bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of Sr Addition on as Cast Microstructure of AS31 Alloy
Authors: Zhou Ji Xue , Yang Yuan Sheng , Tang Shou Qiu , Tian Chang Wen
Published: June 2011

The effect of Sr addition on the as-cast microstructure of AS31 alloy was studied. The experimental results show that the grain size decreased obviously from 1116μm to 221μm for AS31 alloy with addition of 0.05%Sr, and promote the formation of globular grains. The morphology of eutectic Mg2Si phase is changed from Chinese script to polyhedral shape or fine fibers shape. The grain refinement mechanism is attributed to the enrichment of Sr element at solidification interface front, which restricts the growth of α-Mg primary dendrite. The modification of the eutectic Mg2Si phases results from the dissociative Sr changing the preferred growth manner of them.
Effects of Ultrasound on the Microstructures and Mechanical Properties of Cast-Rolling AZ31B Magnesium Alloy Strip
Authors: Li Jian Ping , Hu Jian Bing , Mao Da Heng , Zhao Guan Zhong
Published: June 2011

The experiment of ultrasonic cast-rolling magnesium strip was carried out on the horizontal twin-roll cast-rolling machine with the ultrasonic pole used in the solidification. The microstructures of ultrasonic and general cast-rolling magnesium strip were characterized. The results showed that the cellular dendrite of the general cast-rolling magnesium strip was coarse, the grain structure was heterogeneous and the average grain diameter was between 50μm~60μm. However, the grain structure became more homogenize after the ultrasonic treatment for cast-rolling magnesium strip, the grain was refined and the average grain diameter was between 20μm~30μm. Besides, the mechanical properties test results show that the tensile strength, yield strength and elongation of the ultrasonic cast-rolling magnesium strip were increased by 22.85%, 49.78% and 123.06% than those of the general cast-rolling magnesium strip.
Evaluation on Vibration Property of Magnesium Honeycomb Panels
Authors: Quan Gao Feng , Liu Zhao Ming , Gu Xiue
Published: June 2011

The vibration and acoustic transmitting experiments and digital simulation were carried out on AZ31 magnesium sheet and magnesium honeycomb panels. The results show that the vibration characteristics and acoustic transmission loss (TL) of honeycomb panel are related to magnesium sheet and honeycomb core parameters. In full audible frequency spectra, TL of various honeycomb panels behaves in a similar manner, and the TL increases with the frequency at higher frequency. Damping enhancements of honeycomb panels contribute better vibration insulation. Vibration analysis shows that the dangerous positions are located in no-strutting areas.
Grain Reﬁnement of Magnesium Alloy AZ31 by Repeated Cold Rolling and Annealing
Authors: Chen Xing Pin , Xiao Rui , Sun Can , Lin Zhen Xia , Liu Qing
Published: June 2011

This work focused on the grain reﬁnement and investigation its effect on the microstructural evolution and mechanical properties. The magnesium alloy AZ31 sheet was processed by repeated cold rolling and recrystallized annealing. From the experimental works, the ﬁne and equiaxed grains with less than 5 μm were achieved. It was found that for annealing at temperatures in the range of 523–673K, sample was fully recrystallized less than 30 minutes and after that the growth of the recrystallized grains is slight. Finally, the tensile tests were carried out to analyze the changes in the strength and fracture elongation.
High Strain Rate Compression Behavior and Constitutive Relation of As-Extruded Mg-Gd-Y Magnesium Alloy
Authors: Liu Zheng , Mao Ping Li , Wang Chang Yi
Published: June 2011

The high strain rate compression behavior of extruded Mg-Gd-Y magnesium alloy was tested by split Hopkinson pressure bar (SHPB) under the strain rates of 465s-1，2140s-1 and 3767s-1. As comparison the quasi-static compression behavior was tested in the meanwhile. The results show that the quasi-static yield stress is equivalent to that of high strain rates, but the flow stress at high strain rates are higher than that of quasi-static stain rate at the same strain. When the strain rate is increase from quasi-static to high strain rates the deformation stresses increase obviously but within the present testing high strain rates, increasing the strain rate the stress has a slight increasing, indicating that at high strain rate the stress of Mg-Gd-Y magnesium alloy is not sensitive to the strain rate. The constitutive equation between deformation stress, strain and strain rate was build based on the tested compression stress strain curves. The calculated stress strain data were compared with tested stress strain curves. The results demonstrate that when the strain rates are 0.001s-1，465s-1，2140s-1 respectively the calculated and experimental data are fit very well. The calculated stress is higher than that of tested stress if the strain rate is increase to 3767s-1 and the strain is more than 0.15. The discrepancy was explained through the physical soundness of Johnson-Cook model.
High Temperature Deformation Behaviour and Processing Maps of AZ81 Magnesium Alloy
Authors: Liao Hui Min , Zeng Ming , Long Si Yuan , Cao Han Xue
Published: June 2011

The hot compression deformation behavior of AZ81 magnesium alloy was studied with Gleeble-1500 thermal simulation machine at the strain rate of 0.003 ~ 3.0s-1 and temperature of 340 ~ 430 °C. The results show that, the flow stress decreases when the deformation temperature increases and strain rate decreases; the peak stress increases with decrease of the temperature and the increase of the strain rate; the critical strain that comes into stable phase increases obviously. It is that the high temperature flow stress model of AZ81 magnesium alloy is constructed by introduceing Zener-Hollomon parameters, its average deformation activation energy is 169.48 kJ / mol. Processing maps of AZ81 magnesium alloy is also calculated and analyzed by the dynamic model of the material. Useing hot deformation processing maps, the flow instability zone is determined and the best process parameters access to the test parameters during hot deformation are as follow: thermal processing temperature range of 380 °C ~ 420 °C, strain rate range of 0.01 ~ 0.03 S-1.
Interpretation of Crystallographic Morphologies of Precipitates in Mg Alloys with a Secondary CCSL Model
Authors: Shi Zhang Zhi , Zhang Wen Zheng
Published: June 2011

