ZHENG Liang, XIAO Cheng-bo, ZHANG Guo-qing, YUAN Hua, HAN Bo, TANG Ding-zhong. Investigation of the Master Alloy Cleanliness of High Cr Content Cast Ni-base Superalloy K4648[J]. Journal of Materials Engineering, 2012, 0(3): 1-7.
Two heats of high Cr content cast Ni-base superalloy K4648, which possess significant differences on impact ductility, were investigated comparatively. The cleanliness of K4648 master alloy was studied by chemical analysis on the alloy composition and gas content, electron beam button (EB button) technique evaluation on inclusions and microstructure observation of chromium metal used in raw materials. The results indicate that the two heats of K4648 master alloy have no obvious difference in major constituent. However, 1# master alloy possesses a high oxygen level of （20.5?75）?10-6, which is much higher than 6?10-6 of 2# alloy. The impact ductility of 1# alloy is less than half that of 2# alloy and lower than the K4648 specification requirement of 19.6J/cm2. The electron beam button (EB button) experiment could effectively aggregate the inclusions in specific region. The inclusions were identified as (Y,Ce)-rich oxide and Al-rich oxide. It is evident that the addition of rare earth (RE) element such as yttrium and cerium in high Cr content cast Ni-base superalloy K4648 can snatch the free oxygen or sulfur, and form stable RE oxides or sulfides to purify the master alloy. About 15%（atom fraction） element O is solusionized in the chromium metal matrix which is used in raw materials for K4648 master alloy. Some Cr-rich oxides and (Cr,Al,Si)-rich oxides distributes in the Cr matrix. In addition, a N-bearing and O-depletion zone exists in the Cr matrix. The Vickers microhardness of this region can reach 8.2GPa, which is 6 times harder than 1.3GPa of Cr matrix, indicate that the element N can harden and embrittle the chromium metal.
ZHU Jing, LIU Yong-guang, ZHAO Yan-qin, WANG Ling. Study on the Concentration-gradient LiNixCoyMn1-x-yO2 Electrode Material Prepared in the Molten Salt Method[J]. Journal of Materials Engineering, 2012, 0(3): 8-11.
The layered cathode material LiNi1-x-yCoxMnyO2 was prepared at different temperatures in the molten salt method. Experiments were carried out to test the charge and discharge properties of the material. The XRD and SEM experiments show that the prepared material has a typical α-NaFeO2 layered structure with the particles diameter range from 200nm to 400 nm. The capacity of the prepared material at 800℃ is 166.8mAh/g with a retention of 99% in the first charge-discharge cycle, tested within the voltage cut off limits of 2.75 and 4.5 V. Besides, the results show that the material demonstrates a good rate capability.
YANG Lu,ZHOU Yuankang,LI Yi,WU Xuemei，CHEN Jianhai，WANG Chenxiang. Investigation on Auto-restoration Performance of Palygorskite/Ag Composite Nanomaterial Additive[J]. Journal of Materials Engineering, 2012, 0(3): 12-16.
The influence of friction and wear performance with palygorskite (P) /Ag nanocomposite lubricant additive on 45# steel45# steel pair treated by quenching and tempering were investigated by MMU10G friction wear testing machine in the condition that friction surfaces were lubricated by the 150N base oil contained P/Ag composite nanomaterials in the mass fraction of 4%. Wear mass losses were estimated by weighing, and the topographies of worn surfaces were characterized by SEM and the main elements of the final surfaces were detected by EDX, moreover, using metallographic microscope observed the topography of autorestoration film at different growth stages. The results show that the nanoP/Ag composite additive reduces the wear mass loss of the 45# steel45# steel pair as high as 37.5%. The main elements of autorestoration film contain Fe,Si,O,C,Al,Mg,Ag, which proves that the composite additive participates in the forming of autorestoration film. The autorestoration film mainly forms in the time after 10h（or after running for 18km）.
CHEN Ling, YUWEN Xuan-xuan, ZHONG Shu-jin, XIE Jin-ting. Methodological Research for Defining Interface Heat Transfer Coefficient in Metal Mould Casting[J]. Journal of Materials Engineering, 2012, 0(3): 17-21.
