Abstract:The Young’s modulus of implant plays an important role in reducing stress shielding. A new method called titanium mesh the stacked-forced-sintering (TMSS) was applied to porous titanium, which easily control Young’s modulus and balance the mechanical properties by different porosities, pore sizes and pore distribution. The results show that porous titanium has different structures in different directions. It has regular macro-pores in the cross section and irregular micro-pores in the longitudinal section. The stress-strain curve of porous titanium shows smooth and stable increase at plastic deformation along the axis direction. The young’s modulus obviously decreases, when increasing the porosity, decreasing nominal pore size, and changing pore distribution from regular to staggered at the same porosity. So the Young’s modulus of porous titanium can be adjusted by these architecture factors to match the different bone tissues, and the appropriate pore sizes have the potential to induce bone tissue ingrowth. The match of mechanical properties and appropriate structures can effectively promote the fixation between the implant and the bone tissue in a long term.

Abstract:The as-cast Mg-9Li-3Al-xSi(x=0,0.1,0.5,1.0 wt%)alloys were prepared in a vacuum induction furnace with the protection of argon. The alloys were then investigated by OM,SEM,XRD and mechanical properties test. Results exhibit that the as-cast Mg-9Li-3Al-xSi alloys are consist of α-Mg, β-Li, Mg17Al12 and phase. The addition of Si leads to the formation of new phase (Mg2Si) and the refinement of the grain. But if the content of Si is too high, α-Mg phase will coarsened, there are block and Chinese character shaped Mg2Si phase existing in the phase boundary. The temsile strength of alloys initially enhance and then decrease while the elongation declines with the increase of Si content. When Si addition is 0.1wt%, the tensile strength of the alloy comes to the maximum of 182.5Mpa, enhanced by 59.6% compared to the Mg-9Li-3Al alloy, while the elongation is 12.1%.

Abstract:The DyxPr2-xFe17 (x =0.0, 0.1, 0.2, 0.3, 0.4) powder were prepared by arc-smelting and high energy ball milling method. The phase structure, morphology, magnetic properties and electromagnetic parameters of the powder were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), vibrating sample magnetometer (VSM) and vector network analyzer (VNA), respectively. The results reveal that the saturation magnetization of the DyxPr2-xFe17 alloys decreases with the increase of Dy content. The minimum absorption peak frequency shifts towards higher frequency region upon the Dy substitution. And the minimum reflection loss of the DyxPr2-xFe17 alloys increases firstly and then decreases upon the Dy content. The Dy0.3Pr1.7Fe17 powder exhibits the best microwave absorbing properties. The minimum reflection loss of Dy0.3Pr1.7Fe17 powder is about -42.38 dB at 5.04 GHz, and the frequency bandwidth of RL < -10 dB reaches about 1.20 GHz with the best matching thickness of 2.5 mm.

Abstract:A facile visible-light-assisted method has been demonstrated to synthesize palladium (Pd) nanoparticles (NPs) with single-crystalline and multiple-twinned structures by reduction of PdCl2. The results showed that the formation of different nanostructures depend on reduction rate of the control. Unlike multiple-twinned Pd NPs, single-crystalline Pd NPs exhibit surface plasmon resonance (SPR) peaks in the visible region. Electrochemical properties of Pd NPs have been also investigated by cyclic voltammetry (CV). By comparison of the electrochemical parameters in the oxidation process of Pd NPs with single-crystalline and multiple-twinned structures, multiple-twinned Pd NPs exhibit the better electrocatalytic activity and anti-poisoning capability for ethanol oxidation.

Abstract:The effect of rare earth metals on mechanical and corrosion properties of 7085 aluminum alloy（Al-7.5Zn-1.5Mg-1.4Cu-0.15Zr）was investigated by means of optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Inter granular, exfoliation corrosion, hardness, tensile test and electrical conductivity test were performed on both Al alloys with and without rare earth additives. It was shown the Al alloys with rare earth metals are presenting better mechanical properties such as higher strength and hardness as a result of finer microstructure in comparison with those without the additives, and the electrical conductivity was slightly lower. The corrosion resistance was greatly improved after adding rare earth metals. Where inter granular corrosion resistance was enhanced from Level IV to Level II, the denudation level for 48h was improved from EB to PA and ISSRT reflecting stress corrosion resistance was enhanced from 65% to 96%.

Abstract:A new high strength titanium alloy include elements Cr, Fe Mo,W and Al was designed in order to achieve an excellent combination of ultra-high strength and good fracture toughness. Both the α/β and β heat treatment were intbilletuced to study the effect of microstructure on mechanical properties of alloy in this work. The result shows that the alloy with α/β solution plus aging treatment which composed of a mixture microstructures obtained a few equiaxed or short billet-like primary α phase and fine lamellar secondary α phase has excellent combination of ultra-high strength and good fracture toughness. The corresponding tensile strength is the superior strength about 1400MPa and fracture toughnesses K_IC is 50.7 Mpa.m_1/2. Compared with α/β heat treatment, the alloy with β region heat treatment presents representative Widmanstiitten structure which has higher fracture toughnesses and lower strengths than the mixed microstructures.

Abstract:In this paper, the solid phase diffusion reaction behavior between Ti and Al is characterized from 520 to 630℃ at different annealing time with titanium and aluminum being superfluous. In the samples annealed up to 46h, only intermeallic TiAl3 phase forms and grows at the Ti/Al interface. It was found that the growth rate of TiAl3 towards TiAl3/Al interface is more rapid than that towards the Ti/TiAl3 interface. Additionally, the solid-state diffusion reaction kinetic equation of TiAl3 is successfully established in the present work. The reaction activation energy of Ti/Al is calculated to be 170.1 kJ·mol-1 and dynamic index n is 0.5. Hence, the growth of TiAl3 is controlled by normal parabolic law with annealing time. Ti/Al powder compact is employed as experiment material to identify the proposed reaction kinetic equation for the growth of TiAl3. It is suggested that no extra aluminum was found in the specimen annealed at 590℃/4.5h, and the aluminum is still found at 590℃/3.5h, indicating that is in a good agreement with the developed solid-phase diffusion reaction equation.

