Abstract:The neodymium –based (Nd-based) conversion coating was obtained on the surface of AZ31 magnesium alloy. The formation process of Nd-based conversion coating was examined by weighting experiment and open cruit potential (OCP) test. The coating morphology, micro-structure and composition were characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy(XPS) and X-ray diffraction (XRD)，respectively. The variation of morphology between bare sample and coated sample immersed in 3.5 wt.% NaCl aqueous solution was investigated, the results showed that the Nd-based conversion coating can effectively reduce the corrosion speed in 3.5 wt.% NaCl aqueous solution. The composition and corrosion resistance of post-treatment on Nd-based conversion coating were measured by XRD and electrochemical experiments. The post-treatment can perfectly improve the corrosion resistance of the Nd-based conversion coating.

Abstract:The corrosion behavior of Gd56Al26Co18 and Sm56Al26Co18 amorphous alloys in 0.01 M NaOH solution had been researched by polarization scanning, EIS technique, XRD and SEM. The free volume was also investigated by DSC technique. It was found that the corrosion resistance of amorphous alloys increased after remelting.

Abstract:By using Y2O3/CeO2 powder, instead of part of Al2O3, acting as filler, Y2O3/CeO2-modified aluminide coatings were produced on Ni based using a conventional pack-cementation method at 600℃ for 10 h. For comparison, normal aluminide coating was also produced using pure Al2O3 acting as filler. Effect of Y2O3/CeO2 in the pack on the alumina phase transformation and cyclic oxidation resistance in air at 1000℃ was investigated. The results indicated that Y2O3 and CeO2 have a different effect for ?-? phase transformation: Y2O3 suppresses the growth of the ?-alumina but CeO2 promotes the q-a phase transformation. However, compared to the normal aluminide coatings, the addition of Y2O3/CeO2 significantly improved the cyclic oxidation resistance due to the formation of adherent alumina scale, especially the later. The effects of Y2O3 /CeO2 on alumina phase transformation and cyclic oxidation resistance are discussed in detail.

Abstract:An Inconel 718 alloy was coated by WC-17Co using a high-velocity oxygen fuel (HVOF) thermal spray process. The residual stress of WC-17Co coating under different heat-treatment conditions was investigated. The effect of residual stress on bending fatigue life of the coated alloy was discussed. It was found that fatigue cracks were initiated at the WC-17Co coating and propagated to the alloy substrate. The compressive residual stress generated during HVOF process could restrict the initiation and propagation of cracks. The absolute value of the compressive residual stress in WC-17Co coating decreased after annealing treatment, resulting in a lower fatigue life of the coated specimens.

Abstract:Ag2CO3/SrCO3 rods were prepared by a facile precipitation method using AgNO3, Sr(NO3)2, and Na2CO3 as precursors. The as-prepared samples were characterized by X-ray di?raction (XRD), scanning electron microscopy (SEM), nitrogen adsorption–desorption isotherms, and UV-visible (UV-vis) diffuse reflectance spectroscopy. The photocatalytic activity was evaluated by photodegradation of methyl orange (MO) aqueous solutions under visible-light irradiation (λ > 420 nm). The results show that Ag2CO3/SrCO3 rods become thinner and shorter with the decrease of Ag2CO3/SrCO3 molar ratio. The as-prepared Ag2CO3/SrCO3 rods showed excellent visible-light photocatalytic activity. Moreover, Ag2CO3/SrCO3 composites exhibited an enhanced photocatalytic acticity compared with that of the monocompoment Ag2CO3 and SrCO3. Ag2CO3/SrCO3 rods with the Ag2CO3/SrCO3 molar ratio of 1:5 exhibited the highest activity due to the synergetic effects of the large surface area and the heterostructure.

Abstract:In the present paper, some turbine wheels produced by metal injection molding (MIM) were subjected to x-ray inspection using different three x-ray equipment. An x-ray inspected turbine wheel was then cut and polished to observe defects by OM and SEM equipped with EDS. The defects existing in the blades and the center of the turbine wheels were analyzed statistically using MINI TAB software. The results show that, under the same testing condition, the film x-ray equipment has higher sensitivity than the real-time imaging x-ray. However, the microfocus x-ray testing is not suitable to the MIM418 turbine wheels due to low power. NDT and metallographic observation exposes that Maro-cracks are prone to forming in the center part of the turbine wheel, and the mi-cro-defect in term of porosity in the blade is higher than that in the center of the sintered turbine wheel, and decreases significantly after heat isostatic pressing (HIP).

Abstract:A highly active photocatalyst TiO2/g-C3N4 was facilely synthesized by a facile two-step method, sol-gel method and calcination using Ti(OBu)4 as Ti source and melamine as nitrogen source. The structural and morphological properties of the resultant photocatalysts were characterized. The results showed that TiO2/g-C3N4 was formed and TiO2 was beset with graphite-like carbon nitride of layer structure. TiO2/g-C3N4 exhibited obviously enhanced visible light photocatalytic activity, and the degradation efficiency of Methylene blue (MB) reached 94.46% after irradiation for 1h, which was much higher than that of g-C3N4 and TiO2. The improved photocatalytic activity of TiO2/g-C3N4 was attributable to its wide spectrum responsive range, strong visible light adsorption capability, and the synergistic effect between TiO2 and g-C3N4. The mechanism of photocatalytic reaction was discussed.

