共查询到20条相似文献,搜索用时 15 毫秒
1.
Effect of Heat Treatment on Grain Size, Phase Assemblage, and Mechanical Properties of 3 mol% Y-TZP 总被引:1,自引:0,他引:1
The effect of heat treatment on the grain size, phase assemblage, and mechanical properties of a 3 mol% Y-TZP ceramic was investigated. Specimens were initially sintered for 2 h at 1450°C to near theoretical density; some specimens were then heat-treated at 1550°, 1650°, 1750°, or 1850°C to coarsen the microstructure. The average grain size increased with heat treatment from <0.5 to ∼10 μ-m. Phase analyses revealed predominantly tetragonal and cubic phases below 1750°C, with a significant decrease in tetragonal content and increase in monoclinic content for temperatures >1750°C. The maximum fraction of tetragonal phase that transformed during fracture corresponded with the largest tetragonal grain size of ∼5–6 μm. Strength was on the order of 1 GPa, and was surprisingly insensitive to heat-treatment temperature and grain size, contrary to previous studies. The fracture toughness increased from 4 to 10 MPa.m1/2 with increasing grain size, owing to an increasing transformation zone size. Grain sizes larger than 5–6 μm spontaneously transformed to monoclinic phase during cooling. Such critical grain sizes are much larger than those found in past investigations, and may be due to the greater fraction of cubic phase present which decreases the strain energy arising from crystallographic thermal expansion anisotropy of the tetragonal phase. 相似文献
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Effect of Microstructure on the Tribological and Mechanical Properties of CuO-Doped 3Y-TZP Ceramics 总被引:1,自引:0,他引:1
Shen Ran Louis Winnubst Dave H. A. Blank Henry R. Pasaribu Jan-Willem Sloetjes Dik J. Schipper 《Journal of the American Ceramic Society》2007,90(9):2747-2752
Dense 8 mol% CuO-doped 3Y-TZP ceramics were prepared by pressureless sintering for 8 h at 1500° and 1550°C, respectively. Transmission electron spectroscopy revealed that the ceramic sintered at 1500°C exhibits grain boundaries free of any amorphous phase, while crystalline copper-oxide grains were found in the zirconia matrix, whereas the sample sintered at 1550°C contains a Cu-rich amorphous grain boundary layer. The tribological behavior of these materials was tested under dry-sliding conditions using a pin-on-disk tribometer. The material sintered at 1500°C showed self-lubrication resulting in a low coefficient of friction ( f ) of 0.2–0.3 and a low specific wear rate ( k ) ≪ 10−6 mm3 ·(N·m)−1 . In contrast, the material sintered at 1550°C showed poor tribological behavior ( f =0.8–0.9; k ≫ 10−6 mm3 ·(N·m)−1 under the same conditions. The difference in the tribological behavior of these two materials was interpreted on the basis of mechanical properties and microstructural characteristics. 相似文献
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Two-Stage Sintering of Alumina with Submicrometer Grain Size 总被引:1,自引:1,他引:1
Katarína Bodiová Pavol ajgalík Duan Galusek Peter vanárek 《Journal of the American Ceramic Society》2007,90(1):330-332
This work verifies the applicability of two-stage sintering as a means of suppressing the final stage grain growth of submicrometer alumina. The first heating step should be short at a relatively high-temperature (1400°–1450°C) in order to close porosity without significant grain growth. The second step at temperatures around 1150°C facilitates further densification with limited grain growth. Fine-grained alumina with a relative density of 98.8% and a grain size of 0.9 μm was prepared by two-stage sintering. A standard sintering process resulted in ceramics with identical relative density and a grain size of 1.6 μm. 相似文献
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Grain Size Dependence of Hardness in Dense Submicrometer Alumina 总被引:3,自引:1,他引:2
