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Solute-solute interactions and their impacts on solute co-segregation and interfacial cohesion of{1012}Twin boundary in zinc

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Journal of Materials Science & Technology 2023年第7期138卷 117-128页

作者： Zhifeng Huang Jian-Feng Nie Department of Materials Science and Engineering Monash UniversityMelbourneVIC 3800Australia

Interactions of solute atoms in biodegradable zinc alloys and their effect on alloy mechanical properties have been less investigated.In this work,the interactions between the common solutes(Li,Mg,Mn,Cu,and Ag)used in the biodegradable Zn alloys,including a solute-solute pair with the same element or with two different elements,are investigated based on first-principles calculations.It is found that the energetically favorable configuration is the third nearest-neighboring for most solute-solute pairs in the bulk lattice because of the relatively strong electronic interaction between solute and Zn atoms or the relatively small local elastic deformation associated with the configuration.Considering that interfacial cleavage is a key fracture mode of zinc,the segregation ability of these solutes and their effect on the{1012}Twin boundary cohesion are also examined.The result shows that Li tends to fully occupy its preferred site in the Twin boundary,while Mg,Mn,Cu,or Ag has a concentration limitation in the Twin boundary.The Twin boundary cohesion can be significantly enhanced by the segregation of Mn,followed by Cu and Ag,because of the contribution of their d states close to the Fermi level.Furthermore,the co-segregation ability of two solute atoms in the Twin boundary increases with increasing the binding tendency of these two solute atoms in the boundary.Mn and Li or Mg show a relatively strong co-segregation ability in the Twin boundary.Adding Mn to Zn-Li or Zn-Mg alloys can significantly enhance the resistance to fracture of twin boundaries.

关键词： Zinc alloys Twin boundary Solute-solute interaction Co-segregation Interfacial fracture

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In situ observation of the pseudoelasticity of Twin boundary

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Journal of Materials Science & Technology 2023年第35期166卷 200-207页

作者： Jingpeng Hou Keliang Qiu Fengshi Li Zhenyu Yang Yonghai Yue Yongjun Tian Zhongchang Wang Lin Guo School of Chemistry Beijing Advanced Innovation Center for Biomedical EngineeringBeihang UniversityBeijing 100191China Institute of Solid Mechanics School of Aeronautics Sciences and EngineeringBeihang UniversityBeijing 100191China Center for High Pressure Science State Key Laboratory of Metastable Materials Science and TechnologyYanshan UniversityQinhuangdao 066004China International Iberian Nanotechnology Laboratory(INL) Braga 4715-330Portugal

Twin boundary(TB)is a special and fundamental internal interface that plays a key role in altering the mechanical and physical properties of materials.However,the atomistic deformation mechanism of TB re-mains under debate,of which the most concerned aspect is how TB would affect the mechanical strength and plasticity of a material.Herein,we introduce our new discovery that the pseudoelastic strain of a TB can recover with decomposition and escape of pile-up dislocations,demonstrated by imposing a sponta-neous pseudoelastic deformation with recoverable plastic bending strain up to 5.1%on a TB.We found that the steps on the curved TB gradually annihilated during the migration of the TB,which was in-duced by the slip of decomposition dislocations on the TB.The TB not only provides local strain harden-ing through interaction with dislocations during the loading stage but also acts as a channel for the fast movement of decomposition dislocations during the recovery stage.Beside,the TB can maintain excellent pseudoelasticity under a multicycle bending test,which may play an important role in improving the fa-tigue resistance of materials.These findings could open up a new avenue for optimizing the mechanical properties of materials by manipulating their twin boundaries at the nanoscale.

