bluuebunny/crossref_metadata_2025 huggingface dataset:
Mechanical Properties and Mechanism of Graphite Oxide Reinforced Oil Well Cement
Authors: Li Ming , Meng Fei , Guo Xiao Yang
Published: March 2016

The effect of graphite oxide (GO) on the mechanical properties of oil well cement was experimentally studied, in view of the zonal isolation failure due to the brittleness. The microstructure of cement stone was observed by SEM, and the mechanism of graphite oxide reinforced cement stone was also investigated. The result illustrates that the mechanical properties of cement was improved significantly due to the addition of GO. When the GO dosage was 0.05%, the compressive strength, flexural toughness, and splitting tensile strength of cement paste at 7 day age were increased by 61.32%, 15.46% and 145.34% respectively. GO had no bad effect on the application properties of cement slurry, and the stability of the slurry was favorable. Besides, GO could reduce the fluid loss of cement slurry. When GO reinforced cement stone undergoes damage under complex stress, if damage occurs within graphite oxide layer, chemical bonds of GO layers must have been broken, and the force between the layers of GO must be overcome when interlaminar peeling happens, which will lead large amounts of energy consumption as well. The mechanical properties of the cement stone were enhanced by the above two aspects. The research results can provide a theoretical reference for solving the brittle fracture of oil well cement stone.
Effect of Na2SO4 on the Performance of Mg-Air Battery
Authors: Zhao Yan Chun , Huang Guang Sheng , Liu Ding Kai , Han Ting Zhuang , Pan Fu Sheng
Published: March 2016

In this study, an Mg-air battery based on air cathode with different content of Na2SO4 was prepared to study the effect of Na2SO4 on the performance of Mg-air battery. The electrochemical performance of the air cathode was studied by potentiodynamic polarization and electrochemical impedance spectroscopy. The results indicated that the electrochemical activity of the electrode enhanced with the increasing Na2SO4. The discharge performance of the battery was investigated by constant-current discharge test, and the results showed that the discharge potential of the battery also improved with the increasing of Na2SO4. However, the forming of air cathode became difficult gradually with the increasing content of Na2SO4. What is worse, the oversize pore produced in the moisture barrier when the content of Na2SO4 was too high and the moisture barrier would lose resistance to water. So the content of Na2SO4 should not be too high.
Synthesis of MDI-50 and Tung Oil-Based Non-Ionic Waterborne Polyurethanes
Authors: Ren Bai Xia , Wang Hua Fen , Ren Zhi Yong , Liu Wen Tao , Jiang Lei , He Su Qin
Published: March 2016

A series of MDI-50 based non-ionic waterborne polyurethane dispersions (MDI-NPUD) were prepared by the mixing of 2,4’-diphenylmethane diisocianate (2,4’-MDI) and 4,4’-MDI (MDI-50) which reacted with hydroxylated tung oil (HTO) and polyethylene glycol-800 (PEG-800), Fourier Transform Infrared Spectroscopy (FTIR) and Proton-Nuclear Magnetic Resonance (1H-NMR) were used to characterize and analyze their molecular structures. The results indicated that MDI-50 and HTO were introduced as hard segment while PEG acted as soft segment. The surface tension, Hydrophile-Lipophile Balance (HLB) and stability were investigated. All MDI-NPUDs had much lower surface tension than the dicyclohexyl methane diisocyanate (HMDI) based NPUD (HMDI-NPUD). By changing the feed ratio of MDI-NPUD, the properties of MDI-NPUD could be controlled
Microstructure and Performance of Fused Silica-Based Ceramic Core Reinforced by Mullite Fiber
Authors: Li Xin , Yao Jian Sheng , Liu Xiao Guang , Fan Hong Na , Niu Shu Xin
Published: March 2016

Fused silica-based ceramics are often used as sacrificial cores in investment castings to produce hollow, precise, and complex-shaped blades. In this work, the content of mullite fiber and its effects on mechanical and dimension behavior of silica-based ceramic cores were investigated. In order to simulate the single crystal blades casting process, the sintered samples were also heated up to 1540°C and kept for 0.5 h. Flexural strength test at 1540°Cwas carried out for the samples. The shrinkage, creep behavior and erode behavior were characterized. The results showed that in the premise of maintaining strength of materials, mullite fiber could decrease significantly the shrinkage. Many gains appeared on the surface of fiber after creep test of the core samples at 1540°C.
Low-Temperature Synthesis of Magnesium-Stabilized Aluminum Titanate Powder via Non-Hydrolytic Sol-Gel Method
Authors: Feng Guo , Jiang Wei Hui , Liu Jian Min , Zhang Quan , Hu Zi , Miao Li Feng , Wu Qian
Published: March 2016

Magnesium-stabilized aluminum titanate powder was prepared via non-hydrolytic sol-gel method using titanium tetrachloride and anhydrous aluminium chloride as precursors, anhydrous ethanol as the oxygen donor, magnesium powder, magnesium fluoride, magnesium ethoxide and anhydrous magnesium acetate as stabilizers. The effect of magnesium stabilizers on low temperature synthesis of aluminum titanate was investigated, and their role and mechanism in stabilizing aluminum titanate were also studied by XRD, FT-IR and thermal expansion dilatometer. The results show that introducing magnesium powder or magnesium fluoride can’t stabilize aluminum titanate, they also lead to the failure of aluminum titanate low-temperature synthesis at 750 °C due to its promotion of non-hydrolytic homogeneous condensation. Anhydrous magnesium acetate and magnesium ethoxide can react with aluminum alkoxide and titanium alkoxide in the precursor mixture to form heterogeneous condensation bonds, which promotes magnesium ion to dope into aluminum titanate lattice at 750 °C, and hence to improve its thermal stability.
Low Temperature Synthesis of Ultrafine Al2TiO5 Powders by Hydrolytic Sol-Gel Method
Authors: Zhang Quan , Jiang Wei Hui , Liu Jian Min , Feng Guo , Xu Gui Rong
Published: March 2016

