Abstract:TiNi shape memory alloy (SMA) is one of the commercially successful shape memory alloys (SMAs) due to its excellent performances. In this work, the 49.3Ti-Ni (at.%) alloy was prepared by vacuum induction melting in 25 kg-grade home-made BaZrO3 crucible, and the cast alloy was turned into wire form (Ф1.0mm). The chemical compositions (including oxygen, nitrogen and carbon) of as-cast alloy were measured and the phase constitution was analyzed by X-ray diffraction (XRD), the microstructures were observed by Optical Microscope (OM) and Scanning Electron Microscope (SEM), the shape memory recovery rate and fatigue life of alloy wires were tested by two home-made test apparatus respectively. Experimental results showed that the contents of oxygen and nitrogen in alloy ingot were 560 ppm and 17 ppm respectively, and the impurities contents in TiNi alloy melted using the BaZrO3 crucible are just eligible to medical devices and surgical implants. The chemical composition melted by the BaZrO3 crucible is more uniform and accurate than by the vacuum arc remelting (VAR). The present presents higher shape memory rate and fatigue life than graphite crucible, the best shape memory recovery can reach 98.62% with 2% deformation and water aging at 550℃ for 20min, and the best average fatigue life can reach 3072 times with water aging at 500℃ for 20min.

Abstract:The semi-solid TiAl3/A356 aluminum composite was prepared by ultrasonic vibration treatment(UVT). The effects of UVT temperature, time and power on the microstructure of semi-solid slurry of TiAl3/A356 composite were studied by using SEM and X-ray diffraction techniques. The results revealed that the size of primary α-Al particles increased with the decrease of UVT temperature and power. The size of primary α-Al particles decreased at first and then increased with the increase of UVT time. When treated for 60s at an UVT temperature of 608 ℃ and an UVT power of 1KW, a good primary α-Al particle morphology with an average size of 62 μm and a shape coefficient of 0.8 could be obtained. The mechanism involved in the development of microstructure is the result of increase of nucleation rate and undercooling caused by a cavitation and acoustic streaming. Furthermore, the in situ TiAl3 particles have strong ability to nucleate α-Al particles.

Abstract:3mm thick TC4 titanium alloy and 2A14-T4 aluminum alloy were well joined by friction stir welding (FSW), and the influence of tool offset on weld formation and tensile property of the joints was investigated. The results show that tool offset to the Al side has significant influence on ultimate tensile strength (UTS) of the joints. With the increase of tool offset, the UTS increases gradually. When the tool offset is 2.0mm, the UTS of the joint decreases with increasing tool rotation speed from 400r/min to 700r/min. However, when the tool offset is increased to 2.5mm, the UTS of the joint increase with the increase of tool rotation speed. A tool rotation speed of 700r/min and a welding speed of 60mm/min is matched, the highest UST of 347MPa of the joint is obtained, which reaches to about 83% of Al matrix. The tensile results prove that the fracture location and tensile strength of the joints mainly depend on microstructure and intermetallic phases. For the joint with the highest strength, the fracture occurs in the heat affected zone (HAZ) of Al matrix due to brittle TiAl phase formed in the joint.

Abstract:Microstructural evolution of Ti-1300 alloys was investigated using an optical microscopy, scanning electron microscopy, transmission electron microscopy and electron backscatter diffraction during continuous cooling. Then, a continuous cooling transformation diagram was established using dilatometric method, and the different kinds of β phase decomposition modes in the alloy under continuous cooling were investigated in detail. Moreover, the β → α + β phase transformation and colony structures are observed for low cooling rates. When the cooling rate is from 0.3 °C/s to 1.5 °C/s, the β → α + β + β_m phase transformation and needle-like structures are observed in the alloy. However, when the cooling rate exceeds 3 °C/s, the alloy is only composed of a single metastable β phase. Thus, a rate of 3 °C/s is considered as critical cooling rate of the alloy under continuous cooling condition. The concentration gradient of molybdenum equivalent is considered as a driving force of α phase growth in the alloy.The microhardness of the alloy initially increases and then decreases with increasing of the cooling rate. When the cooling rate is 0.3 °C/s, the microhardness of the alloy reaches its maximum.

Abstract:The effects of hydrogen addition (0.12 wt.% H) on microstructural evolution in Ti-0.3Mo-0.8Ni alloy argon-arc welded joints have been investigated using optical microscope (OM), X-ray diffraction (XRD) and transmission electron microscopy (TEM) to reveal the influence of hydrogen on the characteristics of defect-free titanium alloy welded joints. The results show that hydride precipitation changed the initial microstructure of the welded joints, the increase of hydrogen content was more favorable for the beta phase precipitation. Face centered cubic δ hydride evenly distributed in the hydrogenated 0.12 wt.% H welded joints, the lamellar δ hydride could only precipitate from the lamellae alpha, and not from the transformed beta phase. Formation of δ hydride was associated with the result of αH phase separation reaction: αH→α (H lean region) + δ (H rich region), and H rich regions finally transformed to the δ phase. The dislocation distribution was heterogeneous and there was a relatively high density of dislocations in the vicinity of the precipitated δ hydride, which were caused by the lattice distortion due to the stress field generated by the hydride precipitation.

Abstract:A nickel intermediate layer was firstly electrodeposited onto the titanium substrate by cathodic electroplating, then the β-PbO2 coating was electrosynthesized by anodic oxidation. The resulting Ti/Ni/PbO2 was compared with the Ti/PbO2 electrodes without intermediate layer. The effect of plating nickel intermediate layer on the structure and performance of PbO2-coated electrodes were investigated by microstructure characterization, accelerated life test in 1mol/L H2SO4 solution, electrochemical performance and electro-oxidation behavior of simulated phenol wastewater. The results indicated that the introduction of nickel electroplating intermediate layer leads to the grain refinement of the surface active β-PbO2 coating, thus enhancing the catalytic performance of PbO2-coated electrodes. Furthermore, the Ni intermediate improves the conductivity of the electrode, thus significantly reducing cell voltage, enhancing potential uniform distribution of the electrode surface, extending the electrode lifetime and reducing the energy consumption of electrocatalytic oxidation of simulated phenol wastewater. Besides, the introduction of nickel inter-layer might enhance the catalytic performance of the electrode.

