Abstract:Single crystalline wurzite GaN nanowires were synthesized through ammoniating Ga2O3/Ta films by RF magnetron sputtering. The products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), selected-area electron diffraction (SAED) and photoluminescence (PL). The results show that the nanowires have a hexagonal wurtzite structure with diameters ranging from 20 nm to 60 nm and lengths typically up to 10 μm. The PL spectrum exhibits a strong UV light emission at 363 nm. The growth mechanism of the crystalline GaN nanowires is discussed briefly

Abstract:Iridium alloys doped with approximate 4 at% Zr and 0.3 at% W alloying elements were fabricated for ultra-high temperature applications by powder metallurgy route. The phase compositions and microstructures of the composite powders and the alloy were investigated. It was found that Ir3Zr phase could not form and no mechanical alloying phenomenon occurred when the composite powder of Ir-ZrH2-W was prepared by high-energy ball milling even for 24 h, but it could be completely transmitted to Ir3Zr phase after calcinating at 1300 oC. The average grain size of the alloy prepared by the powder metallurgy route was 4-5 μm, and Ir3Zr phase was generated in-situ in Ir-based alloy during sintering process

Abstract:TiNbZr alloy was prepared by vacuum consumable arc melting furnace. The effects of solution and aging heat treatment on the microstructure and mechanical properties of this alloy were studied. The results show that ultimate tensile strength over 1000 MPa can be obtained when the alloy is solutioned for 1 h and then aged at 300 and 350 oC. α phase precipitation appears under the condition of the treatment of solution for 1 h, followed by aging at 400 oC and 450 oC. The aging time plays an important part in α phase precipitation. The ultimate tensile strength increases to 850 MPa and the elongation keeps around 11% when the alloy is aged at 400 ℃ for 9 h

Abstract:The microstructure changes brought by the addition of Nd element to AM60 magnesium alloy were studied, the precipitating phases were identified and their influences on the mechanical properties of alloys were investigated. Results show that Nd addition makes the refinement of microstructure of the AM60 alloy, and decreases the size of Mg17Al12 phase. Nd element takes a priority to react with Al element over Mg, Mn and Zn forming binary phase Al11Nd3 with high melting point. Certain content of Nd can increase tensile strength, yield strength and elongation of the alloy. But with too much addition, Nd would combine with more Al in matrix and decrease strengthening effect because Al11Nd3 phase would become coarsening. The mechanical property tests indicate that AM60-0.9Nd alloy has the best properties. Maximum tensile strength, maximum yield strength, maximum elongation are 230 MPa, 127 MPa and 14% respectively, increased by 28%, 48% and 250% respectively

Abstract:The titanium metals subjected to surface modification have good biocompatibility, bioactivity and low cell toxicity. It could induce apatite formation in vitro and bone bonding in vivo. However, the infection of implant is a serious problem for the clinic, so it is important to study the interaction of titanium metal with germs involving in the infection. The titanium metals subjected to anodic oxidation treatment (AO-Ti), acid-alkali treatment (AA-Ti) and alkali-heat treatment (AH-Ti) were used in this study. The germs of Gram-positive strain of Staphylococcus aureus (ATCC 25923) and Gram-negative strain of Escherichia coli（ATCC 25922）were cultured on these bioactive metals. The material surfaces were characterized by SEM and DSA. The effects of surface properties on the germs were evaluated by the investigation of the cell extrinsic shape, the proliferation of bacteria according to SEM and MTT observations. The results show that the Ti metals subjected to alkali-heat treatment (AH-Ti) and anodic oxidation treatment (AO-Ti) have good bacterial restrain properties. The titanium surface topography has great effect on the bacterial adhesion and proliferation on its surface

