FAN Shi-tong, TANG Hai-bo, ZHANG Shu-quan, WANG Hua-ming. Finite Element Analysis of Factors to Thermal Stress in Gradient Composite with Orthogonal Method[J]. Journal of Materials Engineering, 2012, 0(8): 1-4.
In order to analysis the contributions of graded layer thickness, constituent phase volume fraction and aspect ratio to the being of thermal stress, physical models of gradient composite were established. The thermal stresses of the models induced by cooling to room temperature were simulated using finite element method, and the importance of the factors was mathematically estimated by orthogonal design method. The results show that, in the three factors, graded layer thickness has the most remarkable effect to thermal stress, and the influence of constituent phase volume fraction is obvious, but the effect of aspect ratio is not significant.
ZHANG Xiao-yan, WANG Jing-he, CHENG Xiao-yang, FAN Zhao-dong. Structure Design and Verification Test for Fragile Protection Closure Made from Epoxy-foam Plastics[J]. Journal of Materials Engineering, 2012, 0(8): 5-9.
The stress distribution of the fragile protection cover made from epoxy-foam plastics was analyzed under the given blast load by the method of the finite element simulation. And the strain distribution was tested under the safe load. So the two drafts of the structure were designed based on the results of the research on the destroy forms of the wing slip area of cover structure which was carried out according to the properties of the base material. The explosion experiments besides the static pressure and gas dynamic pressure were executed to the specimens. The results showed that the weakening groove laid along the structure in vertical, horizontal and edge lines contributed to root fracture and uniform segments at the critical pressure, and that the structure design was reasonable and the analysis method was accurate, which were proved to be the basis for the application of fragile protection cover.
LIU Xin-ling, PENG Kai, BAI Ming-yuan, YU Yang. Failure Analysis About Bourdon Spring of Electrohydraulic Servo Valve[J]. Journal of Materials Engineering, 2012, 0(8): 10-13.
The crack conditions of 13 bourdon springs of electrohydraulic servo valve were analyzed, including crack position, crack orientation and the crack regularity. Using the methods of macrography observation, fracture surface analysis and metallic phase analysis, the fracture characteristics and mechanism of bourdon springs were studied. The results showed that, main failure reasons included: larger stress, material quality and process. The inclusion distribute was axial because of hard-drawing, crack was formed following the inclusion during the process of circumferential dressing.
LI Bo, KANG Yong-lin, ZHU Guo-ming, GAO Yong-jian. Effects of Substrate Strength on Friction Coefficient of Galvannealed Auto Steel Sheets[J]. Journal of Materials Engineering, 2012, 0(8): 14-18.
Friction coefficient of galvannealed steel sheets under different contact pressure was studied by sliding test. The results show that,at the same deformation, the work-hardening of the low-strength substrate is stronger than that of high-strength substrate; the friction coefficient of the high-strength substrate galvannealed steel sheets is lower at the same contact pressure. Moreover, the friction coefficient of low-strength substrate galvanized steel sheets decreases from 0.154 to 0.136, and the friction coefficient of high-strength substrate galvanized steel sheets decreases from 0.140 to 0.135, when the contact pressure increases, but at the higher contact pressure, the decrease extent of friction coefficient is slow down. Furthermore, the effect of substrate strength on the friction coefficient using adhesion theory was investigated. The conclusions are as followings: friction coefficient is decided by α (mold and coating direct contact percentage of the total actual contact area) and substrate surface micro-hardness; α and substrate surface micro-hardness are mainly determined by substrate strength; the different substrate surface micro-hardness moves close to each other because of different work-hardening as the contact pressure increases, contributing to α equality, and finally the effect of substrate strength on friction coefficient of galvannealed steel sheets would be low.
ZHANG Zhi-xiang, ZHANG Zhi-chao, YE Qian-jin, SUN Li-yan, LIAN Shi-quan, HAO Bao-qian, ZHAO Qin-xin. Study of Dewpoint Corrosion of Coal-fired Boiler[J]. Journal of Materials Engineering, 2012, 0(8): 19-23.
