ZHANG Lin-wei, WANG Lu, WANG Quan-sheng, NING Xian-jin. Effect of Vacuum Pre-oxidation on Oxidation Behavior of NiCoCrAlY Coating Prepared by Cold Spray[J]. Journal of Materials Engineering, 2014, 0(1): 1-5,29.
A NiCoCrAlY coating was prepared by cold spray. After deposition, the pre-oxidation of the coating was performed by vacuum heat treatment. The microstructure and phase structure of the coating were characterized by XRD, SEM and EDS. The effect of vacuum heat treatment on the oxidation behavior of NiCoCrAlY coatings at 1050℃ was also studied. The results show that the as-sprayed coating presents a dense structure with low porosity (less than 0.36%) and low oxygen content (0.25% mass fraction). Vacuum heat treatment converts the single-phase (γ) as-sprayed coating to a two-phase γ/β microstructure, and a continuous, uniform and dense α-Al2O3 layer is formed, with an average thickness of 0.47μm. After oxidation for 200h at 1050℃, a dense and continuous thermally grown oxide(TGO), mainly composed of α-Al2O3, is formed on the surface of as-sprayed and vacuum heat-treated coating. Vacuum heat treatment can postpone the formation of spinel in a certain time (100h) and decrease the growth rate of TGO.
WU Xing-ping, SHI Jin-gang, WU Hao, CHEN Ming-hai, LIU Ning, LI Qing-wen. Preparation and Mechanical Properties of SiC Particulate-reinforced ADC12 Aluminum Matrix Composite by Vacuum Stir Casting[J]. Journal of Materials Engineering, 2014, 0(1): 6-11.
SiC/Cu composite powders were adopted to fabricate SiC particulate-reinforced ADC12 aluminum alloy matrix composite by vacuum stir casting technique, and the influence of preparation process on the mechanical properties of composite was investigated and optimized. The composites were characterized by X-ray diffractometry (XRD) and scanning electron microscopy (SEM).The results show that dispersity and wetting ability of SiC particles in molten aluminum alloy matrix are significantly improved by SiC/Cu composite powders. At the condition of T=580℃, t=30min, and SiC content (w=4%), the composite attains the best mechanical properties. Its tensile strength and hardness reach 283MPa and HB133, respectively, which are improved by 24.1% and 77.3%, compared with ADC12 alloy matrix. It also shows obvious increase by 15.5% in tensile strength and 26.7% in hardness, respectively, compared to the composite with only bare SiC addition.
CHENG Xiu, HU Shu-bing, SONG Wu-lin, LI Zhen. Surface Strengthening Treatment of Nodular Cast Iron by Plasma Beam[J]. Journal of Materials Engineering, 2014, 0(1): 12-18.
The surface of nodular cast iron was strengthened by means of surface melting and alloying with plasma beam. The microstructures and the phase structures were analysed with SEM and XRD. The corrosion resistance and wear properties as well as microhardness were tested by hardness tester and wear tester. The results show that the near-surface graphite of the nodule disappears completely and there are mainly dendrites and eutectics in the modified layers after surface treatment of nodular cast iron by plasma beam. The highest microhardness in the melted layer and alloyed layer, appearing in the subsurface, are 1243HV0.1 and 1343HV0.1, respectively. The corrosion resistance and wear resistance of the melted layer and alloyed layer are enhanced remarkably comparing with the matrix. Furthermore, the corrosion resistance and wear resistance of the alloyed layer are better than that of the melted layer due to more hard phases, finer and more homogeneous structures in the alloyed layer.
ZHOU Yi-qun, TONG Wen-wei, LIU Fang, ZHANG Kai-kuo. Effects of Thermal Barrier Coatings on High Temperature Low Cycle Fatigue Behavior of K417G Alloy[J]. Journal of Materials Engineering, 2014, 0(1): 19-23.
High temperature low cycle fatigue(LCF) behavior of K417G alloy with thermal barrier coatings(TBCs) at 800℃ was investigated under fully reversed total strain-controlled mode. The individual strain fatigue parameters were gained by the analysis of strain-fatigue life and cyclic stress-strain data. The results indicate that the LCF of K417G alloy and K417G alloy with TBCs are stress fatigue, and the primary damage of LCF processing is elastic damage. K417G alloy with TBCs exhibits a longer LCF life than the K417G alloy, especially with higher strain. The SEM observations show that TBCs have little influence on the initiation of LCF cracks of K417G alloy. The LCF cracks initiate predominantly on the surface of specimens or at near surface defects, and the LCF specimens exhibit transgranular propagation.
