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Laser metal deposition (LMD) technology was used to fabricate single-track-multi-layers samples using Invar 36 alloy powder by two different deposition patterns: one-way laser scanning pattern and back and forth laser scanning pattern. The microstructure characteristics, grain morphology, formation mechanism and mechanical properties of the samples fabricated in two different deposition patterns were systematically investigated. It was shown that there was a thin layer of equiaxed grains in the top zone, an alternative arrayed grain morphology of columnar and cellular grains in the middle and periodic circular growth of small columnar grains at the bottom, which was generated by different temperature gradient in different location. The crystal orientation of columnar grains was distinct due to different deposition patterns. X-ray diffraction (XRD) and Energy Dispersive Spectrometer (EDS) showed that the deposited specimen was composed of austenite-single phase. Samples built by back and forth laser scanning pattern showed higher microhardness and tensile strength but lower elongation compared with samples built by one-way pattern, the horizontally built sample showed higher Ultimate tensile strength and yield strength but lower elongation compared with vertically built sample in the same laser scanning pattern. Laser metal deposited Invar 36 showed more excellent mechanical properties compared to the forged and casted counterparts.

Laser joining of carbon fiber reinforced polyether ether ketone (CFRP-PEEK) to titanium alloy (TC4) was performed. The influence of defocus distance, also described as irradiance diameter of laser beam on interfacial joining was investigated. The appearance of welded joint and the microstructure at joint interface was observed. The fracture load was thereafter obtained. In addition, temperature field simulation at the joint interface during laser joining process was carried out to clarify the joining mechanism. The results indicated that good appearances were obtained with low defocused distance. The interfacial observation showed that mechanical bonding was generated at the joint interface since the melted resin was embedded in the rough surface of the TC4. Besides, a new phase formed at the interface between CFRP-PEEK and TC4, which was identified as CTi0.42V1.58. The content of the phase increased as the defocus distance increased. Shear force decreased when the defocus distance increased from −4 mm (irradiance diameter 0.84 mm) to 0 mm (irradiance diameter 0.6 mm), and then increased when the defocus distance increased from 0 mm to +8 mm (irradiance diameter 1.06 mm). This phenomenon was explained by simulation result of temperature field that the width of the range of melting temperature of the resin increased as the laser beam diameter increased. The simulation results were consistent with the changes of the width of resin adhesion in actual joint.

High-entropy alloy Al0.85CoCrFeNi was joined to TiAl alloy through vacuum diffusion bonding. The typical interfacial microstructure of Al0.85CoCrFeNi/TiAl joint was TiAl/ α2-Ti3Al + solid solution strengthened γ-TiAl / FeNi, AlNiTi / Al(Co, Ni)2Ti /Cr(Fe, Co)ss / Al0.85CoCrFeNi. The formation of Al(Co, Ni)2Ti phase and Cr(Fe, Co)ss layer was result from the diffusion of Ni and Co atoms from Al0.85CoCrFeNi into TiAl substrate and the accumulation of Fe and Cr atoms at the Al0.85CoCrFeNi side. The effects of joining temperature and holding time on the microstructure and mechanical properties of joints were revealed. The joint with the maximum shear strength of ∼70 MPa was obtained at the joining temperature of 850 °C for 1.5 h under pressure of 30 MPa. The fracture path was deflected from solid strengthened γ-TiAl layer where FeNi, AlNiTi existed to Cr(Fe, Co)ss layer.

The effect of laser process parameters including single pulse energy (E), dimples per square millimetre (D) and laser incidence angle (θ) on the properties of 30CrMnSiA steel substrate and the tensile shear strength of adhesively bonded joints was investigated. The characterization of the substrate was established by surface morphology, the dimension (diameter and depth) of dimples and surface roughness (Ra and Rz). Single lap joints were fabricated and tensile tests were then performed. The fracture surfaces were observed and analyzed. The results indicated that the dimple dimension and surface roughness increased as the single pulse energy increased. The increase of dimples per square millimetre made surface roughness improve. The larger incidence angle reduced the actually absorbed energy changing the shape and size of dimples. The diameter of dimples increased while the depth decreased as incidence angle increased. The modified substrate morphology as well as increased dimple dimension expanded the contact area between the adhesive and adherend. The shear strength was enhanced and the maximum value was 24.67 MPa increasing by 363% compared to the adhesive joints without surface treatment. The mechanical interlocking between the adhesive and laser textured morphology was discovered in the fracture surface demonstrating the improvement of shear strength.

The isothermal wetting behavior of Sn–Ti alloys in contact with SiC were studied by the sessile drop method in the 900 °C–1000 °C temperature range, and the interfacial microstructures were characterized. Ti additions led the system to evolve from a non-wetting (θ = 151°) to a wetting state with the formation of interfacial layers (TiC and Ti5Si3). As the Ti concentration increased, more Ti5Si3 phases grew on the TiC layer and lower final contact angles were obtained. The lowest value θ = 20° was obtained at 1000 °C for the Sn-2.0Ti/SiC system. The Sn-5.0Ti melt kept the contact angle of 20° as well, whereas the formation of solid Sn–Ti intermetallics inhibited the kinetics of spreading. Lower temperatures had no influence on the final contact angles, only slowed down the spreading rate. The spreading of Sn–Ti melts on SiC consisted of three stages: (i) reaction-limited stage, (ii) transition stage and (iii) diffusion-limited stage. The activation energy of the first stage was calculated to be 210.3 kJ/mol. These results offer important information to optimize SiC brazing and for the preparing SiC-based composites.

