KANG Yong-wang, QU Shi-yu, SONG Jin-xia, YUAN Hua, HAN Ya-fang. Microstructure and Properties of Nb-Ti-Si-Cr-Al-Hf Alloy Prepared by Electron Beam Melting[J]. Journal of Materials Engineering, 2009, 0(4): 1-5.
The Nb-Ti-Si-Cr-Al-Hf system alloy was prepared by electron beam melting method.The microstructure,hardness,room temperature fracture toughness and high temperature compressive behavior of the alloy were investigated.The results showed that the composition inhomogeneity at different region of the ingot was serious,which may attribute to the vapor pressure of the elements,and the higher cooling rate was benefit to the formation of small and uniform microstructures.The microhardness(HV) of Nb silicide was about 1100,which was three times of that of Nb solid solution.In addition,the room temperature fracture toughness(KQ) of the alloy was about 10.3MPa·m1/2.The compressive strength at 1250℃ of the Nb-Si in-situ composition was about 426.3MPa,and the alloy had good plastic deformation ability at high temperature.
ZHAO Shou-tian, WU Ping, CHEN Sen, ZHAO Xin, YUAN Shao-qiang, WANG Xue-min, YANG Shan-wu, HE Xin-lai. Segregation of Boron in Ultralow-carbon Micro-alloy Steels[J]. Journal of Materials Engineering, 2009, 0(4): 6-9.
By means of Particle Tracking Autoradiography(PTA),the segregation of boron to grain boundaries in ultralow-carbon micro-alloy steels during cooling from 1150℃ to 850℃ at 5℃/s was investigated.The enrichment factors and widths of boron depletion zone were measured at different temperatures,and the effect of copper on the segregation of boron was analyzed.The results show that the concentration of boron at the grain boundary increases and reaches its maximum at about 1000℃ at the beginning of the cooling;after that,it decreases gradually to a minimum with temperatures decreasing to 910℃;and then,it increases again.Experiments also indicate that the segregation of the boron could be enhanced via adding copper.
ZHAO Ping, YANG Zhi-guo, HE Qing-hua. Experiment Investigation for Creep Performance of DD3 Single Crystal Superalloy[J]. Journal of Materials Engineering, 2009, 0(4): 10-13.
The creep life,creep curves,fracture characteristic,microstructure at different creep stages and the width of rafts were analyzed under three different experiment conditions.The results showed that applied stress played an instinct influence on the creep life of DD3 single crystal superalloy under the condition of middle temperature,the increase of temperature or stress would promote the growth of microvoids and dimples at higher temperature and the creep rupture was characteristic of the convergence of microvoids,the creep process was the process of γ′directional coarsening,rafts forming and dissolution,the speed of rafts forming and the process of rafts dissolution had affected directly the creep life.
PANG Xiao-feng, ZENG Hong-juan. Investigations of Biological Activity of Nanohydroxyapatite Ceramic Powder[J]. Journal of Materials Engineering, 2009, 0(4): 14-17,22.
The nanohydroxyapatite ceramic powder was synthesised by using sol-gel method.The work parameters were controlled as pH>9,Ca/P=1.67,the sintered temperature and time were controlled at 1100℃ and 2 hours,respectively.A nanometer powder of hydroxyapatite with high purity were obtained.Its structure and biological activity absorbing the amino acid molecules were studied by ultraviolet absorption spectrum,X-Ray Diffraction(XRD)structure analysis,infrared spectrum and X-ray Diffraction Spectrum(XDS) of constitute analysis.The results showed that the nanohydroxyapatite can absorb these amino acid molecules,of which acted positions on the hydroxyapatite is the radical PO43-,instead of Ca2+.The mechanism of absorbing of the hydroxyapatite with amino acid molecules with different electric potentials was proposed.
SHEN Hua-long, WU Yun-xin, XIONG Wei-min. Choice of Dynamic Stress as Application of Vibratory Stress Relief in Aluminum Alloy[J]. Journal of Materials Engineering, 2009, 0(4): 18-22.
