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Kinetics of glass Transition and Crystallization in Carbon Nanotube Reinforced Mg-Cu-Gd Bulk metallic glass

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Journal of Rare Earths 2006年第3期24卷 327-331页

作者：王银春王育人魏炳忱李维火孙玉峰 Institute of Mechanics Chinese Academy of Sciences Beijing 100080 China Research Center for Materials Department of Materials Science and Engineering Zhengzhou University Zhengzhou 450002 China

Mg65Cu25Gd10 bulk metallic glass and its carbon nanotube reinforced composite were prepared. Differential scanning calorimeter （DSC） was used to investigate the kinetics of glass transition and crystallization processes. The influence of CNTs addition to the glass matrix on the glass transition and crystallization kinetics was studied. It is shown that the kinetic effect on glass transition and crystallization are preserved for both the monothetic glass and its glass composite. Adding CNTs in to the glass matrix reduces the influence of the heating rate on the crystallization process. In addition, the CNTs increase the energetic barrier for the glass transition. This results in the decrease of GFA. The mechanism of the GFA decrease was also discussed.

关键词： metallic glass carbon nanotube glass transition crystallization kinetic effect composite glass Gadolinium rare earths

Structural origin for composition-dependent nearest atomic distance in Cu–Zr metallic glass

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Chinese Physics B 2023年第11期32卷 545-549页

作者：张驰刘华山彭海龙 School of Materials Science and Engineering Central South UniversityChangsha 410083China

We systematically investigate the structures of Cu–Zr metallic glass(MG) by varying the Cu concentration in classic molecular-dynamics simulation. From the pair distribution functions(PDFs), it is found that the nearest atomic distance between Zr atom and Zr atom increases significantly after adding Cu, which is related to the composition-dependent coordination behavior between Cu atom and Zr atom in the nearest neighbors. The portion of PDF related to the nearest connection is decomposed into the contributions from quadrilateral structure, pentagonal structure, hexagonal structure,and heptagonal bipyramid structure. Although the population of denser structures, i.e. 5-, 6-, and 7-number sharing ones,increases with Cu addition increasing, the connection distances between the central atoms in all these bipyramids increase for Zr–Zr pairs, leading to the expansion of Zr–Zr nearest atomic distance. These results unveil the effect of the interplay between chemical interaction and geometric packing on the atomic-level structure in Cu–Zr metallic glasses.

关键词： metallic glass structure molecular dynamics

High entropy state of orientationally-disordered clusters in Zr-based bulk metallic glass

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Progress in Natural Science:Materials International 2010年第1期20卷 87-96页

作者： Akira TAKEUCHI Makoto OGATA Akihisa INOUE World Premier International Research Center Tohoku University 2-1-1KatahiraAoba-kuSendai 980-8577Japan Graduate School of Engineering Tohoku University AramakiAoba-kuSendai 980-9482Japan Current affiliation:Materials Research Laboratory Hitachi Ltd. 1-1Omika-cho 7-chomeHitachi-shi319-1292Japan

A phase transformation of a metastable Zr2Ni intermetallic crystalline phase to vitrify was studied with molecular dynamics(MD)simulations based on a plastic crystal model(PCM),which utilizes the orientational disorder of molecules of plastic crystals in a class of soft *** simulation results showed that computational operations in MD-PCM for the random rotations of the clusters in the crystalline phase around their center of gravity and subsequent annealing lead to form a dense random packing structure from the metastable Zr2Ni *** randomly-rotated clusters provide high degrees of freedom in terms of atomic positions,which results in enhancing the glass-forming ability of the *** critical fraction of the number of rotated clusters for forming the glassy phase(fc~R)is evaluated to be ***,the critical fraction of the number of un-rotated clusters(fc~U=1-fc~R) is close to the critical concentration of site percolation for metallic *** mechanism of the metastable Zr2Ni phase to vitrify with increasing f~R was analyzed with a concept of communal entropy in the free volume theory with solid-and liquid-like cells proposed by Cohen and *** MD-PCM for the metastable Zr2Ni phase suggests that Zr-based bulk metallic glass(BMG)can be regarded as an alloy in a high rotation entropy state of clusters and that glass transition takes place by percolation of the nuclei of a liquid-like glassy phase.

