XIONG Hua-ping, MAO Jian-ying, CHEN Bing-qing, WANG Qun, WU Shi-biao, LI Xiao-hong. Research Advances on the Welding and Joining Technologies of Light-mass High-temperature Structural Materials in Aerospace Field[J]. Journal of Materials Engineering, 2013, 0(10): 1-12.
Ti-Al system intermetallics and high-temperature ceramics or ceramic matrix composites, are the two kinds of light-mass heat-resistance structural materials with high potential in aerospace applications. According to the published literatures, the research advances on their welding and joining technologies, including the material weldabilities, joint properties with different welding processes and material combinations, and the progresses of studies on the application of the welding and joining technologies were reviewed, and some comments are made on the reporting advances especially in the past two decades. It is pointed out that, development of new high-temperature-tolerance welding consumables or brazing alloys, joining of dissimilar materials, and study on joint assessment and engineering application would be mainly important research areas in future.
REN Guo-cheng, ZHAO Guo-qun. Homogeneous Deformation Analysis and Microstructure Properties Study of AZ31 Magnesium Alloy in Multi-pass Equal Channel Angular Pressing[J]. Journal of Materials Engineering, 2013, 0(10): 13-19.
Equal channel angular pressing (ECAP) is an interesting method for changing microstructure and producing ultra fine grained (UFG) materials through super-plastic deformation. The homogeneous deformation is the main factor that influences the material performance during ECAP. Four processing routes are analyzed in detail by using finite element method with spatial switching method through rotating three-dimensional model in multi-pass pressing. The accumulated effective strain distribution of the work-piece processed by ECAP for four pressing routes are obtained respectively through finite element simulation. The processing route that can generate more homogeneous effective's main distribution in sample after four routes processing is defined. The mechanical property of AZ31 magnesium alloy processed by multi ECAP passes in different routes was analyzed through microstructure observation and mechanical tensile test at room temperature. The experimental results show that the fine and uniform microstructure can be acquired by appropriate deformation route, the mechanical property of AZ31 magnesium alloy is greatly improved when strain accumulation uniform after ECAP processing.
YANG Ji-nian, XU Ai-qin, CHENG Guo-jun, YU Xiu-hua. Fabrication and Properties of PLA Composites Toughened by SBS[J]. Journal of Materials Engineering, 2013, 0(10): 20-23.
The composites of poly (lactic acid) (PLA) toughened by styrene-butadiene block copolymer (SBS) were prepared via molten blending and compression molding. The effects of SBS contents were investigated on the morphologies, mechanical and thermal properties of composites. The results show that typical droplet-matrix morphologies of SBS/PLA composites were observed with well dispersed SBS particles in matrix and fine interfacial adhesion between SBS and PLA. The tensile strength and elastic modulus were decreased, however, the elongation at break and impact toughness of SBS/PLA composites were constantly increased with increasing SBS mass fraction within the range of research. The heat stability of SBS/PLA composites was greatly improved by the introduction of SBS with the evidence of thermo-decomposing temperature shifting to high temperature zone obviously.
SHEN Shui-fa, LIU Yu-hong, LI Ling, PAN Hai-bo. Preparation and Characterization of Mesoporous ZnFe2O4 with Superstructure of Stacking Strings of Bead[J]. Journal of Materials Engineering, 2013, 0(10): 24-28.
Mesoporous ZnFe2O4 was successfully synthesized through the reaction of Zn2+, Fe2+ and C2O42- using sodium dodecyl sulfate (SDS) as size-controlling reagent. The characterizations were done by X-ray powder diffraction (XRD), differential thermal analysis-thermo gravimetric analysis (DTA-TG), fourier transform-infrared spectroscopy (FT-IR), field emission scanning electronic microscopy (FE-SEM), nitrogen adsorption-desorption measurement, showing that mesoporous ZnFe2O4 can be obtained after calcined at 500℃ with Fe2+:SDS (mol)=10:1, its surface area is 82.0m2·g-1, BJH average diameter is 12.5nm, pore volume is 0.257cm3·g-1, and the mesoporous ZnFe2O4 has superstructure of stacking strings of bead.
WANG Hong-tao, CHEN Xiao, JI Gang-chang, BAI Xiao-bo, DONG Zeng-xiang, YI Deng-liang. Microstructure and Performance of Cold Sprayed WC-Co Coatings[J]. Journal of Materials Engineering, 2013, 0(10): 29-35.