Abstract:The effects of Al4C3 on the microstructure and performances of AZ91D alloy are studied by using SEM, EDS, EDS and DTA. It is found that a small amount Al4C3 addition to AZ91D magnesium alloy leads to the α-Mg grain size obvious decreasing, causes the eutectic microstructure morphology marked change from the fully-divorced β eutectic phase and lamellar α+β eutectic structure to honeycomb partially-divorced α+β eutectic structure, and the β-phases diminution of size and tendency to dispersed distribution. Based on the analysis of EDS, DTA and the calculation of disregistry between Al4C3 and Mg, it is found that the Al4C3 particles can act as the heterogeneous nuclei. The strength properties are significantly improved due to the microstructural refinement of AZ91D alloy, but a little change of elongation percentage, and slight increase of corrosion resistance

Abstract:Nickel-based alloys with different contents of graphite were prepared by powder metallurgy method. High temperature oxidation resistance of these alloys was studied by high temperature test at 900 ℃ for 100 h in static air. Morphology of oxides was studied by SEM and their composition was analyzed by XRD. The result shows that the kinetic curves of oxidation for nickel-based alloys with lower content of graphite obey the parabolic law. The oxide films consist of Cr2O3 and NiCr2O4 when the alloy contains no graphite. The oxide film consists of Cr2O3 when the alloy contains 3% graphite. If graphite content increases to 6%, the oxidative decomposition of graphite leads to severe initial oxidation, and mass gain takes place significantly; the cavity after decomposition of graphite accelerates the process of oxidation reaction. The oxidation mechanism of the alloy has also been suggested by the phase composition analyses of oxide film

Abstract:XRD, TEM, SEM and OM techniques are used to investigate the cyclic oxidation behavior of Ni-20Cr alloys prepared by mechanical alloying (MA ) and conventional casting (CA ) at 1000 ℃ in air. It is found that a compact Cr2O3 scale is formed with a very good adhesion for the mechanically alloying Ni-20Cr alloy, even after a cyclic oxidation at 1000 ℃for 200 h, but a slight scale spallation is observed. For the conventional casting Ni-20Cr alloy, a complex scale of NiO/NiCr2O4 is formed, and a severe scale spallation is observed with a obvious mass decrease after a cyclic oxidation at 1000 ℃ for 200 h. The results show that the MA Ni-20Cr alloy exhibits a better cyclic oxidation resistance than the CA Ni-20Cr alloy owing to the fact that the grain refinement can significantly promote the formation of Cr2O3 scale and enhance the adhesion to the scale by the thermal stress reduction and release

Abstract:The fabrication method of sphericity nanoporous metal silver powders by nanosilver powders is described in the present paper. In this technique, a chemical deoxidize deposited way is used by taking N2H4.H2O as deoxidizer, the nanosilver powders are prepared by deoxidized silver ions which are protected by the dispersant and the home-made organic mixed solution. The silver ions concentration, the dispersant adding amount, and the organic mixed preparation are 10~40 g/L, 1.5~3 g/L, and 60 g/L, respectively, in the solution, then the reduction reaction is finished instantly with a nanosilver granularity of 10~20 nm. The nanosilver powders are conglomerated to sphericity nanoporous silver powders under controllable conditions, fast separated from the solution by deposited. The morphology was studied using a JEOL JSM-6400 FESEM, the results show that the sphericity nanoporous silver powders granularity is 40 ~80 μm. The specific surface area of the nanoporous silver powders is more than 16 m2/g measured using a Micromeritics ASAP 2020, and its pore channel has a very high penetration, different from the traditional microminiature silver powders.

Abstract:Micro-arc oxidation (MAO) coatings have been successfully prepared on Mg-Li alloys by micro-arc oxidation. The structure, phase composition and anti-corrosion behavior of MAO coatings are investigated by SEM, XRD, XPS, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). SEM images indicate the MAO coatings possess two layers “dense” and “loose layer”. Plenty of micropores exist on the surface of MAO coatings. The diameter of micropores ranges from 2 to 7 mm. XRD and XPS analysis reveal that MAO coatings are mainly composed of periclase MgO and amorphous phosphate compounds. Potentiodynamic polarization and electrochemical impedance spectroscopy results show that the corrosion resistance of Mg-Li alloys has been improved obviously after MAO treatment.

