Composite Materials V

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Authors: L.J. Chang, G.R. Fang, Jason S.C. Jang, I.S. Lee, J.C. Huang, Chi Y.A. Tsao
Abstract: Mg65Cu20Y10Ag5 Amorphous/ nano ZrO2 composites alloy powder were fabricated through the combination method of melt spinning and mechanical alloying (MA). The melt spun amorphous matrix ribbons are ground into powders and mixed with 3 vol.% ZrO2 nano particles in the planetary mill. After then formed by hot pressing in Ar atmosphere under the pressure of 700 MPa at the temperature of soft point which measured by TMA (Thermal mechanical Analysis). The hot-pressed bulk composite specimens are compression tested at different temperature within the supercooled temperature region. The flow stress was found decrease with increasing temperature dramatically when the temperature exceeds the middle temperature of supercooled region. The specimens after compression test were examined by X-ray diffractometry and SEM to investigate its crystallinity and fracture mechanism.
Authors: Zheng Yi Fu, Z. Fan, W.J. Tang, Jin Yong Zhang, Wei Min Wang, H. Wang, Yu Cheng Wang, Qing Jie Zhang
Abstract: Hybridization is a promising method for core/shell particles by a mechanical shock process involving dry blending and dry impact blending. In this paper, hybridization was used to prepare TiB2/Ni ceramics/metal and TiB2/Al2O3 ceramics/ceramics core/shell particles. The mechanism of the formation and the features of the core/shell particles were analyzed. The nano- Al2O3 particles can be coated on the surface of micron TiB2 particles directly by hybridization, The sub-micron Al2O3 particles can be coated on the surface of micron TiB2 particles, only with the introducing of PE-wax as transition layer. The mechanical properties of cermet sintered from TiB2/Ni core/shell ceramics/metal particles were compared with that from TiB2/Ni blended particles.
Authors: C.I. Chang, Y.N. Wang, H.R. Pei, C.J. Lee, X.H. Du, J.C. Huang
Abstract: Friction stir processing (FSP) has been applied to fabricate 10~20 vol% nano-sized ZrO2 and 5~10 vol% nano-sized SiO2 particles into an Mg-AZ31 alloy to form bulk composites under the FSP parameters of advancing speed of 800 rpm and pin rotation of 45 min/min. The microstructures and mechanical properties of the resulting composites were investigated. The clustering size of nano-ZrO2 and nano-SiO2 particles, measuring average ~200 nm was relatively uniformly dispersed, and the average grain size of the both Mg alloy of the composites varied within 1.0~2.0 μm after four FSP passes. No evident interfacial product between ZrO2 particles and Mg matrix was found during the FSP mixing in AZ31-Mg/ZrO2. However, significant chemical reactions at the AZ31-Mg/SiO2 interface occurred to form the Mg2Si phase. The mechanical responses of the nano-composites in terms of hardness and tensile properties are examined and compared.
Authors: X.L. Lei, Dong Ming Zhang, Lian Meng Zhang
Abstract: Nano-scale 8mol% titania doped yttria stabilized zirconia (8TiYSZ) powders were prepared by coprecipitation combined with azeotropic distillation process. Powder X-ray diffraction, BET method and TEM were performed to characterize the powder properties. The relative density of 8TiYSZ sample sintered by spark plasma sintering technique at 1150°C for 3min reached 99%. The electrical conductivity of sintered pellet was much higher than the reported one.
Authors: Yi Wang Bao, Si Jian Gao, Yan Fei Han, Ming Guan
Abstract: Bond strength of metal-glass bilayer laminate was determined via a simple testing approach using cross-bonded sample and a special fixture. Tensile and shear strength in the interface for glass-metal composite were obtained by this way. It is demonstrated that the strength can be accurately determined when it is lower than the glue strength but it is invalid if the strength is higher than the glue strength. The specimen preparation and testing principle is introduced for determining the interface bonding strength of coatings.
Authors: Lin Geng, Yi Wu Yan
Abstract: The coefficients of thermal expansion (CTEs) of the 20 vol% SiCp/Al composites fabricated by powder metallurgy process were measured and examined from room temperature to 450°C The SiC particles are in three nominal sizes 5μm, 20μm and 56μm. The CTEs of the SiCp/Al composites were shown to be apparently dependent on the particle size. That the larger particle size, the higher CTEs of the composites, is thought to be due to the difference in original thermal residual stresses and matrix plasticity during thermal loading. The thermal conductivity of the composites also increases with particle size increasing.
Authors: Lei Wang, Yu Dong Huang, Li Liu
Abstract: In the present work, Al2O3 was coated on the quartz fiber by the sol-gel method to improve the high temperature mechanical properties of the quartz fiber/methyl silicon resin composites. The X-ray diffraction results showed that the crystalline property of the Al2O3 coating increased with the processing temperature. Before 500oC treated, the Al2O3 coated fiber reinforced composites have lower flexural strength than the commercial fiber reinforced one. While after 500oC treated, the flexural strength of Al2O3 coated fiber reinforced composites was higher than the uncoated reinforced one. And the flexural strength for the 400oC treated Al2O3 coated fiber reinforced composites was higher than that of the 600oC treated one. The mechanism of the crack propagation in the purchased and Al2O3 coated fiber reinforced composites was also studied through scanning electronic microscopy (SEM).
Authors: Chang An Wang, Hai Long Wang, Yong Huang, Dai Ning Fang
Abstract: ZrB2/SiC ceramic composites reinforced by nano-SiC whiskers and SiC particles have been prepared by hot-pressing at 1950°C for 1hr under 20 MPa pressure in flow argon atmosphere. Effects of SiC addition on microstructure, mechanical properties and thermal ablation/oxidation behavior of ZrB2/SiC composites were investigated. The results showed that the addition of SiC effectively improved the densification of ZrB2/SiC composites and almost full dense ZrB2/SiC composites were obtained when the amount of SiC increased up to 20 vol%. Flexural strength and fracture toughness of the ZrB2/SiC composites were also enhanced; the maximum strength and toughness reached 600 MPa and 8.81 MPa·m1/2 at SiC additions of 20 vol % and 30 vol%, respectively. The composites possessed good resistance to flame ablation and could keep the whole shape without distinct peeling or cracking after flame ablation by oxyacetylene flame for 3 mins. The more SiC added, the better resistance to flame ablation the composites displayed.
Authors: Qiu Bao Ouyang, H.L. Gu, W.L. Wang, Di Zhang, Guo Ding Zhang
Abstract: Friction and wear properties of aluminum matrix composites are studied, including brake speed, brake pressure, and surface temperature etc. A conclusion can be drawn that SiC particle reinforced aluminum matrix composites are of stable friction coefficient, high thermal conductivity, and excellent wear-resistance. Hubs of motorcycle with brake rings of Al/SiC composites were manufactured and exhibited an excellent braking performance.
Authors: Cong Fa Zhang, Wei Cao, Tong Xiang Fan, Di Zhang
Abstract: The (AlN+Mg2Si)/Mg metal matrix composite was successfully fabricated by adding Si3N4 into Mg-Al alloy. The formation mechanisms of AlN and Mg2Si were analyzed; the effects of synthesizing temperature and holding time were investigated as well.

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