材料期刊网

AN HREM STUDY OF A LATERAL MICROCRACK BENEATH INDENTATION OF [001] SILICON

Y.Q. Wu , X. Y. Yang and Y.B. Xu (State Key Laboratory for Fatigue and Fracture of Materials , Institute of Metal Research , The Chinese Academy of Sciences , Shenyang 110015 , China)(Laboratory of Atomic Imaging of Solids , Institute of Metal Research , The Chinese Academy of Sciences , Shenyang 110015 , China)

金属学报(英文版)

A cross-sectional sample of indentation in [001] silicon was made and a lateral microcrack beneath the indentation was observed by high resolution electron microscope (HREM). The HREM images around the microcrack tip show an alternate distribution of the amorphous and lattice structure. The crack does not propagate by the successive debonding between certain atomic planes, meaning that before a crack completely opens, there may be a stage of amorphization, resulting from severe distortion of lattice.

关键词: amorphization , null , null , null , null

THERMAL STRUCTURAL DISORDER AND MELTING TRANSITION IN HIGH-ANGLE GRAIN-BOUNDARY: A MOLECULAR-DYNAMICS STUDY

S.J. Zhao , Y.C. Wang , J.Q. You , Q.B. Yang , L.G. Zhou and H.Q. Ye (Department of Physics , Xiangtan University , Xiangtan 411105 , China)(Laboratory of Atomic Imaging of Solids , Institute of Metal Research , The Chinese Academy of Sciences , Shenyang 110015 , China)(Department of Materials Science , Northeastern University , Shenyang 110006 , China)

金属学报(英文版)

A structural transition in the fcc ∑=5 (120)/[001] high-angle tilt grain-boundary(GB)is investigated by molecular-dynamics simulation. The calculations have been performed at various temperutures and the thermodynamic melting point Tm of the model system is determined by using a many-body potential fitted to copper. A thermal disorder transition in the GB region occurs well below the melting point. Our results indicate that such a transition is a continuous process and there is no evidence of premelting, which is entirely in accord with experiment results and theoretical prediction.Moreover we also observed that melting initiated at the interface and then propagated into the bulk quickly at or above Tm.

关键词: moleculandynamics , null , null

DEFORMATION-INDUCED α2→γ TRANSFORMATION IN A HOT DEFORMED Ti-45A1-10Nb ALLOY

J. G. Wang , L.C Zhang , G.L. Chen and H. Q. Ye(State Key Laboratory for Advanced Metals and Materials , University of Science and Technology Beijing , Beijing 100083 , China)(Laboratory of Atomic Imaging of Solids , Institute of Metal Research , The Chinese Academy of Sciences , Shenyang 110015 , China)

金属学报(英文版)

High-resolution transmission electron microscope (HRTEM) was employed to investigate the deformation-induced α2→γ phase transformation phenomenon in a hot deformed Ti-45Al-10Nb alloy. Such a tronsformation can be nucleated either at α2/γ interfaces or at stacking faults on the basal planes of the α2 phase. The growth of deformation-induced γplate is accomplished by the motion of α/6<100> Shockley partials on alternate basal planes (0001)α2, and the α/6<100> Shockley partials move in coordination rather than sweep on (0001)α2 plane one by one. It appears that no atom transportation is involved in this stress-induced α2→γ transfromation.

关键词: intermetallic compound , null , null , null , null , null

THE TYPE II DEFECT IN 18R MARTENSITE IN A Cu-Zn-Al ALLOY

J. X. Zhang , Y. F. Zheng , W. Cai and L.C.Zhao(School of Materials Science and Engineering , Harbin Institute of Technology Harbin 150001 , China)(Laboratory of Atomic Imaging of Solids , Institute of Metal Research , The Chinese Academy of Sciences , Shenyang 110015 , China)

金属学报(英文版)

Type H defect in 18R martensite in a Cu-Zn-Al alloy has been studied by high resolution electron microscopy. It was found that Type H defect is not fault internal to martensite plate; rather,it is a stack of plates A and C. The rare observation of Type H defect is considered to be due to the fact that thc slice is too thin to exist for self-accommodation.