Three kinds of WC-Co coatings were prepared by cold spraying (CS) of nanometer WC-17Co, WC-23Co and micrometer WC-12Co powders. The microstructure and phase structure were analyzed by scanning electron microscope (SEM) and X-ray diffraction (XRD). The microhardness, elastic modulus and fracture toughness of three kinds of the cold sprayed WC-Co coatings were investigated using microharder tester based on indentation toughness measurements and the wear performance of three coatings were tested on a pin on disk tester. It was revealed that three cold sprayed WC-Co coatings have dense microstructure and similar phase structure with that of feedstock powder. The allotropic transformation of metal Co occurred due to its intensive plastic deformation. The coatings have no lamellar structure characteristics of conventional thermal spraying coating and the WC hard phase in the coatings flow and redistribute in local area. Moreover, the microhardenss and elastic modulus of coatings decrease and fracture toughness increase with increasing binder phase content. Compared to 316L stainless steel, the cold sprayed WC-Co coatings exhibit excellent wear resistance and the wear mechanism is mainly the micro-cuts effect of abrasive particle on the coating surface.
LEI Yi-wen, SUN Rong-lu, TANG Ying. Thermodynamic Calculation on Precipitated Phase in Laser Clad Ni Base Alloy Coating on TC4 Alloy[J]. Journal of Materials Engineering, 2013, 0(10): 36-40,47.
Laser clad Ni base alloy coatings are fabricated on TC4 alloy using CW CO2 laser. The microstructures, precipitated phases and the partitioning characteristics of the main elements in γ-Ni and M23C6 phases of the coatings were examined. Results show that the coating can be divided into three regions: the cladding zone, the bonding zone and the heat-affected zone of the substrate. The cladding zone consists of γ-Ni, TiB2, TiC, M23C6 and Ni3B phases. The fine particles of TiB2, TiC and M23C6 are distributed in the primary γ-Ni and the eutectics consist of γ-Ni and Ni3B. The precipitated phases in Ni base alloy coatings were calculated using Thermo-Calc software with related database. To illustrate the evolutional rule of the precipitated phases and microstructure of Ni matrix coatings on TC4 substrate in the temperature range from 3500K to 500K, the effect of temperature on the amount of the precipitated phases and the partitioning characteristics of the main elements (B, C, Cr, Fe, Ni and Ti) in γ-Ni and M23C6 phases were studied. It could provide the theoretical basis to optimize of the processing parameters and design the constituent of laser clad Ni matrix coatings on TC4 substrate.
ZHANG Xin-ming, YU Cui-juan, LIU Sheng-dan, LIU Xing-xing, ZHANG Pan, WANG Ying-ying. Influence of Fe and Si Impurities on the Quench Sensitivity of Al-Zn-Mg-Cu Alloy[J]. Journal of Materials Engineering, 2013, 0(10): 41-47.
The influence of Fe and Si impurities was investigated quenching by means of end-quenching tests, and microstructure analysis including optical microscopy (OM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Results show that the addition of Fe and Si impurities leads to lower quench sensitivity, decreasing by 3.29% in maximum when characterize by hardness. With increasing the content of Fe and Si impurities, Al7Cu2Fe phase and Mg2Si phase content increased significantly, thus reducing the solutes concentration of Cu and Mg elements in the matrix, reducing the degree of supersaturation, which leads to lower quench sensitivity. Al7Cu2Fe phases and Mg2Si phases are favorable for recrystallization, but bad for the reducing quench sensitivity. This is attributed to the higher amount of the recrystallization grains and (sub)grain boundaries, which result in more heterogeneous precipitation of η equilibrium phases during slow quenching. The influence of supersaturation on quench sensitivity is bigger than that of grain structures.
WANG Yong, ZHOU Xin-yuan, SONG Zhan-yong, HUANG Yan-fei, ZHANG Wei. Tribological Property of Fe-based Coating Sprayed by Different Thermal Spraying Technologies[J]. Journal of Materials Engineering, 2013, 0(10): 48-52.
The Fe-based coatings were prepared by high velocity arc spraying technology(HVAS), high efficiency plasma spraying technology (HEPS), and detonation gas spray(DGS).Residual stress distribution and width at half height were measured by X-ray diffraction diffractometer. The microstructure and wear properties of the coatings were investigated by nano-tester and CETR wear tester.Results showed that the relationship of residual compress stress and wear properties of the coating is linear. The coating prepared by DGS has high hardness and excellent wear resistance. The main reason is that the DGS coatings have compress stress, high nano-hardness and compact structure. The fine structure and increment of distortion lattice of coating surface can improve wear resistance.
YUAN Song-dong, XIONG Kun, HU Kun-peng, ZHANG Yun-hua, LUO Yi, JIANG Guo-dong. Preparation and Properties of h-BN Porous Material with High Specific Surface Area by Adding NH4Cl[J]. Journal of Materials Engineering, 2013, 0(10): 53-56.
