Abstract:In this work, the connection between the boron content and the wettability of TiZrNiCu/Ti60 system was studied by sessile drop method of elevating and maintaining isothermal process under vacuum, and TiBw-TC4 composite was successfully brazed to Ti60 alloy using TiZrNiCu-B filler alloy with brazing temperature of 940 °C for 10 min. The contact angle of TiZrNiCu/Ti60 alloy substrate and the corresponding interfacial microstructure, the interfacial microstructures and shear fractures of brazed joints were studied using SEM, EDS and XRD, and the influence of B content on interfacial microstructure and joining properties was also investigated in detail. Added B element can react with Ti to in-situ synthesizing TiB whiskers (TiB_w), which resulted in a relative refinement of microstructure. And the maximum shear strength of TiBw-TC4/TiZrNiCu-B/Ti60 joint was 177 MPa when the content of B is 0.3 wt.%, which was 65% higher than the joints brazed without B content. However, the excessive B content worsened the wetting behavior of TiZrNiCu-B on Ti60 alloy substrate, resulted in the microvoids and disconnected area in the brazed joint, and the shear strength decreased inevitably.

Abstract:The remanufacturing experiment of FV520B precipitation hardening stainless steel was carried out by using surfacing deposition technology. On this basis, the remanufacturing microstructure characteristics were analyzed and the effect of mechanical vibration on remanufacturing microstructure was studied. The results showed the following: Firstly, the remanufacturing microstructure of FV520B stainless steel by MAG surfacing deposition technology was comprised of martensite plus a carbide precipitation-hardening phase. It performed a characteristic periodical variation along the direction of forming height, which was described by certain self-similar fractal characteristics. The vibration would increase the probability of twin formation to some extent. There was also the broken effect on martensite lath that had to be taken into account. It should be noted that the width of the martensite lath decreased first and then increased with the continuous increase of the vibration rotation rate. Affected by the vibration, the lattice distortion and the preferred orientation of each crystal plane would both be changed. However, the change rule of different crystal planes was different. The Bragg diffraction peak positions of planes (110) and (211) shifted towards the direction of lower diffraction angle due to the addition of vibration. Furthermore, the offset increased first and then decreased with the continuous increase of the vibration speed. Meanwhile, the FWHM of diffraction peak (110) decreased first and then increased and the preferred orientation of this crystal plane increased first and then decreased. Within the range between 0 and the resonance speed, the FWHM of diffraction peak (211) decreased first and then increased with the continuous increase of the vibration speed and decreased again when the vibration speed was higher than the resonance speed. However, its preferred orientation continued to increase with the increase of the vibration rotation rate. In general, the sub-resonance frequency (The vibration rotational speed f=3000 r/min) had the most significant effect on the remanufacturing microstructure of FV520Bstainless steel by MAG surfacing deposition technology.

Abstract:In this paper, the crack initiation mechanism of dissimilar aluminum alloy welded joints was studied. The base metals are 2219 aluminum alloy and 5A06 aluminum alloy, the filler wires are 2325 and 5B06. The microstructure was analyzed by the optical microscope (OM), scanning electron micrograph (SEM) and energy dispersive spectroscopy (EDS). Results showed that the weld hardness obtained by the 2325 is about 100 HV and that by 5B06 is about 80 HV. Compared with heat affected zone (HAZ) of the weld obtained by 2219 and 2325, the grain growth of HAZ of the weld obtained by 5A06 and 2325 is not so obvious that the joint softening phenomenon doesn’t exist. The diffusion and segregation of Mg element and Cu element can be obviously observed in the welded fusion zone (FZ) obtained by 2325 and 5A06, and that by 5B06 and 2219. Compared with the welded joint obtained by 5B06 filler wire, the great cracking tendency can be found in dissimilar welded joint obtained by 2325 filler wire, because there is no obvious low melting eutectics in welded joint by 5B06 filler wire. Many low melting eutectics (Al2CuMg and CuAl2) present in the welded joint by 2325 filler wire, and the Al2CuMg eutectics are fundamental cause for the crack initiation.

Abstract:Friction stir welding (FSW) has been validated to be a severe plastic deformation method for development of ultrafine-grained metals. In this study, hot-rolled AZ31 magnesium alloy plate was processed by FSW, and the effect of FSW on the low-cycle fatigue (LCF) behavior of AZ31 magnesium alloy was analyzed. Results showed that the interface between the stir zone and thermo-mechanically affected zone at the advancing side is the weakest region, in which the monotonic tensile and fatigue fracture occur. Compared with the base metal (BM), the LCF fatigue life, the yield strength, the ultimate tensile strength and the elongation of FSW specimen decrease. The main deformation during LCF was dislocation slip deformation. The fracture surface exhibited a typical fatigue characteristic with the fatigue striations. Finally, we found that the LCF behavior of BM and FSW specimens can be well described by the Coffin-Manson and Basquin’s relations.

Abstract:Aluminum alloy friction stir welding (FSW) tends to produce hole defects, reducing the mechanical properties of Tailor Welded Blanket (TWB). However, the effect of hole defects on the crack propagation of welding joints is not clear yet,which greatly limits the application of tailor-welded blanks. Based on the partition modeling of the FSW joint with holes for 2024 aluminum alloy, the paper studied the influence law of hole size of joint on crack propagation through the tests combined with the finite element method. The results show that the mechanical properties of the joint increase with the decrease of the hole size under quasi-static service conditions, the heat affected zone is fractured, the mechanical properties of the joint are basically the same as those without the defect when the hole diameter is less than 0.1 mm; WNZ with hole defect is fractured when the diameter of the hole is larger than 0.1 mm. The fatigue properties of the joint increase with the decrease of the hole size under the condition of fatigue load, and the sensitivity to the load decreases gradually; there will be a temperature rise in the fracture and the fracture always takes place in the WNZ with hole defect.

