Abstract:The MgB2 wires were prepared by in-situ Powder-in-Tube (PIT) method with Nb/Cu compounds tube as the sheath and then were heat treated at various temperatures for 2 h in flowing argon. The resistivity (R-T), magnetic moment (M-T), transport critical current (Ic-B) and magneto optical (MO) properties of MgB2 wires were analyzed. The results show that there is a diffusion layer between MgB2 superconducting core and Nb barrier layer when the heat-treatment temperature is higher than 750 °C, and this diffusion layer obstructs the current transfer into MgB2 superconductor core from the Cu sheath. This indicates that the best heat-treatment temperature for the MgB2 wires with Nb as the barrier layer should be lower than 750 °C

Abstract:Four kinds of PbO2 electrodes were prepared by electrochemical deposition and three of them were doped by Fe, Ni and Ag, respectively. The characters of the electrodes were analyzed by SEM, XRD, accelerated life tests, and linear scanning voltammetry. The results show that the electrode surfaces are covered by quadrangular β-PbO2 crystals. The average grain sizes of the undoped PbO2 electrode and Ni-doped PbO2 electrode are similar and smaller than that of the Fe-doped PbO2 and Ag-doped PbO2 electrodes. The Fe-doped PbO2 electrode has the longest accelerated test life due to its dense surface. The LSV tests show that the Ni-doped PbO2 electrode possesses the highest oxygen evolution potential. From the phenol electrolysis, the Ni-doped PbO2 electrode demonstrated the best performance in COD removal efficiency, average current efficiency, and energy consumption

Abstract:A series of Co-free La1.8Ti0.2MgNi9-xAlx (x=0, 0.1, 0.2, 0.3, 0.4) hydrogen storage alloys were prepared by magnetic levitation melting under Ar atmosphere. The effects of partially substituting Al for Ni on the structure and hydrogen storage properties of the alloys were investigated. For the La1.8Ti0.2MgNi9-xAlx (x=0, 0.1, 0.2, 0.3, 0.4) alloys, LaMg2Ni9 phase is contained in all samples. when Al content x≥0.1, La(Ni, Al)5 phase replaces LaNi5 phase, LaNi3 phase disappears and LaNi2 phase appears. The enthalpies of the test alloys are close to –30.6 kJ/molH2 of the LaNi5 compound. Al substitution for Ni favors the improvement of discharge capacity, cycling stability and electrochemical kinetics. The optimum alloy is found to be La1.8Ti0.2MgNi8.7Al0.3 alloy, with the effective hydrogen storage capacity of 1.32 wt% (at 30 °C), the maximum discharge capacity of 340 mAh/g, the HRD1400 of 79.8% and the discharge capacity retention of 60% after 100 charging/discharging cycles

Abstract:The electroactive lithium vanadium phosphate, monoclinic Li3V2(PO4)3 [space group 14(P21/n)] has been synthesized by a solution route. The microstructure and electrochemical properties of the samples were characterized through combination of X-ray diffraction and galvanostatical discharge/discharge. Preliminary electrochemical evaluation indicates that this phosphate undergoes reversible lithium insertion reactions at average potentials of 1.81 and 3.77 V, and a complex series of two-phase transitions were observed during lithium extraction and insertion in the voltage range of 1.5~4.3 V. Constant current cycling conducted at C/5 and in the voltage range of 1.5~3.0 V is indicative of the longer term stability of the lithium insertion reactions evidenced by minimal capacity fade over the first 50 charge-discharge cycles. Therefore Li3V2(PO4)3 maybe used as both cathode and anode for fabrication of a symmetric lithium-ion battery, and the lithium insertion in the voltage region of 1.5~3.0 V could serve as a built-in overdischarge safety valve

Abstract:Au-Pd alloys doped with Zr, Mo and Y, respectively, were prepared in a vacuum high frequency melting furnace. The effects of rare metal doping on Microstructure and mechanical, electrical properties of the binary alloy was investigated. X-ray diffractometer and metallographic microscopy were employed to detect the microstructures. Electric bridge and eddy current conductive instrument were employed to test the electrical resistivity and the mechanical properties of alloys were tested by AG-X100KN type tensile testing machine. The results show that adding rare metal elements into Au-Pd system could refine microstructure effectively, increase the melting point, density and electrical resistivity of the alloy, and improve mechanical properties, but the processing property of the alloy is decreased