Abstract:The sintering process is formulated by dehydrogenation properties of titanium hydride and zirconium hydride,combined with powder metallurgy method,Ti-13Nb-13Zr alloy is prepared by die pressing and vacuum sintering titanium hydride powde,niobium and zirconium hydride powder.The sample is investigated by metallographic microscope,SEM,XRD.The result shows that through this process, the relative density of sintered body is 92.2%.SEM result shows that platelet α and platelet β exists in the alloy.During the formation of the alloy,as beta stable element niobium makes the β-phase is still in the alloy after cooling.Analysis based on XRD data reveals the presence of the α-Ti andα-Zr are hcp and the β-Ti、Nb and β-Zr are bcc.

Abstract:Artificial tribo-layer containing Fe₂O₃ were induced to form at room temperature by supplying Fe₂O₃ nanoparticles and its mixtures with TiO₂ or MoS₂ onto the sliding interfaces of Ti6Al4V alloy and GCr15 steel. The role of Fe₂O₃, TiO₂ and MoS₂ on the sliding wear performance of Ti6Al4V alloy was respectively studied. The effect of the relative content of Fe₂O₃ in artificial tribo-layer on wear behavior and mechanism of Ti6Al4V alloy was also explored. Results showed that Ti6Al4V alloy indeed presented a terrible wear resistance, but it would be changed by the supplied particles. The wear rate of Ti6Al4V alloy was further accelerated by TiO₂, was slightly and inappreciably reduced by MoS₂, but was completely inhibited by Fe₂O₃. In the case of supplying TiO₂-rich or MoS₂-rich particles, they were agglomerated into the grooves or pits on worn surfaces, instead of forming a tribo-layer. For Fe₂O₃-rich particles, an artificial tribo-layer were noticed to form and cover the worn surfaces. It was confirmed that the improved elevated-temperature wear resistance of titanium alloy was attributed to the appearance of Fe₂O₃. As the particles of MoS₂+80wt.% Fe₂O₃ were supplied, the tribo-layer possessed both of the lubricating property of MoS₂ and the load-carrying ability from Fe₂O₃, which brought the best performance of friction and wear for Ti6Al4V alloy.

Abstract:Based on Ti-Al-M alloys , the effect of V、Mo elements on as-cast microstructure as well as the microstructure of different heat treatment processings is studied. V、Mo elements can change the solidification path of conventional γ- TiAl, avoid peritectic reaction, and preserve β phase to room temperature. The martensite mode will be observed in the microstructure subjected to water quenching condition, with increasing the content of V、Mo elements. During two-step heat treatment procedure, with Mo addition, alloys are prone to the transformation reaction of α→β＋γ as well as β→β＋γ.

Abstract:Effects of target thickness and macroscopic interface on the ballistic performance of Ti6Al4V titanium alloy were investigated. The monolithic Ti6Al4Vtitanium alloy with thickness varied between 10mm and 30mm and the armor configurations of the double-layered (15+15)mm Ti6Al4V titanium alloy were normally impacted by the 12.7mm AP. The results showed that the ballistic performance increased with the increase of the target thickness. Significant improvement was observed when the target thickness varied between 15mm and 20mm, this was considered to be related to the failure mechanism involved. The 30mm monolithic Ti6Al4V titanium alloy was more effective than the (15+15)mm double-layered Ti6Al4V titanium alloy, this was thought to be related to no exist shear strength on the macroscopic interface between the double-layered targets.

Abstract:Considering the problem of coarse microstructure and awful mirco-orientation distribution of TC4 titanium alloy welded-joint with high friability and low plasticity, we designed the post welding cyclic heat treatment between α+β and β-tansus temperature, and discussed the effect of different heat treatment process on the tissue morphology. The equiaxial alpha phase and lamellar alpha and transformed beta phase composition of the tri-modal microstructure was obtained. The study found that improving the cyclic times, occurrence of alpha phase could increase, and the ratio of length to diameter decreased.However, after five cycles some crystal orientation to meet the lamellar related to α Burger orientation relationship of abnormal growth, lammelar alpha rest staggered phase well-distributed, whereas equiaxed alpha phase is not conducive to improve the mechanical properties. When the clcyic times inceased, the more spherificated α phase appeared, and the length to diameter ratio reduced significantly, generally was less than 3. In addition, there were different kinds of small bars α phase around spherificated α phase. After four cyclic heat treatment, the product of strength and elongation of welded joint achieved 14441.17 MPa?%. The mechanical tests result showed that, after four times of cyclic heat treatment the plasticity of welded joint fracture are at maximum, compact size uniform dimples, have obvious ductile fracture characteristics. Almost at the same time, the yield strength and significantly increased, combined with analysis of EBSD, TEM test results, explain the causes of the phenomenon, and a detailed description of the changes in circulation process and spheroidizing mechanism.

Abstract:Customized metal powder with a series of specific indexes is the core material to Selective Laser Melting (SLM) process, by which, the fabricated parts exhibit high precision in dimension and excellent properties in mechanics. While, multiple properties of the powder may change during the forming and recycling processes, and that could impair the products’ quality of SLM. This paper focused on the variation of TC4 powder’s properties, including particle morphology, particle size distribution (PSD) and flowability during the recycling process, and the underlying mechanism of the variation was proposed in the meantime. It was observed that the particles still kept morphology of sphere and became smoother with the increasing recycle times; few satellite particles were observed after recycling 14 times; the PSD experienced the course of concentration-dispersion-concentration; the recycled powder showed improved flowability；All the variation above inextricably linked with the percentage decreasing of tiny particles and satellite particles in the recycled powder.The porosity of the forming sample increased firstly and then decreased with the increasing recycle times ; recycle times of TC4 powder had no effect on microhardness.

Abstract:The influence of frequency, amplitude and intermittent vibration modes of ultrasonic vibration on the stress and strain, yield strength, tensile strength and elongation of TC1 titanium alloy sheet is studied by ultrasonic vibration assisted tensile test. The influence of ultrasonic vibration parameters on the microstructure, fracture morphology and vickers hardness of TC1 sheet is studied by analyzing the microstructure and properties of tensile specimen. The results show that superimposed a certain frequency and amplitude of the ultrasonic vibration can significantly reduce the material yield strength and tensile strength in the TC1 titanium alloy sheet tensile process. The elongation of the material can be greatly improved under certain technological parameters, and the effect on the microstructure and properties of TC1 sheet is less.

