The Effects of Nano Mgo on Physical and Mechanical Properties of Al2O3-SiC Composites
A. Nemati1, F. Surani2, H. Abdizadeh3, and H.R. Baharvandi4
1 Department of Materials Science and Engineering, Sharif University of Technology, Azadi St., Tehran, Iran
received August 28, 2011, received in revised form January 5, 2012, accepted January 19, 2012
Vol.3, No.1, Pages 29-34 DOI: 10.4416/JCST2012-00034
In this research, the effects of nano-sized MgO in Al2O3-SiC composites were investigated. The overall changes in the density and mechanical properties of sintered samples (hardness, bending strength and toughness) were evaluated.
After mixing, drying and uniaxial compaction of the powders, they were first heat-treated at low temperature in an electric furnace to remove any residuals. They were then heat-treated at high temperature (1700 °C) inside a graphite furnace in argon atmosphere for sintering (at normal and high pressure). The content of MgO in the Al2O3-10 vol% SiC composite was 0, 500, 1000, and 1500 ppm.
The fracture toughness (KIC) of sintered composite with 10 vol% SiC (nano-sized) and different amounts of MgO was investigated by means of the Vickers indentation method. Microstructural analysis was performed using a scanning electron microscope.
The data showed that the mechanical properties were increased up to 1000 ppm MgO and then decreased above that. Microstructural observations revealed that in Al2O3-10 vol% SiC nanocomposites, nano-scale SiC particles were normally distributed all over the Al2O3 matrix and inhibited the abnormal grain growth of Al2O3. In addition, transgranularly fractured alumina grains were observed on the fracture surface of the samples.
The results also showed that the fracture toughness of the composites with MgO was improved and better than that of Al2O3-10 vol% SiC samples.
Keywords: Nanocomposite, sintering, additive, mechanical properties, microstructure
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