The key and most recent research results on bainite transformation obtained by Phase Transformation and Multi-Phase New Materials Research Group of Tsinghua University have been generalized in this paper,including the objective and popular existence of three-dimensional super and nanometer scale ledges, the mobility of ledge risers, internal ultra fine structure of bainitic plates, the characteristic and nature of bainitic surface reliefs, the source and formation models of bainitic carbide, STM and AFM studies of martensitic surface reliefs, etc. The sympathetic nucleation and ledgewise growth (SNLG) formation mechanism of bainite has been further described, and applied to interpret the multi-layer complicated substructure. Also the industrial application of air-cooled bainitic/martensitic duplex phase steel has been related.Correspondent: WANG Jiajun, associate professor, (Department of Materials Science and Engineering,Tsinghua University, Beijing 100084)

The effects of Ni content on the transformation temperature (T_R,T_M), transformation heat (△H_R,△H_M), hysteresis(△Θ_R,△Θ_M) of martensite (M) and rhomboheddrel (R)transformation in Ti-(33.3-75.0)% Ni alloys have been investigated systematically by DSC and optical microscopy. It has been confirmed that there are no transformations during cooling and heating processes in Ti_2Ni(Ti-33.3%Ni) and TiNi_3(Ti-75.0%Ni) alloys; T_M, △Θ_M,△H_M and △H_R are functions of Ni content; T_R and △Θ_R are constant and almost independent of Ni content. Correspondent: HE Zhirong, associate professor,(Department of Mechanical Engineering, Shaanxi Institute of Technology, Hanzhong 721003)

Ni-10% Fe and Ni-35% Fe alloy melts were undercooled with glass fluxing technique by 371 (0. 90 △T_h) and 343 K (0. 91 △T_h) .Their hypercooling limits △T_h were determined to be 413 and 376 K respectively. A new method to measure the integral mean specific heat C_(pL) of undercooled metallic melts was developed according to the definition of hypercooling. That is, one can take C_(pL) as the ratio of latent heat of fusion △H_m to hypercooling limit △T_h, provided that the latter two physical parameters have been obtained through experiments. The C_(pL) values of the above Ni-Fe alloys were found to be 41. 0 and 40. 7 J/ (mol . K). Theoretical calculations were also carried out to reveal the relationships of enthalpy change △H_(LS), entropy change △S_(LS), Gibbs free energy change △G_(LS) and crystal nucleation rate I during rapid solidification vs undercooling. Although the maximum undercoolings achieved by both Ni-Fe alloys have exceeded the critical level of 0-2 T_L, the calculated results indicate that heterogeneous nucleation must have taken place in preference to homogeneous nucleation. Those heterogeneous nucleants with a wetting angle range of 53°< θ< 80°played the dominating role to prevent Ni-Fe alloys from further approaching their hypercooling limits. Correspondent: WEI Bingbo, professor, (Department of Applied Physics, Northwestern Polytechnical University, Xi'an 710072)

Particle pushing is one of the basic problems involved during solid-liquid phase transformation. Classical theory suggested that particle pushing is governed by the surface energy interactions, but this theory could not used to explain particle pushing occurring during the production of some metal-matrix composites. the authors propose that particle pushing is a result of fluid flow that occurs at the front of the solid-liquid interface. Two mechanisms for particle pushing as a result of fluid flow are presented and the criteria for particle pushing are derived. Experiments, carried out to verify the mechanisms and the criteria,show good agreement with theoretical model.Correspondent HAN Qingyou,(Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH, England)

The variations of properties and microstructure of a cold-rolled rapidly solidified AIFeVSi alloy during high temperature annealing were investigated in comparison with an as-extruded alloy. Unexpectedly, cold-roll did not promote the change of properties and microstructure in the annealed alloy. This might result from the low work-hardening effect, dislocation multiplication during annealing, retardation of the recrystallization by strengthening dispersoids and anneal-hardening phenomenon existing in the cold-rolled alloy.Coarsening dispersoids and migrating grain boundaries were thought of as the main dislocation sources at high-temperature. Correspondent ZENG Yuxiao, lecturer,(Department of Materials Sciences and Engineering, Central South University of Technology, Changsha 410083)