Abstract:Hot deformation behavior of as-cast TC18 titanium alloy has been investigated in the temperature range 1000-1150℃, the strain rate range 0.01~10 s-1 and the deformation degree was 70% by the Gleeble-3800 simulator. The deformation activation energy was evaluated; processing maps for hot working were established on the basis of variable of efficiency in power dissipation with temperature and strain rate, and interpreted according to the microstructure observation. The optimum processing parameters of hot deformation in the range of this experiment attained by different variables of the hot processing map, which can be used as a reference for hot working of as-cast TC18 titanium alloy.

Abstract:Micro-fine spherical alumina (Al2O3) powders have been synthesized in this work with irregular feedstock materials by the SY119-30kW induction plasma sphroidization system. Effects of main operating parameters in fabrication process have been discussed and characteristics of the powders were investigated. The results show that the obtained powders with smooth surface exhibits fantastic sphericity, preferable density and better flowability. The purity of the fabricated powders has been improved and the phase compositions characterized by X-ray diffraction (XRD) shows the same results under different sheath gas (Ar or N2) conditions. Different axial positions of the injection probe strongly influenced the effectiveness of the treatment and Z=12.9cm would be the better choice for Al2O3 spheroidization in this experiment. The spheroidization efficiency of synthesized powders is almost 100% at feeding rate of 65g/min with the chamber pressure of 11.5psi (1atm=14.696psi), which decreases gradually as the feeding rate increases. The chamber pressure was also the vital factor that influenced the fabrication process and it should be coordinated with the carrier gas flow rate.

Abstract:In the industrial production of nitric acid by oxidation of ammonia over multi-effect group Pt-Rh-Pd alloy gauzes catalysts the division of ammonia oxidation zone, knitting structure, components, oxidation rate and the principle of a gauze pack has prompted a number of investigations into their behavior. This paper reports on a survey of surface structure of individual gauzes in multi-effect group Pt-Rh-Pd alloy gauzes by field emission scanning electron microscopy (FESEM) and EDS analysis and offers some indications towards the choice of gauze weight and economic effects.

Abstract:Electrochemical corrosion behaviors of friction stir welding (FSW) and MIG(mixed inert gas) welding joints of 6082 Al alloy and parent material 6082 Al alloy were investigated in a solution of 0.2M NaHSO3 and 0.6M NaCl ,by using potentiodynamic polarization curve and electrochemical impedance spectroscopy(EIS) and scanning electron microscopy (SEM) observation. The corrosion rate of the FSW joint was less than those of MIG joint and the parent material; the corrosion potential of the FSW joint was more positive than those of MIG joint and the parent material, the corrosion current density of the FSW joint was less than those of MIG joint and the parent material, the polarization resistance of the FSW joint was bigger than those of MIG joint and the parent material. EIS Nyquist loops indicated that an inductive arc existed on the complex plane.SEM observation showed that a few shallow pits presented on the surface of the FSW joint, however, a large number of deeper pits emerged on the surface of the parent materials and MIG joint.

Abstract:The present article described the spectra properties of aged gold colloids, which were synthesized by only adding NaOH to chloroauric acid and Hexadecyl trimethyl ammonium bromide (CTAB) mixture solution. The formation mechanism for the fabrication of gold nanoparticles (AuNPs) was discussed based on the Fourier transform infrared spectroscopy (FTIR) analysis. The gold colloids with the different amount of NaOH were aged three months and characterized by UV-Vis spectrometer and transmission electron microscopy (TEM). Moreover, surface-enhanced Raman scattering (SERS) spectra of methylene blue (MB) on the aged three months gold colloids were obtained. UV-Vis spectrometer showed the broadening of plasmon absorption peak of aged three months gold colloids. And an explanation for the broadening changes was provided in the as-prepared samples. TEM images demonstrated that the diameter and shape change of the AuNPs depended on adding different of NaOH on the stage of the synthesis, and the NaOH was also affected the aging process. The corresponding SERS spectra on the aged three months gold colloid displayed the size/shape-dependent properties. The aged colloidal gold was expected to exploit and utilize in biochemical analysis field.

Abstract:According to retrogression and re-ageing treatment (RRA), a novel retrogression and stress-ageing treatment (RSA) is put forward for Al-Zn-Mg-Cu alloys. The effect of stress-ageing time and external stress on precipitates of pre-retrogressed Al-Zn-Mg-Cu alloy is investigated by transmission electron microscope (TEM). It is found that there is a large number of matrix precipitates (MPts) and slightly discontinuous grain boundary precipitates (GBPs) in the pre-retrogressed alloy. The effects of stress-ageing time and external stress on precipitates of the retrogressed alloy are significant. With the increase of stress-ageing time and external stress, the size of MPts increase and the density of MPts decreases. Meanwhile, the size of GBPs, the distance between GBPs and the width of precipitate free zone (PFZ) increase. Compared with the traditional retrogression and re-aging treatment, the retrogression and stress-ageing treatments increase the size of MPts, narrows the width of PFZ and discontinuous the GBPs of the studied Al-Zn-Mg-Cu alloy.

