Abstract:In this work, a hot-rolled and annealed Zr alloy plate with a composition of Zr-1.06Sn-0.36Nb-0.3Fe-0.1Cr-0.13O (wt. %) was compressed along normal direction (0° sample) and transverse direction (90° sample) at 700 ℃ at a strain rate of 1/s. The microstructures and microtextures were characterized by electron backscattered diffraction (EBSD) technique. Visco-plastic self-consistent (VPSC) model was applied to evaluate the activity of slip and twinning systems during deformation at low strain. Microstructure characterization revealed that dynamic recrystallization (DRX) occurs in the two samples. It is found that the texture of the recrystallized grains is similar to that of parent grains, and the preferred nucleation or growth is not in charge of the texture formation. In the 0° sample, all three slip modes (basal, prismatic and pyramidal slip) operate from the first stage of deformation, while a few amount of pyramidal slip is active in the 90° sample in the early stage of deformation. The high activity of prismatic slip results in an intensive <10-10>//RD texture component in the 90° sample. Moreover, predominant basal slip activity at 700 ℃ is necessary to simulate the observed deformed texture.

Abstract:A series of Schmid factor (SF) maps for different slip and twinning modes in Zirconium were systematically calculated and comprehensively illustrated as a function of the tensile angle between the applied stress and the c-axis together with the projective angle on the basal plane. The deformation modes include three groups of slip systems, i.e. basal, prismatic, pyramidal and slips and four groups of twinning systems, i.e.{10-12}, {11-21}, {11-22} and {10-11}. The “soft” and “hard” orientation zones were determined in terms of individual plastic deformation modes. A variant selection criterion for slip and twinning of Zirconium is proposed. The plastic deformation mechanisms are interpreted based on the Schmid factor maps in combination with the experimental data on the critical resolved shear stress (CRSS) for different deformation modes. The predicted plastic deformation mechanisms are consistent with the existing experimental results.

Abstract:Mechanical milling can easily obtain nanopowders and consolidate milled powders to full density. Milling time exerts a critical influence on the performance of powders and bulk materials. In this study, the tungsten (W) combined with niobium (Nb) powder was wet milled for 15, 25, 36, and 45 h, and consolidated by spark plasma sintering. The W-Nb specimens were irradiated with 9.90 × 10₂₄Sions/m₂ helium (He) beams for 11 min. The solid solution degree of W and Nb influences the irradiation damage of the specimen. The surface damage of specimen milled for 36 h which has the lowest solid solution degree is the most serious among all specimens, such that the nanostructure “fuzz” is formed only in the said specimen. In the same specimen, tungsten presents different surface damage degrees owing to its different orientations. After characterization, the W-Nb specimens were isochronally annealed at 900, 1100, and 1300 °C for 1 h. The grains grow in Nb but barely change in W. Nb exerts a strong influence on the right shifting of He desorption peaks.

Abstract:Titanium-Zirconium-Molybdenum (TZM) alloy as the plasma facing material (PFM) will continue to be used in large quantities in the Experimental Advanced Superconducting Tokamak (EAST) device. Research and analysis of heat absorption ratio of TZM will have high reference for the later selection of PFM. In this paper, the heat absorption ratio of TZM in rolled and forged state is tested by the e-beam device of Shenzhen University, and the relevant experimental results were analyzed. It shows that the heat absorption ratio of TZM in both rolled and forged state is about 0.7, and it is not affected by the change of cooling effect and high temperature of the material. This work will be very helpful in judging the safety of TZM, which is important for long-term development of EAST. And it will also have important reference for the future construction of CFETR.

Abstract:The interfacial microstructure and joining properties of Titanium-Zirconium-Molybdenum (TZM) alloy joints were characterized by SEM, EDS, XRD and mechanical tests, etc. The results showed that the Ni-Ti brazing filler metal can efficiently realize high-temperature vacuum brazing of TZM. The formation MoNi₄ phase from Mo of the base metal and Ni in the braze metal was the main reason for the metallurgical bond between the TZM and the Ni-13.7Ti / TZM interface region. Ti in Ni-44Ti braze metal dissolved in Mo to form an infinite solid solution in TZM / Ni-44Ti / TZM interface zone, forming a metallurgical bond between the braze metal and TZM. However, a serious inter-granular infiltration phenomenon was observed when Ni-44Ti braze alloy was used to braze TZM alloy. The degree of inter-granular infiltration and corrosion of the base material significantly reduced with a decrease of Ti content in the braze alloy. The average shear strength of TZM / Ni-13.7Ti / TZM brazed joints reached 193 MPa, while the average shear strength of TZM/Ni-44Ti/TZM brazed joints reached 167 MPa. The lower shear strength of TZM/Ni-44Ti/TZM was attributed to the inter-granular infiltration due to the higher content of Ti in the brazing filler.

Abstract:The influence of rolling reduction and temperatures at room and liquid nitrogen on the formation of deformation-induced martensite and microstructural evolution in a β-ZrTiAlV alloy was investigated by X-ray diffraction (XRD), optical microscopy (OM) and electron backscatter diffraction (EBSD) technique. The analysis of the phase composition and microstructure of the rolled alloy indicated that a deformation-induced martensite phase transformation process from body-centered cubic β to closed-packed hexagonal α＇accompanying with (102) <110> twinning in the α＇phase were simultaneously detected. With the increase of rolling reduction, deformation-induced phase transformation and the volume fraction of martensite variant were promoted. Nevertheless, lower temperature (liquid nitrogen) resulted in the inhibition of α＇martensite transformation and the promotion of the (102) <110> twinning. When the specimen was subjected to the rolling reduction of 5%, plate-like deformation-induced martensite started appearing in the equiaxed parent β grains. However, when the rolling reduction increased to 10%, the deformation-induced martensite would be generated fully within some β grains.