Aluminum titanate (AT) ultrafine powder with high productivity ratio was prepared via hydrolytic sol-gel (HSG) method at 1250 °C, using aluminum nitrate (Al (NO3)3·9H2O) and titanium tetrachloride (TiCl4) as precursors, ethanol as solvent through solvothermal treatment process. Water required for hydrolysis reaction was supplied by the crystal water of aluminum nitrate itself. The effect of process parameters including filling ratio, solvothermal temperature and soaking time on the synthesis of AT powder was investigated by means of X-ray diffraction (XRD) and scanning electron microscopy (SEM). The cause of low temperature synthesis of AT was investigated. The result showed that excessive or insufficient filling ratio, too high or low solvothermal temperature, too long soaking time was not beneficial for the preparation of AT. The optimized ultrafine AT powder appeared at the decomposition temperature of 1250 °C with average particle size less than 1μm at a relatively high productivity ratio of 98 % with filling ratios of 60 %, solvothermal temperatures of 130 °C and soaking time of 30 min. The refinement of particles in the AT xerogel through solvothermal treatment process, and increasing reactivity of precursor, plays the key role in the low temperature synthesis of AT.
Effect of Polyvinyl Pyrrolidone Dosage on Barium Ferrite Fibers via Electrospinning
Authors: Chen Yue Guang , Liu Gui Fang , Wang Shi Jiao
Published: March 2016

Barium ferrite micro/nanofibers were successfully prepared via the electrospinning by using dimethyl formamide (DMF) as the solvent, poly vinyl pyrrolidone (PVP) as the spinning auxiliaries and iron nitrate and barium nitrate as raw materials. The effect of poly vinyl pyrrolidone on the structure, morphology, magnetic and microwave absorbing properties were investigated by scanning electron microscope (SEM), X-ray diffraction analysis (XRD), vibration sample magnetometer (VSM) and vector network analyzer (VNA). XRD patterns of the samples confirmed that when the additive content of PVP was up to 10%, (wt%) pure barium ferrite fibers formed under the condition of the same heat treatment. Also, the FE-SEM images showed that the morphology of the fibers improved with the increase of PVP content. Moreover, the VSM results demonstrated that the saturation magnetization can reach 54.7 emu/g when the PVP dosage is 14% (wt%) in the precursor solution.
Dual-Band Linear Polarization Transformer with Diode-Like Asymmetric Transmission Based on Composite Metamaterial
Authors: Cheng Yong Zhi , He Bo , Wu Chen Jun , Gong Rong Zhou
Published: March 2016

A dual-band linear polarization transformer with diode-like asymmetric transmission using a three-layer composite metamaterial was proposed and investigated numerically. The proposed three-layer composite metamaterial was comprised of two layers of asymmetric split-ring resonators and a sub-wavelength cross structures sandwiched symmetrically between these layers. By introducing the sub-wavelength cross structure into the asymmetric chiral metamaterial, an electromagnetic wave tunneling effect formed for the incident waves. Thus, the transmissions in the composite structures can be strongly modified, one of the two off-diagonal cross-polarized transmission (txy) of the Jones matrix is enhanced while all the others (txx, tyy, and tyx) are suppressed extremely at resonances. This present design for enhancing asymmetric transmission via polarization conversion can be used as many novel devices, such as optical isolators, asymmetric wave splitters, and circulators.
Preparation of SiO2 Matrix Composite with Tunable Dielectric Properties in Radio Frequency Range
Authors: Zhang Zi Dong , Qin Chen , Ji Xiu Jie , Wang Hui Min , Chen Shu Hui , Sun Kai , Fan Run Hua
Published: March 2016

In this paper, C/SiO2 composites were fabricated by self-assembly process combined with heat treatment. The X-ray diffraction (XRD) analysis, SEM and impedance analyzer were used to investigate the microstructure and radio-frequency dielectric properties of the composites. The results showed that the matrix of C/SiO2 composite with a periodical structure formed by the hexagonal stacking of SiO2 microspheres. The sheet carbon distributes in pores formed by SiO2 microspheres and act as the functional phase in the composite. The results indicate that the permittivity of C/SiO2 composite could be easily adjusted by controlling the content of Carbon in the composite. Both real and imaginary parts of the permittivity increase with the content of carbon, but decrease with the frequency.
A Promising Energy-Saving and Environmental-Friendly Lighting Device: High CRI White LED with Phosphor Materials
Authors: Liu Sheng , Zhou Bei Ying , Gu Shi Jia , Wang Lian Jun , Jiang Wan , Luo Wei
Published: March 2016

Two kinds of commercial LED phosphors (green phosphor LuAG:Ce3+ and red phosphor CaAlSiN3:Eu2+) with polymethyl methacrylate (PMMA) powders were mixed to prepare film phosphors with tunable emission peak in photoluminescence spectrum by flat vulcanizing machine under the temperature of 170 oC and pressure of 2 MPa. The physical phase, surface morphology, transmittance, luminescence spectra of samples were characterized by means of X-ray diffraction (XRD), Environmental scanning electron microscopy (ESEM), Ultraviolet-Visible (UV-Vis) spectrophotometry and Fluorescence spectrometer. The results show that the film phosphors phase was consistent with raw phosphors, phosphor particles were uniformly distributed, and fluorescence spectra with different proportions of phosphors in different position can be adjusted. Tested by HSP 3000 spectrum analyzer, the white LEDs fabricated by blue chip and composite film phosphor containing 5 wt% green phosphor and 1.5 wt.% red phosphor, which refers to the remote excitation technique, possessed color coordinate of (0.3715, 0.3280) and color rendering index (CRI) of 87 when it was driven at power of 36 V/140 mA, reaching the international advanced level.
Gradient Nano-Grained Cu and Cu-Zn Alloys Processed by Surface Mechanical Attrition Treatment
Authors: Yin Zhe , Sun Le Le , Shen Yu , Pang Yan Zhao , Yang Jian , Gong Yu Lan , Tao Jing Mei , Zhu Xin Kun
Published: March 2016

