ZHAO Lihua
,
WU Lijun
,
HUANG Qizhong
,
YANG Qiaoqin 1)(Material Research and Test Center
,
Hunan University
,
Changsha
,
China)2)(Powder Metallurgy Research Institute
,
Center-South University of Technology
,
Changsha
,
China)3)(Laboratory of Atomic Imaging of Solids
,
Institute of Metal Research
,
Chinese Academy of Science
,
Shenyang
,
China)Manuscript received 18 April 1995
金属学报(英文版)
C-B4C-SiC composites with silicon additive obtained by the hot press sintering method are studied by means of transmission electron microscopy(TEM).When the specimens are heated to 1800℃,their structure does not change.When the specimens are heated to 2000℃,carbon begins to graphitize. Moreover,two monoclinic phases are observed.One monoclinic phase named as the M phase belongs to C-center monoclinic lattice with a=0.90nm,b=0.59nm,c=0.54nm and β=119.3°.The other monoclinic phase named as the Ml phase also belongs to C-center monoclinic lattice but with a=0.85nm,b=0.49nm,c=0.53nm and β=123.6°.
关键词:
:C-B_4C-SiC composite
,
null
WANG Haifeng
,
ZHANG Chunxia
,
QI Yuanhong
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
Acta Materialia
The microstructures of bulk Zr(2)Al(3)C(4) and Zr(3)Al(3)C(5) ceramics have been investigated using transmission electron microscopy and scanning transmission electron microscopy. These two carbides were determined to have a point group 6/mmm and a space group P6(3)/mmc using selected-area electron diffraction and convergent beam electron diffraction. The atomic-scale microstructures of Zr(2)Al(3)C(4) and Zr(3)Al(3)C(5) were investigated through high-resolution imaging and Z-contrast imaging. Furthermore, intergrowth between Zr(2)Al(3)C(4) and Zr(3)Al(3)C(5) was identified. Stacking faults in Zr(3)Al(3)C(5) were found to result from the insertion of an additional Zr-C layer. Cubic ZrC was occasionally identified to be incorporated in elongated Zr3Al3C5 grains. In addition, Al may induce a twinned ZrC structure and lead to the formation of ternary zirconium aluminum carbides. (c) 2006 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
关键词:
TEM;carbides;layered structures;STEM;transmission electron-microscope;mechanical-properties;crystal-structure;ternary-systems;behavior;ti3sic2;al;carbide;ti2alc;phases
Modelling and Simulation in Materials Science and Engineering
The dynamical shear deformation-induced HCP -> FCC process in Ti(3)Al was systematically investigated using both molecular dynamics ( MD) and ab initio methods. The details of the dislocation initiation, the microstructure evolution and the velocity field effect were presented and discussed. The MD simulation reveals that, with the increment of the velocity field, the deformation-induced dislocation slide may happen by three modes based on the nucleation of an initial FCC core, i.e. the continued fault slipping may initiate every other three layers, every other one and then three layers and every other one atomic layer. The corresponding transformed structure is an alternate existence of the single FCC and HCP plate, 18R fault, and the FCC plate containing three ABC units or more. The mechanism was further explored based on ab initio calculations of the detailed energy variation at different fault transition modes. The results promote systematic understanding of the stress induced fault transition mechanism in experimental observations.
关键词:
tial based alloys;phase-transformation;1st-principles;dislocation;interfaces
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
Journal of Non-Crystalline Solids
The formation of Fe-SiC composite, nanocrystalline solids through ball milling is reported. The effects of mechanical deformation, crystallite size and gaseous elements on the solid state reaction between Fe and SiC are also investigated. The formation of Fe3C after a long milling time is attributed to the kinetics of the reaction between nanocrystalline Fe and SiC.
关键词:
J.L. Huang
,
X.G. Cao
,
E. Sukedai
,
S. Yamasaki
,
and H.C.Gu(Department of Materials Engineering
,
Luoyang Institute of Technology
,
Luoyang 471039
,
China)(Department of Mechanical Engineering
,
Okayama University of Science
,
1-1 Ridai-Cho
,
Okayama City
,
Okayma 700
,
Japan)(Institute of Materials Science and Engineering
,
Xi'an Jiaotong University
,
Xi'an 710049
,
China)
金属学报(英文版)
The direct observations of the atomic arrangements in both conventional furnace annealed and electric pulse rapid annealed Fe78B13Si9 amorphous alloy have been conducted by the lattice imaging technique in a higt resolution electron microscope. The results showed that the embrittlement of the alloy was related to the extent of atomic rearrangements during the annealing processes. The embrittlement of the alloy after 1hour conventional furnace annealing at about 270℃ is caused by the sufficient atomic rearrangements which are characterized by the growth of some bct Fe3B-like atomic short range ordering regions already existed in the as-quenched structure. Electric pulse rapid annealing can effectively retard the above-mentioned atomic rearrangements and thus restrain the embrittlement. The embrittlement only occurs when certain amount of bcc α-Fe nanocrystals are precipitated in the amorphous matrix during electric pulse rapid annealing.
关键词:
Fe_(78)B_(13)Si_9 amorphous alloy
,
null
,
null
,
null
H.J. Peng
,
Y.Q. Xie
,
null
,
null
金属学报(英文版)
On the basis of the framework of systematic science of alloys (SSA), the basic information such as states, volumes, and potential energies of characteristic atoms in hcp Ti-Al system have been determined. The average atomic state of the hcp Ti3Al compound consisting of ψ and ψ atoms is 0.75[Ar] (3dn)0.573 (3dc)2.1685 (4sc)0.972 (4sf)0.3093 + 0.25[Ne] (3sc)1.32 (3pc)1.19 (3sf + 3pf)0.49. The brittleness of the ordered hcp Ti3Al compound has been discussed considering the fundamental factors, which are atomic states, bond networks, potential energy wave planes, and the ratio xTi/xAl. The existence of more pc and more dc directional electrons in the hcp Ti3Al compound lead to considerable brittleness; From bond networks and potential energy wave planes, the hcp Ti3Al compound has poorer ductility than the pure hcp Ti metal and the pure fcc Al metal; The Al-rich hcp Ti3Al ordered type alloys have poorer ductility than the Ti-rich hcp Ti3Al ordered type alloys.
关键词:
Ti3Al alloy
,
null
,
null
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
Materials Letters
The effect of atomic order on environmental embrittlement of an Fe3Al-based alloy was studied. The ordered B2 and DO3 structures are much more susceptible to the test environments (air versus vacuum) than the disordered structure. The embrittlement index, I, of B-2, DO3 and disordered structures is 62.1%, 62.5% and 21.7%, respectively. The disordered Fe-Al alloy showed the transgranular cleavage fracture mode whenever tested in vacuum or in air. A mixed intergranular/transgranular cleavage fracture mode was observed for both ordered alloys tested in vacuum. When tested in air, the B2 alloy continued to fracture via the mixed mode, while the DO3 alloy exhibited mainly transgranular cleavage fracture.
关键词:
Fe3Al-based alloy;atomic order;environmental embrittlement;room-temperature ductility;hydrogen embrittlement;feal;fracture;fe3al