This work presents a secondary CCSL model to interpret newly observed orientation relationships of fcc Mg2Sn precipitates and bcc Mg32(Al, Zn)49 precipitates with respect to Mg matrix. The morphologies of these precipitates are characterized with a common feature of well defined facets. The orientations of these facets have been interpreted with the secondary CCSL model.
Mechanical Properties and Microstructure of AZ31 Magnesium Alloy under Uni-Axial Tensile Loading
Authors: Zhong Xiao Yu , Huang Guang Jie , He Fang Fang , Liu Qing
Published: June 2011

Uni-axial tensile plastic deformation behavior of rolled magnesium alloy AZ31B under the temperature range from room temperature(RT) to 250°C with strain rates between 10-3 and 10-1s-1 has been systematically investigated. Microstructure evolution and texture were determined using optical microscopy (OM) and electron back-scattered diffraction (EBSD) techniques, respectively. Our results indicated that the strength and elongation-to-fracture were more sensitive to strain rates at elevated temperature rather than that at room temperature; dynamic recrystallization (DRX) and relaxation of stress at elevated temperature resulted in dramatic change of mechanical properties. Compared with strain rate, the temperature played a more important role in ductility of AZ31B Mg alloy sheet.
Ultimate Strength and Plasticity of Magnesium Alloy under Different Temperatures and Strain Rates
Authors: Chen Bin , Yin Da Gang , Yuan Quan , Luo Ji , Zhang Ding Fei , Quan Guo Zheng
Published: June 2011

A series of tensile tests of AZ61 magnesium alloy were conducted using Gleeble-1500 thermal-mechanical material testing system to learn the effect of the test temperatures and strain rates on the mechanical properties of the alloy. It is indicated that the higher the temperature, the lower the ultimate strength and fracture stress, and the larger the plasticity. It is also revealed that the larger the strain rate is, the higher the ultimate strength of the specimens will be, and the larger the plasticity of the specimens will be. The failure mechanism of the material under high temperature was also analyzed based on the fracture observation. It shows that the high temperatures will induce microvoids or microflaws in the material.
Microstructure and Mechanical Properties of Quasicrystal Reinforced Magnesium Matrix Composites
Authors: Wang Xu Dong , Du Wen Bo , Wang Zhao Hui , Li Shu Bo
Published: June 2011

Magnesium-based composites reinforced with stable icosahedral quasicrystal particles have been fabricated via Repeated Plastic Working (RPW) process. The microstructure of the composites has been investigated by XRD, SEM, TEM and HREM, and its mechanical properties have also been studied. The results showed that the RPW process could reduce the matrix grain size significantly, and the average grain size of matrix was only about 500 nm after 200 cycles of RPW. A good metallurgical bond interface between the quasicrystal particles and the Mg matrix was found. The composites exhibited the maximum yield strength of 265MPa and the maximum ultimate tensile strength of 309MPa at room temperature, respectively. The enhancement of mechanical properties is attributed to the strengthening effect of the quasicrystal particles and the fine-grain size of matrix.
Effect of Nd Addition on a Mg-Zn-Bi Magnesium Alloy
Authors: Zhao Hao Feng , Wang Ling , Zhang Yong , Zhang Lu , Yi Liang
Published: June 2011

The effect of the 1-4wt% Nd addition on the microstructure , hardness and anticorrosion performance of Mg-Zn-Bi alloy was studied . The experimental results showed that both the hardness anticorrosion performance of the Mg-Zn-Bi magnesium alloy increased with increase of the Nd addition.
Research on Corrosion Resistance of AZ91D Magnesium Alloy Coated with Epoxy Resin
Authors: Li Yong Gang , Wei Ying Hui , Hou Li Feng , Tian Yun , Yang Lijing
Published: June 2011

The corrosion resistance of a 1~2mm thick AZ91D magnesium alloy die-casting coated with epoxy varnish after phosphatizing was tested. Zinc phosphating solution was used. In the experiment, uniform paint was obtained by dipping method. Scratch test showed that the adhesion force between the coating and matrix is excellent. Within the test range the optimal phosphating temperature and time are 50°C and 1 min tested by dynamic potential scanning method. With the organic coating the corrosion current density decreased 3 orders of magnitude, the polarization resistance increased 3 orders of magnitude. The coated specimens were immersed in10% H2SO4, 10% NaOH and acetone for 10 days, respectively. The results showed that blistering did not occur on the paint films. This work illustrated that the simple zinc phosphating process combined with simple organic coating can meet the corrosion resistance requirements of thin-wall die casting magnesium components that require higher quality appearance.
Thermodynamics of In Situ Formation of Mg2Si and MgO in AZ91D /Flyash Composites
Authors: Yu Si Rong , Huang Zhi Qiu , Liu Jia An
Published: June 2011

Novel AZ91D Mg alloy/fly-ash cenospheres (AZ91D/FAC) composites were fabricated by melt stir technique. The thermodynamic analyses of the interfacial reactions, the microstructure observation, and the phase analyses of the AZ91D/FAC composites were investigated. The results showed that the cenospheres were almost filled with Mg alloy matrix. In-situ MgO and Mg2Si phases were formed in Mg alloy matrix and near the interfaces between the cenospheres and Mg alloy matrix. Through the thermodynamic calculation, it can be found that the standard free enthalpy changes of these interfacial reactions are all negative at the temperature of Mg alloy melt preparation in this work, and these reactions can occur.
Effect of Clock Rolling on Microstructures and Properties of AZ31 Magnesium Alloy Sheets
Authors: Huang Xin , Huang Guang Jie , Xiao Dong Ping , Liu Qing
Published: June 2011