Cu and Cu-30wt.%Zn alloys with stacking fault energies (SFEs) of 78 mJ/m2 and 14 mJ/m2 were processed by surface mechanical attrition treatment (SMAT) at room temperature and liquid nitrogen (LN) temperature, respectively. The effect of SFE and deformation temperature on tensile properties of these samples was investigated. The tensile testing results indicated that the yield strength and uniform elongation of these samples enhanced simultaneously with decreasing SFE. Meanwhile, the LN-SMAT processed samples exhibited remarkably higher strength and slightly lower ductility compared to those processed at room temperature. The SFE affected the deformation mechanisms of metals greatly. X-ray diffraction (XRD) measurements indicated that the twin density increased while the average grain size decreased with SFE decreasing, and twinning became the dominant deformation mechanism. The relationship between microstructure and mechanical property is also discussed.
Microstructure and Mechanical Properties of Nano-Grained Dual-Phase Ni-Based Alloy
Authors: Sun Yan Le , Fu Li Ming , Lv Li Feng , Guo Run Jiang , Yao Xue Feng , Xu Song Qian , Shan Ai Dang
Published: March 2016

To provide insight into the mechanical behavior and microstructural evolution of bulk nanograined (NG) Ni-based alloys during annealing, the Ni-based alloy sheets with grain size about 50 nm was produced through severe cold-rolling at room temperature, and then the cold rolled (CRed) Ni-based alloys were annealed at different states. The evolution of the nanostructure of the CRed Ni-based alloy during annealing and corresponding change in mechanical properties was investigated. The results showed that the CRed Ni-based alloy exhibited prominent enhancement in the yield strength (YS), ultimate tensile strength (UTS), which increased respectively from 253 MPa to 1455 MPa, 684 MPa to 1557 MPa. Further increase of the YS and UTS were obtained in the annealed-CRed Ni-based alloy with dual-phase. The YS and UTS of the NG dual-phase Ni-based alloy was respectively 2013 MPa and 2061MPa, which was annealed at 700 °C for 1h. In terms of the microstructural evolution, lower density of defects on the grain boundary were observed and the nanograins can be maintained about 100 nm even when annealed for 30 h at 700 °C, which suggests high thermal stability at this temperature. Both the high thermal stability and strength are due to the formation of the γ′ precipitates and slight grain growth of the NG matrix.
Progress on the Applications of Piezoelectric Materials in Sensors
Authors: Wang Ding , Chen Jian Sheng
Published: March 2016

Piezoelectric materials, which can couple electrical and mechanical displacements, are one of the most important functional materials nowadays. They comprises piezoelectric monocrystals, piezoelectric polycrystals (piezoelectric ceramics), piezoelectric polymers, and piezoelectric composites. Sensors made of these materials can convert pressure, acceleration, flow rate, etc. to surface charge (voltage) that can be easily processed, and at the same time generate their own energy instead of consuming it. Compared to other electromechanical transduction technologies, piezoelectric sensors have the advantages of high environmental and chemical stability, broad temperature and frequency band, as well as self-sufficiency. Piezoelectric materials can also be used in various applications such as energy harvesters, actuators, transducers, and capacitors. This paper reviews the piezoelectric materials and their recent application progress on sensors and others. These published results show the developing trend of piezoelectric sensors to become lead-free, flexible, and with high performance.
Effect of Heat-Treatment on the Microstructure and Properties of SiO2-TiO2  Aerogels Synthesized via Supercritical Drying
Authors: Jiang Yong Gang , Qin Yan Qing , Feng Jun Zong , Feng Jian , Xu Lin
Published: March 2016

Monolithic SiO2-TiO2 aerogels were prepared via supercritical drying using tetraethoxysilane and tetrabutyltitanate as precursors and ethanol as solvent. Influence of the heat-treatment on the microstructure and properties of SiO2-TiO2 aerogels were investigated in detail. The results showed that the as-prepared SiO2-TiO2 aerogels had low densities, high specific surface areas, small average pore diameters, and three-dimensional nanoporous structures. The anatase TiO2 phase of SiO2-TiO2 aerogels could form during supercritical drying process, and the transition to rutile TiO2 phase occurred after experiencing 1200°C for 2 h. SiO2-TiO2 aerogels containing 30 wt% TiO2 (ST3) still presented relatively high specific surface area of 451 m2/g even they undergo the treatment of 1000°C for 2 h. And the SEM images indicated that the agglomerated particles derived from ST3 appeared gradually to some extent. The glassy luster of ST3 heat-treated at 1200°C for 2 h illuminates SiO2 started to vitrify. Besides, the thermal conductivity of ST3 at room temperature is up to 0.03257 W·m-1·K-1.
Effects of Microstructures on the Tensile Properties and Corrosion Resistance of High-Purity Magnesium
Authors: Feng Xiao Hui , Jia Hong Min , Liu Yun Teng , Li Yang De , Li Wei Rong , Zhang Tao , Yang Yuan Sheng
Published: March 2016

