GAO Feng, ZHANG Chang-song, WANG Wei-min, ZHANG Hui-jun, TIAN Chang-sheng. Lattice Structure and Piezoelectric Properties of W6+ Doped PZN-PZT Ceramics[J]. Journal of Materials Engineering, 2005, 0(1): 3-7,11.
The effect of W6+ doped on lattice structure and piezoelectric properties of 0.2PZN-0.8PZT ceramics was investigated.The results show that the pure perovskite phase form in ceramics.The lattice constant is decreasing with increasing W6+ additive, also the ratio of c/a is decreasing with the addition of tungsten, which should be attributed to replacing B-section ions such as Zn2+,Nb5+,Ti4+ and Zr4+ by W6+.The additions of tungsten will increase dielectric constant ε and mechanical quality factor Qm, and decrease coercive e-lectric field Ec, spontaneous polarization Ps, the electromechanical coupling factor Kp and piezoelectric constant d33.The composition with 1.0% (mass fraction) of WO3 addition on 0.2PZN-0.8PZT ceramics has the excellent piezoelectric properties, d33 is 314pC/N, Kp is 0.62 with the high Qm amounted to 1178, which can meet the needs of high power piezoelectric devices.
FAN Zhen-xiang, CHENG Hai-feng, ZHANG Chang-rui, TANG Geng-ping, WANG Jun. Fabrication Process and Properties of Silicon Carbide Fiber Reinforced Si-O-C Composites Using Polysiloxane as Precursor[J]. Journal of Materials Engineering, 2005, 0(1): 8-11.
Silicon carbide fiber reinforced siliconoxycarbide(Si-O-C) composites were fabricated via precursor infiltration and pyrolysis using polysiloxane.The effect of absorbent contents on flexural strength,density, thermal expansion coefficient of SiCf/Si-O-C composites was studied.Absorbing wave properties were fairly excelent in low frequency,when measuring reflection rate of radar microwave absorbing materials.Microstructure and properties of SiCf/Si-O-C composites were discussed, the high properties were mainly attributed to ideal interface structure and density.
ZHANG Ke, NIU Yan, WU Wei-tao. High Temperature Corrosion of NiCr Alloys in Chlorination-oxidation Atmosphere[J]. Journal of Materials Engineering, 2005, 0(1): 12-15.
Corrosion behaviour of pure Ni and three NiCr alloys were studied in 5%O2-0.3%HC1-N2 (volume fraction) at 800℃.The results show that all of materials undergo accelerating corrosion and metal chlorides form at the interface of oxide scale/metal substrate.NiCr alloys suffered mass loss in initial stage of corrosion, which may be caused by sublimation of chromium of chlorides and oxychlo-rides.However, addition of Cr in NiCr alloys can improve their corrosion resistance in the mixed atmosphere.
CAI Jian-ming, ZHANG Wang-feng, LI Zhen-xi, MA Ji-min, CAO Chun-xiao. Characteristic and Control of Bright and Dark Striations in TC11 Titanium Alloy Blades[J]. Journal of Materials Engineering, 2005, 0(1): 16-19.
The characteristic of bright and dark striations in TC11 titanium alloy was analyzed.Meanwhile, the solution to decrease or eliminate the bright and dark striations was recommended.The results show that most of the bright striations are titanium-rich segregation or aluminum-rich segregation.In other instance, the bright striation may be interstitial elements richened segregation.The dark striations are the strain trace formed during forging of the blades or β phase stabilized elements richened segregation.The forming reason of the compositional segregations related bright and dark striations is mainly resulted from the melting process of the titanium alloy ingots.To decrease or eliminate the compositional segregation, raw materials selection, electrode preparation, melting process must be controlled properly, and the quality inspection must be done at some important procedures.The forging strain trace related dark striations can be decreased or eliminated by optimizing the practice parameters in forging and heat treatment procedures.
QI Xin-zhe, WEI Qi, LI Zhuo-xin, LIU Hai-xia. Microstructure and Properties of Al-based Coatings Prepared by Arc Spraying[J]. Journal of Materials Engineering, 2005, 0(1): 20-24,28.
Al-based coatings were prepared by Al-based cored wire and arc spraying.Their microstruc-ture and oxidation and corrosion resistance were also investigated.Al-based coatings were consisted of AlFe, AlFe3, Al2O3, AlFe0.25Ni0.77 and AlNi mainly; and after heat treatment for 1h at 800℃, high-aluminum new phases such as Al13Ni4, Al86Fe14, Al5FeNi appeared in the coatings, and they improved Al-based coatings hardness.Oxidation and corrosion resistance of Al-based coatings were better than that of Fe-based coatings, and oxidation resistance of Al-Fe-Ni-B coatings was close to that of 45CT, and corrosion resistance of Al-Ni-Cr coatings was nearly same as that of 45CT.