In this paper, the influence of clock rolling（CR）on microstructure and texture as well as the anisotropic properties of AZ31 alloy sheet was systematically studied. Compared to unidirectional rolling（UR）, clock rolling leads to more uniform microstructure in annealed sample. The average grain sizes of the two kinds of sheet are similar. Texture measurement reveals that clock rolling can effectively weaken the intensity of basal texture and generate more symmetrical basal texture. Clock rolled samples exhibit weaker anisotropy of mechanical properties due to its lower basal texture intensities and more symmetrical basal texture in tensile test.
Fabrication of Alumina Composite Ceramics with High Addition of Carbon Nanotubes
Authors: Bi Song , Su Xun Jia , Hou Gen Liang , Guo Feng , Xiao Zhou
Published: June 2011

Carbon nanotubes-alumina (CNTs-Al2O3) composite ceramics with 25vol% CNTs were fabricated by sol-gel method and followed by hot-pressing. The resultant ceramics and powders were characterized for their microstructure and composition by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and infrared spectra (IR). The mechanical properties of the ceramics were measured by micromechanical testing system (MTS). The results show that both ultrasonic calefaction process during the gelation of alumina sol and annealing process during the sintering can remarkably enhance the fracture toughness and flexural strength of CNTs-Al2O3 composite ceramics, compared with the composite ceramics without undergoing these processes. It is believed to be due to the relatively uniform dispersion of CNTs and the lower thermal stress in the matrices.
The Thickness and the Inerior Quality of Composite Panel in the Vacuum Assisted Resin Transfer Molding Process
Authors: Li Yan Liang , Yi Xiao Su , Tang Bang Ming
Published: June 2011

The objective of this paper was focused on predicting the thickness and the interior quality of carbon fiber composite panel during the vacuum assisted resin transfer molding (VARTM) process. The character of the VARTM process determined that it was low cost. A panel made of Epoxy resin, and carbon fibers, was used as the simplest article to experiment and except routine items, the thickness and the interior quality was focused. In the process, the flow front of the resin was record using a digital camera. Darcy’s law was the model of resin flow. The results showed that the flow front history would reach unanimous, thickness near the edges was difficult to control, and most of the porosity came from the injection line where more resin cumulated.
Well-Crystallized SnO2 Nanocrystals Homogeneously and Intimately Coated on Multiwalled Carbon Nanotubes by a Simple Surfactant-Free Hydrothermal Method
Authors: Guo Y.Q. , Tan Rui Qin , Cao Z.Y. , Song Wei Jie
Published: June 2011

A simple approach to the in situ deposition of well-crystallized SnO2 nanocrystals on the surface of multiwalled carbon nanotubes (MWCNTs) in the ethanol solution system of SnCl2 was presented in this paper. The well-crystallized SnO2 nanocrystals with small and uniform crystal size (4~5 nm) can be tightly and homogenously coated on the outside surface of the MWCNTs entirely. The prepared nanocomposites were characterized by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, and nitrogen BET measurements. It is found that the hydrothermal reaction plays an important role for the crystal growth of the SnO2 nanocrystals on the surface of MWCNTs, and the crystallinity of the SnO2 nanocrystals can be controlled by varying the pH value or the hydrothermal reaction time. It is found that a unique structure of leaf-like SnO2 nanosheets hanging on the MWCNTs was obtained when using water as the solvent of SnCl2 instead of ethanol. The gas sensing performance of the SnO2/MWCNTs nanocomposites was also investigated.
Influence of Carbon Fiber Pre-Treatments on Interlaminar Shear Strength and Fracture Behavior of C/C Composites
Authors: Sun Wan Chang , Li He Jun , Fu Qian-Gang , Zhang Shou Yang
Published: June 2011

PAN-carbon fibers were pretreated using three methods. 2D-C/C composites were fabricated by a rapid chemical liquid-vaporized infiltration (CLVI) processing. Surface morphologies of carbon fiber pretreated and fracture micrographs of 2D-C/C composites were observed by scanning electron microscopy (SEM) and high resolution transmission electron microscope (HRTEM). The interlaminar shear strength(ILSS) of C/C composites was tested. The influences of carbon fiber surface pretreatments on ILSS and fracture behaviors of C/C composites were analyzed. The experimental results indicated that the C/C composite with carbon fiber coated CVI pyrocarbon possesses both higher flexural strength and interlaminar shear strength than composites with other fiber pretreatments. The fractographes revealed the differences in the mechanical behavior depending on the interface strength of fiber/matrix.
Preparation and Properties of Electromagnetic Absorbing of Hollow Ceramic Microspheres
Authors: Wang Jian Jiang , Lou Hong Fei , Shi Dong Mei , Hu Wen Bin
Published: June 2011

The preparation, mechanism and electromagnetic absorbing properties of Hollow Ceramic Micro-spheres (HCMs) were studied in the present investigation. HCMs were produced by traditional flame spraying technology as well as equipments. Al-TiO2 was chosen as a main reactive system. The self-reactive agglomerate powders were produced by spraying process by adopting a temperature-controlled media to get the high cooling rate to solidify and crystallize rapidly. HCMs with characteristic of hollow structure and in-situ synthesis were obtained. Electromagnetic parameter of HCMs has been tested and the reflectivity was analyzed. The results showed that HCMs possess the microwave absorbing properties. The relationship between intrinsic parameters of HCMs and microwave absorbing properties has been also investigated.
Effect of the Content of LaNd on Physical Properties and Solderability of Zn20Sn6Cu Solder
Authors: Zhao Kuai Le , Yan Yan Fu , Li Yong Bing
Published: June 2011