Al4B2O9-whisker-coated Al2O3 ceramics were bonded by AgCu–4.5 wt.%Ti alloy in vacuum. The microstructure of the whisker-coated Al2O3 joints was investigated by scanning electron microscopy, transmission electron microscopy and X-ray diffraction. A continuous (Cu,Al)3Ti3O layer formed against the alloy at lower bonding temperatures, and a complex transition zone bordering the whiskers was observed, which consisted of Ag nanoparticles, titanium oxides, TiB2, (Cu,Al)3Ti3O nanoparticles and possible Ag3Al. As the bonding temperature increased, the Al2O3/AgCuTi interface was found to transform from whisker- to nanoparticle-strengthened composite region. Bend test results revealed that both the whiskers grown on Al2O3 and the dispersive nanoscale products in the alloy played positive roles in improving the joint properties. The maximum bend strength of the whisker-coated Al2O3 joints was 313 MPa at the bonding temperature of 820 °C.

A novel particle reinforced AgCu composite filler (abbreviated as AgCuC filler) was developed by introducing nano-Si3N4 particles and micron-Ti particles into AgCu powder filler. Reliable brazing of TC4 alloy to Si3N4 ceramic was achieved by using the AgCuC filler. The interfacial microstructure of TC4/AgCuC/Si3N4 brazed joint was TC4/Ti–Cu intermetallic layers/Ag based composite reinforced by fine particles/TiN + Ti5Si3 layer/Si3N4. The addition of nano-Si3N4 in AgCuC filler improved the interfacial microstructure by suppressing the growth of continuous Ti–Cu intermetallic layers adjacent to TC4 alloy and promoting the formation of Ag based composite reinforced by particle phases in brazing seam. The continuous Ti–Cu intermetallic layers thicken and the TiCu2 particle phases coarsened gradually with an increasing brazing temperature. Brazing defects including micro-cracks and nano-Si3N4 aggregation were generated at higher brazing temperature. The highest average shear strength of 73.9 MPa was achieved when brazed at 880 °C for 10 min, which was higher than that of joints brazed using AgCu filler alone (49.2 MPa).

High Nb containing TiAl alloy (Ti–45Al–8.5Nb–(W, B, Y) (at%)) was successfully brazed by using Ti–28Ni (wt%) eutectic brazing alloy. The interfacial microstructure was characterized by SEM, EDS and XRD. Especially the effect of brazing temperature on interfacial microstructure and joining properties was investigated in details. Microstructure analyses results showed that the brazed joints presented a symmetrical characteristic and mainly consisted of Ti3Al, Ti2Ni and B2 phases. As the brazing temperature increased, the amount of Ti2Ni phase gradually decreased, meanwhile the amount of B2 phase increased significantly, while the continuous Ti3Al layer was insensitive to the brazing temperature. The maximum shear strength reached 204 MPa when the joints were brazed at 1100 °C for 10 min. Brittle fractures were observed in all of the brazed joints after shear test although the fracture location changed obviously with the increase of brazing temperature.

In this paper, a spectral diagnosis method was reported to explore the temperature characteristic of plasma and detect the forming quality in laser additive manufacturing. The spectral data were collected by the spectrum acquisition system under different processing parameters. The plasma temperatures under different processing conditions were calculated using Boltzmann plot of six neutral iron lines between 375 nm and 390 nm, and the influence relationships between laser power, powder feeding rate, traverse speed, cladding layer and plasma temperature were found. Meanwhile, the time domain diagrams (the relationship between the temperature and time) corresponding to the process were established, in which temperatures were respectively calculated by Boltzmann double-line method and Boltzmann plot method, to analyze the correlation between temperature fluctuation and the forming defects. It was found that the results from Boltzmann plot method could reflect the generated defects more clearly.

In this paper, the growth behavior of Cu 6 Sn 5 intermetallic compound in Cu/Sn/Cu interconnection system during the ultrasonic-assisted transient liquid phase soldering were investigated under various ultrasonic bonding time. Asymmetrical growth of the interfacial Cu 6 Sn 5 was observed in the Cu/Sn/Cu solder joints, i.e., the Cu 6 Sn 5 near the side of cavitation erosion grew randomly, while the Cu 6 Sn 5 near the opposite side grew in layer type. The asymmetrical growth can be wholly ascribed to the asymmetrical ultrasonic effects across the entire Sn interlayer. The asymmetrical ultrasonic effects resulted in different conditions for the nucleation and growth behavior of Cu 6 Sn 5 on the upper and lower Cu/Sn interfaces. The microstructure and mechanical properties of the resulted full intermetallic joint were also investigated.

