The distribution and diffusion of carbon atoms during deformation of undercooled austenite in the medium carbon steel were investigated by means of uniaxial hot compression simulation experiment and SEM, XRD, thermomagnetic methods. The experimental results showed that the effective diffusion coefficient of the carbon atoms during dynamic transformation of undercooled austenite increased significantly compared with that during the isothermal transformation at the same temperature, as a result the completion of ferrite and pearlite transformation was shortened. During the subsequent spheroidization process of lamellae pearlite, high density dislocations and vacanies introduced during hot deformation promoted the diffusion of the carbon atoms, therefore the cementite spheroidization kinetics was accelerated dramatically as compared to isothermal annealing treatment. The dissolution, re-precipitation of cementite and supersaturated carbon inside the ferrite grains were confirmed. The supersaturated carbon atoms were not located at interstitial sites within the iron lattices homogeneously, but highly segregated in ferrite grain boundaries and dislocation cores.

Quantitative analysis of strain-induced NbCN precipitates in a low-carbon high-Nb microalloyed steel with coarse grained austenite was investigated by applying double-hit tests and SUPRA55 field emission microscopy. The results have shown that the precipitation-start time adopts the C curve form. When deformed and held at 1000℃～900℃, the particle number density increases while particle diameter decreases with decreasing of deformation temperature. The precipitation kinetics obeys the modified Avrami equation and the Avrami exponent is about 1.1. The models developed in this experiment predict the precipitation-start time and precipitation kinetics well.

This work investigates the glass formation of Fe-B-Y-based multicomponent alloys designed using a cluster line approach. Cluster lines Fe8B3-Y, Fe8B2-Y, Fe83B17-Y, Fe6B-Y and Fe9B-Y intersect with cluster line Fe12Y-B at five compositions in the Fe-B-Y phase diagram that are taken as basic compositions. Further minor alloying by additions of 2 at.% Nb and 2 at.% M (M=Ti, Hf, Ta, Mo, Ni, and Sn) was designed and alloy rods were synthesized with a diameter of 3mm by suction-casting in copper mold. A. Considering mass loss of B and Y during arc melting, the ingots were all weighted after each melting and the final compositions were revised accordingly. When M=Ti, Hf, Ta and Mo, the quinary alloys form BMGs at compositions close to the Fe8B3-Y cluster line. This signifies that the close-packed Archimedes octahedral antiprism Fe8B3 is the basic atomic cluster that favors glass formation. The best glass-forming composition is (Fe69.9B24.6Y5.5)96Nb2Ti2 with Tg=944K, Tx=997K, Trg=0.666. When M=Ni and Sn, no glass formation was observed.

A eutectic Cu-71.8 wt.% Ag alloy was prepared by conventional process of fusion casting. There are approximate fifty percent of stepped phase interfaces with the step plane surface parallel to (111) and an orientation relationship between phases Cu and Ag symmetrized to the stepped interface in the eutectic structure. The stepped interfaces have a height equal to the average interplanar distance of Cu(111) and Ag(111) and the widths equal to the interplanar distances of 3-4 Cu(11-1). A coincident lattice site of Cu and Ag atoms can exist at the stepped interfaces at regular intervals of 3-4 Cu(11-1).

In order to disclosure the high damping mechanism of Fe-Mn alloy, the effect of deep-cooling and measurement temperature on damping capacity was studied, by measuring stacking fault probability and using G-L dislocation model. The damping capacity was measured using reversal torsion pendulum. The stacking fault probability and volume fraction of ε-martensite were determined using XRD. The microstructure was observed using SEM. The results indicated that the high damping mechanism was determined by the movement of Shockley partial dislocation, and not by ε-martensite. Because Deep-cooling increased the stacking fault probability in γ-austenite and ε-martensite, the number of Shockley partial dislocations also increased and the damping capacity of Fe-Mn alloy was improved. Higher temperature could decrease the unpinning stress between Shockley partial dislocation and weak pinning points. At a certain strain amplitude, therefore, with the temperature increased, the number of unpinning Shockley partial dislocations was more and the damping capacity of Fe-Mn alloy was improved.

Abstract: The corrosion behaviors of passive films of stainless steel 0Cr13Ni5Mo at the conditions of static state (quiescence) and ultrasonic cavitations in the hydrochloric acid solutions have been studied by means of electrochemical impedance spectroscopy (EIS) and capacitance potential measurements. The results indicated that the passive films showed a distribution of multi-layer structure and properties of p-type semiconducting in the conditions of quiescence. The outer-layer passive films were damaged and transformed to n-type semiconducting properties in the conditions of ultrasonic cavitations, with anode currents increased and corrosion rate accelerated. The local high temperature caused by cavitations lead to the increase of densities of donor (electron) in layer of passive films and the inversion of semiconducting properties.

