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Journal of Materials Sciences & Technology
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1998, Vol.14 No.1
Online: 1998-01-28
Articles
 
Articles
1 M. P. Tosi(International Centre for Theoretical Physics, Strada Costiera 11, I-34014 Trieste, Italy)
Nonmetal-Metal Transition in Solutions of Metals in Molten Salts
Solutions of metals in molten salts present a rich phenomenology: localisatlon of electrons in disordered ionic media, activated electron transport increasing with metal concentration towards a nonmetal-metal (NM-M) transition, and liquid-liquid phase separation. A brief review of progress in the study of these systems is given in this article, with main focus on the NM-M transition. After recalling the known NM-M behaviour of the component elements in the case of expanded fluid alkali metals and mercury and of solid halogens under pressure, the article focuses on liquid metal-molten salt solutions and traces the different NM-M behaviours of the alkalis in their halides and of metals added to polyvalent metal halides.
1998 Vol. 14 (1): 1-8 [Abstract] ( 256 ) [HTML 1KB] [PDF 1015KB] ( 361 )
9 Hengzhi FU; Xingguo GENG; Jianguo LI and Jun ZHANG (State Key Lab. of Solidification Processing, Northwestern Polytechnical University, Xi'an 710072, China)
Sub-high Rate Directional Solidification
The main features of morphology evolution of crystal growth during near rapid directional so lidification were reviewed and the concept of effective constitutional supercooIing was proposed.On the basis of interface stability theory combined with experiments, the behaviour of transition from dendrites to fine cells was quantitatively described, and the transition from cells to plane front of absolute stability was also examined.
1998 Vol. 14 (1): 9-14 [Abstract] ( 213 ) [HTML 1KB] [PDF 3204KB] ( 232 )
15 Zhufeng YUE and Zhenzhou LU (Dept. of Applied Mechanics, Northwestern Polytechnical University, Xi'an 710072, China)
Self-consistent Constitutive Modeling of the Creep Damage Behaviour of Nickel-base Directionally Solidified Superalloys with Different Grain Orientations
A self consistent creep damage constitutive model is developed for nickel-base directionally solidified superalloys. Grain degradation and grain boundary voiding are considered. The model parameters are determined from the creep test data of single crystal and directionally solidified superalloy with a special grain orientation. The numerical analysis shows that the model creep damage behaviours of nickel-base directionally solidified superalloys with difFerent grain orientations are in good agreement with the experimental data.
1998 Vol. 14 (1): 15-19 [Abstract] ( 223 ) [HTML 1KB] [PDF 461KB] ( 294 )
20 Huaping XIONG (Dept. of Materials Science and Engineering, Jilin University of Technology, Changchun 130025, China)
Effect of Metallurgical Behaviour at the Interface between Ceramic and Interlayer on the Si_3N_4/1.25Cr-0.5Mo Steel Joint Strength
By using newly developed CuNi5~25Ti16~28 B rapldly solidifled brazing filler the joining of Si3 N4/1.25Cr-0.5Mo steel has been carried out with interlayer method. If employing the interlayer structure of steel (0.2 mm)/W (2.0 mm)/Ni(0.2 mm), the joint strength can be increased greatly compared with employing that of Ni/W/Ni, and the three point bend strength of the Joint shows the value of 261 MPa. The metallurgical behaviour at the interface between Si3N4 and the interlayer has been studied. It is found that Fe participated in the interfacial reactions between Si3N4 and the brazing filler at the Si3N4/steel (0.2 mm) interface and the compound Fe5Si3 was produced. However, since the reactions of Fe with the active Ti are weaker than those of Ni with Ti, the normal inter facial reactions were still assured at the interface of Si3N4/steel (0.2 mm) instead of Si3N4/Ni (0.2 mm), resulting in the improvement of the joint strength. The mechanism of the formation of Fe5Si3 is also discussed. Finally, some ideas to further ameliorate and simplify the interlayer structure are put forward.
1998 Vol. 14 (1): 20-24 [Abstract] ( 217 ) [HTML 1KB] [PDF 2180KB] ( 238 )
25 Weitao ZHENG; Kezhao XING; N.Hellgren; I.Ivanov; WS.Salaneck and J.-E.Sundgren (Dept. of Physics, Linkoping University, S-581 83 Linkoping, Sweden)(Present address: Dept. of Materials Science, Jilin University Changchun 130023, China)
N1s Electron Binding Energies of CN_x Thin Films Grown by Magnetron Sputtering at Different Temperature
Carbon nitride thin films deposited using dc unbalanced magnetron sputtering system have been analyzed by X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT1R) and Raman spectroscopy. The XPS data show that N1s binding states depend on substrate temperature Ts, in which the peak at 400.0 eV increases with Ts, whereas the peak at 398.3 eV decreases with Ts slightly On the basis of XPS, FT1R and Raman spectra, the assignment of N1s electron binding energies was made. The peak at 400.0 eV is attributed to N atoms bonded to sp2 coordinated C atoms. The peak at 398.3 eV is attributed to N atoms bonded to sp3 coordinated C atoms as well as N C bonds.
