The dislocation features in FeAl alloy after superplastic deformation have been investigated by TEM. The results show that the initial large grains are divided into small grains through the formation of sub-grain boundaries during the superplastic deformation,and the sub-grain boundaries can develop into small grain boundaries by absorbing the dislocations in sub-grains. Meanwhile, the new grains can be further divided by newly formed sub-grain boundaries. After repeating the above process of evolution, the initial large grains are fined and the superplastic deformation keeps going on. Correspondent: LIN Dongliang,professor，Department of Materials Science, Shanghai Jiaotong University,Shang hai 200030

The bonding characteristics of Al3Ti and its alloys have been investigated by XPS technique. The anisotropic bonding of Al3Ti stablizes the DO22 crystal structure. In the Mn or Ni modified Al3Ti alloy appear the isotropic bonds which favour the Ll2 structure.Al(67)Ti(25)Mn8 alloy shows more spherical and weakly directional bonds than those in Al(67)Ti(25)Ni8. So the Mn-modified alloy is more ductile than the Ni modified alloy. Correspondent: HU Gengxiang, professor, Department of Materials Science, Shanghai Jiaotong University,Shanghai 200030

The effect of hydrogenation on the hot deformation behaviour of a cast Ti-25Al- 10Nb-3V- 1 Mo alloy was investigated by the isothermal hot compression test in the temperature range of 900-1000℃. The microstructural changes were examined by optical microscopy and TEM. A reduction(37%-45%) in the peak stress was observed when the alloy was charged to 0.2%H (mass fraction), which corresponds to decrease the deformation temperature by about 50℃ . Hydrogenation promotes the globularization or dynamic recrystallization of α2 phase and dynamic recovery of β phase in the alloy.Correspondent: ZHANG Yong,Beijing Box 81-4, Beijing 100095

The influences of S ranging from 15×10~(-6)to 175×100(-6)(mass fraction) on mechanical properties and microstructure have been studied. The results show that S reduced detrimentally the 650℃ stress rupture life and decreased the dutilities of the tensile and stress rupture at 650℃. Correspondent DONG Jianxin, Superalloy Division, Department of Materials Science, University of Science and Technology Beijing, Beijing 100083

The serration flow and its morphology of Al-Li single crystal were investigated under different temperatures(T) and strain rates(ε). The critical strain of serration(εc) first increased and then decreased with increasing T or decreasing ε. Temperature and strain rate have some influences on the frequency and amplitude of serration which changed irregularly with deformation. The relations between the type of the serration and the mechanisms for the occurrence of serration, and the changes of frequency and amplitude were obscure in the Al-Li single crystal. Correspondent: TIAN Baohui, Departinent of Materials, Beijing University of Aeronaulics and Astronautics,Beijing 100083

The relationships between microstructure, fracture surface and propagation behaviour of fatigue crack in TiB2 particulate reinforced ZA-8 Zn alloy and in the corresponding constitute matrix materials were studied. The present results indicate that the resistance to fatigue crack growth of the employed composite is in general superior to that of constitute matrix materials, especially for the short crack behaviour. This is attributed to (1) the interaction between particle and crack tip decreased the stress intensity ahead of the crack tip,(2) owing to the excellent interface strength,(3) the addition of reinforcement caused the change of matrix microstructure and refined the structure and (4) the bridging function of reinforcement. Finally, the mechanism for the difference in fatigue crack growth behaviour of the two materials was discussed. Correspondent HUA Wenjun, Beijing Institute of Aeronautical Materials, Beijing 100095

Studies of the fatigue crack initiation and propagation show that there is the loading frequency effect for the quenched and tempered or normalized 40Cr steel, but no the loading frequency effect for the solution treated ICr18Ni9Ti. The essential reason that causes the loading frequency effect is due to decrease in the plastic deformation propagation speed with the inereasing loading frequency. The decrease in plastic strain amplitude and the increase in residual compressive stress play a main role for the delaying fatigue crack initiation and the retarding crack propagation. The study of the loading frequency effect on the fatigue behaviour of the metals with the lower plastic deformation propagation speed possesses important engineering signification. Correspondent: FENG Zhongxin, associate professor, Institute of Metallic Materials and Strength, Xi'an Jiaotong University, Xi'an 710049