Abstract:The influence of the added KF concentration in the 6 mol/L KOH electrolyte on the electrochemical performances of the commercial AB5-type hydrogen storage alloy was investigated. The cycle life and high-rate performance of the commercial AB5-type hydrogen storage alloy can be improved by adding KF to the electrolyte. The analyses of XRD, SEM and SEI show that the formation of LaF3 in KF-added electrode can obviously decrease the corrosion of the metal hydride electrode compared with that of the KF-free electrode which prevents the dropping of the hydrogen evolution reaction voltage of the electrode and results in the improvement of electrochemical dynamics of the electrode

Abstract:In order to get high-precision TC4 alloy rod during the three-roll tandem rolling process, the spread of rod has been studied. A numerical simulation project was designed by an orthogonal experiment optimization design method. On the FEM software platform of Marc, the influence of rolling process parameters, including the rolling temperature, the rolling velocity, the inscribed circle of pass, the diameter of roller, and the friction coefficient between roller and rod, on the spread was investigated. Moreover, the effect order of above parameters was analyzed. On this basis, the spread model for TC4 alloy rod during three-roll rolling was established. The experiment was done on the self-developed three-roll mill of eight passes with a flat triangle-round sequence. The calculated results of spread model are in good agreement with the on-site data

Abstract:The microstructure, defect characteristics, and mechanical properties of electron beam welded (EBW) tantalum-to-stainless steel joints were investigated. Joint formation was influenced by the position of the EBW heat source. with a well-formed joint was obtained when the heat source was deviated by 0.2 mm towards the stainless steel. The weld is composed of fine dendrites with high elemental Fe content and homogenously-dispersed ε (Fe2Ta) and μ (FeTa or Fe7Ta6) phases. However, ε and μ phases formed at the tantalum fusion line had lamellar distribution and micro-cracks are easily formed in this region under welding stress. Although the weld zone has high hardness, the poor deformation compatibility of the fusion line at the tantalum side and the existence of crack sources lead to fracturing during the tensile test. The tensile strength of the joints was found to be low, 255 MPa

Abstract:The cast microstructure of a new difficult-to-deform superalloy эк151, was observed by high resolution field emission scanning electron microscope. The effects of elements on the thermodynamic equilibrium phases were studied by Thermo-Calc software. The results show that there is serious segregation of Mo, Nb and Ti during the solidification, which promotes γ′+γ eutectic. The main precipitates of эк151 alloy are a large fraction of cubic γ′, some carbides, borides and μ phase. Higher Cr, Mo, Nb and Ti contents can improve the primary and final melting points. The contents of Al, Ti and Nb can influence the precipitation temperature and mass fraction of γ' phase. Contents of Cr and Mo promote precipitation of M23C6 and M6C respectively. Furthermore, the increment of Cr, Mo and W content leads to more precipitation of μ phase

Abstract:The variation of band structure, density of states, charge density and atomic populations for the α-titanium with hydrogen were calculated with help of the first principle method and the calculation model of α-titanium crystal. The calculated results show that the hydrogen affects the symmetry of band structure and the aberration of band structure resulting from hydrogen ion; the covalent bond of titanium-hydrogen forms as the orbit intertexture between the s orbit of hydrogen with the p and d orbits of α-titanium with the increasing of hydrogen content; the electron zone of intercommunity forms as the great change of charge density around hydrogen; the smaller the distance from hydrogen, the more the charge transfer and the stronger the positive electricity of α-titanium, and the repulsion strengthens and the combination between α-titanium decreases at the same charge transfer of α-titanium in the same zone

Abstract:The microstructure and mechanical properties of the ZM61 alloy (Mg-6Zn-1Mn) with different Sn content were researched by optical microscope (OM), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), X-ray diffraction (XRD) and tensile tests. The existence form and acting mechanism of Sn element in ZM61 alloy and the influence of Sn content on microstructure and mechanical properties were investigated. The results show that the addition of Sn can improve the casting fluidity and the formation of the dispersed Mg2Sn particles can refine the MgZn phase to improve the microstructure and the mechanical properties of ZM61 alloy. The ZM61-4Sn alloy with double aging treatment has the best mechanical properties, with tensile strength of 374 MPa, yield strength of 358 MPa and elongation of 4.6%. However the addition of Sn cannot change the fracture behavior of ZM61 alloy while the coarse Mg2Sn phase can become crack source during fracture to decrease the plasticity. Therefore, Sn content should not be too high, no more than 4%.