Abstract:The corrosion behavior has been studied on the three different coupled samples dipped in 5%NaCl solution. The coupled samples are Q235 steel with AM50 alloys, one without any coating, the other with cathodic E and cathodic electrophoretic coating on magnesium alloy. The surface morphologies of magnesium alloys with three different surface conditions have been observed in detail after dipped. The corrosion rates have been measured and the microstructure has been examined after ending the corrosion dip. The phenomena and law of galvanic corrosion have been explained by corrosion model. The results show that the cathodic electrophoretic coating could postpone the galvanic corrosion of magnesium alloy with steel effective and pre-silane treatment with much better protection. The affection area of galvanic corrosion did not increase with the dipping time. The corrosion developed more quickly along the coupled area than along the surface extending.

Abstract:The roles of Nb played in crystallization procedure of nano-crystal Nd2Fe14B permanent magnet were investigated by XRD, TEM and 3DAP. The results revealed that the addition of Nb improved the glass formation ability of the alloys and the thermal stability of the as-spun amorphous ribbons, as well as improving the optimum crystallization temperature. Nb atoms, together with more B atoms and some Fe atoms, had some enrichment in the as-spun ribbons, but few or no Nd atoms were found at these Nb-enriched regions. Nb-enriched phase hindered the growth of Nd2Fe14B grains, refined the microstructure and improved the magnetic properties

Abstract:The cavitation erosion of shape memory alloy Fe-14Mn-6Si-9Cr-5Ni-Nb-Ce in 3.5% NaCl solution was investigated by using an ultrasonic vibratory apparatus. Free corrosion potential and polarisation curves of the alloy in 3.5% NaCl solution under quiescent and cavitating condition were studied. The results show that Fe-14Mn-6Si-9Cr-5Ni-Nb-Ce alloy has excellent cavitation erosion resistance in 3.5% NaCl solution, cavitation erosion rate is 0.37 mg/h. Cavitation can shift free corrosion potential of the alloy in the active direction for about –65 mV. Corrosion current of Fe-14Mn-6Si-9Cr-5Ni-Nb-Ce alloy is very low in 3.5% NaCl solution under quiescent and cavitating condition, therefore, Fe-14Mn-6Si-9Cr-5Ni-Nb-Ce alloy shows high corrosion resistance. The relative contribution of electrochemical corrosion rate and pure mechanical erosion-induced corrosion rate to the overall cavitation eroson only amounts to 2.24%

Abstract:The Mg1-xScxNi (x=0, 0.01) hydrogen storage alloys were prepared by mechanical alloying. The XRD test results showed that the alloys were amorphous alloys. The XPS test results indicated that the addition of Sc weakened the degree of oxidation on the alloy surface, and increased the atom ratio of Ni/Mg at the alloy powders’ surface. The electrochemical test results showed that the addiction of Sc improved the electrochemical properties of the alloy electrodes. The discharge capacity, the cycle capacity retention rate S10, HRD200, the exchange current density I0 and the limited current density IL of Mg0.99Sc0.01Ni alloy electrodes were 10.5%, 14.7%, 30.4%, 202.7% and 77.8% higher than that of MgNi alloy electrodes’ , respectively

Abstract:The fracture characteristics of high cycle fatigue slick samples of FGH 95 powder superalloy was observed, and the fracture feature law was put forward. The fatigue crack expanding peculiarity was analyzed using fractography quantitative analysis, and the fatigue expanding life was also calculated. On the basis of above research work, the internal relation between crack expanding peculiarity and fracture characteristics was analyzed. For 120 high cycle fatigue slick samples, the relation between fracture feature parameter ac and test fatigue life Nf was studied through statistical and inductive method. There is rough linear relation between logac and logNf, all of the data under the same temperature and stress ration R distribute among a disrupt strap with a certain width, and there are a top limit and below limit for the disrupt strap, the top limit line is approximately parallel to the below limit line. The critical crack length ac maybe used to evaluated the fatigue life using the top limit and below limit equations.