GE Yong, WANG Tao, LI Lei. Effect of Injection Molding Parameters on Residual Stress of Polycarbonate[J]. Journal of Materials Engineering, 2014, 0(1): 24-29.
The influences of injection molding parameters on the residual stress of polycarbonate specimens were investigated by using orthogonal method. The results show that the most significant factor is melt temperature followed by cooling time and mold temperature, and the injection pressure has less influence. Because of the rapid relaxation of molecule chain, the residual stress decreases with increasing the melt temperature. The residual stress which decreases gradually along the flow direction is concentrated and high around the gate. The different injection molding processes take little influence on the distribution of the residual stress.
YU Qiu-jing, ZHANG Wei-hong, YU Lian-xu, LIU Fang, SUN Wen-ru, HU Zhuang-qi. Development of Thermal Processing Map and Analysis of Hot Deformation Mechanism of Cast Alloy Inconel 625[J]. Journal of Materials Engineering, 2014, 0(1): 30-34.
Gleeble 3800 testing machine was used to conduct a series of compression tests of cast alloy Inconel 625. Then thermal processing map was developed based on dynamic material model (DMM), which was used to analyze the hot deformation mechanism with the combination of true stress-true strain curve and microstructure. The results show that, for cast alloy 625, 1273-1363K, 0.1-5.05s-1 is the dynamic recovery(DRV) domain, 1363-1453K, 0.1-5.05s-1 is the partly dynamic recrystallization(DRX) domain and 1400-1453K, 5.05-10s-1 is the completely dynamic recrystallization domain. When it is deformed at 0.1-10s-1, the critical temperature of DRX is between 1373K and 1423K and the critical strain is between 0.4 and 0.6. The conditions without flow instability are 1400-1453K, 5.05-10s-1.
ZHAO Long-zhi, JIAO Yu, ZHAO Ming-juan, ZHANG Jian, HU Yong, XIONG Guang-yao, JIANG Xian. Effect of Holding Time on Mechanical Properties of Al-Fe-Si/Al In -situ Composites[J]. Journal of Materials Engineering, 2014, 0(1): 35-40,46.
Al-Fe-Si/Al in -situ composite was prepared by using powder metallurgy transient liquid phase sintering method. The influence of holding time on microstructure and mechanical property of Al-Fe-Si/Al in -situ composites was investigated by means of X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The results show that the grain size of in -situ synthesized Al0.5FeSi0.5 increases and the pore size of materials surface decreases when prolonging the holding time. The granular and short-rod reinforced phases get a diffuse distribution on the substrate when the holding time is 4h. With holding time, the compressive strength, the maximum bending flexibility and the bending strength have a trend of rising first then falling. Moreover, the interface bond in the composites is enhanced. However, the holding time has no influence on the composite elastic deformation and plastic deformation.
HUANG Yuan-chun, SONG Man-xin, XIAO Zheng-bing, ZHANG Yun-ya. Influence of Grain Refiner on Corrosion Properties of Aluminium Substrate Presensitized Plate[J]. Journal of Materials Engineering, 2014, 0(1): 41-46.
By using electrochemical workstations, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and other means,the effects of two kinds of grain refiners, Al-5Ti-1B and Al-5Ti-0.2C, on microstructures and properties of 1050 aluminum presensitized plate were investigated. The results show that there are numerous coarse second-phase particles containing Fe and Si in the cast-rolling board added Al-5Ti-1B. There are second phase particles and tangled dislocations in presensitized plate, which result in strong local corrosion and ununiformity of corrosion holes. However, in the cast-rolling board added Al-5Ti-0.2C,the second-phase particles containing Fe and Si, are relatively smaller and more uniform, without aggregation. The second-phase particles in presensitized plate are in small dispersion and uniform distribution, which lead to the acceleration of electrochemical corrosion and more uniform corrosion. For the plate added Al-5Ti-0.2C, the properties of electrolytic corrosion were improved.