关键词： metallic glass molecular dynamics simulation plastic crystal percolation communal entropy

Oxidation induced ductility enhancement of Zr based metallic glass ribbons in vicinity of glass transition temperature

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China Foundry 2022年第1期19卷 75-80页

作者： Jin-tao Wang Xue-feng Gao Rui-chun Wang Yin-xiao Wang Fu-yu Dong Wen-ying Xue Hong-wang Yang School of Materials Science and Engineering Shenyang University of TechnologyShenyang 110870China School of Intelligent Manufacturing Weifang University of Science&TechnologyShouguang 262700ShandongChina State Key Lab of Rolling&Automation Northeastern UniversityShenyang 110819China

Zr-based metallic glasses(MGs)possess a wide supercooled liquid region,which gives a wide processing window for superplastic forming to make microdevices with demanding size accuracy and surface *** existence of oxygen may have an influence on the thermoplastic deformation ***,the effect of oxidation on the mechanical behavior of the MGs in the vicinity of glass transition temperature is of great significance for practical forming of MG *** the present study,the effect of oxidation on tensile properties of Zr50Cu40Al10 metallic glass was *** tested samples were characterized by XRD and SEM *** the samples tested in air,the strength decreases 187 MPa,61 MPa and 59 MPa and the ductility increases 0.31,0.36,and 0.77 at 420℃,430℃,and 440℃,respectively,compared with those tested in flowing ***_(2) preferentially formed during the tensile testing at 420℃,and both ZrO_(2) and Al_(2)O_(3) oxides formed at 430℃.The dilution of Zr elements in the remaining amorphous matrix caused by preferential oxidation on the surface layer attributes to the decrease in strength and enhancement in ductility of the Zr_(50)Cu_(40)Al_(10) metallic glasses.

关键词： metallic glass mechanical properties tensile test preferential oxidation high temperature

Synthesis of metallic glasses and metallic glass based composites in the Cu-Mo-Hf system by ion beam mixing

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Science China(Technological Sciences) 2012年第5期55卷 1353-1358页

作者： BAI Xue WANG TongLe CUI YuanYuan DING Ning LI JiaHao LIU BaiXin Advanced Materials Laboratory Department of Materials Science and EngineeringTsinghua UniversityBeijing 100084China

Single-phase and dual-phase metallic glasses as well as metallic glass based composites were synthesized in the Cu-Mo-Hf ternary metal system by 200 keV xenon ion beam mixing of far-from-equilibrium. It was found that Mo-Hf-based and Cu-Mo-based single-phase metallic glasses could be obtained at compositions around CulTMo20Hf63 and Cu34Mo57Hf9, respectively. Interestingly, at the nearly equal-atomic stoichiometry of Cu38Mo31Hf3i, a dual-phase Cu-Mo-Hf metallic glass, consisting both of the Mo-Hf-based and Cu-Mo-based phases, was first obtained at relatively low irradiation doses ranging from （1-5）×10^15 Xe＋/cm2, and a single-phase metallic glass was eventually obtained at a dose of 7×10^15 Xe＋/cm2. In addition, two glass-based composites were obtained at the compositions of Cu14Mo62Hf24 and Cu77Mo14Hf9, and they consisted of the Mo-Hf based and Cu-Mo based metallic glasses, dissolved with some uniformly distributed BCC Mo-based and FCC Cu-based crystalline solid solutions, respectively. The formation mechanism of the above described non-equilibrium alloy phases was also discussed in terms of the atomic collision theory.

关键词： Cu-Mo-Hf system ion beam mixing metallic glass dual-phase metallic glass glass-based composite

How does the initial free volume distribution affect shear band formation in metallic glass?