The Q345E lamellar tearing resistant steel with 140mm thickness was welded by submerged arc welding (SAW). The microstructure and properties of the welded joints were investigated. Affected by the long-term welding thermal cycle, microstructure at different thickness has great differences. The hardness in the weld center is higher about 55 HV than the base metal. Due to the grains refinement of the microstructure at 1/2 thickness was more obvious, the microhardness of this zone has a more obvious dispersion degree. The average grain size of ferrite at the 1/4 thickness is about 10 μm, which resulted in two samples at this thickness obtain a higher tensile strength (496.568 MPa and 496.36 MPa). Moreover, part of the pearlite lamellar in the HAZ at 1/4 thickness had been fragmented and spheroidized.

The composition of oxide film of Zr55Cu30Ni5Al10 bulk metallic glass was identified by X-ray photoelectron spectroscopy. In addition, the relatively sound joints of bulk metallic glass without macroscopic deformation were obtained by removing the oxide film before diffusion bonding. The joint interfaces were observed by scanning electron microscopy and atomic force microscopy. The hardness of joints near the interface was higher than that far away from the interface, which is attributed to the difference of structural relaxation. According to the result of micro-focused X-ray diffractometry and transmission electron microscopy, the joints retained the amorphous structure when the holding time is less than 20 min. The surface area fraction of oxide film on the interface of joints was detected by ultrasonic inspection. Moreover, the surface area fraction of oxide film is in excellent agreement with the theoretical value calculated by shear strength. The result indicated that surface oxide film is the dominant barrier on the diffusion bonding of bulk metallic glass rather than low atomic diffusion coefficient.

Diffusion bonding of TiAl alloys and Ti3SiC2 ceramics were carried out in a vacuum atmosphere. The microstructures and mechanical properties of the bonded joints were investigated. Results showed that three coherent intermetallic layers formed in the TiAl/Ti3SiC2 joints during bonding process. The compound layer adjacent to Ti3SiC2 substrate was indicated to be Ti5Si3, in which brittle fracture of the joints took place during shear strength test. The properties of diffusion bonded joints were greatly improved attributed to the formation of a good transition in the joint as well as the relief of the residual stress when using Ni foil as interlayer. Formation mechanisms of the compound layers during bonding process were discussed. Shear test results showed that the maximum shear strength reached 52.3 MPa. Corresponding fractograph indicated that the crack mainly propagated along Ti3SiC2 substrate adjacent to the bonding zone, accompanied with an intergranular and transgranular fracture mode.

TiAl intermetallics and Ti3AlC2 ceramics were jointed through diffusion bonding using Ti/Ni interlayer. The effect of bonding temperature and holding time on interfacial microstructure and mechanical properties of the bonded joints were investigated. The typical interfacial microstructure of the joint from TiAl to Ti3AlC2 side could be divided into τ3-Al3NiTi2, α2-Ti3Al, α-Ti + δ-Ti2Ni, δ-Ti2Ni, β2-TiNi, η-TiNi3, γ-(Ni)ss, γ′-Ni3(Al, Ti), γ′-Ni3(Al, Ti) + Ti3AlC2, respectively. The value of the microhardness in the reactive zones increased due to the formation of intermetallcs. Lower or higher bonding temperature and longer or shorter holding time both resulted in low strength owing to the insufficient diffusion of atoms or excessive formation of intermetallics. A high bonding strength can be obtained when bonding at 920 °C for 60 min. Fracture occurred through the intermetallic layer adjacent to the Ti3AlC2 substrate during shear test, showing brittle intergranular and transgranular characteristic.

Transient liquid phase bonding of Inconel718 superalloy was carried out using a commercial Ni–Cr–Si–B amorphous interlayer. The interfacial microstructure of Inconel718 joints was analyzed by a scanning electron microscope and a transmission electron microscope. In particular, the effects of post-weld heat treatment on the interfacial microstructure and joining properties of Inconel718 joints were investigated in detail. The results showed that the precipitation of second phases in joints induced by post-weld heat treatment were beneficial to the improvement of joint properties. A tensile strength of 1130 MPa with an elongation percentage of 7% was achieved for a sample bonded at 1050 °C/60 min+1180 °C/60 min followed by the post-weld heat treatment.

In this work, carbon fiber was introduced into the Ag-26.7Cu-4.5Ti (wt%) filler to optimize brazed joints by participating in brazing reaction process. The interfacial microstructure was analyzed by SEM and TEM, the effects of carbon fiber content on the microstructure and mechanical property of brazed joints were studied, the formation of brazing interface was systematically discussed, and the action mechanism of carbon fiber was illustrated. Experimental results demonstrated that carbon fiber reacted with Ti to generate TiC during the brazing process, and formed a structure of carbon fiber wrapped by TiC and Ti-Cu compounds (TiCu+Ti3Cu4). Due to competitive reaction between carbon fiber and Cu to Ti, the formation of bulk Ti3Cu4 and TiCu4 was inhibited, while the formation of Cu-based solid solution was promoted. The microstructure of joints was dispersed as the increase of carbon fiber. The maximum shear strength of 27.8 MPa was achieved when 0.3 wt% carbon fiber was added into AgCuTi filler. The reinforcing effects of carbon fiber were mainly to relieve the residual stress generated by CTE mismatch and reduce the thickness of brittle TiC layer close to C/C composite. However, excessive carbon fiber would deteriorate the joints because of the insufficient reaction between filler and C/C composite.