WANG Bo, LI Song-mei, LIU Jian-hua, YU Mei, AN Jun-wei. Ultrasonication-assisted Green Synthesis of Graphene by Nickel Powder Reduction[J]. Journal of Materials Engineering, 2014, 0(1): 47-51.
A new method was presented to effectively reduce graphite oxide to graphene with nickel powder at room temperature. The reduced graphite oxide was characterized by X-ray diffraction analysis (XRD),Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, scanning electron microscope (SEM) and transmission electron microscope (TEM). The results show that the oxygen functionalities of the graphite oxide were mostly removed,and the intensity ratio (ID/IG) of D band to G band of reduced GO (rGO) is about 1.34. When the mass ratio of Ni and GO is 2, the effect of reduction is relative ideal. This method offers a feasibility for low-cost,effective,environmentally friendly and large-scale production of graphene.
GENG Bo, ZHANG Lu, FAN Nian-qing, XIA Zhi-xin, LIU Jiang-nan. Effect of Water Vapor Temperature and Flow on Oxidation Behavior of T91 Heat Resisting Steel[J]. Journal of Materials Engineering, 2014, 0(1): 52-57.
The effects of water vapor temperature and flow on oxidation behavior of T91 heat resisting steel was studied to reveal the relation between oxidation kinetics and scale structure. The results indicate that oxidation processes are divided into linear stage of rapid oxidation, parabolic stage of slow oxidation and linear stage of slow oxidation. Linear stage of slow oxidation takes place at the high temperature and small flow of water vapor. Oxidation rate increases with increasing vapor temperature in the fast oxidation of T91 steel. However, the effects of flow on the fast oxidation are not evident. The maximum of mass gain shows a linear increase with increasing flow, and the high vapor temperature accelerates this trend. The morphology change of outer layer causes the rapid decreasing of high temperature oxidation resistance with increasing the temperature and the flow of the water vapor.
LI Peng, ZHAO Kun-yu, GUO Jun, ZHANG Xiao-juan, DAI Dan, HUANG Feng. Factors and Mechanism for Transition of TiO2 from Nanopores to Nanotubes[J]. Journal of Materials Engineering, 2014, 0(1): 58-63,74.
Dense Ti films with uniform surface were deposited on glass pieces by using medium frequency pulsed magnetron sputtering method.The Ti films were subsequently anodized in NH4F/ethylene glycerol+H2O electrolytes.The results show that under a constant anodization voltage of 30V, increasing the concentration of NH4F from 0.5% (mass fraction) to 1% makes the formed TiO2 layers gradually change from a nanoporous to a nanotubular structure. And at a low concentration of NH4F (less than 0.75%), the same change is not observed with increasing the anodization voltage.
SHEN Chuang-shi, HAN Xiao-ping, GUO Zhang-xin, WANG Bin. Progressive Failure Simulation of Composite Laminates Stitched Around a Circular Hole[J]. Journal of Materials Engineering, 2014, 0(1): 64-69.
A new damage model was developed to simulate progressive damage behavior of the stitching reinforced composite laminates stitched around a circular hole. The damage at the edge of the hole was investigated for different stitching parameters, different layer design and axial tensile. The failure load for different stitching parameters was estimated by using the model and the calculated values show good agreement with the measured values. It is shown that the effects of the damage extend are extremely evident with the layer design for different stitching parameters. There exists an obvious postponement effect in the damage of the composite laminates after stitching reinforcement, especially the case of the double stitching reinforcement is more notable.
ZHENG Shu-kai, WU Guo-hao, ZHANG Jun-ying, WANG Fang, ZHAO Rui, LIU Su-ping, LIU Lei. Energy Band Structure and Photocatalytic Activity of Sn-doped TiO2 Thin Film[J]. Journal of Materials Engineering, 2014, 0(1): 70-74.
TiO2 thin films were successfully deposited onto microscope glass substrates by using RF sputtering technology. Then Sn ions were implanted into the TiO2 thin film with ion implantation method. The photocatalytic activities of the Sn-doped and un-doped TiO2 thin films under visible light were evaluated by the photodegradation of methylene blue dye solution. The results indicate that the photocatalytic activity of the Sn-doped anatase TiO2 thin film is enhanced under the visible light irradiation. The energy band structures of the Sn-doped and un-doped TiO2 were calculated by the first-principle based on density functional theory (DFT). The Sn doping takes slight effect on the band structure of TiO2, whereas doping energy level is formed by Sn 5s orbit near the bottom of the TiO2 valence band.