Based on the new type of device, widely used ND steel, Corten steel and 316L steel, compared with 20G steel and 20# steel, dewpoint corrosion was tested on a 600MW power plant in Inner Mongolia Datang International Tuoketuo Power Generation Co.,Ltd. The temperature of inlet cycling water was 30-80℃ and the testing time was 72h. The scanning electron microscope (SEM) and energy dispersive spectrometer (EDS) were used to analyze the microstructure and the migration of the corrosive elements.The mechanism of dewpoint corrosion was revealed, and the relationship between the thickness of corrosion layer and temperature of inlet water was obtained. The results also showed that the order of corrosion resistance for the five materials was 316L>ND>Corten>20G>20#.
ZENG Wei-hua, LIU Hong-xi, WANG Chuan-qi, ZHANG Xiao-wei, JIANG Ye-hua. Effects of Technological Parameters on Microstructure and Corrosion Resistance of Laser Cladding Ni-based Coating on Stainless Steel Surface[J]. Journal of Materials Engineering, 2012, 0(8): 24-29.
A 6kW CO2 laser apparatus was used for cladding Ni25WC35 alloy powder on 1Cr18Ni9Ti stainless steel surface by different technological parameters to obtain single-pass cladding coating. The phase composition of cladding layer and effects of technological parameters on corrosion resistance of coating were studied. The results show that the coating mainly consists of(Fe,Ni)solid solution, W2C by WC in-situ reaction, and contains CrNiFeC,Cu3.8Ni compounds and some hard-phase such as FeW3C,Ni2Si,Fe3Ni3B. Optical microscope analysis results indicated that microstructure of cladding coating was homogeneous, dense, forming a good metallurgical bonding layer. Electrochemical corrosion measurements in 5.0%NaCl saturated solution results show that, with increasing laser power, the corrosion resistance presents a trend of decrease; with increasing scanning speed, the corrosion resistance presents firstly increasing, and then a trend of decrease. The maximum self-corrosion potential of cladding coating was -554.70mV, the lower corrosion current density was 0.55μA·cm-2. As a result, the process parameter of the best corrosion resistance was P=3.0kW and ν=500mm·min-1.
XU Xiao-jing, SHENG Xin-lan, ZHANG Ti-feng, LIU Min, XIN Xi-ling. Raman Spectrum and Friction Behaviors of Carbon-doped TiB2 Films Prepared by Magnetron Sputtering[J]. Journal of Materials Engineering, 2012, 0(8): 30-32,38.
The carbon-doped TiB2 (TiB2-C) film (SiC film and Ti film as interlayer) was successfully deposited on Cr12MoV steel substrate using magnetron sputtering technology. The carbon-doping effect on Raman spectrum, nano-indentation and friction behavior of TiB2 film was investigated. The results showed that higher or lower sputtering power of carbon can not lead to the doped-carbon presented in manner of DLC (diamond-like carbon). The doped-carbon decreased the nano-hardness and elastic modulus of TiB2 film. As sliding against steel balls (4mm in diameter) under room temperature and dry frictional condition, the doped carbon presented in manner of DLC can effectively decrease the friction coefficient of TiB2 film.
TAN Yi, SUN Shi-hai, DONG Wei, XING Qi-zhi, JI Ming. Research of Solid-liquid Interface Property During Directional Solidification Process for Multicrystalline Silicon[J]. Journal of Materials Engineering, 2012, 0(8): 33-38.
The silicon ingots prepared by vacuum melting furnace with different pulling rates were analyzed by the variation of macrostructure and minority carrier lifetime along solidified height and radial direction, and the solid-liquid interface property during directional solidification process was investigated. The results showed that the minority carrier lifetime increased with the increased solidified height at first, and reached its maximum, then decreased. The radial distribution of the minority carrier lifetime was considered to be corresponding to the solid-liquid interface. From the minority carrier lifetime distribution, the solid-liquid interface curvature decreased with the decreased pulling rate, and solid-liquid interface morphology is the cellular interface. The calculated effective segregation coefficient of Fe was over three magnitudes than the equilibrium segregation coefficient due to the existence of the cellular interface.