Abstract:TC4/TC11 direct-transition alloy samples were prepared by laser deposition technique, and the stress relief and solution aging heat treatments were carried out. The microstructure, tensile fracture were observed using optical microscope (OM), scanning electron microscopy (SEM) and universal testing machine, then the tensile properties and hardness were tested and analyzed. The results show that the basket-weave microstructures of two sides of the deposited TC4/TC11 differ greatly, the microstructure is much more uniform after stress relieving and the microstructure is coarser after solution-aging. After the tensile tests under ambient temperature on the stress-relieved samples, the minimum tensile strength of TC4/TC11 is located at the direct transition zone, which is close to that of TC4. TC4/TC11 has a low plasticity at the direct transition zone. The fracture sections at room temperature are all on the side of TC4 titanium alloy, which proves that the direct transition interface of TC4/TC11 has good properties. The microstructure analysis of the direct transition zone explains its micro-hardness variation.

Abstract:Applying an electrically insulating coating on the inner surface of the lithium flowing ducts is a feasible way to effectively mitigate the MHD pressure drop for Li/V self-cooled blanket. This paper mainly overviews the present progress and issues of the insulating coatings, including the single-layer insulator and the multilayer insulatos. Many studies have showed that the single-layer insulator does not perform as stablely as theoretically especially at elevated temperatures, so the necessary of development of the multilayer insulators has been stressed. However, the currently investigated “V-alloy/insulator/metal” structured multilayer insulting coating (such as V-alloy/Er2O3/V) exists some obvious weaknesses, such as the difficulty in realizing the in situ formation and self-healing of the surface metal layer, the compatability problem between lithium and the surface metal layer. Then a new V-alloy/metal/insulator structured multilayer insulator is proposed, which has the potential to realize the in situ formation and self-healing and probably a new possibility for the development of the insulating coating.

Abstract:The tensile properties, aging precipitate type and distribution in Al-Cu-Li-(0.35Mg)-(0.2In) alloy were investigated. In the T6 aged Al-Cu-Li alloy, the aging precipitate are T1(Al2CuLi) and ?? (Al2Cu). As 0.2%In is added, many square-shaped cubic precipitates Al5Cu6Li2 are formed at early aging stage and their size keeps stable with aging time extension. Meanwhile, ? ? precipitation is advanced. The alloy?s aging response is therefore accelerated and its strength is enhanced. The combined addition of In+Mg suppresses the precipitation of cubic Al5Cu6Li2, but plays a role in promoting T1 precipitation instead. This role is smaller than that of combined addition of Ag+Mg in Al-Cu-Li alloy 2050, which results in a lower strength of the In+Mg micro-alloyed Al-Cu-Li alloy than that of the Ag+Mg micro-alloyed Al-Cu-Li alloy 2050. At T8 temper, the role of both In independent addition and In+Mg combined addition is suppressed by the dislocations introduced by plastic deformation prior to artificial aging.

Abstract:The CNT bundles can be jagged and used as template to load the precursor H₂WO₄. The H₂WO₄ seeds can be enclosed by the jagged CNT template during liquid precipitation process. The H₂WO₄clusters with avarage size of 500Snm are consisted of nanosized H₂WO₄with 10-20 nm diameter, which display high specific surface area of 85.24 m₂ g_-1 and total pore volume of 0.2933 m₃ g_-1. After thermal treatment of H₂WO₄/CNTs at oxygen atmosphere, nano-WO₃ particles attached to sphere-like micro-WO₃ can be easily obtained by removing the CNT template. Its specific surface area and total pore volume is 18.7 m₂ g_-1 and 0.2055 m₃ g_-1respectively. These results indicate that the jagged CNTs can play an important role for effective mediation of WO₃ with hierarchical size, and exhibit excellent prospects for preparation of micro-nanostructured materials.

Abstract:W-Cu alloy has been applied in metallurgy, materials, electronics, military and other fields because it has good arc-resistance, anti-welding, conduct heatSandSelectricity and so on. Electrical conductivity is one of the important material performanceSindexes and has attractedSmuch attention. The electrical conductivity models of W-Cu alloy with different content of Cu are studied in this paper. The characteristics and applicableSrangesSofStheseSmodels is also discussed. The conductivity are calculated by using these models and compared with the experimental results and the theoretical values. The suitable theoretical values of W-Cu alloy are selected and compared to the experimental values. The results show the experimental conductivity is basically consistent with the theoretical values for W-Cu alloy with low or high Cu component. Enhancing copper content and reducing porosity lead to increasing the conductivity of W-Cu alloy. This offers the theoretical basis to design the constituent and electrical conductivity of W-Cu alloy.

Abstract:The amorphous silicon oxycarbide powders containing in situ-grown single-crystal silicon carbide nanowires were fabricated via the pyrolysis of a polymeric precursor with ferrocene as the catalyst. The nanowires, with lengths of several micrometers and diameters of 10-100 nm, were composed of single-crystal β-SiC along the <111> growth direction and uniformly dispersed in the composite powders. The growth mechanism of silicon carbide nanowires was explored by analyzing the microstructure of the silicon carbide nanowires. The dielectric properties of the composite ceramic powders were studied, which demonstrates that silicon carbide nanowires can be used to adjust the electrical of the composite and a high nanowire content can result in a large real and imaginary part of permittivity.

Abstract:The hybrid structure of composite material such as carbon fiber-reinforced polymer (CFRP) and metal such as steel, aluminum alloy or titanium alloy is an effective structure to realize lightweight with reliable structural strength. The CFRP-metal hybrid structure is widely used in aircraft, automobile and watercraft. The CFRP-metal joints joined by plastic deformation are characterized by lightweight and high-strength, which are suitable for various working environments. Thus, the advanced joining method based on plastic deformation has a good application prospect. The application of various joining techniques between CFRP and metal, as well as the strength of hybrid joints, was reviewed. Some future researches and developments of CFRP-metal hybrid joints with high-performance, light-weight and high-reliability were highlighted.

