Started in 1985 Semimonthly
ISSN 1005-0302
CN 21-1315/TG
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      28 March 2003, Volume 19 Issue 02 Previous Issue    Next Issue
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    Research Articles
    Materials Design of Microstructure in Grain Boundary and Second Phase Particles
    Yaping ZONG, Liang ZUO
    J. Mater. Sci. Technol., 2003, 19 (02): 97-101. 
    Abstract   HTML   PDF (1105KB)
    A concept of microstructure design for materials or materials microstructure engineering is proposed. The argument was suggested based on literature review and some our new research work on second phase strengthening mechanisms and mechanical property modeling of a particulate reinforced metal matrix composite. Due to development of computer technology, it is possible now for us to establish the relationship between microstructures and properties systematically and quantitatively by analytical and numerical modeling in the research scope of computerization materials. Discussions and examples on intellectual optimization of microstructure are presented on two aspects: grain boundary engineering and optimal geometry of particulate reinforcements in two-phase materials.
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    Glass-Forming Ability for Nd70-xFe20Al10Yx and Nd60-xFe30Al10Yx Alloys
    Keqiang QIU, Haifeng ZHANG, Aimin WANG, Bingzhe DING, Zhuangqi HU
    J. Mater. Sci. Technol., 2003, 19 (02): 102-106. 
    Abstract   HTML   PDF (1497KB)
    The glass-forming ability (GFA) of Nd70-xFe20Al10Yx and Nd60-xFe30Al10Yx (0≤x≤15) alloys produced by Cu mold casting was investigated. Except Y=5 at.pct, bulk amorphous Nd70-xFe20Al10Yx alloys up to 2 mm in diameter were obtained. The GFA for Nd60-xFe30Al10Yx alloys, however, was found to decrease with increase of Y due to the increasing compositional deviation from the original eutectic point of Nd60Fe30Al10 alloy. The Nd60Fe20Al10Y10 and Nd60Fe30Al10 alloy exhibit the largest GFA and can be cast into bulk amorphous cylindrical specimens of 3 mm in diameter. The melting temperature or/and the reduced crystallization temperature is closely related to the GFA of Y-containing alloys. The bulk amorphous cylinder for the Nd55Fe20Al10Y15 alloy shows a distinct glass transition temperature and a wide supercooled liquid region before crystallization. The crystallization temperature, Tg, and the supercooled liquid region, ∆Tx, are 776 K and 58 K, respectively. The GFA and thermal stability of the Nd-Fe-Al-Y alloys were discussed.
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    Density of Ni-Cr Alloy in the Mushy State
    Feng XIAO
    J. Mater. Sci. Technol., 2003, 19 (02): 107-110. 
    Abstract   HTML   PDF (670KB)
    The density of Ni-Cr alloy in the mushy state has been measured using the modified sessile drop method. The density of Ni-Cr alloy in the mushy state was found to decrease with increasing temperature and Cr concentration in alloy. The molar volume of Ni-Cr alloy in the mushy state therefore increases with increasing the Cr concentration in alloy. The ratio of the difference of density divided by the temperature difference between liquidus and solidus temperatures decreases with increasing Cr concentration. The density of the alloy increased with the precipitation of a solid phase in alloy during the solidification process. The temperature dependence of the density of alloy in the mushy state was not linear but biquadratic.
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    Research on the Relationship between Density of States and Conducting Properties of Single-walled Carbon Nanotubes
    Zhenhua ZHANG, Jingcui PENG, Xiaohua CHEN, Jianxiong WANG
    J. Mater. Sci. Technol., 2003, 19 (02): 110-112. 
    Abstract   HTML   PDF (576KB)
    The analytical expression of the electronic density of states (DOS) for single-walled carbon nanotubes (SWNTs) has been derived on the basis of graphene approximation of the energy E(k) near the Fermi level EF. The distinctive properties of the DOS, the normalized differential conductivity and the current vs bias for SWNTs are deduced and analyzed theoretically. The singularities in the DOS (or in the normalized differential conductivity) predict that the jump structure of current (or conductance)---bias of SWNTs exists. All conclusions from the theoretical analysis are in well agreement with the experimental results of SWNT's electronic structure and electronic transport. In other words, the simple theoretical model in this paper can be applied to understand a range of spectroscopic and other measurement data related to the DOS of SWNTs.