In the process of numerical simulation of casting solidification, the interface heat transfer coefficient was traditionally used to reflect the influence of the heat resistance. Among several factors to make the precision more precisely, this coefficient played an important role in affecting the precision. In order to determined a higher precision, the ANSYS software served as a platform. Basing on the experiment of temperature measurement, the 0.618 method was adopted to select the coefficient, considering the different meet places between the cast and the mould, and the effects made by different interface heat transfer coefficient. By using the least-squares method, a mathematic mode of the realization between time and the interface heat transfer coefficient was set up in order to simulate temperature fields of metal mould casting solidification. And then, a conclusion that a reasonable temperature distribution can be made by comparing the simulation result with the testing data. The result provides a method to get the accurate interface heat transfer coefficient.
WANG Xiao, WANG Zuo-cheng, WANG Xie-bin, LI Xian-da, GAO Jun-qing, ZHAO Xiu-ling. Effect of Subcritical Quenching on Microstructures and Mechanical Properties of Boron-nickel Added Nb-treated HSLA H-beam[J]. Journal of Materials Engineering, 2012, 0(3): 22-27.
Microstructures and mechanical properties of subcritical/complete quenched and quenched & tempered boron-nickel added Nb-treated high strength low alloy (HSLA) H-beams were investigated. The results indicate that the subcritical quenched and tempered steel exhibits good combination of strength, plasticity and toughness. Yield strength, tensile strength and elongation of the subcritical quenched and tempered steel is 512MPa, 595MPa and 27%, respectively. Its ductile-brittle transition temperature is -88℃. The quasi-polygonal ferrite and dispersed small carbides make sure high plasticity without dramatic decrease of strength after tempering. The carbides promote grain refinement by pinning effect and have little influence on toughness.
LU Tao, PAN Ye, DONG Xun. Microstructures and Properties of Co(Ti)-Al2O3 Cermets Prepared by Combustion Synthesis[J]. Journal of Materials Engineering, 2012, 0(3): 28-31.
The ferromagnetic Co(Ti)-Al2O3 cermets were prepared by combustion synthesis in thermal explosion mode associated with densification technique. The reaction temperature was controlled by partial replacement of high-exothermic reaction system Al-CoO by low-exothermic Al-TiO2 and by proper content of Al2O3 diluents adding for the purpose of heat absorbing. The results show that along with the increasing of adding Al-TiO2 system in the reactant mixtures, the combustion temperature of preparing Co(Ti)-Al2O3 cermets decreases, so that the metal phase shows smaller dimension and more homogeneous dispersion; meanwhile, a transitional region occurs between metal and ceramic phases, which increased the phase interfacial strength. The saturation magnetization of Co(Ti)-Al2O3 cermets increases with the increasing of Co content in metal phase and the top of Ms is 37.2849Am2/kg while the coercive force changes from 3997.6A/m to 5615.4A/m, which means the magnetic property of this series of composites is between soft-magnetic and half-hard-magnetic.
LUO Feng-zuan, WU Guo-you, SHAO Zai-dong, CHENG Xuan, YU Yu-xi. Effects of Preparation Conditions on Hydrophobic Silica Aerogels via Ambient Pressure Drying[J]. Journal of Materials Engineering, 2012, 0(3): 32-37.
The preparation of silica aerogel via ambient pressure drying has become of great importance recently. A key to improve the properties of aerogels is to optimize the preparation parameters. Using tetraethoxysiliane (TEOS) and methyltriethoxysilane (MTES) as the silica source and co-precursor, respectively, the hydrophobic silica aerogels via ambient pressure drying process were prepared by sol-gel method with aging and two-step surface modification by trimethylchlorosilane (TMCS)/n-hexane/ethanol (EtOH) solutions. The BET, FT-IR, SEM, TEM and contact angle measurements were used to characterize the structure of silica aerogels. The effects of hydrolyzing time, aging time, aging temperature and surface modification reagents on the properties of silica aerogels were systematically investigated. The results revealed that the silica aerogels prepared using 16 h hydrolyzing time, 48 h aging time at 55℃ and surface modified by the molar ratios of TMCS/TEOS being 1.56 for 48 h possessed the best properties. The porosity and specific surface area were 92% and 969m2/g, respectively, with the contact angle of 157?.
WANG Hongl，，LIU Hongyu，ZHOU Peng，FEI Yang,HUANG Yu，CHEN Hao.
Influence of Co Microalloying on Microstructure and Drawing Properties of Highgrade Tire Cord Steels[J]. Journal of Materials Engineering, 2012, 0(3): 38-42.
