The microstructures of martensite and austenite in steel Ni9 treated under 800℃1 h, WQ+670℃1 h, WQ+585℃1 h, WQ were investegated with TEM. Most of tempered austenite particles do not precipetate according to theoritical K-S or N-W orientation relationship (OR) with martensite martrix, but have small deviation from these two ORs. In a martensite lath packet, the different austenite variants with the above approximate ORs are pricipetalted. The lath-like tempered austenite precipetates along martensite boundaries with habit plane (335)γ'∥(341)α. Martensite twins form when austenite transformed into martensite. These twins disappear during tempering. Correspondent: WU Yukun, professor, Institute of Metal Research, Chinese Academy of Sciences, Shenyang110015

The effects of Si on the grain boundary structure and mechanical properties of hypereutectoid Mn steels austenitized at 950℃ and isothemially transformed at 560℃were studied by means of SEM and TEM. The experimental results showed that the impact toughness and elongation can be improved by Si additions. The observation of microstructure revealed that grain boundary cemetite networks can be inhibited and grain boundary ferrite formed in these hypereutectoid steels by Si addition. The formation mechanism of grain boundary ferrite has also been discussed. Correspondent: LI Chengji, Professor, Department of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083

NiAl and Ni3Al duplex alloy exhibits superplastic behavioar over a narrow temperature range from 975 to 1025℃at the strain rate of 1.52 ×10(-4) s(-1). A maximum tensile elongation of 149% was obtained at 1000℃with the strain rate sensitivity up to 0.375.The superplastic deformation of the duplex alloy can be approximately described by an empirical equation of the form: ε= Aσ2.67exp(-303000 /RT). Optical microstructure and TEM observation showed that the superplastic behavior mechanism of the investigated alloy is a process of continuous recovery and recrystallization during deformation. Correspondent. LIN Dongliang, professor, Department of Materials Science, Shanghai Jiaotong Univereity,Shanghai 200030

Directionally solidified (DS) Ni3Al alloy exhibits superplasticity under a strain rate of 2.1×10(-4) s(-1) in the temperature range from 1000 to 1050℃. The highest of strain rate m value may exceed 0.3 and a maximum elongation is 1 85%. Optical and TEM observations revealed that a dynamic recrystallization process took place and this process was then in turn resulted in superplasticity of DS Ni3Al alloy. Correspondent: LIN Dongliang, professor, Department of Materials Scicnce, Shanghai Jiaotong University,Shanghai 200030

Fatigue cracking in Ni3Al single crystals with two kinds of orientation was examined by means of single-edge notch specimens under cyclic compression. Stage I cracking along two or more {111} planes can occur from the notch root simultaneously. There exists an orientation dependence of the crack initiation threshold under cyclic compression. The cleavage chunk falling off from the specimen surface due to the intersection of different {111} planes was observed in (100)[010] specimen, but never observed in (110)[110] specimen. Subsequently, the mechanism of crack growth which is dependent on orientation was proposed in this paper. Correspondent: ZHANG Guangping, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110015

Samples of Fe3Al with (D0)3 structure after annealing at 500℃ for 5 days were studied with field-ion microscope (FIM). Although the overall FIM ring structures of the treated Fe3Al are much developed, the ring structure of <111> pole is rather confused while that of the <100> pole is very clear. By successive observation, it was found that the <100> pole has a simple field evaporation sequence, while the <111> pole possesses a rather complicated one. This indicates that the ordering of type SI occurred in the (D0)3 order transformation tends to end, but the ordering of type SII is not completed.Prolonging the annealing time to 20 days under the same temperature did not result in a better <111> pole contrast. Correspondent: ZHI Rentao, professor, Department of Materials Physics, University of Science and Technology Beijing, Beijing 100083