Abstract:Due to the connection problem of Cu/W during the rolling process of tungsten plate, dissimilar metals Cu/W are welded by Tungsten inert gas(TIG) welding.In the case of coating SiO2 and uncoating SiO2 activating flux,the spot welding of W overlapped by Cu was conducted,respectively,the appearance of spot welding,cross-section,microstructure and tensile strength of joints were analyzed,respectively.The results indicate that top surface of the welding spots uncoated SiO2 are convex and irregular,many holes at the interface,in the case of coating SiO2,the center of welding spot appears round pits,the number of holes at interface reduce.Interdiffusion occurs between Cu and W,the interface of samples coated with SiO2 is more tightness than the uncoated. When the welding current is same,the strength of joint coated with SiO2 are higher than the uncoated,in the two cases of welding ,fracture exists a large different.

Abstract:Supercapacitors are widely used as energy storing device in a wide range of communication, transportation and daily life, including hybrid electric vehicles, new energy collection and conversion, high-power construction machinery, mobile electronic equipment, and so forth. The electrode materials of supercapacitor require effective, controllable porous structure, specific surface area, reasonable pore size distribution, good electrical conductivity and easy molding. Nanoporous copper is a kind of porous material with high conductivity, high specific surface area, controllable aperture and good capacitance. It can be used as a current collector loads more active materials for supercapacitor, and thus greatly improves the energy density of supercapacitor. In addition, the modified nanoporous copper can enhance physical and chemical stabilities of porous copper substrate and retain more active sites. It offers a kind of idea for controllable design electrode of supercapacitors.

Abstract:In this article, a mathematical model was developed to investigate the electron beam melting (EBM) process of vanadium alloys. The temperature distribution of molten V-4Cr-4Ti alloy was obtained by using the model. The effects of different parameters of electron beam melting process on the temperature field and the shape of molten pool were studied. The results showed that the temperature field and the shape of molten pool were influenced by the melting power and scanning radius. With the melting power increasing, the max melt temperature increased linearly and the width and depth of molten pool increased gradually. With the scanning radius increasing, the max melt temperature increased first and then reduced. The optimized parameters of refining vanadium were obtained, and the accuracy of the model was validated by the experimental data.

Abstract:The damage mechanism of commercial 2060 (T8) aluminum alloy during bending was studied in this work. The microstructure evolution and strain localization was collected by Electron Backscattered Diffraction (EBSD) and Digital Image Correlation (DIC) methods, respectively. The new method based on the dispersion distribution of copper powders was developed, which can be used to characterize the strain distribution and microstructure evolution of the same region simultaneously. The experimental results showed that macro shear band formed during bending and the crack grow along the macro shear band, the reason for this phenomenon can be attributed to the larger volume fraction of Small Angle Grain Boundary (SAGBs) formed in the region of macro shear band, since less energy was needed if the crack propagated along the direction of macro shear bands.

Abstract:The time-temperature-transformation (TTT) curve and time-temperature-property (TTP) curve of Al-9.0Zn-2.5Mg-1.5Cu-0.15Zr-0.2Sc alloy were determined by interrupted quenching technique. Phase transformations have been investigated by TEM, DSC and XRD. The result shows that under certain temperature and prolonging the holding time, the electro-conductivity of the specimens tend to increase and the hardness will decreases. Microstructure observation indicates that with the time increased, a lot of large equilibrium rod-shaped η (MgZn2)phase precipitated in the matrix and grew rapidly, which results in loss of solutes in the aging process and weakened the strengthening effect. The main reasons for precipitation of η particles are that the rapid diffusion of solute atoms and the strong driving force for phase transformation. Quench sensitive temperature range is 270℃~390℃. Consequently, the cooling rate should?be consider?lowering appropriately from the solution temperature to 390℃ to control the residual stress. And then, in the quench sensitive range, it is necessary to increase the cooling rate properly to obtain high mechanical properties.

Abstract:In the thixo-extrusion process, the fiber orientation can be effectively controlled by applying the hydrostatic pressure (i.e., backpressure), and consequently improving mechanical properties of short fiber reinforced composites. In this paper, the variation regularities of the deformation field and fiber orientation during the thixo-extrusion process of Csf/AZ91D composites with and without backpressure were investigated experimentally. The equivalent strain rates along the flow line were obtained based on the flow function method. By employing the image processing technology, the angle of fiber orientation after extrusion was statistically analyzed. The results show that there was an obvious equivalent strain rate gradient from the outer wall to the core of the composite without applying backpressure. At the same position, the fiber orientation angle was almost proportional to the equivalent strain rate. Furthermore, the applied backpressure enhanced the ability of the composite to fill the outer corners of the mold, resulting in a smaller equivalent strain rate gradient across the cross-section. Comparing with the thixo-extrusion without backpressure, the equivalent strain rate distribution is more uniform and fiber orientation angle is more consistent by the application of backpressure. The research results have important guiding significance for regulating the plastic deformation of Csf/AZ91D composites.

Abstract:A high entropy bulk metallic glass (HE-BMG) Cu₂₉Zr₃₂Ti₁₅Al₅Ni₁₉ was investigated by nanoindentation in detail with load-controlled, continuous stiffness measurement (CSM) and cyclic loading mode, respectively. Pop-in occurs in this alloy during nanoindentation. Applied load have more influences on the pop-in events than loading rate does. When the applied load is larger than 40mN, obvious pop-in events can be observed in the loading curves even at high up to 5mN/s loading rate. Indentation size effect exists in this alloy, confirmed by the hardness decreasing with the increasing indentation load and a Meyer’s index n less than 2. The fraction of energy dissipated during indentation (E_d) changes within the range of 54%-60%. Cyclic loading tests reveal obvious hardening effect.