From the analysis of the mechanism of Vibratory Stress Relief(VSR),the influence factors and distribution situation of dynamic stress were analyzed,and the principle of choosing the magnitude of dynamic stress was presented,when it need to have a local plastic deformation without fatigue damage.Then the high intensity aluminum alloy thick-plates’VSR experiment was tested by means of suspension.The principle of choosing dynamic stress was set forth.
XIE Ke-lei, QU Chun-yan, MA Ying-jian, YANG Hai-dong. Effect of Cross-linking Agent to Structure and Properties of PMI Foams[J]. Journal of Materials Engineering, 2009, 0(4): 23-27,30.
The effect of crosslinking agent on the preparation of PMI foams was presented by selecting MgO and allyl methacrylate as crosslinking agent respectively.The results showed that the density of PMI foams was gradually improved,and the average cellular diameter decreased with the increase of the content of crosslinking agent.The heat resistance and mechanical properties including compression strength,shear strength,tensile strength and tensile modulus was also gradually improved while the breaking elongation firstly increased then decreased with the increase of the content of crosslinking agent.PMI foams used MgO as crosslinking agent showed higher tensile modulus and the PMI foams used allyl methacrylate as crosslinking agent exhibited higher density and breaking elongation.
LI Ai-lan, YU Qian, WANG Ye. Explanation for Aeronautical Standards of "Test Methods for Estimating Grain Size of Superalloy Investment Castings" and "Test Methods for Estimating Microshrinkage of Superalloy Investment Castings"[J]. Journal of Materials Engineering, 2009, 0(4): 28-30.
To improve the quality of superalloy castings,aeronautical standards of " test methods for estimating grain size of superalloy investment castings" and "test methods for estimating microshrinkage of superalloy investment castings" were compiled.The backgrounds of the standards,methods for sampling and key technical contents were illustrated for reference.
LUO Jian-lin, DUAN Zhong-dong, LI Hui. Effect of Nanoscale Silica Fume and Carbon Nanotube on Damping Capacity of Cement-based Composite[J]. Journal of Materials Engineering, 2009, 0(4): 31-34.
Nanoscale Ultrafine Silica Fume(USF) or/and Multi-Walled Carbon Nanotube(MWCNT) were incorporated into cement matrix to fabricate 3 groups nanocomposites,with associated the reference(Plain/C).The critical damping ratios(ζ) and flexural strengths(σ) of these composites were investigated with free attenuation method in an elastic system,half-power bandwidth technique and subsequently three-point bending testing method,respectively,to evaluate the effect of USF or/and MWCNT additives on the damping and mechanical properties of cement matrix.Relative to the reference,the infilling and pozzolan effect of USF additive has positive influence on the enhancement of the σ of matrix,yet somewhat negative effect on that of ζ.The dislocation,viscous deformation effects of hollow nanotubes render the nanocomposite good damping behavior,yet the formation of defect and porosity with bad dispersion of MWCNT may jeopardize the enhancement of the σ.There are dual positive effects on the ζ and σ of the nanocomposite when with combinatory incorporation of USF and MWCNT,microstructure reveals there exist good cross linkages between USF,MWCNT and cement matrix,and the enhancement amplitude of the ζ and σ can increase by 30.21%,24.13%,relative to the reference,respectively.
SHI Chang-liang, DONG Shi-yun, XU Bin-shi, HE Peng. Research on Metal Magnetic Memory Test in Process of Frictional Wear[J]. Journal of Materials Engineering, 2009, 0(4): 35-38,44.
Metal magnetic memory method was employed to detect 0.45%C steel samples in order to develop the variation law of magnetic signals in the process of frictional wear.The results showed that magnetic signals of the samples obviously changed before and after frictional wear tests.There existed abnormal magnetic peak in the wear district.By the analysis of the width and shape of the abnormal magnetic peak,the size of the wear district can be exactly known and the damage degree of the sample can be also qualitatively judged.Meanwhile,the experimental phenomena was explained by the theory of magnetic doublet model.
GAN Xue-ping. Influences of K4Fe(CN)6 on Electroless Copper Plating Using Hypophosphite as Reducing Agent[J]. Journal of Materials Engineering, 2009, 0(4): 39-44.
