Study was made of the microstructural morphology and phase transformation mechanism of the "ferrite+islands" formed either as granular bainite in upper region of temperature range of bainitic transformation or as so called "granular structure" in temperature range of pro-eutectoid transformation in the low carbon alloy steels. The granular bainite stands out in surface relief during its transformation Its ferrite grows up longitudinally and form parallel laths The K-S orientation relationship is kept between ferrite and austenite The morphology of its islands appears as the shape of short lath and with a tendency of being parallelly distributed in the bainite-ferrite matrix. The granular structure does not stand out in surface relief in the formation of equiaxial ferrite. It's ferrite can grow across the grain boundary of parent phase, and has no strict orientation relationship with parent phase The shape of the islands is irregular, and its arrangement on the matrix is also irregular. The grain boundary of austenite couldn't be revealed clearly Except the difference of the transformation temperature, the granular structure possessed Widmanstatten ferrite is similar to the granular bainite in characteristics. Finally, the models of the growth of granular bainite and granular structure are suggested.

An observation under TEM was made of the (M-A) structure and "bamboo shaped" bainite in the isothermally quenched ultra high strength steels containing Si after the isothermal transformation The retained austenite in the isothermal structure of bainite region at temperature≥300℃ is often found in the M-A and "bamboo shaped" bainite In the bainite formed isothermally at 180, 300, 320 and 420℃, the ε-carbide is observed. The type of carbide in decomposition products is related to the distribution and morphology of retained austenite. The ε-carbide may precipitate along the austenite side of martensite/austenite boundary.

The method for the determination of alloyed amounts of rare earth metals in steels developed previously by the authors was verified to be appropr ate Using this method, the alloyed amount of Ce in steels 16Mn, 25MnTiB, Cr24Ni7Si2N and Fe-Cr-A1 alloy has been analysed The microautoradiographs show that the alloyed Ce distributed among the pearlite is more than that among the ferrite in 16Mn or 25MnTiB steel. An enrichment of Ce was obviously observed by autoradiography to be segregated along the grain and dendrite boundaries in Fe-Cr-Al alloy or Cr24Ni7Si2N when the Ce content is notl ow The microscopic inhomogeneity of Ce distribution is presented among different grains of the Fe-Cr-Al alloy.

A study was made of the behaviour of retained austenite to improve the contact fatigue strength of the carbonitriding gear steel 25MnTiBR by means of the contact fatigue test, the fracture mechanics analysis of spalling on contact surface and the energy estimation of crack tip plastic zone The retained austenite deformation induces the martensite transformation, which absorbs energy more than one half of the strain energy of material It may retard the propagation of fatigue cracking and may improve the contact fatigue strength of the carbonitriding steel 25MnTiBR with retained austenite The proper material together with a reasonable technique chosen for production practice may be available to obtain more and not very stable retained austenite in the surface layer of the gear, especially, it may improve the gears under heavy load.

The aging structure and deformation structure of the 18Ni(350) maraging steel have been studied The dominant age strengthening phases are Ni_3Mo and Ni_3Ti, or Ni_3Ti and reverse austenite in the specimens after heat treating at 820℃ for 1 h, A.C.+480℃ for 3 h A.C., or at 820℃ for lh, A C+510℃ for 3 h, A.C. respectively A brittle zone is found in the specimen of under aging at 820℃, 1 h, A.C. +400—450℃, 3 h, A. C., This is, perhaps, resulted from an ordered or short range ordered martensite Imatrix The proper regime of aging at 510℃ for 3 h, A C. is available on the basis of structural analysis and property examination.

The modification of five Al-Si alloys of different purity and composition with 9—14 wt-% Si at various cooling rates influenced by an additive Sr or Sb has been investigated in detail by means of SEM, EPMA, etc. The microstructural nomograph of these Al-Si alloys is constructed to provide for the selection of optimum addition of Sr or Sb in production practice Experimental results indicate a threshold of Sr content in Al-Si alloy modification, over it, the structure of Al-Si alloy may be completely modified even at quite slow cooling rate down to 4.5℃/min. The threshold increases with the decrease of cooling rate Both Sr and Sb can retard the initiation of Si precipitation, but differ in the influence on the growth form of eutectic Si

The microstructure of adiabatic shearing band for β-Ti alloy deformed at high strain rate was observed undermetallographic microscope and SEM. Three types of adiabatic shearing bands, namely, the deformation band, the transformation bands with fine stripped microcrystalline structure and with equiaxied very fine microcrystalline structure are found in sequence Under very large deformation, it may be cracked along the adiabatic shearing band With regard to discuss the criterion of adiabatic shearing, the distinction among the adiabatic shearing deformation, the adiabatic shearing fracture and the thermoplastic instability is important