The microstructure, tensile properties at room temperature and corrosion rate in the 0.9% NaCl solution of the as-cast, as-extruded and as-drawn high-purity magnesium (99.99wt.% Mg) were experimentally investigated, respectively. Due to the coarse grains, both the tensile properties and corrosion resistance of the as-cast high-purity Mg were the lowest among the three states specimens, the yield strength (YS), ultimate tensile strength (UTS) and the elongation (EL) were 26.6MPa, 69.2MPa and 5.6%, respectively. The mass-loss rate of the as-cast high-purity Mg in the NaCl solution was 0.44g⋅m-2⋅h-1. For the as-extruded high-purity Mg, as the grains was remarkably refined, the YS, UTS and EL increased to be 108.3MPa, 152.7MPa and 27.0%, respectively, and the mass-loss rate become slower to be 0.25g⋅m-2⋅h-1. Attributed to the further refined grains, the YS, UTS and EL of the as-drawn high-purity Mg increased to 134.1MPa, 199.4MP and 15.3%, respectively, and the mass-loss rate reduced to be 0.12g⋅m-2⋅h-1. The experimental results in the present research indicated that the grain refinement can effectively improve both the mechanical properties and corrosion resistance of the high-purity Mg.
Low Temperature Co-Fired ZnNb2O6 Dielectric Ceramic Doped by B2O3
Authors: Yang Jian , Yan Ji Kang , Du Jing Hong , Yan Fang Chun , Kang Kun Yong , Yi Jian Hong , Gan Guo You
Published: March 2016

To lower the sintering temperature of ZnNb2O6 microwave dielectric ceramic, ZnNb2O6 doped with B2O3 were prepared by the traditional solid state reaction method. The effects of the amount of B2O3 (0.25-5.0wt.%) on the microstructure, density and electrical performances were investigated. The results show that a pure columbite ZnNb2O6 phase was obtained for all B2O3-doped ceramics. The microwave dielectric properties reached the maximum values of εr = 24.1, Q×f = 19502 GHz, τf = -52.19 ppm/°C for 1wt% B2O3-doped ZnNb2O6 ceramic sintered at 1050 °C for 4 h. All of evidences suggest that the enhancement of microwave dielectric properties is due to the enhanced ions-energy and ionic diffusion with the increase of sintering temperature. Furthermore, B2O3 doping can generate liquid phase and reduce the activation energy of diffusion to promote the materials sintering.
Effect of β Annealing and near β Zone Hot Deformation on the Microstructure and Texture of TC18 Alloy
Authors: Cui Yi Min , Zheng Wei Wei , Zhang Feng , Sha Ai Xue
Published: March 2016

Forged TC18 alloy billets with strong <100> texture were selected to investigate the effects of β annealing and near β zone hot deformation on the microstructure and texture by means of optical microscopy, XRD and EBSD techniques. The results showed that the original <100> fiber texture can’t be eliminated through β annealing although completed static recrystallization happened during annealing. After deforming in near β phase zone, the microstructures were composed of elongated β grains. A lot of small angle boundaries were observed near the original β grain boundaries, indicating that dynamic recovery controlled the deformation. Dynamic recrystallization grains can only be seen at the original β grain boundary at the strain of 50%. <100>//TD and <111>//TD texture were generated during the near β zone hot deformation. Annealing at dual phase zone after hot deformation can effectively reduce the proportion of grains with <111> orientation, but the <100>//TD texture still existed.
Effect of Hot Forging Strain Rate on the Microstructure and Mechanical Properties of TC4-DT Titanium Alloy
Authors: Shang Guo Qiang , Wang Xin Nan , Fei Yue , Li Jing , Zhu Li Wei , Zhu Zhi Shou
Published: March 2016

The microstructures, tensile properties and fatigue property of TC4-DT titanium alloy hot die forged under different strain rates were investigated. The results show that the microstructures and mechanical properties of TC4-DT titanium alloy die forging using different strain rates can meet the requirement of technical standard. At the strain rates of 1mm/s and 10mm/s, the microstructure was not sensitive to the strain rate, and the alloys showed uniform, fine and fuzzy crystal grains, and no metallurgical defects. However, more uniform tensile properties in different orientations were obtained by the low strain rates (1mm/s), while the high strain rate (10mm/s) could lead to slightly increase in strength but obviously decline in ductility. High fatigue strength could be obtained by the low strain rate, but the fracture toughness and fatigue crack growth rate were not sensitive to the strain rates.
Influence of HA and Environmental Factors to the Damping Performance of HA/Mg-3Zn-0.5Zr Composites
Authors: You Chen , Zheng Hao Ran , Jin Dan Dan , Wang Lei , Wang Meng Meng , Chen Min Fang
Published: March 2016

Vibration and noise are the dangers for equipment, human health and environment. Developing of a new Mg matrix composite with high damping performance and high strength rate has been acknowledged as an important approach for the reduction of vibrations and prevention of noise. In this paper, xHA/Mg-3Zn-0.5Zr (x=0.5wt.%, 1wt.%, 1.5wt.%) composites were prepared by vacuum induction melting and hot extruding. The microstructure and damping performance were observed and measured using an optical microscope and a dynamic thermomechanical analysis apparatus (DMA), respectively. The influence of HA and environmental factors (temperature, frequency and strain amplitude) on the damping performance of HA/Mg-3Zn-0.5Zr composites were studied. The results showed that the damping performance of HA/Mg-3Zn-0.5Zr composites increased with increasing HA content and strain amplitude. The damping mechanism was in line with the G-L theory and interface damping theory. The damping values were strongly amplified at 150-300°C. The plot of damping versus temperature showed a peak for the Mg-3Zn-0.5Zr-1HA composite at 235°C. The low frequency damping values of xHA/Mg-3Zn-0.5Zr were higher than the high frequency damping values. It is suggested that the change of damping by a variety of external factors is due to the presence of different dominant damping mechanism at different conditions. Furthermore, it was found that at increased HA content, the grain size of HA/Mg-3Zn-0.5Zr composites decreased and the tensile strength and elongation of HA/Mg-3Zn-0.5Zr composites improved. This work will be beneficial for the study of Mg based joint implant materials with high vibration damping performance.
Ambient-Temperature and High-Temperature Tensile Properties of Investment Casted Titanium Matrix Composites with B4C Additions
Authors: Wang Ji Heng , Huang Guang Fa , Li Jiu Xiao , Mao Jian Wei , Guo Xiang Long , Lu Wei Jie
Published: March 2016