Abstract:Crystallographic orientation and microstructure of the 0.5mm thick cold-rolled annealed molybdenum sheets for vacuum electron devices were analysed by electron back-scattered diffraction (EBSD) and metallography, and their correlation with mechanical performance was discussed. The molybdenum sheets with excellent processability have some characteristics: grain orientation distribution which is relatively weaker and more diffused, mainly consists of α-fiber and γ-fiber texture. In the α-fiber texture, rotation cubic {001}<110> is the maximum component, and an amount of {112}<110> exists. Observed microstructures are mostly flat cloud-flake grains arrayed orderly along rolling direction and paralleled to rolling surface. Relatively less high-angle boundaries with θ> 50° are detected. Therefore, the Mo sheets show higher yield ratio and elongation, and weaker elongation anisotropy in RD, TD, and 45°-RD directions, i.e. excellent strength and toughness matching.

Abstract:Electrolytic hydrogenation was carried out on two kinds of newly developed zirconium alloy (SZA-4 and SZA-6) tubes, and the effects on the hydrogen absorption properties and mechanism were investigated. The results showed that the hydrogen absorption tendency of SZA-4 alloy was higher than that of SZA-6 alloy under the as-received condition, while, after the recrystallization annealing, the hydrogen absorption tendency of SZA-4 alloy reduced, and the hydrogen absorption tendency of SZA-6 alloy increased. As a result, the hydrogen absorption tendency of SZA-6 alloy was higher than that of SZA-4 alloy, and both of them have a higher hydrogen absorption tendency than that of the traditional Zr-4 alloy. The changes of the hydrogen absorption tendency of SZA-4 and SZA-6 zirconium alloys were related to the precipitation of SPPs. A large amount of (Zr,Nb)2Fe SPPs precipitated with fcc crystal structure in the SZA-6 alloy after recrystallization annealing lead to the hydrogen absorption tendency increasing.

Abstract:The Low cycle fatigue properties of the commercially pure zirconium (CP-Zr) were investigated by a method under axial loading controlled by symmetric strain. The characteristics of cyclic stress-strain response and hysteresis loop of CP-Zr were discussed. Cycle softening and hardening characteristics and cumulative hysteresis of the CP-Zr were analyzed and then the fatigue life was predicted. The results indicate that the CP-Zr displays cyclic hardening when the total strain amplitude is more than 0.5%. The fatigue life of CP-Zr matches Basquin-Coffin-Manson"s empirical relationship, whose transitional life is 1548 cycles. And the plastic strain energy can be suitably utilized as an essential parameter in fatigue failure model to evaluate the fatigue damage. The hysteresis loop area (i.e. the plastic strain energy) decreases with the total strain amplitude decreasing and the number of fatigue cycles increasing. The fatigue striation can be obviously observed, as the total strain amplitude increases, the number of fatigue striation decreases and the width increases.

Abstract:The precipitation behavior of second phase particles (SPPs) of Zr-Sn-Nb-Fe-Cr-Cu alloy after 6% and 12% pre-compressed deformation during aging was investigated by scanning electron microscope (SEM) and transmission electron microscope (TEM). It was found that the pre-deformation has a marked influence on precipitation behavior of Zr alloy. The average size of SPPs of 12% pre-compressed deformation samples was about 10nm larger than that of 6% pre-compressed deformation; and the average size of SPPs was linearly inversely proportional to the volume fraction of pre-deformation when the alloy was aging at 600℃. From TEM observation, the precipitates of orthorhombic Zr3Fe containing Cu element were detected when Zr alloys were aged at 550℃ for 30 minutes; the precipitates of hexagonal Zr(Fe,Nb)2 were also found with smaller size to Zr3Fe when the aging time prolonged to 1800 minutes. The pre-deformation has no remarkable impact on the type of SPPs.

Abstract:The surface mechanical attrition treatment was used to process the commercial pure zirconium and the fatigue properties of the samples were examined by four-point bending fatigue test. By observing the microstructure, characterizing the microhardness and residual stress, and combining the finite element method simulation of the stress distribution in the four-point bending specimen, the effect of surface nanocrystalline on the fatigue property was analyzed. The results show that the fatigue limit of the surface nanostructured commercial pure zirconium increases by about 23% compared with the original sample. This is due to the fact that the maximum tensile stress of the original sample under loading is located at the surface region, which leads to the initiation of fatigue cracks in the surface layer. For the surface nanostructured sample, the microstructure strengthening effect and residual compressive stress are beneficail for the fatigue performance. In addition, crack source was shifted to the subsurface layer because of the high strength of the surface layer. Therefore, the surface nanostructured commercial pure zirconium samples possess better fatigue properties.

Abstract:Pure tungsten specimens were prepared by additive manufacturing of selective electron beam melting(SEBM). The heat transfer process during SEBM and microstructure characteristics of pure tungsten were analyzed. The results show that the microstructure is columnar crystal grown in the form of epitaxial growth. In the inner side of the sample, the heat conduction along the building direction of the sample is dominant. The columnar crystal growth direction is opposite to the heat flow direction, forming a cylindrical crystal with complete vertical growth; In the outer side of the sample, the heat conduction are the joint action of conduction along the building direction and conduction to the powder bed. This makes the direction of the heat conduction deviate from the building direction, so the columnar crystal is 30-45_⁰ angle with the building direction. Furthermore, the preferred orientation of [111] and [100] is formed along the building direction in the SEBM pure tungsten.

Abstract:The service performance and effects of the different details of spun molybdenum crucible on sapphire crystal structure and during the preparation of sapphire single crystal were analyzed, based on which the failure forms and elements of quality control of spun molybdenum crucible were proposed. The hot multi-spinning processing of shearing and rheological deformation of molybdenum plate was developed, and its processing parameters, including spinning wheel load factors (roller forming angle α&lt;sub&gt;0&lt;/sub&gt;, roller radius D&lt;sub&gt;ρ&lt;/sub&gt;, roller radius ρ and angle adjusting angle β), wall thinning rate ψ&lt;sub&gt;t&lt;/sub&gt;, roller feed f, core mould - roller clearance δ, spindle speed n, spinning temperature, heating method, annealing temperature and annealing time, were experimentally studied. The quality affecting factors and causes and solutions of molybdenum crucible, including outer and inner cracks in bottom corners, deep burrs in outside surface of side walls, cracks in open ends, collapsed bottom corner, insufficient wall thickness, circumferential uneven thickness and size errors in open ends, were comprehensively discussed. Meanwhile the evolution law of microstructure during the spinning process of molybdenum metal was presented.

