It has been considered that the boron segregation at austenite grain boundaries is responsible for the effect of boron addition on the properties of the steel, such as hardenability, creep fracture, etc. By means of particle tracking autoradiograph(PTA) the grain boundary segregation of boron has been investigated in Fe-30% Ni alley, quenched from 550—1200℃ at different cooling rates. It is shown that two kinds of grain boundary segregation, equilibrium and nonequilibrium segregation, caused by different mechanisms take place. The nonequilibrium grain boundary segregation during cooling with boron depleted zone adjacent to the grain boundary is very sensitive to the cooling rate, and can be inhibited by rapid quenching. The temperature effect on these two kinds of grain boundary segregation are different, As the quenching temperature increases, the grain boundary segregation of boron due to equilibrium adsorption decreases, while the nonequilibrium segregation kinetically increases. The nonequilibrium segregation therefore dominates in the specimens quenched from high temperatures; and the equilibrium segregation in those cooled from low temperatures. In this work, the transition temperature lies in the range of 650—750℃, increasing with enhancing cooling rate.

Directional solidification technique was used to determine the effect of Ce on the solidification structure of low-sulphur 16Mn steel: The results show that addition of Ce increases the primary dendrite arm spacing and decreases the secondary dendrite arm spacing, the width of Columnar region, the size of equiaxed grains and the degree, of micro-segregation of Mn. This technique is expected to be used to reduce the detrimental influence of impurity particles on solidification structures.

The microstructure of four liquid-phase-sintered W-Ni-Fe altoys with 90-95 wt-%W was investigated by means of optical and electron microscope and X-ray diffraction. It was found that there would be a precipitated phase formed in the 90W-Ni-Fe alloy in presence of a little carbon impurity and under the condition of slow-cooling after Iiquid-phase sintering. It was identified as a kind of A_6B_6C carbide of compiex face-centered cubic system with lattice constant of 1.0935 nm. Its morphology varies with the cooling speed and its empiric formula can be written as(Ni, Fe)_6W_6C approximateiy. After studying the heat treatment, the formation or elimination of this phase can be controlled.

A mathematical model has been established for the character of the variation of Sb concentration in the melt during the growth process of heavily Sb-doped Si single crystal. The calculated curve drawn with the model is in good agreement with the experimental one. As a result of the segregation of the solute during pulling, the concentration of Sb in the melt increases. It is found from the calculated curves that the increase of Sb concentration can be brought under control while the pulling process was carried out under a reduced pressure. Thus, the formation of cellular interface could be postponed. As the pressure in a furnace decreases to 2.7 kPa, the Sb concentration will be kept almost unchanged.

The distribution of Mg in a Ni-base superalloy was observed to be not only enriched along the grain boundaries, but also entered into the secondary carbides of grain boundaries and γ'-phase, either along grain boundary or in the grains.

The microstructure and fracture process of an eutectoid pearlitic steel have been observated and analysed by means of electron-diffraction-contrast technique and SEM. The fine structure of ferrite and cementite as well as the character of interface combination between the two phases in pearlite have been studied. The fracture process, which is characterized by layer structure was discussed in the term of crystallography. To evaluate the toughness level of pearlitie steels, a new macro-parameter, size of SOCC group, has been suggested.

The behaviour of hydrogen induced cracking of three low carbon alloysteels, 15Mn, 15MnVB and 20MnVB, has been studied in the aqueous solution of 0.1N HCl. Three different structures ,of them: bainite, tempered martensite and F/M dual-phase revealed after heat treatment. Using the data of the delayed failure and fracture mechanics tests, the σ_n/σ_(bn) vs t_f and da/dt vs K were plotted. The experimental results showed that the best susceptibility to hydrogen embrittlement resistance is the structure of isothermal bainite, the worst one is of tempered martensite and F/M duai-phase structure is obviously reduced the hydrogen induced cracking tendency.