Abstract:Micro-structural development of TC21 alloy after double alpha/beta solution and aging heat treatment was investigated. Primary alpha morphology was determined by the first solution treatment at the top of alpha/beta portion. Varying the cooling rates can significantly influence the volume fraction of retained beta phase and secondary alpha. Higher cooling rate resulted in greater retention of the beta phase and transformation of the phase into secondary alpha phase upon aging. This higher amount of fine, secondary alpha phase promoted higher strength and lower toughness. Second alpha/beta heat treatment temperature significantly influenced the heat treatment response of the microstructure. Higher heat treatment temperatures promoted greater amounts of retained beta with fine, transformed alpha in the final microstructures. Lower alpha/beta heat treatment temperatures promoted less responsive retained beta during aging process. Aging treatment promoted decomposition of retained beta phase, particularly in larger retained-beta regions that exhibited lower stability.

Abstract:Ni-based coatings with nano-sized feedstock rare earth element (RE, La2O3) addition were produced by laser cladding. Bed of high energy ball milling mixed Ni60A and La2O3 powders were pre-placed unto the substrate 30CrMnSiNi2A before laser cladding. La segregates in interdendrite thus secondary dendrites growth and ripening are limited. The microstructure is refined. Top surface of cladded coatings displayed better refined microstructure which caused by high La concentration, this phenomena is verified in EPMA results. And the results of EPMA reflected the interconnection between Fe dilution and decrease of coating microhardness. The cracks and pores cannot be found in cladded coatings in which microstructure refinement and purify effect caused by RE is clearly reflected in SEM microstructure, hardness and especially, the wear resistance test results. The COF of Ni60A-La coatings is apparently lower than substrate steel and Ni60A, the wear volume loss rate of Ni60A-La coatings is less than 1/10 that of 30CrMnSiNi2A and 1/5 that of Ni60A, respectively. The microhardness of Ni60A-La is about 4 times higher than that of substrate metal.

Abstract:In high temperature ablation process, the TiC coating will be oxidized to TiO₂. The thickness of molten TiO₂ increases when the temperature is higher than 2000℃, which decreases the bonding strength of coating. In this study, the TiC/ZrO₂ coatings with different content of high melting phase ZrO₂ were deposited by plasma spraying, in order to improve the anti-scouring property of TiC coatings. The phase structure, microstructure and composition of coatings, before and after ablation, were characterized by XRD, SEM and EDS, respectively. The ablation resistant mechanism of coatings with high melting phase ZrO₂ was discussed. The results indicate that the TiC/ZrO₂ coating shows good ability of ablation resistance, and its weight loss is only 1.5×10_-4 g.cm_-2.s_-1 at 2000℃. The ZrO₂ layer formed during the ablation can restrain the further oxidation of inner TiC and reduce the shearing force of oxyacetylene flame, which improves the anti-scouring property of coatings.

Abstract:Microstructures, elevated temperature mechanical properties and fracture mechanisms of the as-extruded ZM61-xSn (x=2, 4, 8, wt. %) alloys are investigated by optical microscope (OM), X-ray diffraction (XRD), scanning electron microscope (SEM) and high temperature tensile tests. The experimental results reveal that the addition of Sn can refine microstructures and the refinement effect increases with the increase of Sn content. The average grain size of the as-extruded ZM61-xSn (x=2, 4, 8 wt. %) alloys are 11, 8 and 4 μm, respectively. With increasing of Sn amount, the strength of experimental alloys increase at first and decrease afterward. ZM61-4Sn alloy shows the highest strength, which ultimate tensile strength and yield strength are 216 and 173 MPa tested at 180 ℃, respectively. The ductility increasing with the content of Sn increasing, the elongation of as-extruded ZM61-xSn (x=2, 4, 8 wt. %) alloys are 183.8%, 235.8% and 258.6%, respectively, when tensile temperature reaches 300 ℃. The ZM61-4Sn alloy has the optimal coalescent of strength and ductility. The localized necking leads the final fracture of the specimens and the micro-void coalescence is the main fracture mechanical. Incomplete dynamic recrystallization occurs when tensile tests are carried out at 260 and 300 ℃.

Abstract:A method for fabrication of ternary compound Ti3AlC2 powder by presureless calcining (PC) technique was developed. Powders of Ti, Al and TiC were mixed as staring materials. The effect of calcining temperatures and aluminum content on the purity of Ti3AlC2 was discussed in detail. The reaction mechanism and the microstructure evolution of Ti3AlC2 prepared at different temperature were investigated by X-ray diffraction, field emission scanning electron microscopy and high resolution transmission electron microscopy. Results indicate that the single-phase polycrystalline Ti3AlC2 powder was obtained at 1300 ℃, which perform a typical laminated structure, and the best molar ratio of raw Ti/Al/TiC materials was 1:1.2:2. The bulk samples sintered by hot pressing were using the Ti3AlC2 powder. After hot pressing of different temperature, the fully dense of bulk Ti3AlC2 showed the best properties prepared at 1300 ℃. The density of bulk Ti3AlC2 reached to 99.9%. The average Vickers hardness was around 5.7 GPa, and the maximum flexural strength was over 630 MPa. Finally the strengthening mechanism of the bulk Ti3AlC2 was also proposed.