Titanium matrix composites (TMCs) were prepared by investment casting in a consumable arc skull casting furnace. The effects of B4C additions on ambient-temperature and high-temperature tensile properties of TMCs were investigated. It has been found that with the addition of B4C, the microstructure of TMCs was refined and the strength improved. The strength enhancement of the TMCs is ascribed to the combined effects of the second-phase strengthening, grain refinement strengthening and the solution strengthening. The grain refinement and solution strengthening effects play a main role in the yield strength enhancement of TMCs at ambient temperature, and the second-phase strengthening of TiB whiskers and TiC particles plays a more important role at high temperature.
Effect of Carbon on the Microstructural Evolution and Thermal Fatigue Behavior of a Ni-Base Superalloy
Authors: An Ning , An Yang , Fan Qiang , Fu Zu Ming , Li Zhen Rui , Zhang Yong Yue
Published: March 2016

The effect of carbon content on the microstructural evolution and thermal fatigue behavior of Ni-Cr-Fe-Mo alloy with different carbon content was carried out at temperature ranging from 20°C to 920°C. The microstructure evolution was detected and the length of thermal fatigue cracks was measured. The results revealed that all the alloys are mainly composed of γ phase and carbides. With the increase of carbon content, the volume fraction of carbides increase and the morphology varies from blocky to script-like and sheet-like. The microstructural features exert influence on the thermal fatigue cracks of the alloys with different carbon content. Considering the thermal fatigue properties, the optimum carbon content of the Ni-Cr-Fe-Mo alloy superalloy should be below 0.08wt.%.
Influence of Carbides on Stress Rupture Property of a Ni-Base Superalloy
Authors: Li Zhen Rui , An Ning
Published: March 2016

This study aims to explore the influence of morphology and distribution characteristic of carbides on stress rupture property at high temperature. The stress rupture life at 850°C/325MPa was tested. Meanwhile, microstructure and fracture morphology of stress rupture specimens were observed by scanning electron microscopy. The types of carbides were identified and the carbide size was also measured. The results show that the alloys with small size, uniformly distribution and moderate number of carbides present a high stress rupture performance.
Laser Brazing Research on Carbon Steel and Stainless Steel Applying Fe-Based Amorphous Coating
Authors: Song Jing Hui , He Sheng Jie , Xu Qi Sheng , Liang Fei Fei , Hou Yong , Jiang Run Sen
Published: March 2016

The Fe-based amorphous ribbons were prepared by the copper roller melt spinning method, and then the laser brazing was carried out using the amorphous ribbons as the brazing filler metal. Subsequently, laser was used to melt and brazed the plain steel and stainless steel whose surfaces had been pre-coated with the Fe-based amorphous brazing. The micro Vickers hardness tester, metallographic microscope, X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to characterize the hardness, morphology, microstructure and composition distribution of the welded joints, respectively. The results showed that the prepared amorphous ribbons were of fully amorphous structure. The ordinary steel and stainless steel were well-connected, and mutual dissolution and diffusion had occurred between the solder and the base metal, which achieved the metallurgical bonding. The Fe-based amorphous ribbons were used to solder heterogeneous sheet metals that were difficult to be welded directly. New attempts were made in the hard-connected metal plate field, and the paper could provide concrete references for soldering metals with low invasion, which is of great significance in promoting the development and application of amorphous brazing.
Effect of Mn Contents on the Phase Transition of the High Entropy Alloy Prepared by Laser Cladding
Authors: Liu Shi Da , Peng Cun Yuan , Ma Ming Xing , Liu Wen Jin , Zhang Wei Ming
Published: March 2016

Al1.3FeCoNiCuCr high entropy alloy (HEA) coatings were prepared by pre-placed laser cladding on 921A steel substrate, and the study on the phase transition of the Al1.3FeCoNiCuCr coating due to the introduction of Mn was conducted. The combination of TEM and XRD results showed that the Al1.3FeCoNiCuCr HEA coatings without Mn addition typically consisted of two kinds of grains, i.e., one is composed of only FCC phase, and the another is a mixture of BCC and FCC phases. The two phases were of similar ratio in the coatings, while nanoparticulate precipitates were observed in the bcc phase. When 3 wt. % Mn was introduced into the alloy, the coatings consisted of also FCC and BCC phase. However, most of the grains were in FCC phase, while the BCC phase with a lath shape only distributed between the FCC phases. High hardness nanobanded precipitates were observed in the FCC phase. It is clearly revealed that the phase structure of Al1.3FeCoNiCuCr coatings undergoes a dramatic transition due to the introducing of Mn.
Meso-Structure Design of B4C-Al/Al Composites by Hot Pressing
Authors: Li Hui , Zhang Yi Tan , Ameyama Kei , Yang Hai Jun , Liu Zhi Guo , Ma Chao Li
Published: March 2016