The precursor C3N6H6·2H3BO3 was prepared by wet chemistry method by using H3BO3 and C3N6H6, which are cheap and available as raw material, and NH4Cl as additive. Boron nitride with high specific surface area was prepared by pyrolysing the precursor under high temperature in N2 atmosphere. The product was characterized by XRD, FTIR, SEM, TEM, BET. The results showed that the product is mainly porous hexagonal BN belt, which specific surface area was 456.68m2/g, average pore size was 3.8303nm and pore volume was 0.4373cm3/g.
YOU Guo-qiang, WANG Xiang-jie, QI Dong-liang, GUO Qiang, LONG Si-yuan. Effect of Line Energy on the Microstructure and Properties of GTAW Welded Hot Extruded AZ91D Magnesium Alloy Joints[J]. Journal of Materials Engineering, 2013, 0(10): 57-63,70.
The influence of line energy on the microstructures, microhardness and ultimate tensile strength (UTS) of gas tungsten arc welded (GTAW) hot extruded AZ91D magnesium alloy plates were investigated by microstructural observations, quantitative analysis of grain size, microhardness tests and tensile tests. The results show that the weld prone to emerge defects such as incomplete penetration and porosity if the line energy is too low, and the grains both in the fusion zone (FZ) and the heat-affected zone (HAZ) increased with an increase of the line energy. Moreover, an increase of the line energy result in transition of low melting eutectic products from continuous shape to particulate shape in both the FZ and the HAZ. The microhardness and ultimate tensile strength (UTS) of the welded joint increased with an increase of the heat input, however, an over high line energy results in a decrease both for the microhardness and the ultimate tensile strength of the welded joint. When the line energy increases to a certain amount, the effects of grain size (Hall-Page effect), evaporation of zinc and over aging on the properties of metallic materials are greater than that of dispersion strengthened (Orowan strengthening mechanism), and the H-P effect is of the dominant on the material properties.
ZHANG Jia-min, YI Jian-hong, GAN Guo-you, YAN Ji-kang, DU Jing-hong, LIU Yi-chun. Process and Microstructure of Titanium Alloy Prepared by Sintering TiH2 Powder[J]. Journal of Materials Engineering, 2013, 0(10): 64-70.
The titanium hydride was directly used as the raw material through component mixing, compaction and sintering to manufacture the titanium alloy. The particle size and morphology of TiH2 change with the milling process and the microstructure of CP-Ti and Ti-6Al-4V alloy were observed using scanning electron microscope. The dehydrogenation characteristics of TiH2 powder was studied using thermal gravimetric analysis. The thermal expansion technique was used to evaluate the sintering densification characteristics of compacts of TiH2 and TiH2-Al-V powder. The results show that the particle size of TiH2 powder after ball milling is reduced rapidly with ball milling time adding and the powder morphology change gradually from the original irregular to be the equiaxed. The compacts of TiH2 powders is easy to sintering densification due to the combination of dehydrogenation and shrinkage of α-Ti in the process, which creates the fresh dehydrogenation titanium uniform during sintering, thus leads to rapid densification and very high sintering relative density, higher than 99%. In contrast, it is difficult to achieve a full densification of TiH2-Al-V alloy powder during sintering process, which requires dissolution of alloy elements. The microstructure of sintered sample of TiH2 powders compacts appears typical pure titanium with equiaxed.The microstructure of TiH2-Al-V alloy shows the typical lamellar like α+β characteristics with a uniform distribution of alloy element.
ZUO Wei-wen, HUANG Hua-li, SHI Lei, YANG Yang, WU Ran, ZHU Song. Preparation and Research of Organic-inorganic Hybrid Coating on the Surface of Denture Base Resins[J]. Journal of Materials Engineering, 2013, 0(10): 71-75.
An organic-inorganic hybrid coating was constructed on the surface of the denture base resins. The hybrid silica sol was prepared by co-hydrolysis and co-condensation of γ-glycidyloxypropyl trimethoxysilane (KH560) and tetraethyl orthosilicate (TEOS). The copolymer was prepared by co-polymerization of glycidyl methacrylate (GMA), acrylic acid (AA) and methyl methacrylic acid (MMA). The hybrid coating with inter penetrating network structure could be formed through the formation of cross-linking of the epoxy groups on the polymer chain and silica sol. The values of hardness, adhesion and resistance to rupture of the coating were tested. The values of water sorption, water solubility and glossiness of the denture base resins covered with coating were also measured. The experiments results revealed that the hybrid coating possesses good mechanical properties. Besides, the coating could increase the glossiness and decrease the water sorption, water solubility of the denture base resins, ultimately improve the comprehensive properties of the denture base resins.
