Si alloy Nanocrystalline Thermal stability

From protonation & Li-rich contamination to grain-boundary segregation: Evaluations of solvent-free vs. wet routes on preparing Li_(7)La_(3)Zr_(2)O_(12) solid electrolyte

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Journal of Energy Chemistry 2022年第10期31卷 223-239,I0005页

作者： Xiao Huang Yang Lu Yajun Niu Jiawen Tang Yongjian Zhou Yan Yang Bingbing Tian SZU-NUS Collaborative Innovation Center for Optoelectronic Science&Technology International Collaborative Laboratory of 2D Materials for Optoelectronics Science and Technology of Ministry of EducationInstitute of Microscale OptoelectronicsShenzhen UniversityShenzhen 518060GuangdongChina Beijing Key Laboratory of Green Chemical Reaction Engineering and Technology Department of Chemical EngineeringTsinghua UniversityBeijing 100084China Collaborative Innovation Center for Vessel Pollution Monitoring and Control Dalian Maritime UniversityDalian 116026LiaoningChina

Garnet-type Li_(7)La_(3)Zr_(2)O_(12)(LLZO) has been recognized as a candidate solid electrolyte for high-safety Lianode based solid-state batteries because of its electro-chemical stability against Li-metal and high ionic conductivity. Solvent(e.g., isopropanol(IPA)) has been commonly applied for preparing LLZO powders and ceramics. However, the deterioration of the proton-exchange between LLZO and IPA/absorbed moisture during the mixing and tailoring route has aroused less attention. In this study, a solvent-free dry milling route was developed for preparing the LLZO powders and ceramics. For orthogonal four categories of samples prepared using solvent-free and IPA-assisted routes in the mixing and tailoring processes, the critical evaluation was conducted on the crystallinity, surficial morphology, and contamination of ascalcinated and as-tailored particles, the cross-sectional microstructure of green and sintered pellets,the morphology and electro-chemical properties of grain boundaries in ceramics, as well as the interfacial resistance and performance of Li anode based symmetric batteries. The wet route introduced Li-rich contaminations(e.g., Li OH·H)_(2)O and Li)_(2)CO)_(3)) onto the surfaces of LLZO particles and Li-Ta-O segregations at the adjacent and triangular grain boundaries. The LLZO solid electrolytes prepared through dry mixing in combination with the dry tailoring route without the use of any solvent were found to the optimal performance. The fundamental material properties in the whole LLZO preparation process were found, which are of guiding significance to the development of LLZO powder and ceramic production craft.

关键词： Li_(7)La_(3)Zr_(2)O_(12) Solid electrolyte Solvent-free procedure Ion-exchange Grain boundary Fundamental material properties

Segregation of solute atoms in ZrC grain boundaries and their effects on Grain boundary strengths

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Journal of Materials Science & Technology 2022年第6期101卷 234-241页

作者： Fu-Zhi Dai Yinjie Sun Yixiao Ren Huimin Xiang Yanchun Zhou Science and Technology on Advanced Functional Composite Laboratory Aerospace Research Institute of Materials&Processing TechnologyBeijing 100076China

ZrC is a promising candidate for the application in ultra-high temperature regime due to its unique combination of excellent properties,such as high melting point,good chemical inertness and high temperature stability.The rapid decrease of strength at high temperatures,however,is one of the obstacles that impedes its practical services.Strengthening of grain boundaries by solute segregation is believed to be an effective way to improve its high temperature performance.Therefore,the segregation tendency of ten solid solute atoms,including Sc,Ti,V,Cr,Y,Nb,Mo,Hf,Ta,W,in Zr C grain boundaries,and the strengthening/weakening effects on grain boundaries due to segregation are investigated by first-principles calculations.The segregation tendency is found dominated by the size effect,which is confirmed by both a qualitative analysis and a quantitative approach based on support vector regression.It means that big atoms tend to segregate to Grain boundary sites with local expansions,while small atoms tend to segregate to Grain boundary sites with local compressions.Simulations on stress-strain responses indicate that segregation of small atoms(Ti,V,Cr,Nb,Ta,Mo,W)can usually improve Grain boundary strengths by inducing compression strains to grain boundaries,even though there is also an exception.In contrast,segregation of Sc and Y will soften grain boundaries.The results reveal that strengthening of grain boundaries by solute segregation is a valuable avenue to enhance high temperature mechanical properties of ZrC,providing guidelines for further design of ZrC based materials.

关键词： ZrC Grain boundary Segregation Strength First-principles calculation Machine learning

Fatigue crack propagation across Grain boundary of Al-Cu-Mg bicrystal based on crystal plasticity XFEM and cohesive zone model

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Journal of Materials Science & Technology 2022年第31期126卷 275-287页

作者： Qi Zhao Magd Abdel Wahab Yong Ling Zhiyi Liu School of Materials Science and Engineering Hubei University of Automotive TechnologyShiyan 442002China Faculty of Mechanical-Electrical and Computer Engineering School of Engineering and TechnologyVan Lang UniversityHo Chi Minh CityVietnam Soete Laboratory Faculty of Engineering and ArchitectureGhent UniversityTechnologiepark Zwijnaarde 903B-9052 ZwijnaardeBelgium School of Materials Science and Engineering Central South UniversityChangsha 410083China