1998 Vol. 14 (1): 25-28 [Abstract] ( 238 ) [HTML 1KB] [PDF 369KB] ( 308 )
29 Kun ZHANG and Yuqing WANG (Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110015, China)Benlian ZHOU (International Center for Materials Physics, Shenyang 110015, China)
Biomimetic Study on Helical Fiber Composites
The innovative approach imparting strength and toughness to carbon fiber reinforced polymer composites (CFRP) is put fotward from the viewpoint of biomimetics. Helical fibers produced by twisting fiber bundle are arranged in the matrix to simulate the unique structure of natural fibers.The results on the CFRP with helical fiber bundles show that, under the same state of strong fiber/matrix interface, the impact fracture toughness can be improved substantially compared to conventional composites with plain fibers. The beneficial effect is attributed to the helical fiber bundles which act as single fibers of huge diameter effectively increasing the fIber eIastic energy.
1998 Vol. 14 (1): 29-32 [Abstract] ( 209 ) [HTML 1KB] [PDF 1152KB] ( 302 )
33 Zongyi MA; Jing BI and Yuxiong LU (Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110015, China)
Tensile Creep Behaviour of Silicon Carbide Particulate Reinforced Aluminium Composite
Tensile creep tests were carried out on 15SiC (vol.pct) particulate reinforced commercial pure aluminum (15%SiCp/Al) composite at 573 and 623 K. The steady state creep stage exists at the applied stresses under the condition of tension. The 15%SiCp/Al composite exhibits an apparent stress exponent of about 13 and an apparent activation energy of 253 kJ/mol. The creep data were normalized using a substructure invariant model with a stress exponent of 8 together with a threshold stress.
1998 Vol. 14 (1): 33-36 [Abstract] ( 212 ) [HTML 1KB] [PDF 345KB] ( 270 )
37 Yufeng ZHENG; Wei CAI; Yongqian WANG; Yichun LUO and Liancheng ZHAO (School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001, China)
Effects of Heat Treatment on the Transformation Temperature and the Microstructure of Ni-Ti-Nb Shape Memory Alloy
The effects of heat treatment on the phase transformation temperature and the microstructure of Ni-Ti-Nb alloy have been investigated by means of R-T method, TEM and EPMA. With the increase of annealing temperature, cooling rate and ageing temperature, the Ms temperature increases. TEM observations show no new precipitated phase was found in the B2 parent phase after heat treatment, but EPMA shows the content of Ni (or Ni/Ti ratio) in the B2 matrix changed. The main reason for the change of transformation temperature lies in the change of the matrix composition (or Ni/Ti ratio) with the variation of heat treatment procedure.
1998 Vol. 14 (1): 37-40 [Abstract] ( 275 ) [HTML 1KB] [PDF 1209KB] ( 407 )
41 Geping LI and Qingchun LI (Harbin Institute of Technology, Harbin 150001, China)Dong LI, Yuyin LIU Shaoxuan GUAN Qingjiang WANG, Dehai PING and Zhuangqi HU (Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110015, China)
Structure of Second Phase Particles in As-cast Ti-5Al-4Sn-2Zr-1Mo-0.25Si-1Nd Alloy
The microstructure of the Ti-5Al-4Sn-2Zr-1Mo-0.25Si-1Nd (Ti-55) alloy containing second phase particles was studied. The second phase particles are 1~15 μm in size and most of them are distributed at the grain boundaries in the form of ellipsoid with a few short needle-like and blocky phases. It consists of either dark or bright amorphous "matrix", and some small spots dispersed within the "matrix", which match SnO (orthorhombic, a=0.500 nm, b=0.572 nm, c=1.12 nin).