The law of microstructures and properties of 80 and 100grade tire cord steels with Co microalloying were investigated, in order to alleviate the precipitation of grain boundary cementite (GBC) and enhance their strengths and cold drawing properties. The microstructure, precipitation of GBC and the interlamellar spacing of pearlite of specimens with various Co contents were observed and measured using electron scanning microscope (SEM); the mechanical properties after hot working and cold drawing were measured by means of mechanical testing machines. It was shown that, the Co microalloying can decrease greatly the size of pearlite colony on condition of natural cooling; the ultimate strength were increased and the reduction of area decreased but GBC became severe with the contents of Co increasing. GBC were suppressed and cold drawing work hardening rate of highgrade tire cord steels improved after salt bath patenting.
GE Ming-liang, JIA De-min. Study on Intercalating Stage of Natural Rubber/Clay Nanocomposites by X-ray Diffraction[J]. Journal of Materials Engineering, 2012, 0(3): 43-46.
The organic clay(Org-clay) was prepared by alkyl ammonium ions treating of Na-montmorillonite, and then the natural rubber(NR)/Org-clay nanocomposites were prepared by intercalation method. The structure and morphology of the nanocomposites were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM), the results show that Org-clay can disperse in the rubber matrix at nanometer size. The result of XRD indicated that natural rubber chains could be intercalated into the interlayer of the Org-clay during the mixing stage. During the vulcanizing stage, with increasing vulcanization time the basal space of Org-clay was slightly increased. At the end of rubber vulcanization process, the NR chains were fixed in the interlayer of the Org-clay because of cross-linked network structure of vulcanizate.
ZHAO Xiu-ming, YANG Jin-feng, ZHANG Yong-jian, HUI Wei-jun, YU Tong-ren, WANG Zhang-zhong. Hydrogen Induced Delayed Fracture Behavior of Cold Hardening Microalloyed Bainitic Steel[J]. Journal of Materials Engineering, 2012, 0(3): 47-51.
The hydrogen induced delayed fracture behavior of a newly developed low carbon Mn-B-Ti type cold hardening microalloyed bainitic steel was studied using electrochemical charging and slow strain rate test (SSRT). It is found that charging of hydrogen significantly impairs the delayed fracture property of specimen both at as-hot rolled and as-cold drawn conditions. The decrease of anti-delayed fracture property is more noticeable when cold drawing reduction γ is lower than 20%. However, aging treatment has a beneficial effect on improving the anti-delayed fracture property of cold drawn specimen, and this improvement is more noticeable when aging temperature is higher than 200℃.
LI Ling, TIAN Jin-li, CHEN Jian-nan. Synthesize Hydantoin Epoxy and Preparation Cured Hydantoin Epoxy/HHPA[J]. Journal of Materials Engineering, 2012, 0(3): 52-55.
Hydantoin epoxy resin was synthesized and hydantoin epoxy in presence of hexahydrophthalic anhydride (HHPA) as the curing agent was preparation. Hydantoin epoxy resin was substantiated by FTIR and 1H-NMR spectrum. Non-isothermal differential scanning calorimetry (DSC) was examined to follow the curing reaction of hydantoin epoxy/HHPA system. Epoxy equivalent of hydantoin epoxy resin is 164g equiv-1 and viscosity is 6.9Pa?s at 25℃ which the closed to diglycidyl ether of bisphenol F(CYDF-180). The DSC analyses showed that there are an exothermic reaction peak from 90℃ to 210℃ for the hydantoin epoxy/HHPA system and top of the peak is 152.5℃ at 10℃/min，which determined main reaction of hydantoin epoxy/HHPA system. The curing process temperatures such as gel temperature (Tgel)=93.7℃, curing temperature (Tp )=136.9℃ and post-curing temperature (Ttreat)=181.2℃ were acquired by extrapolation, which confirmed a lowering of the cure temperature of the hydantoin epoxy/HHPA system to avoid defect formation. Curing characterization of hydantoin epoxy resin is the similar with diglycidyl ether of bisphenol A. The hydantoin epoxy/HHPA cured resin was made and its properties were studied. Investigations show that the flexural strength is 122MPa, flexural modul is 2.8GPa, impact strength is 14.9kJ/m2，and limit oxygen index is 23 which indicates mechanical properties of hydantoin epoxy resin exceeds diglycidyl ether of bisphenol A. Therefore hydantoin epoxy resin can a candidate matrix for performance composite material manufacture and adhesive application in automobile industries, shipbuilding, aerospace, laminates and insulation material.
