Oxygen atom adsorption on γ-TiAl(111) surface is studied using first-principles approach. The adsorption site with more Ti atoms as its nearest neighbors on the surface layer is found to be preferred. Adsorption energy differences between different adsorption sites become smaller with increasing of oxygen coverage. Electron structure analysis shows the chemisorption is characterized mainly by ionic bonds. The stability of γ-TiAl(111) surfaces are investigated in a range of oxygen chemical potential, which indicated that the clean surface can be energetically stable only when the oxygen chemical potential is very low. For higher oxygen chemical potential the clean surface becomes unstable, therefore, the oxygen atoms start to adsorb on it, and soon come up to high coverage.

A series of ultrafine-crystalline (ufc) pure copper samples with different densities of nano-sized twins were synthesized by means of the electro-deposition technique. Numerous dislocations were induced in the pure copper samples by means of cold rolling. After cold rolling to the deformation degree of 40%, the yield strength of ufc copper sample with high density of nano-sized twins increased from 690 MPa to 850 MPa, while the yield strength of ufc copper sample without twins increased from 230 MPa only to 330 MPa. The difference of strength increment suggests that the copper sample with high density of nano-sized twins has high storage capacity of dislocations.

Microstructural feature and evolution of nano-twin bulk Cu specimens produced by means of dynamic plastic deformation at liquid nitrogen temperature (LNT-DPD) have been studied using TEM. The results show that the microstructure of LNT-DPD Cu consists of high density of nano-scaled mechanical twins, nano-sized grains and coarse grains with high density of dislocations, which makes the LNT-DPD Cu exhibit a significant high tensile yield strength. Such a deformation structure was attributed to twinning and shearing during the LNT-DPD treatment.

The KKSM multi-phase field model is employed to simulate the eutectic growth in thin-film unidirectional solidification of CBr4-C2Cl6 eutectic alloy at low velocity. Three interface destabilization modes of eutectic lamellae, lamella annihilation, oscillatory instability and lamella nucleation, and the morphology selection of eutectic lamellae have reappeared veritably. With increasing of the initial lamella spacing, the stable morphology of the CBr4-C2Cl6 eutectic alloy evolved in the sequence of lamella annihilation→stable growth→1λO instability→2λO instability→lamella nucleation. The simulation results are in agreement not only with Karma et al's calculated results but also with Ginibre et al's experimental results qualitatively.

The conception of shape memory factor is defined to describe the superelasticity and shape memory effect of shape memory alloys. From the differential relationship between martensite fraction and free energy during phase transformation, a shape memory factor evolvement equation is established. Based on micromechanics theory, a 3-dimension constitutive model with considering the process of martensitic reorientation is developed, which possesses simpler mathematics form and clearer physics meaning than the previous models with the same functions.

The 3D deformation process of type-B PLC shearing band inAl-Cu alloy is captured by the help of a high speed digital photography with 1000 frames per second. A technique based on a novel high-speed digital speckle pattern metrology consisting of in-plane and out-of-plane deformation measurement methods is used for obtaining the playback of the 3D deformation process. The result shows one of the nucleation methods of type-B band: the shearing band initiates at a lateral specimen surface as a narrow band at an angle of 53 to the tensile axils and shears along the thickness direction. Subsequently the band front begins to propagate to the other lateral specimen surface along its length direction and expands in its width direction accompanying with the drop of the stress. When the front of the band reaches the other lateral surface, the band begins to expand in its width direction instantly and avalanchine shearing deformation happens. Based on the out-of-plane data, the relationship to the nucleation positions of following bands is that the latter one initiates on the front edge of the former one and the spacing of their center lines is half of the band width.

Cu-6%Ag (mass fraction) microcomposite, of which the primary structure consists of dendritic Cu matrix and non-equilibrium eutecticcolonies, was prepared by heavy cold drawing and intermediate heat treatments.The scales of different microstructural components were determined at different draw ratios and the strain compatibility was discussed by evaluating the strain level and strain increase rate for each microstructural component. The microstructural components display different strain levels and strain increase rates in different ranges of drawing strain because both have different characters of strain hardening. Therefore, the strain level and strain increase rate show a non-synchronous increase between both microstructural components with the increase of draw ratio when the microstructural components evolve from original as-cast morphology into filamentary structure.

Cu-Ag filamentary microcomposites with various Ag concentrations were prepared by cold drawing combined with intermediate heat treatments. The influences of Ag content on the microstructure evolution, tensile strength and electrical conductivity were investigated. The as-cast microcomposites containing 6%-24% Ag (mass fraction) consisted of -Cu dendrites, eutectic colonies and secondary particles. The eutectic colonies and secondary particles evolved into eutectic filamentary bundles and uniformed fine fibres during cold drawing. With the increase of Ag content, the tensile strength and strain hardening rate increase but the electrical conductivity decreases because the amount of the eutectic filamentary bundles and secondary precipitated fibres increases in the microcomposites. In special, the electrical conductivity loses more significantly if the Ag concentration is high enough to produce the eutectic filamentary bundles with a continuous net-like distribution. The eutectic filamentary bundles in the microcomposites with high Ag concentrations can produce greater benefit to the material strengthening than the secondary precipitated fibres in those with low Ag concentrations. However, the eutectic filamentary bundles can reduce the electrical conductivity more evidently than the secondary precipitated fibres.