Abstract:Stoichiometric and lithium-rich Li3+xV2(PO4)3 (x=0.02,0.04,0.05,0.06) for lithium batteries was prepared by a carbon-thermal reduction (CTR) process. The properties of the Li3+xV2(PO4)3 were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and electrochemical measurement. The results show that the samples have monoclinic structure, without any other phases in samples. The SEM images exhibit that the surface structure of the primary particles is clearly improved. The measurement of electrochemical performance shows that the cycle ability and the first discharge capacity are also improved with the doping of lithium

Abstract:By using diffusion couple made by inlaying, the forming rule of Ti/Cu diffusion-solution zone was researched with different anneal conditions. The microstructure was observed and analysed by means of backscattered electron and secondary electron image. The forming mechanism was researched in the views of diffusion, dissolve and crystalline. The results show that the formation of diffusion-solution zone comes from the solid phase diffusion, dissolve and crystalline of Ti and Cu at different diffusion temperatures for different times. The diffusion-solution zones with different numbers of layer, thickness and structure are formed almost in the Ti/Cu interphase at the same time; the Cu-Ti compound with a relatively lower percent content of Cu and Ti atom is firstly formed; one layer or several layers are formed on earth, which is determined by the concentration distribution of Cu in Ti and Ti in Cu. When the diffusion couple is heated at 700 ℃ for 100 h, the atom diffusion flow is the Cu diffusing into Ti, the Ti hardly diffusing into Cu. Consequently, the other five layers are formed on the Ti body except the Cu4Ti layer on the Cu filaments; the Cu2Ti and Cu3Ti2 as well as the Cu4Ti3 and CuTi phase layers grow with the opposite directions and intervein each other with bamboo shoot shape, showing relatively obvious floating and protruding, otherwise, the Cu4Ti and CuTi2 phase layer grows with a “plane pattern”

Abstract:The microstructure of W and Ti alloy prepared by sintering and infiltration has been studied. The formation mechanism of W-Ti solid solution is discussed and the electron density of W-Ti solid solution is calculated by means of the Thomas-Fermi-Dirac-Cheng phase diagram (TFDC). The results show that the substitutional solid solution of TixW1-x results from the W and Ti atoms diffusing into each other during sintering and infiltration at 1750 ℃. The hardness value range of this solid solution is 3350～5280 MPa (HV0.1). The electron density of W-Ti solid solution is 2.4851×1029 /m3 and the calculated lattice parameter is 0.3140 nm

Abstract:The formation enthalpies of medical Ti-based alloy are calculated by a modified Miedema model. The results show that the formation enthalpy is evidently reduced when the non-transition metal Al or Sn is added into the medical Ti-based alloy. The contribution of elastic enthalpy is bigger than that of chemical enthalpy in the Ti-Zr alloy systems

Abstract:Vanadium oxide thin films were deposited by reactive direct current facing targets magnetron sputtering, and then processed in oxygen ambience to fabricate phase transition vanadium oxide thin films. X-Ray Photoelectron Spectroscopy(XPS), X-Ray Diffraction(XRD) technique and Atom Force Microscope(AFM) were employed to study and analyze the phase composition, structure of crystalline units of the thin films and surface morphology. The resistance-temperature property was also measured. The results show that the phase composition of as-deposited thin film changed from V2O3 and VO to VO2 when annealing at 300 ℃; the grains on surface are incompact and it is useful for oxygen infiltration to oxidate VOx thin films. The structure of VO2 oxidated from V2O3 and VO is monoclinic rutile structure processed between 300~320 ℃, the magnitude of metal-semiconductor transition increases to 2 with increasing of VO2 in thin films. All the results reveal that metal-semiconductor transition vanadium oxide thin films can be obtained by reactive direct current facing targets magnetron sputtering at low thermal processed temperature.