1998 Vol. 14 (1): 41-44 [Abstract] ( 232 ) [HTML 1KB] [PDF 2508KB] ( 209 )
45 Yixin HUA and Chunpeng LIU (Dept. of Metallurgy, Kunming University of Science and Technology, Kunming 650093, China)
Evaporation Kinetics of SnS from SnS-Cu_2S Melts
The kinetics of SnS evaporation from SnS-Cu2S melts was investigated by a unique experimental method. It is shown that the process is controlled by the mass transport of SnS in gas phase. The evaporation rate of SnS is significantly enhanced by increasing tempeature and carrier gas flow rate. The apparent activation energy for the process is found to be 204.67 kJ. The evaporation rate for the present system is much smaller than that for SnS-FeS system.
1998 Vol. 14 (1): 45-48 [Abstract] ( 262 ) [HTML 1KB] [PDF 374KB] ( 302 )
49 Yang GAO (Beijing Institute of Aeronautical Material, Beijing 100095, China)Yong LIANG and Changxu SHI (Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110015, China)
Microstructure of Laser Remelted Ni-base Alloy Coating on Stainless Steel
A 5 kW CW CO2 gas laser was used to produce NiCrBSi superalloy coatings. Powders were preplaced by plasma-spraying. The microstructure and chemical composition of the coating have been studied by SEM, XRD and HREM. The results show the coating microstructure is fine dendrites, composed of γ matrix, γ' and boride (NiB) eutectic, the lattice parameter of the γ matrix is 0.3572 nm and there is a metallurgical bonding in interface.
1998 Vol. 14 (1): 49-52 [Abstract] ( 242 ) [HTML 1KB] [PDF 2358KB] ( 332 )
53 Jie FU; Yueguang YU; Anren WANG and Boping CHEN (University of Science & Technology Beijing, Beijing 100083, China)Wenshan SUN (Inner Mongolia Metallic Materials Research Institute, Baotou 014034, China)
Inclusion Modification with Mg Treatment for 35CrNi3MoV Steel
The effects of Mg on the inclusion characteristics of 35CrNi3MoV steel have been studied. The results show that Mg treatment reduces obviously the amount of inclusion in the steel.Magnesiurn and oxygen in liquid steel form dispersed fine particles of MgO, to which other oxides or sulphides nucleated at heterogeneity and grown during solidification. In this way the inclusions are modified. The small spherical inclusions containing MgO have been observed in the Mg treated steel in contrast to the large angular inclusions with Al2O3 in the conventional steel. Especially the elongated MnS inclusion is replaced by small MgS·MgO or MgS. MnS·MgO complex inclusion. The formation of inclusions have been discussed.
1998 Vol. 14 (1): 53-56 [Abstract] ( 208 ) [HTML 1KB] [PDF 1055KB] ( 401 )
57 Xiaolong ZHU(General Research Institute for Nonferrous Metals, Beijing 100088, China)Tingquan LEI (Harbin Institute of Technology, Harbin, 150001, China)
Influence of Deformation and Heat Treatment on Seawater Corrosion of 70Cu-30Ni Alloy
After deformed and annealed, 70Cu-30Ni alloy with irrecrystallization or incomplete recrystallization mainly consisting of deformed grains displayed unstable E.(corrosion potential) and low Rp (polarization resistance) in 3.5%NaCl, and corrosion product film contained a lot of seawater species in the outer layer and denickelified in the inner layer immersed in seawater for 3 and 6 months, and intergranular corrosion occurred in the matrix. With the increase of deformation and annealing temperature, the anodic oxide film formed by polarization in artificial seawater was increasingly stable. The recrystallized alloy was stable in Ec and high in Rp and its corrosion product film formed in seawater was uniform and rich in Ni.
1998 Vol. 14 (1): 57-61 [Abstract] ( 235 ) [HTML 1KB] [PDF 2261KB] ( 290 )
62 Qingsuo LIU; Huifen PENG and Nanju GU (Hebei University of Technology, Tianjin 300132, China)
Upper Bainite Formation Mechanism in Fe-1.36Si-1.01Cr-0.88C Steel
In this paper it is discussed on the mechanism of upper bainite formation. According to the results obtained in Fe-1.36Si-1.01Cr-0.88C steel, we discovered that the primary upper bainite is formed by subunits arranging along its long axis and steps are formed by subunits growing into different size along the thickness, the macro-plane of the primary upper bainite plate is the same as the basal plane (shear plane), the formation mechanism of the primary upper bainite plate is the nucleation-growth mechanism of subunits shearing one by one along long axis, controlled by diffusion.
