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2. Investigation on microstructure and fracture mechanism of n-SiCp/7075 Al composites.

Author

Zuo, Cheng Ming, Du, Xiao Ming, Luan, Dao Cheng, Zheng, Kai Feng, Hu, Zhi Hua, Li, Yuan, Deng, Tian Xin, Ren, Yang, and Wang, Zheng Yun

Subjects
DISPERSION strengthening, ALUMINUM composites, MICROSTRUCTURE, SCANNING electron microscopes, CRYSTAL grain boundaries
Abstract

In the present study, the composites have been prepared using vacuum hot pressing process technique. The influence of 2.0 wt.% nanometric SiC particles (n-SiCp) on the microstructure and fracture mechanism of 7075 aluminum alloy was studied by means of metallographic microscope, scanning electron microscope (SEM), energy-dispersive spectrometer (EDS), X-ray diffraction (XRD), laser scanning confocal (LSC). The results indicate that SiCp fill at grain boundaries dispersing evenly and nail to aluminum grains which sizes have been reduced successfully, that making the organization tighter, the gaps fewer and the surface rougher. Meanwhile, phases (MgZn2) precipitated from the 7075 aluminum alloy were been detected. The grain bonding states of matrix alloys are strengthened by the combination of fine grains strengthening and dispersion strengthening and thus affect the fracture morphology. The micro-fracture mechanism of 7075 aluminum alloy is micro-porous aggregation fracture, however, the 7075 aluminum matrix composites (AMCs) are quasi cleavage fracture. [ABSTRACT FROM AUTHOR]

Published
2020
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3. Ferroelectric Relaxor Behavior of Ba(Ti0.91Zr0.09)O3 Ceramics

Author

Song Tianxiu, Luan Dao-cheng, Chen Tao, and Ding Shihua

Subjects
Permittivity, Materials science, Valence (chemistry), Condensed matter physics, Doping, Dielectric, Condensed Matter Physics, Microstructure, Electronic, Optical and Magnetic Materials, visual_art, Electric field, visual_art.visual_art_medium, Polar, Ceramic
Abstract

Ba (Ti0.91Zr0.09) O3 ceramics doped with Bi2O3 and Li2O respectively were prepared by a solid phase reaction. The effect of A-site donor-acceptor doped on dielectric properties was investigated. Dielectric properties were measured from −30°C to 130°C at different frequencies. Relaxor behavior was observed with increasing additive oxides concentration. Additive oxides introduce structural disorder, causing perturbations like local electric field and strain. These perturbations reduce the long-range polar order resulting in relaxor behavior. The corresponding relaxor characteristics were determined and discussed according to the A-site substituted cation type.

Published
2009
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5. FEM Analysis on Thermoelectric Properties of Metal/TiO2–x Composites with Random Distribution of Metal Powder

Author

Sagara, Katsuhiro, Lu, Yun, and Luan, Dao Cheng

Abstract

Analysis model of finite element method with a random distribution for thermoelectric composites was built. Thermoelectric properties including electrical resistivity, Seebeck coefficient and thermal conductivity of M/TiO2–x (M = Cu, Ni, 304 stainless steel (304SS)) thermoelectric composites were investigated by the proposed model. Cu/TiO2–x composite showed a large decrease in electrical resistivity while 304SS/TiO2–x composite thermal conductivity was slightly increased. Calculated dimensionless figure-of-merit, ZT of Ni/TiO2–x composite was higher than those of TiO2–x and the other composites in a wide range of metal volume fractions because Ni has large absolute values of Seebeck coefficient, power factor and dimensionless figure-of-merit compared to the other two metals. It was found that power factor and dimensionless figure-of-merit of thermoelectric composites depended on the balance among electrical resistivity, thermal conductivity and Seebeck coefficient. The results revealed that it is important for M/TiO2–x composites to choose suitable addition metal with high power factor and dimensionless figure-of-merit.

Published
2013
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