Abstract:The microstructure of as-cast V-5Cr-5Ti alloy during annealing was analyzed by XRD、OM、SEM and TEM. The results show，with increasing annealing temperature,V-5Cr-5Ti alloy secondary phase of as cast V-5Cr-5Ti alloy decompose, diffuse and aggregate. The dendritic phase made by lamellar secondary phase is turn into reunion phase made by acicular secondary phase. The shape of acicular secondary phase changes coarse- elongated - tubby over time. The lattice parameters of V-5Cr-5Ti alloy after 1100℃?h annealing is 0.30362 nm, Ti and interstitial (C, N, O etc.) are combined to form more stable secondary phase, reduce the expansion of V-5Cr-5Ti alloy lattice.There are three kinds of the secondary phase in V-5Cr-5Ti alloy after 1100℃?h annealing:1) Strip secondary phase, chemical formula can be expressed as V2(CO); 2) Acicular secondary phase, has FCC structure, the lattice parameter is 0.4193~0.4256nm; 3) Elliptical-shaped secondary phase, has FCC structure, the lattice parameter is 0.4203~0.4268nm; In the process of annealing, The dendritic phase decompose and diffuse firstly, then the alloy matrix will precipitate due to alloy element desolution and separate out the reunite phases, witch is the Characteristic of acicular secondary phase. Finally, the secondary phase is chromium-alloyed stabilized precipitations of titanium-vanadium oxycarbonitride with FCC structure, which chemical formula can be expressed as (TiV)(CON).

Abstract:This paper investigates the main mechanical properties of TC1 titanium alloy sheets with different thicknesses, and a useful function that can describe the mechanical properties reasonably through extensive practical application will be used. Meanwhile, planar anisotropies of above TC1 titanium alloy sheets were fully studied by Barlat''89 and Yld2000-2d yield functions with an aim of the influence M value on describing ability for distribution characteristics of material yield stress and anisotropy parameter and comparison of their performances on above titanium alloy sheets.

Abstract:Nonequilibrium molecular dynamics (NEMD) simulations are investigated to obtain an understanding of the effect of strains on the thermal conductivity of Ge thin films. The results show that the strains have an appreciable influence on the thermal conductivity of Ge thin films. The thermal conductivity decreases as the tensile strain increases and increases as the compressive strain increases. It is explained by the fact that the decrease of the phonons velocities and the surface reconstructions. Meanwhile, a theoretical calculation basing on Modified-Callaway model under different strains is performed to assess our NEMD simulation results. We find that the theoretical results closely match the molecular dynamics results. The theoretical analysis reveals that the contributions of the relaxation time on strains are very important to the thermal conductivity of Ge thin films.

Abstract:High strength and high conductivity Cu-Nb microcomposites were fabricated by accumulated bundling and drawing process. The crystal orientation and morphology of Cu-Nb materials were investigated by means of X-ray diffraction and scanning electron microscopy. The stress-strain curves and conductivity of samples at different HT condition were measured. It is indicated that recrystallization textures are formed after HT at 700℃. Chemical potential difference and atomic diffusion caused by serve plastic deformation are key factors of interface stability. And even intermediate HT at 700℃ will be benefit for the mechanical properties of Cu-Nb microcomposites. It is believed that low temperature adjustment could improve the plasticity and keep the strength.

Abstract:The fibrous porous metals as a noise control material was used in harsh environment which in the high temperature, strong vibration, high sound intensity, corrosion, etc. But the effects of porosity and wire diameter on sound absorption performance in different thickness were waiting for lucubrated. In this paper, fibrous porous metals which the thickness were from 1mm to 30mm were prepared by three kinds of sintering processing, loose sintering, compacting sintering, positioning sintering. The absorption coefficient was tested by double microphone impedance measurement tube of B&K Company in Denmark. The effects of the porosity and the wire diameter were studied systematic. The results shown that there was a different optimum range value of porosity with different thickness, for example, the zone of the thickness from 1mm to 3mm, the porosity in the range from 80% to 85%, and the thickness was 5mm, the porosity in the range from 85% to 90%, and the zone of the thickness from 10mm to 15mm, the porosity in the range from 90% to 94%, the sound absorption performance was the best at the frequency from 50Hz to 6400Hz, which was increased with thickness. When the wire diameter ≤3mm, the smaller the fiber diameter, the sound absorption performance was very good in the whole frequency, when the thickness from 3mm to 20mm, with the thickness increased, the sound absorption performance of the materials in thicker diameter was well gradually, the absorption peak was moved to low frequency, the sound absorption performance at high frequency was still kept very well, and when the wire diameter ≥20mm, the larger the fiber diameter, the sound absorption performance was very good in the whole frequency.

Abstract:Aluminum with a high B4C content are valuable as a neutron absorber for spent nuclear fule pool storage rack,welding of B4C/6061Al using conventional fusion methods degrades the joint properties due to solidification induced structure and chemical reactions. B4C/6061Al neutron absorbers were fabricated by powder metallurgy with the B4C volume fractions of 0 ~ 30%. Plates of 4 mm thickness and 30% B4C/6061Al neutron absorbers was prepared and successfully butt joined using friction stir welding (FSW). The weld displays the smooth appearance. The micro-mechanical properties in welded joints of FSW weld nugget (WZ), Thermo-mechanically affected zone (TMAZ), heat affected zone (HAZ) and base metal (BM) were investigated by nanoindentation method, and the tensile tests were carried out.Furthermore,the microstructure of indentation and fracture surface were characterized by scanning electron microscope. The results showed that in the same region, with the distance(d＜11 μm) of the interface between particle and matrix increased, the micro-area of hardness and elastic modulus decreased overall. After the micro-area equalization, different regions of hardness and elastic modulus from high to low were WZ, TMAZ, BM and HAZ. The pressure into the power recovery rate in WZ, TMAZ, HAZ and BM were 28.10%, 25.14%, 31.76% and 29.30%. The performance difference in the welding joint of different areas was caused by the different degree of plastic deformation and the thermal cycle in different area. A joint efficiency of 85.7% was realized under the experimental conditions, and the welded joint failed at HAZ.