DAI Zhi-shuang, SHI Feng-hui, ZHANG Bao-yan, LI Min, ZHANG Zuo-guang. Study on the Surface Physical Characteristics of Carbon Fibers and the Effect on Wettability[J]. Journal of Materials Engineering, 2012, 0(3): 56-60.
Inverse gas chromatography was used to measure the surface area, solubility parameter and surface energy of T300B and desized T300B fiber, and the effect of surface physical characteristic on wettability between fibers and resin was investigated. A multiple of injection experiment with different concentration of hexane on fibers sample at 303K was carried out, and accordingly the surface areas of T300B and desized T300B were calculated as 0.43m2/g and 0.39m2/g, respectively, by BET method. Decane, nonane, octane and heptane were chosen as the neutral probes and toluene, dichloromethane, ethanol, 1,4-dioxane, acetone as polar probe, to determine the Flory-Huggins parameters (χ) between carbon fibers and probes. The solubility parameter (δ) of T300B and desized T300B was 11.98MPa1/2and 10.01MPa1/2respectively. The sizing could enhance the polar component of surface energy and the wetting ability of T300B fiber.
HAO Shi-ying, GAO Hui-lin, YAN Kai-juan, ZHANG Xiao-yong, JI Ling-kang, LI Wei-wei. Microstructure and Mechanical Properties of X80 Pipeline Steel with Excellent Deformability[J]. Journal of Materials Engineering, 2012, 0(3): 61-65.
By Heating On-line Partitioning (HOP) method to obtain (B+M/A ) dual phase, the microstructure and property of a dual phase pipeline steel are investigated. The results show that , in the context of meeting the strength and toughness requirements of the second west-east gas pipeline project in China, the （B+M/A） dual phase pipeline steel also possesses a lower yield/tensile ratio and higher uniform elongation, showing excellent deformation ability. The bainitic matrix, M/A component and the precipitation of carbonitride are the microstructure characteristics of experimental steel.
SONG Xiao-hui, GAO Wei, LUO Ning, YU Chang-zhen. The Determination of Impurity Elements Na, K, Mg and Ca in High Purity Silicasol by AAS[J]. Journal of Materials Engineering, 2012, 0(3): 66-69.
A method for the determination of impurity elements Na, K, Mg and Ca in high purity silicasol by FAAS has been developed. Under the optimum condition, the detection limits of Na, K, Mg and Ca are 0.0047，0.0060，0.0036，0.028μg/mL.The recovery were between 92.5%-112.5%,RSD were all less than 10%.The methods is accurate, rapid and convenient.
LI Jia-yan, GUO Su-xia, TAN Yi, LIU Chen-guang. Preparation of Porous Silicon and the Influence of Gettering on the Electrical Properties[J]. Journal of Materials Engineering, 2012, 0(3): 70-73.
Porous silicon gettering was an effective method for reducing impurities and defects in crystalline silicon and improving conversion efficiency of solar cell.Porous silicon layer was prepared on the surface of monocrystalline silicon by electrochemical etching. The characterizations of porous silicon layer were investigated and the effect on the porous silicon gettering of current density. Moreover, the gettering mechanism was supposed based on the microstructure of porous silicon. The result showed that the porosity increased significantly as the current density increasing and the maximum values are achieved for the current density 100mA/cm2. The porous silicon layer formation was accompanied by the appearance of elastic mechanical stress and the increasing of lattice parameters. The two factors were beneficial to the migration for defects and metallic impurities from the bulk to the PS layer. Therefore, the resistivity increased with the current density increasing.
GAO Yu-xin, ZHAO Cheng, YI Jian. Microstructure and Properties of Ni-Cr Alloyed Coating Prepared by Electrospark Deposition Processes[J]. Journal of Materials Engineering, 2012, 0(3): 74-78.
The Ni-Cr alloyed coating was produced on the surface of P20 steel plate with self-made electrode by electro-spark deposition (ESD) technique. The microstructures and properties of the coating were investigated. The results show that ESD process can produce big-thickness coating with proper process parameters, and the thickness is about 430μm. The coating is well bonded to the matrix and the interface between the coating and the substrate is presented as non-uniformly mixed mutuai melting crystallization. The superfine dendritic structure prevails in the middle and bottom of the coating and nano-structured grains in the upper coating. The hardness of the coating shows gradient distribution from the surface reached the largest to the substrate reduced sequentially. Nano-structured particles of the upper coating are the main factors leading to high hardness as well as corrosion and wear resistance of the coating.