The influences of K4Fe(CN)6 on the deposit composition,resistivity,structure,morphology and the electrochemical reactions of hypophosphite(oxidation) and cupric ion(reduction) were investigated.The deposition rate and the resistivity of the copper deposits decreased significantly with the addition of K4Fe(CN)6 to the plating solution and the color of the deposits changed from dark-brown to copper-bright with improved uniformity.The content of P in the deposits also decreased slightly with the use of K4Fe(CN)6.Greater crystallite size and preferred orientation of(220) plane were obtained by the addition of K4Fe(CN)6 to the bath.The electrochemical current-voltage results show that K4Fe(CN)6 inhibited the catalytic oxidation of hypophosphite at the active nickel site by adsorption on the electrode.This results in lower deposition rate and a decrease in the mole ratio of NaH2PO2/CuSO4< consumed during plating.
LUO Lin, LIU Qian, QIU Ji. Fretting Wear Behavior of 7A52 Aluminum Alloy[J]. Journal of Materials Engineering, 2009, 0(4): 45-48.
The fretting wear behavior of 7A52 aluminum alloy was investigated with a micro-fretting wear tester.The effects of normal load,vibration amplitude and frequency on friction coefficient and wear volume were analyzed.Worn surface under different vibration amplitude was observed.Chemical composition of the worn scar and worn particles was analyzed by EDAX.Wear mechanisms of the fretting test was investigated.The results showed that larger vibration amplitude lead to abrupt rise of the friction coefficient in the initial stage of the fretting,while with lower vibration amplitude,no such phenomenon was observed.Wear volume increased with increasing vibration cycles,larger vibration amplitude and normal load.Under lower vibration amplitude,only abrasive wear was found,while under higher vibration amplitude adhesion occurred in addition to abrasion.With further increased vibration amplitude,contact fatigue wear was also observed.
ZHANG Ming, YU Wan-li, JIA Xiao-peng, MA Hong-an, HUANG Wan-xia, YUAN Qing-xi. Synchrotron Radiation Topographic Study of Crystal Defects in Synthetic Diamond[J]. Journal of Materials Engineering, 2009, 0(4): 49-51,56.
Crystal defects in a synthetic diamond were studied using continuous spectra synchrotron ra-diation.A seed crystal was observed in the specimen.It was found that a large amount of dislocations in the crystal was originated from the surface of the seed and ended at the surface of the crystal.The directions of the dislocations and the density of the dislocations were calculated.The growth course of the crystal and the main factors affecting the crystal defects were discussed.The defect density of syn-thetic diamond could be reduced effectively and the integrality of the synthetic diamond could be effec-tively enhanced if the defects on the surface of the seed could be reduced and the stabilization of growth condition could be kept.
ZHONG Yuan-hui, DAI Pin-qiang, DAI Chun-fu. Thermal Stability of Pulsed Electrodeposition Nanocrystalline Ni-Co Alloy Coating[J]. Journal of Materials Engineering, 2009, 0(4): 52-56.
Microstructures and composition of nanocrystalline Ni-Co alloy produced by pulse electrodeposition were studied by XRD and EDS.The microhardness of nanocrystalline Ni-Co alloy annealed at various temperatures was measured and the thermal stability of Ni-23.5%Co(mass fraction) alloy was studied extensively.The results indicated that microhardness of Ni-Co alloys increased slightly after annealing at low temperatures,and reached the maximum at 250℃,then decreased with the increasing of the annealing temperatures.The grain size of Ni-23.5%Co alloy increased from 13.5nm to 98.5nm when the annealing temperature rose to 300℃.The DSC curve obtained at 20 K·min-1 heating rate showed low energy exotherm beginning at 300℃ and continuing to 350℃ at which point the main thermal release occurred,reaching peak differential heat flow at 372℃,the release ΔH was 14.22J·g-1.According to the Kissinger equation,the activation energy for grain growth of Ni-23.5%Co alloy was calculated to be 212.5kJ/mol.
OU Bao-li. Surface-modification of Silica Nanoparticles by Carbon-carbon Double Bonds and Its Tribological Properties[J]. Journal of Materials Engineering, 2009, 0(4): 57-60.