Characteristics of tong (7mm) and short (0.2-0.4mm) fatigue crack propagation in 5C and 40CrNiMo steels with two stength levels have been studied. The fracture surface roughness and crack closure have been measured. It was found that the fatigue crack growth rate of short crack in low strength 5C steel is anomalously higher at a given stress intensity amplitude, but the threshold △K_(th) is lower. The difference in the growth behavior and threshold △K_(th) between long and short crack reduced with increasing material strength, that may be explained by crack closure effect.

Effect of the creep fracture toughness on crack initiation and propagation under creep fatigue interaction for three low alloying Cr-Mo-V steels and their micro-fracture proeesses has been mainly investigated. It showed that toughness of the material plays an important role in crack initiation and propagation. In the brittle state, the crack initiation under creep fatigue interaction is faster than that subjected to creep, and there is no remarkable difference of crack growth rate between them. In the ductile state, not only the crack initiation time is shorter, but also its crack growth rate is much faster. On the other hand, the creep fatigue interaction tends to embrittle the steel, which depends on the original toughness value of the steel. All the three Cr-Mo-V steels can be transformed from toughness into brittleness when they are in ductile condition. But, in brittle condition, this transformation is not clear.

In the present investigation, the influence of morphology and distribution of ferrite, especially the acicular ferrite in Widmansttten structure, on fracture behavior of low-carbon steel 16Mn at low temperature was discussed in detail. The microstructures of polygonal ferrite, intersecting aeicuiar ferrite and parallel aeicular ferrite were obtained by using interrupted-cooling procedure.If the arrangement is characterized by intersecting, the steel would possess the superior toughness at low temperature in comparison with that of polygonal ferrite. If the microstructure is mainly composed of parallel acicular ferrite, however, it would deteriorate the steel toughness.

The role of hydrogen in stress corrosion cracking (SCC)of austenitic stainless steels in boiling chloride solution was investigated. It was found that the threshold stress intensities for SCC of whether type 321 or 310 steel were much lower than that for hydrogen induced cracking (HIC) during dynamic charging at high fugacity at room temperature and 160℃,and the morphologies of SCC fracture surface differed from those of HIC. In addition, the anodic polarization promoted the SCC in boiling LiCl solution and the cathodic polarization with small current density retarded even restrained the SCC: These facts are important evidences cited as lending support to the anodic path dissolution of SCC of austenitic stainless steels in boiling chloride soluton. Hydrogen entering into the specimen via precorroding in boiling MgCl_2 solution with pH=1 for 200h was about 32 ppm, and it could cause elongation reduction but no HIC.The test in fused salt at 160℃ verified that HIC could occur if hydrogen enough and supplied continuously. However, there existed a critical hydrogen concentration during dynamic charging in 1N H_2SO_4 solution or in boiling LiCl solution, below which no HIC occurred.

The electron structures of H, He, Kr-void complex in Fe and the positron behavior in the complex have been investigated. It has been shown that the positron annihilation provides the information about the kind of impurity and the size of complex. The bound energy of impurity changes sensitively with the increase of the volume of complex.

The deformation a′-martensite in metastable Fe-Mn-Al-Cr alloys with the composition of 15—25wt-％Mn, 0-1.5wt-％Al, 0-0.4wt-％C and 0-1.2wt-％Cr has been studied by means of tensile tests at room temperature and -196℃. The following relationship between the quatity of deformation a′-martensite and the degree of deformation was confirmed: ln[a′/(1 -a′)]=lnA+Klnψ Statistical analysis shows that either lnA or K vary with the composition of alloys linearly at room temperature or-196℃.

The effect of hot deformation conditions on the recrystallization in Ti-10V-2Fe-3Al alloy was investigated. The working softening during deformation above T_β is due to the dynamic recovery. The recrystallization was considered as the static recrystallization following hot deformation. The volume fraction of recrystallzation decreases with increasing the deformation temperature. It is the temperature that causes the change of the β grain size prior to deformation. High strain rate will prompt the recrystallization.