Pressureless sintered alumina compacts with a submicrometer microstructure exhibit a hardness that approaches or even exceeds the level of advanced hotpressed composites of Al2 O3 + 35 vol% TiC, whereas the strength of both ceramics is approximately the same. The combination of reduced dislocation mobility (due to the small grain size), high density, and density homogeneity are the prerequisites for the surprisingly high hardness. Quasiconventional powder processing is used to produce these outstanding alumina bodies. 相似文献
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Dependence of Mechanical Strength of Brittle Polycrystalline Specimens on Porosity and Grain Size 总被引:7,自引:0,他引:7
F. P. KNUDSEN 《Journal of the American Ceramic Society》1959,42(8):376-387
An empirical equation form, approximating the apparent dependence of the strength of brittle polycrystalline specimens on the combined effect of porosity and grain size, has been developed from concepts and data in the literature. The form is shown to be applicable to data for thoria and chromium carbide specimens. 相似文献
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Toma Kosma Ale Dakskobler edomir Oblak Peter Jevnikar 《International Journal of Applied Ceramic Technology》2007,4(2):164-174
Effects of dental grinding, sandblasting, fatigue, and aging on the biaxial flexural strength of yttria partially stabilized tetragonal zirconia ceramics were evaluated. Grinding lowers the mean strength and reliability under static and cyclic loading. In contrast, sandblasting provides a powerful tool for surface strengthening; it also hinders the propagation of the diffusion-controlled transformation during exposure to aqueous environments. By introducing moderate porosity, a reasonable compromise between the mechanical strength and the elastic modulus has been achieved. Such biscuit-sintered specimens also exhibited full hydrothermal stability. Novel experimental dental root posts were designed that exhibit certain advantages over the zirconia posts already in clinical use. 相似文献
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Experimental findings are presented for the effect of microstructure on the room-temperature transverse bend strength properties of hot-pressed dense pure alumina and magnesia. Bend strength shows an exponential dependence on porosity but is sensitive to fabricating temperatures because of changes in grain size. Log-log plots of strength (extrapolated to zero porosity) versus grain size reveal the relation
S = 86,000 G−1/3 (psi) for alumina and S = 50,000G−1/6 (psi) for heat-treated specimens of magnesia ( G = grain size in microns). 相似文献
S = 86,000 G
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Prapaipan Chantikul Stephen J. Bennison Brian R. Lawn 《Journal of the American Ceramic Society》1990,73(8):2419-2427
An investigation of the interrelationships between strength, crack-resistance ( R -curve) characteristics, and grain size for alumina ceramics has been carried out. Results of identation-strength measurements on high-density aluminas with uniform grain structures in the size range 2 to 80 μm are presented. A theoretical fit to the data, obtained by adjusting parameters of a constitutive frictional-pullout relation in a grain-bridging model, allows determination of the critical microstructural parameters controlling the R -curve behavior of these aluminas. The primary role of grain size in the toughness characteristic is to determine the scale of grain pullout at the bridged interface. It is shown that the strength properties are a complex function of the bridged microstructure, governed at all but the finest grain sizes by the stabilizing effect of the R -curve. The analysis confirms the usual negative dependence of strength on grain size for natural flaws that are small relative to the grain size, but the dependence does not conform exactly to the −1/2 power predicted on the basis of classical "Griffith-Orowan" flaws. The analysis provides a self-consistent account of the well-documented transition from "Orowan" to "Petch" behavior. 相似文献