Abstract:Spherical powder has been widely used in injection molding, spraying, additive manufacturing and other fields due to its good flowability, high apparent density and tap density. The irregular tungsten powder was selected as raw materials to preparing spherical tungsten powder by radio frequency plasma system, and the effect of spherical tungsten powder was evaluated by laying powder and forming result. In the process of preparing spherical tungsten powder, the effects of process parameters (feeding rate, feeding position) and raw tungsten powder on spheroidization results were studied. In the aspect of laying powder experiment, the effect of powder characteristics and layer thickness on laying powder effect were studied. The morphologies, particle size distribution, flowability, apparent density and tap density of the tungsten powder before and after spheroidization were characterized by scanning electron microscopy (SEM), laser micron sizer, BT-100 multifuctional powder physical property tester. The results showed that tungsten powder was regularly spherical and had smooth surface after spheroidization, and the spheroidization rate can reach 100%. And the flowability, apparent density and tap density were improved obviously. The better the flowability of spherical tungsten powder with high spheroidizing rate, the better the effect of laying powder. With the increase of layer thickness, the effect of laying powder was improved gradually. And thin-walled parts were prepared by spherical tungsten powder of suitable particle size had low surface roughness and high dimensional accuracy.

Abstract:The cladding tubes of a newly designed SZA-4 zirconium alloy of Zr-Sn-Nb system were hydrided using electrolytic hydrogen charging technique. The effect of electrolytic hydrogen charging time on the hydrogen absorption amount and the type and the distribution of hydrides, as well as the effect of homogenization annealing time on the type and the distribution of hydrides in SZA-4 zirconium alloy were investigated. The results showed that the hydrogen absorption amount of samples increased with the hydrogen charging time, and a parabola relationship between hydrogen absorption amount and hydrogen charging time was found. Microstructure analysis showed that the hydride layers were formed on the surface of the samples after electrolytic hydrogen charging, while the inner part remained the zirconium alloy matrix. And the thickness of the hydride layers increased with the increase of hydrogen charging time. The phase structure analysis showed that the hydride layer was merely composed of δ-ZrH_1.66 at the beginning and increased with hydrogen charging time. When hydrogen charging time reached 24 hours, the hydride layer was composed of ε-ZrH_1.801 and δ-ZrH_1.66 phase. After 400 ℃/6 h homogenization annealing, the thickness of the hydride layer of hydriding samples further increased, and platelet-like hydrides precipitates within the tubes along the circumferential direction were found. The phase structures analysis of the homogenization annealing of hydriding samples showed that ε-ZrH_1.801 disappeared and the original δ-ZrH_1.66 hydride transformed into δ-ZrH_1.5 hydride in hydride layers. And after 400 ℃/96 h homogenization annealing treatment, all of hydride layers disappeared, and thin platelet-like hydrides were evenly distributed in the samples.

Abstract:Ultrafine-grained commercially pure Zr (UFG Zr) was fabricated by equal channel angular pressing (ECAP) coupled with subsequent rotary swaging (RS). Tensile properties and fatigue performance of the commercially pure Zr with ultrafine-grained microstructure were investigated, and these results were compared with those of the commercially pure Zr with coarse-grained counterpart. Fracture surfaces were examined to study the fatigue fracture failure mechanism using SEM. The result shows that ultimate tensile strength of UFG Zr is obviously higher than that of the coarse-grained Zr (CG Zr) at room temperature, while the CG Zr exhibits a higher fracture elongation. Fatigue life of UFG Zr is significant higher than that of CG Zr. The relationship between the applied stress (σa) and cycles to failure (Nf) was determined as: σa=750 Nf -0.06. The conditional fatigue limit of UFG Zr is about 285 MPa, which is improved by 70% compared with that of CG Zr. The fractography analysis reveals that fatigue cracks mainly initiate from the surface of the UFG Zr specimen. The spacing of the fatigue striations of UFG Zr is smaller than that of CG Zr, which indicates that the crack propagation rate of UFG Zr is lower than that of CG Zr.

Abstract:In this paper, 90W-7Ni-3Fe heavy alloy thin plate, with the thickness less than 0.1 mm,was prepared by the process of tape-casting, laminating, rubber discharging, sintering and cold rolling. Scanning electron microscope was used to observe the tapes.The mixed metal particles were evenly distributed in the binder. Comprehensive thermal analysis is carried out to get the binder remove scheme. The result of the carbon / sulfur analysis showed that the binder in WNiFe alloy is almost removed, the carbon content is 0.012-0.018wt%. By analyzing the morphology,relative density and hardness of 90W-7Ni-3Fe plates with different sintering temperatures, it was investigated that when the sintering temperature at 1450℃, the degree of densification was increased and the grain size of W was not grown too large. The sintered 90W-7Ni-3Fe plates were treated by cold rolling, the W grains were elongated into the oblate ellipsoidal shape along the rolling direction, and the Ni-Fe phase which has better toughness than W grains was also stretched and lengthened in the rolling direction, pores were eliminated. the density and hardness of the plate were effectively increased.

Abstract:NbMoTaW high entropy alloy powders were prepared by mechanical alloying. The effects of milling time on the powder phase structure, microstructure, impurity content and particle size were studied. X-ray diffraction, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to analyze the phase and morphology of the high-entropy alloy powder. The element distribution and impurity content in the powder were quantitatively analyzed by the energy spectrum analyzer. The particle size distribution of the powder was measured by the laser particle size distribution tester. The results show that themixed powder undergoes three stages with milling time increasing: flattening, cold welding breakage, and sphericity.After 45 h ball milling, the powder formed a single BCC solid solution. The powder morphology changes from an initial irregular shape to a sheet shape, and then it changes into an ellipsoidal shape, and the sphericity is gradually optimized. The impurities mainly originate from the agate jar and the grinding ball. Different ball milling time periods have different impurity content growth rates. Particle size changes with milling time, showing a trend of increasing first and then decreasing, and the particle size distribution is more uniform.

