Papers by Author: Kyung Ho Min

Abstract: Compressive behavior of 7xxx series Al metal matrix composite (MMC) powders with different ceramic contents and different particle size were investigated. As a starting powder of the experiments, ceramic contents of each starting powder were 5 and 10 wt.% and ceramic particle size of starting powder were 20 and 100 ㎛, respectively. And 7xxx Al blended powder was used for comparison. The powders were uniaxially cold-compacted using cylindrical die with a compacting pressure 250 MPa and sintered at 620oC in a dry N2 atmosphere for 60 min with heating rate of 20oC/min. In case of heat treatment condition, sintered parts were solution treated at 475oC and aged at 175oC. To reveal the effect of Al2O3 particle content and particle size on the mechanical properties of composites, compression test were conducted with constant strain rate of 1×10-3/s using sub-size cylindrical samples of 9 mm diameter. Compression test was performed 5 times and its average value was used. Then fractography analysis was conducted using scanning electron microscope.

Abstract: Mechanical properties of 7xxx series Al metal matrix composite (MMC) powders containing different amounts of ceramic were investigated. The ceramic contents of the starting powders were 5 wt.% or 10 wt.%. 7xxx Al blended powder was used for comparison. The powders were uniaxially cold compacted using a cylindrical die with a compacting pressure of 250 MPa and were sintered at 620oC in a dry N2 atmosphere for 60 min. The heating rate was varied up to 100oC/min. For the heat treatment, sintered parts were solution treated at 475oC and aged at 175oC. Compression tests were conducted to reveal the effect of Al2O3 particle content on the mechanical properties of the composites. Fractography was examined using a scanning electron microscope.

Abstract: The aging behavior of sintered Al composites with various ceramic contents was investigated. 2xxx series blended powder was used as the starting powder. Ceramic contents were 0 wt.% and 5 wt.%. The blended powders were compacted at 250 MPa. The sintering process was performed at 620oC for 60 min in a N2 atmosphere. After sintering, each part was solution-treated at 518oC for 60 min and aged at 180oC. The Rockwell hardness value at the peak aging time increased with increased ceramic contents. However, the peak aging time at maximum hardness was reduced with increased ceramic contents. The changes in aging behavior may have been caused by the acceleration of diffusion due to the strain induced by differences in the thermal expansion coefficients of the matrix and the ceramic phases.