Zn20Sn6Cu solder with the melting point of 382°C has good mechanical properties and low cost. Therefore it is considered as an ideal high-temperature lead-free solder. However, its physical properties and spreading properties are poor. In this paper a new solder was made by adding trace LaNd into Zn20Sn6Cu alloy to improve the performance. The effect of the content of LaNd on physical properties and weld ability of Zn20Sn6Cu solder was investigated. The experimental results showed that the effect of the content of LaNd on the melting point of Zn20Sn6Cu solder was not obvious and the liquid-solid temperature range of the Zn20Sn6Cu solder increased with the increasing of the content of LaNd (less than 0.5 wt.%). When RE content was 0.1 wt.%, the liquid-solid temperature range of Zn20Sn6Cu0.1RE was only 13.3°C. The resistivity of the novel solders increased with the increasing of the content of LaNd. When LaNd is higher than 0.3 wt%, the resistivity of the novel solder sharply increased. The spreading performance of the new solder alloy was improved obviously by adding trace LaNd into Zn20Sn6Cu solder. When the content of LaNd was 0.1 wt%, the spreading area of Zn20Sn6Cu0.1LaNd solder reached to the maximum value of 32.5% bigger than that of the matrix solder, which mainly related to the formation of the new CuZn5 and Cu5Zn8 phases as well as the intermetallic compounds between the solder and the substrate. Therefore, considering the physical properties and spreading properties of the novel solders, the best content of LaNd is about 0.1 wt.%.
A Study on Linseed Oil Modified Waterborne Polyurethane Coatings
Authors: Chen Jian Bing , Guo Qiang , Sun Jin Liang , Shao Xian Li , Nie Zhi Jun
Published: June 2011

The waterborne polyurethane coatings modified by linseed oil were prepared in a method of ammonolysis. The influence of reaction time and temperature of the linseed oil ammonolysis on structure and properties of the waterborne polyurethane coatings was investigated and discussed. It has been shown in this work that the preferred ammonolysis temperature would be 102~118°C, the reaction time could be about 80 min, and structure of the modified waterborne polyurethane was analysed by FTIR. The touch-dry time of the modified waterborne polyurethane with drier would be shorter than that of non-modified waterborne polyurethane, normally in a week, and the stability of the modified waterborne polyurethane coating in water could stand for 3 months under room temperature. The TGA results of the coatings showed that the weight loss started at about 294°C.
Effect of Cryogenic Treatment on the Microstructure and Mechanical Properties of AZ31 Magnesium Alloy
Authors: Li Jie , Jiang Xianquan
Published: June 2011

The microstructure and mechanical properties of AZ31 magnesium alloys were investigated in this paper. AZ31 magnesium alloys were cryogenically treated at -196°C for 1, 5 and 24 hours, respectively. The results showed the grains of AZ31 were initially refined and grew up with the increase of cryogenic time, the second phase decreased gradually, and the rigidity and tensile strength decreased drastically and then increased. As a result, AZ31 magnesium alloys with 1 hour cryogenic treatment were able to obtain the optimal combination properties.
Failure of the EB-PVD TBCs of Rare Earth Zirconates
Authors: Xu Zhen Hua , He Li Min , Lu Feng , Mu Ren De
Published: June 2011

Thermal barrier coatings (TBCs) have very important applications in gas turbines for higher thermal efficiency and protection of components at high temperature. TBCs of rare earth materials such as lanthanum zirconate (La2Zr2O7, LZ), lanthanum yttrium zirconate (3wt% Y2O3- La2Zr2O7, 3YLZ), lanthanum cerium zirconate (La2(Zr0.7Ce0.3)2O7, LZ7C3) were prepared by electron beam-physical vapor deposition (EB-PVD). The compositions, crystal structures, thermal expansion behaviors, cross-sectional morphologies and cyclic oxidation behaviors of these coatings were studied. These coatings have partially deviated from their original compositions due to the different evaporation rates of oxides, and the deviation could be reduced by properly controlling the deposition condition. The thermal expansion behavior of LZ coating can be largely improved after doping with 3wt% Y2O3 and CeO2. The excess La2O3, chemical incompatibilities of the ceramic coatings with thermally grown oxide (TGO) layers, the visible cracks initiation, propagation and extension, the abnormal oxidation of bond coat, and the thermal expansion mismatch between ceramic coatings and bond coat are the primary factors for the spallation of LZ, 3YLZ and LZ7C3 coatings.
Microstructure Features of Cold-Sprayed NiCoCrAlTaY Coating and its High Temperature Oxidation Behavior
Authors: Li Chang Jiu , Li Yong , Xing Lu Kuo , Yang Guan Jun , Li Cheng Xin
Published: June 2011

Superalloy coating was deposited by cold-spraying using a commercial NiCoCrAlTaY powder. The coating microstructure was investigated by scanning electron microscopy and X-ray diffraction to reveal the change of the b-NiAl phase in the as-received powder particle during coating deposition. The oxidation behavior of the cold-sprayed MCrAlY coating and its microstructural evolution during the isothermal treatment were examined. The results show that significant microstructural change occurred to NiCoCrAlTaY superalloy during cold spraying and the thermal exposure. The intensive plastic deformation upon high velocity impact of spray particles results in transformation of b-NiAl to the matrix phase, forming metaltable b-NiAl depletion zones (b-PDZs) which are distributed around the boundaries of deposited particles in the coating. The central part of the deposited particles with limited deformation retained the original phase constitutions of the starting powder. The b-phase with fine grains is re-precipitated uniformly in the areas in b-PDZs in the as-sprayed coating during high temperature exposure. A stable Al2O3 scale was formed on cold-sprayed NiCoCrAlTaY during oxidation possibly due to active b-PDZs on the top surface of the coating.
Research on Cavitation and Silt Erosion Resistance of HVAF Coatings
Authors: Liu Juan , Pan Luo Ping , Yu Jiang Cheng
Published: June 2011