关键词： Twin boundary Pseudoelasticity Migration Dislocation-Twin boundary interaction

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Structural characterization of the{1122}Twin boundary and the corresponding stress accommodation mechanisms in pure titanium

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Journal of Materials Science & Technology 2021年第13期72卷 114-121页

作者： Bingqiang Wei Song Ni Yong Liu Min Song State Key Laboratory of Powder Metallurgy Central South UniversityChangsha 410083China

{11-22}compression twin plays an important role in accommodating deformation along the c axis of HCP metals.However,the studies on the interface structure of{11-22}Twin boundary(TB),especially the twin tip,and the corresponding local stress release mechanism are still limited.This work studied the interface characters of{11-22}TB of a deformed pure titanium by transmission electron microscope.The{11-22}TB presented serrated character,consisting of coherent Twin boundary(CTB)and(0002)_(T)//(11-2-2)_(M) or(11-2-2)_(T)//(0002)_(M) steps,and the twin tip was fully composed of the basal-pyramidal(BPy)and pyramidal-basal(PyB)steps.The twin tip presents asymmetric morphology and the step height at the twin tip is much larger than that away from the twin tip.Two types of local stress accommodation mechanisms were observed:zonal dislocation emission and hexagonal close packed structure to facecentered cubic structure transformation.The zonal dislocation was produced by the dissociation of the1/3dislocation that was nucleated at the twin tip and the phase transformation was introduced by emission of Shockley partial dislocations from the{11-22}Twin boundary.

关键词： {1122} twin Twin boundary twinning dislocation Stress accommodation Titanium

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Twin boundary dominated electric field distribution in CdZnTe detectors

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Chinese Physics B 2018年第11期27卷 316-320页

作者：董江鹏介万奇余竞一郭榕榕 Christian Teichert Kevin-P Gradwohl 张滨滨罗翔祥席守智徐亚东 State Key Laboratory of Solidification Processing Northwestern Polytechnical University Xi'an 710072 China Key Laboratory of Radiation Detection Materials and Devices Northwestern Polytechnical University Xi'an 710072 China School of Optoeletronic and Communication Engineering Xiamen University of Technology Xiamen 361024 China Institute of Physics Montanuniversitaet Leoben. Leoben 8700. Austria

The performance of CdZnTe X/γ-ray detectors is strongly affected by the electric field distribution in terms of charge transport and charge collection. Factors which determine the electric field distribution are not only electric contact, but also intrinsic defects, especially grown-in twin boundaries. Here, the electric field distribution around twin boundaries is investigated in a CdZnTe bicrystal detector with a {111}–{111} twin plane using the Pockels electro-optic effect. The results of laser beam induced current pulses are also obtained by the transient current technique, and we discuss the influence of the Twin boundary on the electric field evolution. These studies reveal a significant distortion of the electric field, which is attributed to the buildup of space charges at twin boundaries. Also, the position of these space charge regions depends on the polarity of the detector bias. An energy band model based on the formation of an n–n＋–n junction across the Twin boundary has been established to explain the observed results.

关键词： electric field distribution CdZnTe Twin boundary Pockels effect

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Effect of Twin boundary on nanoimprint process of bicrystal Al thin film studied by molecular dynamics simulation

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Chinese Physics B 2015年第2期24卷 336-342页

作者：谢月红徐建刚宋海洋张云光 School of Science Xi'an University of Posts and Telecommunications College of Materials Science and Engineering Xi'an Shiyou University

The effects of a Twin boundary（TB） on the mechanical properties of two types of bicrystal Al thin films during the nanoimprint process are investigated by using molecular dynamics simulations.The results indicate that for the TB direction parallel to the imprinting direction,the yield stress reaches the maximum for the initial dislocation nucleation when the mould directly imprints to the TB,and the yield stress first decreases with the increase of the marker interval and then increases.However,for the TB direction perpendicular to the imprinting direction,the effect of the TB location to the imprinting forces is very small,and the yield stress is greater than that with the TB direction parallel to the imprinting direction.The results also demonstrate that the direction of the slip dislocations and the deformation of the thin film caused by spring-back are different due to various positions and directions of the TB.