Abstract:W-ZrC composites are promising materials for plasma face components. In this article, a process of “sol gel – heterogeneous precipitation –spray drying – hydrogen reduction – ordinary consolidation sintering” was used to prepare W-ZrC composites. The toughening mechanisms and interfacial bonding of W-ZrC composites were studied. ZrC particles could improve the strength and toughness of tungsten. The relative density and tensile strength of W-0.5wt.%ZrC are 99.2 % and 460 MPa sintering at 1920 °C. Preliminary transient high-heat flux test shows that W-ZrC composites can endure high-heat flux of 200 MW/m₂(5 ms), and ZrC particles can consume the crack propagation energy and hinder crack propagation. ZrC particles had a process of growing up and rounding, and translated into nearly spherical particles sintering at 1600 °C held for 1 h. At the interfacial bonding zone of ZrC particles and tungsten, W, Zr, and C elements were smooth transition. The hardness of W,ZrC and interfacial bonging zone were 12 GPa, 22 GPa, and 18 GPa, respectively. The linear SEM-EDS and nanoindentation results indicate that the W and ZrC particles form (W,Zr)C compound.

Abstract:The property of thermal ductility and hot cracking sensibility for the forge and rolling plate with 70mm thickness nickel alloy were studied using an optical microscope (OM), scanning electron microscope (SEM), and Gleeble 1500 thermal simulation equipment. The results show that the forge and rolling plate have excellent thermal ductility; the samples taken from surface position have higher thermal ductility than those taken from middle position at the same plate. The rolling plate has higher thermal ductility than the forge plate at the lower temperature during heating process. As rising the temperature, the forge plate has higher thermal ductility than the rolling plate. During the cooling process, the forge plate shows higher thermal ductility than the rolling plate. The rupture sections have more smooth morphology, even some sections exist the melt phenomenon. The forge and rolling nickel alloy 690 have high hot cracking sensitivity. The crack number and length increased with the strain increased.

Abstract:The effects of Sn addition on the microstructure and tensile properties of as-cast AZ80 alloy were investigated by the means of OM, XRD, SEM and tensile property test. The microstructure of as-cast AZ80-xSn (x=1, 3, 5, wt.% ) alloys appears typical equiaxed dendrites morphology, which consists of a-Mg primary, divorced eutectic (Mg+Mg₁₇Al₁₂), laminar Mg₁₇Al₁₂, divorced eutectic Mg₂Sn. The addition of Sn elecment effectively suppressed the laminar Mg₁₇Al₁₂ phase precipitating duringSsolidification. When the Sn content was 5 wt.%, the laminar Mg₁₇Al₁₂ phase nearly disappeared. The grain size reduced when the Sn content less than 3 wt.%. Moreover, The alloy was strengthened significantly by Sn content and the AZ80-3Sn alloy had the superior mechanical property.

Abstract:The influence of pre aging heat treatment on microstructure and mechanical properties of coarse grained β titanium alloy has been studied in this paper. The pre aging heat treatment could serve as a precipitation step to provide uniform dispersed precursors for secondary α phase precipitation, and then leads to the dense, finely and homogenous distribution of secondary α phase. Prolonging of the pre aging time results in the finer scale of secondary α phase. The pre aging heat treatment strongly affects the mechanical properties of β titanium alloy. Within a coarse grain condition, the strength tested in this work is about 1340MPa when single aging at 550oC. However, the strength achieves to 1760MPa when pre aging at 350oC before 550oC, which increased by more than 30% compares to single aging. The micro hardness of the alloy also be improved markedly by pre aging. The effect of pre aging time on mechanical properties is that the prolonging of the pre aging time leads to the increase of strength and micro hardness, but the ductility is sacrificed, which is mainly due to the refinement of secondary α phase.

Abstract:This paper aimed to use explosive consolidation to fabricate tungsten–tin alloy powder. The tungsten–tin alloy powder was prepared at first. In order to obtain tungsten–tin alloy powder, the weldability between tungsten and tin was studied. The tungsten–tin interface did not show any crack, indicating the successful welding of tungsten and tin. Result provided basis for producing tungsten–tin alloy powder. The Vickers hardness (HV) is very important to explosive consolidation. In order to obtain HV of the tungsten–tin alloy material, the tungsten–tin powder was consolidated by explosive consolidation. The detonation velocity (D_C-J) of ammonium nitrate fuel oil (ANFO) was measured by continuous velocity probe. The detonation pressure (P_C-J) was approximately 3.24 GPa simulated by D_C-J. The density of the consolidated tungsten–tin alloy block was 16.017 g cm_-3. The hardness values of the tungsten–tin alloy block were in the range of 210–247 HV.

Abstract:In this paper, aiming at the problem of non-infiltration between FeCuNbSiB amorphous alloy strips and epoxy resin matrix, the interface layer of Cu_0.75Fe_2.25O₄ and Fe₃O₄ phases, which the thickness was about 5μm~10μm, was successfully obtained on the both sides of FeCuNbSiB amorphous alloy strips by surface chemical modification. The interface layer has high bonding strength with FeCuNbSiB amorphous alloy strips, and good infiltration with epoxy resin matrix. The epoxy resin matrix composites using the amorphous alloy strips as reinforcing materials were prepared according to FSS grid design, the electromagnetic wave absorption peaks of composite board appeared in the frequency range of 13-18GHz and the value of reflectivity R was between -5dB and -10dB.The value of absorption peaks kept constant but absorption peak frequency bands shifted to lower frequency along with increasing the layer number of FeCuNbSiB strips. This kind of character can be used to modify radar absorbing properties of other composites and broaden absorption band.

Abstract:The mechanical behaviors of silica-based cores for the directional solidification of single crystal superalloy hollow blades were investigated. The experimental results of strength, elastic modulus and stress-strain relationship of sintered samples S0 and heat treatment samples S1, S2 and S3 were obtained. Based on the Weibull distribution statistics, the continuous damage constitutive model of silica-based cores for the directional solidification of single crystal superalloy hollow blades was established by using M-C (Mohr-Coulomb) criterion. The method of determining the relevant parameters of the continuous damage constitutive model was given. The results show that the mechanical properties and the degrees-of-sinter of silica-based core samples with heat treatment at 1500℃ are improved. The relationship between the crack propagation and the macroscopic fracture of silica-based cores is described by using the damage variable D in the constitutive model and microstructure.