Directionally solidified DZ-38G superalloy was in situ observed under SEM in order to obtain a better understanding of its slip deformation and fracture process. The slips initiate in matrix and eutectic, and they are able to be transmitted by the eutectic. The slips on dendrite arms are much obvious than those in the interdendritic areas. The slip direction may slightly alter with the change of columnar grain orientation. The microcracks are prone to initiate at transverse grain boundarie, carbides on grain boundaries or eutectic/matrix interfaces. A microcrack usually propagates along a zig-zag path, and it is controlled by the maximum shear stress and tensile stress. The propagation of cracks is closely related to the straightness of columnar grain boundaries.

Corrosion tests were carried out in simulating coal mine water for three light railway steels. Morphology of the corrosion rust layers was observed by means metallographic microscope and SEM; the structure of them was detected using X-ray diffractometer and the distribution of the alloy elements in the layers were determined by EPMA. The corrosion of these steels in given environments is an electrochemical process, in which cementite plays a role as cathode and ferrite as anode. The rust layers formed on carbon steel are not clearly stratified. A large number of cracks and holes were found in the rust layers, which make the steel protect from corrosion uneffectively. However, the rust layers on the steel 36 CuPCr and that made in Japan are stratified. The interior layer which consists of Fe_3O_4 appears to be very homogeneous, adhesive and compact. In addition, Cu, P and Cr concentrated in the layer and localized on the side nearby matrix. All these improve the corrosion resistance of steels.

The supercoductivity and structure of Y-Ba-Cu oxide have been investigated by means of electrical resistance and magnetic susceptibility measurements as well as X-ray diffraction, SEM and electron probe microanalysis. The results show that the onset temperature is 107.6K and the zero resistivity state occures at 94.8K with a width of about 2K for the sample of Ba_3Y_2Cu_5O_(5(3-z)). Diamagnetic susceptibility (Meissncr effect)was observed by magnetic susceptibility measurement, and confirmed with electrical resistance determination. The specimen consists mainly of hexagonal (or rhombohedral) ABO_3-type phase with lattice parameter of a=b=0.550nm, c=1.332nm and space group of R3c of R3m. The particles of oxide well connecte up each other, although quite a large number of pores exist. Zero resistance can be kept while up to 2A/cm~2 current passes through the sample.

Phase equilibria in Al-Mg-Sm system at 400℃ have been investigated by means of microstrueture and chemical analysis as well as X-ray powder diffraction techniques. 15 single-phase regions, 27 two-phase regions and 13 threephase regions were found in this system. The microstructural observations show that the solubilities of Sm in Mg_5Al_8 and Mg_(17)Al_(12) are less than 0.5 and 1.0 wt-％ respectively. No evidence of new phase has been observed in the system.

The standard oxidation/reduction potential of Al including its valence state in fused salt was examined, The anodic dissolution of Al can be shown by the equation Al→Al~3+3e. The standard oxidation/reduction potential of Al in fused salt is-1.122V as obtained by graphical method. Cathodic process has been investigated by means of steady state method. Separate potentials of some ions, the coefficient of diffusion ,of AlCl_4~- ion and kinetic constants of Al ion reduction have been meastured and discussed.

The new model developed by the authors is used to predict and simulate the ingot and slag composition during the ESR process of Cr-Mo-V turbine rotor steel on an industrial unit. The results are shown to be in excellent agreement with those of practical process in an ingot diameter of 2300mm, also to agree with observations on Ca and Al deoxidation, and the model may be expected to offer a practical basis for the control of Composition during the ESR.

The temperature which separates upper and lower bainitic transformations is about 300℃ in nodular cast iron. The overall activation energy of lower bainitic transformation of it is nearly the same as that for high carbon steels, but that of upper bainitic transformation is much smallar than the value of latter. this can be explained by the fact that the addition of Si suppresses precipitation of Fe_3C. The following orientation relationships have been observed by the present work: N-W relation for ferrite and austenite in upper bainite; K-S relation for ferrite and austenite in lower bainite and Bagaryatski relation for Fe_3C and ferrite in lower bainite.