关键词: shape memory alloy , null , null

Quantitative Analysis of Non-Crystalline and Crystalline Solids in Blast Furnace Slag

WANG Haifeng , ZHANG Chunxia , QI Yuanhong

钢铁研究学报(英文版)

China is short of water seriously. But granulation of blast furnace slag (BFS) with water has many disadvantages, such as high water consumption and difficulty in heat recycling. So developing a new dry granulation technique to treat BFS is very important. The applicability of BFS directly depends on the content of non-crystalline solids in the slag after treatment. So it is of theoretical and practical significance to analyze the content of non-crystalline solids in the slag quantitatively and simply. Metallographical test is mainly adopted to quantify the non-crystalline in BFS now with the shortages such as making sample complexly, determining difficultly and personally. For the diffraction intensity of non-crystalline is proportionate to the content of non-crystalline in BFS, X-ray diffraction method was adopted to quantify the non-crystalline and the crystalline solids in BFS. The quantificational coefficient between the crystalline and the non-crystalline solids of BFS is 0.70 whose main composition is: w（CaO）38.2%，w（SiO2）35.7%，w（Al2O3）16.3%，w（MgO）8.3%. The relatively error of using X-ray diffraction instrument to quantitative analyse non-crystalline content of BFS is less than 1%.

关键词: Blast Furnace Slag;Non-Crystalline;Crystalline;Quantificational Analysis

FRACTAL NATURE OF A FRACTURE SURFACE IN LAYERED SOLIDS

Chinese Physics Letters

We study the crack propagation in layered solids and find that when there exists an easy-fractured layer, the fractal surface becomes more rough, which is characterized by larger fractal dimensions.

关键词: dimension

Melting and superheating of crystalline solids: From bulk to nanocrystals

Progress in Materials Science

Melting of solids is a common phenomenon in nature. It is also one of the most important phase transformations in materials science and engineering. In recent years, extensive experimental and theoretical investigations in conjunction with computer simulations on melting of solids, with various geometries ranging from bulk forms to nanometer-sized clusters, have greatly enhanced our understanding of the nature of melting. This paper reviewed the up-to-date research results on this classical and cutting-edge topic. Emphasis was made on melting and superheating of nano-sized particles and thin films including thermodynamic and kinetic analyses of the size effect and the interfacial structure effect on melting processes. (C) 2007 Elsevier Ltd. All rights reserved.

关键词: isolated tin nanoparticles;embedded pb nanoparticles;kinetic stability;limit;energy ion-scattering;equation-of-state;small particles;electron-microscopy;molecular-dynamics;al(110) surface;al matrix

Synthesis of nanocrystalline materials from amorphous solids

Advanced Materials

The key to the formation of nanocrystallites from amorphous solids lies in the annealing temperature. This aspect of the preparation of nanocrystalline materials is covered, as are other attractive features of this method, for example, that it can be applied to most alloy and pure element systems, large quantities of nanocrystalline samples can be produced, and the grain size can be controlled. The properties of these materials are also described and it is concluded that more studies on 3D bulk: porosity-free, and clean samples are needed.

关键词: ultrafine grain-structure;alloys;selenium;sizes

Crystallization kinetics of amorphous solids under pressure

Physical Review B

The pressure effect on crystallization kinetics of amorphous solids was investigated by means of thermodynamic analysis. A model was developed to describe the nucleation process under pressure by considering the crystalline/amorphous (c/a) interface that plays a dominant role in the nucleation process. Applying the model to three types of crystallization process, polymorphous (a-Se), primary (Al89La6Ni5), and eutectic (Ni80P20), we found the calculated results can give reasonable explanations for the experimental observations. The calculation suggests that for a-Se and Ni80P20 amorphous alloy, the initial stage of nucleation is a volume expansion process due to the c/a interface formation, resulting in an increase in the nucleation work with an increment of pressure. Hence the crystallization temperature of the amorphous phase rises when a pressure is applied, while for the Al-La-Ni amorphous alloy, the nucleation barrier decreases at higher pressures. The coincidence between the calculation and the experimental results illustrates that the cia interface formation is the governing factor in the crystallization kinetics of the amorphous solids. [S0163-1829(99)03534-1].

关键词: activation volume;nanocrystalline state;metallic glasses;diffusion;alloy;selenium;phase;se;transformations;microstructure

DIRECT ATOMIC IMAGING OF THE FORMATION OF A 60-DEGREES DISLOCATION ON THE (111) SURFACE OF TB4O7

Philosophical Magazine Letters

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