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    AFM Study on Interface of HTHP As-grown Diamond Single Crystal and Metallic Film
    Bin XU, Musen LI, Longwei YIN, Jianjun CUI, Jianhong GONG
    J. Mater. Sci. Technol., 2003, 19 (02): 113-116. 
    Abstract   HTML   PDF (1180KB)
    The study for the interface of as-grown diamond and metallic film surrounding diamond is an attractive way for understanding diamond growth mechanism at high temperature and high pressure (HTHP), because it is that through the interface carbon atom groups from the molten film are transported to growing diamond surface. It is of great interest to perform atomic force microscopy (AFM) experiment, which provides a unique technique different from that of normal optical and electron microscopy studies, to observe the interface morphology. In the present paper, we report first that the morphologies obtained by AFM on the film are similar to those of corresponding diamond surface, and they are the remaining traces after the carbon groups moving from the film to growing diamond. The fine particles and a terrace structure with homogeneous average step height are respectively found on the diamond (100) and (111) surface. Diamond growth conditions show that its growth rates and the temperature gradients in the boundary layer of the molten film at HTHP result in the differences of surface morphologies on diamond planes, being rough on (100) plane and even on the (111) plane. The diamond growth on the (100) surface at HPHT could be considered as a process of unification of these diamond fine particles or of carbon atom groups recombination on the growing diamond crystal surface. Successive growth layer steps directly suggest the layer growth mechanism of the diamond (111) plane. The sources of the layer steps might be two-dimensional nuclei and dislocations.
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    3-D Numerical Simulation of the Electromagnetic Dam of Twin Roll Casting using Edge Element Method
    Peiwei BAO, Hongshuang DI, Aiwen QIAN, Xiaoming ZHANG, Guodong WANG
    J. Mater. Sci. Technol., 2003, 19 (02): 116-119. 
    Abstract   HTML   PDF (742KB)
    The 3-dimension numerical simulation study on the electromagnetic dam used in the twin roll caster has been performed by using the edge element method. It was found that the materials and structures of the roll collars have great influence on the distribution of the magnetic flux density, eddy current density and the electromagnetic force in the molten pool. The conductive collars make the magnetic flux density decreased in the molten pool, but it also makes the magnetic force more uniformly, and the force in the low part of the molten pool where needs greater force have increased some what. The conductive collars make the EMD device more effective than the nonconductive collars.
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    Morphology, Growth Process and Symmetry of {0001} Face on Yb:YAl3(BO3)4 Crystal
    Shanrong ZHAO, Jiyang WANG, Daliang SUN, Jing LI, Xiaobo HU
    J. Mater. Sci. Technol., 2003, 19 (02): 120-122. 
    Abstract   HTML   PDF (843KB)
    The {0001} face develops on the habit of self-frequency doubling laser crystal Yb: YAl3(BO3)4 (YbYAB) only under high growth rate condition, and its morphology is rough. To study the growth mechanism of {0001} face, we have observed the growth morphology on {0001} polishing section by atomic force microscopy (AFM). A series of AFM images captured in different growth durations on the {0001} polishing section reflect the crystal growth process. It is shown that the growth morphology on the {0001} polishing section was rough with many hillocks at the first growth stage, and it can become smooth finally, although the growth morphology on the {0001} face developed naturally on YbYAB crystal habit is always rough. On the smooth {0001} surface formed at the last growth stage, there are some triangular pits. This fact is different from that of hillocks in most crystal growth morphologies. AFM can easily distinguish the pits or hillocks on the surface, but differential interfere contrast microscopy (DIC) can not do. The orientation of the triangular pits is just the opposite to the triangular {0001} faces. The chemical etching pattern is also composed of this kind of triangular pits. These growth morphology and etching pattern of the {0001} faces show 3m symmetry, but the point group of YbYAB crystal is 32. The symmetric contradiction between morphology and point group does not exist for quartz, although which has the same point group as YbYAB. From quartz {0001} surface morphology we can distinguish the right form or left form of the crystal, but from YbYAB {0001} surface morphology we can not do. The reason for the symmetric contradiction between YbYAB {0001} surface morphology and its point group is not known yet.