Abstract:Ti-Ni-based amorphous composite samples (Ti0.5Ni0.5)100-XCuX with the same CuX but the different diameters which had been prepared successfully by the copper mold suction casting were used to study the effect of their Cu contents (X=0, 10, 15, 20, 25, 30, 35 and 40) on the microstructures and mechanical properties of such amorphous composites. The results show that both fracture strength and plastic strain of the alloy are very high while the copper content is x=20. And the alloy exhibits the best comprehensive properties. As the x values increase, the glass forming ability of (Ti0.5Ni0.5)100-XCuX alloy shows a waveform change from increasing to decreasing and then to increasing, but following an overall trend towards decreasing. The plasticity of Ti-based amorphous materials can be improved by adding Cu element in modest quantities (x = approx. 25) to the Ti-Ni-based composites; however adding more numbers (i.e., x > 30), neither can improve the amorphous forming ability nor can enhance its strength. When x = 15, the alloy has the highest breaking strength of 2,440 MPa while reach the higher yield strength of 1471 MPa and cause a 17.15% plastic strain. The data are pretty high with respect to other amorphous systems or other alloy systems with memory of their shapes. When x = 25, there is a certain increase in the alloy plastic strain, whereas underwent a 21.35% plastic deformation.

Abstract:Based on fusion bonding and atomic interdiffusion between the ceramic and stainless steel, the TiB2-based ceramic/1Cr18Ni9Ti stainless steel composite with chemical composition gradient was produced by combustion system in ultra-high gravity field (CSUGF). The presence of chemical reaction in explosive combustion and the subsequent thermal-vacuum circumstance induced by liquid products in ultra-high gravity make stainless steel partially fused, resulting in the achievement of fusion bonding. XRD, FESEM and EDS results show that the interface has a good bonding, and the intermediate exhibits three dimensional network ceramic-metal graded microstructure considered as a result of intensive interdiffusion of atomics. Vickers hardness profile reveals the quasi-parabola relationship of the hardness to the testing distance from the ceramic matrix to the steel substrate. Meanwhile, interfacial shear fracture of the composite presents the mixed mode consisting of intercrystalline fracture along TiB2 platelets and ductile fracture in Fe-Ni-Cr alloy, presenting interfacial shear strength 325±25 MPa.

Abstract:As the most common grain boundary strengthening elements in Ni-based superalloy, C and B are inclined to form carbides and borides with other elements, thus influence the mechanical performance of superalloy. In this paper, the evolution of the carbides and borides in a Ni-based superalloy during creep is studied. Through analyzing the creep mechanism at different conditions, and comparing the morphology, distribution and crystal structure of carbides and borides before and after creep tests, the influences of creep condition on the precipitation and evolution of carbides and borides are investigated, and the effects of carbides and borides on the creep properties of Ni-based superalloy are revealed.

Abstract:Fatigue crack growth rates of alloy 690 have been generated in air at room temperature (RT)，in air at 325℃ and in deoxidized ultrapure water at 325℃ based on direct current potential drop (DCPD) method. The results have been analyzed by Priddle model, thus the threshold of stress intensity factor amplitude (△Kth) and the fracture toughness (Kc) were obtained in these three conditions. Results showed that, fatigue crack growth rates were accelerated in water environment, which could be explained by slip dissolution mechanism. In higher temperature, fatigue crack growth rates were also accelerated because material strength was weakened which lead to decreasing in △Kth and Kc. Scanning electron microscopy (SEM) examination of the fatigue fracture surfaces revealed similar slipping ledges with transgranular cracks for specimens in air, and different crack surface with both intergranular and transgranular cracks in water environment.

Abstract:The nanostructure and chemical compositions of Ni-based superalloys are investigated utilizing APT instrument LEAP 4000X Si. The article contains the following four contents: nanostructure of γ''-precipitates, refractory elemental partitioning, coherent γ/γ'' interface and clustering and ordering of atoms. Our results demonstrate that it is possible to yield unique and quantitative high quality information in the study of Ni-based superalloys from APT.

Abstract:In this study, critical pitting temperature (CPT) of G3 alloy under high temperature and high H₂S/CO₂ pressure environments was assessed using potentiostatic and electrochemical impedance spectroscopy (EIS) techniques. EIS measurements were carried at anodic potential of 150 mV vs. E_corr and the results were compared with those of potentiostatic polarisation. The results revealed that the CPT of G3 Alloy under high temperature and high H₂S/CO₂ pressure environments was 58.5 _oC in potentiostatic method and between 50-60 _oC in EIS method. Both potentiostatic polarization and EIS methods give an almost identical CPT value.

Abstract:The tensile tests and microstructure evolution of as-extruded Mg-3Al-3Zn-1Ti-0.6RE magnesium alloy at elevated temperature were conducted on WDW3100 microcomputer control electron universal testing machine and Zeiss microscope at strain rates ranging from 10-4 s-1-10-2s-1 and deformation temperature of 623K-723K. The result has shown that temperature and strain rate are the important factors influencing the rheological stress. During the process of deformation, the flow stress decreases with the increase of temperature and the decrease of strain rate. Under this experimental condition, the deformation constitutive equation of the alloy can be described by hyperbolic sine function.Among them, the stress exponent and the activation energy of the as-extrude alloy are 3.286 and 238KJ/mol. The most important deformation mechanism of this alloy is dislocation slip and climb.

Abstract:In this paper, based on the first-principles density functional theory, the crystal structures, band stuctures and chemical bond properties of high-temperature phase(short for α-LiHB), low-temperature phase(short for β-LiHB) in LiN₂H₃BH₃ and LiNH₂BH₃(short for LiAB) materials for hydrogen storage have been studied. The caculated hydrogen removal energies showed that H_δ+(N₁), connected with Li , played a major role in the intial stage of dehydrogenation and low-temperature phase β-LiHB was easier to desorpt hydrogen than high-temperature phase α-LiHB. Then, HOMO and LUMO caculated by Dmol₃ indicated that dehydrogenation of α-LiHB was through H-N₁…B and H-N₂…B, while β-LiHB and LiAB were only through H-N₁…B. The energy gap of HOMO-LUMO suggested that chemicalSstability of LiAB, α-LiHB and β-LiHBH was: LiAB＞α-LiHB＞β-LiHB. All the researches provided theoretical basis for the synthesis of polyphase LiHB in some way.