The morphology of white layer generated within the surface layer of the steel specimens by the impact wear has been studied by TEM. It is shown that the sub-structure of white layer consist of a complex dislocation distribution. There are lamellar, cellular,polygonal, equiaxial morphologies which lay properly below the worn surface. The different morphologies are arisen out of the inhomogenous deformation. The results confirm the deformation mechanism of white layer formation further. Correspondent: YANG Yeyuan,(postdoctoral worker,National Tribology Laboratory, Tsinghua University,Beijing 100084)

The dual property TC11 Ti alloy compressor disk of 420 mm in diameter has been manufactured by the techniques of pretreatment and isothermal forging under controllable strain. The disk bore is of the equiaxed structure with high strength, ductility and low-cycle fatigue and the rim with basket-wave microstructure has high resistance to high temperature creep and high fracture toughness. This process is more simple and the production quality is more controllable as comparing with the conventional one. The properties of the bore and rim of the disk is satisfied over the specifications of conventional mechanical properties.Correspondent: YAO Zekun, associate professor, Faculty. No.402, (Northwestern Polytechnical University, Xi'an 710072)

Coating of TiC particles coated with Ni-Cr alloy on the surface of 5CrNiMo steel specimens has been obtained with CO2 continuous laser treatment. The microstructure of the coating was investigated. The results show that TiC grains are preferably encircled by Cr phase. The gliding band formed in Ni crystal and the deformation twinning formed in Cr crystal are due to solidified stress. The TiC phase in interdiffusion zone dissolves more easily in Fe-matrix than in Ni-Cr phase. The microcrystals of a and y phase were also observed and their formation is related to the dispersively precipitated TiC. Correspondent: AN Shimin, associate professor,(National Laboratory of Material Modification,Dalian University of Technology, Dalian 116023)

A computer simulation on the distribution behaviour of As, Sb and Bi during copper flash smelting has been carried out by using a mathematical model as well as the results of the overall equilibrium calculations. The results are in good agreement with those obtained from previous studies and industrial data. The effects of some operating conditions such as matte grade, oxygen potential, temperature and contents of minor elements in concentrate were predicted and elucidated. Correspondent YIN Aijun,lecturer,(Institute of Metallurgical Physicochemistry and New Chemical Materials, Central South University of Technology, Changsha 410083)

Fe-Si-B alloy has been produced from the Liaoning ludwigite by carbothermic or carbon-aluminothermic method. The effects of reducing time and temperature on B, Si and C contents in melt were investigated, and the relationship between C content and B and Si contents in melt was also discussed. The residual AI in melt was excluded by means of slag-metal equilibrium method, and the variations of Al content in melt with basicity and B and Si oxides were determined. The experimental results showed that it is feasible to produce Fe-Si-B alloy from Liaoning ludwigite and C and Al in alloy can be controlled down 0. 15% and 0.05% respectively.Correspondent: LIU Sulan, associate professor, P.O. Box 119, (Northeastern University, Shenyang 110006)

The effects of the multi-component (Y_2O_3-Al_2O_3) coating on the surface oxidation of the Ni-base cast superalloy M38 and Y microalloyed M38 (mass fraction of 0.04%) exposed to air at 1000℃ have been investigated. The oxidation kinetics of M38, M38+(Y_2O_3-Al_2O_3) and M38+Y+(Y_2O_3-Al_2O_3) follow the approximate parabolic law. The mass-gain of M38+Y is very rapid at the initial stage and slow after about 50 h. The sequence of mass-gains after 200 h oxidation is M38>M38+(Y_2O_3-Al_2O_3)>M38+Y+(Y_2O_3-Al_2O_3)> M38+Y. The morphology and component of the oxide scale on M38 are changed remarkably by the alloying of Y and the coating of (Y_2O_3-Al_2O_3) thin film. The grain size of oxide is fined and the selective oxidation of Cr and Al is promoted. Correspondent: HE Yedong,(professor, Corrosion and Protection Centre, University of Science and Technology Beijing, Beijing 100083)

The calculated results indicated that the effective medium theory is available and convenient for discribing the conductivity of metal film during the film formation. The little difference between the theoretically calculated and experimental results was discussed in detail. Correspondent: CAO Xiaohui,(postdoctoral worker, State Key Laboratory of Catalysis, Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023)