The room temperature and 500℃ isothermal sections for Cu-rich (Cu+1.0 at.-％Ni)-Al-In and (Cu+1.0 at.-％Sn)-AI-In phase diagrams have been determined using X-ray diffraction method. The solubilities of Al and In in α-Cu were found to be 10.8 and 2.7 at.-％, respectively, at room temperature, and to be 19.0 and 10.5at.-％, at 500℃, while 1.0 at.-％Ni was addition. However, in the case of 1.0 at.-％Sn addition, the corresponding solubility values become 18.7, 4.9, 22.0 and 11.6 at.-％, respectively. The results show that the addition of small content nickel makes Cu-rich Al-Cu-In alloys heat-treatable.

Some empirical rules governing the crystal type of AB_3 type alloy phases have been obtained by pattern recognition method. By computerized prediction, we have predicted that Dy-Ir, Gd-Ir and Nd-Ir systems form AuCu_3 type alloy phases. Based on this prediction, we have prepared Dy-Ir, Gd-Ir and Nd-Ir alloy samples and haste proved the existence of DyIr_3, GdIr_3 and NdIr_3 alloy phases, with AuCu_3 structure Their lattice parameters are: a=0.3842nm, a=0.3839nm and a=03836nm respectively.

The solubilities of Neodymium in pure iron were determined by the positron annihilation method. In iron cooled slowly to room temperature or exposed at 760℃ for 72h, they are 0.082wt-% and 0.088wt-% respectively

The thermal stability of amorphous Fe_78Co_4.3Si_5.9B_11.8 thin film prepared by sputtering has been studied using thermomagnatie measurements, differential thermal analysis, electron microscopic analysis, electron diffraction and X-ray diffraction. It is observed that the crys-tallization process of sputtering film is different from that of melt quenching ribbons. The crystallization temperature of the former is much lower than that of latter. The preparing condition have an important effect on the thermal stability.

The coarse oxide inclusions isolated from either horizontal or curved continuous casting strands were examined on their content,shape,composition and size distribution bv means of the slime method and elecrtoprobe. They are oxides of SiO_2-Al_2O_3-MnO system. About 80% or more of them are coarser than 80um. The inclusion content in the horizontal continu-ous casting strand is far more than in curved one owing to preventing the secondary oxida-tion by clo e connection between the tundish and mold. Thus, the protective casting is avail-able to improve the steel purity.

Hyperfine parameters of Fe sublattices in Nd_2Fe_(14)B have been deduced by refering to the magnetic moment values of Fe for different sites obtained by Givord et al using polarized neutron diffraction technique. By examining the ~(57)Fe Mǒssbauer spectra of Co doped specimen, it is observed that Co atoms, while their amount is small, preferentially enter k_2 site of Fe and thus creat unequivalent sites of their nearest neighbors, e. g. k_1 and j_2 Fesites. And they will enter other Fe-site if more Co was doped.

The effects of annealing treatment on the activation energy, Curie temperature and Mos-sbauer parameters of FeZrBiSiB metallic glass have been investigated by DTA technology and magnetic measurements Different relaxation processes were found at the temperatures below or above 327℃. The conception of short range locolized relaxation and medium or long range cooperative relaxation have been used to analize the mechanism of these two relaxation stages. It is considered that the variation of △Tc reflects the information about the interaction between the antiferromagnetic clusters and ferromagnetic matrix during rela-xation process. And the variation of Mossbauer parameters could be explained by TSRO and CSRO relaxation processes.

Laser quenched microstructure of HT 21-40 grey cast iron Was studied by transmission electron microscopy. Results indicated that the structure is consisted of fine acicular martensite and ultrafine grained austenite. The carbon content of austenite is about 1.8%, that can also be transformed into fine acicular martensite when cooled in liquid nitrogen.

The fracture behaviour of tetragonal ZrO_2 toughened Si_3N_4 ceramic composite has been investigated using acoustic emission technique, X-ray diffraction, SEM and TEM. The results show that the fracture toughness increased markedly by addition of t-ZrO_2. The t-ZrO_2 particles show a considerable resistance to transformation. It is considered that the toughening mechanism of t-ZrO_2 addition might be crack deflection, crack branching and microcrack toughning.

EXELFS of graphite has been analyzed by maximum entropy method (MEM) and fast fourier transformation (FFT). Comparision of the two methods shows that MEM gives much higher resolution than FFT does.