Abstract:Stress corrosion crack (SCC) of small crack has an important effect on the whole-life attenuation process of critical structures in nuclear power plants (NPPs). By combining the film slip-dissolution/oxidation model with the elastic-plastic finite element method (EPFEM), the quantitatively predicting of SCC propagation rate for small crack in reactor pressure vessels (RPVs) of NPPs. According to the crack tip mechanical field analysis, the crack tip strain rate is determined to control the initiation and propagation of small cracks, and it is approximately calculated by the variation of plastic strain (de_p/da) at a characteristic distance r₀ in front of a growing small crack tip. Two methods of dynamic crack propagation method and quasi-static crack propagation method based on EPFEM were proposed to calculate the variation of plastic strain (de_p/da). The contrast of the two calculation method and the sensitivity analysis of variation of plastic strain to the crack length were carried out, which concludes that the slight differences between the two methods, and the plastic strain variation are more sensitive to crack propagation with small crack than that of long crack. The SCC propagation rate of small cracks is larger than that of long cracks, and it is significantly influenced by the characteristic distance r₀. As it is difficult to determine the value of characteristic distance r₀ finally due to the unclear of its meaning, it is suggested to be determined by combining experimental SCC data with a finite element simulation of the single-edge crack panel specimens under the same environmental and material conditions. The approach proposed in this paper is expected to quantitatively predict SCC propagation rate in core materials and evaluating SCC propagation in key structural components in NPPs.

Abstract:Static load tensile test is the most widely used mechanical properties test. In this paper, it is tried to reveal that the influence of the presence of laser welded joint on the deformation behavior of the specimen by comparing the thermal effects of TC4 base metal and joint specimen during tensile test by infrared thermograph method. The results show that for joint and base metal specimens with the same tensile strength, there are many differences in the thermal effect, such as the beginning times of the physical yield phenomenon and the corresponding stresses, the temperature distribution and evolution process.

Abstract:PdAg films with self-supported porous dendritic walls were fabricated by hydrogen dynamic template method, which could provide as the transport channel due to the micron-sized pores and the interstices between the dendrites. Different composition PdAg catalysts were obtained by adjusting the proportion of Pd(NO₃)₂ and AgNO₃ and it was also studied that the effect of the addition of Ag on the catalytic performance for ethanol. The cyclic voltammetry (CV) curves showed that PdAg films possessed high catalytic activity for ethanol and the addition of Ag significantly increased the mass-normalized catalytic activity of Pd. The mass-normalized catalytic current density of porous Pd₅₁Ag₄₉ is 0.49 A/mg, and it was estimated as 1.47 times as porous Pd. X-ray photoelectron spectroscopy (XPS) study indicated that the enhancement of the catalytic activity of PdAg films could be ascribed to the change of the Pd electronic structure when Ag atoms are embedded into the Pd lattice to form PdAg alloy as shown in X-ray diffraction(XRD) and element analysis mapping (EM) results.

Abstract:The phase?transformation process form 25°C to 1450°C and magnetic properties of Sr0.3La0.3Ca0.4Fe10.625Co0.225Zn0.1O19 were investigated by means of high-temperature X-ray diffraction, thermal analysis, vibrating sample magnetometer and scanning electron microscopy. The formation of M-type hexagonal ferrites in air passes through two endothermal reactions. SrCO3 and partial Fe2O3 first generated the intermediate phase Sr3Fe2O7-d in around 700°C. And then Sr3Fe2O7-d and the remaining unreacted Fe2O3 generated SrFe12O19. Meanwhile, La3+, Ca2+, Co2+ and Zn2+ ions gradually dissolve in the intermediate phase or the late product M phase with the temperature increases. The perovskite was obtained when annealed at about 700°C, which may transform perovskite into Sr3Fe2O7-d during the cooling process. The average valence of Fe in Sr3Fe2O7-d was a function of temperature. A very high single degree of M phase and a small number of second phase were obtained at about 1200°C, and the cationic were evenly distributed in the crystal. The rectangularity of the demagnetizing curves of the LaCaCoZn-type substituted ferrite powder decreases compared to that of unsubstituted ferrite powder. The ferrite will be decomposed at about 1380°C.

Abstract:Grain boundary character distributions (GBCDs) have been measured for both Σ13a and Σ2 coincidence site lattice (CSL) boundaries in WC-Co composites under plastic deformation condition via five parameter analysis (FPA) method. For the two CSL boundaries, compared to the cases in the undeformed sample, both populations and the habit plane occurrence frequencies of the CSL boundaries decreased in the plastic deformed sample. The interpretation about the evolution of GBCDs during plastic deformation is proposed based on the fine-sorted crystallographic plane categories.

Abstract:During horizontal lapped deposition with solidification of an aluminum molten droplet onto an aluminum substrate, the effects of the surface morphology and interior quality of the specimens under different process parameters were studied in this paper. By research of the single metal droplet deposition behavior, the horizontal lapped deposition of numerical model was established, and the evolution of morphology and temperature of one, two, three and four molten droplets horizontal lapped deposition impacting a substrate surface at different time respectively and multiple droplets successively deposition experiments under the different simulation parameters were carried out. In order to confirm the numerical simulations and experimental verification, the comparison between numerical simulations and experiments shows a good agreement. The optimal parameters are obtained. This investigation is essential to implement effective process control in metal micro-droplet deposition manufacture and it provides technical support and reference for the complex metal parts of molten droplets horizontal lapped deposition process.

Abstract:The aim of this work is to study how applied voltage in stages incorporates into the prepared micro arc oxidation (MAO) coatings on titanium and control the characteristics and resistances. The microstructure of MAO coatings were characterized by scanning electron microscope (SEM) and laser scanning confocal microscopy, and the coating composition were analyzed by energy dispersive spectrometer (EDS) and X-Ray diffraction (XRD). Thickness, roughness and corrosion resistance of coatings were evaluated. Compared with the coating obtained in different applied voltage stages, the coating formed on substrate alloy with first applied voltage is 320V for 180s and second applied stage is 420V for 720s showed a minimal roughness. The coating with first applied voltage is 320V for 120s and second applied stage is 420V for 780s exhibits a dense micro structure and the best corrosion resistance. The XRD result shows that the MAO coating is composed with TiO2 and Ti2O3 in metastable state.