Abstract:Isothermal compression of the TC11 titanium alloy was conducted on a Gleebe-1500D hot-simulator at the deformation temperature ranging from 960 to 1050 °C and the strain rate ranging from 0.01 to 10 s-1. The influence of deformation temperature and strain rate on the stress was studied according to true stress-true strain curves, and the constitutive equations of TC11 titanium alloy during hot deformation were established based on hyperbolic sine equations of Arrhenius type. Error analyses show that the established constitutive equations are coincident with experimental data well, and they provide a theory basis for the forging technique of TC11 titanium alloy

Abstract:Aging heat treatment was applied to the Austeinitic NiTi shape memory alloy at 300 and 500 °C, and two typical microstructures with grainy precipitation phase and acicular precipitation phase were obtained, respectively. Static and dynamic mechanical property testing were conducted for both the samples with different morphologies of precipitation. Results indicate that under static tension loading, the strain-induced martensite transformation of the both samples has an obvious strain rate effect. The initial stress for strain-induced martensite transformation of samples with grainy precipitation is higher than that of samples with acicular precipitation, while samples with acicular precipitation phase show better?plasticity and higher flow stress of plastic deformation. Under static compression loading, the two kinds of samples exhibit similar mechanical behaviors. Under dynamic loading, the samples with acicular precipitation manifest much higher yielding strength, indicating a better strain rate hardening effect. However, the plastic deformation stage of marstensite transformation for samples with acicular precipitation displays more evident strain rate hardening effect, resulting in close failure strength with that of the other samples. The corresponding mechanism was also discussed

Abstract:The deformation behavior and microstructure evolution after isothermal near β deformation of TA15 titanium alloy with initially equiaxed microstructure were investigated by compression tests. The effects of deformation temperature, strain and strain rate on the deformation behavior and microstructure transformation were quantitatively characterized through metallographs analysis. Results show that dynamic recrystallization is suppressed and dynamic recovery is promoted with the deformation temperature increasing or the strain rate decreasing. Otherwise dynamic recrystallization is promoted and dynamic recovery is suppressed with the deformation temperature decreasing or the strain rate increasing. Deformation temperature is the primary factor influencing the volume fraction, the size and the aspect of equiaxed α. Increasing strain rate has little effect on the refinement of equiaxed α. The empirical model was developed to describe the relationship between deformation temperature and the volume fraction as well as the size of equiaxed α in the near β temperature range. The research results can provide a guide for process optimization and control of isothermal near β deformation of TA15 titanium alloy

Abstract:A new composite extrusion method of Mg alloys was proposed which combined extrusion and one-time shear (ES). ES devices suitable for the thermal simulation instrument Gleeble1500D were designed and made and the theoretical simulation experiments were conducted. ES thermal-mechanical coupled finite element models were established based on the commercial DEFORMTM-3D software for FE simulation. The strain rate, extrusion force and stress-strain of the billet were studied during the deformation process. A new recrystallization mode has been discovered, which is different from the traditional recrystallization process and known as the “double-stage dynamic recrystallization”. In the extrusion stage, the accumulation strain value is smaller, and a little dynamic recrystallization happens. However, the equivalent strain rate of magnesium alloy billets after one-time shear rises rapidly, and the second phase of more dynamic recrystallization occurs. Microstructures of magnesium alloy billets are gradually refined after two phases dynamic recrystallization

Abstract:The hydrogen storage properties of LaNixMn0.26Aly alloys were investigated. Results show that when y=0.13, the lattice parameters (a and c) and the lattice volume V are increased, the absorption plateau pressure is slightly decreased, the desorption plateau pressure is almost the same and the hysteresis factor is improved, while the hydrogen intake capacity is impaired, and the stability of metal hydride is enhanced with decrease of the x. As for LaNi4.4Mn0.26Al0.34 alloy, the lattice parameters and cell volumes are increased, the absorption/desorption plateau pressure is obviously decreased, the hysteresis factor and the absorption kinetics are greatly improved, while the hydrogen content is obviously impaired with Al substituting for partial Ni

Abstract:LaFeO3 and Fe(OH)3-modified LaFeO3 were used as supports for the nano-gold catalysts, respectively. The catalysts were prepared by a deposition- precipitation method and were characterized by XRD, XPS, AAS and BET. Furthermore, the activity and stability, involving the reaction and storage process, were investigated. The results demonstrate that the addition of Fe(OH)3 could improve the stability both in the continual reaction and the preserving process. Therefore the strong interaction between the gold species and Fe(OH)3 could inhibit the aggregation of gold particles and increase the stability of the catalyst.