WANG Xue-hua, CHEN Gui, CAI Peng, FU Ping, LI Cheng-yong, YANG Liang, CAO Hong. Magnetic Properties of FeCo Alloy Nanowire Arrays Synthesized by AC Electrodeposition in AAO Template[J]. Journal of Materials Engineering, 2012, 0(3): 79-82.
Anodic aluminum oxide (AAO) membranes with highly ordered pores were prepared by secondary anodic oxidation. By using alternating current (AC) electrochemical deposition，FeCo alloy nanowire arrays were fabricated in anodic aluminum oxide (AAO) membranes in different electrolytes with variable molar ratios of Fe2+/Co2+. The morphology, microstructure and magnetic properties of FeCo alloy nanowires were characterized by TEM, FE-SEM, XRD and VSM, respectively. The results indicate the FeCo nanowire arrays are uniform and regular, which corresponds to the diameter of the nanochannel of the AAO membrane, and the degree of pore filling rate is very high throughout the template. XRD and TEM results show that the crystal structure of FeCo alloy nanowires has ［110］ preferred orientation. VSM results show the FeCo nanowire arrays fabricated in different electrolytes has a strong perpenticular magnetic anisotropy, whose easy axis was parallel to the nanowires. The magnetic properties of FeCo nanowire arrays changed with their compositions, and the variation of coercivity and squareness of all samples was discussed in detail.
LIU Li-lai, YANG Pei-xia, AN Mao-zhong, ZHANG Yun-wang. Effect of Constituents of Electrolyte and Operating Condition on Micro-arc Oxidation Process of Mg Alloys[J]. Journal of Materials Engineering, 2012, 0(3): 83-88.
Magnesium alloys were treated with micro-arc oxidation in a solution containing NaAlO2 at a constant applied current density. The effect of concentration of NaAlO2, glycerol, NaF in electrolyte and current density and oxidation time on voltage-time response of micro-arc oxidation process and coating thickness was also investigated. The results showed that sparks could be seen at the anode surface when the electrolyte only contained NaAlO2, the addition of glycerol can obviously restrain point discharge, the addition of NaF increased the coating thickness considerably. With the increase of the current density, ignition time of micro-arc oxidation become shorter. While the break voltage had no obvious change, and coating thickness increased obviously. The surface morphology of micro-arc oxidation coating was observed by scanning electron microscopy (SEM). The results showed that obvious pores and discharged tunnels which were melting and combined together can be seen on the coating surface.
WANG Hai-ren, LI Yan, QU Jun-e, ZHENG En-xiu, CAO Zhi-yong, LI Wen-wei. Research on Judgment of Quality of Chemical Activation Pre-treatment for Coloring of Stainless Steel[J]. Journal of Materials Engineering, 2012, 0(3): 89-92.
The activation state of stainless steel was judged by the potential-time curve, and the effect of activation degree on the coloring process was investigated by anodic polarization and EIS (Electrochemical Impedance Spectroscopy) test. The results showed that when the stainless steel specimens were activated by immersed in a 5％ H2SO4 solution at 35℃,the potential decreased firstly ,and then reached stability gradually. The stainless steel specimens can reach a good and stable activation state after keeping the stable potential value for about 60s, which is positive for the repeatability of coloring. The coloring film showed better corrosion resistance for the completely activated samples.
LIU Pei-sheng, XIA Feng-jin, CUI Guang. Study on a Porous Titanium Dioxide Film Photocatalytic System with Micro-nano Pores Structure[J]. Journal of Materials Engineering, 2012, 0(3): 93-96.
A porous anatase TiO2 film with nano and sub-micro pores was fabricated by sol-gel method with ion implantation. A dense film was firstly fabricated by the conventional sol-gel method, which was then bombed by Fe ion with a certain kinetic energy to generate a great amount of micro-nano pores. These micro-nano pores significantly enlarge the specific surface area of the titanium dioxide film. The experimental results of photocatalytic decomposition of a methyl orange solution display that the porous film is better than the dense film for the photocatalysis both under ultraviolet light and under visible light.
