共查询到20条相似文献,搜索用时 15 毫秒
1.
2.
The brazing of alumina ceramic to itself was performed using Ag57Cu38Ti5 filler alloy. The bonding was carried out in a vacuum of 7 × 10?3 Pa, and the joining conditions were at 1073, 1123, 1173, 1223, 1273 and 1323 K for 1.8ks under a pressure of 0.01 MPa, at 1123 K with a pressure of 0.01 MPa for 0, 0.3, 0.9, 1.8, 2.7 and 3.6 ks, and at 1123 K for 1.8 ks with pressures of 0, 0.01, 0.05, 0.10, 0.15, 0.20 and 0.30 MPa, to determine the effects of joining temperature, pressure and holding time on the joint strength. The joint strength was measured by shear tests. The interface microstructures and fractured surfaces after testing were observed by scanning electron microscopy (SEM). It was shown that the shear strength of Al2O3/Al2O3 joints was largely affected by the joining conditions; it first increased and then decreased with increasing joining temperature, pressure and holding time and depended mainly on the strength of interfacial reaction layer itself and the interface bonding strength between the reaction layer and the ceramic. The maximum joint strength was obtained when the reaction occurred under a suitable temperature, pressure and time, and the reaction layer thickness was about 2 μm. SEM observations revealed that there were four types of fracture and each kind corresponded to a different strength. 相似文献
3.
4.
A. Garcia-Romero X. Alberdi J. Tezanos M. Anglada 《Journal of Materials Science》1995,30(10):2605-2609
Metal matrix composites are presently being introduced in various industrial applications; specifically δ-alumina short-fibre-reinforced
aluminium composites are already employed by some Japanese companies for the production of car pistons. Many studies on the
fundamental properties of these composites can be found in the literature. However, in spite of what would be expected from
an industrially employed material, some relevant aspects still remain to be studied. One of these important aspects scarcely
found in the literature is the reliability of the material. This paper presents a statistical evaluation of the tensile strength
of a δ-alumina short-fibre-reinforced aluminium alloy by means of Weibull statistics, in order to determine the reliability
and repeatability of the material. 相似文献
5.
6.
7.
采用溶胶-凝胶法在α-Al2O3中空纤维载体上制备了Al2O3-SiO2复合膜,并对复合膜的制备条件及稳定性进行了研究.利用SEM和EDS对复合膜的微观形貌及化学组成进行了分析.结果表明,所制备的担载复合膜表面完整、无缺陷.气体渗透实验进一步说明,复合膜具有一定的气体选择性,在0.1 MPa下对H2/N2的分离因子为3.03,表明气体通过膜的扩散以Knuen扩散传质为主.用等温氮气吸附实验测定了非担载膜的孔径大小和分布,其比表面积为294.85 m2/g,总孔容为0.28 mL/g,最可几孔径小于3 nm. 相似文献
8.
采用溶胶-凝胶法在α-Al2O3中空纤维载体上制备了Al2O3-SiO2复合膜,并对复合膜的制备条件及稳定性进行了研究.利用SEM和EDS对复合膜的微观形貌及化学组成进行了分析.结果表明,所制备的担载复合膜表面完整、无缺陷.气体渗透实验进一步说明,复合膜具有一定的气体选择性,在0.1 MPa下对H2/N2的分离因子为3.03,表明气体通过膜的扩散以Knuen扩散传质为主.用等温氮气吸附实验测定了非担载膜的孔径大小和分布,其比表面积为294.85 m2/g,总孔容为0.28 mL/g,最可几孔径小于3 nm. 相似文献
9.
《Composites》1993,24(3):282-287
Fatigue damage development in two aluminium matrix (Al7SiO.6Mg and Al5Si-3Cu1Mg) composites reinforced with discontinuous Al2O3 fibres has been monitored by means of acoustic emission (AE). The AE signals (RMS) recorded during the tests clearly exhibit three distinct stages which correspond to crack initiation, dominant crack formation and stable propagation. Generally speaking, the cracks initiated at a high load level form close together and a dominant crack forms easily. By contrast, at a low load, initiated cracks are widely separated and the formation of a dominant crack is difficult. If there are large defects in the composite, the first stage is absent, even at low load. In the first stage, little change in microstructure and modulus of the composite is observed; in the second, fibre fracture, interface debonding and matrix cracking occur and there are often sinusoidal cracks in the matrix; in the last stage, the principal characteristic is stable propagation of the dominant crack. The degradation of the elastic modulus of the composite in the last two stages is small. 相似文献
10.
Al2O3 matrix composites with unidirectionally oriented high-purity Al2O3 fibre with and without carbon coating, were fabricated by the filament-winding method, followed by hot-pressing at 1573–1773
K. The composite with non-coated Al2O3 fibre exhibited a bending strength (594 MPa) comparable to that of monolithic Al2O3 (589 MPa). While the composite with a carbon-coated fibre had lower strength (477 MPa), it showed improved fracture toughness
(6.5 MPa m1/2) compared to the composite with an uncoated fibre (4.5 MPa m1/2) and monolithic Al2O3 (5.5 MPa m1/2). This toughness enhancement was explained based on the increased crack extension resistance caused by the fibre pull-out
observed by SEM at the notch tip.
This revised version was published online in November 2006 with corrections to the Cover Date. 相似文献
11.
12.
