LU Jie, LIÜ Bo-cao, ZHANG Li-tong. The Effect of Seeds on the Microstructure and Mechanical Properties of Selfreinforced Si3N4 with La2O3Y2O3[J]. Journal of Materials Engineering, 2000, 0(4): 3-5,10.
The effect of seeds on the microstructure and mechanical properties of selfreinforced Si3N4 with La2O3Y2O3 was investigated. The results show that with the adding of seeds, large elongated β-Si3N4 grains increased. The higher the seeds content, the larger the area ratio of large elongated grains, the coarser the microstructure. The fracture toughness of self-reinforced Si3N4 could be improved without affecting the strength, producing a microstructure having coarse elongated β-Si3N4 grains distributed without contact each other by adjusting the content of seeds. It is also shown that, the bridging caused by coarse columnar grains is the predominant mechanism. The improvement of fracture toughness could be related quantitatively with diameter and area ratio of columnar β-Si3N4 grains.
CAI Xun, YANG Xiao-yu, CHEN Qiu-long, BU Xiao-mei. Microstructure of Laser Surface Melting (LSM) Layers on Cast AlSi Alloy[J]. Journal of Materials Engineering, 2000, 0(4): 6-10.
Laser surface melting (LSM) modified layers on cast Al-Si alloy were obtained using a CO2 continuous transverse flow laser beam with maximum power of 10kW. The microstructure of LSM modified layers were studied by using optical microscope, scanning electron microscope(SEM) and energy dispersive spectroscope(EDS), transmission electron microscope(TEM) and X-ray diffraction (XRD).It is shown that LSM modified layer could be divided in cellular, dendritic and mixed crystal zones The grain size of LSM modified layers became much finer than that of substrate material. The results of X-ray diffraction(XRD) and selected area diffraction(SAD) analysis indicated that much more silicon atoms were saturated in crystalline cells of α-Al phase through LSM processing. Microhardness distribution from surface to substrate on cross section plane was also tested. The average microhardness of LSM modified layers were in the range from 116 to 203HV, and wear resistance was enhanced greatly. Generally, improvement of mechanical property was due to the effects of fine-grained microstructure and oversaturated α-Al crystalline in LSM modified layers.
LI Ge-yang, NAKAE H, HANE T, DAI Jia-wei. The Improvement of Wettability of Al2O3 by Molten Aluminum[J]. Journal of Materials Engineering, 2000, 0(4): 11-13.
It is difficult for Al2O3/aluminum composites with excellent properties to be fabricated due to nonwetting of Al2O3 by molten aluminum. In this paper, the wettability of Al2O3 by molten aluminum and Al-La alloy was measured with an improved sessile drop technique and the interface between AlLa alloy and Al2O3 was analyzed with electron prober. The experiment results show Al2O3 is wetted by molten aluminum when rare earth element La is added in. The wetting angle decreases from 905° to about 80° This phenomenon results from La2O3 produced in the interf ace by reaction of La and Al2O3.
OUYANG Liu-zhang, LUO Cheng-ping, SUI Xian-dong, LUO Zhuo-xuan. The Influence of Al2(SO4)3 in Manufacture of Aluminum Matrix Composites[J]. Journal of Materials Engineering, 2000, 0(4): 14-15,44.
In situ Al2O3 decomposed from Al2(SO4)3 reinforced aluminum matrix composites was fabricated through stirring cast by adding Al2(SO4)3 to the molten alloy. SO3 decomposed from Al2(SO4)3 may refine and remove the gas from the molten composites by the way stated before.The results show that Al2O3 and matrix bond well, no cast defects being found,such as gas hole, porosity and particles segregation in in situ Al2O3 decomposed from Al2(SO4)3 reinforced aluminum matrix composites.
CAO Hai-lin, HUANG Yu-dong, ZHANG Zhi-qian, LIU Li-xun. The Effect of Anodic Oxidation Treatment on Interfacial Properties of Composites[J]. Journal of Materials Engineering, 2000, 0(4): 16-18.
Anodic oxidation treatment method was used to modify the surface of carbon fibers. The chemical composition of carbon fibers surface, the tensile strength of filaments and the interlaminar shear strength (ILSS) were studied respectively. The results indicate the number of polar functional groups on the carbon fiber surface and the ILSS of the composites are increased, and the tensile strength of filaments is decreased in a certain scope. Meanwhile the mechanism of the anodic oxidation treatment to improve the interfacial property of composites is obtained by analyzing the results.
DING Min, ZENG Fei, PAN Feng. Phase Evolution in Fe-Zr Multilayers by Ion Beam Assisted Deposition[J]. Journal of Materials Engineering, 2000, 0(4): 19-21,48.
The phase evolution in Fe/Zr multilayers by ion beam assisted deposition (IBAD) was investigated in this study. The Ar+ ion energy used was selected from 4 to 12 keV, and the ion beam current density was 12μA/cm2. The experimental results revealed that the Fe-Zr amorphous alloys can be obtained in Zr-rich films. With increasing the Ar+ ion energy, a crystal-amorphous-fcc phase-amorphous-crystal phase evolution was observed in Fe(0.54nm)/Zr(45nm)films during IBAD experiment. For Fe-rich films, only partially amorphized films could be formed by IBAD technique.