In this study, reliable Ti2AlNb/high-Nb-containing TiAl alloy (TAN) joints were achieved by diffusion bonding. The effects of bonding temperature and holding time on the interfacial microstructure and mechanical properties were fully investigated. The interfacial structure of joints bonded at various temperatures and holding times was characterized by scanning electron microscopy (SEM), energy dispersive spectrometer (EDS) and X-ray diffraction (XRD). The results show that the typical microstructure of the Ti2AlNb substrate/O phase/Al(Nb,Ti)2 + Ti3Al/Ti3Al/TAN substrate was obtained at 970 &deg, C for 60 min under a pressure of 5 MPa. The formation of the O phase was earlier than the Al(Nb,Ti)2 phase when bonding temperature was relatively low. When bonding temperature was high enough, the Al(Nb,Ti)2 phase appeared earlier than the O phase. With the increase of bonding temperature and holding time, the Al(Nb,Ti)2 phase decomposed gradually. As the same time, continuous O phase layers became discontinuous and the Ti3Al phase coarsened. The maximum bonding strength of 66.1 MPa was achieved at 970 &deg, C for 120 min.

Alumina was successfully joined to itself in air environment by B2O3 + Al2O3 powder mixture as the interlayer to synthesize aluminum borate whiskers in the joint. The microstructure evolution was analyzed by means of scanning electron microscope (SEM) and X-ray diffraction (XRD). The possible mechanism of microstructure evolution was also discussed. The effects of parameters such as heating cycles and temperature on the microstructure as well as the 3-point flexural strength of the joint were investigated. It was found that heating the specimen for several heating cycles instead of holding at a constant temperature for a long time can eliminate the voids among the whiskers to achieve a dense microstructure, and the phenomenon that higher temperatures can accelerate the reaction was also observed. The highest strength of the joint reaches 90.29MPa with the heating temperature of 800°C after four heating cycles.

Bonding of a single crystal Ni-based superalloy to a polycrystalline Ni-based superalloy was carried out through diffusion bonding and the microstructure and mechanical properties of the joint were investigated. A diffusion zone with a width of 35 μm was formed due to elements diffusion. From the single crystal substrate to the diffusion zone, the shape of γ′ phase changed from cuboidal to columnar. The hardness of the diffusion zone was a bit higher, which can be attributed to the precipitation of the fine γ′-strengthening phases. The average shear strength of 433 MPa was obtained and the fracture presented a plastic characteristic.

Contact reactive brazing of Ti53311S alloy was extensively evaluated using Cu foil as interlayer within the range of 940–1020 °C for 10 min. Effect of brazing temperature on the interfacial microstructure and its evolution as well as joining properties were investigated in detail. TiCu and Ti 3 Cu 4 intermetallic compounds formed in joint by isothermal solidification and peritectic reaction (TiCu + L → Ti 3 Cu 4 ) when the brazing temperature was 940 °C. A eutectoid microstructure consisting of α-Ti and Ti 2 Cu phases was produced by the eutectoid reaction (β-Ti → α-Ti + Ti 2 Cu) in joint when brazed at 960–1000 °C. Whereas when brazing was conducted at 1020 °C (above the α → β transus temperature 1010 °C), Lamellar(α + β) structure was obtained in joint by isothermal solidification and subsequent phase transformation. Tensile test indicated that the maximum average tensile strength reached 932.6 MPa at room temperature. Brittle fractures were observed in all of the brazed specimens although the fracture mode was different.

A mathematical model was established to estimate the contributions of different mechanisms to the diffusion bonding of Zr-based bulk metallic glass to crystalline aluminum alloy. Additionally, the fraction of contact area with oxide film ϕ was introduced into the model since oxide film is the main barrier to atomic bonding across interface at lower temperature. The model calculation displayed that the plastic deformation of Al alloy dominated the void formation stage, while the homogeneous plastic flow of BMG played a major role in the void shrinkage stage. The joints bonded by two different methods were used to verify the model. The experimental strength of joints achieved by pre-friction assisted diffusion bonding and Ar ion assisted diffusion bonding had a sound fit with the theoretical strength curves of ϕ = 28% and 22.5%, respectively.

1 keV low energy argon ion beam was used to irradiate the surface of Zr 55 Cu 30 Ni 5 Al 10 bulk metallic glass. Bulk metallic glass specimens irradiated for different times were used to join with Aluminum alloy by argon ion activated diffusion bonding. Compared with the joints using the as-cast bulk metallic glass, the tensile strength of the joints using irradiated specimens had a drastic improvement. Moreover, a crystalline layer was obtained in the BMG side of the joint interface using irradiated specimens. The improved joint quality was attributed to the local heating resulting from a crystallization behavior of irradiated surface layer which increases the probability of jumping the barrier to form the atom bonds, as well as the significant enhancement of the atomic diffusivity after crystallization.