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    Comparative Study of Dielectric and Magnetic Properties of Selected 3D Reticulated Ceramics and Their Same Composition Ceramic Disks
    Qing GONG, Zheng FANG, Xiaoming CAO, Jinsong ZHANG
    J. Mater. Sci. Technol., 2003, 19 (02): 123-125. 
    Abstract   HTML   PDF (558KB)
    3-dimensional reticulated ceramics (3DRCs) and their same composition ceramic disks (SCCDs) were fabricated by sol-gel method, with the composition of SrO·6Fe2O3(30%), SiC(35%) and TiO2(35%), sintered at 1200℃ in N2. The dielectric and magnetic parameters of such 3DRCs and their SCCDs were measured respectively in a temperature range from room temperature to 800℃ and in a frequency range from 2.6 GHz to 18 GHz. The results showed that the dielectric and magnetic loss of 3DRCs were obviously larger than those of their SCCDs in a wide range of temperature and the whole range of measuring frequency. The increase of dielectric loss of 3DRCs was much higher than that of magnetic loss compared to their SCCDs, which was found due to the 3D net structure extrinsic characteristics.
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    Microstructural Evolution of 2.25Cr-1.6W-V-Nb Heat Resistant Steel during Creep
    Lihui ZHU, Xueming MA
    J. Mater. Sci. Technol., 2003, 19 (02): 126-128. 
    Abstract   HTML   PDF (1338KB)
    2.25Cr-1.6W-V-Nb developed in Japan, is a low alloy heat resistant steel with good comprehensive properties. Influence of long term creep at elevated temperature on the structure of 2.25Cr-1.6W-V-Nb steel was studied in this paper, and the micromechanism of creep strength degradation was elucidated, too. Both TEM observation and thermodynamic calculation reveal that during creep the transformation occurs from M7C3 and M23C6 to M6C, which can be cavity nucleation sites. Besides, creep at 600℃ also leads to the decrease of dislocation density, the coarsening and coalescence of M23C6, the nucleation of cavities and development of cracks. The strength decrease of 2.25Cr-1.6W-V-Nb steel after long term creep is related to the decrease of dislocation hardening, precipitation hardening, solution hardening, the nucleation of cavities and development of cracks.
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    Size Evolution of the Surface Short Fatigue Cracks of 1Cr18Ni9Ti Weld Metal
    Yongxiang ZHAO
    J. Mater. Sci. Technol., 2003, 19 (02): 129-132. 
    Abstract   HTML   PDF (1696KB)
    Size evolution of the surface short fatigue cracks of 1Cr18Ni9Ti weld metal was investigated. A local viewpoint is applied to be agreement with a so-called ``effectively short fatigue crack criterion". Attention was paid to the dominant effectively short fatigue crack (DESFC) initiation zone and the zones ahead of the DESFC tips. The results revealed that the evolutionary size shows a significant character of microstructural short crack (MSC) and physical short crack (PSC) stages. In the MSC stage, fatigue damage is due to mainly the initiation and irregular growth of the effectively short fatigue cracks (ESFCs). In the PSC stage, the damage is conversely due to mainly the DESFC growth and partially, the growth of the ESFCs and the coalescence of the ESFCs themselves with the DESFC. The process involves from a non-ordered/chaotic state in the initiation of MSC stage, gradually to an independently random state at the transition point between the MSC and PSC stages and then, to an ordered/history-dependent random state. Interactive effect of the collective cracks is stronger and shows an increase in the MSC stage. It reaches a maximum value at the transition point and then, tends to a decrease in the PSC stage. The DESFC acts as a result of the interactive cracks and thus, is deemed suitable to describe the behaviour of collective cracks.