According to the theory of meso-structure design, milling powders were blended with un-milled Al particulate to increase ductility. Two kinds of Al particulate-toughened composites were fabricated by using powder metallurgy method, where the mass fraction of B4C in the B4C-Al agglomerate particles was 40%, but 32% and 16% in the whole composite. The microstructure of composites was examined by scanning electron microscope (SEM), and its mechanical properties were studied. The results indicate that Al particulate-toughened sample has a slight plasticity with bulks of aluminum alloy in the composite. But meso-structure design has no effect on improvement on the plasticity and toughness of the sample B4C-Al/Al (16%)(3#), where the mass fraction of B4C in the whole composite is 16%. In the present study, the strengthening and deformation mechanism of the composites were also discussed.
Fabrication of W-Cu/Lu2O3 Composites with High Strength and Electrical Conductivity Prepared by Electroless Plating and Powder Metallurgy
Authors: Lu Ze Long , Luo Lai Ma , Zhang Jun , Qin Yong Qing , Huang Xin Min , Luo Guang Nan , Zhu Xiao Yong , Zan Xiang , Cheng Ji Gui , Wu Yu Cheng
Published: March 2016

W–Cu (0, 0.25, 0.75, 1.5, and 3 wt.%)/Lu2O3 composite materials were prepared through electroless plating with simplified pretreatment method and powder metallurgy. The phases and morphologies of the W–Cu/Lu2O3 composites were characterized by X-ray diffraction, field emission scanning electron microscopy and energy dispersive spectroscopy. The relative density, microhardness, electrical conductivity, and bending strength of the sintered samples were examined. The experimental results show that W–Cu composites with uniform structures can be obtained with pretreated W using the simplified method, followed by electroless Cu plating. The microstructure and properties of the composites were significantly affected by the addition of Lu2O3 nanoparticles, resulting in high electrical conductivity and strength. The electrical conductivity of W–Cu/1.5 wt.% Lu2O3 composites reached 63.3%, which is higher than the national standard value of 50.71%. The bending strength of W–Cu/1.5 wt. % Lu2O3 reached 1306.7 MPa, which is 65.41% higher than the national standard. These results may be attributed to the uniform distribution of refined particles with Lu2O3 content increased to 1.5 wt. %.
Interface and Damping Capacity of Mg/Al Multilayered Composite Produced by Accumulative Roll Bonding
Authors: Liu Zhong Ming , Chen Hong Mei , Guo Wei Peng , Zhang Jing , Jin Yun Xue
Published: March 2016

Mg/Al alloy multilayered composites were produced by accumulative roll bonding (ARB) technique. The microstructures of Al and Mg alloy layers were characterized by scanning electron microscopy, and damping capacity of the composite was tested by dynamic mechanical analyzer.It can be found that the diffusion layers were produced in Al and Mg alloy layers, and the diffusion layers increased with increasing of the ARB pass. With the increasing of ARB pass, the room temperature damping value of Mg/A1 multilayered composite presented a downward trend. The temperature damping spectrum of the composite had two internal friction peaks, with the increasing of the ARB pass, the peak height of P1 peak increased gradually and P2 peak moved to low temperature gradually.
Migration Characteristics and Degradation Kinetics of Bisphenol A
Authors: Sun Zhuo Jun , Gao Jian , Liu Hui , Pan Shu Zhen , Zhang Shu Li , Yang Lun Hua , Song Xiao Yun , Gao Jian Guo
Published: March 2016

This paper study the migration characteristics and degradation kinetics of bisphenol A using TGA - gas chromatography - mass spectrometry and found that bisphenol A polycarbonate in the thermal oxidative aging conditions of 130 °C de-gradated to bisphenol A. At the range of 0 h to 120 h, the bisphenol A content of environmental hormones increased with time. When it reached 120 h, bisphenol A environmental hormone content decreased slightly with aging time. The content of bisphenol A reached 495mg/kg when the thermal oxidative aging time was 168 h, which was decreased compared to the content of 442mg/kg at 120 h. Polycarbonate thermal decomposition kinetics study showed that the thermal decomposition of polycarbonate can be divided into three phases. The first thermal decomposition occurred at the range of 415° C to 425 ° C, the polycarbonate end groups fracture of the second stage at 493.6°C , the main fracture of the main chain rearrangement and crosslinking, and the third stage at 598.7°C, the degradation of the chain continues to decompose and the decomposition of the crosslinked carbon precursor; thermal oxidation aging of polycarbonate decreased the heat stability and promote the thermal decomposition of polycarbonate. Comparing the oxidation induction period, thermal weight loss rate and activation energy of polycarbonate before and after thermal oxidative aging, it c found that the thermal stability of the hot oxygen aging of polycarbonate is reduced.
Kinetics of Dynamic Recrystallization of 18 Ni Maraging Steels
Authors: Li Ni , Zhao Fei , Zhang Huan , Ren Yong Hai
Published: March 2016

The dynamic recrystallization behavior of 18 Ni maraging steels was investigated by hot compression tests at temperatures ranging from 900 °C to 1100 °C and strain rates ranging from 0.001 to 1 s-1. Based on the flow curves from the tests, the effects of temperatures and strain rates on the dynamic recrystallization behavior were analyzed. The strain-hardening rates versus stress curves were used to determine to the critical strain, the peak stress (strain), the saturated stress and the steady stress. With the assistance of the process parameters, constitutive equations were obtained and the activation energy was determined to be 413544.96 J/mol. The dependence of the characteristic values on Zener-Hollomon was found. The dynamic recrystallization kinetics model of the tested steels was constructed and the validity was confirmed based on the experimental results.
Study on the Solidification of Sn-Pb Alloy under Direct Current Field by Synchrotron X-Ray Radiography
Authors: Yang Fen Fen , Cao Fei , Li Ren Geng , Kang Hui Jun , Huang Wan Xia , Wang Tong Min
Published: March 2016