Abstract:In recent years, fabrication of bulk ultrafine-grained (UFG) Al-Li alloys via severe plastic deformation (SPD) techniques has been investigated to improve properties for expanding its applications as structural products. This review reveals microstructure and mechanical properties of Al-Li alloys produced by SPD techniques. It focuses on the microstructure evolution during SPD, with the influence of internal and external factors. The strengthening mechanism of Al-Li alloys mainly based on precipitation hardening is presented. It is demonstrated that UFG Al-Li may attain enhanced strength with relatively good ductility via grain refinement and multiple precipitates. Special attention is given to the superplasticity of UFG Al-Li alloys, especially to the high strain rate superplasticity (HSR SP). It suggests that UFG Al-Mg-Li alloy produced by SPD, particularly by equal-channel angular pressing (ECAP), is a promising candidate material for use in superplastic forming operations.

Abstract:Conventional casting method was adopted to fabricate the alloys of Mg-Zn-Y, in which the dendritic morphology and its relation to the damping properties of as-cast Mg-Zn-Y alloy were studied based on the typical Mg93Zn6Y1 alloy containing icosahedral quasicrystal phase. By controlling the pouring temperature, the stirring speed and stirring time, the dendritic morphology with different parameters was obtained. The results show that the microstructure of the as-cast Mg93Zn6Y1 mainly consists of α-Mg dendritic crystal and icosahedral quasicrystal phase. After stirring, the primary α-Mg dendritic gradually have fractal characteristics in faith, and its size changes, affecting the damping capacity. The mechanism was discussed in detail.

Abstract:Nitrogen doped anatase/rutile/brookite titanium dioxide (N-TiO₂) regular nano-rod bundle photocatalyst for improving visible light photocatalytic activity was prepared through a template-free sol-hydrothermal method. The properties of the materials were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), ultraviolet-visible diffuse reflectance spectra (UV-Vis DRS), Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS). Photocatalytic degradation of methyl orange (MO) in an aqueous solution under visible light irradiation was used as a probe reaction to evaluate the photocatalytic activity of the mixed-phase N-TiO₂ nano-rod bundle. The results of characterization combined with photocatalytic activity of MO photodegradation showed that the synergistic effects among N doping, mixed-phase and nano-rod bundle structure were the main reason to improve photocatalytic activity of mixed-phase N-TiO₂ nano-rod bundle compared with P25-TiO₂. The possible mechanism of MO degradation by mixed phase N-TiO₂ nano-rod bundle photocatalyst was preliminarily discussed.

Abstract:Abstract: Cr-TiAlSiN composite coatings were deposited on the substrate of zirconium alloys tubes by multi-arc ion plating and intermediate frequency unbalanced magnetron sputtering, respectively. The micro-morphology of surface and cross-section of the composite coatings was observed by a scanning electron microscopy; the porosity and the quantity of large particles on the surface were analyzed by Image J software; the adhesion strength between the coatings and substrate was measured by a?pull pressed?spring?testing machine; the samples were subjected to high temperature oxidation test at 800℃ and high temperature quenching test at 1200℃ by using a high temperature furnace. The results show that there are more large particles on the surface of the coatings deposited by multi-arc ion plating, but the porosity of that is relatively low, so that the high temperature oxidation resistance behavior is better. The interface of the composite coatings is relatively clear and uniform, and the adhesion strength between the coatings and substrate is relatively strong, both of which are higher than 22.68MPa. According to the high temperature quenching test at 1200℃, it also turns out from the side that the adhesion strength is better with the process of multi-arc ion plating.

Abstract:Effects of Ga and Ce additions on the microstructures and mechanical properties of Ag17CuZnSn-xGa-yCe filler metals and brazed joint were investigated by microscopy method and tensile test. The results indicated that the solidus and liquidus temperatures of filler metals decreased with addition of Ga and Ce. And the wettability of filler metals on the brass and stainless steel improved when the content of Ga and Ce are 2 wt. % and 0.15 wt.%. The highest shear strength of brazed joint was 3% higher than the shear strength of the Ag17CuZnSn-2Ga. During brazing process, Ga has a higher diffusion coefficient into stainless steel than that of other elements. A novel Ce₂₀(Ag, Cu)₄₀Sn₄₀ intermetallic phase was found in filler metal when the content of Ce is higher than 0.3 wt.%.

Abstract:AlxFeCoNiB0.1 (x=0.4, 0.5, 0.8, 1.2, 1.6where, x is the mole percentage) were prepared by vacuum arc melting.The microstructure and mechanical property of AlxFeCoNiB0.1 high-entropy alloys were investigated. With the increase of Al content, the cast dendrites of the alloy were changed from FCC phase to B2 (AlNi) /BCC phase. When x= 0.4 and 0.5, the microstructures of the alloy were consisted of the dendrite FCC phase and the interdendritic B2 phase and (Fe, Co) 2B; when x=0.8, the dendrites were composed of B2 phase, and the interdendrites were composed of FCC phase and (Fe, Co) 2B; when x=1.2, the interdendritic structures were consisted of the eutectic FCC+ (Fe, Co) 2B, and the nanoscale granulars are the BCC phase;When x=1.6, the eutectic structures disappeared. With the increase of Al content, the compressive strength increased first and then decreased. When the content of Al was 0.8, it reached the peak value of 2243MPa. Appropriated amount of Al can improve the comprehensive mechanical properties of high entropy alloy。

Abstract:The ultra-high-strength stainless steel with high strength and toughness, high inherent fatigue strength and good corrosion resistance can be mainly used in some load- bearing components, such as landing gear, gas turbine engine shaft, and wheel bolts that working under corrosion environment. An environmental friendly ultra high strength stainless steel S280 for a new type of aircraft landing gear was developed in order to avoid the toxic effect of protective coating processes. The new ultra high strength stainless steel S280 has mechanical properties equal to, or better than conventional ultrahigh strength steels with the added benefit of modest corrosion resistance. By heat treatment process experiments and mechanical tests, the appropriate heat treatment process of S280 steel (Heating to 1080 ℃，holding at heat for one hour, and quenching in oil, cooling to -73℃, holding at this temperature for two hours, and warming in air to room temperature and then heating to 540℃, holding at heat for four hours, and cooling in air) was found in this paper. After heat treated under the appropriate heat treatment process,S280 steel can get good comprehensive performance, with the strength of 1900MPa, and KIC of 90MPa?m1/2. The new ultrahigh strength stainless steel S280, which apply low-carbon martensitic transformation hardening and aging strengthening superimposed, has high performance and can replace the existing Aer-Met100,300M steel material used for aircraft landing gear. The microstructures of new ultrahigh strength stainless steel S280 after thermal ageing at 540℃ and 600℃ was investigated by optical microscopy, transmission electron microscopy (TEM) and high-resolution electron microscopy (HREM).The results show that the S280 steel aged at 540℃ has desirable microstructures, which is fine lath martensite matrix with high-density dislocation and finely dispersed precipitate strengthening phase, and film-like reversed austenite precipitated from the boundary of martensite. The strengthening phases of the steel include Fe2Mo[1], Fe3C and Cr2C. There is no related report about that Cr2C precipitated from ultrahigh strength steel as a strengthening phase. In this paper, it was firstly discovered. And the crystallographic orientation relationship between Cr2C and matrix was measured: (1 -1 0 )M // ( -1 2 -1 )Cr2C, [ 1 1 1 ]M // [ 1 1 1 ]Cr2C The steel aged at the different temperature of 600℃ and 540℃ have the same precipitated phases Cr2C and Fe2Mo. The precipitated phases are relatively bigger than that of sample aged at 540℃.The strengthening phases of S280 steel have a high content of Cr and Co analyzed by energy spectrum analysis (EDS).