TEM in situ tensile tests of 310 stainless steel show that a dislocation free zone (DFZ) forms after equilibrium if the displacement keeps constant after many dislocations are emitted from a crack tip. The elastic DFZ is gradually thinned and the stress in DFZ will reach the cohesive strength resulting in nucleating of nanocracks in DFZ and blunting into voids. If continuously tensioning after crack tip emitted dislocations, and inhomogeneously thinning ahead of crack tip, then initiating and connecting of micro-voids(or micro-cracks) will be observed rather than DFZ, initiating of nanocracks and nanocracks' blunting into voids. The inversely piled-up dislocations ahead of a loaded crack tip can move towards the crack tip if unloading a little. Correspondent: LI Hongqi, Department of Materials Physics, University of Science and Technology Beijing,Beijing 100083

The fracture toughness KC and fractal dimension Df of fractured surfaces of Cu-Ni-Al single crystal have been measured at temperture range from 20℃to 120℃, in which thermoelastic martenstic transformation happened. The parent phase has higher KC than martensite phase due to stress induced transformation. The relationship between KC and Df has been studied especially and a linear relationship was found on semilog plot if failure mode is a simple mechanism. The slope of plot may be positive or negative for brittle or ductile failure respectively. The opposite relation can be understood by fracture micro-mechanism. Correspondent: LIN Guangming, professor, Department of Physics, Zhongshan University, Guangzhou 510275

The partial α(α2)/γ phase equilibria in Ti-Al-Si ternary system at low Si concentration were measured by EPMA and examined with thermodynamic analysis. The results show that the addition of Si in Ti-Al binary system results in the α(α2)/ (α(α2)+γ) phase boundary shifting to Ti-rich side, whereas the (α(α2)+γ/γ) phase boundary shifting little. Si has effect on refining lamellar microstructure and makes the lamellae coarsen difficultly. The Si solubility in α(α2) phase is higher than that in γ phase thereas Si is an αphase-forming element in Ti-Al binary system. A third phase Ti5Si3 appears in the system with Si addition up to 1 .0% (atomic fraction). Correspondent: LI Juntao, Department of Materials Science and Engineering, Northeastern University.Shenyang 110006

Five petal star-shaped primary silicon in hypereutectic Al-Si alloy possesses a nucleating characteristic by agglomerating from tiny polyhedron clasters with simple shape.From the veiwpoint of thermodynamics, it is a spontaneous process that the five fine tetrahedron or octahedron clasters agglomerate in a way of fivefold twinning. The agglomerated polyhedron may grow into a five petal star-shaped primary silicon. By combining clasters with smaller size than that of critical nucleation, the polyhedron can acts as a stable nucleus of primary silicon. Correspondent: GUI Manchang, senior engineer, Post Box 81-3, Beijing Institute of Aeronautical Materials,Beijing 100095

Via embedded atom type potential and molecular dynamics simulation, surface energies of four low index lattice planes at six different temperatures have been calculated for B2 stoichiometric NiAl alloy. Surface energy increases gradually with the temperature; the closest-packed plane has the lowest surface energy: surface reaction such as reconstruction and compositional preference occurs on some specific surfaces at high temperature. Calculation of surface energy has also been performed for fcc structure Ni with similar method, and the results coincide with the known experiments. Correspondent: SHA Xianwei, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110015

The positron lifetime spectra of single crystals and polycrystals of three intermetallic alloys Ni50Al30Fe20, Ni50Al20Fe30 and Ni60Al20Fe20 were measured.Based on the characteristic parameters, a two-region trapping model for positron was introduced, and the relationship between the microstructure and mechanical properties was discussed Correspondent: XIONG Liangyue, associate professor, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110015

The electrochemical discharge capacity is in close relation with its crystal characteristics of AB2 type Laves phase hydrgoen storage alloy ZrCr0.4 Mn0.2V0.1Ni0.3, its capacity decreased shapoly from 324 mA · h / g to 25 mA · h / g after amorphization by mechanical milling of the crystalline (as-cast) alloy with stainless steel balls. Hydrogen atoms stored in the Zr2B2(B=Cr, Ni or V) tetrahedral interstitial sites of as-cast alloy lattice mainly contributed to its electrochemical capacity. However, for the amopohous alloy with the same composition the contribution to the electrochemical capacity is mainly resulted from the hydrogen atoms in Zr3B and Zr4 sites. It is believed that only haif sites in the crystilline or amorphous alloys can adsorb and desorb hydrogen atoms reversely. Extra energy induced during milling process can reduce the potential of electrochemical discharging of hydrogen reaction. Correspondent: YANG Xiaoguang, lecturer, Department of Materials Science and Engineering, Zhejiang University, Hangzhou 310027