In this paper, synchrotron X-ray radiography was used to study the grain refining performance of direct current (DC) during the solidification of Sn-50 wt.% Pb alloy. Based on the radiographs, the variations of equiaxed grain number and dendrite growth rate with time were measured and analyzed. It is shown that DC mainly affects the microstructure formation through changing the nucleation behavior and the dendrite growth rate. When DC was applied during the whole process of solidification, the nucleation was enhanced and the dendrite growth was suppressed, which resulted in significant grain refinement.
Analysis on Internal Defect of 319S Aluminum Alloy Impeller by Semi-Solid Thioxcasting
Authors: Jing Yan Hong , Lu Hong Xing , Li Da Quan , Zhu Qiang
Published: March 2016

In the present investigation a batch of impellers made of 319S aluminum alloy with about 300 pieces and produced by semi-solid thixocasting process were subjected the ultrasonic testing (UT). The experimental results revealed that the equivalent size of the defects in the impellers was not more than φ0.4mm FBH+12dB. And there were two main types of defects in 12 mm depth area from the machined surface, where defect was apt to form. One type was single defect and the other was intensive defect. Moreover, other nondestructive testing (NDT) was used to test some impellers containing typical defect, and the result suggests that UT was more sensitive than x-ray testing. The defects existed in the impellers were investigated by Optical Microscope (OM) and Scanning Electron Microscope (SEM) equipped with Energy Dispersive Spectrometer (EDS). The observation showed that the both types of defects existed in eutectic zone. The single defect derived from billet and the intensive defect came from die casting process.
Effect of Residual Stresses on Ductile Crack Growth in Pipeline Steel
Authors: Zhuo Xiao Min , Xu Jie , Li Peng Peng , Fan Yu , Sun Zhi
Published: March 2016

In this study, the effects of residual stresses on the ductile crack growth resistance was investigated using single-edge-notched bending (SENB) and single-edge-notched tension (SENT) specimens as well as axisymmetric model. Weld residual stresses were introduced by the so-called eigenstrain method. The crack tip opening displacement (CTOD) and constraint parameter R were calculated for different specimens and residual stresses. Results show that the residual stresses slightly reduced the ductile crack growth resistance. However, crack tip constraint R elevated with the increase of residual stress.
Estimation of Average Strain Rate during Equal-Channel Angular Pressing
Authors: Liu Fan , Liu Ying , Wang Jing Tao
Published: March 2016

In plastic deformation, the strain rate is a crucial factor to influence the constitutive behavior of materials such as the flow stress evolution, dislocation slipping, and deformation heat generation. In the present work, a formula based on the volume flow rate rule in plastic deformation was proposed to estimate the average strain rate of materials during equal-channel angular pressing (ECAP). It has been found that both the deformation parameters (channel angle Φ, corner angle Ψ, channel width d, and pressing speed v) and material characteristics (strain hardening behavior) can influence the average strain rate during ECAP. The present model was compared with two other models for estimating the strain rate and numerical values calculated by four different finite element methods (FEM). The result of the present model is in good agreement with the numerical strain rate values by FEM at various values for channel angle Φ and corner angle Ψ.
Effect of Mg and Cu Additions on Microstructure and Mechanical Properties of Squeeze Casting Al-Si-Cu-Mg Alloy
Authors: Liu Hai Jun , Li Lie Jun , Niu Jian Wei , Gao Ji Xiang , Ren Chuan Dong
Published: March 2016

The effects of Mg and Cu additions with different contents on the mechanical properties of Al-Si alloy prepared by indirect squeeze casting have been experimentally investigated. The microstructure and mechanical properties of as-cast and T6-treated Al-Si-Cu-Mg alloys were tested by OM, SEM, DSC and tensile measurement, where the samples were produced by artificial aging at 180°C for 8 h after solution treatment at 540°C for 4 h. It has been found that for the as-cast alloys, with increasing contents of Mg and Cu the tensile strength (UTS) and yield strength (YS) increased, while the percentage elongation (El) decreased. And the optimal mechanical properties of Al-Si-Cu-Mg alloys were obtained under the content ratio of Cu/Mg within 4, where the UTS and El reached 426 MPa and 6.3% after T6 treated, respectively.
Effect of Ultrasonic Vibration and Applied Pressure on the Microstructure and Mechanical Property of Al-5.0Cu-0.6Mn-0.6Fe Alloys
Authors: Zhao Yu Liang , Zhang Yang , Luo Zhi , Wang Zhi , Zhang Wei Wen
Published: March 2016

Al-5.0Cu-0.6Mn-0.6Fe alloy was obtained for the first time using ultrasonic vibration and squeeze casting simultaneously. The effect of ultrasonic vibration and applied pressure on the microstructures and hardness of Al-5.0Cu-0.6Mn-0.6Fe alloy were studied. The results indicated that the ultrasonic vibration and applied pressure promoted the formation of smaller α-Al globular grains. In particularly, with the treatment of ultrasonic vibration or applied pressure during solidification, the brittle Fe-rich imtermetallic compounds in Al-5.0Cu-0.6Mn-0.6Fe alloy became more refined and changed from Chinese script shape to polyhedral shape, which improved the mechanical property. Furthermore, these effects on the grain refinement and Fe-rich intermetallic compounds became more significant by using ultrasonic vibration and applied pressure concurrently during solidification. This process technology is helpful for the development of high performance aluminum alloys with low cost as well as for green casting.
Solidification Behavior and Mechanical Properties of Al-Si-Mg Alloy with Ti Addition
Authors: Xu Cong , Wang Cheng Yuan , Yang Hai Jun , Liu Zhi Guo , Yamagata Hiroshi , Ma Chao Li
Published: March 2016