Three point bending CTOD tests have been conducted for two kinds of high strength steels with same chemical compositions but different yield ratio. Distributions of the stress and the strain in the vicinity of crack tip were also studied by three dimensional finite element analysis. It has been shown that the steel with higher yield ratio, comparing with the lower one, has the lower brittle initial CTOD δc , because of the higher stress level in the vicinity of its crack tip; but it has better ductile fracture resistance, because the micro strength heterogenity in the lower yield ratio dual-phase steel causes strain concentration. Correspondent: JING Hongyang, associated professor, Mechanical Engineering Department, Tianjin University, Tianjin 300072

The stability of the Ekman flow during ACRT (accelerated crucible rotation technique) process, and the effects of the crucible diameter Φ, the maximum variation of the rotation speed, △ωmax , as well as the liquid height H in the crucible on the Ekman flow,were studied with hydraulic analogue experiments. The result shows that, if Reynolds number Re ≤ ReC1(the low critical Re), the Ekman flow is stable, if Re≥ ReC2(the high critical Re), the Ekman flow during the crucible deceleration period is unstable, and the Ekman flow height h increases with increase of the crucible diameter Φ and the maximum variation of the rotation speed △ωmax . When Re≤ ReC1, the relation between the ratio h / R (R = 0.5Φ) and Re2 is linear. When the liquid height H< H(a critical value), the Ekman flow height h decreases with decrease in the liquid height H. Correspondent: LIU Juncheng, State Key Laboratory of Solidificatton Processing, Northwestern Polytechnical University, Xi'an 710072

The effects of the ion concentration in molten salt, agitation etc. on the chemical composition, structure and surface of alloy plating were explored. The main effect on the chemical composition of alloy plating is the metal ion concentration in the molten salt. Agitation is an important condition to obtain smooth and dense plating. Electrochemical examination and corrosion test showed that the Al-Ti and Al-Mn alloy platings have excellent corrosion resistance. Correspondent: GUO Naiming, associate professor, Institute of Chemical Metallurgy, Chinese Academy of Sciences, Beijing 100080

The foaming behaviour of CaO-SiO2-Al2O3-FeO slag system during its reduction process showed that the foaming ratio of the slag was influenced by the rate of the generated gas as well as the foaming index of the slag. The foaming index of the slag increased with decreasing the size of the bubbles inside the molten slag. With decreasing the basicity of the slag, the foaminess became more stable and the foaming life of the slag increased. The analysis of the foaming behaviour of the molten slag reveals that the height of the foaming slag is dependent on the difference between the rates of the gas generation within and discharge from the foam. Correspondent: XIAO Xingguo, professor, Department of Ferrous Metallurgy, Northeastern University,Shenyang 110006

The corrosion of 3 10SS in gas mixture of 0.4H2S / H2 / 7%CO2 at 600℃was in the form of sulfidation. The mass gain due to corrosion obeyed parabolic rate law for the initial 50 h but subsequently lower rate was observed for long time exposure up to 250 h. Such change in kinetics corresponded to structure modification of the innermost layer of chromium sulfide from its particle distribution to a continuous layer. The scale consisted of the outermost layer of FeS, the middle layer of FeCr2S4 and the innermost layer of Cr3S4. Correspondent: LI Lingchuan, Department of Materials Science and Engineering, Tsinghua University, Beijing100084

The fine-grained Ni-11 .82Al-1 .03Zr-0. 1B alloy formed Ni-rich oxide layer after preoxidized in air at 1000℃ for 15 min. This kind of preoxidation caused a severe embrittlement at 600℃ in air, and did not affect the ductility under vacuum. When the environment of preoxidation changed from air to argon atmosphere (po2 =10-1 Pa), the oxidation rate constant decreased by a factor of 103, but the oxidation rate constant for Al is expected to be independent of the externally applied oxygen partial pressure. Free energy of the formation for Al2O3 is more negative than that for NiO. The preoxidation at the argon atmosphere , by which Al-rich oxide layer formed on the large-grain specimens, retarded the embrittlement in air, but caused a ductility loss under vacuum. Correspondent: LI Tiefan, professor, Institute of Corrosion and Protection of Metals, Chinese Academy of Sciences, Shenyang 110015

The oxidation of two Fe-Nb alloys containing 15 and 30% Nb(mass fraction) has been studied at 600─800℃ under 0.1 MPa pure oxygen.The reaction followed the parabolic rate law to a reasonable approximation with rate constants much lower than that for the oxidation of pure iron under the same condition. Internal oxidation and depletion of niobium in the alloy have not been observed. The external scales were composed of Fe2O3 and a dispersion of double Fe-Nb oxide, while FeO and Fe2O3 were not observed.The oxidation behavior of these alloys is interpreted with reference to an approximate phase diagram of the ternary system Fe-Nb-O, taking into account the effects of the low solubility of niobium in the base metal and of the presence of two metallic phases in the alloy. Correspondent: NIU Yan, State Key Laboratory for Corrosion and Protection, ICPM Shenyang 110015