Abstract:In order to investigate more effective and thinner protective coatings preparation for uranium laser targets, nano-Al coatings prepared by magnetron sputtering were researched, single-layer of Al and DU, Al/DU/Al “sandwich” film samples were prepared, oxidation resistant of nano-Al coatings Al/DU/Al samples under atmosphere environment was investigated. The surface topography, atomic concentration and atomic concentration’s change, and phase composition of these samples were characterized by SEM, XPS and XRD. The results show: Al coating becomes continuous when its thickness exceeds 10 nm, grain size of Al coatings increase with thickness. 30 nm thick Al protective coating effectively avoids DU layer oxidation, no obvious increase of DU layer’s oxygen content under atmosphere environment was found within 72 hours.

Abstract:Corrosion behavior of U-Ti alloys in standard salt spray environment was investigated by laser scanning confocal microscope (LSCM), scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS), respectively. The results show that U-Ti alloys presented heterogeneous corrosion in the environment and corrosion extend of the alloys was mainly affected by thickness of liquid film and exposure time. Pitting corrosion was the main corrosion type for initial corrosion behavior of U-Ti alloys and corrosion extend was more grievous with the increasing thickness of liquid film and longer exposure time. Localized corrosion and the cracks of corrosion products occurred in the surface of U-Ti alloy. The U4f spectras of U-Ti alloys in two typical regions as a function of etching time show that the composition is U₃O₈/UO_2+x/UO₂/U in black region while the composition is UO_{2 x}/UO₂/U in yellow region.

Abstract:It is one of the goals for science researchers to improve the glass forming ability (GFA), overcome the limit to dimensions of metallic glasses and search for a simple and reliable gauge for quantifying the GFA of metallic glasses. In the work, five kinds of Zr based BMGs with different GFA, which were Zr_41.2Ti_13.8Cu_12.5Ni₁₀Be_22.5、Zr₅₅Al₁₀Ni₅Cu₃₀、Zr₄₅Cu₄₅Ag₅Al₅、Zr₆₅Al_7.5Ni₁₀Cu_17.5、Zr₅₇Ti₅Al₁₀Cu₂₀Ni₈ respectively, were used to study the relationship between GFA and internal friction (IF). By comparing the internal friction-temperature curves of different samples, it is found that the higher the value of IF peak is, the better the GFA is. Compared with the activity energy evaluated during the supercooled liquid, the nature of internal friction shows the reason of metallic glass with high GFA. So a new criterion evaluating the GFA is proposed, i.e. internal friction peak. Besides, based on the internal friction-loading frequency curves of five samples, the behavior of mechanical relaxation was discussed. It is showed that the more GFA is, the more the number of instability atoms in the supercooled liquid is, the shorter the time of mechanical relaxation is.

Abstract:In this paper, the NaAl(NH2)4 phase is successfully prepared from NaAlH4 reacting in liquid ammonia at low temperature, and the XRD pattern and FT-IR was used to the characterization. The decomposition process of the NaAl(NH2)4 were studied By thermoanalysis, XRD pattern and FT-IR, and product analysis of as-prepared samples at different temperature heat treatment. The experiments show that: The thermal decomposition of NaAl(NH2)4 under primary vacuum leads to the release of NH3 and completed at 250癈 with Two moles of NH3 released. Meanwhile, intermediate NaAl(NH)2 was amorphous and decomposed at about 113.8 ℃. In the complex NaAl(NH2)4, [NH2]? is covalently bonded with Al, and the same to N-H bone. In the pyrolysis process, [NH2]? - Al bone prior to break up, that lead to the formation of NH3. The final pyrolysis products of NaAl(NH2)4 is NaNH2, AlN and NH3.

Abstract:First principles based on density functional theory, the establishment of Al2O3 and RuO2 crystal cell model. the alloy oxide of Al2O3 and RuO2 that the internal oxidation of RuAl, The results show:the oxidation energy of Al2O3 to -11.43eV,the oxidation energy of RuO2 to -2.28eV, Al2O3 is more stable than the structural stability of RuO2.Through the analysis of density of States, charge density of Bander,W alloy to enhance the antioxidant properties of RuAl is the fundamental reason: due to the adsorption effect of W on the O, the W around the Al-O and Ru-O bond strength decrease,the Oxidation energy of Al2O3 and RuO2 can be reduced, In order to reduce the structural stability.Among them, the Al2O3 structure stability significantly decreased.At the same time, the alloying of W can reduce the structure stability of Al2O3 Within the RuAl alloy matrix system. Blocking the formation conditions of oxidation process in the generation, reduce the formation of surface perpendicular to the interface of Al2O3, the transverse direction the surface interface on Al2O3 oxide layer growth, the formation of Al2O3 continuous dense oxide layer, improve the oxidation resistance of RuAl.

Abstract:Porous NiTi alloys have broad potential application in the biomedical field due to their good biocompatibility and unique mechanical properties. Porous NiTi alloys were successfully prepared by using Micro-FAST which can realize the sintering process in a short sintering time at a low cost and in a environmental-friendly way. It was found that with the increasing sintering temperature, the porosity of the porous NiTi alloys decreased firstly, then increased and slightly reduced finally. Undesired NiTi2 and Ni3Ti phases were formed and decreased gradually with a trend to form single NiTi phase. At the sintering temperature of 1100℃, the porous NiTi alloys exhibited well-distributed pores. With the increasing holding time, the porosity increased significantly to 32.2% and the pore sizes were about 100μm, which meets the requirement of human bone implants.

Abstract:Single phase vanadium dioxide (VO₂) thin film was fabricated by radio frequcecy magnetron sputtering method on silicon single crystal, the transition magnitude is beyond 2 orders. VO₂ thin film was annealed in nitrogen by rapid thermal annealing method. X ray diffraction, scanning electron microscopy, high resolution transparcy electron microscopy and four pobe method were used to characterize the crystal structure, morophology and electrical properties, respectively. The results show that, the phase transition properties were affected heavely by temperature at rapid thermal annealing mode. The magnitude of phase transition in sheet resistance increases from 2.3 to 2.4 orders when rapid thermal annealing at 300 ℃, and when the temperature beyond 350 ℃, the order of magnitude decrease to lower 1, at 500 ℃ the phase transition disappear. The composition of VO₂ thin films change form VO₂ to V₄O₇. SEM results show that the hole structure in film doesn’t change and the particle size also keep the same size during annealing at different temperature. The results are important for VO₂ application in envirment with fast change of temperature.