Abstract:The hot compression tests for TA15 Titanium alloy were conducted at 0.001s-1~1s-1 strain rates and 750℃~ 1050℃temperatures.The effect of deformation temperature and strain rate on the flow stress was analyzed. According to the test results, the rise temperature on the deformation process was calculated, which is proportional to strain rate and strain. The maximum temperature rise 122.63℃ is produced In the low temperature and high strain rate of .Finally, considering the thermal effect leads to deformation temperature, based on Sellars-Tegart constitutive model, the constitutive model is established for the microstructure evolution of TA15 titanium alloy at hot deformation.

Abstract:We present a study of the growth and magnetic properties of Fe83Ga17 thin films prepared by the dc magnetron sputtering method, sputter deposited on Si(100) substrates for sputtering powers in the range 40W≤P≤80W. The structure and magnetic properties? of Fe83Ga17 thin films have been investigated by using X-ray diffraction analysis (XRD), scanning electron microscope (SEM)，physical property measurement system (PPMS) and magnetic force microscope (MFM). The results show that all samples exhibited a (110) disordered bcc structure, additional, the grain size of Fe83Ga17 thin films is about 40~70nm and the grain size slowly increases with increase in the sputtering power. The remanent magnetization Mr and the remanence ratio Mr/Ms tend to decrease slowly with increase in the sputtering power while the coercivity Hc and saturated magnetic field strength Hs go the opposite way. However, the changes in the saturation magnetization Ms are not so clear. The magnetic domain (MD) patterns showed the labyrinth structure and the domain size was increased with increase in the sputtering power.

Abstract:By in situ tension observed with SEM, the deformation of hydrides and the slip behavior were investigated for the N18 zircaloy, which had been charged hydrogen by electrolytic hydrogenation method. And the effects of hydrides on the tensile properties were discussed. The results show that, the deformation of zircaloy results from multiple slip and the hydrides can be deformed evidently with matrix. The sparse strip clusters are not able to block the slip band movement, even to change the slip direction. But the big and thick strip clusters can stop the slip movement, or change the direction. The hydrides can increase the tensile strength slightly and decrease the elongation greatly. But the N18 zircaloy with 623 ppm hydrogen still has 13.1% elongation, an acceptable ductility.

Abstract:Abstract: BiFeO3(BFO) and Sr1-xLaxFe12-xCoxO19（x=0~0.3）monolayer films and 2-2 BiFeO3 / Sr1-xLaxFe12-xCoxO19 stacked composite films were prepared on the P-type <100> Si-based substrates by magnetron sputtering at room temperature. The microstructure, surface morphology and magnetic properties of thin film samples were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and material properties of a comprehensive test system (PPMS).The results indicate that with the increase of x, the coercive force of Sr1-xLaxFe12-xCoxO19 monolayer first increase after small decreases, residual magnetism ratio unchanged at first and then increase, while the residual magnetization have been reduced. When the x = 0.3 the coercive force and the residual magnetism ratio reached a maximum value of 6165Oe and 0.69, and the residual magnetization reaches the minimum value of 50emu/cm3; The coercive force and residual magnetism ratio of the composite film decreases after the first increases, while the residual magnetization have been reduced. At x = 0.2 the coercive force and residual magnetism ratio reached a maximum value of 5333Oe and 0.73. When the x = 0.3 when the ratio of the coercive force and the residual magnetism ratio decreased significantly as 2151Oe and 0.4, the residual magnetization in this case is the minimum value of 19 emu/cm3.

Abstract:Site substations of Y and the super-cell systems of γ-TiAl doped with Y were investigated by the means of the first-principle plane-wace pseudopotential method based on density functual theory. The geometric and electronic structures, the formation energy, Mulliken and bond population of Ti2Al2, TiAl2Y, Ti3Al4Y, Ti7Al8Y as well as Ti15Al16Y were obtained. The results show that Y prefers to be a substitute for Ti in γ-TiAl alloy. The addition of Y increases both lattice distortion of γ-TiAl and forming ability of the doped lattice. Moreover, the proportion of covalent properties increases first and then desends with increasing Y doping concentration. Ti15Al16Y possesses the lowest proportion of covelent properties, improving the brittleness of γ-TiAl.

Abstract:Zr47–xCu46Al7Yx(x=3~8) bulk metallic glasses (BMGs) were prepared by injection in copper mould with arc melting. The effect of Y content on the glass-forming ability (GFA), microstructures, fractured surfaces and mechanical properties of the alloys were investigated by using X-ray diffraction (XRD), differential scanning calorimetry (DSC), scanning electron microscope (SEM), compression tests and hardness tests, respectively. Results show: Y content has evident effect on the GFA and mechanical properties, the BMGs with 4~7at%Y contents only contain amorphous phases and possess a larger supercooled liquid region ΔTx with value of 56~71K and a better reduced glass transition temperature Trg with value of 0.665~0.678, but very few crystalline phases appear on the BMGs with 3 and 8at%Y contents. The BMGs possess better mechanical properties with compression strength of 1803-1899MPa and Vickers hardness of 5.22~5.39GPa, the BMGs with the better GFA correspondingly possess the better mechanical properties. In compression test, the BMGs happen brittle fracture by pure elastic deformation way, and all fractured surfaced are flat and smooth with typical vein-like morphologies.