1998 Vol. 14 (1): 62-64 [Abstract] ( 236 ) [HTML 1KB] [PDF 2019KB] ( 301 )
65 S.F. Yoon (School of Electrical and Electronic Engineering, Nanyang Technological University, Nanyang Avenue,Singapore 639798, Rep. of Singapore)
A Comparative Study of Boron and Phosphorus Doping Effects in SiC: H Films Prepared by ECR-CVD
Hydrogenated silicon carbide films (SiC:H) were deposited using the electron cyclotron resonance chemical vapour deposition (ECR-CVD) technique from a mixture of methane, silane and hydrogen, and using diborane and phosphine as doping gases. The effects of changes in the microwave power on the deposition rate and optical bandgap were investigated, and variations in the photoand dark-conductivities and activation energy were studied in conjunction with film analysis using the Raman scattering technique. In the case of boron-doped samples, the conductivity increased rapidly to a maximum, followed by rapid reduction at high microwave power. The ratio of the photo- to dark-conductivity (σph/σd) peaked at microwave power of ~600 W. Under conditions of high microwave power, Raman scattering analysis showed evidence of the formation and increase in the silicon microcrystalline and diamond-like phases in the films, the former of which could account for the rapid increase and the latter the subsequent decrease in the conductivity.In the case of phosphorusdoped SiC:H samples, it was found that increase in the microwave power has the effect of enhancing the formation of the silicon microcrystalline phase in the films which occurred in correspondence to a rapid increase in the conductivity and reduction in the activation energy The conductivity increase stabilised in samples deposited at microwave power exceeding 500 W probably as a result of dopant saturation. Results from Raman scattering measurements also showed that phosphorus doping had the effect of enhancing the formation of the silicon microcrystals in the film whereas the presence of boron had the effect of preserving the amorphous structure.
1998 Vol. 14 (1): 65-71 [Abstract] ( 290 ) [HTML 1KB] [PDF 780KB] ( 354 )
72 S. G.Psakhie; K.P.Zolnikov and D. Yu.Saraev (Institute of Strength Physics and Materials Science, Russian Academy of Sciences, Siberian Branch,Akademicheskii pr.2/1, 634021 Tomsk, Russia)
Hot Spot in Materials with Structural Defects under High Shear Loading Rates
The response of three-dimensional sample of Al, containing vacancy complex, under shear loading was simulated. The molecular dynamics method was used and interaction between atoms was described on the base of pseudopotential theory Solitary waves were generated in the sample under mechanical loading. Their interaction with the vacancy complexes was shown to be able to initiate hot spot in that local region of the complexes. Some parameters of the hot spot as well as solitary waves were calculated. The initiation of the hot spot is accompanied with sufficient local structural relaxation.
1998 Vol. 14 (1): 72-74 [Abstract] ( 213 ) [HTML 1KB] [PDF 289KB] ( 307 )
75 Junlin YIN (Shanghai Key Lab. of Metal-Founctional Materials, Shanghai Iron and Steel Research Institute, Shanghai 200940, China)
Observation on Emitting Dislocation from Grain Boundary by TEM
The observation on emitting dislocations from grain boundaries by TEM during Cu elongation has been pefformed. It is shown that there exists the "ledge" at the grain boundaries in fcc pure Cu, which is able to emit dislocations into grain under action of stress.
1998 Vol. 14 (1): 75-76 [Abstract] ( 233 ) [HTML 1KB] [PDF 680KB] ( 314 )
77 Chunxiang CUP and Renjie WU (State Key Lab. for MMCs, Shanghai Jiaotong University, Shanghai 200030, China)Jianran YAN and Guobin LI (Hebei Polytechnic University Tianjin 300132, China)
In-situ Synthesis and Formation Mechanism of TiN-Al_2O_3/Al Composite
The synthesis of TiN and Al2O3 by in situ injection of reactive nitrogen gas into molten Al alloys has been evaluated over the temperature range from 1000 to 1600℃. It is shown that TiN and Al2O3 can be formed in melt with nitrogen and surplus oxygen (in vacuum room of the induction furnace) as the reactive gases over 1000℃. Up to 2.1 wt pct Al2O3 and 5.2 wt pct of TiN in situ phases in an Al alloy has been formed in a range of size from 0.8 to 5 μm. The formation mechanism of TiN and Al2O3 is discussed in this paper.
1998 Vol. 14 (1): 77-79 [Abstract] ( 230 ) [HTML 1KB] [PDF 1406KB] ( 225 )
80 Zhongchao FENG; Yan ZHAO; Binchun ZHANG; Yaqing WANG and Zhengang WU (Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110015, China)
Low Temperature Synthesis of Diamond Films by CVD of Combined Lasers
Diamond films have been synthesized by means of LCVD through combined effects of a XeCl ultraviolet laser and an infrared CO2 laser. A special apparatus has been developed. The conditions of synthesis and the roles played by both lasers were studied. High-purity diamond films were deposited on Si substrates at 340℃.