关键词： nanoimprint molecular dynamic simulation Twin boundary

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The physical origin of observed repulsive forces between general dislocations and twin boundaries in FCC metals:An atom-continuum coupling study

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Journal of Materials Science & Technology 2022年第14期109卷 221-227页

作者： Jiayong Zhang Hongwu Zhang Qian Li Lizi Cheng Hongfei Ye Yonggang Zheng Jian Lu Department of Engineering Mechanics State Key Laboratory of Structural Analysis for Industrial EquipmentFaculty of Vehicle Engineering and MechanicsDalian University of TechnologyDalian 116024China Department of Mechanical Engineering Shenyang National Laboratory for Materials ScienceGreater Bay Joint DivisionCity University of Hong KongTat Chee AvenueKowloonHong KongChina CityU-Shenzhen Futian Research Institute Shenzhen 518045China

The combination of ultrahigh strength and excellent ductility of nanotwinned materials is rooted in the interaction between dislocations and twin boundaries(TBs).Quantifying the interaction between TBs and dislocations not only offers fresh perspectives of designing materials with high strength and ductility,but also becomes the cornerstone of multiscale modeling of materials with TBs.In this work,an atomcontinuum coupling model was adopted to quantitatively investigate the interaction between dislocations and TBs.The simulation shows that the dislocation-TB interaction is much weaker than the interaction between dislocations at the same distance.Simulation of the early stage of dislocation pileups further verifies that the experimentally observed repulsive forces are essentially from the dislocations or kink-like steps on TBs.The interaction between TBs and dislocations with different Burgers vectors was demonstrated referring to the elastic theory of dislocations.With the intrinsic interaction between dislocations and TBs being clarified,this work will promote further development of the multiscale simulation methods,such as discrete dislocation dynamics or phase-field method,of materials with TBs by providing a quantitative description of the interactions between TBs and dislocations.

关键词： Twin boundary Intrinsic interaction Repulsive force Dislocation pileup Atomistic simulation Anisotropic elasticity

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Atomic-resolution studies on reactions between basal dislocations and {1012} coherent twin boundaries in a Mg alloy

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Journal of Materials Science & Technology 2021年第7期66卷 28-35页

作者： Huhu Su Xinzhe Zhou Shijian Zheng Hengqiang Ye Zhiqing Yang Shenyang National Laboratory for Materials Science Institute of Metal ResearchChinese Academy of SciencesSchool of Materials Science and EngineeringUniversity of Science and Technology of ChinaShenyang110016China State Key Laboratory of Reliability and Intelligence of Electrical Equipment Hebei University of TechnologyTianjin300130China Jihua Laboratory Foshan528251China

Reactions between basal 〈a60〉 dislocations and {1012} coherent twin boundaries(CTBs) in a Mg alloy were studied with atomic resolution. Individual dislocation-CTB reactions produced steps with residual dislocations and multiple t winnin g dislocations(TDs) gliding away, consequently resulting in TB migration. Reactions between {1012} CTBs and low-angle grain boundaries composed of basal 〈a60〉 dislocations created either basal-prismatic/prismatic-basal interfaces or asymmetric tilt grain boundaries, depending on whether TDs gliding away or not. Not only the emission of TDs by dislocation-TB reactions may drive TB migration, but also the resultant steps or facets along TBs can act as TD sources to facilitate TB migration. Our results indicate that roughness or severe loss of local coherency induced by dislocation-TB reactions does not intrinsically impede TB migration in Mg alloys. Dislocation-TB reactions may provide another feasible strategy to improve the ductility of Mg alloys, in addition to other techniques like grain refinement and texture modification.