XIANG Ying-wei, ZHANG Jin-yuan, JIN Cheng-hai. A Study of Ni-P Nanometer Diamond Composite Electroless Plating[J]. Journal of Materials Engineering, 2000, 0(4): 22-25.
The process of Ni-P nanometer diamond composite electroless plating was studied. The structure and hardness of the composite coating were analysed. The results show that the composite coating prepared with injection agitation has a larger nanometer diamond content than that with mechanical agitation and N2 agitation. Several surfactants used in this test fail in increasing nanometer diamond content of the composite coating. The embedded nanometer diamond particles don′t change the structure of Ni-P matrix, but coarsen the surface of the composite coating with a large number of spherical particles.
MA Heng-yi, HUANG Yu-dong, ZHANG Zhi-qian. The Effect of γ-ray Radiating Carbon Fiber on Interfacial Property of Composite[J]. Journal of Materials Engineering, 2000, 0(4): 26-29,33.
In this paper, γ-ray radiation technique has been used to treat carbon fiber (CF); the effects of radiation on the interlaminar shear strength (ILSS) of CF reinforced composites and the bundle tensile strength of CF are studied. The chemical composition of CF surface and interfacial adhesion strength of composite is characterized by the methods of x-ray photoelectron spectroscopy (XPS), torsional braid analysis, interfacial microdebonding. The results show that radiation induces reaction between the surface of CF and the epoxy coating, the interfacial adhesion strength and ILSS of CFRP are improved, and the bundle tensile strength after radiation has not been changed.
LU Guo-hui, ZENG Peng, HUANG Hui-ping, WANG Gui-tang, PAN Zhen-peng, HU She-jun. Microstructure and Properties of Al2O3 Ceramic Gradient Coating Deposited by Detonation Gun Spraying[J]. Journal of Materials Engineering, 2000, 0(4): 30-33.
The ceramic gradient coatings of Al2O3 and self-fluxing alloy were deposited by detonation gun spraying. Experimental results show that the ceramic gradient coating of matrix/Ni60/25%Al2O3+75%Ni60/50%Al2O3+50%Ni60/ Al2O3 has good cohesion, low residual internal stress and mitigative thermal stress. It is also found that the ceramic coating of Al2O3 is γ-Al2O3, but the powder is α-Al2O3 by XRD. There is a phase transition during the processing of spray. The ceramic gradient coatings can apply to thermal barrier and wear resistance coatings under bad working atmosphere.
TIAN Zhen-hui, LIU Yu-yan, WAN Zhi-min, DU Xing-wen. Experimental Studies on Fatigue Damage of Polyester Reinforced Rubber[J]. Journal of Materials Engineering, 2000, 0(4): 34-37.
A set of specially designed clamps and a fatigue testing system was established. The fatigue damage mechanism of polyester reinforced rubber was studied by using enhanced X-ray technique and the fatigue life diagram is obtained in this paper. Results indicate that the fatigue damage of polyester reinforced rubber under strain control presents in stages and three damage modes are rubber crack, polyester/rubber interface debonding and cord break. Different damage mechanism containing the damage of the matrix, interface and the cord fiber correspond with different damage stages. In addition, the thermal effect in the fatigue test is analyzed qualitatively.
XIE Jian-xin, SUN De-qin, WU Chun-jing, WANG Zi-dong. Fabrication of Bimetallic Composite Materials with Duel-mold Continuous Casting Technique[J]. Journal of Materials Engineering, 2000, 0(4): 38-40.
The existing continuous casting processes of bimetallic composite materials were introduced. A new process named Duel-Mold continuous Casting (DMC) technique was proposed in this paper. The conceptual equipment for DMC process was manufactured, and Pb and Pb-Sn eutectic alloy being used as testing materials. The experimental results show that the proposed DMC process is practicable to the continuous casting forming of bimetallic composite materials. Pb and Pb-Sn eutectic alloy are used as the simulated experimental materials, bimetallic clad bars having metallurgical bonding interfaces being fabricated by DMC process.
XU Jiu-hua, WANG Min. Study on Internal Threads in High Strength Steels by Cold Form Tapping[J]. Journal of Materials Engineering, 2000, 0(4): 41-15,44.
The influence of strengthening of internal threads by cold form tapping on the fatigue property of high strength steel is investigated. In order to strengthening mechanism of formed threads residual stresses near to the root of the threads is measured by Moir Interferometry, and the fracture of sample is surveyed by means of SEM. The results of fatigue tests shows that fatigue lives of the threads of 300M steel strengthened by forming tap are from four to thirty times longer than those of cut threads at the stress of 500 and 600MPa.
ZHANG Yi, ZHANG Wen-feng, YAN Hai. Quantitative Analysis in Evaluating Fatigue Lives of Components[J]. Journal of Materials Engineering, 2000, 0(4): 45-48.
Basic theory of evaluating fatigue lives by fatigue striations had been clarified. With the quantitative analysis, the crack length a and the crack propagation rate da/dN were measured and their relationship was established. Paris formula was applied to deduce da/dN curve in crack propagation stage, then the propagation lives could be obtained. The process was conducted in evaluating fatigue lives of a turbine disk and 30CrNi4MoA steel specimens as examples.