The solidification behavior, microstructural evolution and mechanical properties of Al-Si-Mg foundry alloy with different Ti additions were investigated in the present study. The solidification behavior of those A357 alloys was analyzed through thermal analysis. The microstructures were examined by optical microscopy (OM), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). The results showed that the addition of Ti could refine grains of A357 as-cast alloy due to a good restriction on the grain growth, but Ti could not refine secondary dendrite arm spacing (SDAS), thus mechanical properties of the A357 as-cast alloy did not improved significantly. After T6 heat treatment, the microstructure with α-Al dendrites with the Al-Si eutectics at interdendritic space was replaced by a homogeneous α-Al matrix with a nonuniform dispersion of discrete, spheroidizing and coarse silicon particles. Hence, compared with the as-cast alloys, both of the strength and ductility of the T6 treated alloys are significantly improved, and an optimal combination of strength and elongation of the A357 alloy can be achieved by the 0.8 wt.% Ti addition after T6 heat treatment.
Morphology of Iron-Zinc Coating for Hot Press Forming Steel
Authors: Fang Fang , Hu Kuan Hui , Wei Hai Li , Chen Yi Ming , Huang Feng
Published: March 2016

The coating morphology of a hot press forming steel galvanealed by HDPS (hot dipping process simulator) in laboratory was studied in the paper. The results show that, firstly from thermodynamic calculations, the intermetallics increased the melting point of Zn, and it is possible to avoid the melting and volatilization of zinc coating for hot press forming steel strip, when the coating mainly consists of δ phase (~10% Fe) in galvanealing process, and lower re-austenization temperature (below 782°C) in hot press forming process. Secondly, according to the SEM morphology in the paper, the zinc coating formed an alloy predominantly composed of delta (δ) phase, a low iron zeta (ζ) phase formed on the surface, and a high iron gamma (Γ) phase formed at the interface with the steel substrate. The hard and brittle Γ phase failed to grow up on the interface of coating and matrix which results in high shear stress and good coating adherence.
Study on Microstructures and Components Uniformity of 7050 Aluminum Alloy with Annulus Electromagnetic Stirring Casting
Authors: Wang Ya Bao , Zhang Zhen Lin , Li Bao , Gao Zhi Hua , Zhang Zhi Feng , Xu Jun
Published: March 2016

7050aluminum alloy billets processed by semi-continuous casting were studied using conventional casting (N-EMS), conventional electromagnetic stirring casting (EMS) and annulus electromagnetic stirring casting (AEMS), respectively. Adopting the method of mathematical statistics, Zn, Mg, Cu chemical component uniformity and the microstructure of 7050 aluminum alloy billets were analyzed. The results showed that the high chemical component uniformity of the AEMS billets were obtained compared with N-EMS and EMS. The Zn, Mg, Cu element component variance was reduced 26% compared with EMS. And the A-EMS process exhibited superior grain refinement and remarkable structure homogeneity, which mainly consisted of rosaceous and nearly globular structure. The average grain size for AEMS sample was 42μm, and the grain shape factor was about 0.68.
Microstructure and Mechanical Properties of Al-1.1Mg-0.6Si-0.4Cu Alloy Manufactured by Casting-Forging Integrated Technology
Authors: Wang Shun Cheng , Song Dong Fu , Xu Jing , Zheng Kai Hong
Published: March 2016

In the present investigation the casting-forging integrated technology was adopted to manufacture Al-1.1Mg-0.6Si-0.4Cu alloy automobile brake calipers. The effect of forging pressure on the microstructure and mechanical properties of Al-1.1Mg-0.6Si-0.4Cu alloy calipers were studied. The results showed that the shrinkage porosities and cracks in the Al-1.1Mg-0.6Si-0.4Cu alloy calipers could be removed by the forging process. The ultimate tensile strength and elongation of Al-1.1Mg-0.6Si-0.4Cu alloy calipers increased with the increase of forging pressure. When the forging pressure was 120 MPa, the ultimate tensile strength and elongation of Al-1.1Mg-0.6Si-0.4Cu alloy calipers with T6 heat treatment were 365.3 MPa and 11.5%, which were improved by 22.8% and 38.2%, respectively compared with that of Al-1.1Mg-0.6Si-0.4Cu alloy calipers without forging. The tensile fracture images revealed that the fracture modes of Al-1.1Mg-0.6Si-0.4Cu alloy calipers were more ductile at higher forging pressure.
Effect of Heat Treatment on the Microstructure and Property of Al-Si-Mg Alloy
Authors: Guan Liu Yi , Li Bo Long , Qi Peng , Wei Li Jun , Nie Zuo Ren
Published: March 2016

The as-casted Al-Si-Mg alloy was treated by solution and aging process of 545°C/10h/water cooling plus 175°C/6h /air cooling. The effect of heat treatment on the microstructure and mechanical property of Al-Si-Mg was investigated by metallographic analysis, scanning electron microscopy, energy dispersion spectrum analysis and mechanical testing. The experimental results showed that the alloy had the ultimate tensile strength (UTS) of 317MPa and the elongation of 2%, and suitable for squeezing cast. During solution treatment, the plate-like eutectic Si particles became small granular or short bacilliform morphology, and the non-uniformly distributed eutectic phase was eliminated substantially. In addition, Si particles distributed uniformly and finely in the matrix. The tensile strength of as-casted alloy was 180 MPa, while it was up to 317 MPa after solution and aging treatment process, and the elongation increased from 2% to 3%, which is consistent with the microstructure. Fracture surface analysis showed that fracture mode of the alloy transformed from brittle fracture into co-existence of ductile fracture and brittle fracture during T6 treatment.