Abstract:The reactive elements (RE), such as Y, Hf, Zr and Ce (or their oxides), are added into the aluminide coatings to improve the oxidation resistance of coatings. In this work, the δ-Ni2Al3/Ni coating systems with different CeO2 contents and particle sizes were specially prepared by partially aluminizing the Ni films containing ~0, ~1, ~2 and ~3 wt. % nanometer CeO2 (15-30 nm) and ~1 wt. % micrometer CeO2 (5 μm), respectively. The effects of CeO2 contents and particle sizes on the interdiffusion of the aluminide coating and underlying substrate were investigated by annealing in vacuum at 1000 °C. The results showed that the addition of nanometer CeO2 in the δ-Ni2Al3/Ni coating system could mitigate the interdiffusion between the aluminide coating and underlying substrate and the blocking effect can be significantly improved with the increase of the CeO2 contents which is 1-3 wt. %. However, the addition of micrometer CeO2 in the coating system had little influence on the degradation of the aluminide coating. This is intrinsically correlated with the fact that the CeO2 contents and particle sizes would influence the formation of the CeO2-rich layer at aluminide/Ni film interface acting as a diffusion barrier between the aluminide coating and substrate.

Abstract:With the constant upgrading of traditional and strategic emerging industries, carbon and graphite materials (CGM) has become an important strategic resource and essential mineral material to support the development of high and new technology. The current situation of report for the CGM still remains at macro-mechanical properties, Seldom?is?reported?about pore structure of CGM, which may affect on mechanical properties. It is well known that properties of CGM depends on its micro-structure, and the pore structure plays an important role on micro-structure. Therefore, this paper reviews the development and application of CGM, and parameters of pore structure in CGM. Moreover, the effect of parameters characterizing of CGM’s material pore structure on comprehensive properties are described and the correlation between them also are discussed. It provides a theoretical basis for material scientific description of physical and chemical properties, material modification, performance optimization and new process design.

Abstract:Isothermal hot compression tests of a new marine titanium alloy Ti80 were conducted on a Gleeble-3500 thermal simulator. The variation of flow stress under different processing parameters was studied and elevated temperature constitutive equation and processing map were established. Based on the analysis of high power dissipation efficiency in safe region, the initial temperature of bar stock was preliminary determined as Ti80 alloy seamless tube was prepared through rotary piercing process. Finally, the judgment was proven by 3D thermo-mechanical coupled simulation as well as physical experiment. The results show that the flow stress of Ti80 alloy varies with sensitivity of the temperature under different strain rate. The stress will increase sharply with decreasing temperature in α+β phase field; while has slight difference in single β phase field. Taking strain compensation into consideration, the modified hyperbolic-sine Arrhenius type equation could give an accurate estimation of flow stress for hot deformation of Ti80 titanium alloy. The developed processing map shows two high power dissipation efficiency domains, one is in α+β phase field with low strain rate, i.e. 925-975℃/0.01-0.1s_-1; the other is in the β regime with intermediate strain rate, i.e. 1050-1100℃/0.1-1s_-1. Finite element simulation for rotary piercing process was further conducted at initial temperature of 950, 1050 and 1100℃ for bar stocks. It is found that the plug force at temperature of 950℃ increases significantly about 4-5 times to that at temperatures in single β phase field, and what is worse, piercing in α+β phase field leads to rolled stock jamming in Diescher mill. However, the piercing process in β phase field can be conducted well. For reducing energy consumption, the temperature of 1050℃ is considered as the optimal choices. In the end, Ti80 alloy seamless tube was produced successfully in Diescher mill.

Abstract:The residual stresses in the ring forgings were tested and described using radar charts. The effects of bulging process forming on residual stress and distribution along ciucumference were analyzed. The results show that radar charts can be used to describe effectively the values and distributions of residual stresses along ciucumference for the ring forgings. And the bulging process forming is an effective way to adjust the residual stress and distribution in the ring forgings. For the ring forgins in this paper, residule stresses are compressive stress and in the range of -50~-150MPa. A sharp area exists in each radar chart and is weakened after bulging process forming. The hoop stresses are relaxed much more than the axial stress and especially on the inner and bottom end surface about 24.8% and 20.2%. The distribution uniformity of residul stress is improved except for the bottom end surface.

Abstract:The Berkovich indenter was selected to perform an varied load nano-scratching experiment for monocrystalline Germanium by using nano indentation test. The surface morphology of the groove was observed by SEM, which was found that there are three regimes in nano scratching process, i.e. the ductile regime, the brittle-ductile transition regime and the brittle regime, and the mechanical characteristics at each regime was analyzed. According to the theory of fracture mechanics, the first drop of tangential force was taken as the occurrence point of brittle-ductile transition, thus the critical load and critical depth for monocrystalline Germanium were obtained, and the crack generation and propagation process were also analyzed. Non-linear fitting method was used to figure out relationship between normal force, tangential force, friction factor and scratch depth respectively during nano-scratching process, the calculation results of the correlation coefficient show that there is a strong correlation between scratch force and scratch depth. Based on the Hertzian contact theory, the critical elastic-plastic transition depth during the scratch process for monocrystalline Germanium is calculated, and the value is 1.2 nm. Based on the critical load of brittle-ductile transition, An equation for characterizing the phenomenon is established, the results show that the transition depth is 561 nm. Therefore, a quantitative method for distinguishing different regimes of monocrystalline Germanium is established.

Abstract:The deformation behavior of Al-Zn-Mg-Cu alloy during equal channel angular dual-directional extrusion （ECADE） processing was studied by means of numerical simulation and experiments. The results show that the ECADE process can be divided into three stages: local upsetting, shearing deformation and final filling. Also, the processed sample can divided into undeformed zone, small deformation zone, shear deformation zone and severe deformation zone according to the metal flow and mesh distortion. Different loading ways of the upper and lower punches lead to the deviation of deformation zone, and the sample has less deformation homogeneity along with the more velocity difference between the two punches. The most homogeneous deformation with maximum strain of 3.97 and deformation uniformity coefficient of 1.89 was obtained while the velocity ratio was 1: 1. In addition, the deformation behavior under different routes was investigated. It is found that the deformation is more homogeneous under 4 passes of route B compared with route A, having a 29 % reduction in deformation uniformity coefficient and a 14 % increase in shear deformation zone proportion.