Abstract:Ni-P alloy coating on Titanium alloy was obtained by electroless plating method. The influence of annealing temperature on the adhesion of the Ni-P coating was investigated .Dynamic equation to describe the interface layers thickness, diffusion heat treatment temperature and holding time were established by SEM analysis. The product of the diffusion interface and the influence of different annealing temperature on the coating of thermal stress were studied by X-ray diffraction. The results showed that the Ni-P coatings were no diffusion layers when treated at 400℃ for 2 and 4 hours, and diffusion layers appeared when treated above 400℃. The dynamic equation, , can be obtained according to the relations of the thickness of the diffusion layer and the time and temperature of heat treatment. The thermal stress of coating increased significantly after heat treatment; the adhesion of the coating with heat treatment was much higher than that of without heat treatment. The best adhesion of the coating can be obtained when the heat treatments were at 400℃2h、400℃4h、500℃4h.

Abstract:Aiming at improving the electrochemical rate capability and cyclic performance of LiNi0.5Mn1.5O4，two step solid-state reaction was adopted to synthesize LiNi0.5Mn1.5O4-xFx（x=0, 0.05, 0.1, 0.15, 0.2）cathode materials.The effect of F-doped on the performance of LiNi0.5Mn1.5O4 was investigated. X-ray diffraction, scanning electron microscopy, the charging-discharging test, cyclic voltammetry tests, electrochemical impedance spectroscopy were employed to study their properties.The results showed both the doped and un-doped cathode materials were cubic spinel structure with clearly defined shape and uniform particle size distribution. For the cathode materials doped with 0.1F presents the best electrochemistry performance, at the charge-discharge rate of 0.1, 0.5, 1, 2 and 5C, its initial discharge specific capacity was 129.07, 123.59, 118.49, 114.49, 92.57mAh/g, respectively. When cycled at 1C rate, above 98.84% of its initial capacity can be retained after 30 cycles for LiNi0.5Mn1.5O3.9F0.1.

Abstract:The Nd60Fe20Co10Al10 bulk amorphous alloy was prepared by suction casting into the copper mould. The microstructure and magnetic property of the alloy during crystallization process were studied. The magnetic viscosity of this alloy during crystallization process was investigated by waiting time method. It was found that magnetic properties of the Nd60Fe20Co10Al10 bulk amorphous alloys annealed at temperature below 783 K had a slight change. However, after annealing at temperature higher than 783 K, values of the remanence (Mr), saturation magnetization (Ms) and intrinsic coercivity (iHc) decreased significantly. Furthermore, the alloy showed paramagnetic behavior after annealing at 803 K. When samples were annealed at 703 K and 753 K, the activation volume (Va) and activation diameter (Da) changed slightly, while the fluctuation field (Hf) showed a maximum at 703 K. It was due to the presence of a metastable phase. The relationship of parameters of magnetic viscosity and magnetic property of the Nd60Fe20Co10Al10 alloy was discussed.

Abstract:By means of first-principles calculating the formation enthalpy, binding energy and states density of γ′-Ni3Al and γ″-Ni3Nb phases, the influence of Nb doping on alloying behaviors of γ′-Ni3Al and γ″-Ni3Nb phases is investigated. Results showed that, in the molten of the γ′-Ni3Al and γ″-Ni3Nb phases, compared to γ″-Ni3Nb phase, the γ′-Ni3Al phase has a lower stability in the range of Nb doping quantity being less than 15.625(at%), but the γ″-Ni3Nb phase has a bigger stability in the range of the Nb doping quantity being more than 18.75(at%). Wherein, the γ′-Ni3Al and γ″-Ni3Nb phases have the close lattice parameters in the range of 15.452-16.34 (at%) of Nb doping, which is thought to be an essential condition of promoting γ′-Ni3Al → γ″-Ni3Nb coherent phases transformation. The difference of the states density in the Femi-level location increases obvious as the quantity of Nb doping is more than 18.75(at%), which enhances the stability of γ″-Ni3Nb phase. Moreover, the decomposition of the γ′-Ni3Al phase occurs at the same time the γ″-Ni3Nb phase growing, which may result in the disappearing of γ′-Ni3Al phase.

Abstract:Mo particle reinforced copper composites with Mo 2.5-10.8 vol% were prepared by Electron beam physical vapor deposition (EB-PVD), the microstructure, hardness and electrical resistivity were investigated. The results show that the Cu matrix is composed of columnar crystalline and the average grain size of Mo particle is 2.4-8.1nm; the columnar crystal width of copper matrix, hardness and electrical resistivity of the composites increase with the increase of the Mo content; the strengthening mechanism of the composites by EB-PVD is mainly the Orowan mechanism.

Abstract:Preform design of blade forging has been optimized by utilizing developed topology method in this study. The key techniques of 3D topology optimization include optimization strategy, optimization objectives, element addition and removal criterion, geometry model treatment are given in detail. To fulfill the objective of increased raw material utilizing rate and die-filling rate, a theoretical optimized preform has been obtained after a dozen optimization iterations based on the self-programmed code. Blade forging experiments are implemented to validate the formability of optimized preform form. Aerofoil section profiles extracted from actual forged blade by utilizing laser measure equipment are compared with that from the FE results. The preparation technology of optimized preform is also discussed. A satisfactory optimal result of preform design has been achieved by utilizing the topological method.