XU Bo, JIA Ming-chun. Influencing Factors and Mechanism of Deoxygenization with Modified Sponge Iron[J]. Journal of Materials Engineering, 2013, 0(10): 76-79,102.
Kinetics, SEM, EDS and surface analyses were applied to evaluate the deoxygenization mechanism and the effects of factors on the deoxygenization behaviors. The results show that the copper content on the modified sponge iron has more effects than the specific area of modified sponge iron on deoxygenization performance. The deoxygenization by modified sponge iron is described as a first order reaction and is reaction controlled. In addition, the reaction rate constant decrease following an increase with initial pH value or initial conductivity increasing. The increase in modified sponge iron dosage or solution temperature can improve the reaction rate constant. However, the reaction rate constant is unable to be infinite for the increase in modified sponge iron dosage, and the limiting value of rate constant is 0.3663min-1.
JI Jian-min, CHEN Jin-long, GUO Guang-ping, CHEN Xin-wen, WANG Xiang. Measurement of Elastic Constants for Aviation Composite Materials Using Digital Image Correlation Method[J]. Journal of Materials Engineering, 2013, 0(10): 80-85.
The elastic constants for three kinds of aviation composite materials were measured using digital image correlation method (DICM) and the feasibility of DICM measuring elastic constants for aviation composite materials detailedly was studied. By theoretical analysis of DICM and proposing measuring method according to ASTM, the strain measurement precision could reach 25με. It meets the test requirement of aviation composite materials. The elastic constants for three different composite materials were measured by DICM and strain gauge method simultaneously, the results of the two methods are consistent. It demonstrates that DICM can measure the strain of aviation composite materials accurately.
ZHANG Xiao-yun, MEI Ke-li, XIONG Wen-hua, GUO Meng-qiu, GAO Jian. SCC Evaluation on Welding Samples of 7A52 Aluminum Alloy[J]. Journal of Materials Engineering, 2013, 0(10): 86-92,97.
The susceptibility of welding samples of 7A52 aluminum alloy to stress corrosion cracking (SCC) was evaluated using the slow strain rate test (SSRT) and direct tension stress corrosion test. The microstructure was also investigated after the SCC test. The results show low susceptibility to SCC of welding joint by 5A56 welding wire, metal inertia gas (MIG) procedure welded from both side. It is also possible SCC at high level stress and high temperature. The SEM indicated there are pores in welding part. High SCC sensitivity was expressed in high temperature or stress level. Secondary cracking existed on the fracture surface, large size secondary cracking increases obviously with the higher of stress level.
MAO Li, WU Hua-qiang, ZHANG Ning, LI Ming-ming, LI Ting-ting, XIA Ling-ling. Microwave-assisted Synthesis and Magnetic Properties of Composition-controlled Cu1-xNix/MWCNT Nanocomposites[J]. Journal of Materials Engineering, 2013, 0(10): 93-97.
Composition-controlled Cu1-xNix/MWCNT nanocomposites (x=0.5, 0.6, 0.8) were prepared by microwave-assisted method without using additional protective agents. The structure and morphology of the as-prepared nanocomposites were characterized by XRD, TEM, SEM, EDX and FT-IR spectroscopy. The magnetic properties were measured by VSM. The results show that Cu1-xNix alloy nanoparticles are face-centered cubic structure, quasi-spherical and disperse uniformly on the surface of MWCNTs. Both the lattice parameter and the size of Cu1-xNix alloy nanoparticles decreased with increasing Ni content. The saturation magnetization (Ms) of Cu1-xNix/MWCNT nanocomposites increases whereas the coercivity (Hc) decreases with increasing Ni content. Moreover, a possible mechanism of formation was discussed.
WU Feng-qiu, ZHANG Bao-fa. Influence of Surface Hardness on Oxidation Resistance of C/C Composite[J]. Journal of Materials Engineering, 2013, 0(10): 98-102.
The used carbon-carbon (C/C) composite softened on surface to different levels due to oxidation. The surface Shore hardness (HS) and oxidation resistance of the used C/C composite samples after anti-oxidation treatment were measured. The results show that the samples with the hardness of HS70 increased to HS80 after recoating, and the mass loss ratios were 0.44%/15h and 1.2%/22h after oxidized at 700℃ in air. The surface layer within 1mm was softener than the substrate for the oxidized C/C composite sample with the hardness of HS40, and the hardness increased from HS40 to HS60 with a mass loss ratios of 3.93%/15h and 6.52%/22h at 700℃ in air after recoating.