Immobilization of carbon-carbon double bonds at silica nanoparticles surface was successfully achieved to gernerize reactable functionalized silica nanoparticles.The as-prepared samples were char-acterized by FTIR,TEM,wetting and dispersivity experiments.Friction reducing and anti-wear be-havior of the as-prepared functionalized silica used as additive in lubricant were evaluated on wear test-er.The results indicated that the functionalized silica nanoparticles can well dispersed in lubricant oil,which contributed to greatly improvement on anti-wear and friction reducing ability of gas mobile oil,and also can repair worn surface to a certain degree due to forming polymer films at rubbing surface.
WEI Jia-rui, TANG Ai-min, SUN Zhi-hua. Effects of Ultrasound Wave Pretreatment on Structure Changes of PPTA Fibers[J]. Journal of Materials Engineering, 2009, 0(4): 61-66.
The molecular mass,super-molecular and morphology structure of PPTA((Poly(p-Phenylene Terephthalamide)) fibers before and after ultrasound wave pretreatment was studied by means of viscometer,X-Ray Diffraction(XRD),optical microscopy and SEM.The influences of treatment time and power of ultrasound wave on structure changes of PPTA fibers were discussed at different structure level.The results show that the molecular mass of PPTA is reduced from 27,000 before treatment to 26,200 after 6min ultrasound wave treatment.The crystallinity and crystalline size of PPTA do not change greatly as well.The morphology structures of fibers have significantly changed and partial fibrillation can be observed by optical microscopy and SEM.The extent of fibrillation of fibers increases as the treatment time and power increase.As the molecular weight and crystallinity of PPTA fibers do not change notably and the morphology structures change obviously by ultrasound wave treatment,ultrasound wave can be used as a useful pretreatment way in the preparation of PPTA pulp.
HAN Jian, DAI Qi-xun, LI Gui-rong, CHEN Deng-bin, ZHAO Yu-tao, LIU Yu, CHEN Gang, CHENG Xiao-nong. Effect of Addition of Yttrium on As-cast Microstructure of 7055 Aluminum Alloy[J]. Journal of Materials Engineering, 2009, 0(4): 67-70.
The effects of addition of yttrium on as-cast microstructure of 7055 aluminum alloy were investigated using optical microscope,scanning electron microscope,X-ray diffraction,etc.The results showed that the as-cast microstructure of 7055 alloy was gradually fined when quantity of yttrium was under 0.25%(mass fraction).The grain size reduced from 100μm to 40μm was fined remarkably with addition of 0.25% yttrium,and the second phases of the 7055 alloy were sphericized and fined.However the as-cast microstructure of the alloy was observed gradually becoming coarse when the percentage of the yttrium increased to more than 0.25%.The Al6Cu6Y resulting from addition of yttrium to the 7055 alloy was distributed at the grain boundary.
LI Dong-hai, HU Ming, SUN Feng-yun, CHEN Peng, SUN Peng. Study on Fabrication of Porous Silicon Gas Sensor and Gas Sensing-characteristics[J]. Journal of Materials Engineering, 2009, 0(4): 71-74.
Double-cell electrochemical etching was used to prepare PS based on P+ type and the principle and advantages of porous silicon gas sensor were presented.The film morphology was characterized by SEM and AFM.The sensing-characteristic of PS films was studied in terms of different of porosities.The results show that the response/recovery time of PS thin films decreases with increasing the current density and the PS thin film reveals excellent sensitivity and response characteristics in the presence of low concentration of 0.1×10-5-6×10-5 NO2 gas in air.
ZHANG Hua, XU Jia-wen, WANG Ji-ming. Experimental Study of Hybrid Processing of Jet Electrochemical Machining and Laser Beam Machining on Nickel-based Superalloy[J]. Journal of Materials Engineering, 2009, 0(4): 75-80.
In order to solve the problem with recast layer produced during laser machining on nickel-based superalloy,a new processing of Jet Electrochemical Machining and Laser Beam Machining(JECM-LBM) was put forward.Based on the analysis of principle of JECM-LBM and the study on the properties of laser attenuation in electrolyte,the experimental system was made,and drilling experiments on a thin GH3044 sheet were done with the system.The results showed that recast layer had been reduced more than 90% during JECM-LBM with NaNO3 electrolyte of pressure 1.5MPa and concentration 18%,and that the hybrid processing was feasible with applied future for the film cooling holes of aero-engine blades.