Abstract:Al-doped Ti3SiC2 ceramics were prepared by hot-pressing sintering, which were characterized and measured for oxidation resistance and microwave dielectric property by X-ray diffractometer, scanning electron microscope, energy dispersive spectroscopy and vector network analyzer, respectively. Results showed that the prepared ceramic with Al doping had higher mass fraction of Ti3SiC2, and that the as-prepared ceramic grains had the typical laminated appearance. Through the Al doping approach, the oxidation resistance of Ti3SiC2 ceramic at 1200℃ was efficiently improved, and its real component ε′ and imaginary component ε″ of permittivity were greatly increased, compared to undoped sample, which were 60.8 and 6.28 in average in the frequency range of 8.2-12.4GHz, respectively.

Abstract:This paper reports the use of micro-arc oxidation(MAO) to prepare porous oxide coatings containing Ca and P on the surface of titanium and large plastic deformed titanium. The surface morphology, hardness, film-substrate bonding force, fretting friction and wear properties and bioactivity of MAO coatings on titanium and large plastic deformed titanium were investigated. Results reveal that compared with the MAO coating of conventional titanium, pores on the MAO coating of large plastic deformed titanium are more uniformly and compactly distributed, with smaller micro-sized pores, which have larger quantity, higher porosity, smoother and more level surface , larger relative content of rutile TiO2, higher hardness value, stronger adhesion strength. The improvements were caused by the increasement of crystal defects (internal energy) due to the microstructure refinement of large plastic deformed titanium.

Abstract:In order to research the mechanism of nano TiO₂ doping effect on micro-arc oxidation coating formed on aluminum alloy, it was treated by using micro-arc oxidation in different concentration of nano TiO₂ electrolyte. Surface morphologies,Ti, Al,O and elements content, phase composition of micro-arc oxidation coating were analyzed by SEM, EDS and XRD. Thickness and hardness of micro-arc oxidation coating and surface charge of nano TiO₂ in electrolyte were measured. The doping modification model was established in this paper. The results show that the oxidation voltage were raised at initial stage, and then declined after 5minutes.The numbers and sizes of hole on oxidation coating surface decreased, formation efficiency and compactness of coating, and the hardness of surface porosity coating increased. The nano TiO₂ was distributed homogeneous on oxidation coating surface, and inhomogeneous on cross-section. Oxidation coating was mainly composed by γ-Al₂O₃, mullite and little Si phase.

Abstract:The microstructure in adiabatic shear band (ASB) of U-5.7Nb alloy deformed at high strain rate by a split Hopkinson pressure bar (SHPB) was investigated by means of OM, SEM, and TEM. The ASB with black etching color in U-5.7Nb has been observed, and its width was about 40 um. The evolution of microcracks in ASB led to the formation of the micro-feature which like equiaxed "broken grain" with the size of 2-5um in ASB. The nanometre-sized grain domains well below 5 nm are found in the core of ASB, and the orientations of single small grain domain differ completely, even within an area of 1 μm. Microhardness of the ASB is higher than that of the matrix, but elastic modulus of ASB is lower than that of the matrix. The different trends between microhardeness and elastic modulus are caused by the change of microstructure in ASB.

Abstract:The Ti/TiN/Zr/ZrN multilayer films were prepared on 1Cr17Ni2 stainless steel by vacuum arc deposition, and the morphologies, phase composition, bonding strength, polarization curve and electrochemical impedance spectroscopy (EIS) of the multilayer films were studied. The results show that the films are mainly composed of TiN and ZrN phases with a few metal Ti and Zr. The multielement interface of the Ti/TiN/Zr/ZrN multilayer films exhibite excellent and dense with a total thickness of 2-3 μm, and the grain size presents uniformity and fine. The bonding strength between the films and the substrate is higher than 70 N. The microhardness of the films is up to 2900 HV0.025. Compared to the uncoated 1Cr17Ni2, the multilayer films possesse higher corrosion potential, higher polarization resistance, larger capacitive reactance arc and lower corrosion current density.

Abstract:The impact mechanisms of the thermal effect of vacuum electron beam welding on the micro-hardness of AZ91D and AZ31B magnesium alloy weld were studied. The experiment results showed that the welding thermal effect exerts its influence on weld hardness differently for AZ91D and AZ31B magnesium alloy. Two factors affecting the micro-hardness of the weld should be included, which are the cooling rate after welding and the burning loss of alloying elements after the action of welding thermal effect. When the welding heat input is large, the main factor affecting the weld hardness of AZ91D magnesium alloy is the increase of strengthening phases because of the burning loss of Mg elements. A larger welding heat input induces more strengthening phases in weld and the weld hardness increases relatively. When the welding heat input is small, the main factor affecting the weld hardness of AZ31B magnesium alloy is the cooling rate after welding. The smaller welding heat input induces faster cooling and solidification rate after welding and then forming fine grains, so the weld hardness is relatively high.

Abstract:Ag-4wt%TiB2 electrical contact materials reinforced with different TiB2 particles were prepared by hot pressing, and the effect of TiB2 particle sizes on the micro-structure and properties of Ag-4wt%TiB2 electrical contact materials were studied. The microstructure and arc erosion morphology of Ag-4wt%TiB2 electrical contact materials were characterized by a scanning electron microscope and a confocal laser scanning microscope, and the relative density, hardness and electrical conductivity were tested as well. The results show that the hot pressing is favorable to improve the relative density of Ag-4wt%TiB2 electrical contact materials.With decrease of TiB2 particle size, the electrical conductivity constantly increases, while the hardness increases and then decreases. The fine and well distributed TiB2 particles are beneficial for the improvement of arc erosion resistance. The Ag-4wt%TiB2 contact material presents shallow erosion pits, large erosion area, and short arcing time.

