Papers by Author: Jeong Keun Lee

Abstract: The tribological behavior of TiC-based metal matrix composites was investigated via measuring counterpart weight. The composites were prepared using powder metallurgy technique. Wear of counterpart by the composites varying from 35 to 45 % by volume Titanium carbide were observed over a load ranges of 9.81 to 49.05 N and sliding velocities of 2.0, 2.2, 2.4, 2.6, 2.8 and 3.0 m/sec. Detailed wear track micro-graphy was done to verify the effect of sliding condition on wear mechanism. Observations indicate that wear rate of counterpart increases with the increase in load and the sliding velocity and discontinuous wear rate change occurs at a certain load.

Abstract: An attempt was made to produce nickel aluminides with fine microstructure from nanoscale nickel and aluminum powders produced by wire electric explosion (WEE). The powders were mixed and spark plasma sintered (SPS) for simultaneous reaction and densification of the material. Various mixing methods were tested to give the best homogeneity of the nanopowders mixtures. Utrasonic pre-treatment of the powders did not result in any positive effect on mixing homogeneity. Sintered compact contained NiAl and Ni3Al phases, showed fine grain size and unexpectedly high hardness possibly due to the presence of aluminum oxide in the starting nanopowders.

Abstract: The microstructure and mechanical property of hot-pressed Al2O3/Cu nanocomposites with a different temperature for atmosphere changing from H2 to Ar have been studied. When the atmosphere changed from H2 to Ar gas at 1450°C, the hot-pressed composite was characterized by inhomogeneous microstructure and low fracture strength. On the contrary, when the atmosphere changed at a lower temperature of 1100°C, a more homogeneous microstructure and higher fracture strength was observed.