LIU Haiyan, SONG Weidong, NING Jianguo. Dynamic Behavior of Tungsten Alloys with Different Grain Sizes[J]. Journal of Materials Engineering, 2007, 0(6): 3-6.
Experimental Lagrangian analysis technique was adopted to investigate the dynamic behavior of 91W-6.3Ni-2.7Fe with three kinds grain sizes of 1-3μm,10-15μm and 30-40μm.The stress-time history curves at different Lagrangian positions were obtained for tungsten alloys at different impact velocities.Lagrangian analysis technique was used to discuss the mechanical properties of the tungsten alloys under high strain rate.The mechanical quantities at different Lagrangian positions,such as strain,specific volume,density,strain rate,specific internal energy and particle velocity were obtained.The influence of grain size on the dynamic behavior of tungsten alloys under high strain rate was analyzed and the stress-strain curves(104-105s-1) of the tungsten alloys were given.
WANG Baoshun, L Yizhong, CUI Yan, ZHAO Huiyou. Dry Sliding Tribological Behavior of SiCp/Al Composites Against Semi-metallic Brake Pad[J]. Journal of Materials Engineering, 2007, 0(6): 7-10,14.
The aluminum matrix composites reinforced with 15%(volume fraction,the same below),25%,35%,45%,55% of SiC particles(45,63μm) were prepared by pressureless infiltration process.The friction and wear behavior,under a load of 196N and at a constant sliding velocity of 0.42m·s-1,of the SiCp/Al composites and gray cast iron(HT250) were investigated using a block-on-ring test at room temperature under dry sliding against a semi-metallic brake pad.The results showed that the friction coefficient of the SiCp/Al composites significantly increased with improving the SiCp volume fraction,but the friction coefficient of the SiCp/Al composites was not significantly affected by the SiCp size.When the volume fraction of the particles improved from 15% to 55%,the friction coefficient of SiCp(45μm)/Al and SiCp(63μm)/Al increasing from 0.319,0.303 to 0.385,0.359,respectively.The stability of the friction coefficient of SiCp/Al composites was better than that of HT250.The wear rate of the HT250-brake pad tribo-pairs was 7.09×10-6cm3·m-1,2.2 times than the 55% SiCp(45μm)/Al-brake pad tribo-pairs and 2.7 times than the 55%SiCp(63μm)/Al-brake pad tribo-pairs.The composites-brake pad tribo-pairs had better wear resistance than the HT250-brake pad tribo-pairs.The wear rate of the SiCp/Al-brake pad tribo-pairs decreased with increasing the SiCp size.
HUANG Fengping, LI Hejun, LI Kezhi, HU Zhibiao, HUANG Lihai. Prefabrication of SiC Coating to Protect C/C Composites with Carbonizing Rice Hull[J]. Journal of Materials Engineering, 2007, 0(6): 11-14.
In order to protect carbon/carbon(C/C) composites from oxidation,a silicon carbide coating had been produced by carbonizing rice hull though pack cementation technique.The component and morphology of the coating were analyzed by XRD,SEM and EDS methods.The results revealed that the coating with net structure was mainly β-SiC crystals and a few α-SiC crystals.The SiC coating with net structure could be produced at low temperature was due to nanometer crystallite of SiO2 in the carbonizing rice hull.
CHEN Ting, ZHANG Guangcheng, LIU Tiemin, ZHANG Cui, SHI Xuetao. Study on Cellular Structure of Acrylonitrile/Methacylic Acid Copolymer Foam Plastic[J]. Journal of Materials Engineering, 2007, 0(6): 15-19,54.
Acrylonitrile(AN)/methacylic acid(MAA) copolymer foam plastic was prepared by free foaming.The change trend of average cellular diameter with the apparent density was discussed.The influence of nucleate agent and stress whitening on average cellular diameter was studied.The macroscopic and microscopic foam structure were observed by optical microscope and scanning electronic microscope.The results indicate that the average cellular diameter of AN/MAA copolymer foam plastic decreases with the increase of the density.Carbamide can be used as nucleate agent and minish the cellular dimension evidently.Stress whitening of foamable copolymer can increase the nucleation process during foaming and decrease the cellular diameter greatly.AN/MAA copolymer foam plastic has high obturator foramen ratio and isotropic.The side number of cell wall is between three and seven,and three cell walls intersected as cell arris.The volume occupied ratio of cell walls decreases with the increase of the density.
LIU Tiemin, ZHANG Guangcheng, LIANG Guozheng, CHEN Ting. Research on In-situ Cyclization Reactions During Preparation of High-performance MAA/AN/AM Copolymer Foam[J]. Journal of Materials Engineering, 2007, 0(6): 20-25,60.