In this paper,a methodology integrating crystal plasticity(CP),the eXtended finite element method(XFEM)and the cohesive zone model(CZM)is developed for an Al-Cu-Mg alloy to predict fatigue crack propagation(FCP)across Grain boundary(GB)of Al-Cu-Mg alloy during stageІІ.One GB model is incor-porated into FCP constitutive law to describe grain interaction at GB.A bicrystal containing GB is built up to simulate FCP behavior through L participated GBs.Modelling features including GB characteristic,cumulative plastic strain(CPS)distribution and crystal slipping evidence can be identified.The numer-ical results are compared with published experimental data to check the accuracy of model.This work demonstrates that the combination of CP containing GB constitutive laws,XFEM and CZM is a promising methodology in predicting twist angle-controlled crack deflection through GBs.

关键词： Grain boundary Twist angle Crystal plasticity Extended finite element method Fatigue crack propagation Cumulative plastic strain

Unveiling the Grain boundary-related effects on the incipient plasticity and dislocation behavior in nanocrystalline CrCoNi medium-entropy alloy

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Journal of Materials Science & Technology 2022年第32期127卷 98-107页

作者： Shuo Sun Yang Yang Chenxu Han Guixun Sun Yan Chen Hongxiang Zong Jiangjiang Hu Shuang Han Xiaozhou Liao Xiangdong Ding Jianshe Lian Key Laboratory of Automobile Materials Ministry of EducationCollege of Materials Science and EngineeringJilin UniversityChangchun 130025China State Key Laboratory for Mechanical Behavior of Materials Xi’an Jiaotong UniversityXi’an 710049China College of Mechanical Engineering Zhejiang University of TechnologyHangzhou 310014China School of Aerospace Mechanical and Mechatronic EngineeringThe University of SydneySydneyNSW 2006Australia

The incipient plasticity and dislocation behavior in a nanocrystalline(NC)CrCoNi medium-entropy alloy were systematically investigated in terms of pop-in events during instrumental nano-indentation tests.Quantitative statistical analysis and molecular dynamic simulations were performed to reveal the effects of grain boundaries(GBs)on initial stages of plastic deformation.Multiple pop-in events appeared during loading on the NC CrCoNi.The first pop-in that represents the initial yielding was identified to be controlled by dislocation nucleation,which is in sharp contrast to the continuous elastic-plastic transition mediated by GB mechanisms in NC pure metals.This can be attributed to the sluggish kinetics of the chemically complex GBs(CCGBs)in the NC CrCoNi that hinders diffusive GB activities but facilitates dislocation nucleation.Subsequent pop-ins were also found to be closely related to the extra dragging effects imposed by the CCGBs on dislocation propagation in the NC alloy.Moreover,the extremely small grain sizes and the consequent high-volume fraction of GBs in the NC alloy severely restrict the lengths of dislocation source and the radii of dislocation loop,giving rise to a higher critical stress,smaller activation volume and lower pop-in width as compared with its coarse-grained counterpart.These results provide new insights into the onset of nano-plasticity in concentrated multi-principal element alloys.

关键词： Medium-entropy alloy Nanocrystalline Nanoindentation Incipient plasticity Grain boundary

Synergistic effect of V_(2)O_(5)and Bi_(2)O_(3) on the Grain boundary structure of high-frequency NiCuZn ferrite ceramics

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Journal of Advanced Ceramics 2022年第6期11卷 912-921页

作者： Xiuyuan FAN Guohua BAI Zhenhua ZHANG Qiming CHEN Jiaying JINa Jiafeng XUa Xuefeng ZHANG Mi YAN School of Materials Science and Engineering State Key Laboratory of Silicon MaterialsKey Laboratory of Novel Materials for Information Technology of Zhejiang ProvinceZhejiang UniversityHangzhou 310027China Institute of Advanced Magnetic Materials College of Materials&Environmental EngineeringHangzhou Dianzi UniversityHangzhou 310012China

High-frequency soft magnetic ferrite ceramics are desired in miniaturized and efficient power electronics but remain extremely challenging to deploy on account of the power loss(Pcv)at megahertz frequencies.Here,we prepared NiCuZn ferrite with superior high-frequency properties by V_(2)O_(5)and Bi_(2)O_(3)synergistic doping,which proves to be a potent pathway to reduce Pcv of the ferrite at megahertz frequencies.The sample doped with 800 ppm V_(2)O_(5)and 800 ppm Bi_(2)O_(3)yielded the most optimized magnetic properties with a Pcv of 113 kW/m^(3)(10 MHz,5 mT,25℃),an initial permeability(μi)of 89,and a saturation induction(Bs)of 340 mT,which is at the forefront of the reported results.These outstanding properties are closely related to the notable Grain boundary structure,which features a new type of nano-Bi_(2)Fe_(4)O_(9)phase around ferrite grains and a Ca/Si/V/O amorphous layer.Our results indicate great strides in correlating the Grain boundary structure with multiple-ion doping and set the scene for the developing high-frequency soft magnet ferrites.

关键词： NiCuZn ferrite megahertz application Grain boundary Bi_(2)Fe_(4)O_(9) ion doping