Abstract:Scanning electron microscopy (SEM) and energy dispersive X-ray spectrometer (EDS) were used to analyze the microstructure and composition changes in the aging process of Sm2Co17 type permanent magnet. The microstructure changes of such magnets in the aging process with the aging temperature and time changes in the law were revealed, and the typical SEM image of microstructure of normal sample was identified. The result of this method is more accurate and more intuitive than optical microscope, and the sample preparation is easier than that of transmission electron microscopy. The application in the production control effect is remarkable

Abstract:Ni76Ti5P19 and Ni73Ti5Zr3P19 (at%) metallic glasses were prepared by a melt-spinning technique. Their thermal stability and corrosion behaviors were investigated, and the effects of Zr addition on the properties of the Ni-Ti-P glassy alloy were discussed. Results show that Zr addition increases the glass transition temperature (Tg) and crystallization temperature (Tx) of the Ni76Ti5P19 glassy alloy, and decreases its supercooled liquid region (ΔTx). Electrochemical tests in NaCl, HCl and H2SO4 solutions indicate passivation behavior of the Ni-Ti(-Zr)-P metallic glasses. Their good corrosion resistance can be attributed to the formation of a protective Ti/Zr- and phosphorus-rich layer on the surface of the alloys. Compared with Ni76Ti5P19 glassy alloy, the Ni73Ti5Zr3P19 glassy alloy exhibits higher open-circuit potential and lower passive current density. Partially replacing Ni with Zr in Ni-Ti-P alloy introduces ZrO2 in the passive film, which improves the protection of the surface film and results in a higher corrosion resistance

Abstract:Ag(90.5%)/Sn(9.5%) alloy powders (mass fraction) were prepared by atomization. The oxidation kinetics curves at 600, 700 and 800 °C were obtained using a thermogravimetric analyzer (TGA). The particle size, surface morphology, phase structure and surface composition of AgSn alloy powders were investigated before and after oxidation. Results show that there is negligible difference in particle size before and after oxidation. After oxidation, a rougher surface and slight volume expansion are observed. Moreover, some small holes and cracks appear at the junction of "scales-like section". Based on the controlling diffusion factors, the oxidation phase can be divided into 3 typical stages: exponentially rapid mass gain stage, crossing transition stage and parabolic slow mass gain stage.

Abstract:The microstructure evolution during the preparation process of BT16 titanium alloy wires, mechanical properties and cold upsetting performance of the wires, and microstructure of the solid-aged alloy were investigated by transmission electron microscope (TEM), scanning electronic microscope (SEN), optical microscope (OM) and X-ray diffraction (XRD). The results show that BT16 alloy wires have excellent mechanical properties with reduction of area Ψ 62%~65%. The cold upsetting bolt can achieve the head deformation of 75% without any defects. The titanium alloy ingot has dendritic α+β phases. Transverse section of the forged billet deforms unevenly and the equiaxial, the short-bar and the needle α phases precipitate. The hot forged bars have the fine needle α phase precipitation in the boundaries and grains. The microstructure of alloy wires consists of the primary equiaxial α phases and intergranular β phases. The microstructure of the solid-aged alloy is composed of equiaxial primary α phases and β phases which precipitate the secondary needle α phases

Abstract:The microstructure and properties of Nb/Nb5Si3 in situ composites prepared from Nb-20Si, Nb-20Si-5Ti, Nb-20Si-15Ti and Nb-20Si-24Ti by the spark plasma sintering (SPS) technique. The microstructures of the synthesized composites were analyzed by SEM, XRD and electron probe microscopy (EPMA). The effects of Ti addition on the microstructure and properties of Nb/Nb5Si3 in situ composites were studied. The result show that the main phase of the composites changes from Nb/Nb5Si3 to Nb/(Nb, Ti)5Si3 due to the Ti addition. The pure Ti phase and Nb3Si phase are found in the composites when the Ti content reaches to 24%. With the content of Ti increasing, the hardness of Nb/Nb5Si3 in-situ composites would be decreased, but the high temperature oxidation property would be increased

Abstract:Organic aprotic polar solvent EtMgCl/THF solution was prepared as magnesium electrodeposition electrolyte, and the initial electrochemical deposition of Mg film electrodeposited on Cu matrix was investigated by cyclic voltammetry (CV). The results show that the deposition of Mg film follows the mechanism of nucleation and subsequent grain growth. The bright, compact and uniform coating of magnesium was obtained by DC (direct current) deposition for changing the electrolyte concentration and current density. The surface morphology and phase composition of the coating were characterized by D8 XRD and SEM respectively. Compared with DC, the grain size by PC (pulse current) are more finer, and the results manifest a preferential orientation of the Mg crystallites parallel to the [002] crystallographic planes.