A model with local composite structure is used to simulate the microstructure of nodular cast iron at a small crack tip region of the three-point bending specimen This model allows to get a solution close enough approaching the solution of a real material The J-integral in a material with composite structure is discussed It is found that the fracture toughness of nodular cast iron is practically the fracture toughness of steel with holes The effects of the graphite shape, size, volume fraction etc. on the stress intensity factor and fracture toughness of nodular cast iron are also examined. In the finite element calculation, the elastoplastic increment theory with finite deformation has been used The calculated results agree well with experimental data

The behaviour of the grain boundary in the growth of austenite grain in alloy structural steel and the mechanism of the austenite grain growth have been observed under high temperature microscope and successively taken photomicrograph in situ It was shown that the growth of initial austenite grain and the coarsening of grown grain are substantially resulted by migration of the grain boundary which revealed mainly in moving, coalescing and disappearing of the boundary and "corner"

The process of stress induced transformation in 51.6 at-%Ni-Ti alloy has been studied by means of X-ray diffraction and TEM equipped with loading attachment The results show that the process may proceed as two stages: premartensitie and martensitie transformations It seems to be reversible with unloading

The electrical resistivity of paramagnetic CuNi alloys in composition range between 30 and 42 at.-% Ni due to spinflip scattering of conduction electrons from individual and coupled spin-clusters was studied by using the disordered spin-cluster model Together with the ρ_L(T) phonon contribution, the total resistivity can be written as: ρ=ρ_L(T)+ρ_0(0)-nρ_1lgT+A n~2/T The resistance minima that was observed in the experiments was explained by using the results.

A thin foil electron microscopic study has been made of the various morphologies and microstructures of the carbides Cr_7C_3 and M_(23)C_6 in HK40 (4Cr25-Ni20) austenite casting steels The orientation relationship between the M_(23)C_6 precipitates and the austenite matrix during high temperature tempering has been identified by electron diffraction patterns The morphologies and Burgers vectors of the dislocations in the austcnite matrix, carbides and interfaces have been examined The weak beam and Moire pattern techniques have also been used in the analysis

Hydrogen induced cracking (HIC) of a high strength steel 34CrNi3MoA (TS=1700 MPa) under mode Ⅱ loading was investigated using notched specimens. The stress field around the notch tip was analyzed by means of finite element method. The result shows that the HIC under mode Ⅱ loading initiates at the back of the notch tip, i. e., θ=-110°, where hydrostatic stress has the maximum value. However, cracking is oriented along the shear stress direction at the site, not normal to the direction of maximum principal stress component. On the contrary, if the specimens are loaded to fracture in air under mode Ⅱ loading cracking at the maximum shear stress site around the notch tip and the cracking direction coincides with the direction of the maximim shear stress. The facts above mentioned indicate that hydrogen induced delayed plastic deformation is a necessary condition for HIC.

A new method has been developed to solve the problem of complete integration of the Gibbs-Duhem equation along phase boundaries in a c-component and c-1-phase system. Two variables, (△_1)_(1i)=D_i/D_i and (△_i)_(1i)=D_i/D_(1i), are introduced into the Gibbs-Duhem equation for multicomponent systems. And the function φ suggested by Chou for use in a miscibility gap of ternary systems is extended. Activities of component f on whole phase boundaries may be calculated from the known experimental values of a_1 by means of the modified Gibbs-Duhem equation without integral difficulties.

The liquid boundary of the slags of Ce_2O_3-CaO-CaF_2 system and the iso-activity lines for Ce_2O_3 and CeO_2 are given from experimental determination of the activity of Ce_2O_3 by equilibrating the slag with Sn in a graphite crucible under an atmosphere of CO at 1600℃. The activity of Ce_2O_3 in the slags containing certain CeO_2 or CaO, increases with the increase of concentration of CaO or CeO_2 respectively. The transition of CeO_2 to Ce_2O_3 under the condition of high temperature and low oxygen partial pressure was also discussed by thermodynamical analysis.

The influence of solidification rate, modifying agent added and fading on the morphology of graphite were investigated by means of the technique of the liquid metal cooling directional solidification. The model of growth of graphite crystal was also proposed.

The study was carried out on the decomposition mechanism of barite in the sintering mixtures of Jiuquan barite-containing iron ore concentrate during sintering, and on the interaction between barite and other constituents It showed that the decomposition of barite in sintering mixtures started at 1190℃ in air, and reached its maximum rate at 1240℃ During sintering, the decomposition mechanism of barite is the solid-state reaction between barite and Fe_2O_3 which takes place at high temperatures and the product under oxidized atmosphere is BaO.6Fe_2O_3 For the sintered Jiuquan sintering mixtures the product is (BaO. 6Fe_2O_3). 1.81 (CaO.2Fe_2O_3) The apparent activation energy of barite decomposition in air is 119.9 kJ/mol and the order of reaction is 1.3—1.4 obtained by kinetical calculation.