Abstract:Double-wires plus arc additive manufacturing(D-WAAM) system for Al-Cu-Mg alloy using variable polarity gas tungsten arc welding(VP-GTAW) process was established. Al-6.3Cu and Al-5Mg wires were employed as filling metal, the microstructure and mechanical properties of as-deposited D-WAAM samples were analyzed. Experimental results show that the excellent deposits wall samples can be achieved and the deposition efficiency can be improved by using D-WAAM process. Al-Cu-Mg alloys with different element content of copper and magnesium were obtained by adjusting the two wire feed speed. The microstructures of Al-Cu-Mg deposits were mainly composed of columnar dendrite and equiaxed dentrite grains with the non-uniformly distribution characteristics. Mechanical properties can be enhanced due to the addition of alloying of element magnesium. The microhardness of as-deposited Al-Cu-Mg alloy was 90-100 HV. The UTS, YS and elongation of as-deposited D-WAAM alloy can be increased to 286 MPa, 183 MPa and 4.5%, respectively.

Abstract:Crack can constantly expand and then cause invalidation, even cause catastrophic damage under the reciprocating loading. Based on remanufacturing, high energy pulse current impacting device was used to treat 316 austenitic stainless steel containing prefabricated unilateral fatigue crack. The influence of high density pulse electric current on the microstructure at crack tip was investigated by means of metallographic microscope, X-ray diffraction, electron backscattered diffraction (EBSD) and transmission electron microscope (TEM). And the evolution of microstructure by melting treatment was analysized. Results show that the sturture at crack tip obviously became refinement after the pulse current processing, and the gradient structure including the columnar crystal area, recrystallization zone and matrix was observed. Due to the rapid heating and cooling, the generation of high-speed electronic wind, electrically induced plasticity effect, the thermodynamic barrier of recrystallization or phase change was reduced by pulsed current treatment. The rate of nucleation was increased, inhibiting the grain growth process. Therefore the grain size of recrystallization zone was smaller than that of the matix, and hence the mechanical properties of materials was improved.

Abstract:The microstructure and melting characteristic of the Ti-25.65Zr-13.3Cu-12.35Ni-3Co-2Mo fillers prepared via casting and rapid solidification technology, as well as the interfacial microstructure of the brazed γ-TiAl joint were analyzed by SEM, EDS, XRD, TEM and DSC. The tensile strength of the brazed joint was also evaluated. The results show that the Ti-25.65Zr-13.3Cu-12.35Ni-3Co-2Mo filler prepared by rapid solidification is fully amorphous. The amorphous filler shows thinner melting temperature interval and better wettability to γ-TiAl compared with the crystalline filler. The joints brazed with crystalline and amorphous fillers are both composed of a central brazed layer II between two interfacial reaction layers I, and the tensile strength first increases and then decreases in the brazing temperature range of 925 - 1050 °C for 10 min. However, the tensile strength of the joints brazed with the amorphous filler is always much higher than that with the crystalline filler, and it obtains a maximum value of 302 MPa at temperature of 1000 °C with a holding time of 10 min.

Abstract:Effects of high strain-rate rolling on microstructure, mechanical properties and corrosion resistance of Mg-4Zn alloy were investigated by optical microscope (OM), scanning electron microscope (SEM), mass loss of immersion test and tensile testing. The results showed that high strain-rate rolling after solution treatment produced homogenous dynamic recrystallization (DRX) with final grain size of 4 μm leading to a significant mechanical property improvement. The tensile strength, yield strength and elongation were 285MPa, 180MPa and 27.4% respectively. The solutionized and the as-rolled alloys had better corrosion resistance than the as-cast, exhibiting a uniform filiform corrosion due to the lower fraction and the finer size of the second phase. The as-rolled alloy showed the best corrosion resistance with the average corrosion rate of 0.25 mg/cm2.d, about 1/5 of the as-cast alloy after soaking in Hank’s solution for 15 days. It also showed the highest residual tensile strength ( 215MPa), far above the as-cast and the solutionized alloys.

Abstract:In this paper, the dynamic mechanical properties and sensitivity of adiabatic shear banding of TC4 alloy having bimodal microstructures were invesgated using Split Hopkinson Bar.The bimodal microstructures with different volume fraction of transformed β matrix were obtained via different heat treatment. The results showed that the volume fraction of transformed β matrix increased with the increasing of solution temperature. Under dynamic compression experiments, the dynamic strength rised at first and went down latter as the volume fraction of transformed β matrix increased, and reaches its maximum value when the volume fraction of transformed β matrix was 80.7%. While the dynamic strain decreased with the increasing of volume fraction of transformed β matrix. Under forced shearing experiments, the sensitivity of adiabatic shear banding decreased at first and increased latter as the volume fraction of transformed β matrix increased, and reached its minimum value when the volume fraction of transformed β matrix was 80.7%. Besides, the sensitivity of adiabatic shear banding increased for the same microstructure with the increasing of impact velocity.