Abstract:Multi-directional forging (MDF) process with different cycles was conducted on the Ti2AlNb-based alloy under the temperature of 800℃ in the (B2+O) phase region followed by water cooling. The microstructure was characterized by electron backscatter diffraction(EBSD) and X-ray diffraction (XRD), the effect of MDF process cycles on microstructure evolution of Ti2AlNb-based alloy was analyzed. The experimental results show that the microstructure is significantly refined to submicrometer, the misorientation of grain boundaries has the transforamtion from low angle to high angle and the equiaxed ultrafine grains with high angle boundaries are obtained after MDF processing. The grain size decrease raplidly after one cycle of MDF and the value keeps nearly constant with the increasing number of MDF cycles. After deformation, the major phases of the alloy are B2+O, as well as some residual ɑ₂ phase. The content of ɑ₂ phase decreases while the O phase increases compared to the initial sample. In addition, the microstrain and dislocation density increase significantly after deformation. Because of dynamic recovery, the microstrain saturates to a stability level with the number of cycles increasing, while the dislocation density experiences a slight decrease.

Abstract:La-F two-step co-doping TiO2 photocatalysts have been prepared by the means of in-situ doping method using tetrabutyl titanate, lanthanum nitrate, and sodium fluoride as the main materials. The prepared samples have been characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and UV-Vis diffuse reflectance spectra (UV-Vis DRS). The photocatalytic property under visible light was evaluated by the photo degradation of Methylene blue (MB). In addition, by means of electrochemical impedance spectroscopy (EIS), the carriers concentrations of co-doping samples were calculated through Mott-schottky equation to discuss the mechanism of two-step co-doping. The results demonstrated that all the samples exhibit homogeneous anatase TiO2, La-F co-doping led to larger lattice distortion and refined the grain size of TiO2. SEM results showed that the morphology of samples were spherical in shape but the aggregation degree was different with each other, and the two-step co-doping could aggravate the reunion of the sample particles compared with that of the co-doping samples because of the difference of their preparation process. The La-F co-doping also could cause the absorption band of samples shifted towards the longer wavelength side and the band gap decreased accordingly at the same time. Simultaneously, n-n heterojunction was formed between TiO2 and Lax-Fy-TiO2 in the two-step co-doping TiO2 samples. The build-in internal electric field caused by the different Fermi level of TiO2 and Lax-Fy-TiO2 played an important role in the directional migration of charges in the two-step co-doping samples, and reduced its recombination of photo-generated electron and hole effectively, and then enhanced the charge carrier concentration. As showed in the electrochemical impedance results, when the doping ratio of La and F in the two-step La-F co-doping sample were 1.5% and 10% respectively, the carrier concentration reached 1.5×1020/cm-3, and it’s degradation rate of methylene blue under visible light is 96% at 120min, which was 2.6 times of pure TiO2 on the same condition.

Abstract:A prepared method of Cu-doped TiO2 nanotubes(Cu-TNT) was proposed in this paper, which combined sputtering and anodic oxidation. Scanning electron microscopy (SEM), X-ray diffraction (XRD), Transmission Electron Microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) were used to study the structural and photoelectric properties of TNT. Cu-doped inhibited the growth of nanotubes, and excessive Cu-doped had a significant effect on the morphology of nanotubes. The position of Ti ion in the lattices of TiO2 nanotubes was replaced by the Cu ion., which made the (101) crystal faces a crystal lattice distortion, and the crystal plane spacings became wilder. The addition of Cu ions affected the growth orientation of the nanotubes, inhibited the growth of anatase (101) crystal plane and promoted the preferential growth of anatase (004) crystal plane. Transient photocurrent respons analysis showed that the recombination of photoelectron-hole pairs were effectively suppressed, and would improve the utilization ratio of solar light. Keywords: Cu-doped TiO2 nanotubes, anodic oxidation, sputtering

Abstract:In this paper, Cu-Nb microcomposite (8 #) with 7 cores reinforced by graphene coated with niobium powder and reinforced by pure niobium powder (9#) with 7 cores were successfully prepared by accumulative drawing and bundling process.The breakage phenomenon of wire in plastic processing has been significantly improved after the optimization of heat treatment process, especially the wire (8 #) reinforced by graphene coated with niobium powder,which have a regular uniform distribution of the core and a good coordination.Through the analysis of the microstructure, mechanical properties and electrical properties of two kinds of wire with different sizes (Φ2.49mm, Φ2.29mm, Φ2.02mm, Φ1.84mm), the results show that the mechanical properties of Cu-Nb wire reinforced by graphene coated with niobium powder increased only tens of MPa that compared with reinforced by pure niobium powder, however,the conductivity of the Cu-Nb wire increased obviously, which reached 10 IACS%.Finally, the plastic deformation mechanism of two kinds of wires were analyzed.

Abstract:The microstructure of CuAgNi filler metals and Tungsten-based powder alloy brazing joints has been observed by OM, SEM and XRD, to compare and analyze the high temperature shear strength of tungsten based powder alloy joints brazed with CuAg and CuAgNi filler metals, and the thermal fatigue properties of the brazed joints of CuAgNi brazed filler metal are further analyzed. It is investigated that Ni has promoted the shear strength of brazed joints at room temperature and high temperature. When the temperature is close to room temperature, the shear strength of the brazed joint is 214.7 MPa, which is 32.37% higher than that without Ni. At 400 °C, the shear strength is 121.9 MPa, which is 91.67% higher than that without Ni. Moreover, when the temperature is beyond 300 ° C, the oxidation of the bonding interface causes the bonding strength of the joint to drastically decrease. In the thermal fatigue test, as the number of thermal cycles increase, the cracks gradually expand after the initiation of α-Ag and β-Cu bonding, which gradually reduces the shear strength of the joint.