A new joining method, pre-friction diffusion hybrid bonding, was proposed to achieve a BMG/BMG joint without macroscopic deformation. This method employed the pre-friction process to break the oxide film of BMG specimens. The average shear strength of joints bonded by this method was 194.38 MPa, which is much higher than the conventional diffusion bonding. No observable crystallization was detected by MF-XRD and TEM. This novel joining method provided a feasible route for the high-quality solid-state bonding of materials with surface oxide film.

The composite fillers have a number of advantages comparing with the traditional filler metals, and have been widely used for brazing ceramics. However, previous researches mainly focus on the strengthening mechanism of either whiskers or particles. It is still of great interest to investigate the reinforcement effect with the presence of both whiskers and particles. In this study, Ag-Cu-Ti + B4C composite filler was developed to braze SiC ceramics, and effects of holding time on the microstructure evolution and mechanical properties of the joints were investigated in detail. With the prolongation of holding time, the overall thickness of Ti3SiC2 + Ti5Si3 layers adjacent to SiC ceramic was increased correspondingly and the reaction between active Ti and B4C particles was promoted more extensively. The bending strength of the joints increased with holding time until the maximum bending strength of 140 MPa was reached and then decreased dramatically. The hardness and Young's modulus of the joints were characterized by nano-indentation to reveal the strengthening of the brazing seam. In addition, the strengthening mechanism of the joints brazed by the Ag-Cu-Ti + B4C composite filler was proposed on the basis of experimental observation and theoretical analysis.

a b s t r a c t A novel TiNi-V25 (at.%) eutectic brazing alloy, which was composed of TiNi intermetallics and V, was designed and fabricated. Subsequently, the brazing alloy was used to braze TiAl intermetallics (Ti-42.5Al-9V-0.3Y (at.%)) and reliable joints were obtained. The typical interfacial microstructure of TiAl brazed joints was characterized by employing SEM, EDS and XRD, and the brazing mechanism was ana- lyzed in detail. The brazed joints mainly consisted of B2 phase and 3-Al3NiTi2 intermetallics. Interfacial morphology of TiAl joints varied with the increase of brazing temperature, while the phase constitu- tion in joints did not change sound TiAl joints with the highest average shear strength of 196 MPa were obtained when the specimens were brazed at 1220 ◦C for 10 min. The presence of B2 phase and 3- Al3NiTi2 intermetallics in joints deteriorated the joining properties due to their brittleness, which led to cleavage-dominated fracture after shear test. The crack propagation path and fracture location were mainly determined by the content and distribution of 3-Al3NiTi2 phase. © 2012 Elsevier B.V. All rights reserved.

The Al/Ni multilayers were characterized and diffusion bonding of TiAl intermetallics to TiC cermets was carried out using the multilayers. The microstructure of Al/Ni multilayers and TiAl/TiC cermet joint was investigated. The layered structures consisting of a Ni3(AlTi) layer, a Ni2AlTi layer, a (Ni,Al,Ti) layer and a Ni diffusion layer were observed from the interlayer to the TiAl substrate. Only one AlNi3 layer formed at the multilayer/TiC cermet interface. The reaction behaviour of Al/Ni multilayers was characterized by means of differential scanning calorimeter (DSC) and X-ray diffraction. The initial exothermic peak of the DSC curve was formed due to the formation of Al3Ni and Al3Ni2 phases. The reaction sequence of the Al/Ni multilayers was Al3Ni → Al3Ni2 → AlNi → AlNi3 and the final products were AlNi and AlNi3 phases. The shear strength of the joint was tested and the experimental results suggested that the application of Al/Ni multilayers improved the joining quality.

Brazing titanium aluminide to silicon nitride was realized by using inactive AgCu filler metal. The effect of the brazing temperature on the interfacial microstructure and joining strength was investigated. The typical interfacial microstructure of the joint was TiAl/B2 phase/AlCuTi/AlCu2Ti/Ag(s,s) + AlCu2Ti/TiN + Ti5Si3/Si3N4. With an increase of the brazing temperature, the distribution of granular AlCu2Ti intermetallics at the center obviously changed and the thickness of TiN + Ti5Si3 layer adjacent to silicon nitride substrate increased simultaneously. The highest shear strength of 124.6 MPa was achieved with 1133 K brazing temperature and 5 min holding time. In addition, the nucleation of tiny Al3V intermetallics for the precipitation of AlCu2Ti phase was found, which was confirmed beneficial for improving the joining properties.

Since the existence of the ionosphere contamination, results of high-frequency radar has been greatly affected. This paper addresses a new method based on temporal correlation matrix to correct phase distortion for HF sky-wave radars. Strong point echoes, such as target, clutter, transponder and so on, which are highly temporal correlated, can be used to structure temporal correlation matrix. And the matrix contains angles of echoes and phase distortions information. In this paper, we use two-dimension FFT to estimate angle of strong point echo, and then obtain the corrections. Computer simulations are conducted to show the validity of the new method, and some of performances of PGA were compared.