The mild sliding wear behaviour of a 15 vol % Al2O3P/6061 Al composite has been investigated by using a pin-on-disc reciprocating sliding machine. The composite has been shown to exhibit an excellent wear resistance as compared to the unreinforced matrix alloy. The wear rate of the composite under dry wear conditions with a 12N load is approximately one tenth of that in the 6061 aluminium alloy. The wear rate of the composite under lubrication with 15W/40 gear oil under a 100N load is only one thousandth ofthat in the 6061 aluminium alloy.The dry wear resistance of an over-aged sample is shown here to be better than a peak aged or under-aged sample when the composite was aged at 160°C. The coefficient of friction of the composite was approximately 0.5–0.6 under dry conditions and 0.07 in lubricated wear experiments.In the initial stage, the worn surface of the composite under dry conditions is primarily composed of ploughed grooves and ductile tear. The composite makes a conducting contact with the steel pin. The worn surface is composed of compacted powder and the contact potential gradually increases when the period of the wear experiment goes beyond 2 h. 相似文献
13.
将Al2O3-TiC陶瓷材料与具有固体润滑特性的Al2O3-TiC-CaF2陶瓷材料进行叠层,通过真空热压烧结制备Al2O3-TiC/Al2O3-TiC-CaF2复合叠层陶瓷材料.在环盘式摩擦磨损试验机上进行摩擦磨损实验,研究该材料在不同载荷、转速条件下的摩擦系数和磨损率,分别用SEM及EDS观察材料磨损前后的微观形貌和分析其成分组成,研究其磨损机制.结果表明:在相同载荷条件下,Al2O3-TiC/Al2O3-TiC-CaF2复合叠层陶瓷材料的摩擦系数和磨损率随着转速的升高而下降,在相同转速条件下,其摩擦系数和磨损率随着载荷的增加而下降;Al2O3-TiC/Al2O3-TiC-CaF2复合叠层陶瓷材料的磨损机制主要是磨粒磨损和黏着磨损. 相似文献
14.
M. Ksiazek N. Sobczak B. Mikulowski W. Radziwill B. Winiarski M. Wojcik 《Journal of Materials Science》2005,40(9-10):2513-2517
The subject of the work was to study the effect of Ti thin film on alumina ceramic on mechanical strength and fracture character of Al2O3/Al/Al2O3 joints. The joints were formed by liquid state bonding of alumina substrates covered with titanium thin film of 800 nm thickness using Al interlayer of 30μm thickness at temperature of 973 K in a vacuum of 0.2 mPa for 5 min. The bend strength was measured by four–point bending test at room temperature. Scanning and transmission electron microscopy were applied for detailed characterization of interface structure and failure character of fractured joint surfaces. Result analysis has shown that application of the Ti thin film on alumina leads to decrease of bond strength properties of Al2O3/Al/Al2O3 joints along with the change either of structure and chemistry of interface or of failure character. 相似文献
15.
16.
HONGHUA KAN DAHAI ZHANG HUI YANG MANZHEN GE ZHONGHUA JIANG WENJIAN WENG 《Journal of Materials Science Letters》1997,16(3):190-191
Abstracts are not published in this journal
This revised version was published online in November 2006 with corrections to the Cover Date. 相似文献
17.
18.
High-temperature strength and thermal stability of a unidirectionally solidified Al2O3/YAG eutectic composite 总被引:1,自引:0,他引:1
Y Waku N Nakagawa T Wakamoto H Ohtsubo K Shimizu Y Kohtoku 《Journal of Materials Science》1998,33(5):1217-1225
A unidirectional solidification method was investigated to manufacture Al2O3/YAG eutectic composites with high-temperature resistance that would make them usable at very high temperatures. We were successful in manufacturing a single-crystal Al2O3/single-crystal YAG eutectic composite with a dimension of 40 mm in diameter and 70 mm in length containing no colonies or pores. This composite also displayed excellent high-temperature strength characteristics. The flexural strength was in the range 350400 MPa from room temperature up to 2073 K (just below its melting point of about 2100 K) with no apparent temperature dependence. During tensile tests above 1923 K, the eutectic composite showed evidence of plastic deformation occurring by dislocation motion, and a yield phenomenon similar to many metals was observed. In addition, the microstructure of the composite was extremely stable: after 1000 h of heat treatment at 1973 K in an air atmosphere there was no growth. The above superior high-temperature characteristics are caused by such factors as the eutectic composite having a single-crystal Al2O3/single-crystal YAG structure, the formation of a compatible interface with no amorphous phase and thermal stability, and the combined effect of a YAG phase with superior high-temperature characteristics. © 1998 Chapman & Hall 相似文献
19.
20.
《Vacuum》2010,84(12):1475-1480
In order to clarify the effect of Al2O3 particle size on the arc erosion behavior of the ceramic-reinforced Al2O3/Cu composite, Al2O3/Cu composites with different sizes of Al2O3 particles were prepared by powder metallurgy, the effect of Al2O3 particle size on the characteristics of arc motion was studied, and the mechanism of arc erosion of Al2O3/Cu composites was discussed as well. The results show that with decrease in the size of Al2O3 particles, the erosion area increases significantly and the erosion pits become shallower. The vacuum breakdown is preferred to appear in the area between Al2O3 particle and the copper matrix. Based on the experimental results and theoretical analysis, a particle partition arc model is proposed. 相似文献