LI Wen-long, XIA Chun, XING Li, KE Li-ming. Influence of Pin Shape on Homogeneity of CNTs Distribution in CNTs/Al Composite Fabricated by Friction Stir Processing[J]. Journal of Materials Engineering, 2014, 0(1): 75-78,84.
A series of CNTs/Al composites were fabricated with friction stir processing(FSP) to investigate the effects of pin shape on the homogeneity of CNTs distribution in the composites. The results show that the paths and degree of the plasticized material flow are influenced by the pin shape, resulting in the variation of the macrographs of composites and homogeneity of CNTs distribution. Compared with cylindrical pin, a higher temperature of the metal around the conical pin promotes the formation of extruded zone more easily, and the effect of suction-extrusion on the plastic materials around pin is stronger. Therefore, the area of the central zone is expanded and the homogeneity of CNTs distribution in this zone is improved. Since double material flow paths are formed in the thickness direction of the plate and the extrusion zones are overlapped during friction stir processing, the mixing extent of the materials fabricated by the double threaded cylindrical pin is enhanced, resulting in homogeneous distribution of CNTs within the central zone.
ZHANG Xuan, ZHONG Yan-li, YAN Yue, LI Lei. Nanomechanical and Nanotribological Properties of Scratch-resistant Coatings on Polycarbonate[J]. Journal of Materials Engineering, 2014, 0(1): 79-84.
Two kinds of transparent scratch-resistant coating with different silica sol contents were synthesized,and their nanomechanical and nanotribological properties from the surface to bulk regions were investigated. The results show that the improvements of the mechanical properties are ascribed to the performance of nanosilica sol and the increased Si-O-Si inorganic bonds. Meanwhile, the hardness,modulus and friction-resistance of coatings in the bulk region are lower than that of surface region.
WANG Kai, YAN Zhi-feng, WANG Wen-xian, ZHANG Hong-xia, PEI Fei-fei. Temperature Evolution and Fatigue Properties Prediction for High Cycle Fatigue of Magnesium Alloy Under Alternate Loading[J]. Journal of Materials Engineering, 2014, 0(1): 85-89.
High-cycle fatigue damage process of AZ31B magnesium alloy at room temperature was studied based on thermographic technology. An infrared-thermography camera was used to investigate the temperature evolution on the surface of material during fatigue experiments. Results show that the temperature evolution mainly undergoes five stages under fatigue loading: an initial increase, steep reduces, steady-state, an abrupt increase and final drop (stage Ⅴ). Theoretical model combining the thermoelastic, inelastic, and heat-transfer effects will be formulated to explain the temperature profiles observed during fatigue. The relative error of fatigue limits between the experimental result (108MPa) and the predicted result (113MPa) is 4.8%. ΔTmax-N curve was proposed to predict the fatigue life based on the temperature evolution during the fatigue experiments. The fatigue fracture and the fatigue life will be predicted by maximum temperature rise of first stage.
PEI Li-zhai, YANG Yong, YANG Lian-jin, PEI Yin-qiang, XIE Yi-kang, CAI Zheng-yu. Synthesis and Application of One-dimensional Germanate Nanomaterials[J]. Journal of Materials Engineering, 2014, 0(1): 90-96.
One-dimensional germanate nanomaterials exhibit excellent potential applications in the fields of photocatalysis, nanoscale optical devices, nanoscale electron devices and sensors, owing to their good photocatalysis, sensing, electrical and optical properties. The recent research and development were reviewed on the synthesis, properties and application of the one-dimensional germanate nanomaterials. Especially, the development on the synthesis of germanate nanowires, nanorods and nanobelts by thermal evaporation, hydrothermal method and chemical vapor deposition, and the applications for the magnetic devices, electrochemical sensors, photocatalysis and lithium ion batteries were discussed. Finally, the possible development direction of the one-dimensional germanate nanomaterials was introduced.