Abstract:Abstract: A series of experiments are conducted on as-cast titanium alloys β20C, TC4, TA15 and TA18, including the ballistic test, the dynamic compression test, the quasi-static tensile test, as well as the quasi-static compression test. Based on the experiments, factors affecting the ballistic performance of as-cast titanium alloys are compared and analyzed. The results show that as-cast titanium alloy β20C has the minium of DOP, which is 4.7mm, about 22%, 37% and 23% less than that of as-cast titanium alloys TC4, TA15 and TA18, respectively. Besides, mass efficiency of β20C is 2.61 which is the maximum among the four as-cast titanium alloys, indicating that β20C has the best ballistic performance. Furthermore, dynamic compression strength, quasi-static compression strength and quasi-static tensile yield strength together with quasi-static tensile strength of β20C are 1578MPa, 1474MPa, 1052MPa and 1101MPa, respectively, larger than the corresponding values of the other three titanium alloys. While the impact absorbing energy, dynamic ductility and critical fracture strain and fracture elongation don’t reflect the ballistic performance very well.In addition, the cratering size of the target frontage of β20C is 10×12mm, being the biggest one among the four as-cast titanium alloys, without obvious shearing plugging damage.

Abstract:In this paper, the effect of microstructure on the room-temperature hydrogen absorption behavior of Ti-6Al-4V alloy was studied through electrolytic hydrogen charging method. The results show that Ti-6Al-4V alloys with different microstructures show obviously different room-temperature hydrogen absorbing ability. The hydrogen absorbing ability of the alloy with duplex microstructure is the weakest and that of the alloy with widmanstatten microstructure is the strongest at room temperature. The influence of the microstructure characteristics of β phase is stronger than that of α phase on the capability for room-temperature hydrogen absorption. The Ti-6Al-4V titanium alloy with duplex microstructure should be the one with a perfect resistance to the hydrogen embrittlement.

Abstract:Kaolinite composites MK/Co-P and SK/Co-P were prepared by pretreatment and electroless deposition on two type of natural kaolinite produced from Maoming and Suzhou respectively. Their microstructures, magnetic properties and microwave absorption abilities were studied and compared. The results indicated that both kaolinite composites contained single phased Co-P coatings with hexagonal-closed-packed structure. In MK/Co-P, Co-P coatings were deposited on the surfaces of kaolinite flakes uniformly, where the contents of cobalt and phosphorus were determined to be 36.62 wt.% and 4.41 wt.%, respectively. By comparison, kaolinite microclusters were covered completely by Co-P coatings in SK/Co-P and the contents of Co and P were both decreased noticeably. In contrast to SK/Co-P, MK/Co-P shows enhanced saturation magnetization and coercivity together with much improved permittivity and permeability. It presents a maximum reflection loss of -27.32 dB and a effective absorbing bandwidth (reflection loss below -20 dB) covering 4.7 ~ 8.2 GHz at the thickness range of 2.0 ~ 3.0 mm, which would be suitable for applications in microwave devices.

Abstract:A 100-meter-long Ni-5at.%W (Ni5W) alloy tape with ~66μm thickness had been fabricated successfully by Rolling assisted bi-axially textured substrate route technique. A 10m long section was taken from the original piece and recrystallized in a home-designed reel-to-reel heat treatment system. The XRD texture characterization showed that the average content of rolling textures was 63.8% (≤10°) before annealing, and the average FWHM values of the in-plane and out-of-plane texture over the annealed tape length were 7.2° and 6.1° respectively. Moreover, EBSD analyses determined that the content of the cube texture reached 98.7% (≤10°) and that of the grain boundaries exceeded 87.7% (≤10°). In the cold-rolling process, increasing the reduction in the first pass while changing to another mill can effectively reduce the broken cases. These results will prove that the process described in this work has the ability to yield Ni-5at.%W tapes with a high cube texture and homogeneous qualities, which will be able to satisfy the requirements of the YBCO superconductive layer.

Abstract:Using tungsten oxide, cobalt oxide and carbon black as raw materials, the ultrafine WC-η composite powder was rapidly synthesized by the novel technique of in situ reactions. Under the optimized process conditions, the as-synthesized composite powder has a mean particle size of 260 nm, containing only WC and η phases. Then the composite powder was agglomerated into the thermal spray powder with high density and good flowability. Using this powder as the feedstock, the ultrafine-structured WC-based coating was fabricated by high-velocity oxy-fuel spraying technique. The fabricated coating has an average hardness as high as (1406±34) HV_0.3 and only a porosity of 0.3%. The results indicated that the ultrafine-structured WC-based coating exhibited excellent corrosion resistance to molten zinc. The corrosion mechanism can be explained by the slow dissolving of the coating matrix from the surface layer to the inner area caused by the diffusion of molten zinc along micro-cracks, which was then followed by the formation of penetrative cracks and subsequent massive exfoliation of coating materials.

Abstract:The effect of heat treatment on the microstructure and mechanical properties of an Nbss/Nb5Si3 in situ composites prepared by HRS method was investigated. The microstructure evolution of samples during heat treatment process were analysed by SEM、XRD and EPMA: the result showesd that the as-cast alloy consisted of Nbss、γ-Nb5Si3 、β-Nb5Si3 and primary carbide phase; after heat treatment, the β-(Nb,Ti)5Si3 phase was transformed to α-(Nb,Ti)5Si3 phase and the secondary carbide was precipitated. Meanwhile, the silicide phase gradually dissolved or broken into small pieces, with the morphology changing from the needle into granules. The transformation (Nb,Ti)5Si3 →(Ti,Nb)5Si3 occurred when aging at 1150℃.The compressive strength and room temperature tensile strength of heat-treatment specimens were improved, while the tensile strength of as-cast and heat-treated samples at 1000℃ was at same level. The temperature has a great influence on the fracture mode, cleavage fracture at low temperature and ductile fracture at high temperature.

Abstract:Ti-Al-Nb alloy coating is successfully fabricated on the surface of TC4 titanium alloy by laser alloying using Ti, Al, Nb milled powders as the raw material. The phase composition, microstructure and micro-hardness of the coating are investigated. The friction wear property of the coating is tested with the YG6 ball as counter-body under dry lubrication. The results show that under the laser power 1.8kW,scanning speed 5mm/s and spot diameter 2mm, the coating is uniformdense and crack-free, and it has a good metallurgical combination with the TC4 substrate. Microstructure of the coating mainly consists of Ti₃Al, AlNb₂ and α-Ti. The micro-hardness of the coating (between 580 ~ 630HV) is significantly higher than that of the TC4 matrix (350~360HV). The friction coefficient of Ti-Al-Nb coating is reduced (0.33 vs. 0.45) and the wear resistance is 2.95 times greater than that of the substrate.