Abstract:Numerical simulation based on the phase field method is developed to describe the solidification process of pure material in a forced convection. The effects of forced convection, undercooling, coupling parameter and anisotropy on the dendritic growth are investigated. These results indicate that the crystal grow exhibits an asymmetrical dendritic in a forced convection. The upstream arm tip growth is promoted and inhibited on the downstream arm, while restrained for the perpendicular arm. With the increase of undercooling, coupling parameter and anisotropy, the dendritic arm growth velocities increase in the three different directions

Abstract:The titanium anode with sandwich coating structure was prepared by a sol-gel method. The anode was composed of three layers by firstly the oxide based layer coated with Ti70%-Ru30% on the titanium substrate, and then the inter-layer coated with Ir70%-Ta30%, the surface layer coated with Ti70%-Ru30%. The physical and electrochemical properties of the titanium anode with sandwich structure were studied by XRD, electrode potential, polarization curve, cyclic voltammetry and accelerated life tests. The results showed that the anode coating is composed mainly of rutile phases (Ti, Ru)O2, IrO2 and amorphous Ta2O5. The titanium anode has excellent electro-catalysis activities for both chlorine evolution and oxygen evolution. In the electrochemical conditions for chlorine evolution, the anode can keep better potential stabilities, and also shows a strong anticorrosive property for electrolyzing at high current density and in the high acidity. As the result, the titanium anode act as a good anode for both chlorine evolution and oxygen evolution

Abstract:The kinetics of hydrogen absorption for Ti600 alloy is studied at different initial hydrogen pressures using a constant volume method. The microstructure of hydrogenated Ti600 alloy at different hydrogen contents is observed. It is found that the shape, size, distribution and ratio between primary α phase and β phase change and the microstructure of hydrogenated Ti600 alloy and the phase boundary become ambiguous. The hydrogen absorption process represents only the second stage for the Ti600 alloy during hydrogenating at 750 ℃. The hydrogenating reaction represents multilevel reaction with the Avrami index of n>1 for the initial stage. The Avrami indices reach 1 after hydrogen absorption for 200 s, which illustrate that the rate limit of hydrogenating reaction is due to the diffusion of hydrogen in alloy

Abstract:In order to improve the properties and to prepare Zr-Ti-V alloy, V was partially substituted with Ti in ZrV2 alloy. The microstructure, the initial activation and dynamic performances of hydrogen absorption of the alloy are studied. It was found that the Zr-Ti-V alloy has a low activation temperature to absorb hydrogen fast and a good anti-powder capability due to the composite structure consisting of columnar crystals and small equiaxed crystals. The kinetic curves of hydrogen absorption exhibit dual-slope characteristics with a critical temperature Tc of 573 K to 673 K. When the temperature was below Tc, the hydrogen absorption rate is controlled by the phase transition rate, from large to small with time increasing; and when the temperature was above Tc, the hydrogen absorption rate turns from large to small with time increasing, controlled by the surface reaction process

Abstract:LiNi1/3Co1/3Mn1/3O2 and LiNi3/8Co1/4Mn3/8O2 nanofibers as cathode materials for lithium-ion batteries are successfully prepared from sol precursors by using electrospun method. The morphology, crystal structure and electrochemical behaviors are characterized by atomic force microscopy (AFM), X-ray diffraction (XRD) and charge-discharge experiments. The results show that the nanofibers possessed typical layer-structure and the average diameter is in the range of 150-200 nm. Both the initial discharge capacities of LiNi1/3Co1/3Mn1/3O2 and LiNi3/8Co1/4Mn3/8O2 nanofibers are over 170 mAh·g-1 and the capacity retention rates are over 90% up to 50 cycles

Abstract:The solubility of hydrogen in Ti-60 alloy and the effect of hydrogen on the microstructure, (α+β)/β transformation and the mechanical properties of Ti-60 alloy at high temperature have been investigated. The results show that the solution heat of hydrogen in Ti-60 titanium alloy △H is found to be –41.9 kJ/mol. And the volume fraction of primary α and the (α+β)/β transformation temperature is continuously decreased with increasing the hydrogen contents. The results also indicate that the yield strength at high temperature is also continuously decreased with hydrogen concentration, and the minimum yield strength occurs at a concentration corresponding to the (α+β)/β transition