The effects of DC electric current on the precipitation of γ '-phase in a Ni-based single crystal superalloy were studied. Under the action of different current densities the superalloy was cooled at different cooling rates after solution heat treatment at 1250 ℃ for 4 h. The experiment results show that the size and volume fraction of γ '-phase increase with the increase of current density, while the planar density of γ '-phase decreases at air cooling; under the action of the same current density, the size and volume fraction of γ '-phase decrease and the planar density of γ '-phase increases with the increase of cooling rate. It is considered that the electromigration effect induced by the DC current accelerates the diffusion of atoms during γ '-phase precipitation, which enhances the precipitation of γ '-phase, and the Joule heat effect produced by the DC current reduces the cooling rate, which speeds up the growth of γ '-phase.

The tensile properties at room temperature and stress-rupture properties at high temperature of a kind of Ni-based single crystal superalloy grown under a DC field were measured. The results show that the yield strength at room temperature is increased and the stress-rupture life and ductility at 980 ℃ and 221 MPa are improved, whereas the ultimate tensile strength at room temperature varies unnotedly and the ductility at room temperature is reduced. SEM observation and EMPA analysis showed that the prime dendrite arm spacing (PDAS), size of γ’ particles, alloying element segregation, eutectic and the sub-grain boundaries are reduced with the increase of the current. It is considered that the improvement of yield strength and stress-rupture properties arise from the refining of γ’particles and the change of γ/γ’misfits caused by reduction of microsegregation of alloying elements. Furthermore, the enhancement of the stress-rupture properties is also related to the reductions in the PDAS, eutectic and sub-grain boundaries under the action of the electric field.

The low-cycle fatigue tests with tensile hold times ranging from 0 to 60 min were conducted for 3 superalloys, HAYNES 188, HAYNES 230 and HASTELLOY X, at 816 ℃ and 927 ℃ under a total strain range control mode to investigate their creep-fatigue interaction behaviors. It was found that under creep-fatigue loading condition, the strain fatigue lives of the three superalloys are dependent on the type of the alloy, duration of strain hold, and test temperature. The different strain fatigue life behaviors exhibited by the three superalloys are related to the difference in the damages from creep and oxidation. In addition, the frequency-modified tensile hysteresis energy modeling was used to correlate the present strain fatigue life data. The result showed that this modeling could give a satisfactory prediction on the creep-fatigue lives of the three superalloys.

The in vitro anticoagulant property of a medical grade 316L stainless steel with 0.05% La addition was systematically studied. The results showed that, compared with the conventionally used medical 316L stainless steel, the La added 316L steel possesses less platelets adhesion and less activation of the platelets, and their kinetic clotting time and the plasma recalcification time become longer, which reveals that the activation extent of the latter on intrinsic coagulation factors is smaller than the former and the anticoagulant property of the latter is better. Through measurement of the contact angles of the steels, and calculations of the surface tension of the steels and the interfacial tension between the steels and the blood, the anticoagulant mechanism of the steels was analyzed from the viewpoint of surface energy.

ModeⅠdynamic fracture toughnesses KId for high strength steels, 40Cr and 30CrMnSiNi2A, subjected to impact loading with different loading rates were measured using an experimental-numerical hybrid method. The sensitivity of KId to loading rate for the steels were investigated. The tests were performed on three point bending specimens with Hopkinson pressure bar and the time of crack initiation was determined by strain gauge. With 3-D transient finite element analysis, the dynamic stress intensity factor histories under different loading rates were obtained and the dynamic fracture toughnesses were determined by fracture initiation time. The results show that within the loading rate range (10 6 MPa•m 1/2/s), 40Cr steel specimens failed by cleavage fracture, and the KId tendency is not clear with increasing loading rate. 30CrMnSiNi2A steel specimens failed to a large extent by ductile fracture and the KId value increases obviously with loading rate. Mechanisms of the results were discussed macroscopically and microcosmically.

Giant magneto-impedance (GMI) effects of FeZrBNi/Ag/FeZrBNi sandwiched films prepared by radio frequency sputtering on the substrate of single crystal Si have been measured. The maximum GMI ratios are 18% and 31% in longitudinal and transverse fields at 7 MHz and 8 MHz, respectively. Corresponding, the maximum effective susceptibility ratios are 153% (at 7 MHz) and 5117% (at 8 MHz) for longitudinal and transverse cases, respectively, indicating that the as-deposited FeZrBNi/Ag/FeZrBNi films have good sof magnetic properties and GMI effect.

