In view of the statistical randomness and the dynamic necessity, analysis has been conducted on morphology development of solid-liquid interface in directional solidification. Based on the present experimental observations and the known dendritic models, a numerical statistical model of primary dendritic spacing is first presented to the dendritic array in directional solidification at constant velocity. The numerical model is in good agreement with the experimental results.

The solute distribution at the S/L interface is studied with stochastic dynamics. A general fuction relation between the solute distribution coefficient K and time t is given. The deviation of K from K0 (t→∞, K=K0) at the time t, being greater than the thermal equilibrium relaxation time ξ and smaller than the structural equilibrium relaxatin time ξ0, is also discussed. It has come to the conclusion that the deviation of K from K0, in K/K0, increases with increasing superheating temperature. This is in agreement with the result of experiment.

In order to predict the macrosegregation of unidirectionally solidified steel ingots, this paper modifled the continuum model for alloy solidification and put forward a model amenable to low alloy steels. On the basis of Fe-C binary model, the modification was made to draw into the effects of other alloying elements on the solidification process and the driving force for interdendritic fluid flow. Thus the segregation behavior of carbon was expected to be reflected more comprehensively by the model. In addition, the problems such as peritectic reaction, non-constant partition ratio were dealt with.

An effectual method that can determinate the surface heat-transfer coefficients was given by means of the solution of the inverse problem of the heat conduction for steel 45 cylinder with phase transformation during quenching. The technique is composed of numerical methods and determination of the relationship between time and temperature,and suited for various quenchants. It can avoid the considerable discrepancies in the obtained value due to small variation in the experimental condition.In the numerical calculation, the thermal physical properties of materials were treated as the functions of temperature and the volume fraction of consituent of phase transformation.

The formation mechanism of phase interface-layer with microcrystal structure in Ti(C, N)-based cermet has been discussed. The controlling conditions obtaining microcrystal transition layer should be met:(1) carbide phase microcrystallization, (2) composition undercooling during cooling process. The interface layer with microcrystal structure can improve the toughness, strength and stability of properties of the Ti(C, N)-based cermet.

In this paper the hardness change of Al-Zn-Mg alloy during aging-retrogression-reaging treatments was studied. The microstructure change and the mechanism of the change in hardness were studied by small-angle X-ray scattering.

Hot ductility of the continuously casted Nb-containing steel slab was measured under the strain rate of 1×10-3 /s. It was found that in the fractured specimens,Nb(C,N) precipitation took place when temperature decreased to below 1100℃. The Nb(C,N) particles precipitated in the temperature range from 1000 to 950℃ were coarse and rondomly distributed in the specimens. When the temperature was lowered to 900℃, the precipitation content of Nb(C,N) reached maximum and fine Nb(C,N) precipitates were found both along γ grain boundaries and inside the grains with mean particle size of 5-8 nm and interparticle spacing of about 30 nm. As the result of Nb(C,N) precipitation, the hot ductility of the steel was significantly reduced in the lower temperature region of γ single phase. As the temperature decreased to below 800℃, film-like proeutectoid ferrites formed aIong the γ grain boundaries that further reduced the steel ductility. The eutectoid transformation of the Nb-containing steel was delayed compared to the steel without Nb. This leads to the extension of the low ductility of the steel to the lower temperature.

Medium carbon and medium-high carbon air cooling micro-alloyed bainitic steels of Mn-Si-B system have been studied. The main structure is bainite or bainite/martensite after forging and air cooling, and there are carbides and a small amount of retained austenite. The structure is fine and uniform, and the addition of micro-amount elements can further refine the austenite grain and the bainitic structure.By modified treatments of mono, binary and ternary micro-alloying, the structures of various grades can be obtained, and their hardness, toughness and wear resistance increase successively. The structure of the air cooling bainitic steels with medium high carbon treated by ternary micro-alloyed after forging and tempering or nomalizing and tempering is much finer, the properties are much superior.

The tensile properties of alloy ZA27 at ambient temperature and elevated(from 275℃ through the solidus) temperatures were studied. The tress-strain plots at varies temperatures and the relationship between the mechanical properties of the alloy and temperatures are obtained. The results show that, the strength decreases with increasing temperature, the alloy exhibits high deformation ability at elevated temperatures, and the fracture modes are dependent on temperature. At about 275℃, alloy ZA27 has high plasticity and very small resistance to deformation, so it is suitable for the alloy to be processed by deformation at this temperature range.

