Recent progress in solidification theory related to the high growth rate during rapid solidification has been summarized. Methods for quantitative analyses of non-equilibrium partition coefficient, nucleation incubation time, phase selection, absolute stability of planar interface, rapid dendrite or cell growth as well as solidification development in a bulk specimen have been presented.Correspondent: SHEN Ningfu, professor,Research Centre for Materials, Zhengzhou Institute of Technology,Zhengzhou 450002

In order to study the microscopic mechanism of martensitic nucleation and growth proeesses, molecular dynamics simulation of thermally induced martensitic transformation in stoichiometric NiAl alloy with B2 structure has been perfomied via the embedded atom method interatomic potential of NiAl alloy. The phase stability analysis of NiAl at 0 K and constant volume shows that an ordered bct structure with a ratio of lattice parameters of about 1.31 is stable while B2 structure is just metastable. The results of the simulations clearly show that only at some special sites caused by different vibrational properties of Ni and Al atoms the themially induced martensites can nucleate heterogeneously, and this has been further proved by simulations of two other systems with different initial configures. By calculating mean square displacements of Ni and Al atoms in NiAl, the reason of heterogeneous nucleation has been explained. Austenite transformed finally to fct L1_0 martensites, and during the martensite growth processes many transformation twins have formed in martensite.Correspondent: SHA Xianwei, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110015

Fe_3Al alloys in B2 structure with different order degree are studied by means of field－ion microscope (FIM). Whether or not the maximum B2 order degree got, the total regularity of the FIM image is so poor that it is even difficult to know the B2 order degree qualitatively. However, the local evaporation characters of the〈100〉pole contain the information of B2 ordering. By successive examination, it is discovered that the evolution of B2 ordering is not homogeneous in nano－scale. The result got from the〈120〉pole is the similar to that from the〈100〉pole. This consistence confirms once more the conclusion"only the Al atoms contribute to the image while the Fe atoms are invisible" .Correspondent: ZHI Rentao, professor, Deportment of Materials Physics, University of Science and Technology Beijing, Beijing 100083

The microstructure of 9Ni steel was investigated by means of TEM and HREM. In specimans heat treated under different conditions, it was discovered that there was an angle difference of about 5.3 degree between [110]_M directions of adjacent two lathes in a martensite bunch. This paper provides a transformation model of similar Bain relation:(010)_A ∥(110)_M, [101],∥[111]_M, and it can rationally explain the phenomenon above mentioned.Correspondent. MENG Xiangmin, Laboratory of Atomic Imaging of Solids, Institute of Metal Research,Chinese Academy of Sciences, Shenyang 110015

An investigation has been made on the microstructure of the surface layer in pure iron ion-nitrided with RE(rare earth) ions (Ce~+, La~+). Analysis by EPMA shows that the peak value of distribution of nitrogen element inside the pure iron with ion RE-nitridation is about 100 μm deeper than that with ion nitridation. Investigations by SAED and HRTEM show that the γ'(Fe_4N) phase exists as the uncomplete 6H type long period structure due to the effect of RE elements. There is a near K-S orientation relationship between a-Fe and γ' phase. The RE elements also exist as intermetallic compound (Ce, La)Fe_7which has approximate orientation relationship with α-Fe as follows: Correspondent: WU Yaqiao, Laboratory of Aiomic Imaging of Solids, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110015

The influence of heat treatment on growth of precipitates in Ti-5Al-1.5Nd and Ti-SAl-4Sn-1.5Nd(mass fraction, %) alloy was studied in detail. The experimental results show that many near spherical precipitates are present in the matrix of rapidly solidified titanium alloys containing neodymium. But along the grain boundaries, sub-grain boundaries and dislocation lines, and so on, some particles are deposited in the form of strings of pearls. When Ti alloys containing neodymium are subjected to heat treatments at 650, 700, 750, and 800℃ for 1, 8, 27 and 56 h, respectively, the precipitated particles coarsen slowly. EDAX results show that these particles in the Ti-5Al-1.5Nd alloy are found to be rich in Nd. On the basis of the electron diffraction pattern, these particles are identified as Nd_2O_3 with a cubic structure and lattice parameter a=1. 108 nm. The activation energy for the growth of particles is estimated to be 117 kJ/mol. The addition of tin improved the dispersed degree and reduced the rate of growth of these particles which are found to contain both Nd and Sn by the EDAX analysis. And the average atom ratio of neodymium and tin is about 1.37 : 1 in these particles. Electron diffraction analysis shows that the fine precipitates are orthorhombic Nd_5Sn_4 with lattice parameters a= 0.814 nm, b = 1.732 nm,and c= 0.8 14 nm. The growth activation energy of the particles is estimated to be 170 kJ / mol.Correspondent: YAN Ying, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110015

The microstructure features of stainless steel have changed remarkably after laser surface remelting and solidification. Light band, fine cell, cell-dendrite structure and disordered dendrite are found in the surface layer, meanwhile, the causes for their formation have been analyzed. The typical cell-to-dendrite transition is observed at the center of laser melt pool, and a detailed investigation on the transition conditions shows that the critical transition velocity determined by experiment agrees well with the prediction of recent BJT model.Correspondent: PAN Qingyue, Lab.403, Northwestern Polylechnical University, Xi'an 710072