Abstract:Se-based glass is an important system on account of its excellence glass formation ability.The Ge₄Se₉₆ glass was prepared by melt quenched method. The stepwise method for measuring specific heat (C_p) was studied, C_p of Ge₄Se₉₆ glass was then measured and the relation of and temperature T for undercooled liquid was determined. The characteristic temperatures (the strain point, annealing point, glass transition point, yielding point,and soften point) were determined by thermal analysis. The result shows that the glass transition point is 81.5 ℃; the average thermal expansion coefficient is ΔL/L=(0.0557*T-1.7576)/1000. With the result of C_p, the Gibbs energy and the entropy curves were calculated. The Kauzmann temperature can then be determined as T_k=239K.

Abstract:The creep tests were carried out on Ultra-fine grained commercial purity zirconium under the stresses of 0.875 Rp0.2、0.9 Rp0.2、0.9125 Rp0.2、0.925 Rp0.2、0.9375 Rp0.2、0.95 Rp0.2 at ambient temperature. Steady state creep rate was calculated. The creep fracture of UFG CP Zr was investigated by SEM. A new expression was proposed which fit the creep of UFG CP Zr better. It was found that the creep saturation phenomenon happened under 0.875 Rp0.2; the steady state creep rate increased with the rise of creep stress which led the steady state creep stage shortening; the maximum of steady state creep rate was 3.140×10-6s-1 under 0.95 Rp0.2. According to the calculated creep stress exponent, the creep mechanism can be categorized into the dislocation motion. The creep fracture of UFG CP Zrwas ductile fracture.

Abstract:The high temperature thermal compression test was carried out by using Gleeble-1500 thermal simulator for the Ti-6Al-4V alloy prepared by hot isostatic pressing process in the temperature range of 950~1050°C, strain rate range of 0.01~1s_-1 and engineering compressive strain of 70%. The effect of deformation temperature and strain rate on the microstructure evolution of the alloy was investigated. The results showed that the microstructure was mainly composed of corase β grains and needle and lath martensite, which exhibited typical microstructure character in β-phase filed hot deformation after water quenching. The β transformed lamellar microstructure in the β grain form basketweave structure with certain craystall misorientation. The microstructure analysis illustrated that dynamic recovery and dynamic recrystallization occtured during thermal compression. When the condition of 950℃,0.01s_-1, deformation mechanism was dynamic recrystallization and the uniform equiaxed β grain with β transformed microstructure was obtained. With increasing of strain rate, β grains were elongated to long strip in the direction perpendicular to the compression direction, and the β transformed lamellar microstructure was refined, which was attributed to that the dynamic recovery was the main deformation mechanism. As the temperature increased, the size of β grains and β transformed lamellar microstructure increased. However, the strip shaped β grains were still maintained.

Abstract:In order to study the flow behavior of TA32 titanium alloy and set up the constitutive model at high temperature, this paper carries out a tensile experiment at temperatures in the range of 650℃-850℃ and at strain rates of 0.1-0.0001s_-1. The result indicated that the TA32 titanium alloy maintains a comprehensive performance at high temperature (about 650℃) . the behavior of tensile process at high temperature arises work hardening and dynamic recovery obviously at the range from 650℃ to 750℃ and low strain rate of 10_-1-10_-3s_-1 while the elongation of TA32 increases enormously and strength decreases clearly as temperature rises to 800℃ . At the mean time, the steady stage of stress occurs. The constitutive model of Arrhenius-type was constructed by using a specific correction method based on statistic and regularization. The comparison shows a more accurate flow predicted stress through modified model against to the conventional least squares model.

Abstract:The effect of grain size in nanocrystalline alloys is difficult to reveal experimentally because challenges of controlling a number of other microstructure factors. This paper designed and prepared a series of multilayered films with Al-TiB2 crystalline layers of different thickness but with amorphous layers of identical thickness. In these multilayered films, the heights of columnar crystals in crystalline layers were controlled from 8 to 128nm and their diameters kept at ~15 nm, independent of their heights. This design achieved the control of grain size, independent from other microstructure factors. The analysis of mechanical properties of these multilayered films showed that the inverse Hall-Petch phenomenon also exists in Al-TiB2 nanocrystalline alloys , as nanorystalline pure Al. The critical grain sizes of deviation from the Hall-Petch relationship and the inverse Hall-Petch phenomenon are approximately 32 nm and 8 nm respectively. These critical grain sizes are similar to those reports in nanorystalline pure Al by molecular dynamic simulations.

Abstract:The evolution of surface microstructure of the poly crystals formed in TiAl alloy which is treated by laser shock processing is studied in this paper. After a single laser shock peening treated, there are some uneven distributed briefs in the pits formed on the surface of the sample was found, the relative height of briefs ranges from 100 nm to 300 nm and the raised edge is an annular boss. When the samples are treated with different energy density lasers, research on the protrusions showed that the numbers increased significantly and the relative height have an increasing tendency, and the average surface roughness of the pits increased obviously. Further study on the changes in shape of multiple impacts with the spot overlap rate of 50% reveals that the number of briefs significantly reduced compared with a single laser shock processing treatment, and the surface roughness is slightly increased. This is because the elastic deformation and plastic deformation tends to be saturated with the increase in the number of laser shock processing treatment, and the elastic deformation part gets rebound. The formation mechanism of the surface protrusions is analyzed, and the uneven plastic deformation flow model and shock wave superposition model are established. The surface topography formed by laser shock processing is the result of the coupling effect of the two models.