ZHAO Wen-xia, LI Ying, FAN Ying-wei, ZHENG Yun-rong. Fracture Analysis for Second Stage Rotor Turbine Blade in Aero-engine[J]. Journal of Materials Engineering, 2012, 0(8): 39-44.
The macro-structure, micro-morphology and micro-structure were detected by optical microscope, scanning electrical microscope and electrical probe micro-analyzer.The temperature range on different areas of turbine blade was deduced during.And the reason that caused blade fractured was discussed. The results show that,during the starting stage of engine, γ'phase dissolved or even turn out to be incipient melting caused by over-heat, liquefaction was found in parts of interdendritic and grain boundary, leading edge and trailing edge of blade overburned seriously where the temperature reached more than 1260℃, temperature of central area on the blade was around 1220℃ where away from leading edge about 6mm, temperature of area was under 1180℃ in short time where away from leading edge about 8mm. Overload state on blade caused by over-heat, and finally some of blade fractured instantly.
WANG Sheng-xue, LI Wei, CHEN Zhao-hui. Oxidation Behavior of ZrO2-doped Silicon Carbide Ceramics by Precursor Infiltration Pyrolysis Technique[J]. Journal of Materials Engineering, 2012, 0(8): 45-50.
ZrO2 modified silicon carbide(SiC) ceramics was fabricated with polycarbosilane,divinylbenzene and zirconium n-butoxide by precursor infiltration pyrolysis technique, and oxidation behavior was investigated by means of XRD,SEM and EDS. The results showed that after impregnation of ZrO2, the SiC ceramics began to be oxided at 1600℃, and bubbles appeared on the surface because of SiO2 oxidation resistant layer formed. When oxided at 1700℃, the ceramics showed severe oxidation,with serval pit at the surface and a certain mass loss; both of the surface and inner of the ceramics were oxided after oxidation at 1700℃,and the mostly component of the surface was SiO2,meanwhile,SiC in the inner was partly oxided to SiO2,both of the oxidation layers of the two ceramics were gradient; The transformation from the tetragonal phase to the monoclinic phase of ZrO2 happened at high temperature during oxidation, the existence of SiC can prevent this phase transformation while SiO2 can’t.
HU Zhi-qiang, HUANG De-feng, LIU Xian-qing, GAO Li, GAO Hong. Synthesis and Characterization of NiAl2O4 Nano-powders[J]. Journal of Materials Engineering, 2012, 0(8): 51-54,59.
NiAl2O4 nano-powders were synthesised by coprecipitation process of alcohol-aqueous, PEG6000 served as dispersant. The effects of the ratio of alchohol-aqueous on the grain size of powders and the PEG6000 on dispersion characteritics of NiAl2O4 nano-powders were investigated by XRD, TEM analysis, and FT-IR spectrum. The results indicate that the optimal ratio of alcohol-aqueous is 1∶1, in this case the grain size of the powders tend to minimum. By adding the PEG6000 in the deposition process, the reunion of precursor particles and the powder in roasting process can be avoided obviously. And then, the dispersion of the powder was improved significantly. Therefore, after adopting the NiAl2O4 nano-powders to the TiO2 film of dye-sensitized solar cells, the photoelectric conversion efficiency of the battery increases efficiently.
ZHANG Yong-bo, FU Hui-min. Failure Mode Research on CCF300 and T300 Carbon Fiber Composites Subjected to Short-beam Shear Load[J]. Journal of Materials Engineering, 2012, 0(8): 55-59.
The short-beam shear test was conducted on the CCF300 and T300 carbon fiber composite laminate under the condition of 23℃ dry, 23℃ wet,130℃ dry and 130℃ wet. The macroshape conjunctions with the SEM image were employed for the analysis and comparison on the shear failure mode and damage mechanism of these two kinds of carbon fiber composite. The results show that the interface strength is the most important property affecting the shear strength and failure mode of carbon fiber composite. However, CCF300 carbon fiber composite shows lower property on the interface strength. Therefore, if the CCF300 carbon fiber composite want to get more widely application on the structures, it need to improve its interface strength, especially the strength that under the condition of high temperature and wet.