Abstract:_{:. The effects of Cr content on the microstructures, phases, tensile properties and impact properties of the Ti-Al-V-Zr alloys with addition of 0.76%~1.52%Cr were investigated for nucleus applications. Microstructural analyses were carried out using scanning microscopy,SX-ray diffractionSand quantitative microprobe analysis。Additions of Cr refined the microstructure of such modified alloys, but the microstructure with the amount of 0.76wt% Cr was markedly smaller in comparison with others.XRD results that the total amount of β phase increased with Cr increased at 1.52wt%. Cr additions improved significantly the strength significantly but not improved the plasticityof the modified alloys. T2 alloy has much higher value of the impact toughness and energy among all the studied the alloys. The experimental results indicate that the fracture in Ti-Al-V-Zr alloysinfluencedby Cr additions considering the influence of the number and the shape of the secondαphase. They have the great potential to become new candidates for nucleus applications.}

Abstract:With iron powder and aluminum powder as raw material, the rotating viscometer was used to measure the change of the viscosity of the slurry during the gelation process to investigate the gelation behavior to obtain high quality of the green body. The results show that: The increase of the initiator content, monomer content and reaction temperature will decrease both the idle time and the reaction time. The increase of catalyst content will significantly decrease the idle time while it has less impact on the reaction time. In turn, the reduction of the volume ratio of the monomer to the crosslinker reduces the reaction time, but has no influence on the idle time. Combined with the analysis of slurry stability, the idle time and reaction time can be control in range of 71~748 s and 154~714 s to realize the controllable gelation of products with different size and complexity by verifying the initiator content, the catalyst content, the reaction temperature, the monomer content and the volume ratio of the monomer to the crosslinker. the effects of these parameters on the idle time and reaction time has been systematically investigated. The controllable gelation can be realized by adjusting the idle time and the reaction time. Porous FeAl intermetallics with uniform pore structure, open porosity of 57.6 %, pore size below 10 μm, compressive strength of 40.7 MPa and complex shape fabricated by gel casting successfully match the demand of gas separation.

Abstract:In order to study effect of pulse current frequency on microstructure and mechanical properties of TC4 titanium alloys with prefabricated defects, TC4 specimens with void defects were firstly prepared by pre-stretching at room temperature and then treated by pulse current with different frequencies. Microstructural variations of void and matrix before and after pulse current treatment were compared. Mechanical properties were obtained by second room-temperature tension. The results indicate void volume fraction decreases from 2.21% to 0.86% when pulse frequency increases from 0 to 140Hz. Meanwhile, yield strength and ultimate tensile strength rise from 916.7MPa to 990.9MPa and from 951.2MPa to 997.5MPa, respectively. Moreover, the elongation increases by 64.86%. However, void volume fraction increases to 1.99% when pulse frequency increases from 140Hz to 160Hz. At the same time, yield strength and ultimate tensile strength decrease to 975.1MPa and 988.5MPa, separately. The elongation decreases by 37.70%. Void volume fraction almost determines mechanical properties of TC4 alloys with prefabricated defects.

Abstract:The effect of final thermo-mechanical treatment on the microstructure and property of Al-5.2Mg-3.1Zn(wt.%) aluminum alloy have been studied. The effect of deformation parameter on the final aging treatment has been studied by Vickers hardness tests. Observations under optical microscopy and transmission electron microscopy show that there are lots of dislocation structure and fibrous structure in the microstructure, and their volume fractions depend on the deformation parameter. The tensile test reveals that higher deformation temperature benefits the higher strength of sheets, but decreases the elongation. However, the amount of deformation has the completely oppsite effect on the tensile property. The increase of deformation temperature and deformation amount both increase the intergranular corrosion resistance of sheets.

Abstract:Terbium/zinc antibacterial silica gel was prepared by sol-gel method. The better preparation conditions were obtained by controlling single factor variable experiments: The concentration of zinc ion 0.8 mol·L-1，the rare earth terbium concentration 0.003 mol·L-1 and reaction time 1 h. And as-prepared materials were characterized by X-ray diffraction (XRD)，scanning electron microscopy (SEM)，X-ray photoelectron spectroscopy (XPS) andinductive coupled plasma emission spectrometer(ICP) analyses. The results showed that this antibacterial silica gel was amorphous，and its structure was fluffy and porous. The presence of homogeneously mixed zinc and terbium, in the form of ZnO and Tb2O3. The ICP analysis resulted in 1.82% of Zn and 0.073% of Tb Antibacterial test results showed that the material had an inhibitory effect on the growth rate of E.coli. The antibacterial rate of the material after adding rare earth terbium increased from 72% to 87%. Synergistic antibacterial effect of rare earth on materials was judged by synergistic effect factor (SEF) and synergy coefficient (T/E)，terbium was a synergistic antimicrobial agent in materials. The synergistic antimicrobial mechanism of rare earth was preliminarily analyzed through the results of the specific surface area, pore size and the loading capacity of zinc ions.

Abstract:Microstructure and hardness of Two β TiAl alloys, with nominal composition of Ti-42.5Al-2Cr-0.2W-3Ta and Ti-42.5Al-2Cr-0.2W (at.%), were investigated. Both as-rolling and heatreated alloys were examined by optical and scanning electron microscopy and transmission electron microscopy. As-rolling, the lamllar were coarse and the α grain enriched inTi-42.5Al-2Cr-0.2W alloy. Tantalum additions were effective in grain refinement, recrystal grains enriched and the α grain depleted in the microstructure. When the heatreatment temperature increased, the lamellar colonies globularizated more, metastable β phases decomposited as α2+γ.And the time increased, the lamella grain and the γ grain also increased rapidly and respectively in Ti-42.5Al-2Cr-0.2W alloy . The microstructure of the sheet with Ta contained more β phases than the sheet without Ta. Meanwhile, the ω phase precipitated in the alloy with Ta. Besides, the value of hardness for the alloy with Ta was lower than the alloy without Ta, for the Tantalum was effective in grain refinement, the number of β phases and ω phases was few in microstructure.

Abstract:In this paper, CeO₂ with a pore size distribution range of 3.1~4.2nm and a specific surface area of 174.72m₂/g was prepared as a co-catalyst by hydrothermal method. PtNiCeO₂/C catalyst was prepared by microwave assisted glycol method using carbon nanotubes as carrier. Effect of Ni addition on electrocatalytic performance of Pt based catalysts. The prepared CeO₂ and the catalyst were characterized by X-ray diffraction (XRD), BET, SEM and EDAX. The prepared catalyst was characterized by electrochemical workstation electrochemical performance test. The results show that the electrocatalytic activity of CeO₂ catalyst prepared by adding CeO₂ and the ratio of Pt to Ni is 5:1, the electrocatalytic activity is 90.41m₂/g and the peak current density is 837.67A/g, 1100s steady-state current density of 178.33A/g, indicating that adding a certain amount of Ni, can improve the catalyst anti-toxic and electrocatalytic performance.