Two kinds of harding coatings: WC-12Co and CrC-25NiCr were made by active combustion-high velocity air flue (AC-HVAF). By the rotating disc test rig, the systematical experiments were carried to study the wear resistance and mechanisms of coatings on different test conditions: pure water cavitation and sandy water silt erosion. On the sandy water silt erosion test condition, the wear resistance of HVAF coatings is better than that of metal matrix. However, it is reverse on the other test condition. Basing on the scanning electron microscope (SEM) analysis, the surface morphology of coating surface after wear was studied. And the influence of adhesion strength, micro-hardness and porosity ratio of HVAF coating on wear resistance was researched in detail.
Effect of Heating Rates and Loading Rates on Mechanical Behaviors of Magnesium Alloy
Authors: Chen Bin , Luo Ji , Yuan Quan , Zhang Ding Fei , Quan Guo Zheng
Published: June 2011

The mechanical response and failure of the specimens of magnesium alloy AZ61 with different heating rates (HR) and loading rates (LR) were investigated by a Gleeble-1500 thermal-mechanical material testing system. It was found that heating rate has markedly effect on the strength and plasticity of the specimens. The higher the heating rate is, the lower the strength and the smaller of the plasticity of the specimens will be. There is the relatively small effect of the loading rates on the strength and plasticity of the specimens. The metallographs of the failed specimens were also observed. It shows that there are many microvoids in the specimens near the fracture sections. These microvoids may come from the local thermal and stress inconsistency under high heating rate and loading rates and degrade the strength and plasticity of the specimens.
Study on Microstructure of Laser In Situ Formation of TiBX and TiC Titanium Composite Coatings
Authors: Liang Jing , Chen Sui Yuan , LIU C.S. , Liu Feng Hua
Published: June 2011

Two kinds of mixed powders:Ti-6Al-4V/B/C and Ti-6Al-4V/B4C which are pre-pasted or synchronized fed on Ti-6Al-4V substrates separately were scanned by a 500W pulsed YAG laser to induce in situ formation of titanium composite coatings contained TiBx and TiC ceramic reinforced phases. The influences of laser processing parameters including Pulse Frequency (PF), Pulse Width (PW), Laser Power (P) and Scanning Speed (V) together with the powder proportions on the microstructure and properties of the coatings were investigated. Microstructures, phase components of the coating were analyzed by OM, SEM, TEM and XRD respectively. Experimental results show that two and more kinds of ceramic reinforcements were in situ formatted in the matrix of Ti-6Al-4V. TiB and TiC ceramics were formed evenly with the morphology of needle, tiny dendrites and disperse particles in the prepasted single path specimens. For the powder feed laser cladding layers, the ceramic reinforcements were TiB (needlelike), TiB2 (hexagonal prism or rodlike), a small amount of TiC (disperse particles) and non fully reacted B4C. The microhardness increased with the increase of the amount of B4C and B+C additions. When the added B and C contents are the same, the microhardness of the coating with B4C addition is higher than that of the coating with B+C addition. The average micro-hardness of a powder prepasted (with 20 wt.% B4C addition) multi-path laser cladding layer formed under the optimized processing parameters is up to 800HV, which is more than 2 times of that of the substrate (340Hv), and the wear weight loss of the layer decreased nearly 3 times that of the substrate.
Surface Modification by HVOF Coating of Micron-Sized WC-Metal Powder and Laser-Heating of the Coating
Authors: Cho Tong Yul , Yoon Jae Hong , Hur Sung Kang , Chun Hui Gon , Zhang Shi Hong
Published: June 2011

μWC-metal powder (powder) was coated onto the surface of Inconel 718 (IN718) using HVOF spraying for the improvement of surface properties. The coating was heat-treated by CO2(g) laser for further improvement of the properties. Optimal coating process was obtained from surface properties of 9 coatings prepared by Taguchi program. Surface property improvement by HVOF coating and laser-heating were investigated. The surface hardness of IN718 was increased by coating from 399 Hv to 1260±30 Hv, and further increased to 1860±100 Hv by laser-heating. Porosity of the coating was decreased by laser-heating from 2.2±0.3% to 0.4±0.1%. The friction coefficient of the surface was decreased by the coating from 0.48±0.06 to 0.33±0.02 at room temperature. Friction coefficients of IN718 and the coating were decreased with increasing sliding surface temperatures from 25°C to 450°C. According to reciprocating sliding wear tests, wear depth and trace of the coating were smaller than IN718 at both 25°C and 450°C. The coating had better wear resistance compared to IN718, creating smaller wear traces. At 450°C, wear depth of coating was much smaller than IN718: 50-µm-deep groove compared to 75 µm for IN718.
Synthesis of (Ni, Co)Fe2O4-Spinel Coating Using High Temperature Oxidation Treatment of Ni-Co-Fe2O3 Composite Electrodeposited Coating
Authors: Ma Li , Zhou Ke Chao , Li Zhi You , Zhang Lei
Published: June 2011

Ni-Co-Fe2O3 composite coatings are successfully developed via conventional electrodeposition technology. The effects of electrodeposition parameters on the content of Fe2O3 particles in the composite coating and, of surfactants on the texture coefficient of the composite coating were investigated. It is found that electrodeposition parameters play an important role in controlling the composition, the grain size and the preferred orientation of the composite coatings. Composite coatings with high content of Fe2O3 particles and high (100) texture were obtained. A (Ni, Co)Fe2O4-spinel coating was obtained by the oxidation treatment of as-plated Ni-Co-Fe2O3 composite coatings with high content of Fe2O3 particles performed in air at 1000°C for 6h.
The Investigation of the Zirconium Silicate Coatings Prepared by APS
Authors: Liu Yan Bo , Wang Quan Sheng , Ma Zhuang , Du Zhong , Liu Juan
Published: June 2011