HUANG Zhi-rong, MA Liu-bao, LI Pei-ning. Pack Aluminization of HK40 Steel and Evaluation of Carburization Resistance[J]. Journal of Materials Engineering, 2005, 0(1): 25-28.
The pack aluminization of HK40 alloy and its carburization behavior were investigated using optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy dispersion analysis of X-ray(EDAX).The experimental results showed that the desired surface composition of aluminized layer can be obtained by adjusting the proportion of Al to special additive powder in the pack and process parameters such as treatment temperature, and that the deposition rate was increased by about 60% compared with the classical methods.The carburization resistance of aluminized layer of NiAl and Ni3Al obtained by the two-step process is apparently superior to that of the Ni2 A15 phase which is obtained by traditional process.
LI Jing-yong, ZHAO Yong, CHEN Hua-bin. Friction Stir Welding of TiB2 Particulate A356 Aluminum Alloy Composite[J]. Journal of Materials Engineering, 2005, 0(1): 29-32,36.
6.5% TiB2(volume fraction) particulate A356 aluminum alloy composite manufactured by in-situ reaction was successfully joined by friction stir welding (FSW), a kind of pure mechanical solid state joining process.In comparison with un-reinforced Al alloys, the weld quality of aluminum alloy composite is more impressible to FSW parameters.Aluminum alloy composite is welded at lower temperature by FSW process so that the reaction between reinforcement particles and matrix aluminum can be avoided.Meanwhile, because of the combining effect of stirring, colliding and rolling action of rotating pin and friction heat the grains of matrix and reinforcement particles in FSW weld region are partly broken and new recrystallization cores are formed, so the structure becomes smaller and reinforcement particles distribute more uniformly in weld.The hardness of weld region shows’less variation than base metal and the ultimate tensile strength of TMAZ is almost 20% improvement.The results show that FSW has obvious superiority in joining of aluminum alloy composite.
ZHANG Hua, LIN San-bao, WU Lin, FENG Ji-cai, NING Jin-xing. Fracture Mechanism of Friction Stir Welded AZ31 Magnesium Alloy[J]. Journal of Materials Engineering, 2005, 0(1): 33-36.
The mechanical properties on friction stir welded AZ31 magnesium alloy joint were studied.The tensile and fatigue testing results show that the strength of friction stir welded AZ31 magnesium alloy joint can reach to 92.9% of the base metal.The fracture location is on the thermal mechanical affected zone in the advancing side.This is because of the unequal stratum structure and the stress concentration on this zone.Obvious tearing crack and fiber tissue was observed by scanning electric microscopy.
FAN Xuan-hua, CAI Li-xun, HU Shao-quan, LI Cong. Study on Mechanical Behaviors and Low Cycle Fatigue Fracture Analysis of Zr-4 Alloy[J]. Journal of Materials Engineering, 2005, 0(1): 37-40.
A series of investigations on the normal mechanical behaviors of Zr-4 at room temperature and 400℃ elevated temperature were carried out.R-O (Ramberg-Osgood) monotonic constitutive models at the two different temperatures were given.The effects of temperature on elastic modulus and Poisson ratio of Zr-4 alloy, as well as the heat expansion coefficient, were investigated.Micro-structure SEM features were discussed systematically to the LCF (Low Cycle Fatigue) specimens according to the LCF experimental results at room and 400℃elevated temperature.The results show that the failure mode is a type of transgranular fracture accompanied-with some wavy fatigue striations and quadratic cracks.
KE Li-ming, XING Li, XU Wei-ping. Microstructure and Properties of Welding Joints for Cast Magnesium Alloy AZ81A[J]. Journal of Materials Engineering, 2005, 0(1): 41-44.
The experiment of friction stir welding (FSW) and tungsten inert gas (TIG) welding to cast magnesium alloy AZ81A was conducted.The suitability of the two welding processes was analyzed by observing the weld morphology, studying the microstructure and measuring the Vickers hardness profile of the joint.The result showed that the visual appearance and operability of FSW are superior to those of conventional fusion welding, and the joints of FSW had little weld distortion.The microstructure of the typical friction stir weld is a kind of a wrought structure and its nugget zone contained a fine recrystallized grain structure.Within heat affected zone (HAZ), there were partial re-crystallized grains.These recrystallized grains formed along with the original casting grain boundary.In the fusion welds, the microstructure in the weld zone was dominated by columnar grains, which were finer than that of base metal.The microstructure of the grain boundary in the fusion zone is an eutectic structure consisting of α-solid solution and Mg17Al12, and the hardening precipitation exist within the grains.There is a discontinuous eutectic on the grain boundary in the HAZ.