As regard to several cases of real hot tearing ZG45 bars (C 0.42%-0.52%,Mn 0.5%- 0.8%, Si 0.2%- 0.45%), numerical simulation of stress-strain during solidification was conducted. The formation mechanism of hot tearing was discussed, and the conclusion is drawn that hot tearing originates from Bingham body and is caused when strain of Bingham body being over preserved plastic strain. The simulated results show that relative hot spot gives rise to increase in concentration strain of Bingham body, and that case of proper chilI could effectively decrease concentration strain of Bingham body, uponthere to reduce possibility of hot tearing.

The paper studies the flow pattern of molten steel in slab tundish by a hot water model. The results provide that the flow pattern with changed density is opposite from that with constant density because of heat loosing in tundish, which provides the natural convection in slab tundish shouldn't be neglected.

Calculating models of mass action concentrations have been formulated for molten binary salt systems involving solid solution, eutectic and compound formation respectively according to the condition that cations and anions combine together during reaction. The agreement between calculated and measured values is very well, while opposite results would get when the cations and the anions separate from each other. This shows that the cations and the anions combine together during reaction indeed, because of the deficiency of dielectric material for most molten salts.

In order to eliminate the surface defects of continuously casting metals, a casting process imposing an intermittent high frequency magnetic field from the outside of the mold is developed. Effect of the intermittent magnetic field on the motion of a molten gallium in a continuously casting mold, used as the simulator of a molten steel, was investigated by a laser level sensor. The relation between meniscus motion and surface quality was studied by continuously casting tin. It is found that the motion of the melt in the mold can be suppressed and the surface quality of the ingot can be improved by imposing intermittent magnetic field.It is noticed that the surface ripples corresponding to intermittent frequency, fi was formed on the ingot surface, and when fi is close to the intrinsic frequency of the experimental system, the effect of imposing magnetic field is the best.

By using plasma arc method an Sn-P bronze hardfacing formed on steel 25,which contains more strengthening phases. The wearing property of the friction pair consisted of Sn-P bronze and Cr-plated wheel is better than that of bronze QAl 9-4 and Cr-plated wheel.

New process has been developed to synthesize ultrafine Bi-Pb-Sr-Ca-Cu-O superconductor precursor powder with high homogeneity. First, nanoparticle suspension is prepared from mixed cation solution, and thus the inhomogeneity is limitted in nanosize level.Second, nanoparticles are transformed into ultrafine oxide particles with suitable phase assemblages with agglomerate possibility minimized as possible as it can be, and thereby the ultrafine state of bismuth-based superconductor precursor powder with low carbon content (≈200 μg/g) is prepared in short time by this new process, which can sintered into high Tc superconductor at lower temperature.

X-ray diffraction has proved that the structure of Y2Fe17-xMnx(x≤6.0) compounds is same as Y2Fe17. The study on the lattice constants, Curie temperature and magnetization of the Y2Fe17-xMnx compounds has shown that the lattice constants do not increase continuously with increasing Mn content and have a minimum at x=2.0. The Curie temperature increases from 328 K (x=0.0) to 342 K (x=0.3), and then decreases with increasing Mn content. The saturation magnetization decreases with increasing Mn content.

Structure and magnetic properties of quasi-ternary TbMn6-xCoxSn6 compounds with x=0.0, 0.3, 0.6, 0.9, 1.2 and 1.5 have been studied. The structure of TbMn6-xCoxSn6 compounds has not been changed on Co substitution. The substitution of Co for Mn in TbMn6Sn6 results in a monotonous decrease in the lattice constants and the unit-cell volume. The ordering temperature decreases monotonously with increasing Co content. The reorientation temperature decreases with increasing Co content and the reorientation of easy axis magnetization of TbMn6Sn6 disappeared at x=0.6. When x exceeding 0.9 a compensation temperature was observed in the thermal magnetization curve and the compensation temperature increases with increasing Co content. The saturation magnetization at 4.5 K decreases to a minimum at x=0.6 and then increases again.

Spray deposited 2014Al+ 15%SiCp and 18Ni (250) maraging steel+ 10%(Al2O3)p metal matrix composites (MMCs) show an accelerated aging behavior. The aging behavior of the MMCs was evaluated by the nanoindentation technique. It was found that there exists obvious gradient distribution of elastic modulus and microhardness around the reinforcement particles, which is the result of the gradient distribution of the reinforcing precipitates caused by the gradient distribution of the thermal misfit dislocation density. This result may provide the useful information for the more accurate prediction of the aging behavior of the MMCs with age hardnable alloy matrix.

The structures of SiO2 surface layer on the oxidized silicon carbide particles before and after compositing with aluminum matrix were studied by XRD and TEM. It is shown that the SiO, layer is crystalline when silicon carbide particles are oxidized at 1100℃ in air. It will be amorphized under the irradiation of high energy electron beam after being composited with aluminum matrix. The amorphization mechanism of the SiO2 layer was also discussed.