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    Phenomenological Anisotropic Study of Surface Finish in Pack Rolling
    Zhufeng YUE
    J. Mater. Sci. Technol., 2003, 19 (02): 133-136. 
    Abstract   HTML   PDF (668KB)
    A phenomenological anisotropic model has been presented for the surface roughness modeling of pack rolling. The model is an assembly of grains in different orientations and sizes. The grain size is assumed to be in log-normal distribution. To model the macro anisotropic mechanical behavior of the grains induced by the slip deformation, the grains are assumed as isolated anisotropic units. The units have different mechanic behavior, and depend on the crystallographic orientations and the external loading as well as the interaction of the adjunctive grains. In the paper, the material properties of the grains are assumed as uniform distributions. The roughness of the contact surfaces depends on the distribution types and the scatters of the distributions. It is found that the initial roughness of the contact surfaces has a little influence on the surface roughness when the rolling deformation is large. The comparison between the phenomenological model and crystallographic model shows that the phenomenological model can also give out a reasonable result, while it only takes much less CPU time. The agreement between the single sheet model and the pack rolling model shows that in a certain degree the pack rolling model can be replaced by the single sheet model to decrease the CPU time.
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    Microstructure and Performance of 2Y-PSZ/TRIP Steel Composites
    Yingkui GUO, Yu ZHOU, Dongbo LI, Xiaoming DUAN, Tingquan LEI
    J. Mater. Sci. Technol., 2003, 19 (02): 137-140. 
    Abstract   HTML   PDF (1071KB)
    2Y-PSZ/TRIP steel composites have been sintered by hot-pressing method. Their microstructure and mechanical properties were investigated by means of SEM, TEM, XRD and static tension, split Hopkinson pressure bar method. The results showed that the strength and elastic modulus of 2Y-PSZ/TRIP steel composites at room temperature decreased with the increase of 2Y-PSZ content. The main reason was that the combining strength was quite weak between the grains of ZrO2. Distortion induced martensite transformation and plasticity during the dynamic loading increased the strength and distortion capability of the composites. The transformation was carried out mainly through twins formation. The shape of martensite induced by distortion was lamellate with substructures of twins. The habit plane was near {259}γ with no mid-ridge and no explosion phenomena. The interface was straight between the austenite and martensite induced by distortion. The increase of 2Y-PSZ content, on the one hand, made the composite dynamic flow stress improved. Thereby, the fracture strength was improved. On the other hand, it depressed both the distortion capability and the martensite transformation induced by distortion. This resulted in the decrease of dynamic fracture strength.
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    Mg Amorphous Zr0.9Ti0.1(Ni0.57Mn0.28V0.1Co0.05)2.1Composite for Hydrogen Storage
    Haiyan LENG, Demin CHEN, Manqi Lv, Haifeng ZHANG, Huiming CHENG, Ke YANG
    J. Mater. Sci. Technol., 2003, 19 (02): 141-144. 
    Abstract   HTML   PDF (1680KB)
    The reactive mechanical alloying (RMA) method was used to produce Mg-40~wt pct amorphous Zr0.9Ti0.1(Ni0.57Mn0.28V0.1Co0.05)2.1 composite in this study, and the absorption/desorption property of the composite was improved remarkably. The composite possessed excellent kinetic properties even at moderate temperature (393K) without activation. Owing to the formation of the embrittle MgH2, the reactive mechanical milling process reduced the particle size of Mg and made the composite phase being highly efficiently distributed, which determined the excellent hydriding properties of the composite.
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    Effect of Sn on the Color and Tarnishing of Cu-Mn-Zn Alloys
    Yuping ZHANG, Jinxu ZHANG, Jiansheng WU
    J. Mater. Sci. Technol., 2003, 19 (02): 144-146. 
    Abstract   HTML   PDF (565KB)
    parameters such as L*, a* and b* are selected to describe the surface color of alloys while the color difference (ΔE*) is used to evaluate the color stability. The results show that with the increase of Sn, the color change of Cu-Mn-Zn alloys is greatly reduced and the corrosion resistance in the synthetic sweat is improved dramatically. However, up to 4.4wt pct Sn does not change the color of Cu-Mn-Zn alloys much. XPS and AES are employed to analyze the tarnished surface. It is proved that a Sn enriched film is formed and Sn takes the form of Sn oxide. This thin and protective oxide film can prevent alloy from further tarnishing
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    Influence of Liquid Structure on Solid Transformation of CuAlNi Shape Memory Alloy