Abstract:WC-12Co coatings were sprayed by HVOF with a composite mixture of microstructure and nanostructure powder. The thickness of the coatings are 0.5mm, 1mm, 2mm, 3mm and 4mm respectively.SEM and XRD were used to analyse the microstructure and phase composition of the coatings. Porosity of the coatings was also tested. Results show that thickness has little influence on surface microstrucure and roughness of the coating, on the contrary, thickness has great influence on section microstrucure. For coating which is thicker than 1mm, microstructure of the middle part of the coating is denser than the interfacial and the upper area, however, microstructure changes litte along the deposition direction for coating which is thinner than 1mm. There are few W2C and Co3W3C phase in the coating for thermal decomposition of WC, furthermore, more and more decompostion occurs with the increase of the coating thickness.

Abstract:Abstract: Hydrogenation can adjust state of microstructure of superplasticity of Ti-6Al-4V laser butt weld joint and improve the superplastic deformation uniformity of microstructure . The project adopped the treatment of hydrogenation study the deformation behavior of super-plasticity of Ti-6Al-4V laser butt weld joint. The project is the basic research that hydrogenation can improve the superplastic deformation uniformity of microstructureThe main research is that the content of hydrogen affected peak flow stress, welding plate extending rate, uniformity of microstructure . The results revealed that the peak flow stress enlarged with the increasing of the content of hydrogen, reduced with the rising of deformation temperature, enlarged with the increasing of strain rate; elongation of specimen rduced with the increasing of the content of hydrogen, enlarged with the rising of deformation temperature, reduced with the increasing of strain rate. The peak flow stress reaches a minimum 20.7MPA, weld plate maximum elongation reach to 312% in the situation of hydrogen content of 0.291% in the deformation temperature of 920 ℃, strain rate 10-4S-1. Ti-6Al-4V laser butt weld joint with hydrogen can under superplastic deformation without failure，In the initial strain rate of 10-3S-1 and 10-4S-1, the peak flow stress is less than 80MPA.

Abstract:An intermediate strength coarse grain γ-TiAl based alloy Ti-46Al-5Nb-1W(at.%) has been studied in this paper to assess the fatigue properties under different surface conditions both before and after thermal exposure. It has been found that although the majority of specimens were fatigued under condition of σmax <σ0.2 before thermal exposure, pre-yield crack initiation can still occur in coarse lamellar grains, especially in soft orientation. Improvement of the surface quality in the coarse grain alloy for better fatigue performance is found to be less effective in the coarse grain alloys than in the fine grain alloys. It has been also found that the embrittlement effects owing to oxygen release and ordered phase formation caused by thermal exposure were not particularly considerable. On the contrary, the fatigue performance was enhanced because of a long-term immersion of these specimens within warm air, within which residual stresses were releases and defects become less harmful. The degree to which the fatigue performance was enhanced is controlled by the surface quality. The coarse alloy exhibits a relatively low fatigue notch sensitivity factor, which is only 0.27 before exposure and 0.32 after exposure for a V-notch.

Abstract:How to improve the combines strength of bore and rim materials becomes most critical and practical problem for manufacting dual-alloys turbine disk. This research tried to address this issue. In this research, wrought superalloy GH4133B with equiaxed grains has been chosen as bore material and P/M superalloy FGH4096 with PPB nets has been chosen as rim material for dual-alloys turbine disk in present research. Electron beam welding was conducted on as-polished superalloys, and P/M-solidified-wrought (P/M-S-W) complex structure was obtained. Cylindrical compression specimens were machined from the central position of P/M-S-W complex structure. A series of isothermal compression tests were conducted on a thermo-simulation machine. Based on the compression results and the related analyses, plastic deformation and microstructure evolution of P/M-S-W complex structures have been investigated. This research has great effect on improving microstructure controlling theory and developing isothermal deformation technology for dual alloys.

Abstract:F-doped TiO2 have been prepared using tetrabutyl titanate，ammonia and hydrofluoric acid by solvoethermal method.The properties of the powders were characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM)，N2 adsorption-desorption isotherms (BET) and Fourier transform infrared (FT-IR). The photodegradation of methylene blue (MB) solution was used to evaluate the photocatalytic activity of the catalyst under UV and visible light irradiation. The results showed that the TiO2 was in the pure anatase phase, the fluorine atoms were mainly distributed on the surface of TiO2, the photocatalytic activity was increased by adding hydrofluoric acid, it can increased the surface area， improved the crystallinity of the anatase phase and enhanced the formation of free OH radicals.

Abstract:The friction and wear properties of TiAl alloy were measured using a ball-on-disc type tribometer under sliding against SiC counterpart in dry condition an different temperature (20℃，300℃ and 600℃). The relationship between temperature and wear rate, friction coefficient, and topography of wear mark as well as wear mechanism of TiAl alloy was discussed. The results shown that the wear loss of TiAl alloy increased with the rise of temperature, the wear mechanisms of TiAl alloy are grinding abrasion and grain-abrasion at 20℃, and the oxidation abrasion increased with an increase in temperature, especially at 600℃. However, the wear loss of SiC counterpart is obviously higher at 20℃ than that of 300℃ and 600℃, this is because the wear mechanisms of SiC counterpart translation from intergranular fracture to delamination abrasion with the increase of temperature.