In this work, LiCoO2 films were prepared with the pulsed laser deposition (PLD) method. Their structure was characterized by X-ray diffraction, Raman spectra and Scanning electron microscopy and their electrochemical properties were evaluated with cyclic voltammetry (CV). Results showed that LiCoO2 films prepared with PLD at 600℃ had a well-crystallized columnar HT-LiCoO2 structure with the average grain size less than 100nm and with a strong [001] preferred orientation, while these films contain trace amount of Co3O4. CV tests indicated that PLD-deposited HT-LiCoO2 films had good electrochemical reversibility but only a pair of redox peaks near 3.9V(vs Li) were observed in the cyclic voltammograms. Thereafter, emphasis was laid on the study of apparent diffusion of lithium-ion through LiCoO2 films using the potentiostatic intermittent titration technique (PITT). PITT measurements revealed that the lithium-ion diffusion coefficient of PLD-deposited HT-LiCoO2 films reached 10-8~10-9cm2s-1, 1-2 orders of magnitude faster than those prepared by other methods including R.F. magnetron sputtering and, in the voltage range between 3.85~3.95V(vs Li), the lithium-ion diffusion coefficient of PLD-deposited HT-LiCoO2 films was 1-2 orders of magnitude lower than other voltage ranges. The former should be ascribed to the grain refinement of PLD-deposited HT-LiCoO2 films and existence of many voids, while the later may due to the hindrance arising from phase boundary movement.

The deformation and the deposition morphologies of cold-sprayed Ni particles impacted on Cu alloy substrate at different gas temperatures were characterized. The results indicate that particle flattening ratio increases with the increase of gas temperature, but the increment rate decreases at higher gas temperature. Moreover, the bonding ratio increases due to the increment of material jet area at the interface. It is also found that a typical Ni particle impacted on the substrate consists of shear instability thin layer, severe plastic deformation region, and low plastic deformation region. The quality of the particle/substrate bonding is mainly governed by the shear instability thin layer, while the shape of the deposited particle is mainly governed by the plastic deformation regions. It is confirmed that the successful bonding between Ni particle and Cu alloy substrate can be attributed to the adiabatic shear instability mechanism.

Divided into two steps of a chemical reaction and a mass transfer process, the interfacial kinetics of oxygen transfer between two phases has been resolved mathematically, and a kinetic model has also been obtained. It was shown that the interfacial concentration of oxygen is varied with the process, so the oxygen transfer can be considered as a non-equilibrium process. By this model, the experimental data of some systems had been fitted. The results show that it is in good accordance with the experimental data and that the obtained parameters can explain the experimental phenomena well. In addition, the preliminary discussion on the meaning of parameters and their effect on the kinetics had been made.

The entrainment of steel and slag interface has a great effect on casting process and the product quality. The research described the interfacial behavior between fluid steel and molten slag layer in a slab continuous casting mold with high casting speed by numerical simulation method. Good agreement between the mathematical model and experimental observation was obtained. The influences of casting speed, mold width, port angle, submergence depth of SEN and molten slag viscosity on interfacial behavior were investigated. For a given casting speed, increasing the penetration depth and downward port degree can effectively restrain interfacial oscillations. Molten slag viscosity has hardly influence on interfacial profile of steel and slag. Steel-slag interface velocity decreases with increasing molten slag viscosity.

Oscillation marks formation for slab continuous casting with high casting speed was expatiated through stress analyses of initial solidifying meniscus shell during an oscillation cycle with stabilizing casting status at 2.0 m•min-1 casting speed, and the “Extra Liquid Volume” model about position of oscillation marks formation was explained. The results show that ferrostatic pressure, friction force and flux channel pressure act on shell bring on oscillation marks along with solidification progress, and the marks position primarily lies on solidified mass fraction of solidifying shell mushy zone.

Quasicontinuum simulations were performed to study the feature of plastic deformation in the initial stage of nanoindentation test of single crystal aluminium and single crystal copper using rigid cylindrical indenter. The corresponding load-depth loading and unloading curves at different depths were obtained. The contact stiffness, nanohardness and elastic modulus both single crystal aluminium and single crystal copper at different depths were calculated by Oliver-Pharr method. The calculated results using quasicontinuum method were compared with nanoindentation experiments published. The results show that the contact stiffness-displacement relations both single crystal aluminium and single crystal copper are linear. The simulated results indicate that the size effect phenomenon exist in nanohardness measurement both single crystal aluminium and single crystal copper. The nanohardnesses of them are 0.584±0.013GPa and 0.755±0.027GPa, respectively. Size effect phenomenon don’t exist in elastic modulus measurement both single crystal aluminium and single crystal copper. The elastic moduluses of them are 84.088±0.332GPa and 131.833±4.449GPa, respectively. The results calculated using the quasicontinuum method agree with the nanoindentation experiments, indicating that it is reliable and valid to measure the nanohardness and elastic modulus by using this approach.