Abstract:The magnetic pulse welding (MPW) were carried out with the 1060 Aluminum tube and AZ31 Magnesium alloy bar with different surface conditions. Quantitative analysis of the interface morphology of the obtained Al-Mg MPW joints was conducted. The heat production mechanism during MPW process was studied. The results show the MPW joints interface exhibits wave morphology which is the typical character of high velocity impact welding. The pocket type melting phase is distinguished at the joint interface by Mg bar with the smooth surface. However, the continuous melting layer is found at the joint interface by Mg bar with the rough surface. The bumps on the rough surface can catch more impacting jet, and disturb the transportation of the surface wave, which also block the heat lost process. So the interface temperature rises and the melting layer forms

Abstract:The microstructural evolution and room/high-temperature mechanical properties were investigated for a Co-9Al-9W-2Ta alloy with 4at%, 6at% and 9at% Nb additions to replace the same content of W (referred as to 4Nb, 6Nb and 9Nb alloy hereafter, 0Nb for the alloy without Nb addition, and the content of W+Nb=9 at% for all alloys) prepared by arc-melting. Results show that the as-cast alloys exhibit a microstructure composed of Co-base solid solution γ phase (γ-CoSS) and eutectic of γ+ intermetallic compound Co3Nb. While after 1200 °C, 8 h solution and 800 °C, 100 h aging, the cubic γ’ phase with a size of 200~300 nm precipitates homogeneously and coherently on the γ matrix for the 0Nb~6Nb alloys. Besides, cellular and/or needle-like Co3Nb phases are found in the 4Nb~9Nb alloy. The 6Nb alloy shows the highest yield strength in the temperature range of 600~700 °C, while the 4Nb alloy has the highest strength at 800 °C. Alloys exhibit yield stress anomalies at temperatures above 600 °C, and the temperature corresponding to the anomaly stress peak is about 700 °C

Abstract:With Fe(acac)3 as Fe3+source and H2PtCl6·6H2O as Pt4+source, FePt nanoparticles were prepared via chemical reduction process using NaBH4 and poly (N-vinyl-2-pyrrolidone) (PVP) as reductant and surfactant, respectively. The effect of PVP on magnetic properties of FePt nanoparticles was investigated. The as-prepared FePt nanoparticles were characterized by X-ray powder diffraction (XRD), transmission electronmicroscopy (TEM) and vibrating sample magnetometer (VSM). The results show that PVP modified FePt nanoparticles are of face-centered-cubic (fcc) structure, which are spherical shapes with good mono-dispersibility. The particles display superparamagnetic as the coercivity is zero. For the FePt nanoparticles with PVP/Fe(acac)3=7:1, the structure transforms from face-centered-cubic (fcc) to face-centered-tetragonal (fct) after the sample is annealed at 600 °C for 30 min in argon atmosphere, with its coercivity reaching as high as 5400 A·m-1

Abstract:The superficial degradation in vivo and biocompatibility of magnesium alloy (Mg-Al-Zn) coated with tricalcium phosphate (β-TCP) have been evaluated. (β-TCP)-Mg-Al-Zn implants were made and implanted into the femur of rats. The surface microstructure observation of implants and the EDS analysis were carried out. The changes of Ca and P on the surface of the implants were analyzed. Results show that many attachment proteins appear in the surface of (β-TCP)-Mg-Al-Zn after 4 weeks implantation. In the 8th week, the content of Ca and P in the surface of (β-TCP)-Mg-Al-Zn are higher than that in naked Mg-Al-Zn (P＜0.05). In the 12th week, about 33 % of naked Mg-Al-Zn alloy is degraded, while 17 % of (β-TCP)-Mg-Al-Zn is degraded. β-TCP coating can decay the superficial degradation and improve the biocompatibility of Mg-Al-Zn matrix in vivo.