    Xuemin PAN, Xiufang BIAN, Weimin WANG, Jingyu QIN
    J. Mater. Sci. Technol., 2003, 19 (02): 147-149. 
    Abstract   HTML   PDF (581KB)
    Molten Cu-13Al and Cu-13Al-4Ni (mass fraction) alloys have been investigated using X-ray diffraction method. A distinct pre-peak has been found in the structure factors. The pre-peak increases its intensity with decreasing temperature and addition of Ni. The structural unit size corresponding to the pre-peak equals to magnitude of (111) planar distance of β phase. The appearance of a pre-peak is due to existence of clusters with $\beta$-phase-like structure in melt. Quantity and size of clusters increase with decreasing temperature but their structural unit size remains constant. Cu-13Al-4Ni shape memory alloy ribbons can be fabricated by rapid solidification technique. Order degree of martensite and temperature of the reverse martensitic transformation increase with decreasing liquid quenching temperature. β phase particles develop from incorporating and growing of the clusters during solidification, thus result in the correlation between liquid structure and solid transformation
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    Study on Mechanical Property in Steel-Aluminum Solid to Liquid Bonding
    Lizhong ZHANG, Peng ZHANG, Yunhui DU, Daben ZENG, Jianzhong CUI, Limin BA
    J. Mater. Sci. Technol., 2003, 19 (02): 149-151. 
    Abstract   HTML   PDF (653KB)
    The bonding of solid steel plate to liquid Al was conducted using rapid solidification. The influence of thickness of Fe-Al compound layer at the interface on interfacial shear strength of bonding plate was studied. The results show that the relationship between thickness of Fe-Al compound layer and interfacial shear strength is S=30.4+8.51 h-0.51 h2+0.007 h3 (where h is thickness of Fe-Al compound layer, S is interfacial shear strength). When thickness of Fe-Al compound layer is 10.7 μm, the largest interfacial shear strength is 71.6 MPa.
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    Effects of Melt Thermal Treatment on A356 Alloy
    Jun WANG, Shuxian HE, Baode SUN, Yaohe ZHOU
    J. Mater. Sci. Technol., 2003, 19 (02): 152-154. 
    Abstract   HTML   PDF (818KB)
    To increase the casting quality of hypoeutectic Al-Si alloys, the effects of melt thermal treatment on the solidification structure of the A356 alloy were analyzed by a factorial experiment, in which the overheated melt was mixed with the low temperature melt. Experimental results show that the elongation ratio and strength of the treated samples increase remarkably compared with the control sample. The primary dendrite size reduces dramatically and the dendrite changes from columnar to equiaxed, with a little change of the secondary dendrite arm spacing (SDAS). Combined with the measurement of the nucleation undercooling, it is concluded that the solidification structure and refining effect are dependent primarily on the low temperature melt. The refining mechanism is believed as a result of the multiplication of the nuclei in the melt thermal treatment procedure
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    Surface Modification of α-Fe Metal Particles by Chemical Surface Coating
    Qixiang WANG, Baozhen SONG, Hongzhong LI
    J. Mater. Sci. Technol., 2003, 19 (02): 155-157. 
    Abstract   HTML   PDF (633KB)
    The structure of α-Fe metal magnetic recording particles coated with silane coupling agents have been studied by TEM, FT-IR, EXAFS, Mossbauer. The results show that a close, uniform, firm and ultra thin layer, which is beneficial to the magnetic and chemical stability, has been formed by the cross-linked chemical bond Si-O-Si. And the organic molecule has chemically bonded to the particle surface, which has greatly affected the surface Fe atom electronic structure. Furthermore, the covalent bond between metal particle surface and organic molecule has obvious effect on the near edge structure of the surface Fe atoms
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    XPS Analysis of the Cerium Conversion Coating on the Anodized Al6061/SiCp
    Xingwen YU, Chuanwei YAN, Chunan CAO, Guoqiang LI
    J. Mater. Sci. Technol., 2003, 19 (02): 157-160. 
    Abstract   HTML   PDF (654KB)
    A method of concentration analysis based on X-ray photoelectron spectroscopy (XPS) results was introduced. The concentration of Ce-rich conversion coating on the anodized Al based metal matrix composites Al6061/SiCp was then studied according to this method. The results revealed that the Ce conversion coating on the anodized Al6061/SiCp consisted of Al oxide, Ce oxide and Ce hydroxide. The state of Ce element exhibited the mixture of Ce3+ and Ce4+. Some of CeIII was oxidized to be CeIV in the outer layer coating.