In the present work, the 3D FE mathematical model which characterized the heat conduction in composites liquid-solid extrusion process was established. The 3D temperature field was obtained to reveal the temperature distribution and evolution of the billet using 3D heat conduction numerical simulation. The results indicated that during the pressure-keeping stage, the temperature field distributed evenly at the surface and inner part of the billet. In the extrusion process, however, they fluctuated tempestuously which lead to partial overheating on billet surface and result in superficial crack. The flaw analysis and forecast were validated to the experimental result of extruded product. The work laid a theoretical and technical foundation for the rational choice of process parameter to enhance product quality.

A 15v% SiC particulate reinforced Al-2618 matrix composite was selected to simulate its stress-strain curve and the stress in the reinforcing particles. The simulation was also carried out to compare a composite with soft matrix to that with hard matrix, and the necessary experimental data for the simulation were measured on specimens of the composite under different heat treatments. An analytical model was established based on Eshelby equivalent inclusion approach to do the simulation by introducing numerical secant modulus or tangent modulus scheme respectively. The same modeling work was carried out by FEM analysis based on the unit cell model using a commercial ANSYS code. Through the comparison of the results between the simulation and experimental results, it is shown that the Eshelby model can predict the stress-strain curve of the composite with both hard matrix and soft matrix by introducing different numerical modules, while the FEM model can not be used to simulate the stress-strain curve of composite with soft matrix. The stress in the particles is much higher than that in matrix shown by the simulation, which indicates that load transfer is the main strengthening mechanism for the composite.

Fully coupled thermo-mechanical model of friction stir welding is used to analyze the effect of axial load on friction stir welding process. Results indicate that the insufficient axial load leads to the failure of the friction stir welding. The material deformation on the top surface is affected by the rotation of both the welding pin and the shoulder, which causes that the material deformation on the top surface is higher than the one near the bottom surface. The material deformation is not symmetric to the welding line. The material deformation on the advancing side is higher than the one on the retreating side. The asymmetry of the material deformation can be weakened with the increase of the axial load. The maximum temperature of the welding plate during the friction stir welding process is increased with the increase of the axial load. The temperature field near the welding tool in the nugget zone can become more homogeneous when the axial load is increased.

Titanium alloy sheets exhibit significant plastic anisotropy that can be attributed principally to the presence of texture. Such plastic anisotropy has pronounced effects on subsequent sheet metal forming and springback processes. In the present paper, cylindrical cup drawing processes with titanium alloy sheets TC1M of 0.8mm thickness were simulated using ADINA FEM software. Three sorts of shape distortions phenomena exhibit in the drawing cups fabricated in room temperature after elastic recovery process: the inner wall is no longer a cylindrical surface, the lip periphery becomes wavy and the thickness distribution becomes unhomogeneous. A series of cup drawing tests were conducted and reasonable agreement was obtained between the predicted and measured profiles.

The effect of superheating on the sub-rapid solidified microstructure of AISI 304 austenitic stainless steel strip cast by water-cooled copper mould casting was investigated. The results show that the solidified microstructure of the as-cast strip of AISI 304 stainless steel is composed of cellular austenite, columnar ferrite dendrite, and equiaxed ferrite dendrite, from the surface to the center of the strip, respectively. With the increase of superheating, both the primary arm spacing of cellular austenite and the secondary arm spacing of ferrite dendrite raise, while the delta ferrite fraction decreases. As the melt superheating raises, the supercooling of melt falls, then the cooling rate of melt decreases, resulting in the increase of dendritic arm spacing of austenite and delta ferrite. The decrease of cooling rate also accelerates the transformation from delta ferrite to austenite during the subsequent cooling process after solidification, leading to the reduction of residual delta ferrite fraction.

We present ab initio calculations of the thermal properties of hcp metals Zr. We show that the thermal properties such as thermal expansions and heat capacities in hcp metal can be calculated precisely within the quasiharmonic approximation, by using phonon dispersions from density-functional perturbation theory, and the pseudopotential plane-wave method. Our results for the thermal properties are in good agreement with available experimental data in a wide range of temperatures.

The crystal structure and magnetic properties of non-stoichiometric MnFe（P，Si，Ge） alloys have been investigated by X-ray powder diffraction and magnetic measurements. XRD analysis indicates that all the samples consist of the hexagonal Fe2P-type structure phase mainly and a small amount of the second phase Fe2MnSi. The superfluous of Mn and Fe can reduce the Curie temperature which from 343K to 294K (superfluous Mn) and 286K (superfluous Fe). The superfluous of Fe can decrease the thermal hysteresis, but the superfluous of Mn can increase it. However, the entropy change as well decreased from 5.2 J•kg-1•K-1 (stoichiometric) to 4.9 J•kg-1•K-1 (superfluous Mn) and 3.8 J•kg-1•K-1 (superfluous Fe).

In virtue of Auger electron spectroscopy, it is found that the level of grain-boundary P segregation in GH4169 superalloy increases with the increase in solution treatment temperature. Based on this, the characteristic of NGS of P in superalloy is confirmed for the first time. The confirmation provides new theoretical and experimental basis for understanding the influence of P on mechanical properties of superalloys.