Abstract:_{: In order to study the flow stress characteristics of Ti2AlNb alloy under high strain rate conditions, the quasi-static tensile curves was obtained with electronic universal testing machine, and the dynamic true stress-strain curves under high strain rate was obtained with split Hopkinson pressure bar. The results show that the flow stress of Ti2AlNb alloy has a strong sensitivity to strain rate conditions. Ti2AlNb alloy has strain work-hardening, strain rate strengthening and plasticity-increasing effect under high strain rate conditions. The adiabatic temperature rise in the plastic deformation process has a softening effect on the material. It is found that the appearance of adiabatic shear band is the main reason for the rapid decrease of flow stress under the condition of high strain rate loading. The dynamic constitutive relation of Ti2AlNb alloy at room temperature was obtained by fitting the experimental data with improved Johnson-Cook constitutive model. Compared with the experimental results, it is proved that the improved model can predict the flow stress of Ti2AlNb alloy well under high strain rate conditions.}

Abstract:The tensile deformation and fracture behavior of the Ti555211 alloy were investigated using in-situ SEM technology. Results showed that it was found that slip bands were given priority within the lamellar structure with the tensile loading direction for the Ti555211 alloy with initial lamellar structure. As the crack propagated, the slip bands appeared dense. Moreover, for the alloy with initial lamellar structure, the crack propagated from the corners of the indention both across and along the lamellar directions.The Ti555211 alloy with initial lamellar structure show different fracture morphologies. For the alloy with initial lamellar structure, visible shear lips and a number of dimples were observed in fracture. The deformation and fracture behavior of the near-β titanium alloy of Ti555211 can be tracked by the SEM in-situ tensile test method in real time. The results of this method are more scientific and informative.

Abstract:Study on heating process of molybdenum particles in radio frequency plasma can provide theoretical guidelines for improving preparation process of plasma spheroidization. In this paper, the effect of coil current frequency, postion of injection probe tip and powder feeder rate on motion trajectories and heating process of molybdenum particles in plasma have been studied by using numerical simulation method. The research shows that molybdenum particles can be heated to higher temperature during the spheroidization process when coil current frequency is lower beacuase of higher plasma temperature; Chaning of injection probe tip postion have great effect on motion and heating of smaller particles; Decrease of powder feeder rate can increase the energy get from plasma, thus improving the spheroidization effect.

Abstract:617B is a solid-solution strengthened Ni-based superalloy, a candidate material for 700℃ A-USC power plant. It is always used in solution-anneal at about 700℃. So it is significant to research its microstructure evolution during aging at its service temperature rang form 650℃ to 750℃. In this work, the 617B alloy was exposed prolonged approximately 3000h at 650℃, 700℃, 750℃ respectively. The microstructure evolution had been characterized by optical microscope (OM), field emission scanning electron microscope (FESEM) and energy dispersive spectrometer (EDS). γ" phase and Cr, Mo-rich M23C6 were the major precipitates during aging treatment. γ" phase precipitated at about 650℃,600h and got coarsening with a prolonged time and an increasing temperature. The coarsening of γ" phase met the LSW theory below 700℃ aging but when exposed higher than 750℃, it was priority to coarsen by agglomeration. The carbides along grain boundaries were transformed into continuous network structure by the gradual coarsening of small serration carbides. And carbides within grains increased during aging. When alloy undergone 750℃ long-term aged, there are reactions between carbides, matrix and γ"phase.

Abstract:In the present paper, we systematically studied the electrodeposition behaviors of iron, as well as the effects of overpotential and hydrogen bond donors on iron morphology in three deep eutectic solvents. It has found that the overpotential has no effect on iron morphology in DES1 and DES2. However, the overpotential plays an important role in shape evolution of iron deposited in DES3. In addition, this study shows that changing the hydrogen bond obviously affects the morphology of the iron deposited: The presence of urea hydrogen bond donor is conducive to the formation of film with flake network structure; and ethylene glycol hydrogen bond donor can facilitate the formation of quasi-sphere; while with the synergy of ethylene glycol and malonic acid, hollow nanospheres and yarn ball-like nanoparticles are beneficial to form.

Abstract:The ordering behavior and the mechanical properties come from the doped element of the L1₂ type Al₃Sc-based intermetallics were studied by using sublattice model supported with first-principles calculations. The results show that the intermetallics Al₃Sc is fully ordered intermetallics, where Al atoms always occupy the 3c sublattice and Sc atoms always occupy the 1a sublattice. L1₂-Al₃(Sc_0.75M_0.25) intermetallics(where M=Y, Ti, Zr and Hf)is fully ordered intermetallics, where M always occupy the 1a sublattice. The site preferences of these alloying elements are independent of the heat treatment temperature. L1₂-Al₃(Sc_0.75M_0.25) intermetallics satisfy the mechanical stability conditions.The shear modulus, elastic modulus, young"s modulus and the hardness of L1₂-Al₃(Sc_0.75Y_0.25) intermetallics are are smaller than L1₂-Al₃Sc. The shear modulus, elastic modulus, young"s modulus and the hardness of L1₂-Al₃(Sc_0.75M_0.25) intermetallics, where M=Ti, Zr or Hf, decrease with the increasing of the atomic radius. L1₂-Al₃(Sc_0.75Ti_0.25) has the best plasticity and toughness compared with other L1₂-Al₃(Sc_0.75M_0.25).

Abstract:The isothermal oxidation behavior of Hastelloy N superalloy with different silicon contents in air at 850℃ were investigated by using discontinuous increasing weight method. The results showed that oxidation mass gain kinetics of the samples follow the parabolic law. It was observed that the surfaces of the alloys exhibited a multi-layer structure after 100h oxidation. The outer oxide flim of Hastelloy N superalloy mainly consists of NiO, NiFe₂O₄and other oxide composites. The middle layer is confirmed to be Cr₂O₃ and MoO₂. Since a continuous and dense SiO₂ sublayer is formed at the metal-oxide interface, it is effective to prevent Cr diffusion. The addition of Si promotes the formation of a relatively continuous and compact Cr₂O₃ and it can strongly improve the oxidation resistance.