Abstract:In the process of manufacturing 7075 aluminimun alloy thick plate, the non homogeneity of plastic deformations and mechanical properties of the material will generate residual stresses. During the following high speed machining process, the release and redistribution of residual stresses are key to deformations of aeronautical monolithic component with the removal of material. Therefore, the study of the analytical method on the residual stress release and redistribution can more clearly understand the evolution mechanism of machining deformation, which is the core link of controlling the machining quality. This is because it is very important for the realization of machining process with high efficiency and precise. Through equaling the removal of materials to the release of residual stresses, the residual stresses remained in the aeronautical monolithic component are converted into the external force according to the static equilibrium conditions, the analysis model is deduced for machining deformations based on the small deformation theory. Because the overall consideration on position variation is done by the tension/compression of neutral surface, bending of neutral surface, and rotation of end surface, the superposition principle can be used to formulize the mechanical model of residual stress redistribution. The proposed analytical model can be suitable for the accurate calculation of the machining deformations of aeronautical monolithic component, in addition to the analysis of the residual stress redistribution. The comparison among the model calculations, the simulated values and the experimental measurement data shows that, both the amplitude and deformation curve, the model calculations are good agreement with the simulated values. Moreover, the measurement error of residual stresses causes the little difference of the amplitude of the model calculations with the experimental measurement data, though the deformation curves of the two have a good agreement with each other.

Abstract:Nanomaterials La2O3:Sm3+was prepared by combustion synthesis. The morphology and structure were characterized and analyzed by TEM and XRD. The luminescent properties were also investigated. The results were indicated that the mean particle size of La2O3:Sm3+ nanomaterials with hexagonal structure were approximately 34 nm. Because of the Sm3+ doping, the position of diffraction peaks of La2O3:Sm3+ moved to the right slightly; It was observed that intrinsic excitation band of Sm3+ was located in around 411 nm; Under the 411 nm excitation, the major emission peaks at 4G5/2 → 6H5/2 (568 nm)，4G5/2 → 6H7/2 (611 nm, the highest intensity) and 4G5/2 → 6H9/2 (654 nm) were observed. The emission spectrum indicated the location of the Sm3+ ions were asymmetric. The decay lifetime of the Sm3+ ions was about 202 μs; The chromaticity coordinate was approximately (0.5849, 0.4143).

Abstract:The statistical characteristics of Zr-based metallic glass reinforced porous W matrix composite are extracted using two-point probability functions. And representative volume elements (RVE) of the composite are reconstructed. The results show that the micro-structural geometric structure characteristics can be described satisfactorily and the theoretical foundation of macro isotropy of materials is approved. Though the RVEs have the same geometric characteristics with original composites, RVEs are only 2.2% in the size of original SEM picture. Which can increases the efficiency of finite element analysis. A strong tool is developed for the research of Zr-based metallic glass reinforced porous W matrix composite by this work.

Abstract:Mechanical properties of the Nb2C and U(N,C) inclusions and matrix in the U-5.5Nb alloy are characterized by nanoindentation and the yield strength and plasticity index are calculated from the obtained hardness. The result from experiment shows that the Nb2C inclusion has the highest elastic modulus and hardness, while the corresponding values of the U(N,C) inclusion are far less than those in the Nb2C inclusion but higher than matrix. Moreover, the result calculated from hardness shows that the yield strength of the Nb2C inclusion is the highest, but the plasticity index is the lowest, which reveals that the Nb2C inclusion inclines to elastic deformation. However, the yield strength of the U(N,C) inclusion is low and the plasticity index of the U(N,C) is the highest, which reveals that the U(N,C) inclusion prefers to plastic deformation and also can broke easily. Elastic modulus and hardness from multi-cycle load/unload test are close to those obtained by single load/unload test, in addition, the elastic modulus obtained from nanoindentation is accord to the value obtained by tensile test in the literature.

Abstract:Mg-10Gd-0.5Zr alloys with 1-5wt% Sm addition were prepared by melting and casting method. The effect of Sm on microstructures and mechanical properties were investigated by tensile tests, SEM and XRD. The results show that the Mg₄₁Sm₅ phase is found because of Sm addition, Sm promotes the precipitation of Mg₅Gd. After solution-aging treatment, the coarsening eutectic structures at grain boundary were dissolved and the precipitation dispersed homogeneous. The finer grain size is observed when content of Sm come to 3wt%. Some of Mg₅Gd phase become short rod-like when Sm addition is 5wt%. Under the same experimental temperature, the strength of tested alloys increases at fist and then decrease, and peak strength present when content of Sm is 3wt%. For the same alloy, with increasing of test temperature, the strength increase at fist and then decrease too. When Sm content is 0~1wt%, the temperature of tensile strength peak is 200℃ and the temperature is 250℃ when Sm content is 3~5wt%. There are abnormal temperature effects in tensile tests, the effect is reinforced and the temperature of tensile strength peak rise with the Sm addition.