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Semielliptical surface flaws of different sizes were introduced into Al2 O3 by Knoop microhardness indentation. The specimens were fractured by four-point bending and the profiles of the indentation flaws were determined by observing the fracture surfaces with a scanning electron microscope. The relation between the indentation flaw size and the fracture strength could be well explained by applying the fracture-mechanics analysis for semielliptical surface flaw in bending. The calculated values of the as-indented critical stress intensity factor, KIC , were lower than previously reported presumably because of the influence of the residual stresses produced by the indenter. 相似文献
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IVAN B. CUTLER 《Journal of the American Ceramic Society》1957,40(1):20-23
The strength properties of sintered alumina rods, as determined by modulus of rupture experiments, were measured for the purpose of finding the influence of grain size on strength. Sintering temperatures below and above the recrystallization temperature region were utilized in the fabrication of sintered alumina rods so that a wide variation of grain sizes could be tested. Porosity, measured as bulk density, had the largest influence on the moduli of rupture. No prominent change in strength could be observed as a result of recrystallization, but a minor decrease in strength could be attributed to an increase in void size or an increase in grain size. 相似文献
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不同烧结法对3Y-TZP陶瓷力学性能的影响 总被引:1,自引:0,他引:1
本文研究了低温烧结含3mol%氧化钇的四方多晶氧化锆(3Y-TZP)的烧结性能和力学性能,以及进行热等静压(HIP)后其力学性能的变化。成形后的3Y-TZP在常压、1300~1450℃温度下进行烧结。由于该粉料有很高的烧结活性,在1300℃低温烧成下就可获得相对密度大于94%的烧结体;在1350℃烧成温度下3Y-TZP获得了最佳的力学性能。其断裂韧性(KIC)和维氏硬度(HV)分别达到18.7MPa.m1/2和13.7GPa,其中应力诱导相变是其主要的增韧机理。对低温烧成的3Y-TZP陶瓷进行热等静压烧结后发现,HIP增大3Y-TZP陶瓷HV的作用显著,可使其增至14.3GPa。 相似文献
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Igor Levin Wayne D. Kaplan David G. Brandon Albir A. Layyous 《Journal of the American Ceramic Society》1995,78(1):254-256
A simple model was developed which describes the effect of SiC submicrometer particles on the fracture toughness of alumina–SiC "nanocomposites." This effect was attributed to the change in the fracture mode observed in alumina on adding SiC submicrometer particles, which was suggested to be a result of both matrix weakening and grain boundary strengthening. The model suggests that the increase in fracture toughness should be obtained only for small additions (less than 5 wt%) of SiC. 相似文献
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液相烧结 3Y-TZP 陶瓷的相组成与力学性能 总被引:2,自引:1,他引:1
以 CaO-MgO-SiO2 玻璃为烧结助剂,用液相烧结法制备了物质的量分数为 3% 氧化钇稳定四方氧化锆陶瓷(3Y-TZP).研究了烧结助剂对材料致密化、显微结构、相组成及力学性能的影响.结果表明:烧结助剂的引人显著降低了材料的烧结温度,使材料具有细晶显微结构,并对材料的相组成产生影响,同时也使材料具有良好的力学性能.材料的力学性能主要与其致密化程度有关,在最佳条件下,材料的抗弯强度和断裂韧性可分别达到 691MPa 和6.6MPa·m1/2. 相似文献
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Hiroyasu Tamai Takashi Hamauzu Akihito Ryumon Kaoru Aoki Kohei Oda Tetsuo Yoshio 《Journal of the American Ceramic Society》2000,83(12):3216-3218
The hydrothermal corrosion and strength degradation of aluminum nitride (AlN) ceramics were investigated. The weight gain in AlN ceramics after corrosion occurred because of the formation of boehmite. The reaction kinetics of AlN with water were diffusion controlled through the boehmite product layer. At 180°C, immersion in water caused no strength degradation, and water vapor caused a 20% strength degradation. At 300°C, immersion in water caused a 20% strength degradation, and water vapor caused a 30% strength degradation. 相似文献
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本文分别以TiO2和MgO纳米粉体为烧结助剂,采用微波烧结技术制备了3Y-TZP/Al2O3复相陶瓷.研究了烧结助剂含量对材料相组成、致密化及力学性能的影响,通过XRD分析了复相陶瓷中t-ZrO2相的相对量变化,并采用SEM观察了弯曲断裂断口形貌.结果表明:随烧结助剂添加量的增加,微波烧结复相陶瓷的致密度、硬度和弯曲强度均有所增加,均优于传统烧结性能,陶瓷颗粒更细.烧结助剂添加量为0.2wt% MgO、0.4wt% TiO2,在1300℃微波烧结30 min时试样的致密度为98.1%,显微硬度和抗弯强度分别达18.9 GPa和626 MPa. 相似文献