Abstract:The magnetic properties and loss characteristics of ferromagnetic materials in 300K and 77K environments were investigated by means of simulated impact method. In ferromagnetic materials DT4, 1J22, 2Cr13 and amorphous FeSiB alloy as the research sample, the results of the study show that in nitrogen environment, saturation magnetic induction intension of DT4, 1J22, 2Cr13 and amorphous FeSiB were slightly increased, the saturation magnetic induction intension of FeSiB increases to a maximum of 5.3%; The coercive force of DT4, amorphous FeSiB and 2Cr13 increases greatly, and the coercive force of DT4 increases by 106%, while the 1J22 decreases by 1.7%; When the frequency is 50Hz, the loss of DT4 in liquid nitrogen environment increases sharply compared with that at normal temperature. The loss of amorphous FeSiB and 2Cr13 increases slightly compared with the normal temperature, while the loss of 1J22 varies little. Finally, the magnetic field calculation of the magnetron sputtering cathode with superconducting coil excitation is taken as an example. Under the same structure of iron core, the maximum value of the horizontal component of magnetic field is 2284Gs with 1J22 as the core of the magnetron sputtering cathode. Compared with 2Cr13 as the iron core, the maximum value of the horizontal component of magnetic field increases by 9.2%. The study of low temperature magnetic properties of ferromagnetic materials can provide reference for the design of magnetic circuit of superconducting electromagnetic equipment.

Abstract:The corrosion behavior of cerium (Ce) in excess deuterium (D2) was investigated by the pressure-volume-temperature system (PVT) and the hot-stage microscopy (hot-stage microscope, HSM). The phase composition and thermal stability of cerium-deuterium reaction products were investigated by X ray diffraction (XRD) and thermal desorption spectroscopy (TDS). The results show that cerium can quickly react with deuterium to form saturated cerium deuteride (CeD3) at room temperature and the initial deuterium pressure of 43 kPa. After the reaction, the sample is seriously pulverized. A series of cerium deuterides, which have different content of deuterium, can be obtained by heating the saturated cerium deuteride at different temperature. The cerium deuterides have the face-centered cubic (fcc) structure similar to cerium at room temperature. The volume expansion ratio of CeD2 is about 24.3% relative to Ce. However, with the increase of deuterium content, anomalous volume shrinkage of cerium deuteride emerges. Thermal desorption spectrums show that CeD3 could decompose at 120 ℃, but CeD2 could be stable above 600 ℃.

Abstract:TC4/TC11 dual alloy specimens with different component gradients in the transition zone, were prepared by laser deposition technique. The effects of different transition layer number and different heat treatment on the microstructure, tensile properties and micro-hardness of TC4/TC11 dual alloy interface were investigated. The results show that the transition layer number has a great influence on the morphology of the microstructure, and the increase of the transition layer reduces the interface difference between TC4 and TC11 alloys and makes the micro-hardness distribution more uniform. The change of deposited TC4/TC11 transition basket-weave microstructure is obvious, the microstructure after stress relief annealing is much more uniform and the microstructure after solution-aging treatment is much coarser and the difference is obvious. Form the room temperature tensile test results on specimens after stress relief annealing, it can be concluded that the increase of transition layer improves the tensile strength and plasticity of TC4/TC11 dual alloy, and that fractures occurs on the side of TC4 titanium alloy, which shows that the transition interface performance of TC4/TC11 dual alloy is good.

Abstract:A series of TiN films were prepared by high power pulse sputtering with different pulse width parameter, and the morphology, growth pattern and mechanical properties were studied by XRD, SEM, AFM and other means of the films. The result shows that the instantaneous deposition rate of TiN films increase, the crystalline degree increases gradually, and the grain size of the films increases with the increasing of pulse width. The micro morphology shows typical triangular cone and columnar growth of TiN(111) crystal orientation. Both particle size and surface roughness increase during the increasing of pulse width. No obvious pores and significant defects exist in the films. In mechanical properties, the analysis of H\E value shows that the films have better comprehensive properties, higher coating hardness and larger Hardness modulus ratio under the condition of small pulse width.

Abstract:In this paper, the sample of Ti/Ni multilayered composites fabricated by 5 cycles ARB were treated with different heat treatment. The microstructure, interface structure and the thickness of Ti/Ni interface diffusion layer were analyzed by the optical microscope(OM) and scanning electron microscopy (SEM) analysis technology, combined with the dynamic theory to study the diffusion behavior of Ti/Ni interface. The results show that the Ti/Ni interface did not diffusion during accumulative roll bonding processes. After heat treatment with(550 ℃-750 ℃)×(0.5 h-8 h), the Ti/Ni interface occurred diffusion, the thickness of diffusion layer was power function within the experimental time, the thickness is exponential function relation with temperature. With the increase of heat treatment temperature, the growth of Ti - Ni diffusion layer was controlled by the body diffusion under 650 ℃ gradually transformed into grain boundary diffusion controlled. Through the calculation and verification we can get the dynamics equation of reaction layer growth of Ti/Ni interface of Ti/Ni multi-layer structure composite material produced by 5 cycles accumulative roll bonding is:y=1.7043*104*exp(-78202/RT) *t1.2009-0.0008T .

Abstract:Single-phase alloy compound FeTe<sub>2</sub> was rapidly synthesized by vacuum high temperature sintering in the temperature range of 803K~923K. At the preparation temperature of 863.15K, the effect of different holding time on the preparation of single phase FeTe<sub>2</sub> was examined. The crystallographic properties and microstructure were characterized by X-ray diffraction and electron probe microanalysis separately. Seebeck coefficient and electrical resistivity were measured at room temperature. The results show that the single-phase polycrystalline compound FeTe<sub>2</sub> can be rapidly prepared by high-temperature sintering reaction. There are many micron-sized pores evenly inside the sample. The transport properties were measured at room temperature. The maximum Seebeck coefficient was 88.21 88.21μV/k at preparation temperature of 863.15K and holding time of 60 min. When the preparation temperature was 803.15K and the holding time was 30min, the minimum resistivity was 7.86 mΩ.cm. The maximum power factor 53.82 μW/(m.k<sub>2</sub>) was obtained when the sample was prepared at 923.15K temperature for 30min.