Abstract:Plasma-sprayed Al₂O₃-TiO₂ and Al₂O₃-TiO₂-Ta coatings were fabricated on aluminum substrates. Due to the introduction of tantalum, Al₂O₃-TiO₂-Ta coating surface morphology is more uniform and compact. At the same time tantalum metal has a very strong acid and alkali resistance, therefore, Al₂O₃-TiO₂-Ta coating relative to the Al₂O₃-TiO₂ coating has a stronger corrosion resistance. The results of Tafel curves show that the corrosion potential of Al₂O₃-TiO₂ coatings shifts the positive corrosion potential by 99.6 mV, and that of Al₂O₃-TiO₂-Ta coatings shifts the corrosion potential of Al by 208.9 mV. Therefore, the corrosion resistance of Al₂O₃-TiO₂ has been greatly enhanced due to the incorporation of Ta metal with high corrosion resistance. The Al₂O₃-TiO₂-Ta coating can effectively prevent the corrosion of the aluminum alloy.

Abstract:Different contents of impurity elements such as O, N, S and P of DZ125L superalloy were obtained through ordinary smelting method and purified smelting method, separately. The microstructures of experimental alloy were investigated by optical microscopy and scanning electron microscopy, the mechanical properties of alloy were also measured. Results show that the contents of O, N, S and P of DZ125L alloy can be reduced from 0.0010% to 0.0005% by purified smelting method, and the contents of shrinkage and inclusions are decreased with increment of the purity of DZ125L. The yield strength and tensile strength at room temperature, 760℃, 850℃ and 980℃ are slightly improved in alloy produced by purified smelting method, while the stress rupture properties at 760℃/800MPa, 850℃/560MPa and 980℃/250MPa are improved dramatically. The creep properties at 950℃ and fatigue properties at 760℃ can also be enhanced by purified smelting method.

Abstract:A symmetry assembled slab of steel/titanium/separating agent/titanium/steel was designed for fabricating titanium clad steel by hot roll bonding. Effect of heating temperature on microstructure, strength-toughness and bonding properties of clad steel plates were investigated at condition of 850-1000℃. The results show that with the increase of temperature, the shear strength decreases obviously. The heating temperature has an important effect on the variety and thickness of interfacial phase. At temperature of 850, 875 and 900℃, carbon can easily diffuse to the bonding interface to form the TiC layer at the cooling process of roll bonding. The TiC plays an role of barrier to hinder the diffusion of iron into titanium. Consequently, TiC and β-Ti are formed at the Ti/steel interface. While at temperature of 950 and 1000℃, carbon can not enrich at the Fe/Ti interface owing to that the diffusion coefficient of C in β-Ti is over 10 times bigger than that of C in γ-Fe. Therefore, iron can diffuse sufficiently into titanium to form the interface products consisted of Fe-Ti intermetallic compounds, TiC, β-Ti and α-β Ti. In addition, the increase of heating temperature promotes the rise of brittle phase layer thickness. The reduction of shear strength is attributed to the increase of variety and thickness of brittle phase.

Abstract:The MgB₂/Mo multilayer films were fabricated, which the MgB₂ layers were grown by using the hybrid physics-chemistry vapor deposited (HPCVD), the Mo films were prepared with Magnetron sputtering (MS) technology. Scanning electron microscopy, X-ray diffraction, and four-point probe method were carried out to study surface morphology, superconducting properties and crystal structure of MgB₂/Mo multilayer. The results addressed the multilayer can maintain good stability which the crystallization degree is further improved and the grain size is increases with the subsequent deposition temperature of MgB₂ films. Excellent properties are obtained in the upper MgB₂ layer prepared at 730℃, including the superconducting transition temperature(T_con) and zero resistance temperature(T_c0) for 39.73K~39.53K,the remaining resistivity down to about 0.77μΩcm, which indicates that films are in the clean limit.

Abstract:MoS₂ films wre prepared on A286 substrate by unipolar pulse magnetron sputtering. The morphology,microstructure and composition of the films were characterized by using scanning electron microscopy, X-ray diffractometer. The mechanical properties and tribological behavior in air of the films were investigated by using nano-indentation tester and ball-on-disc tribotester. This paper discusses effects of pulsed bias on microstructure, mechanical properties and tribological properties of MoS₂ Films. The results show that the preferential oriention of coatings changes from (002) to (100) in advance with the pulse bias voltage increasing from 300 V to 600 V. When the pulse bias voltage increasing to 800V, the preferential oriention renews to (002), and the film was of smooth and compact structure.With the pulse bias voltage increasing, the hardness and elastic modulus will decrease firstly and increase afterward. The friction coefficient fluctuated in the range of 0.065~0.076 and show the tendency of increasing firstly and decreasing afterward. When the bias voltage is 800 V, the property and performance of friction is the best. The wearing rate is only 13.5% of the substrate, It shows the lower friction coeffient and the good wearing resistance.

Abstract:The microstructures and mechanical properties of electron beam weldment Ti1300 alloy after or before different heat treatment were investigated. The results indicated that the various heat treatments before welded treatment cause little effect on microstructures and mechanical properties for different samples. The fusion zone microstructure of non heat treatment (NHT) specimen after welded treatment is mainly composed of columnar β grain and β subgrain with big size, and there is small amount of α phase distributing at high-angle boundary in the fusion zone. This microstructure shows low strength and elongation in comparison to matrix. For the welded specimens after various heat treatments, the morphology and size of columnar β grain or β subgrain, and the distribution of α phase during heat treatment can not be changed. However, the morphology, size and quantity of α phase can be adjusted for different heat treatments, and which determined the mechanical properties of weld joint zone. For the welded samples after annealing or ageing treatment, α phase shows high strengthening effect in comparison to matrix and which result in the failure occurrence in matrix.