The zirconium silicate can be deposited as functional coatings which will be used at high temperature because of its high melting point and low thermal conductivity. It can also prevent the oxygen of the environment through the coatings and react with the substrate. In this paper, plasma spraying technology was selected to prepare the coatings of zirconium silicate. The orthogonal design method was used to optimize the parameter of plasma spraying process. The content of zirconium silicate in the coatings was checked by XRD because of the decomposition of the zirconium silicate at 1711K.The bond strength and porosity of the coatings were also measured after the optimizing of the plasma spraying parameters in this paper. According the impact on the porosity, the factors of the process can be ordered as follows: spraying distance, current, primary gases and secondary gases. And the order of spraying factors according the impact on the content of zirconium silicate in the coatings was showed as follows: spraying distance, secondary gas, primary gas and current.
Tribological Properties of Laser Surface Texturing and Coating Duplex-Treated Surface
Authors: Jiang Jie , Xiong Dang Sheng , Li Jian Liang , Shi Yan
Published: June 2011

Components of space machines often works at high temperature and vacuum, or on other rigour conditions, the traditional liquid lubricant cannot satisfy the requirement. The common solid lubricant is hard to supply between two friction surfaces continuously and it is easily decomposed and failure at high temperature. It is an urgent need to study a new type of lubrication technology. In this paper, the surface of 1Cr18Ni9Ti with high hardness and micro dimples was prepared through laser texturing and plasma molybdenizing/plasma nitriding duplex treatment. The textured surface was coated with MoS2 lubricating film and the friction and wear properties from room temperature to high temperature were evaluated. The results show that the laser surface textured dimples trap hard abrasive particles and reduce the damage to the lubricating film, and thus decrease the wear rate. The optimum dimple density of 7.1% is obtained. At elevated temperature, the wear rate of molybdenized texture or nitrided texture is lower than that of the matrix and single textured surface.
Improvement of the Electrochemical Properties of LiMn2O4  by Doping Rare Earth Element Ce
Authors: Zhang Hai Lang , Ren Ren , An Jing
Published: June 2011

A series of cathode materials for Li-ion battery, spinel LiMn2-xCexO4 (x=0-0.03), were synthesized by the method of solid-state reaction at high temperature. The XRD data showed that all the synthesis samples were pure spinel phase. The results of charge-discharge tests show that LiMn1.98Ce0.02O4 has the highest discharge specific capacity of 119.6 mAh/g, and the discharge specific capacity of the material was 108.5 mAh/g after 50 cycles at room temperature with a retention of 91.0%, and the coulombic coefficient was still high up to 99.8%.
Characterizations of UV Aging and Atmospheric Corrosion on Epoxy Coated 7A04 Aluminum Alloy
Authors: Dong Chaofang , Xiao Kui , Sheng Hai , An Y.H. , Li Xiao Gang
Published: June 2011

The aim of this work is to investigate characterizations of corrosion on 7A04 aluminum alloy with epoxy coating under simulated marine atmosphere with/without ultraviolet irradiation. The environment containing Cl- and sunlight illumination was simulated by salt spray test and UV irradiation/condensation treatment. The corrosion behavior was studied by electrochemical impedance spectroscopy, and level of coating damage was evaluated through gloss measurement. Scanning electron microscope was chosen to observe surface properties of epoxy coating/7A04 aluminum alloy system. The results show that the electrochemical characters are closely related to the aging degree of epoxy coating, which could influence the penetrating process of oxygen and corrosive medium. The coating resistance decrease, while the coating capacitance and the pore rate increase as prolonging of the test time. Along with gloss loss of epoxy coating, pores appear on the surface and the blisters break, which may act as bulk defects of epoxy coating. The coating degradation and substrate corrosion were accelerated by the cooperation of UV irradiation and salt spray. UV aging significant accelerated the deterioration of coating with larger and deeper pores compared to that of non-UV irradiation coating.
Effect of 1% Ce Addition on Microstructures and Mechanical Properties of As-Cast Mg-3.8Zn-2.2Ca (wt.%) Magnesium Alloy
Authors: Yang Ming Bo , Qin Cai Yuan , Zhu Yi , Cheng Liang
Published: June 2011

In this paper, the effect of adding 1.0 wt.% Ce on the as-cast microstructure and mechanical properties of the Mg-3.8Zn-2.2Ca (wt.%) magnesium alloy were investigated. The results indicate that, after adding 1.0 wt.%Ce to the Mg-3.8Zn-2.2Ca alloy, small amounts of Mg12Ce phase are formed and an obvious equiaxed trendance is observed. At the same time, the average grain size decreases from 234mm to 71mm and the morphology of some Ca2Mg6Zn3 phases changes from initial coarse blocks to fine particles. In addition, adding 1.0 wt.%Ce to the Mg-3.8Zn-2.2Ca alloy also improve the tensile and creep properties of the alloy. Further investigations need to be considered in order to optimize the amounts of Ce additions and understand its effects on the tensile and creep properties and age-hardening behaviour.
Effect of Sr on Microstructure and Mechanical Properties of Mg-9Li-3Al Alloy
Authors: Yang Yan , Peng Xiao Dong , Xie Wei Dong , Wei Qun Yi , Chen Gang , Su Zhong Hua
Published: June 2011