Abstract:TNZS, TiO2/TNZS and HA/TNZS mixed powders were prepared by high-energy milling for 48 h and then sintered by cold pressing. microstructure and phase of TNZS mixed powders and microstructure, phase, pore characteristics and elastic modulus of TNZS-based biomaterials were investigated. The results show that: the three mixed powders are mechanically alloyed after high-energy milling for 48 h; sintering TNZS generates α-Ti phase and β-Ti phase, sintering TiO2/TNZS produces α-Ti phase, β-Ti phase, rutile TiO2 and anatase TiO2; besides of α-Ti, β-Ti and HA, HA/TNZS bio-titanium-based material forms new phases of Ti2O, CaTiO3, CaO and TixPy; the surface composition of the three materials are uniform; porosity of three materials are 2.466%, 5.030% and 13.027%, respectively; elastic modulus of three materials are 64.00 GPa、103.93 GPa and 119.43 GPa, respectively.

Abstract:A Mo surface-modified layer onto Ti-5Zr-3Sn-5Mo-15Nb (TLM) substrate was prepared by plasma surface alloying technique. The microstructure, component distribution and micro-hardness of the Mo modified layer were analyzed. Contact angles with deionized water were measured, and wear behavior of the samples against corundum ball in simulated human body fluids was investigated. The results indicate an about 12 μm uniform Mo surface-modified layer was obtained, which was mainly composed of Mo phase. The surface hardness of Mo alloyed TLM increased significantly than that of untreated TLM, and the contact angle was lowered due to the generation of Mo layer and the increase of surface roughness, enhancing the surface wettability. More importantly, compared to as-received TLM alloy, the Mo modified alloy exhibited significant improvement of wear resistance, about 50 times, with lower friction coefficient.

Abstract:Nickel was continuously plated via magnetron sputtering and electroplating on the surface of Ta-based alloy processed by micro-arc oxidation, and its effects on the thermal shock resistance of the ceramic scale formed on the surface of Ta-based alloy to molten nickel was investigated. The results showed that the ceramic scale with a thickness of 30~35μm prepared by micro-arc oxidation was mainly Ta₂O₅. Although the ceramic layer was continuous and bonded well to the alloy substrate, severe cracking and peeling occurred when it contacted with the molten nickel during casting, which caused the melting of the Ta-based alloy. Fortunately, the thermal shock resistance of the ceramic scale to molten nickel was greatly improved by the plated nickel layer with a thickness of 20~30μm. The ceramic scale was still continuous and integrity after nickel casting. Thus, the nickel plating can be used as a protection coating for the ceramic scales on the Ta-based alloy prepared by micro-arc oxidation in molten nickel environments.

Abstract:To study the effects of nickel content on microstructural evolution and γ′ dissolution of Co-Al-W base alloys, the microstructure,γ′ precipitates transformation temperatures, γ′ precipitates microstructural evolution and microhardness of Co-Al-W base alloys with aging treatment were analyzed by using scanning-electron microscope(SEM) and X-ray diffraction(XRD) etc. The results showed that with the increase of Ni,γ ′ solvus temperature increased at different degree and the volume fraction of γ′ precipitates increased gradually. The solidus temperatures andγ′ precipitates morphology of four Co-Al-W base alloys are nearly unchanged. When the nickel content in Co-8.8Al-9.8W alloy reaches 25%γ′ precipitates transformation temperatures increased to 1100℃. The typical of γ/γ′ two-phase micro-structure is generated in four alloys after the heat treatment at 900 ℃ for 50 h. When prolonged aging at 900 ℃ for 100 h , the γ′ precipitates volume fraction decreases to different degree and there is an obvious phenomenon of the γ′ precipitates become coarsen as a function of Ni concentration . The microhardness results of the four alloys after heat treatment at 900 ℃ for 50 h and 100 h indicate that the microhardness is risen from 5Ni to 15Ni alloy, lowered in alloys with higher Ni content. With the aging treatment time prolonged from 50h to 100h, the microhardness of alloys becomes small.

Abstract:SnO2-Sb2O3-RuO2/Ti thin film electrode was prepared by thermal decomposition method in this paper. It is used to treat Amaranth dye simulate wastewater. The decolourization efficiency of amaranth is studied and the optimal operating conditions of the electrode are ascertained as follows: the sintered temperature is 500℃, the optimal coating layer is 6, the coating oxides proportion is n(Sn):n(Sb):n(Ru)=10:1:1. The surface morphology, microstructure, electrochemical and accelerated test shows that the surface of the SnO2-Sb2O3-RuO2/Ti electrode has the quartet rutile structure, even crystal size, good adhesion, low porosity and high catalytic-activity and long service-life .

Abstract:The effects of B addition on the lattice constant, grain size and electrical property of Al-Si casting alloys were investigated by Wheatstone Bridge Conductivity Measurement, Optical Microscope, Scanning Electron Microscope(SEM), Transmission Electron Microscope(TEM),X-Ray Diffraction(XRD) and Electron Probe Micro-Analyzer(EPMA) Analysis. The results indicated that impurities of Ti,Cr,Mn,V were converted from solid solution state to boride in the Al matrix when B content was increased in the range of 0.02%, meanwhile, the degree of lattice distortion decreased which resulted in the increase of the conductivity by 6.06%; When B content was over 0.02%, B and Ti formed TiB_2, TiB₂ promoted the formation of Al₃Ti phase with the increase of B content, which led to grain refinement, crystal distortion increased, the risk of electron scattering enhanced and the excessing of B dissolved in the Al matrix simultaneously, so the conductivity decreased by 2.5%; when B content was 0.02%, the alloy’s electrical property achieved the best and the tensile strength have not reduced, the conductivity was 33.00%IACS.