1998 Vol. 14 (1): 80-82 [Abstract] ( 196 ) [HTML 1KB] [PDF 2002KB] ( 258 )
83 Xinchun CHANG; Jianqiang WANG; Nanlin SHI and Zhuangqi HU (State Key Lab. of RSA, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110015, China)Yijun DU,(Manufacturing Engineering Dept., City University of Hong Kong, Kowloon, Hong Kong)
Strength Improvement of CVD SiC Fibers by Electrochemical Surface Treatment
An electrochemical sudece-treatment method has been used for modifying surface condition of large diameter CVD SiC (W core) fibers. The average tensile strength of the fibers was increased obviously from 2270.1 to 3002.9 MPa. X-ray photoelectron spectroscopy (XPS) studies on the treated fiber sudece indicate that a silicon-oxide film (primarily α-SiO2) has formed,accompanying the precipitation of amorphous carbon as the products of an anode oxidation reaction. In addition, the substantial increase of fiber strength through the electrochemical treatment may be described to the formation of oxide films and elimination of defects on the fiber surface.
1998 Vol. 14 (1): 83-85 [Abstract] ( 219 ) [HTML 1KB] [PDF 1189KB] ( 258 )
86 Yanwei MA and Xianjin WANG (Dept. of Metal Forming, University of Science and Technology Beijing, Beijing 100083, China)Zutang WANG (Tsinghua University, Beijing 100084, China)
Fabrication of Grain-oriented (Bi,Pb)_2Sr_2Ca_2Cu_3O_x Superconducting Tapes Using Magnetic Field and Vibration Technique
Highly textured (Bi,Pb)2Sr2Ca2Cu3Ox superconducting tapes have been fabricated by means of magnetic-field and vibration technique. This method is an effective way of improving the degree of grain alignment and density of oxide core in tapes after heat treatment and pressing cycles.Jc of above 20% was increased than that without treatment.
1998 Vol. 14 (1): 86-88 [Abstract] ( 209 ) [HTML 1KB] [PDF 1089KB] ( 235 )
89 Hongquan WEN; Xiemin MAO and Kuangdi XU (Institute of Materials Science and Technology, Shanghai University Shanghai 200072, China)
High Strength Conductor by Directional Solidification
The directional solidification of Cu-0.8 wt pct Cr alloy was investigated for high-strength conductors. An in-situ composite material in which the matrix is in cellular morphology and the well-distributed eutectics around the cells is formed in the directional solidification process. In such microstructure, the cellular matrix is as conductor and the coated-around eutectics as reinforcement. The formation mechanism of this microstructure is discussed from the interfacial instability. As a result, the tensile strength of the material along the solidification direction is two times more than that of the conventionally cast one, while the electrical conductivity is reduced a little by comparison with the pure Cu.
1998 Vol. 14 (1): 89-91 [Abstract] ( 207 ) [HTML 1KB] [PDF 1158KB] ( 267 )
92 Wenan HAN (Institute of Corrosion and Protection of Metals, Chinese Academy of Sciences, Shenyang 110015, China)
Approach to the Cause of Corrosion in Urea Medium
The reaction course of urea synthesis from NH3 and CO2 was discussed on the basis Of bimolecular reaction mode. It was considered probable that amino-formic acid is a vigorously corrosive intermediate product. An electrochemical corrosion mechanism of stainless steels and titanium in the urea medium was proposed.
1998 Vol. 14 (1): 92-94 [Abstract] ( 244 ) [HTML 1KB] [PDF 318KB] ( 952 )
95 Qiqing ZHANG; Yan ZHANG; Fujun WANG and Lingrong LIU (Institute of Biomaterial Engineering, Chinese Academy of Medical Science and Peking Union Medical College,P.O.Box 25 (204), Tianjin 300192, China)Chun WANG (Biomedical Polymers Research Building/CCCD R
Thermal Properties of PHB/PEG Blends
Thermal properties of PHB and PHB/PEG blends were investigated by differential scanning calorimetry (DSC) and melt index (Ml) test. DSC thermograms indicate that two components of blend are miscible. From the DSC thermogram, we can also conclude that the melting point of PHB descends with the increased content of PEG, this can improve PHB processing properties.From Ml data, we may draw the same conclusion.
1998 Vol. 14 (1): 95-96 [Abstract] ( 201 ) [HTML 1KB] [PDF 192KB] ( 629 )

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