Abstract:Fatigue crack propagation experiment of AZ31 magnesium alloy in different direction were conducted accompanied by acoustic emission monitoring, and the results presented similarities with the conventional results. Acoustic emission hit counts has a liner relationship with the stress intensity factor range during the stable cracking stage, and the turning point of dC/dN-ΔK curves had error of 2.86%(along the rolling direction)and 3.00% (vertical to the rolling direction) with that of da/dN-ΔK. The crack along the rolling direction propagated slower than another direction, and the reason could be listed as follows: there was obvious quasi-cleavage fracture and more twins when the crack propagated vertical to the rolling direction, which could stop cracking at some extent. So the crack resistance of rolling direction below another direction. and acoustic emission technique was a practical method to study the fracture behavior.

Abstract:Based on the equal addition amount of carbon, the effects of MgCO3, CO2 and CO on grain refinement in AM60B alloy were investigated. The results indicated that the average grain size of AM60B alloy reduced from 213μm to 116μm, 90μm and 106μm respectively due to the addition of MgCO3, CO2 and CO. Also, the Vickers hardness, tensile strength, yield strength and elongation of AM60B alloy inoculated by MgCO3, CO2 and CO were all improved in some degree, moreover, AM60B alloy treated by CO2 have the best mechanical properties, followed by CO and MgCO3 in sequence. In addition, supported by SEM, EDS and XRD, the observed Al4C3 particles as a result of the addition of MgCO3, CO2 and CO should be responsible for the grain refinement of treated AM60B alloy.

Abstract:In this article, NiCrAlY bond coatings was deposited on the Ni-based superalloy (N5) by EB-PVD, and the sample was oxidized by the constant temperature of 1000℃ for different time. Interdiffusion behavior of interface between subatrate and bond coat, as well as, the foramation mechanism of reaction zone was analyaed by SEM、EDS and XRD. The result shows that the elements of Al and Cr in the NiCrAlY coating was diffused to the N5 substrate and formed an interdiffusion reaction zone dominated with β-NiAl phase and α-Cr phase; and the Ni elements in the N5 substrate was diffused to the NiCrAlY coatings, forming the secondary reaction zone and TCP phase, which was mainly composed with the γ’-Ni₃Al and refractory metal respectively.

Abstract:The residual stress on surface of variable polarity plasma arc (VPPA) weldedS5A06 aluminium alloy sampleSwas measured by synchrotron radiation X-ray diffraction, and the distribution of residual stress on the surface of the sample was obtained in this paper. The generation and evolution mechanisms of weld zone, heat affected zone, base metal area were analyzed in combination with metallurgical structureSobservation, EBSD and microhardness tester methods. The results show that the weld zone of VPPA welded 5A06 plate shows coarse grainS, the grains in the heat affected zone are small, the residual stress presents an "M" shape: the weld zone is compressive stress, and the heat affected zone is tensile stress; There is a maximum tensile stress of 75.79 MPa and a maximum compressive stress of 159.34 MPa in the direction vertical weld (TD) and a maximum tensile stress of 132.33 MPa and a maximum compressive stress of 89.38 MPa in the direction parallel to the weld (LD). Compared with the trend of the residual stress measured by traditional X-ray instrument, the distribution trend of the residual stress of the synchrotron radiation diffraction measurement is more consistent with the variation trend of the microhardness of the sample in different welding areas. The experimental results show that the residual stress data of synchrotron radiation X-ray diffraction measurement has better consistency than the traditional X-ray instrument.

Abstract:TiB2-SiC composite powders were prepared by spray-drying, and the influence of slurry solid content, binder content and SiC content on the particle morphology of the spray-dried powder were investigated. TiB2-SiC flattening splats were collected on the polished graphite substrate by air plasma spraying under different substrate temperature and spray distance. The influence of coating parameters on the splat morphology were investigated. Besides, TiB2-SiC coatings were prepared by air plasma spraying. The results indicate that TiB2-SiC powder with high sphericity, and good fluidity is obtained by spray-drying when the solid content of the slurry is 50wt.%, the binder content is 5wt.%, and the SiC content is 10wt.%. With the increase of the substrate temperature and spray distance, the flat particles gradually decreases to form regular disc-shaped particles. Under the flame of plasma, TiB2-SiC particles melting accelerate and collide with the substrate. The molten particles are flattened, rapidly cooled and solidified. Therefore, the TiB2-SiC particles are continuously stacked and connected as a macroscopic coating.

Abstract:In order to improve the manufacturing precision of nanoscale germanium, nano-scratch instrument was used to process the nanogrooves of single crystal germanium. The morphology of the groove was observed by scanning electron microscope, and the three-dimensional morphology was measured by the three-dimensional white light interferometer. The effect of the cutting speed, the applied vertical load and scratching number on the morphology of single crystal germanium nanogrooves was studied. Linear fitting curves and power function fitting curves of vertical load and number of scratches with groove depth and width were established and analyzed. The results show that the width and depth of single crystal germanium nanogrooves are very small with the cutting speed, and with the increase of vertical load, the scratching number increases. The fitting degree of the curve is very high. It can predict the depth and width of the nanoscale groove more accurately, which can reduce the surface roughness of the workpiece and improve the surface quality of the workpiece.

Abstract:The TIG welding process of ZL114A aluminum alloy that modified by Al-Sr master alloy was obtained by selecting welding vice and wire with different states and thicknesses. The chemical composition of the material was determined by inductively coupled method, and the effect of vacuum dehydrogenation on microstructure and mechanical properties nearby welding region were analyzed by Electronic hydrogen measuring instrument, OM, SEM, EDS, TEM and Universal testing machine. The results show that the hydrogen content decreases from 0.64×10_-6 to 0.26×10_-6, accompanying with the number of bubbles within 24mm and 12mm thickness reduce 71.4% and 60% individually, the diameter decrease from 2.3mm and 1.8mm to 1.4mm and 1.2mm, together with a reduced surface density by 77.7% and 81.8% after the vacuum dehydrogenation process. The morphology of silicon phase that distribute nearby grain boundaries transforms from needle-like to spherical, the particle size reduces from 106μm to 12μm, the average tensile strength, yield strength, elongation and reduction of area of 12mm thickness are 364MPa, 332MPa, 9.8% and 14.2%. The microstructure under T6 state mainly contains primary α-Al, primary and eutectic Si phase and Mg₂Si aging phase, the diameter of brittle Si particle is 4μm, Mg₂Si aging phase shows a rod-like morphology and the aspect ratio is 15.2, the shape of dimple changes from elliptical to spherical and the fracture mechanism evolves from intergranular frcture to dimple rupture after vacuum dehydrogenation.