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    Synthesis and Deposition of TiC-Fe Coatings by Oxygen-acetylene Flame Spraying
    Zhiwen LI, Changsong LIU, Jihua HUANG, Sheng YIN
    J. Mater. Sci. Technol., 2003, 19 (02): 161-163. 
    Abstract   HTML   PDF (989KB)
    A simpler and more convenient method for producing wear-resistant, TiC-reinforced coatings were investigated in this study. It consists of the simultaneous synthesis and deposition of TiC-Fe materials by oxyacetylene flame spraying. Solid reagents bound together to form a single particle are injected into the flame stream where an in-situ reaction occurs. The reaction products are propelled onto a substrate to form a coating. Microstructural analyses reveal that TiC and Fe are the dominant phases in the coatings. The reaction between Ti and C happens step by step along with the reactive spray powder flight, and TiC-Fe materials were mainly synthesized where the spray distance is 125-170 mm. The TiC-Fe coatings are composed of alternate TiC-rich and TiC-poor lamellae with different microhardness of 11.9-13.7 and 3.0-6.0GPa, respectively. Submicron and round TiC particles are dispersed within a ductile metal matrix. The peculiar microstructure is thought to be responsible for its good wear resistance, which is better nearly five times than WC-reinforced cermet coatings obtained by traditional oxyacetylene flame spray.
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    Defects and Electron Densities in TiAl-based Alloys Containing Mn and Cu Studied by Positron Annihilation
    Wen DENG, Dingkang XIONG, Jingyang WANG, Liangyue XIONG, Mingzhou CAO, Chiwei LUNG
    J. Mater. Sci. Technol., 2003, 19 (02): 164-166. 
    Abstract   HTML   PDF (658KB)
    The defects and electron densities in Ti50Al50, Ti50Al48Mn2 and Ti50Al48Cu2 alloys have been studied by positron lifetime measurements. The results show that the free electron density in the bulk of binary TiAl alloy is lower than that of pure Ti or Al metal. The open volume of defects on the grain boundaries of binary TiAl alloy is larger than that of a monovacancy of Al metal. The additions of Mn and Cu into Ti-rich TiAl alloy will increase the free electron densities in the bulk and the grain boundary simultaneously, since one Mn atom or Cu atom which occupies the Al atom site provides more free electrons participating metallic bonds than those provided by an Al atom. It is also found the free electron density in the grain boundary of Ti50Al48Cu2 is higher than that of Ti50Al48Mn2 alloy, while the free electron density in the bulk of Ti50Al48Cu2 is lower than that of Ti50Al48Mn2 alloy. The behaviors of Mn and Cu atoms in TiAl alloy have been discussed.
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    High Temperature Tensile Properties of 30 vol. Pct ZrCp/W Composite
    Yujin WANG, Yu ZHOU, Guiming SONG, Tingquan LEI
    J. Mater. Sci. Technol., 2003, 19 (02): 167-170. 
    Abstract   HTML   PDF (1622KB)
    In order to improve the high temperature strength of tungsten, 30~vol. pct ZrC particles were added to the tungsten matrix to form a 30ZrCp/W composite. The tensile properties from 20℃ to 1880℃ of the composite were examined. It was shown that with increasing testing temperature, the nonlinearity of the stress strain curve of 30ZrCp/W composite becames obvious over 1200℃ and the Young’s modulus decreases and the elongation increases. The ultimate tensile strength increases at first and then decreases with increasing testing temperature. The maximum strength of 431 MPa was obtained at 1000℃. The strengthening mechanism at high temperatures is the load transfer to ZrC particles and dislocation strengthening of the tungsten matrix with an effect of grain boundary strengthening.