Mg-9Li-3Al-xSr alloys were prepared in vacuum furnace under the protection of argon atmosphere. Effects of Sr content on microstructure and mechanical properties of as-cast Mg-9Li-3Al alloys were investigated. The results indicate that α-Mg and β-Li phases exist in all alloys. The addition of Sr causes grain refinement of the test alloys and new Al4Sr phase is formed in the alloys. The mechanical properties of alloys initially increase and then decrease with the increase of Sr content. Sr has obvious refining effect on the alloys and the distribution of Al4Sr phase is much more uniformly when Sr content is 2.5wt%,. The as-cast Mg-9Li-3Al-2.5Sr alloy exhibits an optimum combination of mechanical properties with the ultimate strength, yield strength and elongation of 186MPa, 149MPa and 11% respectively, improving obviously compared with Mg-9Li-3Al alloy. With the continuing increase of Sr content, the mechanical properties of the test alloys decrease.
Effect of Zn/Er Ratio on Microstructures and Mechanical Properties of the Cast Mg-Zn-Er Alloys
Authors: Li Shu Bo , Li Han , Li Jian Hui , Du Wen Bo , Wang Zhao Hui
Published: June 2011

The microstructures and mechanical properties of the Mg-Zn-Er alloys have been investigated. The results show that the alloying elements (Zn/Er) with different ratio have a great effect on the microstructure and mechanical properties of the magnesium alloys, especially for the phase constitutes. Furthermore, the more attractive result is that the quasicrystalline phase, as the main secondary phase, precipitates during solidification in the alloy with addition of Zn/Er ration of 6. The cast Mg-5Zn-0.83Er alloy exhibits the ultimate tensile strength and yield tensile strength are 190MPa and 80MPa at room temperature, respectively, with an elongation of 15%.
Interfacial Microstructures and Kinetics of Sn2.5Ag0.7Cu/Cu
Authors: Wang Yao Li , Zhang Ke Ke , Li Chen Yang , Han Li Juan , Zhang Qing Zhi
Published: June 2011

The interfacial microstructures and kinetics of low Ag content Sn2.5Ag0.7Cu/Cu solder joint were investigated by the X-ray diffraction, scanning electronic microscope and energy spectrum analysis during the isothermal aging. The results show that the interfacial microstructures of the Sn2.5Ag0.7Cu/Cu solder joint are composed of Cu3Sn and Cu6Sn5after soldering. With the aging time increasing, the intermetallic compound (IMC) pattern of the solder joint interface can be changed from the scallop-like to the shape-layer, and the growing dynamics is coincidence with the law of parabola and its growing behavior is controlled by diffusion. The growing activation energies values of Cu3Sn and Cu6Sn5layer at the Sn2.5Ag0.7Cu/Cu solder joint are 82.4kJ/mol and 69.6kJ/mol respectively.
Comparison of Wettability for Sn-Based Solders on Copper and Aluminum Substrates
Authors: Yin Li Meng , Xian Jian Wei , Yao Zong Xiang
Published: June 2011

The wetting properties of four typical Sn-based solders, i.e., Sn-37Pb, Sn-3.0Ag-0.5Cu, Sn-0.7Cu and Sn-9Zn, on copper (Cu) and aluminum (Al) substrates at 250 °C, 260 °C and 270 °C were evaluated and compared by wetting balance method. The experimental results show that the wetting time of all solders on Cu substrate is shorter than that on Al substrate, but the wetting force of the solders with Cu substrate is bigger than that with Al substrate except Sn-9Zn solder. In addition, the wettability of the solders on Al substrate increases with increasing soldering temperature, and the wetting force of Sn-9Zn increases most obviously among four solders and reach 3.68 mN at 270 °C. The results also show that the wettability of the solders on Cu substrate mainly depends on surface tension of solder alloy, however, it depends on both surface tension and interaction with Al on Al substrate. Due to the active element Zn riches on the surface of Sn-9Zn solder, and Zn solid solutes into Al more easily, the wettability of Sn-9Zn solder on Al substrate is better than other three solders.
Synthesis and Application of Electronic Transporting Materials
Authors: Li Ting Xi , Gao Su Su , Sui Peng , Kong Na , Wu Sha Sha , Li Shan Ting
Published: June 2011

Novel pyridine-containing compounds were synthesized and their properties were studied. Organic EL devices using these compounds as electron-transporting layer were fabricated. It is demonstrated that these compounds are useful for organic light-emitting diodes (OLED) and solid state lighting technology in favor of energy-saving and environmental protection fields.
Synthesis and Properties of Diphenylquinoxaline as Electron-Transporting Materials
Authors: Li Ting Xi , Sui Peng , Gao Su Su , Kong Na , Wu Sha Sha , Li Shan Ting , Niu Zhan Rui
Published: June 2011

Bis-(2,3-diphenylquinoxaline) (DDPQL) has been synthesized by condensation reaction with 3,3'-diaminobenzidine and benzil. The thermal and electrical properties of DDPQL were measured as well. Organic electroluminescent device using DDPQL as electron-transporting layer was fabricated. The structure of the organic electroluminescent device is ITO/α-NPD/ Alq/DDPQL/LiF/Al. The maximum brightness of the electroluminescent device at voltage of 13.5V is 12,100cd/m², the maximum current efficiency at voltage of 13.0V is 4.97cd/A, the external quantum efficiency is 1.92%, and the lowest drive-voltage is 3.5V. This indicates that the compounds are useful as electron-transporting materials in organic electroluminescent devices.
Synthesis of Bi2O3- B2O3- SiO2- ZnO Glass and their Effects on the Sintering Temperature and Magnetoelectric Properties of Co / Ti Doped M-Type Barium Ferrite
Authors: Zhong Wen Guo , Liu Ying Li , Li Yuan Xun , Chen Da Ming , Yang Kai
Published: June 2011