关键词： Mg alloys Dislocation Twin boundary Migration Plastic deformation

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In situ atomic-scale observation of dislocation behaviors in twin-structured Pt nanocrystals

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Science China(Technological Sciences) 2021年第3期64卷 599-604页

作者： GUO YiZhong SUN Tao FU LiBo HAO LongHu HUANG Ming WEI RuJian LUO JunFeng HE Xin WANG XingQuan XIONG XiaoDong WANG LiHua HAN XiaoDong Beijing Key Lab of Microstructure and Property of Advanced Materials Institute of Microstructure and Properties of Advanced MaterialsBeijing University of TechnologyBeijing 100124China Grikin Advanced Materials CO. LTD.Beijing 102200China

The deformation mechanisms of twin-structured metallic materials have attracted great interest.Though previous theoretical predictions have suggested that the repulsive force of the Twin boundary(TB)can significantly affect the deformation of twinstructured metals,it remains unclear whether this prediction applies to experimental conditions.In this paper,the atomic-scaled deformation process of twin-structured Pt nanocrystals was in situ observed using our home-made device in a high-resolution transmission electron microscope.We have shown that the plastic deformation of the twin-structured Pt nanocrystals was governed by full dislocation generation as well as Lomer dislocation(LD)lock formation and destruction.After LD locks were destructed,these full dislocations tended to move towards the surface of the nanocrystals.The findings revealed that due to the ultra-high repulsive force of TB on dislocation,there was no dislocation-TB reaction during the deformation.These findings can enrich our understanding of the dislocation behaviors of twin-structured nanocrystals.

关键词： deformation mechanism repulsive force Twin boundary dislocations in situ

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Effect of grain size on fatigue cracking at twin boundaries in a CoCrFeMnNi high-entropy alloy

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Journal of Materials Science & Technology 2020年第4期39卷 1-6页

作者： A.G.Wang X.H.An J.Gu X.G.Wang L.L.Li W.L.Li M.Song Q.Q.Duan Z.F.Zhang X.Z.Liao School of Aerospace Mechanical&Mechatronic EngineeringThe University of Sydne0ySydneyAustralia State Key Laboratory of Powder Metallurgy Central South UniversityChangsha 410083China Materials Fatigue and Fracture Division Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China Max-Planck-Institut für Eisenforschung Max-Planck-Stra?e 140237 DüsseldorfGermany

The fatigue cracking behavior at twin boundaries(TBs)in a Co Cr Fe Mn Ni high-entropy alloy with three different grain sizes was systematically investigated under low-cycle fatigue.Irrespective of grain size,the change from slip band cracking to TB cracking occurred with increasing the difference in the Schmid factors(DSF)between matrix and twin.However,the required critical DSF for the transition of the dominant cracking mode decreases with decreasing grain size due to the reduced slip band spacing that increases the impingement sites on the TBs and facilitates the coalescence of defects and voids to initiate TB cracks.

关键词： High-entropy alloy Fatigue cracking Twin boundary Slip band Grain size

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Dislocation Source and Pile-up in a twinning-induced Plasticity Steel at High-Cycle Fatigue

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Acta Metallurgica Sinica(English Letters) 2021年第2期34卷 169-173页

作者： Rendong Liu Zhiyuan Liang Li Lin Mingxin Huang Iron and Steel Research Institute Ansteel GroupAnshan 114021China Songshan Lake Materials Laboratory Dongguan 523808China Department of Mechanical Engineering The University of Hong KongHong KongChina

Dislocation behaviour of a twinning-induced plasticity(TWIP)steel subjected to high-cycle fatigue tests is investigated in the present study.Grain boundaries are the important sources of dislocation generation during fatigue tests,contributing to the increase in dislocation density.Continuous emission of dislocations from grain boundaries is observed in many grains.Inclusions can sustain large dislocation pile-ups at the inclusion interfaces,leading to a high stress concentration and therefore acting as potential sites of microcrack nucleation.In contrast,annealing twin boundaries are relatively weak boundaries for dislocation pile-ups.When the number of dislocations in a pile-up is large,dislocations can crossover twin boundaries and glide inside the annealing twins.The stress concentration at the Twin boundary is relatively low so that twin boundaries could not act as the sites for microcrack initiation.

关键词： Dislocation source Grain boundary Twin boundary Fatigue Inclusion

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