A new high-performance foam plastic was prepared via MAA,AN and AM radical bulk polymerization,and the corresponding foaming and heat treatment.The important reaction mechanism of in-situ cyclization taking place in the course of the expandable copolymer foaming and heat treament was discussed,and then was validated via optical microscope,infrared adsorption spectrum(FTIR) and differential thermal analysis(DSC).The results reveal that there exist weak exothermic peak of 149.17℃ and strong endothermic peak of 270.85℃ in the DSC curves of MAA/AN/AM copolymer after foaming and heat treament(160℃/2h→200℃/2h).The peak temperature of DTG curve is 175.87℃,and the weightlessness rate is lesser at 276.58℃ in the TG curve.In the case of FTIR,—OH absorption peak at 930-970cm-1 and 1480cm-1 are weakened,and C—N absorption peak of imide is enhanced.>C=O absorption peak at 1700cm-1 happens excursion towards the low frequency field,and the second absorption peak enhances.—C≡N absorption peak at 2240cm-1 are weakened,while a new —C=N— absorption band appears.All these datum reveal that in-situ cyclization has taken place,and some rigid ringed structures appear in the copolymer molecule chains,for example,hexahydric imide rings and trapeziform structures.
JIN Xiaoou, HE Shiyu, XUE Wenbo. Fatigue Behavior of 3J21 Alloy at Different Aged States[J]. Journal of Materials Engineering, 2007, 0(6): 26-30,64.
The fatigue behavior of under-aged,peak-aged and over-aged 3J21 alloy were testly by using MTS testing machine.The macrographs and micrographs of fatigue fracture were analyzed by Scanning Electron Microscopy(SEM).The results show that the fatigue crack growth for different aged alloys is all transgranular.The fatigue crack initiation life of under-aged 3J21 alloy is the longest,the fatigue crack growth track is zigzag,the fatigue crack growth rate is the slowest;the fatigue crack growth resistance is maximal;the fatigue life is the longest.However;the fatigue crack initiation life for over-aged alloy is the shortest. The proportion of growing along intercrystalline for over-aged alloy gradually increases;Its crack track is straighter;The fatigue crack growth rate is the fastest,its fatigue crack growth resistance is the lowest.The fatigue life is the shortest.The fatigue behavior of peak-aged alloy is between that of the two aged state alloys.The fatigue fracture consists of fatigue source,fatigue crack growth area and instantaneously fractured area of different states.In low growing area,the fatigued fracture of under-aged shows small plane.The fatigue fracture of peak-aged and over-aged shows sugar candy pattern.In middle growth area,the long fatigue striations were not inspected except small individual fatigue striations.
FENG Yanqiu, PAN Tang, LI Li, YE Xiaoying. ICP-AES Determination of La,Ce in 23Co13Ni11Cr3Mo Steel[J]. Journal of Materials Engineering, 2007, 0(6): 31-34,38.
The determination method of La,Ce in 23Co13Ni11Cr3Mo steel by ICP-AES was studied.The spectral interferences of martrix and coexist elements were studied.And the analytical lines were determined.The limits of La 398.852nm was 0.0079μg/mL and Ce 418.660nm was 0.0089μg/mL.The rate of recovery is in the range of 99%-103%,The relatively standard deviation(RSD%) of results are less than 5% for Ce elements(≤0.005%) and for La elements(≤0.005%).The contrast result of the method and ICP-MS method was accordant,It has been proved that the method is accurate,simple and rapid.
ZHANG Mingyu, HUANG Qizhong, XIE Zhiyong, SU Zhean, WANG Xiufei, HUANG Boyun. Study on Densification and Microstructure of Multi-coupling Fields CVI[J]. Journal of Materials Engineering, 2007, 0(6): 35-38.
With propylene as carbon source,carbon felt as porous preform,C/C composites were rapid fabricated by multi-coupling fields CVI process.A series of experiments were designed for building relationship between fabrication parameters and material quality.Pyrocarbon microstructures were investigated with polarized optical microscope(PLM),SEM,XRD and Raman spectra.The results show the C/C composite with higher density,uniformity and microstructure is obtained under the condition of 650 ℃and 12kPa.It indicates higher pressure and lower temperature are favorable.Analysis for giant regenerative cones in samples was carried out.A new type of pyrocarbon was observed under the PLM which has highest graphitizability.It is called "Dot structure" with its rain drop appearance and its formation mechanism is supposed electromagnetic field absorption and hydrogen abstraction and carbonization og non-fully solidified viscosity.
L Zhenzhou, HAN Jianmin, LI Weijing, YANG Zhiyong, WANG Jinhua. Research on Real-time Temperature Measuring Method for Determining Heat Treatment Regulation[J]. Journal of Materials Engineering, 2007, 0(6): 39-42.