A novel composite filler alloy was developed by introducing Si 3 N 4p (p = particles) into Ag–Cu–Ti filler alloy. The brazing of Si 3 N 4 ceramics and TiAl intermetallics was carried out using this composite filler alloy. The typical interfacial microstructure of brazed joints was: TiAl/AlCu 2 Ti reaction layer/Ag (s,s) + Al 4 Cu 9 + Ti 5 Si 3p + TiN p /TiN + Ti 5 Si 3 reaction layer/Si 3 N 4 . Effects of Si 3 N 4p content in composite filler alloy on the interfacial microstructure and joining properties were investigated. The distribution of Ti 5 Si 3p and TiN p compounds in Ag-based solid solution led to the decrease of the mismatch of the coefficient of thermal expansion (CTE) and the Young's modulus between Si 3 N 4 and TiAl substrate. The maximum shear strength of 115 MPa was obtained when 3 wt.% Si 3 N 4p was added in the composite filler alloy. The fracture analysis showed that the addition of Si 3 N 4p could improve the mechanical properties of the joint.

The function of the hepatitis E virus (HEV) open reading frame 3 (ORF3) protein product remains unclear but it is able to induce a strong antibody response following HEV infection. Therefore, it has been used in some enzyme immunoassays (EIAs) for detecting anti-HEV antibody. In order to evaluate the difference in antigenicity of HEV ORF3 polypeptides derived from genotypes 1 and 4, two EIAs were developed, based on ORF3 polypeptides from genotypes 1 and 4 HEV. Serial weekly serum samples from two rhesus monkeys vaccinated with ORF3 antigens derived from the genotype 4 ORF3 protein and nine rhesus monkeys experimentally infected with genotypes 1 and 4 HEV were tested for anti-HEV using the assays. HEV ORF3 antigens derived from viruses of genotypes 1 and 4 showed different patterns of reactivity with sera obtained from monkeys immunized with ORF3 antigens or infected experimentally with HEV. The genotype 1 ORF3 polypeptide exhibited stronger reactivity with the sera from monkeys infected with genotype 1 than the genotype 4 ORF3 polypeptide. The genotype 4 ORF3 polypeptide demonstrated stronger reactivity with the sera from monkeys infected with genotype 4 than did the genotype 1 ORF3 polypeptide. The HEV ORF3 polypeptide contains genotype-specific antigens and the antigen-antibody reactions between the same genotypes were stronger than those between different genotypes. J. Med. Virol. 83: 827-832, 2011. (C) 2011 Wiley-Liss, Inc.

The hepatitis C virus core protein plays an extremely important role in the hepatocarcinogenesis of hepatitis C virus. Little, however, is known about the oncogenic potency of fragments. Thus, the purpose of the present study is to investigate the cancerogenic effects of the different core protein fragments. Two series of recombinant plasmids containing hepatitis C virus core gene fragments encoding the different-length core protein were constructed using plasmid enhanced green fluorescent protein (pEGFP)-C1 and pcDNA3.1(+), respectively. Human hepatocyte L02 cells transiently transfected with pEGFP-C1-based plasmids were subjected to confocal laser scanning microscopy analysis to determine the localization of the different core protein fragments. The stably transfected L02 cells with the pcDNA3.1(+)-based core protein plasmids were used to investigate the ultrastructural effects of the core protein and the tumorigenicity of L02 cells expressing core protein fragments in athymic nude mice. The full-length core protein and Core130-191 were completely localized in the cytoplasm, while Core1-59 existed exclusively in the nucleus. On the other hand, Core50-140 and Core1-140 were observed in both the nucleus and the cytoplasm. Ultrastructural changes of L02 cells expressing the full-length core protein were comprehensive and included, for example, irregular nuclear, increased nuclear/cytoplasmic ratio and mitochondria swelling. The slight changes were observed in the cells expressing Core50-140 and Core130-191, whereas the ultrastructure of the cells expressing Core1-59 remained normal. All the L02 cells stably expressing different fragments of the core protein, with the exception of the C-terminal truncated fragment Core1-59, could induce the occurrence of tumor in the nude mice. The N-terminal fragment of the core protein, Core1-59, was not oncogenic, while the intermediate and posterior segments of the hepatitis C virus core protein had the cancerogenic potency. In view of the existence of many important immunogenic epitopes in it, the core protein anterior segment might be a safer candidate for the development of hepatitis C virus vaccine.

A joint of Zr 55 Cu 30 Ni 5 Al 10 bulk metallic glass to crystalline material (Al-5Fe alloy) was achieved successfully by the pre-friction assisted diffusion bonding. This method employed the pre-friction process to break the oxide film of bulk metallic glass specimens. The average tensile strength was 58.42 MPa, which is much higher than CDB. The bulk metallic glass workpieces after joining retained the unique amorphous structure, indicating that thermal cycle, microscopic deformation and interface atomic diffusion caused no micro-structural transformation of amorphous state. The pre-friction assisted diffusion bonding mechanism was proposed, which showed that the pre-friction process played a role of breaking the oxide film and providing a favorable diffusion bonding condition.