Abstract:The semi-solid extruded ZCuSn10P1 tin bronze was used as the research object. The effects of heat treatment temperature on microstructure and mechanical properties of semi-solid extruded tin bronze were investigated by using optical microscopy, scanning electron microscopy, microhardness test, Brinell hardness test, tensile test machine. The results indicate that the heat treatment has a great effect on the strength, hardness and microstructure of semi-solid extruded tin bronze. With the heat treatment temperature increase from 250℃ to 650℃, the tensile strength of tin bronze increases first and then decreases, the elongation increases, the Brinell hardness increases first and then decreases. The Vickers hardness of the solid zone and solid-liquid interface increases, however, the liquid zone decreases. The average grain size of solid phase increases, while it is not spherical but rose-like with the temperature increases up to 650°C. With the increase of temperature, the element contents of Sn and P in the solid phase increase, and element segregation weakens. The comprehensive mechanical properties of tin bronze at heat treatment temperature 350°C for 120 min are fine. At this time, the tensile strength is 402 MPa, elongation is 4.5%, Brinell hardness is 136 HBW, compared with before heat treatment, it increases by3.88%, 60.71%, and 6.25%, respectively.

Abstract:Carbon nanotubes(CNTs) coated with metals will show further improvement of electromagnetic shielding performance，due to the composite effect of CNTs and metal coatings. In this paper, Ni-coated CNTs (Ni-CNTs)were firstly prepared with a novel electroless plating method assisted with ultrasonic spray atomization, and then silver coated Ni-CNTs(Ni/Ag-CNTs) and copper coated Ni-CNTs(Ni/Cu-CNTs) were prepared respectively by electroless plating or coprecipitation. The obtained composite powders were characterized by TEM、FESEM and XRD. The Ni-CNTs showed continuous and uniform nickel layers on highly dispersed CNTs，and both the Ni/Ag-CNTs and Ni/Cu-CNTs composite powders showed the morphology of Ni-CNTs embedded in silver or copper particles. The multi-metal coated CNTs showed significant improvement of electromagnetic shielding properties, and the shielding effectiveness of Ni/Ag-CNTs, Ni/Cu-CNTs and Ni-CNTs was 89.34 dB, 72.21 dB and 55.62 dB, respectively.

Abstract:In this paper, the effects of deformation temperature, strain rate and height reduction on hot deformation behavior and microstructure revolution of as-cast AZ31B magnesiumSalloy were researched in terms of hot compression tests. The results show that the peak stress decreases with the decreasing strain rate and increasing deformation temperature, and the main nucleation mechanism consists of initial grain boundary bulging nucleation, sub-grain rotation nucleation, twinning induced nucleation as well as continuous recrystallization. Moreover, the deformation temperature is below 400_oC, the increase of temperature will beneficial to recrystallization and grain refinement, while as above 400_oC, grain sizeSincreases rapidly. Furthermore, the deformation temperature is equal or lesser than 400_oC, the lower strain rate of 0.1s_-1 is more beneficial to the recrystallized grain refinement, while above 400_oC, medium strain rate of 1s_-1 is more advantageous. In addition, it is found that at higher temperature and lower strain rate, height reduction primarily affects the grain size, and at higher temperature and higher strain rate, height reduction primarily affects the dynamic recrystallization degree.

Abstract:Ceramic shot and ceramic shot+cast-iron shot were employed to peen the turning surface of FGH96 powder metallurgy superalloy to induce 3 surface integrity statues. Surface topography, residual stress profile and high-temperature low-cycle fatigue performance were investigated of single shot peening (SSP), double shot peening (DSP) and turning statues. The results show that DSP removes turning masks, increases the average roughness Ra, and induce the crater with smooth bottom, which makes the Kurtosis parameter approach 3. Moreover as contrast, SSP with low intensity could only partially eliminate marks. Meanwhile, surface compressive residual stress values are -1000MPa to -1100MPa by SSP and DSP compared with -446MPa by turning, furthermore, the depth of DSP residual stress profile is 250μm, SSP and turning are 100μm. By the effect of perfect DSP surface integrity statue, fatigue cycles increase to 108% compared with turning, and the SSP edges up only 21% in the fatigue condition of 650℃/ε_t=1.2%. The fatigue life dispersion decreases after peening. The results of macro/microscopic observation and analysis show the fatigue propagation lifes are close of three surface integrity statues while the fatigue initiation lifes vary greatly. The initiation life of DSP is 221% of SSP and 216% of turning. It is important and necessary to optimize the shot peening method for surface integrity promotion and high temperature low-cycle fatigue performance improvement.

Abstract:Effects of sub-rapid solidification by water-cooling Cu mould on microstructure and mechanical properties of 6061 aluminum alloy with Mn and Zr addition were investigated. Microstructure of the alloys was analyzed by optical microscopy, scanning electron microscopy and EDS energy spectrum. Solubilities of Mg, Si and Mn elements in as-cast and homogenized Al alloys were estimated by X-ray diffraction and Vegard’s Law. Tensile tests were conducted to investigate the mechanical properties of 6061 aluminum alloy. Results showed that both the segregation of Mg, Si and Mn elements and homogenization time were decreased by sub-rapid solidification. The grain size had also been refined significantly by adding Mn and Zr elements. As-cast precipitated phase was transformed into α-Fe phase of granulate from β-Fe of bone and strip by water-cooling Cu mould., and they were maily granular α-Al₈(MnFe)₂Si和α-Al₈(MnFeCr)₂Si after homogenization treatment. Tensile properties of Al alloy with Mn and Zr addition casted by water-cooling Cu mould. The UTS, YS and Elongation of homogenized alloy researches to 286Mpa, 27Mpa and 17.84%, respectively.