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    Study on Laser Transformation Hardening of HT250 by High Speed Axis Flow CO2 Laser
    Yunxia YE, Yonghong FU, Yongkang ZHANG
    J. Mater. Sci. Technol., 2003, 19 (02): 170-173. 
    Abstract   HTML   PDF (1053KB)
    In this article, laser transformation hardening of HT250 material by high speed axis flow CO2 laser was investigated for first time in China. Appropriate laser hardening parameters, such as laser energy power P(W), laser scanning rate V m/min), were optimized through a number of experiments. The effect of the mentioned parameters on the hardened zone, including its case depth, microhardness distributions etc ., were analyzed. Through the factual experiments, it is proved that axial flow CO2 laser, which commonly outputs low mode laser beam, can also treat materials as long as the treating parameters used are rational. During the experiments, the surface qualities of some specimens treated by some parameters were found to be enhanced, which does not coincide with the former results. Furthermore in the article, the abnormal phenomenon observed in the experiments is discussed. According to the experimental results, the relationship between laser power density q and scanning rate V is shown in a curve and the corresponding formulation, which have been proved to be valuable for choosing the parameters of laser transformation hardening by axial flow CO2 lasers, was also given.
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    Finding of Gray Points on the Surface of the Sn-Fe Alloy Layer and Its Effects on the Corrosion Resistance of the Alloy Layer
    Ning LI, Jiugui HUANG, Deri ZHOU, Deyu LI
    J. Mater. Sci. Technol., 2003, 19 (02): 174-176. 
    Abstract   HTML   PDF (1571KB)
    After removing tin coating of tinplates offered by some steel works, we discovered massive, highly disperse gray points outspreading along rolling direction on the surface of the alloy layer. Morphology of the alloy layer was observed by scanning electron microscope (SEM), and many cavities of the alloy layer were found out in the gray point. After analyzing the composition of the alloy layer, we found that content of Fe in the gray points was more than that in the normal alloy layer. Moreover, corrosion resistance of the alloy layer declines with increase of amount of gray points. In addition, the hot-humidity testing was carried out for some plates whose surface has many gray points. After 14 days, there were many rust points occurring in the edge of gray points and in the small gray points. The morphology of rust points was observed by atomic force microscope (AFM). The reason why rust points generated in the edge of gray points and in the small gray points was discussed.
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    Simulation on Grain Boundary Sliding during Superplastic Deformation Using Molecular Dynamics Method
    Jitai NIU, Lihong HAN, Chonghao WOO
    J. Mater. Sci. Technol., 2003, 19 (02): 177-179. 
    Abstract   HTML   PDF (558KB)
    Grain growth and grain boundary sliding are the two main superplastic deformation mechanisms. In the paper, simulation work is focused on the sliding of a Σ13 (111) symmetric twist coincidence grain boundary, a Σ13 (110) asymmetric tilt coincidence grain boundary, and a Σ3 (110) symmetric tilt coincidence grain boundary in Al, and the energies of grain boundary for each of equilibrium configurations are computed. An embedded atom method (EAM) potential was used to simulate the atomic interactions in a bicrystal containing more than 2000 atoms. At 0 K, the relationships between total potential energy and time steps for 3 (111) symmetric twist coincidence grain boundary and Σ3(110) symmetric tilt coincidence grain boundary during sliding at 2 m/s represent the periodic characteristic. However, the relationship between total potential energy and time steps for Σ13 (110) asymmetric tilt coincidence grain boundary represents the damp surge characteristic. It is found that grain boundary sliding for Σ3 (110) symmetric tilt coincidence grain boundary is coupled with apparent grain boundary migration.
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    Superelasticity of TiPdNi Alloys with and without Rare Earth Ce Addition
    Qingchao TIAN, Jiansheng WU, Yifeng CHENG
    J. Mater. Sci. Technol., 2003, 19 (02): 179-182. 
    Abstract   HTML   PDF (832KB)
    Ti50.6Pd30Ni19.4 and Ti51Pd28Ni21(Ce) alloys have been prepared under various temperatures for long time annealing. Differential scanning calorimetery (DSC), X-ray diffraction (XRD) and tensile test were employed to investigate the phase transformation behavior and superelasticity of the alloys. It has been found that the phase transformation temperature of Ti50.6Pd30Ni19.4 is about 40℃ higher than that of Ti51Pd28Ni21(Ce), and do not change much with different annealed temperature. Obvious superelasticity is retained in Ti50.6Pd30Ni19.4 alloy annealed at 400℃ for 18 h, and annealing at higher temperature shows a deterioration of this property. The Ce addition in Ti51Pd28Ni21(Ce) alloy significantly delays recrystallization, increases yied strength and elastic modulus, but the superelasticity is poor.