(Fe,Ti)-N films with high content of Fe16N2 phase are prepared by facing target sputtering. Influences of doped titanium content on the structure and magnetic properties of Fe-N films are investigated. According to XRD and TEM results, optimum Ti additions enhance the formation of the 16:2 nitride, the values of saturation magnetization Bs for (Fe,Ti)-N films with Ti atomic fraction of 0—25% are larger than that for pure bcc iron, the maximum value for Bs is 2.68 T for the sample with 10% Ti, this value is 20% larger than that for pure bcc iron. Correspondent: WANG Heying, Department of Applied Physics, Tianjin University, Tianjin 300072

The continual high current density electropulsing and comparable isothermal annealing of Fe78Si9B13 amorphous alloy have been carried out. The microstructual change and crystallization behavior of amorphous specimens after treatment were investigated by Mossbauer spectroscopy. The results show that the electropulse treating promotes obviously the crystallization of amopohous alloy. The effect of electropulsing on crystallization is dependent upon the stimulation of pulse current to the diffusion of atoms in amorphous alloy. Correspondent: CHAO Yuesheng, College of Science, Northeastern University, Shenyang 110006

The Co / Ti multilayer thin films with an amorphous microstructure are prepared by dual facing target sputtering (DFTS) at room temperature. The evolution of the microstructure and magnetization in Co / Ti multilayer thin film during annealing has been investigated by in situ saturation magnetization measurements and the conventional transmission electron microscopy (TEM). Annealing results showed that crystalline Ti precipitated at 400℃ and Co at 500℃. Increasing temperature resulted in the coarsening of Co precipitates and the simultaneous growth of Ti grains. At temperature of about 600℃, Co phase disappeared and Co2Ti phase formed. The thermal magnetic measurement result also shows two clear magnetic changes at 390 and 520℃ respectively, corresponding to the changes in the microstructure of the film. The Co-Ti magnetic granular films can be obtained by annealing at moderate temperature. Correspondent: WU Ping, Department of Applied Physics, Tianjin University, Tianjin 300072

Strain rate and shear viscosity measurements were carried out on Pd-Cu-Si amorphous alloy with a Perkin-Elmer TSM-2 thermomechanical analyser under constant heating rate conditions. The minimum values of the shear viscosity accompanied by the glass transition and crystallization process have been observed. The heating rate dependence of the minimum values of the shear viscosity has been investigated. The viscous flow behaviour of amorphous Pd-Cu-Si alloy can be explained with the model of phase boundaries for the structural transition. Correspondent: SHUI Jiapeng, associate professor, Laboratory of Internal Friction and Defects in Solids, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031

Nanometer aluminum nitride powder synthesized by microwave heating is described in this paper. Aluminum nitride powder which purity is higher than 98% has been obtained by microwave heating the mixture of Al(OH)3 and carbon powder. The character of the nanometer powder is determined by means of XRD, TEM. The effects of temperature and carbon type on the fomiation of nanometer powder are discussed. Correspondent: DAI Changhong, Advanced Ceramics Department, Qingdao Institute of Chemical Technology, Qingdao 266042

Thermal diffusivity, α, of self-baking carbon block with different graphitization degrees was determined experimentally by means of laser-pulse within temperature range of 200—1100℃. The results show that the higher is the graphitization degree of carbon blocks, the higher is thermal diffusivity, α, at a given temperature; and α is decreased with the increment of temperature at a given graphitization degree. Resistance to thermal shock, R, of the carbon blocks was discussed from the experimental results. Correspondent: XUE Xiangxin, associate professor, Post Box 313, Department of Metallurgy, NortheasternUniversity, Shenyang 110006