Polycrystalline (Pr 1-x La x)0.75Na0.25MnO3 (0.00≤x≤1.00) manganites were prepared by sol-gel method. X-ray Diffraction patterns showed that the samples are crystallized in single phase with perovskite-like structure. The structure of the compounds transforms from orthorhombic structure for x≤0.50 to rhombohedral structure for x≥0.70. The introduction of La3+ ions also suppresses the charge ordering in the samples. The charge ordering transition temperature decreases with increasing La3+ doping when x≤0.10. The charge ordering phenomenon disappeared for the samples with x＞0.10, paramagnetic-ferromagnetic transition appeared, while the insulator-metal transition can be observed. For x≥0.50, the compounds also show large magnetic entropy change under low field near or above room temperature, indicating the material can be used in magnetic refrigeration.

Ta(x nm)/Ni65Co35 (40 nm) bilayers films (x = 0, 1, 2, 3, 4, 5 nm) have been prepared by DC magnetron sputtering. The effects of the thickness and deposition rate of Ta seed layer on anisotropic magnetoresistance(AMR) and coercivity of Ni65Co35 (40 nm) layer were investigated.XRD and magneto-test showed that a suitable thickness and higher deposition rate of Ta layer could promote the formation of Ni65Co35 layer with (111) texture, and remarkably increase the AMR value of Ni65Co35 layer and the sensitivity of magnetic sensor element.

Based on the measured data of mould temperatures and heat flux, an inverse problem of mathematic model was developed to calculate the field of heat flux for continuous casting round billet. The characteristics of non-uniform longitudinal and circumferential heat fluxes were shown explicitly. The calculated formulae of longitudinal and circumferential heat fluxes were obtained by fitting the calculated heat flux with considering the effect of casting speeds and mould installation statuses and were compared with the published experiential formulae. The inverse problem simulation and the fitted heat flux formulae are helpful for visualization of mould process and analysis of heat flux and accident in continuous casting round billet.

The dynamic temperature field during roll-bonding combined with high-frequency alternating current heating has been numerically simulated by a simplified model. In the simplified model, the governing equation of heat conduction is discretized using implicit finite difference method, and the computational domain is discretized using cell centered scheme, and the solution of Maxwell equation is used to determine the distribution of the internal heating sources. Considering the saltation of magnetic permeability of the ferromagnetic material when its temperature is more than the Curie point, the general solution of Maxwell equation is deduced. Based on our new method three kinds of composite strips (steel-Al, steel-Cu, steel-stainless steel) are performed numerically to validate the feasibility of the combination of various technical parameters.

Ti-Cu-N films containing approximately 0—10.0% Cu (atomic fraction) were synthesized by inductively coupled plasma assisted magnetron sputtering with two elemental targets. The effects of Cu content on film hardness and microstructure have been investigated. The addition of a small amount of Cu significantly enhanced film hardness. The Ti-Cu-N film containing 2.0%Cu has a superhard trait, with a hardness HV value of 42, which is nearly two times of that of pure TiN film. The Superhard Ti-Cu-N film was characterized as a nanocomposite structure, consisting of nanocolumns of TiN crystallites with nanocrystal Cu inside the column boundaries. The hardness enhancement was attributed to nanocomposite effect.

Elastic viscoplastic rate dependent constitutive model was used to simulate the friction stir welding process. The effect of process parameters on the continuous dynamic recrystallization phenomenon and hardness in the nugget zone was studied in details. Results indicate that the distributions of microhardness on the top surface and on the bottom surface of the friction stir weld are different. The former exhibits that the microhardness near the welding line is smaller, and the one outside of the nugget zone becomes bigger and then is equal to the hardness of the parent metal, which can be fitted well with the experimental tests. For the latter the above distribution law is not exhibited. The rotational speed of the welding tool only has little effect on the hardness distribution but the hardness in the nugget zone can be increased with the increase of the translational speed of the welding tool. The grain size near the bottom surface in the nugget zone is smaller than that in the middle of the weld. The size of the grain in the nugget zone becomes more homogeneous with the increase of the angular velocity of the pin.

A tungsten-wires strengthened Zr41.25Ti13.75Ni10Cu12.5Be22.5 bulk metallic glass composite was fabricated by a melt infiltration cast process. Quasistatic (1×10 -4 s-1)and dynamic (2×10 3 s-1)compressive experiments are carried out for the composite and monolithic material. The results showed that the composite exhibits a compressive strength of 1980 MPa which is similar to that of the matrix, and a plastic strain of 11.5% which is 5 times of that of the matrix under quasistatic compressive deformation. Under dynamic compressive load, the compressive strength of the composite is promoted to 2648 MPa, the plastic strain is in a range from 1.8% to 7.5% and the strain rate sensitivity of the composite is 0.022. Under quasistatic condition, the compressive strength is influenced by residual thermal stress and the critical stress of the tungsten wires. Under dynamic compressive condition, besides the residual thermal stress, the main factors are the shear fracture of tungsten wires and the sinusoidal buckling of the composite.