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    Research on Deformation, Texture and Properties of IF Steel in Multiple Rolling Technology
    Jinxia LI, Xianghua LIU, Guodong WANG
    J. Mater. Sci. Technol., 2003, 19 (02): 183-184. 
    Abstract   HTML   PDF (365KB)
    The relationships among the deformation, texture and deep drawing properties of IF steel were investigated. By adopting double cold rolling (DCR) technology, the deep drawing property has been developed evidently. With the aid of orientation distribution function (ODF) analysis, it was found that the main reason for good property is the counterbalance in intensity of the ideal texture component {111}<011> and {111}<112>.
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    Precipitation Behavior of TiN in Bearing Steel
    Deguang ZHOU, Jie FU, Xichun CHEN, Jing LI
    J. Mater. Sci. Technol., 2003, 19 (02): 184-186. 
    Abstract   HTML   PDF (729KB)
    The precipitation behavior of titanium nitride (TiN) in bearing steel and effects of TiN inclusions on quality of the steel have been studied by thermodynamic calculation and experiment. The results show that with the increase of the content of Ti and [N], the properties of bearing steel decreased; adjusting the content of N and Ti could influence the precipitation occasion and condition of TiN in the steels. If Ti content is less than 30×10-6 and nitrogen content is less than 53×10-6, the temperature of TiN precipitation is under the solidus temperature and the size is small so that they have little harmful and even beneficial effect on the properties owing to grain refinement.
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    A Simple Method for Grain Refinement of Pure Aluminium
    Dae-Heon Joo, Jeong-Keun Lee, Myung-Ho Kim
    J. Mater. Sci. Technol., 2003, 19 (02): 187-188. 
    Abstract   HTML   PDF (570KB)
    In order to produce the fully equiaxed and fine grained pure Al, a simple casting process that used cooling slope was examined and compared with conventional casting process under same casting conditions. By using cooling slope, grains over the whole section of castings were suddenly refined and ability of grain refinement kept up at very high mold temperature up to 550℃ in examined casting conditions.
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    X-Ray and Neutron Diffraction Studies on Thermal Parameters of Thalous Bromide
    J.Bashir, R.T.A.Khan, T.Ikeda, Kenichi Ohshima
    J. Mater. Sci. Technol., 2003, 19 (02): 189-190. 
    Abstract   HTML   PDF (392KB)
    Thermal parameters of TlBr were determined using both X-ray and neutron diffraction techniques. The data was analysed by Rietveld profile refinement procedure. From the neutron diffraction data, due to weak odd-order reflections, it was not possible to determine the individual thermal parameters. The X-ray diffraction measurements yielded B Tl=0.296(5) nm2 and BBr=0.162(5) nm2. The overall isotropic value, B was 0.252(7) nm2 which is in good agreement with B=0.230(8) nm2 obtained from present neutron diffraction measurements. The present values are also in good agreement with theoretical estimates obtained from the shell models.
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    Recovery of Titanium from the Rich Titanium Slag by H2SO4 Method
    Zhenqi HUANG, Minghua WANG, Xinghong DU, Zhitong SUI
    J. Mater. Sci. Technol., 2003, 19 (02): 191-192. 
    Abstract   HTML   PDF (298KB)
    The blast furnace slag bearing TiO2 in Panzhihua, China, is an important resource to be utilized. In the present paper, the effects of the ratio of slag to H2SO4, the reaction temperature, the particle size of the slag, and the concentration of H2SO4 on the reaction rate and the acidolysis ratio of Ti were studied. The results indicated that the maximum acidolysis ratio reached 98%, which can serve as an experimental basis for the production of titania from the slag.
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