Abstract:Graphene oxide (GO) was prepared by Hummers method, then a series of composites consisting of lanthanum doped titanium dioxide and graphene oxide （GO-La3 /TiO2）were in situ synthesized via citric acid chelating sol-gel step, and subsequently lanthanum doped titanium dioxide and graphene (rGO-La3 /TiO2) composite photocatalysts were obtained by sodium borohydride reduction method. The composite materials were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and photoluminescence (PL) spectroscopy technology. The influences of GO addition amount on the composites photocatalytic activity and the effects of composite photocatalysts mass on the methyl orange degradation rate were investigated, respectively. The results showed that the dispersion of lanthanum doped nanometer titanium dioxide on the graphene surface was improved effectively; the photocatalytic activity of rGO-La3 /TiO2 was obviously higher than that of La3 /TiO2, and the photocatalytic performance of rGO-La3 /TiO2 was effected greatly by the addition amount of GO; the optimum mass of composite photocatalysts was 0.10g to degradation of methyl orange.

Abstract:Micro-arc oxidation(MAO) and hydrothermal synthesis(HS) methods were used to prepare hydroxyapatite(HA)and anatase TiO₂ composite ceramic coating on the surface of conventional titanium and large plastic deformed titanium. The cellular compatibility of modified coating was evaluated by cytotoxicity experiment,cell proliferation assay and adhesion behavior of osteoblasts. The results demonstrated that: All samples were found to be noncytotoxic. Compared with the composite ceramic coating of conventional titanium, needle-like HA crystallization, which was closer to the Ca/P ratio of natural human bone, appeared on the surface of composite ceramic coating on large plastic deformed titanium. The composite ceramic coating of large plastic deformed titanium showed smoother and more level surface optimal and could better promote adhesion and spreading of osteoblasts.Optical density of osteoblasts cultured on the composite ceramic coating of large plastic deformed titanium was also significantly higher, and the two-tier growing structure of osteoblasts was more obvious with the progression of cultural time, which implied optimal cytocompatibility.

Abstract:Ultrafine-grained and nanocrystalline Ni coatings were prepared without/with using a flexible friction assisted electrodepositing technology from the addtives-free Watts bath. The microstructure, nanoindentation mechanical properties and dry friction and wear behaviour of the both deposits was comparatively studied. The results show that nanocrystalline Ni has much higher nanohardness, elastic modulus, the ratio of nanohardness to elastic modulus than that of ultrafine-grained Ni. The wear mechanism of these both dposits is mainly adhesive wear, but the tribological behavior is different due to the load discrepancy. At low load (1-3 N), nanocryatalline Ni has lower surface roughness and relative smoother worn surface, thus a relative lower coefficient of friction; at high load (5 N), nanocryatalline Ni has a relative coarse worn surface as a result of loose oxidation worn debris, thus a relative higher coefficient of friction. At all the testing load, nanocrystalline Ni has much smaller wear depth and wear volume, and much better wear resistance.

Abstract:Ultrafine WC-Ni cemented carbides were manufactured by coupled multi-physical fields activated technology to study the effect of the Ni content to sintering of WC-Ni cement carbide. It was found that multi-physical fields activated technology is an effective method to manufacture WC-Ni cemented carbide, and when the content of Ni increased, the micro pore diminished, and densification of the samples increased, but the particle size of WC increased. In addition, firstly, the Micro hardness increases quickly and then decrease with the increasing of the Ni content. At the same time, the fracture toughness (KIC) increase sharply to 8.5 MPa.m1/2 with the increase of the Ni content.

Abstract:The microstructure and composition of the liquid along the mushy zone of superalloy Inconel 718 that was directionally solidified at various solidification rates after heated under different remelting temperature have been investigated by scanning electron microscope (SEM) and energy dispersion analysis spectrometry (EDAX) techniques.The content of Nb and Mo in the interdendritic liquid along the mushy zone was presented. The liquid-density difference and relative Rayleigh number in the interdendritic liquid were calculated. It was found that when the remelting temperature increased from 1600℃ to1700℃, the segregation of Mo became more serious, the liquid-density difference became higher at the beginning solidification and the maximum relative Rayleigh number (Rar) increased greatly which indicated the tendency of thermal solutal fluid flow became larger and mushy zoen was more unstable.

Abstract:The N-doped carbon nanotube was prepared by high-temperature annealing, using the thiosemicarbazide as a nitrogen source. Then, the nitrogen-doped composite (NCNT/S) were outer coating by PEG. The structure and morphology of NCNT/S was detected by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and scanning electron microscope (SEM). The results show that: the nitrogen atoms effectively doped in carbon nanotubes by the high-temperature annealing method, and the carbon nanotube also kept the intrinsic morphology and structure. Electrochemical test results show that: the conductive properties of composites materials were enhanced by N-doped. The initial discharge capacity arrived to 882.5 mAh.g_-1, and it maintained 89.46% after 90 cycles. It further enhanced by PEG-coated, and the initial discharge capacity increased to 1109.7 mAh.g_-1, the discharge capacity retention ratio in 995.2 mAh.g_-1 after 90 cycles. The N-doped and PEG-coated can significantly improve the electrochemical properties of the CNT/S composite materials.