Abstract:In this paper, a multi-core composite wire (3 #) with graphene-coated niobium powder reinforced Cu-Nb was prepared by using powder casting technology, Cu-Nb multi-core composite wire (4#) reinforced the grapheme and niobium powder, and Cu-Nb multi-core composite wire (5#) reinforced pure niobium powder. It is found that the i ntensity of Nb (110) diffraction peak is obviously enhanced after 800 ℃ / 60h heat treatment by the optimized heat treatment process.The microstructure and energy spectrum analysis (EDS) show that the high temperature heat treatment is favorable for the slight diffusion of Cu / Nb interface between, the bonding strength of interface and wire plasticity have been significantly improved.The results show that the conductivity of Cu-Nb-C-Nb wire with graphene-coated niobium powder is better than that of the other two kinds of wires. Finally, Plastic deformation mechanism and micro-mechanism of performance change of the three different materials are analysised.The idea of further optimization of the process is put forward, which opens up a new direction for the preparation of high strength and high conductivity multi-element composite wire.

Abstract:The Li-rich manganese-based cathode of Li1.2+xNi0.1Co0.2Mn0.5O2(x=0, 0.036, 0.060, 0.096) was synthesized by a rheological phase method. The effect of extra lithium amount on the structure and electrochemical properties was discussed. X-ray diffraction (XRD) indicates that all samples had typical α-NaFeO2 structure and small cationic mixing degree. Scanning electron microscope (SEM) showed that the materials with different amount of extra lithium were relatively uniform, smootn surface. The result of electrochemical tests showed that the material with optimal amount of extra lithium (x=0.036) achieved the best electrochemical performance. The tesing of electrical performance between 2~ 4.8V at 0.05C showed that the initial discharge capacity was up to 215.3mAh?g-1 at 25℃ with the initial efficiency of 69.7% and 297.1mAh?g-1 at 55℃ with the initial efficiency of 84.6 %。After 50 cycles at 0.2C, the capacity retention was 89.0% at 25℃ and 87.8% at 55℃. And when x=0.036, the material had the best rate performance.

Abstract:MoW coating was prepared by supersonic plasma spraying technology on 45CrNiMoVA steel. The bonding strength of the coating were tested. The electrical conductivity of the coating was tested by resistance tester. The arc erosion test of MoW coating with different discharge current in atmosphere was carried out by using high voltage arc device. The coating structure was analyzed by field emission scanning microscope (SEM) and electron spectrometer (EDS), and the phase composition of the coating was tested by X ray diffractometer. The results show that the MoW coating prepared by the supersonic plasma spraying process has good adhesion with the substrate, and the conductivity is 6.12%IACS. The addition of W improves the chemical defect ratio of coating and leads to the decrease of conductivity. Porosity is one of the main reasons for low conductivity of coating. The oxidation has little influence on the conductivity of MoW coating. As the discharge current increases, the MoW coating arc erosion area increased significantly; the current size of the errosion coating reflects two different errosion morphology; the greater the porosity, surface roughness, arc erosion resistance of the coating performance worse. The arc erosion resistance of MoW coating is better than that of pure Mo coating.

Abstract:High temperature oxidation behaviors of cast K317 and K325 alloy at 900°C and 1000°C in air environment are contrastively investigated by TGA, XRD and SEM (EDS). The results show that K317 alloy has a superior oxidation resistance compared with K325 alloy. The kinetic curves of two alloys oxidized at 900°C for 100 h obey the parabolic rate law while those at 1000°C obey sectionally the parabolic rate law. The oxide structure of K317, from the top surface down to the base material, consists of NiO-TiO₂-NiCr₂O₄ composite oxide, Cr₂O₃ oxide dense band and Al₂O₃ internal oxide. In comparison, internal oxidation is not observed in K325 alloy whose oxide layer is composed by two oxide layers: NiO-NiCr₂O₄-Nb₂O₅ composite oxide and Cr₂O₃ oxide layer. Serious MoO₃ volatilization and oxide spallation take place in K325 alloy after the oxidation at 1000°C for 100h. In addition, the adhesion property of K325 alloy is worse than that of K317 alloy due to the occurrence of the micro-voids on the oxide layer/substrate interface.

Abstract:A Co₉S₈ film was in-situ deposited onto nickel foam substrate via a hydrothermal electrochemical deposition method. The morphology, composition and structure of the as-prepared film were characterized and the electrochemical performances were tested. The result showed that the as-synthesized Co₉S₈ film displayed a petal-like morphology and possessed excellent capacitive behavior with a specific capacitance of 2538.7 F/g at a discharge current density of 10 mA/cm₂, and retained to 1930.7 F/g even at a higher density of 50 mA/cm₂. After 1000 cycles at 20 mA/cm₂, the specific capacitance of 1825.2 F/g still remained, and the capacitance retention is calculated to be 72.8%. Even after 1500 cycles, the specific capacitance retention could retain to 61.4%.

Abstract:CoCrMoW alloy powder for 3D printing was prepared by vacuum gas atomization. Particle characteristics was studied and the Ell.Elongation, ISO Circularity, Outgrowth were introduced to characterize the particle shape. And the Selective Laser Melting forming properties of the powders and electrochemical properties of the formed parts were studied. Results indicate that the measured D10, D50 and D90 are 12.50 μm, 28.71 μm and 58.05 μm, respectively. Majority powder particles are spherical or near spherical in shape and the mean Ell.Elongation and ISO Circularity are 0.212 and 0.607, respectively. About 74.89% of the powder particles have no adhesion on the surface. The apparent density and tap density are 4.82 g/cm3 and 5.71 g/cm3, the compressibility is 15.6 %. The CoCrMoW powder was used for Selective Laser Melting and the relative density and surface roughness are 98.7% and 8.3 μm, respectively. The microhardness, tensile strength, yield strength and elongation are 396.4 HV, 1154 MPa, 852 MPa and 8.5%, respectively. And the corrosion resistance of CoCrMoW alloy prepared by Selective Laser Melting is better than that of the cast alloy.