Three kinds of test welding wires were developed, and the effect of the proposed welding wires on the microstructure and properties of the T92 deposited materials were studied. The results showed that: the welding wires should be preheated with the temperature range 200–250 °C to prevent the crack occurring; By PWHT, the second phase precipitated at grain boundary and sub-grain boundary as well as inside grain. The precipitation at grain boundary and sub-grain boundary was mainly Cr 23 C 6 phase, and the precipitation inside grain was the diffuse point-like MX phase; When Ni content was greater than 1%, the point AC 1 decreased to be lower than the PWHT temperature. The austenite transformation happened in the tempering heat preservation process at a temperature above AC 1 , then, austenite changed into untempered martensite in the cooling stage, leading to the ununiformity of tempered structure and deteriorated properties as well as the reduction of toughness. As the impact toughness increased, the fraction of radial region and shear lips region reduced while fiber region enlarged. The shear fracture surface ratio for the proposed three deposited metals were 83%, 87% and 86%, respectively, and the fiber regions mainly consisted of the typical dimples.

Welding and joining of titanium aluminides is the key to making them more attractive in industrial fields. The purpose of this review is to provide a comprehensive overview of recent progress in welding and joining of titanium aluminides, as well as to introduce current research and application. The possible methods available for titanium aluminides involve brazing, diffusion bonding, fusion welding, friction welding and reactive joining. Of the numerous methods, solid-state diffusion bonding and vacuum brazing have been most heavily investigated for producing reliable joints. The current state of understanding and development of every welding and joining method for titanium aluminides is addressed respectively. The focus is on the fundamental understanding of microstructure characteristics and processing–microstructure–property relationships in the welding and joining of titanium aluminides to themselves and to other materials.

Summary Objectives The detection of Mycobacterium tuberculosis specific antibodies in human sera has been a rapid and important diagnostic aid for tuberculosis (TB) control and prevention. However, any single antigen is not enough to be used to cover the antibody profiles of all TB patients. Methods Seven single antigens (38 kDa, ESAT-6, CFP10, Mtb8.4, MPT64, TB16.3 and Mtb8) were evaluated serodiagnostically. Two novel M. tuberculosis polyproteins, 38kD-ESAT6-CFP10 (38F) and Mtb8.4-MPT64-TB16.3-Mtb8 (64F), were expressed and the novel 38F–64F indirect ELISA assay used to analyze antibody responses to polyproteins in serum samples. Results The sensitivity of the novel 38F–64F indirect ELISA alone was much higher than that of the sputum culture test (86.91% vs. 50.62%) and that of the sputum smear test (78.64% vs. 47.57%). The novel 38F–64F indirect ELISA had a sensitivity of 74.16% with sera from extrapulmonary TB patients and a sensitivity of 37.14% with sera from LTBI. The specificity of the novel 38F–64F indirect ELISA was 90.36% with the sera from healthy blood donors and 94.15% with the sera from non-TB patients. Conclusions The novel 38F–64F indirect ELISA assay had effective diagnostic performance and would make meaningful contribution to the diagnosis of TB disease in developing countries.

This paper focuses on calibration of uniform linear array (ULA) for high frequency surface wave radar. A novel algorithm is proposed based on spatial correlation properties of the calibration source. We can estimate amplitude from the main diagonal elements of spatial correlation matrix, and obtain DOA (direction of arrival) estimate of the calibration source by two-dimension FFT. The spatial correlation matrix could be estimated in temporal domain and frequency domain, which performs better in low SNR case. It is shown through Monte Carlo simulations and experimental results that this method is practical and reliable.

A 12.4-kDa peptide, corresponding to the entire ORF3 protein of hepatitis E virus (HEV), derived from human HEV genotype 4 and expressed in Escherichia coli as a fusion protein with a 17.5-kDa fragment of interleukin (IL)-1beta at the N-terminus, was recognized by HEV-reactive sera. Eight monkeys were immunized with the purified peptide, and seven were used as non-immunized controls. All 15 monkeys were challenged with HEV genotype 1 or 4. All control animals developed infection and hepatitis, and all but one vaccinated monkey became infected. Nevertheless, the vaccine was effective in reducing the virus titer and shortening the duration of viremia and fecal shedding. Furthermore, the vaccine provided some protection against hepatitis (1 of 2 monkeys in the two-dose regimen and 4 of 6 in the three-dose regimen did not develop severe hepatitis) compared to the controls. These results suggest that immunization with the bacterially expressed peptide may partially prevent experimental hepatitis, and even infection, in primates, following intravenous challenge with high doses of two HEV genotypes.

Following infection with hepatitis E virus (HEV), anti-HEV immunoglobulin (Ig) M is thought to develop before anti-HEV IgG and to be a better marker for differentiating between the acute and convalescent phases of infection. In order to select polypeptides for improved detection of anti-HEV IgM, six and three overlapping polypeptides from open reading frames (ORFs) 2 and 3, respectively, of HEV genotypes 1 and 4 were expressed as fusion proteins in Escherichia coli. The reactivities of the polypeptides with anti-HEV IgM were evaluated using immunoblotting and enzyme immunoassays (EIAs). The data indicated that polypeptides from the N-terminus of ORF3 and middle region of ORF2 were weakly or not reactive with anti-HEV IgM, while those from the remaining regions of ORF2 and ORF3 contained reactive epitopes. Anti-HEV IgM against the N- or C-terminus of ORF2 appeared earlier and disappeared faster than that against polypeptides from the C-terminus of ORF3, based on serum samples from rhesus monkeys infected experimentally, and from patients infected naturally, with HEV. The N- and C-terminal polypeptides from ORF2 complemented one another in detecting anti-HEV IgM and EIA sensitivity was improved significantly with a combination of these polypeptides. The reactivities of ORF2 polypeptides from genotypes 1 and 4 were similar but that of ORF3 differed with sera from monkeys infected by the two genotypes. Thus, a combination of N- and C-terminal polypeptides of ORF2 from one genotype may be effective in EIAs to detect anti-HEV IgM.