Abstract:Ni60 alloy layers with different contends of rare-earth CeO₂ were prepared on the surface of 6063 aluminum alloy by using laser additive manufacturing. The effects of rare earth CeO₂ addition on microstructure, phase structure and corrosion resistance of bonding interface between Ni60-CeO₂ alloy layers and substrate were investigated by means of OM, XRD,SEM and electrochemical corrosion tester. The results show that on the surface morphology, 4%~5% CeO₂+Ni60 alloy layers have the best morphology, it is difficult to obtain a good alloy layer when the CeO₂ content of less than 3% . It is less surface pores, shedding and other defects when CeO₂ contents of 5% to 10% . On the cross-section morphology, the alloy layers prone to cracking at 0% to 2% CeO₂ content, the main defect is porosity when the content of 5% to 10%, 4% CeO₂ Ni60 alloy layer have no obvious pores and cracks, with a relatively good cross-section morphology. Adding 4% CeO₂ can improve the organizational structure of Ni60 alloy layer, promote grain refinement and compositions evenly distributed. Adding different contents of CeO₂ can improve aluminum surface morphology in Ni60 alloy layers, the preferred amount of rare earth CeO₂ is add 4% CeO₂. Electrochemical corrosion tests show that, the corrosion resistance of CeO₂ Ni60 alloy layer was 4.25 times as that of Ni60 alloy layer in 1mol/L H₂SO₄ solution. In 3.5% NaCl solution, the corrosion resistance of CeO₂ Ni60 alloy layer was 1.4 times as that of Ni60 alloy layer. In 1mol/L NaOH solution, the corrosion resistance of CeO₂ Ni60 alloy layer was 1.43 times as that of Ni60 alloy layer.

Abstract:The oxidation behavior of Ti40 alloy in 1000~1500℃ were researched. Analysis the organization and the elements change of the oxide surface and from surface to matrix with OM,XRD and EDS. The results shows that the oxide surface has the evaporation of the V₂O₅, grow up of the TiO₂, and due to the stress exceed the oxide film strength makes the oxide film cracking and spalling. When the oxide film spalled, The TiO₂ and Cr₂O₃ mix oxide layer become the new oxide layer, It with the enrichment layer of V, Cr elements have a good ability to resist the O element getting to the matrix.

Abstract:In order to prepare longer TiO2 nano-tube, Ti sheet was anodic oxidized under direct voltage of 20V in solution of 0.5(wt)％NaF＋glycerin for 7h, in the temperature of 0℃,20℃ and 40℃ respectively. The results of SEM show that the length of the TiO2 nano-tube are 1.034μm,2.601μm and 5.152μm for 0℃,20℃ and 40℃ respectively. The results of pH test show that diffusion coefficient of solution increases with temperature increasing, diffusion of H+ speed up near the Ti sheet, so the rate of pH reduction slow down. In the temperature of 40℃, in solution of 0.5(wt)％NaF＋glycerin, TiO2 nano-tube can grow to about 10μm for 12h, and surface ratio achieves 208 m2.g-1.

Abstract:Three-dimensional Ru nano flowers are formed by nano sheets originating from the Ni-YSZ anode layer. The nano flowers are utilized as a functional layer for direct ethanol solid oxide fuel cells (DE-SOFCs). The morphology and structure of as-prepared catalysts are characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD), which verified that the flower-like RuSnano layer is uniformly dispersed on Ni-YSZ surface. These nanostructures show very interesting performance properties for direct ethanol solid oxide fuel cell. With 0.6wt.% Ru in anode, the cell peak power density reaches 264 mSWScm_?S2 wet ethanol fuel at 750S°C. The fuel cell power density reaches 200, 261 and 316mW /cm₂ at 700,750 and 800_oC,respectively. By dispersing a 0.6wt.% Ru layer into anode, the performance of fuel cells is improved and kept stable at open circuit voltage (OCV) for 15 hrs without carbon deposition.

Abstract:Lithium-ion batteries (LIBs) are efficient and clean energy storage devices, and are promising for various applications such as consumer electronic products, energy storage facilities and electric vehicles, etc, which are significant to relieve the energy crisis and environmental pollution. Olivine lithium iron phosphate (LiFePO4) is one of the most promising positive electrode material for LIBs. However, the intrinsically low electronic conductivity and lithium ion diffusion velocity result in poor performance of LiFePO4 and block its large-scale commercialization application for power LIBs. Nano-structured morphology control is believed to be an effective modification method to improve the rate performance of LiFePO4, nevertheless, LiFePO4 nanoparticles display some disadvantages such as high surface energy, easy to agglomeration and fast specific capacity degradation, etc. Studies in recent years demonstrate that the three dimensional porous LiFePO4 combines both advantages of nano- and micro-sized active materials, which is the research hotspot and important development direction of LiFePO4 materials. In this review, we systematically summarize the reseach progress of porous LiFePO4 materials from the aspects of synthesis methods, morphologies and structure, electrochemical performances, and the relationship between structure and performance, and outlook the future developments of porous LiFePO4 materials.

Abstract:Diesel engines have been more and more widely used in heavy duty vehicles because of high efficiency and low fuel consumption compared with petrol engines. Taking ZrO₂ as the modified additive, the influence of the mass ratio of ZrO₂ and Al₂O₃ on catalytic performance was studied. The results show that, with an increase of ZrO₂ doping, the Pt particles becomes smaller at first and then larger in the catalyst. The interaction between Pt and the carrier increases and then decreases. Analysis of the activity data shows the optimized doping amount of ZrO₂ is 40 wt%, the CO/C₃H₆ complete oxidation temperatures reduced by 20 _oC and 25 _oC, respectively. The study shows that, when the ZrO₂/Al₂O₃ mass ratio in the carrier is varied, the precious metal dispersion on the catalyst and the precious metals interaction with the carrier are different with varying levels. The smaller the Pt particle size, the stronger the interaction between precious metal and the carrier, which indicates that the performance of catalyst is higher.