Abstract:Pentacarbonyl iron is used as iron source; acetylene is used as carbon source. Ultrafine carbon-encapsulated iron(Fe@C) nanoparticles was successfully synthesized by gaseous detonation method. XRD research carried out for the characterization indicated that the main phase of the detonation product was carbon, α-Fe and γ-Fe; and TEM experiment indicated that the product was ultrafine spherical shape particles and the inner Fe core was coated by a carbon outer shell. The particles have equable size, regular sharp and no agglomeration. The average diameter of Fe core is 4.5nm; Raman spectrum analysis also confirmed that the surface of the nanoparticles was consisted of graphite and amorphous carbon. The carbon-encapsulated iron particles were treated by heat treatment at low vacuum temperature 673K, then we can find the size of iron core particles grows slightly; γ-Fe phase turn to α-Fe phase in XRD and the saturation magnetization is more than doubled after heat treatment

Abstract:Silver-based alloy targets were prepared by self-designed melting-casting-stirring equipment. The influence of Au and Ge on the microstructure and property of silver-based alloy targets were studied. Our results indicated that with the addition of Au and Ge, the microstructure of silver-based alloy targets was refined, the second dendrite was shortened and the sulfidation resistance was increased; Furthermore, when the addition of Au and Ge reached 1.0 wt%, the silver-based alloy targets had best sulfidation resistance. Additionally the phenomenon of element segregation was aggravated with the increased of the addition of Au and Ge. Therefore, a few of clustering enrichment regions appeared at the grain boundaries of Ag1.5Cu0.1Y1.5Au alloy targets and the sulfidation resistance was decreased with the increased of the addition of Au and Ge.

Abstract:Solar cell is currently one of the most promising renewable energy technologies. At present, crystalline silicon (c-Si) solar cell is the most widely used photovoltaic cells and cover 90% market share of the world total PV cell production. Front side Ag paste is a key material in c-Si solar cells because it is the main channel of conducting photocurrent. In general, to gain a higher conversion efficiency for solar cell, the low series resistance and the high short-circuit current is required by optimizing Ag paste and its grid. The rheological behavior is very improtant for Ag paste because it can adjust the screen-printing performace and make the grid has a good morphology to enhance the short circuit current and reduce the series resistance for solar cells. Ethyl cellulose is the most common thickeners, which can be used to adjust the viscosity of pastes. And polyamide wax is an important thixotropic agent that can be used to adjust the rheologic performance of pastess. In this work, The additives ethyl cellulose and polyamide wax of positive Ag paste with different viscosity and rheological behavior was studied to optimize the screen printing performance of the Ag paste, the morphology, densification and resistivity of Ag electrodes. The role of ethyl cellulose and polyamide wax on the viscosity as well as on rheological behavior was different. Ethyl cellulose was mainly used to improve the viscosity of the Ag paste while polyamide wax was used to improve capability of shear-thinning of the Ag paste. Because screen-printing performance is mainly determined by rheological behavior, the ratio of ethyl cellulose over polyamide wax became thus critical. By comparing morphology, densification and resistivity of Ag electrodes, we found the ratio of ethyl cellulose over polyamide wax was 1:5 in our case. Besides, the screen-printing performance of the paste with this ratio is also optimized. The development of new Ag paste and the way of optimizing performance of the Ag paste reported in this paper is very beneficial to further improve the efficiency of current commercial silicon based solar cells.

Abstract:In present work, two kinds of Mg-4Al-2Zn alloy (AZ42) with minor addition of Y elements (0.5, 1.0 wt.%) were succesfully fabricated by gravity casting and rapid solidifaication process, respectively. In addition, microstructure, mechanical properties and corrosion behavior of AZ42 alloys with Y addition were systemetically investigated. The results show that rapid solidification technique can significantly refine the microstructure of AZ42 alloys containing Y and improve related mechanical properties and corrosion resistance compared with the traditional casting counterparts. The microstructure of Y-bearing AZ42 alloy is mainly composed of α-Mg matrix, β-Mg₁₇Al₁₂ phase and Al₂Y phase. Moreover, the addition of Y in AZ42 alloy resulted in grain refinmenent and enhancement of both mechancial and corroison properties, which maybe attributed to fine grain size and distribution modification of β-phase. And the optimum amount of Y element in AZ42 alloy is determined to be 0.5 wt.%.

Abstract:The primary silicon is still rough in hypereuctic Al-Si alloys with the P modification. Aimed at this, the melt stirring is proceeded after the Al-15%Si, Al-18%Si and Al-20%Si alloys were modified by the Cu-9%P alloy, and the influences of the stirring parameters on the modification effect were studied. The mechanism that the melt stirring can improve the modification effect was analyzed. The results show that the melt stirring can obviously enhance the modification effect of hypereuctic Al-Si alloys modified the Cu-P alloy, and the primary silicon can refine the maximum 85%. Within the optimum stirring time, the stronger the stirring is and the higher the silicon content is, the better the modification effect is. The melt stirring compel the AlP in the region of rich P to stop the growth. The faster the velocity of the melt flow is, the stronger the scour of AlP in rich P region is. The easier it is to obtain the fine AlP. The melt stirring can also increase the quantity of the primary α in the microstructure. The typical eutectic structure basically disappears if the stirring parameters are suitable. The microstructure of the tiny primary silicon evenly distributed in the continuous α matrix is obtained.

Abstract:TaCr<sub>2</sub>-xNd<sub>2</sub>O<sub>3</sub> (x=0, 0.125, 0.25, 0.5 and 0.75at%) alloys have been prepared by mechanical alloying + hot pressing. The effects of Nd<sub>2</sub>O<sub>3</sub> on the microstructure and oxidation resistance of te TaCr<sub>2</sub> alloy have been investigated. The results show that Nd<sub>2</sub>O<sub>3</sub> mainly exists in Ta solid solution, and has no significant effect on the phase components and crystal form of the alloy. The alloys are composed of TaCr<sub>2</sub>, a small amount of Ta-rich phase and Cr solid solution. The addition of Nd<sub>2</sub>O<sub>3</sub> reduced the oxidation weight gain of TaCr<sub>2 </sub>alloy at 1200 °C; the oxide film showed a discontinuous multilayer distribution, and Nd<sub>2</sub>O<sub>3</sub> promoted the stratification of the oxide phase.