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Science China(Physics,Mechanics & Astronomy) 2011年第8期54卷 1488-1494页

作者： CHEN Yan JIANG MinQiang DAI LanHong State Key Laboratory of Nonlinear Mechanics Institute of Mechanics Chinese Academy of Sciences Beijing 100190 China State Key Laboratory of Explosion Science and Technology Beijing Institute of Technology Beijing 100081 China

Introducing heterogeneities into the structure is an effective way to enhance the plasticity in metallic glasses (MGs). As natural heterogeneity, the original randomly distributed free volume in MGs has been found to be in favor of plasticity. However, the exact correlation between the free volume distribution and mechanical response is still unclear. In this paper, we investigate the shear banding in MGs with different structural disorders, characterized by both the free volume concentration (FVC) and the free volume dispersion (FVD). It is found that, either high FVC or wide FVD leads to low activation stress of shear band; wide FVD promotes the multiplication of shear bands but high FVC restricts it. It reveals that the yield strength in MGs is dependent on the amount of free volume while the plasticity mainly relies on the distribution. An optimum combination of the two aspects probably helps to design a MG of both good plasticity and high strength.

关键词： metallic glass free volume shear band yield strength

Unveiling the early stage evolution of local atomic structures in the crystallization process of a metallic glass

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Chinese Physics B 2024年第3期33卷 58-64页

作者：马琳杨晓东杨锋周鑫嘉武振伟 Institute of Nonequilibrium Systems School of Systems ScienceBeijing Normal UniversityBeijing 100875China

The early stage evolution of local atomic structures in a multicomponent metallic glass during its crystallization process has been investigated via molecular dynamics *** is found that the initial thermal stability and earliest stage evolution of the local atomic clusters show no strong correlation with their initial short-range orders,and this leads to an observation of a novel symmetry convergence phenomenon,which can be understood as an atomic structure manifestation of the ***,in our system we have quantitatively proved that the crucial factor for the thermal stability against crystallization exhibited by the metallic glass is not the total amount of icosahedral clusters,but the degree of global connectivity among them.

关键词： metallic glass crystallization molecular dynamics simulation local atomic clusters

Low-frequency Internal Friction Behaviour of Zr55Al10Ni5Cu30 metallic glass with Different Quenching Temperatures

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Journal of Wuhan University of Technology(Materials Science) 2017年第6期32卷 1476-1480页

作者：王知鸷 WANG Dong JIANG Peng WU Wangping LI Xiaoyan ZU Fangqiu SHUI Jiapeng School of Mechanical Engineering Changzhou UniversityChangzhou 213016 China School of Materials Science and Engineering Hefei University of Technology Hefei 230009 China Key Laboratory of Materials Physics Institute of Solid State Physics Chinese Academy of Science Hefei 230031 China

The correlation between the internal friction behaviour of Zr55 Al10 Ni5 Cu30 BMG samples and their quenching temperatures was investigated. It was found that, below the glass transition temperature, the activation energy decreased with increasing quenching temperature, but in the surpercooled liquid region the activation energy tended to be enhanced with a further increase in the quenching temperature. Besides, there were both anelastic and viscoelastic relaxation for the amorphous alloys. The anelastic behaviour would change into viscoelastic relaxation easily for the samples prepared at higher temperature.

关键词： internal friction quenching temperature metallic glass

Investigation of the microcrack evolution in a Ti-based bulk metallic glass matrix composite

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Progress in Natural Science:Materials International 2014年第2期24卷 121-127页

作者： Yongsheng Wang Zhenxi Guo Rui Ma Guojian Hao Yong Zhang Junpin Lin Manling Sui State Key Laboratory for Advanced Metals and Materials University of Science and Technology Beijing Institute of Microstructure and Property of Advanced Materials Beijing University of Technology

The initiation and evolution behavior of the shear-bands and microcracks in a Ti-based metallic-glass–matrix composite(MGMC) were investigated by using an in-situ tensile test under transmission electron microscopy(TEM). It was found that the plastic deformation of the Ti-based MGMC related with the generation of the plastic deformation zone in crystalline and shear deformation zone in glass phase near the crack tip. The dendrites can suppress the propagation of the shear band effectively. Before the rapid propagation of cracks, the extending of plastic deformation zone and shear deformation zone ahead of crack tip is the main pattern in the composite.

关键词： metallic glass Composites Transmission electron microscopy Ti alloys Mechanical properties