Abstract:In present work, the hardenability and critical cooling rates of 7B50 alloy were investigated based on measured cooling curves obtained from the spray quenching test on modified Jominy specimen, electrical conductivity and hardness in different aging tempers, and microstructures evolution in natural aging temper. Results show that the hardened depth of 7B50 alloy is about 70 mm in natural aging temper while it decreases to 60 mm after natural aging for 50 days followed by artificial peak aging treatment with the corresponding average cooling rates in quench sensitive temperature range (420℃~230℃) increasing from 1.55℃·s-1 to 1.95℃·s-1, respectively, indicating worse hardenability and more quench sensitivity after artificial peak aging treatment. During water-spray quenching, the precipitates form firstly on grain/subgrain boundaries and then at some special positions in matrix, such as Al3Zr particles. The inhomogeneous precipitates on grain/subgrain boundaries are observed at a location of 3 mm from the quenching surface with the corresponding average cooling rate of 981℃·s-1. While inhomogeneous precipitates in matrix are observed at a location of 10 mm from the quenching surface with the corresponding average cooling rate of 37.75℃·s-1. Properties of the alloy at 25 mm from the quenching surface have little changed compared with those on the quenching surface and the corresponding average cooling rate at the location of 25 mm is 9.34℃·s-1 which is much smaller than that on the quenching surface. Therefore, during the spray quenching process, the average cooling rate of 7B50 alloy thick plates should be controlled to close to but not less than 9.34℃·s-1, in order to get excellent and uniform properties after quenching and aging.

Abstract:The effects of bipolar aging heat treatment on the microstructure and mechanical properties were studied on GH738 alloy repaired by laser deposition repair technology.The results show that :the microstructure of repair area present typical characteristics of the epitaxial growth of columnar crystals and the dendrite spacing is about 10μm.After the aging treatment, the repair area begins to grow and merge .The results of SEM analysis show that :There is no γ＇appear at the as-deposited , and the cubic MC type carbide is formed at the interdendritic, and the M23C6 type carbide at the dendrite arm ; After the aging treatment, γ＇phase precipitated at the repair area: γ＇phase with an average size of 37nm was found in the repair area, and the carbide precipitates in the grain boundary with the character of discontinued when the temperature of the stabilization step is 820℃; With the increase of the stabilization temperature, the size of the γ＇ and carbide increases ;When the temperature is 840℃, the average size of the γ＇is about 76nm, and the carbide is precipitated in the form of necklace ;Adding the temperature of the stabilization step to 860℃ , the average size of the γ＇does not increase obviously, and part of the γ＇ of is obviously coarsening and the size reach 150nm, meanwhile the carbides at the grain boundaries begin to form the closed. The results of mechanical property show that :the tensile strength of the sample increases obviously after aging treatment,and with the increase of the temperature, the tensile strength increases first and then decreases, and the elongation decreases continuously.

Abstract:LaFe11.85Si1.15 ribbons with large magnetic entropy change and minor magnetic hysteresis were prepared by melt-spinning technique followed by heat treatment. The influences of different heat treatment processes on phase constitution, microstructure evolution, magnetic entropy change, Curie temperature and itinerant electron metamagnetic transitions were investigated in details. It was shown that the annealed processes had a great influence on the content of 1: 13 phase and magnetocaloric effect. For LaFe11.85Si1.15 alloy prepared under the annealed time of 10 h at 1050 ℃, the maximum △SM value of 20.54 J/(kg K) and the refrigerating capacity of 417.21 J/kg can be acquired due to the high content of 1:13 phase in the magnetic field of 0-5 T, and the phenomenon of itinerant electron metamagnetic transition can be observed, obviously. The shorter annealed time is not beneficial in the formation of 1:13 phase. Meanwhile, too long annealing time can also lead to the decomposition of 1: 13 phase and increased of a-Fe phase.

Abstract:The SiC coating was deposited by high power plasma spraying (HPPS) on carbon/carbon (C/C) composites. Three sets of parameters were selected to optimize the properities of coating. The anti-ablation property of SiC coating was investigated by oxyacetylene torch flame at 1500℃. The phase composition, microstructure and component of coatings were analyzed by different methods included X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS) respectively. The results shows that the porosity of three sets of coating is 21.3%、17.4% and 15.3%. The plasma jet field has a more suitable temperature field and velocity field under the condition that the main gas flow is relatively high and the auxiliary gas flow is low. SiC powders were heated more fully to achieve better melting state and obtain larger kinetic energy. Therefore, the deposition rate of the coating increases gradually and the porosity decreases gradually. SiC powders were oxided to form amorphous SiO2. After been ablated for 300s，the SiC coating provide effective protection for the matrix. Because of the temperature gradient caused by the oxyacetylene on the surface of the sample, the coating forms three kinds of ablation morphology after ablation, including the central dense area, the transition area and the edge of loose area. During the ablation, a dense SiO2 glass layer generated on the surface of central area coating, which is beneficial to block the infiltration of oxygen.

Abstract:W-40vol%ZrC composites was prepared by spark plasma sintering (SPS) and ordinary consolidation sintering respectively. The relative density, mechanical properties and microstructure were studied. The resules show that high relative density, high strength and fine grains structure can be achieved by SPS which is reduced 200℃ to the ordinary consolidation sintering. The relative density, hardness, bending strength of W-40vol%ZrC composites sintering at 1600℃ was 98.56%, HRA78.1 and 501MPa respectively. The average grain sizes of W and ZrC was 3μm and 1.5μm. O-W40ZrC had the optimun value sintering at 1860℃, the relative of density, hardness and bending strength was 98.95%, HRA77.3 and 726MPa. The average grain sizes of W and ZrC was 10μm and 4.5μm. Compared with ordinary consolidation sintering, the tungsten grain is more fine and ZrC particles is much more well-distributed prepared by spark plasma sintering, and the fine grains has a beneficical effect on fracture process.

Abstract:Cotton fibers were firstly treated by nano TiO₂ coating via a dip-coating method, and then Pd nanoparticles (NPs) were deposited onto the surface of TiO₂/cotton fiber (TC) to acquire the Pd/TiO₂/cotton fiber composite (PTC) catalyst by a combined impregnation and NaBH₄-reduction method. The obtained PTC sample was used for room-temperature catalytic oxidation of formaldehyde (HCHO) and the influence of Pd content on catalytic activity was investigated. The results reveal that the air resistance of PTC catalyst is much lower than that of the powder-like sample, which is of vital importance for its actual application, and HCHO can be catalytically decomposed into CO₂ and H₂O over PTC. The catalytic activity of PTC increases with increasing of Pd content in the range of 0.25-1.0 wt%. Owing to the merits of low air resistance, light mass, flexible properties, good efficiency of the PTC catalyst, it can be a good candidate in actual indoor air purification and related catalytic processes.