A case study of quenching and high temperature tempering of forged coupler yoke used to railway freight cars,the real-time temperature measuring method is utilized to measure the temperature in different places of furnace and coupler yoke in the course of heating and cooling treatment.Based on the results of analyzing the rule of temperature change and testing the sample’s microstructure and mechanical properties,the reasonable heat treatment regulation for mass production of forged coupler yoke is determined and the reliability and practicability of real-time temperature measuring method for determining heat treatment regulation are verified.
LIU Hua. Weld Cracking Analysis of the Pressure Vessel Cover[J]. Journal of Materials Engineering, 2007, 0(6): 43-45,49.
The welding line of the pressure vessel cover cracked in the process of pressure experimentation.By means of macro and micro observation on fracture surface,observation on microstucture,hardness test,oxygen and hydrogen content examination,the cause of weld cracking was analyzed.The results showed that the main cause of weld cracking of pressure vessel cover was that the argon protect in the process of welding cannot meet the request,which resulted in the formation of oxide layer and α layer on welding line inner surface.In addition,The welding line cracked in the process of pressure experiment because of high stress concentration and high residual stress in the juncture of the two welding lines.
HONG Xiaobin, XIE Kai, XIAO Jiayu. Novel Organic Silane Modifier for Epoxy Resin[J]. Journal of Materials Engineering, 2007, 0(6): 46-49.
Novel organic silane of 3,3′-dihydroxyldiphenoxydimethyl alkoxy silane and 3,3′,3″-trihydroxyldiphenoxydimethylalkoxy silane triglycidyl ether for epoxy resin modification were synthesized.Their influence on mechanical and thermal properties of crosslinked bisphenol F epoxy resin were studied.It was showed that the toughness of crosslinked bisphenol F epoxy resin were improved efficiently,the thermal expansion coefficient below Tg were reduced, the internal stress decreased and the crack resistance index improved.Bisphenol F epoxy resin modified by 3,3′,3″-trihydroxyldiphenoxydimethylalkoxy silane triglycidyl ether remain high Tg temperature.Meanwhile the mechanical properties improved,and viscosity of bisphenol eopoxy resin matrix decreased.
XU Guozhong, LI Hejun, BAI Ruicheng, CHEN Fuxiao, Huang Min. The Influence of the Precursors on Densification and Properties of C/C Composites[J]. Journal of Materials Engineering, 2007, 0(6): 50-54.
The influence of different precursors on the densification rate,microstructures and flexural strength of C/C composites,2-D needle punctured felt infiltrated by novel-ICVI,was investigated.The density of the resultant C/C composites was tested by volume method.The density distribution and the correlation between the density and the infiltration time were studied.The flexural strength was determined by three-point blending tests,and the microstructures of resultant materials and the morphology of fracture surface were observed by polarized light microscopy and scanning electron microscopy respectively.The result show that the densification rate of C/C composites using methane as precursors is lower than that using propylene as precursors before 100h infiltration,while after 100h infiltration the trend is reversed.The density of C/C composites tends to distribute uniformly,the flexural strength is 250.87MPa,the flexural modular is 29.29GPa,and the texture belongs to rough laminar when methane is used as precursor.The density of C/C composites distributes unevenly,the flexural strength is 102.75MPa,the flexural modular is 11.42GPa,and the texture belongs to smooth laminar when propylene is used as precursor.Therefore,the methane is an ideal precursor for novel-ICVI Process.
LI Bin, ZHANG Xiaoyun, TANG Zhihui, ZUO Xinzhang, YU Bo. Effect of Water-based Cleaning Compound for Aircraft Exterior Surface on Metals Corrosion and Hydrogen Embrittlement[J]. Journal of Materials Engineering, 2007, 0(6): 55-60.
Effect of AHC-1 and AHC-5 water-based cleaning compounds for aircraft exterior surface on the corrosion of aircraft typical metals and the hydrogen embrittlement for high strength steel was studied.The effectivity of controling hydrogen embrittlement by the inhibitor and the possibility of predicting hydrogen embrittlement through electrochemical polarization method were discussed.
ZHANG Rongfa, SHAN Dayong, CHEN Rongshi, HAN Enhou. Application of Micro-arc Oxidation in Improving Corrosion Resistance of Magnesium Alloys[J]. Journal of Materials Engineering, 2007, 0(6): 61-64.
A new process of micro-arc oxidation was developed and it could improve the corrosion resistance of magnesium alloys considerably according to potendynamic polarization curves and salt spray test.In addition,micro-arc anodization of wheels and motor parts were studied in the process in order to lay foundations for industrial use of the technology.Anodic coating is compact and uniform on the surface of samples after anodization.The colour of anodic coating is white and beautiful.