CUI Chun-juan, ZHANG Jun, WU Kun, ZOU De-ning, LIU Lin, FU Heng-zhi. Influence of Solidification Rate on Solid-liquid Interface of Si-Ta Alloy[J]. Journal of Materials Engineering, 2012, 0(8): 60-64.
The influence of solidification rate on the solid-liquid interface of Si-Ta alloy was studied by the zero power method. The results show that the solid-liquid interface morphology has the following evolution processing: planar interface→shallow cell interface→cell interface→shallow cell interface→planar interface when the solidification rate varies from 0.3mm/min to 9.0mm/min. At the lower solidification rates, the experiment results can be consistent with Jackson-Hunt theory well. However, there is a deviation between the theory calculation and the experiment at the higher solidification rates. This is caused by the change of the thermodynamics and kinetics, and the solid-liquid interface can get to planar interface at the solidification rate V=5.0mm/min.
DAI Bin, ZHU Hai-kui, ZHOU Hong-qing, WU Lu-yan, YUE Zhen-xing. Study on Properties of CaO-B2O3-SiO2 Glass Ceramics Contained Alkali Ions[J]. Journal of Materials Engineering, 2012, 0(8): 65-68,72.
The influence of the alkali oxide on soften temperature, crystallization temperature, sintering and dielectric properties of CaO-B2O3-SiO2 (CBS) glass ceramic was investigated. The results show that the soften temperatures of the CBS glass contained double alkali oxide additions increase and the crystallization temperatures decrease, as the alkali ionic radius rises. Na2O and K2O additions can improve the sintering properties of CBS samples better and microstructures of the samples are all dense and homogeneous. CBS samples are mainly composed of crystalline phases of CaSiO3, CaB2O4 and quartz. The dielectric constant and loss decline with the enhancing frequency. As the measure temperature rises, the dielectric constant increases slightly and the dielectric loss decreases.
LIU Jian, ZHANG Yong-zhen, DU San-ming, LIU Jing-chao. Study on Friction Characteristics of PTFE Braided Composites[J]. Journal of Materials Engineering, 2012, 0(8): 69-72.
The dry friction tests of PTFE braided composites were carried out on high-speed tribo-tester with speed, load as variables.The influence of different speed, load on the friction coefficient were analyzed. The results show that friction coefficient is stable reducing trend and finally stabilized with increasing load. Friction coefficient with the speed of change trend is: between 10-20kN, with increasing of the frequency, friction coefficient gets a minimum value and then rises to a steady value. The influence of the load on the friction coefficient is greater than that of frequency on the friction coefficient. Through the analysis of the microstructure of the liner using scanning electron microscope, the influences mechanism of speed, load on the friction coefficient was explained.
LI Xue-qin, ZHOU Yu-jing, ZHANG Zi-long, LIU Gang, YI Xiao-su. Curing Shrinkage Monitoring in Epoxy Resin by Fiber Bragg Grating Sensors[J]. Journal of Materials Engineering, 2012, 0(8): 73-77.
Temperature profile and the build-up of strains throughout the curing process were in-suit monitored by fiber Bragg grating (FBG) sensors embedded into an epoxy sample. The volume change of the resin was free due to the experimental set. The coefficients of thermal expansion of full-cured resin in cooling stage were also calculated from FBG’s measurement data. The results showed that FBG sensors could detect process-induced strains resulting from the volume change of the resin from the gel point until the end of curing. The coefficients of thermal expansion of full-cured resin in cooling stage determined by FBG sensors are comparable to the result of dilatometry. It is sensitive and reliable to determine curing shrinkage of thermoset resin using FBG sensors.
QIN You-qiong, YU Zhi-shui. Effects of Brazing Parameters on Microstructures of C/C Composite/Cu/Mo/TC4 Brazed Joints[J]. Journal of Materials Engineering, 2012, 0(8): 78-82.