CPNE5 is one of the ubiquitous Ca2+-dependent, phospholipid-binding proteins that are highly conserved in animals. It was cloned in the fetal human brain with no exact functions identified yet. We have examined the distribution pattern of CPNE5 mRNA and protein in the developing murine brain by using in situ hybridization, western blotting and immunocytochemistry. Expression of CPNE5 mRNA remains high from embryonic day 9.5 (E9.5) to E15.5 in the developing murine brain. Whole-mount in situ hybridization with the E11.5 and E12.5 embryos showed the strong positive signals in the central nervous system. Western-blot analysis showed that CPNE5 protein is expressed in the developing but not in the adult murine brain. In situ hybridization and immunohistochemistry analysis on the embryonic brain sections indicated that both at RNA and protein levels CPNE5 is mainly expressed in frontal cortex, medial nasal prominence, ganglionic eminence and medulla, particularly in the ventricular zones. Further investigation revealed the co-localization of CPNE5 with Tuj1 and Nestin on embryonic brain sections. In addition to the slight expression in primary cultured neural progenitor cells, CPNE5 is found in soma and neurite projections of primary cultured neurons where Tuj1 is co-localized. Our results demonstrate that CPNE5 is expressed in both neural progenitor cells and the differentiated neurons during the neural development, which suggests that CPNE5 might play an important role in the development of murine central nervous system.

The growth of nickel borate [Ni3(BO3)2] nanowhiskers was successfully achieved by simply heating a mixture of nickel and boron oxide (B2O3) powders at 950 °C in air. The products were characterized using X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The synthesized nanowhiskers, with diameters of 150–500 nm and lengths of 10–30 μm, possessed high aspect ratio, and were found to grow along the [012] crystallographic direction. Stacking faults, hollow interiors, and high-energy facets were found occasionally. The high-temperature stability of Ni3(BO3)2 nanowhiskers was investigated. The nanowhiskers partially decomposed after being treated at 1200 °C. Based on the solid–liquid–solid mechanism, the possible growth process of Ni3(BO3)2 nanowhiskers was discussed. Ni3(BO3)2 nanowhiskers were successfully used for bonding nickel in air. The nickel/nanowhisker/nickel joint was characterized in detail by scanning electron microscopy and laser scanning confocal microscopy.

A chimera HIV-1/HIV-2 envelope sequence composed of multiple conserved immunodominant epitopes of HIV-1 envelope protein (HIV-1 IIIB: env482-518 + env548-675) and the HIV-2 gp36 immunodominant epitope (env592-603), was constructed and directly over-expressed in E. coli by using a prokaryotic translation initiation sequence contained within the gene of HIV-1 envelope. The recombinant product was purified and applied in antibody-screening assay. The purified chimera antigen reacted with all the thirty-eight HIV-1 positive serum samples, the two HIV-2 serum samples, and had no cross-reaction with all the eighty-eight normal healthy serum sample. The results indicated that this recombinant chimera HIV-1/HIV-2 envelope protein could be useful for diagnostic purposes of HIV infection.

Background The present study was aimed to evaluate whether IgG, IgM and IgA antibodies levels detected against a novel Mycobacterium tuberculosis polyprotein 38F-64F (with 38F being the abbreviation for 38kD-ESAT6-CFP10 and 64F for Mtb8.4-MPT64-TB16.3-Mtb8) are suitable for diagnosing active tuberculosis, and for monitoring the efficacy of chemotherapy on TB patients. Methods In this study, a total of 371 active TB patients without treatment were selected and categorized into S+/C+ group (n = 143), S-/C+ group (n = 106) or S-/C- group (n = 122). A series of serum samples were collected from 82 active TB patients who had undergone anti-TB chemotherapy for 0–6 months at one month interval. Humoral responses (IgG, IgM and IgA) were determined for the novel Mycobacterium tuberculosis polyprotein using indirect ELISA methods in all of serum samples. Results For S+/C+, S-/C+ and S-/C- active tuberculosis patients before anti-TB chemotherapy, the sensitivities of tests based on IgG were 65.7%, 46.2% and 52.5% respectively; the sensitivities based on IgM were 21.7%, 24.5% and 18.9%; and the sensitivities based on IgA were 25.2%, 17.9% and 23.8%. By combination of three isotypes, for all active tuberculosis patients, the test sensitivity increased to 70.4% with the specificity being 91.5%. After anti-TB chemotherapy, there were no significant differences between groups with different courses of anti-TB chemotherapy. Conclusions The novel Mycobacterium tuberculosis polyprotein 38F-64F represents potential antigen suitable for measuring IgG, IgM and IgA antibodies. However, the serodiagnostic test based on the 38F-64F polyprotein appears unsuitable for monitoring the efficacy of chemotherapy.