Study was carried out of the reducibility of titania-rich slags with relation to their high temperature properties under heating stage microscope The temperatures of fusibility and fluidity of the slags sampled at intervals of reduction smelting increase steppedly with decreasing FeO content and increasing reducibility In both ranges of 22.21>FeO wt-%>12.68, 0FeO wt-%>5 44, 0.11 References | Related Articles | Metrics

By using X-ray diffraction and TEM techniques, result has been shown that the inside of single roll quenched ribbon of BNi2 alloy, namely, Ni_(70)Cr_7-Fe_3Si_8B_(12) is amorphous but both the free and roll sides of this amorphous ribbon consist of Ni crystals with a preferred orientation of 111 parallel to the ribbon surface This structural inhomogeneity implys that the momentum transport mechanism plays an important role during the solidification process of this ribbon In addition, the unknown metastable phase appeared on the second stage of crystallization is a fcc phase with a≈1.04 nm of M_(23)B_6 type.

The reductions distributed over the reducing zone are closely related with the axial plug force (APF) during rolling on the LD cold tube mill XIIFP60 The distribution of the APF is influenced by the rolling pressure distributed over the reducing zone and the inhomogeneity of fhe tube reduction The numerical analysis of APF indicates it may be the sum of a transient and an accumulated acting forces.

The Mossbauer spectra of Ni9 steel foil and extracted return austenite, γ′, have been studied. Four kinds of surrounding for Fe-atom nucleus are found in the steel The Fe-Ni atom cluster which consists of one Fe atom and two nearest neighbouring Ni atoms (2nnNi) is considered as the critical state of transformation to austenite The atom cluster of this type in the specimen quenched from α+γ region is more than that undergone conventional heat treatment The stable γ′ has yielded more abundant in the former than in the later Futhermore, the γ′-phase increases with the increase of tempering temperature because of the migration and enrichment of Ni atoms.

The electrical resistivity of amorphous (Fe_(1-x)V_x)_(84)B_(16) (x=0—0.1) alloys as a function of temperature between 4.2—300 K has been studied. It was shown that the resistivity minima over the whole concentration range seem to be presented; below T_(min) it showing maxima at x=0.02—0.1; over T_(min), as a T~2 temperature dependence. The low temperature resistivity anomaly is likely to originate from Kondo-like effect, RKKY interaction and localized spin-fluctuation scattering.

The dependence of microhardness on the Co or Ni concentration has been measured for amorphous Zr_(100-x)M_x (M=Co, 22 x≤53.4; M=Ni, 24.1 x≤63.8) alloys. It is shown that the microhardness increases systematically upon increasing the concentration of Co or Ni. The effect of structural relaxation on the microhardness has been investigated for Zr_(78) Co_(22) and Zr_(75.9)Ni_(24.1). The microhardness exihibits a minimum and, then, increases slowly during isothermal annealing at 250℃. For isochronous annealing at differe nt temperature the microhardness increases very sharply when the crystallization temperature is approached. Complementary experimental results of DSC, resistivity, superconducting-critical-temperature and X-ray-diffraction measurements are used for an analysis of the phenomena occurring during structural relaxation and crystallization.

The structural relaxation of the amorphous alloys Fe_(77.8)Si_(7.5)B_(14.7) and Fe_(78.5)Si_(8.9)B_(12.6) was studied using Mossbauer technique together with DTA and resistivity. It is likely to have two stages, low and high temperature, of structural relaxation. The low temperature stage is mainly showed as relieving distorted stress and locally ordering atomic arrangement; and the high temperature stage as the long-range diffusion and segregation of metalloid atoms as well as nuclear growth.

The effect of the slag system and addtive, including alloying element and deoxidizer, on the non-metallic inclusion removal from the electrothermal alloy 0Cr25A15 in the process of the electroslag remelting has been examined. The choice of slag system containing RE, the addition of Al as deoxidizer and the use of consumable electrode free from Ti are found to be the favourable conditions for remelting technique.

The tendency to fishscale on the enamel steel sheets of TC_1, 08F, 08Al, etc. has been investigated by the electrochemical H-permeation method. It showed that the fishscaling is closely related to the diffusion coefficient of hydrogen in steel. With the increase of the deformation and the Ti/C ratio of steel, the diffusion coefficient of hydrogen may be decreased and thus its tendency to fishscale may be also decreased.

The positron life-time spectra in Fe_(38)Ni_(40)Mo_4B_(18) glass at different temperatures have been measured and the annihilation mechanism has been discussed.

A criterion of the cell-dendrite transition in the unidirectional solidification rate, R, of single phase binary alloys was proposed as R>2D_L/λ, where D_L is diffusion coefficient in liquid and λ is distance between principal branches of cells and dendrites. The experimental verification was made of the Al-Cu alloy by the authers and of the previous data collected.