C/C composite and TC4 were brazed using TiZrNiCu filler metal and Cu/Mo composite interlayers at 820-940℃ for 1-30min. The interfacial microstructures were investigated by scanning electron microscopy and electron energy spectrum analysis. The results showed that the sequence of the interface structure at low brazing parameters can be described as the following: Cu/Cu51Zr14/Ti2(Cu,Ni)+Ti(Cu,Ni)+TiCu+Cu2TiZr/TiC/C/C composite. With the increased brazing parameter, TiCu and Cu2TiZr disappeared, and Ti(Cu,Ni)2 appeared. The interface structure was changed to Cu/Cu51Zr14/Ti2(Cu,Ni)+Ti(Cu,Ni)+Ti(Cu,Ni)2/TiC/C/C composite. For high brazing parameters, the interface structure was composed of Cu/Cu51Zr14/Cu(s.s)+Ti(Cu,Ni)2/TiC/C/C composite. The thickness of Cu51Zr14 and TiC reaction layers increased with the increased brazing temperature and the prolonged holding time.
LIU Xiao-li, LU Hai-jun, XING Li-ying. Study on Micro-morphology and Structure Control of Bismaleimide Foams[J]. Journal of Materials Engineering, 2012, 0(8): 83-87.
Bismaleimide(BMI) foams were prepared using azodicarbonamide (AC) as the foaming agent. Micro-morphology of the foams were analyzed by scanning electron microscopy (SEM) and the foaming process and foamed structure such as cell size, cell density, expansion ratio etc. were also studied. The results showed that the modified BMI foam was a kind of closed-cell foam and its cell shape was pentagonal dodecahedron. The foamed structure can be controlled by foaming viscosity, temperature and foaming agent content. When the viscosity of foaming mixture was enhanced, foam density, cell nucleation density (N0) and cell density (Nf) increased, the cell diameter was decreased and become uniformed. The foam density was reduced with increased AC content, and it increased when AC content was over 7%. With the elevated foaming temperature, the cell size increased and the foaming stability became worse.
ZHOU Yuan, XIONG Hua-ping, MAO Wei, CHEN Bo, YE Lei. Microstructures and Property of Diffusion Bonded Joints Between TiAl Alloy and Two Kinds of Superalloys[J]. Journal of Materials Engineering, 2012, 0(8): 88-91,100.
Joining TiAl alloy and superalloy was carried out by diffusion bonding with and without interlayer.There existed many holes in the TiAl/GH2036 joint under the diffusion bonding condition of 1000℃/20MPa/1h, and the average shear strength of joint at room temperature was only 16MPa. Using Ti-Zr-Cu-Ni alloy as the interlayer, liquid-phase diffusion bonding between TiAl and GH3536 was investigated at 935℃ holding 10min and 1h under the pressure of 3MPa. The joints diffusion boned under the two conditions were composed by multiple phases, such as Ti3Al and NiTi. As a result of the reaction between the interlayer and two base metals, two reaction layers with a certain thickness appeared in the both interface respectively. Sound joint was obtained under the diffusion bonding condition of 935℃/3MPa/1h, and the interlayer alloy exhibited strong cohesion with TiAl and GH3536. The corresponding shear strength of joint reached 125MPa.
QI Huan. Review of INCONEL 718 Alloy: Its History, Properties, Processing and Developing Substitutes[J]. Journal of Materials Engineering, 2012, 0(8): 92-100.
Since its invention and initial application in gas turbine components in the early 60’s of 20th century at INCO Huntington Alloys (now called Special Metals Co.), INCONEL 718 alloy (IN718) has become the most widely used nickel based superalloy in the aircraft engine industry. It was used in many critical aircraft engine components, accounting for over 30% of the total finished component mass of a modern aircraft engine. This article reviews IN718 alloy development history, its mechanical properties, long-term thermal stabilities, industrial processing methods, and current developing substitute alloys for enhanced thermal stability.