The 25%Bi2O3-30%B2O3-10%SiO2-35%ZnO (molar ratio, abbreviated as BBSZ) glass were successfully prepared by solid-phase method. The amount of BBSZ glass varied from 1wt% to 5 wt% was optimized and its effects on the sintering behavior, structure and magnetoelectric properties of the Co / Ti doped M-type barium ferrite were investigated by HP 4291B vector analysis, scanning electron microscopy (SEM) and VSM magnetometer respectively. The testing results show that the ferrite could be well sintered at 900°C with excellent performances when the 3wt% BBSZ is added. The initiative permeability and cut-off frequency are 13.5 and 800MHz, respectiveley, which suggests that this material is a candidate for application in the fabrication of chip inductors by the technology of low temperature cofired ceramics and ferrites (LTCC).
The Effect of Sb Content on Spark Plasma Sintered High-Density Antimony-Doped Tin Oxide Ceramics
Authors: Li Qi Zhong , Zhang Dong Ming , Luo Guo Qiang , Li Cheng Zhang , Shen Qiang , Zhang Lian Meng
Published: June 2011

Spark plasma sintering (SPS) is a newly developed technique that enables poorly sinterable tin oxide powder to be fully densified. Sintering without sintering aids is of great importance when SnO2ceramics are used as electrodes in the glass melting industry and aluminum electrometallurgy. Dense and good-conductive Antimony-doped SnO2 ceramics can be achieved by SPS at a lower sintering temperature and in a shorter time. When the Sb2O3concentration is 1.0 mol%, the densities of the samples reach their maximum value, which is 98.2% of the theoretical value. When the content of Sb2O3was 2.44mol%, SnO2ceramics with densities 97.6% can be obtained at 800°C-1000°C, and the resistivity was about 5.19×10-2Ω.cm at the sintering temperature of 1000°C. Defined amount of Sb3+used in our research are beneficial to low the sintering temperature and promote the densification of SnO2ceramics
Thermal Analysis of High Power Light Emitting Diodes Package
Authors: Han Yuan Yuan , Guo Hong , Zhang Xi Min , Yin Fa Zhang , Chu Ke , Yao Ou Yang
Published: June 2011

With increasing of the input power of the chips in light emitting diode (LED)， the thermal accumulation of LEDs package increases. Therefore solving the heat issue has become a precondition of high power LED application. In this paper, finite element method was used to analyze the thermal field of high power LEDs. The effect of the heatsink structure on the junction temperature was also investigated. The results show that the temperature of the chip is 95.8°C which is the highest, and it meets the requirement. The conductivity of each component affects the thermal resistance. Convective heat exchange is connected with the heat dissipation area. In the original structure of LEDs package the heat convected through the substrate is the highest, accounting for 92.58%. Three heatsinks with fin structure are designed to decrease the junction temperature of the LEDs package.
Dielectric Properties of Low Permittivity BST-Mg2TiO4 Composite Ceramics
Authors: Liu Cheng , Lu Xiao Gang , Gao Chang Jie , Jing Hui Xia , Cheng Lin , Liu Peng
Published: June 2011

100(1-y)wt%Ba0.50Sr0.50TiO3—100ywt%Mg2TiO4(BST-MT,y=0.76, 0.8, 0.82, marked as S1, S2, S3) composite ceramics with low permittivity (ε<60) were prepared by a traditional solid reaction method. The microstructure and dielectric properties of BST-MT composite ceramics were investigated. With the content of MT increasing, the dielectric peaks of BST-MT were depressed and broadened, thus the thermal stability was improved. However, the tunability declined withyincreasing. In order to offset the temperature sensitivity, we obtained an Electrical field-Temperature (E-T) relationship by changing the dc bias field within a wide temperature range so that we could keep the tunability at a fixed value (3%). Such result explored a new route to compensate the temperature sensitivity of BST system in designing tunable microwave devices
Effect of P on the Anti-Oxidation of SnPb Solder and the Mechanism Research
Authors: Yao Ou Yang , Hu Qiang , Zhang Fu Wen , Wang Zhi Gang
Published: June 2011

The effects of phosphorous on the anti-oxidation of SnPb solder and the mechanism were investigated. The surface oxidation behavior of Sn63Pb37 solder in the liquid state was observed by comparing the color of the molten solder and the effects of the temperature on the oxidation resistance of solder Sn63Pb37-P is conduced by skimming and weighting the oxidation dross. OM, SEM and EDS were used to analyze the anti-oxidation performance and mechanism. The results show that Sn63Pb37 solder with 0.019wt.% P can maintain smooth and brightly longer under 260°C, and produce less oxide slag. It is found that phosphorous is needle-like and concentrate on the surface of the solder and oxide film. At 260 °C, the additional element P suppresses impurity element Fe forming oxide. The additional element P will engage in the forming of oxide film, and improve the structure and mechanical property of oxide film to achieve the antioxidant effect. If heated to 380°C, the oxidation resistance of molten Sn63Pb37-P alloy was greatly worsen, instead.
Electrode Size Effect on the Resonance Spectrum of PZT Piezoceramic Resonator
Authors: Wu Long , Chure Ming Cheng , Chen Bing Huei , Chen Ping Cheng , Chen Yeong Chin
Published: June 2011

The resonance spectrums of disc type piezoceramic resonators with different electrode sizes were measured in the frequency range from 100 kHz to 1 MHz. Besides the fundamental mode, some overtone and other vibration modes existed in this frequency range, depending on the electrode size. The series resonance frequency of fundamental modes of the resonators increased with the reduction of the electrode size. When the electrode size was decreased down to 80% of size, some small spurious signals will exist; these spurious signals may be caused by another vibration mode such as twist mode or bending mode. The planar electromechanical coupling factor increased first with the decreasing of the electrode size, and reached a maximum when the diameter of electrode was decreased down to 80% of size, and then decreased with the decreasing of the electrode size.