α-Fe_2O_3 ultrafine particles were prepared by precipitation method. The Mssbauer spectra of three samples with various grain size were measured at room temperature and one of them in temperature range from 295 to 80 K. The results indicate that the internal magnetic field has varied obviously with the change of grain size and environment temperature mainly due to collective magnetic excitations. The magnetic anisotropy constants of the samples with various grain size were obtained by the studies of collective magnetic excitations. Correspondent: LI Haibo,(Department of Materials Science, Jilin University, Changchun 130023)

The coercivity of sintered Nd-Fe-B magnets is enhanced by the addition of a small amount of WC and the highest one corresponds to an amount of 0.6% WC addition. But a higher amount of WC addition leads to the decrease in coercivity. The grain size decreases first and then increases with increasing the WC content. SEM observation revealed that W-Fe-B phase with colony-like shape appears at grain boundaries or in some matrix regions, and that the contents of C and W in the regions near to W-Fe-B phase are higher than other regions. Correspondent: SONG Xiaoping,(College of Materials Science, Xi'an Jiaotong University, Xi'an 710049)

High temperature deformation behaviours of a binary FeAl compound and FeAl based alloys added different Ti contents have been investigated. The elongations of FeAl-Ti alloys were larger than that of the binary FeAl compound under an initial strain rate range of 2.08×10~(-4)-8.33×10~(-2) s~(-1), tested at 900-1000℃. The strain rate sensitivity index, m, is over 0.3 commonly. With the increase in Ti content in FeAl alloys, m value and elongation increase significantly. The maximum m value and the maximum elongation were up to 0.43 and 297% respectively. Microstructure analyses and TEM graphs show that grains became fine and subboundaries were formed during superplastic deformation, which resulted in the superplasticity in large grained FeAl-Ti alloys. Correspondent: LIN Dongliang,(professor, Department of Materials Science, Shanghai Jiaotong University, Shanghai 200030)

The mechanical alloying of Mo-Si powder mixture with atomic ratio of 1:2 under different milling conditions has been studied by means of X-ray diffractometry (XRD), SEM and TEM. It is found that the higher energy milling favours the formation of stable α-MoSi_2, while the lower energy milling promotes the formation of metastable β-MoSi2. Thermodynamics and kinetics aspects related to the different phase transformations have been discussed. Correspondent: QIN Yong,(senior engineer, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031)

The combustion reaction was observed during mechanical alloying Ni_(20)Ti_(50)C_(30), and the agglomerates and powders coexisted in final product. With the analysis of X-ray diffraction (XRD) and the observation of scanning electron microscope (SEM), it is indicated that melting occurred in the combustion reaction. The product is composed of TiC phase and NiTi compound. It is regarded that the initial TiC is produced by the heavy collision of balls during milling, and then the large heat released from the TiC formation induces the latter reactions. Correspondent: YE Lilei,(Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110015)

Creep fractured surface of SiC_p-Al composite was quantitatively analyzed by employing image processing technique and solid mechanics principles, and the effective creep strain was determined. It was found that there is exponential relationship between cavity volume fraction and effective creep strain in the vicinity of fracture surface, which elucidates that the cavity growth during tertiary creep stage was controlled by plastic deformation. The presented testing principle and method could be applied to other plastically deformed materials containing cavities. Correspondent: WANG Daifeng,(Institute of Composite Materials, Shanghai Jiaotong University, Shanghai 200030)

According to the stress analysis of dumbbell fibre-reinforced composite, the weakly bonded interfaces in the composite materials with brittle matrix were investigated. It is shown that the bending strength of concrete reinforced by fibres with enlarged-ends is 20% higher than that by plain fibres. The well distributed stress and the increased pull-out resistance because of enlarged-ends are the important reasons. It means that this biomimetic model gives rise reinforcing effect not only to plastic matrix but also to brittle one. Correspondent: ZHAO Xiaopeng, (Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110015)

Atomic absorption spectrometry (AAS) has been applied to investigate the kinetics of pitting propagation for 321 stainless steel in 0.5 mol/ L NaCl media. The results indicate the occurrence of the active corrosion of metals in the pitting holes. Fe, Ni and Mn, in form of divalence, and Cr in form of trivalvence dissolve into solution. On the basis of AAS data, the influence of the amounts Fe2+ and Cr3+ dissolved in corrosion pits upon the autocatalytic processes is discussed. Correspondent: SONG Shizhe, professor,(Department of Materials Science and Engineering, Tianjin University, Tianjin 300072)