Abstract:Vanadium films were prepared on the surface of aluminum alloy using a high power pulsed magnetron sputtering (HPPMS) method. The influences of the sputtering pressure on the phase structure, surface morphology and tribological properties of vanadium films have been investigated. Results show that the vanadium phase in the vanadium films only grows along the (111) crystal under different pressures. The diffraction peaks increase with increasing the pressure and decrease if the pressure further increasing. The diffraction peak of V(111) is the strongest and the preferred orientation is the most obvious when the pressure is 0.5 Pa. Meanwhile the vanadium film has the smoothest surface with the surface roughness of only 0.267 nm. The samples demonstrate much lower friction coefficient compared with the substrate at room temperature. The sample treated at 0.5 Pa possesses the best tribological properties with the friction coefficient decreasing from 0.57 to 0.28, and there is no obvious spalling on the worn surface. The friction coefficients of vanadium films annealed at 200 and 300 °C is low and stable compared with the unannealed samples, which is attributed to the surface oxidation

Abstract:Nickel-titanium alloy foams with a high porosity, controllable aperture and 3D interconnected porous structure were prepared by an impregnation technique with equiatomic pre-alloy powder as starting material and polyurethane sponge as templates. The alloy foams possess excellent biocompatibility and mechanical compatibility. The phase composition, microstructure and mechanical properties of NiTi foams with different template types (R2D25 and DP91308) were studied by XRD, stereomicroscope, SEM and electronic mechanical testing instrument, respectively. Two types of NiTi foams prepared by the polymer sponge impregnation technique have high porosity (71.8% and 63.8%, respectively) and 3D interconnected porous structure, and the pore sizes are in the range of 250~500 and 150~400 μm, respectively. Compressive yield strength of them is 16.37 and 73.52 MPa, respectively and elastic modulus is 0.51 and 2.45 GPa, respectively, which match with bone in microstructure and mechanical properties.

Abstract:The effect of the melt overheating temperature on solidification characteristics and microstructure of a third generation Ni-based single crystal superalloy was studied by the Differencial Thermal Analysis (DTA) and the melt superheating treatment. The results show that as the melt overheating temperature increases from 1450 to 1500 °C, the nucleation supercooling and solidification interval change a little, the nucleation and growth of γ phase are in a wide range of temperature. When the melt overheating temperature is above 1580 °C, the nucleation supercooling increases sharply and the solidification interval decreases obviously. At the same time, the temperature range of nucleation and growth of γ phase is reduced, the precipitation of γ/γ′ eutectic is decreased, and the precipitation temperature of γ′ phase is elevated by 9 °C compared with the one overheated to 1450 °C. When the melt overheating temperature rises to 1650 °C, the nucleation supercooling decreases, and the solidification interval increases appreciably. As the melt superheating temperature increases from 1500 to 1580 °C, the dendrite structure is refined significantly, but then coarsened slightly when the melt superheating temperature rises to 1650 °C. The results are primarily attributed to the melt structure change caused by the melt overheating temperature, and the solidification characteristics and microstructure of alloy are affected finally

Abstract:An experimental investigation was conducted with pressed pairs of aeroengine hot-end components structure material GH4169/K417 under different interface pressures (60~180 MPa) and surface roughness using the self-developed experimental apparatus to study the effect of interface pressure on thermal contact conductance (TCC). The testing results of TCC under the conditions with and without compensation heater were studied and compared. The results show that the thermal contact conductance experimental apparatus with compensation heater can effectively reduce the lateral heat loss. The effect of contact pressure on thermal contact conductance of specimens with different surface roughness is basically the same, and the specimens with bigger surface roughness have larger TCC values. The differences between these two conditions increase first and then decrease, which depends mostly on the engagement between the rough surfaces when the lay direction is parallel.

Abstract:The Tb9Fe88Cr3 alloy powders were prepared by the arc melting method and high energy ball milling. The phase structure and the microstructure of the alloys powders were analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Then their microwave absorbing properties were analyzed by a vector network analyzer. The results show that the absorbing properties of the powders with micro-oxidation treatment at low frequency are better than that in raw state. On the basis of micro-oxidation treatment, the powders were dealt with by vacuum heat treatment at different temperatures. When the vacuum heat treatment temperature is 350 °C, the absorption peak value of the powders reaches –11.5 dB at 7 GHz. As the temperature of vacuum heat treatment increases, the absorption peak shifts towards the lower frequency region, and the reflectivity increases. When the vacuum heat treatment temperature is 450 and 550 °C, compared to that of the sample only dealt with by micro-oxidation treatment, they have similar absorption frequency, the absorption peak value decreases by 2~3 dB, and the absorbing properties at low frequency region are improved further