Abstract:Fe81Ga19 alloy ribbons were prepared by melt-spinning. The phase structure and magnetostriction of ribbon samples were investigated by XRD and M-TG. The results show that the matrix of Fe81Ga19 ribbons was disordered Fe(Ga) solid solution, accompanied with a small amount of the second phase maintaining an unsymmetrical DO3 structure. The [100] preferred orientation was formed along the thickness direction. The maximum magnetostricton of –1830×10-6 was obtained when the magnetic field was applied normal to the ribbon plane. The shape anisotropy of ribbons, the unsymmetrical DO3 structure and the [100] preferred orientation are suggested to be responsible for the giant magnetostriction.

Abstract:Titanium oxide nanotube arrays were fabricated from a pure titanium foil with invariable anodizing voltage. CdS nanoparticles were then deposited upon the TiO2 nanotube arrays by electrochemical deposition method. And it was used to degrade the methyl orange. Results showed that CdS nanoparticals were evenly distributed upon the surface of the nanotube arrays and the doped nanotube arrays has better photocatalytic properties. The degradation of the methyl orange increases from 57.1% to 76.4% and the removal of the COD increases from 49% to 70.6% after 2 hours of irradiation

Abstract:Colloidal silver nanoparticles were synthesized respectively in three water-in-oil microemulsions, i.e., the microemulsion composed of SDS, cyclohexane, isoamylalcohol and water, the microemulsion composed of AOT, cyclohexane and water as well as the microemulsion composed of AOT, dodecane and water. The UV-Vis absorption spectroscopy was used for confirming the formation of silver nanoparticles, and the TEM was also used for elucidating the structure of resultant particles. The UV-Vis spectra show that the maxima of absorption peaks are at 400 nm, 428 nm and 435 nm, respectively. The UV-Vis spectrum is narrow with a high absorption density in SDS microemulsion. However, the silver particles formed in AOT-dodecane-water microemulsion have the broadest plasmon peak and the lowest absorption density. The TEM images confirm that the nanoparticles are all spherical with mean diameters of 6.46 nm, 4.03 nm, and 1.78 nm, respectively. There are not agglomerated particles in the three microemulsions. The growth mechanism of spherical silver particles is thought to be that the spherical reverse micelles in microemulsions offer a special microscopic template for the formation of silver namoparticles, and thus there is a relation between the droplet size and the radii of the formed particles. However, the size and morphology of the particles do not directly follow the shape and size of the microemulsion droplets due to the collision and coalescence. That is to say, the final silver nanoparticles are not perfectly monodisperse and have a breadth in size distribution

Abstract:The microstructure, the thermal tensile behaviors and the gas bulging forming formability of AZ31B Magnesium Alloy were investigated by thermal uniaxial tensile，gas bulging forming，optical microstructural observation and SEM observation. The results show that in the condition of 425 ℃, with a deformation rate of 1.0×10-3 ~ 6.6×10-5 s-1, a flow stress of 4~12 MPa, and an elongation of 200 %~327 %, the extrusion + hot/cold rolled magnesium alloy shows a good superplasticity. The AZ31B magnesium alloy shows a better formability at 425 ℃, 1.0×10-3 s-1 with a bulging height of more than 24 mm and H/r>0.80

Abstract:The CoFe ferromagnetic film with substrate/seed Ta (5 nm)/Co75Fe25 (5 nm)/Cap Ta (8 nm) was prepared by using UHV magnetron sputtering. The Influence of Ga+ irradiation on the microstructure and the magnetic properties of CoFe film were investigated by means of transmission electron microscope (TEM), selected electronic diffraction (SAED) and X-ray diffraction (XRD). The concentration profiles for Ga, Ta in the film after irradiation were also simulated by SRIM2003. The results show that the coercivity and microstructure of the film vary slightly after irradiation at low dose (less than 1×1013 ion·cm-2). With increasing of Ga+ ion dose, the coercivity decreases, the grain grows and the degree of <111> texture weakens. At high dose with 1×1015 ion·cm-2, noncrystalline appears in the CoFe film due to the presence of large atoms such as Ta and Ga and the existence of large amount of vacancies resulting in the film non-magnetizaton