LUO Shou-jing, CHENG Yuan-sheng, DU Zhi-ming. Ceramic Matrix Composite Thixoforming in Pseudo-semi-solid and Its Application to Satellite Angle-frames[J]. Journal of Materials Engineering, 2005, 0(1): 45-49.
Ceramic matrix composite thixoforming process in pseudo-semi-solid state was proposed.The satellite angle frames with 30% (volume fraction) Alp/SiCp composite were prepared by the thixoforming in pseudo-semi-solid state.The feasibility of process was tested by the metallographic analysis and tensile test.The results showed that the microstructure was homogeneous and the hardness could reach 6.43GPa(HV).The strain was about 0.5%.The tensile strength was about 300MPa.
YAN Hai-yan, HU Zhi-yi, KOU Kai-chang, ZHENG Ban-long, ZHANG Jiao-qiang. Study on Conductivity and Spectra of Polyaniline Doped with Functional Sulfonic Acids[J]. Journal of Materials Engineering, 2005, 0(1): 50-52,57.
Polyaniline doped with 4-dodecyl benzenesulfonic acid(DBSA), sulfo-salicylic acid (SSA) and 4-methyl benzesulfonic acid (TSA) were synthesized and labeled as PANI/DBSA, PANI/SSA and PANI/TSA.Their conductivity were measured with the method of four-probe, and the influence of different functional acids on electric conductivity of polyaniline doped with them was studied.The FT-IR and UV-VIS spectra were analyzed.The result shows that the conductivity and the spectra of PA-NI doped with functional acids were effected by the counter-anion of the dopants.The counter-anion’s size of DBSA is bigger than that of SSA and TSA, and its conductivity, shifting of FT-IR and UV-VIS spectra were more stronger than the two others’.The reflectivity of NIR is the same as PANI/ DBSA >PANI/SSA> PANI/TSA.
WU Xiao-wen, ZHANG Wei-jia, ZHONG Li-zhi, HUANG Hao. Preparation of Ge1-xCx Thin Film and Its Infrared Properties[J]. Journal of Materials Engineering, 2005, 0(1): 53-57.
Ge1-xCx films were prepared by PECVD (Plasma Enhanced Chemical Vapor Deposition).The effects of processing parameters on carbon content and infrared optical properties of the films were studied.The results showed that carbon content in the films increased with the increased of gas flow radio CH4/GeH4.The infrared refractive index was various from 2 to 4.The deposition rate was increased with the increase of ratio frequency power,but it was almost invariable when the power was higher than 60W.The deposition rate was decreased with increased of the temperature.Ge1-xCx films were transparent in the band of long infrared wavelength.
CHENG Xiang-zhen, SONG Yong-cai, XIE Zheng-fang, XIAO Jia-yu, WANG Ying-de. Composition and Structure Characterization of Polycarbosilane Precursor Synthesized from Liquid Polysilane Under High Pressure[J]. Journal of Materials Engineering, 2005, 0(1): 58-60,64.
The polycarbosilane (PCS) precursor for SiC fiber was synthesized in an autoclave with liquid polysilane (LPS), which was obtained by thermal decomposition of polydimethylsilane (PDMS).The composition and structure of the PCS were characterized.The results showed that the PCS was the general term for organosilicon polymers with a Si-C backbond.The weight average molecular weight (Mw) of PCS was about 2861, and the polydispersity index, Mw/Mn (weight average to number average molecular weight), was about 1.92.Elemental analysis gave an empirical formula of SiC1.89H4.81O0.05.IR and NMR showed the presence of SiC4 and SiC3H structure units containing Si-CH3, Si-CH2-Si and Si-H groups.From the ratio of C-H and Si-H intensity areas in H-NMR spectra, the value of C-H /Si-H was about 9.83.From 29 Si-NMR spectra, the ratio of SiC3H to SiC4 units was about 0.48.The PCS synthesized under high pressure was better for precursor for SiC fiber than that of synthesized under normal pressure, because the PCS synthesized under high pressure had higher molecular weight and Si-H bond content.
QI Hai-bo, YAN Yong-nian, LIN Feng, ZHANG Ren-ji. SiCP/Al Composite Made by Electron Beam Rapid Manufacturing[J]. Journal of Materials Engineering, 2005, 0(1): 61-64.
The characteristics and technology of electron beam rapid manufacturing, which can be applied into the process SiCP/Al composite, are introduced.This new technology possesses not only the ability of adjusting the volume of reinforced particle at random as powder metallurgy, but also the a-bility of greatly improving the wet properties between particle and matrix as producing in vacuum environment.Electron beam rapid manufacturing has also succeeded the advantages of rapid manufacturing, such as no molds required, the casting problem avoided, little or no machining allowance.Therefore, the electron beam rapid manufacturing is a very effective technology of SiCP/Al composite produced.