Abstract:ITO:Nb thin films with the thickness of 300 nm were prepared by magnetron sputtering using a ceramic niobium doped ITO target at the temperature from room temperature to 300 °C. The structure, conductivity, and the optical transmission in the visible region of ITO:Nb films were investigated. The results of XRD analysis indicate that ITO:Nb thin films are In2O3 single phase. AFM images show that the surface roughness of the film increases with the temperature increasing. The resistivity decreases as the temperature increasing, reaching a minimum value of 1.2×10-4 Ω·cm at 300 °C due to the rising of both Hall mobility and carrier concentration. The average transmittance of films in the visible light region is over 87%. The optical band gap becomes wider and red shift of the absorption edge takes place with the rising of the temperature, which is coincident with the variation trend of the carrier concentration

Abstract:A self-made solidification controlling facility was developed in accordance with the principle of directional solidification to study the solidification behavior of SAC305 solder alloy and the effect of directional solidification on the alloy microstructure. The microstructure of the tin-rich phase grows with significant orientation under the rapid cooling conditions. Increasing the cooling rate can enhance the continuity of columnar tin-rich phase and is likely to inhibit the secondary dendrite growth. Rapid cooling reduces the size and disperses intermetallic compounds significantly, resulting in the increase of the microhardness of the solder.

Abstract:Friction stir processing was applied to 2024-T4 aluminum alloy plate under the condition of forced cooling. The microstructure of each zone (the base metal, the thermo-mechanically affected zone, the stir zone) and the effect of the advancing speed on the mechanical properties of the stir zone were studied. The results show that the grain size decreases gradually from the base metal, through the thermo-mechanically affected zone, to the stir zone. The microstructure in the stir zone is significantly refined and the grains are distributed uniformly with an average size of 1.9 μm. The base metal exhibits a large number of high-angle grain boundaries, while the thermo-mechanically affected zone has numerous low-angle grain boundaries. The distribution of misorientation angle in the stir zone presents a bimodal phenomenon. Hardness and tensile strength of the stir zone are increased with higher advancing speed

Abstract:Both the phase and microstructure evolution of MIM Ti-6Al-4V alloy in the thermo-hydrogenation treatment process were investigated, especially the effect of hydrogen content, to improve mechanical properties. The results show that β-Ti becomes more and more initially and then δ titanium hydride is precipitated as hydrogen content in the alloy increases during the hydrogenation process at 650 °C, so that the bulky sheets in the microstructure of as-MIMed alloy are gradually broken into tiny needles. Solution treatment at 850 °C and isothermal aging at 620 °C make the dissolved hydrogen in the alloy distribute more uniformly and let more needle-like δ precipitate. The alloy remains a refined needle-like microstructure after vacuum dehydrogenation at 720 °C, and the higher the dissolved hydrogen content in the hydrogenised alloy, the more the refined needle-like microstructure after dehydrogenation. For the alloy with 0.51wt% H after hydrogenation, its ultimate tensile strength, yield strength and elongation after dehydrogenation are increased by 11%, 13% and 19%, respectively, in comparison with those of MIM Ti-6Al-4V

Abstract:The process parameters of a chromium-free conversion technique based on permanganate-phosphate solution on die cast magnesium alloy AZ91 have been optimized by orthogonal experiments. The effects of process parameters on thickness, corrosion resistance and morphology of the conversion film were discussed. The results show that the corrosion resistance of the conversion film can be improved by more than 8 times compared with that of the substrate when the concentration of ZnSO4 and NaF are 5 and 1g /L, respectively, and pH = 4. Furthermore, the pH value has significantly affected the thickness, morphology and corrosion resistance of the film. The film is loose and easy to fall off when the pH is too low. Meanwhile only the thin inner conversion film remains and the corrosion resistance is poor. When pH= 4, the film thickness reaches its maximum value, and the inner film adheres closely to the outer film, which significantly improve the corrosion resistance of the conversion coating. However, when the pH increases further, the film becomes dense, but the corrosion resistance increases slightly because of poor bonding between the inner film and the outer one

Abstract:(Fe83Co17)xAg100-x granular films (x=40, 45, 50, 55, 60) were grown on the substrates of glass using the magnetron sputtering system. The structure, GMR and magnetic property of (Fe83Co17)55Ag45 granular film, which were as-deposited and vacuum annealed, were studied by X-ray diffraction (XRD), a four-point probe method and a vibrating sample magnetometer (VSM). The results of magnetic resistance measurement show that GMR of the sample (Fe83Co17)55Ag45 granular film with 400 nm thickness gets the maximum, –8.1%. XRD results show that microstructure of (Fe83Co17)55Ag45 granular film has changed, which leads GMR to firstly increase and then decrease, and the maximum is –8.3% at 150 °C. Meanwhile, the magnetic hysteresis loop illustrates that the coercive force of (Fe83Co17)55Ag45 granular film increases with the annealing temperature increasing