The structure of nanostructured NiAl(n-NiAl), synthesized by inert-gas condensation, was investigated by X-ray diffraction and TEM. The results indicated that the crystal structure of n-NiAl is same as that of conventional poly-crystalline NiAl alloy(p-NiAl); and the mean grain size of n-NiAl is 8.6 nm. However, there is severe distortion in the crystal lattice of n- NiAl(the distortion ε = 1 .2%); and the long-range ordering degree of n-NiAl is lower than that of p-NiAl. Annealing experiments showed that the grain growth almost did not occur when annealing temperature was lower than 800 K, indicating that n-NiAl is of high resistance to grain growth. In addition, by using electron-spin resonance and magnetization, the strong magnetism(ferro-or antiferromagnetism) of n-NiAl has been ovserved, and it is different from the conventional p-NiAl with weak one. The enhancement of magnetism of n-NiAl would be related to the severe distortion in the crystal lattice and the damage of long-range ordering degree of n-NiAl. Correspondent: QIN Xiaoying, associate professor, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031

The electric conductivity of sputtered ultrathin Al films as a function of thickness has been measured in situ during vacuum deposition process. At different stages of growth, the films have the different electric conductivity characteristics. Therotical analysis showed that surface scattering and grain boundary scattering played a main role in size effect of resistivity. Correspondent: TANG Zhaolin, Institute of Corrosion and Protection of Metals, Chinese Academy of Scicnces,Shenyang 110015

The solidification microstructrues and the effect of heat treatment on the eutectic carbides of M2 cast high speed steel modified with RE-B-AI-Ti compound were investigated. The solidification microstructures may be refined by modification and the eutectic carbides, mainly M2C, present discontinuous network distribution. The amount of carbide MC may be increased. Decomposition and granulation of M2C may take place after annealing at 850℃ for 3 h. Annealed further at 1000℃ for 3 h, a large quantity of eutectic carbides dissolved into the matrix. The carbides occur as the granular dispersion in traditional quenching and tempering modified steel. Thus, a great improvement of the impact toughness and the hardness and red hardness may be obtained. Correspondent: LI Yanjun, Faculty of Foundry, Jilin University of Technology, Changchun 130025

The study of Ti alloy based composite reinforced by SiC fibers showed that SiC dendrites grew along the radial directions peprendicular to the tungsten core; many stacking faults and microtwins were formed within the dendrites; SiC fibers bond well to the matrix, and the amorphous interfacial layers between them have not been damaged during composition. In the course of composition SiC dendrites near the interfacial region dissolved and diffused into the amorphous layer and reacted with the Ti alloy matrix at high temperature, producing TiC and Ti5Si3 . Correspondent. LI Douxing, professor, Institute of.Metal Research, Chinese Academy of Sciences, Shenyang 110015

The composite TiCw-AlNp/Al was prepared by a method of in situ solid-vapour-liquid state reaction under certain appropriate cooling conditions, in which the distribution and reinforcement of the TiC whiskers were discussed. The stereoscopic feature and space distribution of the TiC whiskers in the partially corroded TiCw-AlNp / Al composite matrix were observed under SEM. Correspondent: WU Renjie, professor, Institute of Composite Research, Shanghai Jiaotong University,Shanghai 200030

The magnetic properties of(Sm1-xYx)2Fe(17)Ny were studied by Mossbauer spectroscopy. The following conclusions were obtained:The uniaxial anisotropy of Sm sublattice is stronger and is the main mechanism of the total anisotropy; The preferential occupation of Y atom leads to the change of crystal structure and the influence on anisotropy is smaller. Correspondent: L UO Guangsheng, lecturer, Department of Materials, Nanchang University, Nanchang 330047

Artificial Neural Network (ANN) has been used to find the regularities of the P-C curves,plateau width and plateau pressure of ABS5-type hydrogen storage alloys. The results of computerized prediction show the usefulness of this method for the materials design of hydrogen storage alloys. Correspondent: CHEN Nianyi, Shanghai Institute of Metallurgy, Chinese Academy of Sciences, Shanghai 200050