Abstract:The effects of grain size on the lattice distortion, Fermi energy and Fermi velocity of nanocrystalline zirconium are investigated in this paper. Further more, the relation of the grain sizes with the lattice distortion, Fermi energy and Fermi velocity is founded. We have calculated the rate of lattice distortion and the value of Fermi energy and Fermi velocity. These results show that the lattice distortion of nanocrystalline zirconium is expanded. The lattice distortion increases with the grain size decreasing, while the values of Fermi energy and Fermi velocity increase with the grain size increasing

Abstract:The microstructure and mechanical property of forming parts by electron beam selective melting (EBSM) for ELI Ti-5Al-2.5Sn metal powder were investigated by means of optical microstructure and SEM, and universal mechanical testing machine. The results indicate that the density, the elongation and the room temperature strength of the forming parts are improved effectively according to zigzag scanning way with a vacuum of 3.0×10-2 to 5.0×10-2 Pa and a current of 2.0 to 3.0 mA,. The relative density, the tensile strength and the elongation are 97%, 740 MPa and 8%, respectively, close to the properties of forging parts, due to the transit liquid phase from the electron beam high energy utilization during sintering. Meanwhile, the cleaned surfaces of powders in vacuum improve the sintering actively. A rapid condensation process makes forming fine grains easy, while the increase of density and the refinement of grains are helpful to improve the mechanical properties of parts.

Abstract:The mechanical properties and texture evolution of AZ31 Mg alloy extruded at different die temperatures are investigated in this paper. It is found that the grains of alloy are refined after extrusion. The tensile strength and yield strength are significantly enhanced, but the elongation is not increased notablely. The tensile strength, yield strength and elongation of the sample extruded at 20 ℃ are 322 MPa, 233 MPa and 21%, respectively. The frequencies of high angle grain boundaries of the as-extruded samples are raised with increasing the extrusion temperatures, which indicates that the dynamic recrystallization is more and more sufficient. The basal ring type texture has been formed in the as-extruded samples, and a significant decrease in the intensity of basal ring type texture is detected. Our study reveals that the mechanical properties of AZ31 Mg alloy are not only related with the average grain size, but also with the texture.

Abstract:A method to determine preferred orientation of Ni-base single crystal superalloys AM3 is presented by use of X-ray diffractometer. By rotating a sample along its surface axis during θ-scanning process to ensure the normal axis of the crystal plane to across the diffraction plane multiply, the relationship between the crystal plan and the surface is obtained. The credibility is discussed by comparing the results of calculation and experiments. The identification of single crystal superalloys and dispersion degree of crystal orientation are elucidated. It is found that this method is simple and accurate for identifying single crystal superalloys

Abstract:The ZrW2O8 thin film of negative thermal expansion (NTE), as a novel functional material, has various potential applications in optics, microelectronics and micro-machine. The ZrW2O8 thin films were deposited on different substrates by RF magnetron sputtering with pure ZrW2O8 ceramic as target. The performance of target and the effects of post-deposition annealing temperature, atmosphere and substrate on the microstructure and morphology of the ZrW2O8 thin films were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results indicate that the target is compact and composed of pure ZrW2O8. The as-deposited ZrW2O8 film shows an amorphous phase. The ZrW2O8 film with preferred orientation can be prepared in oxygen atmosphere by annealing at 730 ℃, the trigonal ZrW2O8 film can be prepared by annealing at 750 ℃, and the cubic ZrW2O8 film can be prepared in a sealed cell at 1200 ℃, and the negative thermal expansion coefficient of the resulting cubic ZrW2O8 film is –14.47×10-6 K-1 in the temperature range from 15 ℃ to 700 ℃. With the increase of annealing temperature, some holes and deficiencies appear in the surface of films

Abstract:The resistance corrosion of zircaloy-4 by a shot peening treatment in autoclave steam at 673 K has been discussed with the oxide film component, topography, surface roughness, grain size and stress distribution according to XRD, SEM, AFM in this paper. It is found that the grain size decreases and the resistance corrosion is improved after the shot peening treatment for the zircaloy-4 alloy.