By physical modelling, the recovery phenomenon of inner crack in 20MnMo steel at high temperature was discovered, and its regular pattern was concluded.It was believed that the recovery process was mainly controlled by the diffusion and migration of metal atoms. The recovery process can be divided into two steps, void filling and grain growing. The filling materials consisted of many very fine grains with segregation of iron. There was a very clear boundary between the filling materials and matrix. The grain growing and composition homogenzing occurred simultaneously. Inner cracks and voids can be filled and taken away in a certain deformation. A certain holding time was necessary for grain growing and inner crack recovery entirely.Correspondent: HAN Jingtao, associate professor, Department of Metalworking, University of Scicnce and Technology Beijing, Beijing 100083

The effect of polarization on the dislocation behaviours of A537 low alloy steel in 3.5% NaCl active system during low cycle fatigue was studied. The results showed that in the system A537/3.5% NaCl, after the specimens were fractured at the same strain amplitude and various polarization potentials, the dislocation structures near the surface were wall structure at -580 mV(SCE) and -1200 mV(SCE), and cell structure at -800 mV(SCE) cathodic protective potential.Correspondent: WANG Jianqiu, Institute of Corrosion and Protection of Metals, Chinese Academy of Sciences,Shenyang 110015

The sessile drop method and four points bending test were used to study the wettability and joining strength of Sn-based solders on Sialon substrates. Under vacuum of 1.33 Pa and holding 20 min at 1173 K, the contact angle of Sn-based is lower than 20 degree,while the joining strength of the soldering joints on rough vacuum may be markedly improved with the addition of zinc or lead, The average joining strength of Sialon/Sialon joints, soldered with Sn-5Cu-STi, Sn-5Cu-5Ti-20Zn, Sn-5Cu-5Ti-10Pb, are 90.8, 154.3 and 169.1 MPa respectively. And the maximums of joining strength are respectively 119.8, 200 and 216.1 MPa for three solders. In rough vacuum, Sn-based active solders may finish the joining of Sialon/Sialon, and the residual stress is reduced. On the other hand, alloy component zinc in Sn-based solders obviously affects precursor film in rough vacuum.Correspondent:ZHUANG Yanxin, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110015

A mathematical model and corresponding computational results describing the three-dimensional turbulent flow, thermal dispersion and inclusion behavior in tundish were presented in this study. The predicted flow fields were compared with the measurements in aqueous model. Building up the synthetic mathematical model of tundish process and simulating it by computer may efficiently modify the working conditions and improve continuous casting technology.Correspondent: SHENG Dongyuan, National Research & Engineering Center of Continuous Casting Technology, Gentral Iron and Steel Research Institute, Ministry of Metallurgical Industry, Beijing 100081

Flow stress curves of five types of brass were experimently studied with a cam plastometer at a constant deformed speed. The effects of the deformed temperature, determed rate and deformated degree to flow stress were analysed. At the same time, non-linear regressions to mathematical models with different structure were conducted. Through comparision and analysis, mathematical models with higher fitting accuracy were proposed.Correspondent: GUAN Kezhi, professor, Institute of Mechanical Engineering, University of Science and Technology Beijing, Beijing 100083

A numerical simulation technique based on the stable alternating direction implicit(SADI) method and the upper bound element technique(UBET) is presented and applied to simulations of the direct extrusion process of liquid metal during solidification (the process is hereafter called "liquid extrusion" for short) which involves solidification and large plastic deformation in one process. The computer-generated animation displays the forming process of workpiece lively. The simulative results are helpful to a better understanding of the technology of liquid extrusion.Correspondent: REN Xiangqian, lecturer, Centre for computer, Wuhan Transportation University, Wuhan430063

The surface films respectively formed by 5454 Al-Mg alloy tube and pure aluminium tube in carbonated solution were studied using AES, XPS, SIMS and CWT. The results show that the main composition of the surface film is hydrated oxide of aluminium.The thinner the surface film is, the better corrosion resistance behaviour it has. The intensification of magnesium results in the better anti-corrosion property of the alloy than that of pure aluminium. The content of magnesium ions in the surface film is two orders of magnitude higher than that in the inner matrix.Correspondent: FANG Yaohua, associate professor, Department of Applied Chemistry, Nanjing University of Chemical Technology. Nanjing 210009

The core loss spectrum P(f) of soft magnetic alloy with constant permeability has been studied. It is found that P(f) has the fractal structure. The effect of the induced anisotropy energy K_u on the fractal dimension D_f is discussed.Correspondent: DAI Wenmin, associate professor, Department of Physics, University of Science and Technology Beijing, Beijing 100083

W/Si multilayer for soft X-ray optics was deposited by magnetron sputtering. The periodicity and interface roughness of the multilayer were studied by low-angle X-ray diffraction at a X-ray diffractometer, and analyzed with dynamical theory of X-ray diffraction. Good fitting between simulational and experimental curve has been obtained with a model that allows for interface asymmetry.Correspondent: WANG Fengping, Department of Material Physics, University of Science and Technology Beijing, Beijing 100083

Phase composition of pseudobinary ZrM_2 alloy (M= Ni_(1.3), Mn_(0.6), Cr_(0.25), V_(0.05)) has been revealed by means of multiphase Rietveld analysis. It is consisted of C14, C15 Laves phase, ZrN, Zr_7M_(10) and Zr_9M_(11) intermediate phase. The abundance order of phases is following. ZrM2(C15)>Zr_7M_(10)> ZrM_2(C14)>Zr_9M_(11)>ZrN. Nonstoichiometry defects existing in A sites of C15 Laves phase were also discovered. The crystal types of Zr_7M_(10) and Zr_9M_(11) are the same with that of Zr_7Ni_(10) and Zr_9Ni_(11) respectively.Correspondent: L Guanglie, Institute of Material Structure, Hangzhuo University, Hangzhuo 310028