Abstract:Porous palladium (Pd) bulk was prepared by spark plasma sintering (SPS). Afterwards oxidation and deoxidation on the surface of the porous Pd bulk was conducted in the temperature range of 500~600 °C. The microstructure, surface area, porosity and pore size distribution were investigated. The microstructure and chemical composition of the porous Pd bulk surface were characterized by SEM and XPS. The results show that porous Pd bulk with excellent mechanical properties and higher porosity (87.88%) can be prepared by SPS at 550 °C. Carbonaceous impurities on the porous Pd bulk surface can be removed and the surface area of porous Pd bulk as well as the roughness can be increased by oxidation and deoxidation reactions

Abstract:The effects of total strain range and dwell time on low cycle fatigue life of C-276 alloy at 650 °C were investigated. The total strain range controlled fatigue tests were performed at total strains of 0.3%, 0.35%, 0.4%, 0.45% and 0.5% with dwell time of 0, 30 and 60 s respectively. The fracture characteristics were observed by SEM. Results show that the fatigue life significantly decreases with increasing the total strain range for the fixed dwell time due to the enhanced fatigue crack-growth-rate. The effect of dwell time on the fatigue life is dependent on the introduced total strain range. In lower total strain range of 0.35%~0.4%, the fatigue life is decreased by introducing dwell time, which is obviously caused by the coeffect of the enhanced fatigue crack-growth-rate and the presence of some microcracks and cavities. In higher total strain range of 0.45%~0.5%, the fatigue life is increased by introducing dwell time due to the closed microcracks and cavities

Abstract:The intermetallic T2 (Mo5SiB8) alloy was prepared by sparking plasma sintering (SPS). The microstructure and room temperature mechanical properties were characterized by SEM, XRD as well as indentation, compression and notched three-point bending tests. The results show that SPS, a unique plasma activation sintering approach, favors the formation of pure T2 alloy with a dense and fine-grained microstructure. Almost no plastic deformation is observed in the true strain-stress curve of the T2 alloy after room temperature compression and the alloy has a compressive strength of 2907 MPa. The Vickers hardness is 17.86 GPa, while the averaged fracture toughness determined from indentation crack lengths is 3.23 MPa·m1/2, similar to the averaged value of 3.34 MPa·m1/2 from single edge notch bend specimens. The cleavage fracture occurs across {001} planes of the T2 alloy in the three-point bending tests at room temperature. For the T2 alloy, the contribution to room temperature brittleness, high strength and high hardness is mainly derived from the covalent bonds which arrange alternately in the T2 phase

Abstract:Cu-13%Cr-0.24%Zr, Cu-15%Cr-0.24%Zr and Cu-15%Cr deformation in situ composite wires were prepared by cold drawing combined with intermediate heat treatments. The effects of Zr element, Cr content, intermediate annealing temperature and times on the ultimate tensile strength (UTS) and electrical conductivity of Cu-Cr composites were investigated. Results show that Zr element can significantly enhance the UTS, while its effect on the electrical conductivity is modest. With the increase of mass friction of the Cr element, the UTS tends to increase a bit, and it has little impact on the electrical conductivity. Increasing annealing temperature or times can decrease the UTS and improve the electrical conductivity. In the experiment Cu-15%Cr-0.24%Zr in situ deformation wires with excellent comprehensive properties were obtained through the process of twice intermediate annealing at 500 °C, whose UTS reaches 1056 MPa and whose electrical conductivity reaches 73%IACS

Abstract:The effects of temperature and deformation rate on the mechanical properties of TC4 weldment were studied. The dynamic mechanical properties of the weldment were characterized by tension tests at the deformation rates of 0.001, 0.1, 1 and 10 /s. Based on the Johnson-Cook model, the yield strength of TC4 plate was calculated and the experimental data were compared with calculation values. It is concluded that Johnson-Cook model can be used to characterize the change of the yield strength of TC4 weldment under different deformation rates and temperatures

Abstract:The progress in lithium vanadium oxides used as cathode for lithium secondary batteries were reviewed, including vanadium oxides V2O5 and LiV3O8, vanadium oxides of single valence change LiNiVO4, and of double valences change FeVO4. The structures, the methods of preparation and electrochemical performances of these oxides were summarized. The charge-discharge mechanism and modification research status of FeVO4 were introduced