Abstract:The Ni-W and Ni-Co-W alloys have been electrodeposited on copper substrates from a citrate bath. The effects of pH values on the microstructure, soft magnetic properties and mechanical behaviors of the electrodeposited alloys have been investigated by XRD, SEM, EDX, VSM and Vickers microhardness measurements. The results show that the pH value affects the microstructure of both of the alloys. The microstructure of the alloys shows an amorphous structure if the pH value is less than 9, and a nanocrystalline structure with average grain size of 5 nm at the pH value of 9. The Vickers microhardness of Ni-Co-W electrodeposits reaches 10.5 GPa in the case of nanocrystalline structure. The coercivity reaches the minimum of 23×79.6 A/m when the pH value is 6. The soft magnetic properties and microhardness of electrodeposited Ni-W alloys are improved by Co adding

Abstract:Titanium bulkheads are widely used in the aviation and aerospace industry. This kind of parts are very complex, and meet high requirements for dimensional precision and the stabilization of inner quality. Some defects would be produced during the forming process, such as unfilling, overlapping, and the disturbance of forging flow line. In this paper, the effects of billet optimization and loading conditions on the forming quality during titanium alloy bulkhead isothermal closed-die forming process have been investigated, based on the rigid-viscoplastic finite element code, DEFORM-3D. The results show that the filling of die cavity can be effectively improved by using the billet with unequal thickness, which is obtained by the analysis of material flow, as a result, the dimensional precision can be satisfied for these parts. The local loading can make the deformation more uniform and eliminate the defects caused by bad material flow. The results obtained could provide a guide for proper loading scheme determining bulkhead forming

Abstract:The thermal stability of Ti14, a new typical α+Ti2Cu burn resistant alloy, after conventional forging and semi-solid forging (SSF) were investigated. The results revealed that under the condition of thermal exposure time no more than 150 h, Ti14 alloy after SSF had higher tensile strength than that of conventional one and the plasticity of the two forging state was similar. Up to 200 h, these two states alloy had similar thermal stability. The Ti2Cu particles distributed in grains uniformly after conventional forging; While in the process of SSF, Ti2Cu phases melted and precipitated on the grain boundaries as banding precipitations during cooling, which formed coarse dimples and few cleavages in microfracture, leading to the change of thermal stability

Abstract:Ce doped SrHfO3 nano-powders are synthesized by sol-gel process. The effects of pH value and calcining temperature for precursor and different Ce contents on the luminescence characteristic of specimen are studied. XRD, TG-DTA and SEM are employed to analyze the phase change and the characteristics of specimen. Results show that the powders have an uniform granularity with a dimension of about 50 nm, and good dispensability and polygonal morphology when calcined at 900 ℃ for 2 h and the sol pH value is controlled at 2.8. The maximum light band intensity appears if dopping 1.5% Ce (molar fraction). There is a broad band spectrum from 200 nm to 340 nm in the excitation spectra for the 385 nm light, peaking at 218 nm, 242 nm and 308 nm. There are three emission bands in the emission spectra excited by the 218 nm light, peaking at 380 nm, 487 nm and 526 nm. Only one emission band appears in the emission spectra excited by the 242 nm light and the 308 nm light. respectively, peaking at 393 nm and 403 nm. But The relative intensity of the first emission lights is stronger than the others due to the different transition probabilities for the electron transitions between different energy levels in SrHfO3:Ce

Abstract:Recently, researches have revealed that the granular jamming and glass-transition of amorphous matter, which seems to be out of the picture, may be intimately related to each other due to the strong analogies between these two systems. The progresses on the characteristics of granular jamming and the descriptions of amorphous structure, and the connectivity between the granular jamming and glass-transition are presented and shown, and the potential scientific interests are introduced in this paper