• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1995.10a
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• pp.181-187
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• 1995

The effet of glass fiber and graphite on the wear properies in tin-bronze alloy matrix composites was studied by a pin-on-disk type wear testing machine. The results obtained from the wear test were analized by SEM observations of worn surfaces of pins and disks and EPMA composition measurments. The amount of wear was devreased as increasing the content of glass fiber in matrix, since the alloy matrix was reinforced by glass fibers. The wear mechanism of the matrix specimen without glass fibers was proved as the contact area delamination. Oxide layer formed on sliding surface led to the increasing wear resistance. Specimens containing graphite particles showed an lubrication effect to counter disks.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2000.04a
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• pp.187-191
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• 2000

High temperature creep behaviour of Al-5 wt% Mg alloy reinforced with 7.5% BN flakes was studied. The composite specimens showed two main creep characteristics : (1) the value of the apparent stress exponent of the composite was high and varied with applied stress (2) the apparent activation energy for creep was much larger than that for self-diffusion in aluminum The true stress exponent of the composite was set equal to 5. Temperature dependence of the threshold stress of the composite was very strong. Which could not be rationalized by allowing for the temperature dependence of the elastic modulus change. AIN particles which were incorporated into the Al matrix during fabrication of the composite by the PRIMEXTM method were found to be effective barriers to dislocation motion and to give rise the threshold stress during creep of the composite

• Journal of Korea Foundry Society
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• v.18 no.4
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• pp.373-382
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• 1998

Particulate reinforced aluminum alloys produced by indirect squeeze casting are difficult to shape by cutting or milling. Therefore near net shape forming of complex shapes is of high economic and technical interest. The complex shape products of $SiC_p/6061$ Al composites are fabricated by the melt-stirring and indirect squeeze casting process. The mold temperatures are $200^{\circ}C$ and $300^{\circ}C$ and applied pressures are 70, 100, and 130 MPa. The volume fractions of the reinforcements are in the range of 5 vol% to 15 vol%. The reinforcement dispersion state are observed using on optical microscope. By employing observed results systematically a correlation is demonstrated among the microstructure, particles behavior, mechanical properties and processing parameters for an optimum melt-stirring(compocasting) and indirect squeeze casting process of MMCs. A procedure to establish the optimum squeeze casting of Al-MMCs is proposed.

• Journal of the Korean Ceramic Society
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• v.32 no.7
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• pp.846-852
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• 1995

The multiply reinforced mullite-zirconia composites were prepared with addition of Al2O3 particles, platelets, and fibers. The sinter-HIP specimens (presintered at 1$700^{\circ}C$ and hipped at 1$600^{\circ}C$) showed that the fracture toughness of Al2O3 fiber reinforcement (4.4 MPa.{{{{ SQRT {m} }}) was higher than those of platelet (4.0 MPa.{{{{ SQRT {m} }}) and of particle (3.9MPa.{{{{ SQRT {m} }}) reinforcement, whereas the fracture strength of Al2O3 particle reinforcement (304 MPa) was higher than those of platelet (293MPa) and of fiber (248MPa) reinforcement.

• Proceedings of the Materials Research Society of Korea Conference
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• 2012.05a
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• pp.91.2-91.2
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• 2012

The TiB2-reinforced iron matrix nanocomposite (Fe-TiB2) was in-situ fabricated from titanium hydride (TiH2) and iron boride (FeB) powders by a simple and cost-effective process that combines the mechanical activation (MA) and a subsequent heat treatment (HT). Effect of milling factors and synthesized temperatures on the formation of the nanocomposite were presented and discussed. A differential thermal analyser (DSC-TG) was employed for examination of thermal behavior of MAed powders. Phases of the nanocomposite were confirmed by X-ray diffraction analysis (XRD). The morphologies and microstructure of nanocomposite were investigated by field emission-scanning electron microscopy (FE-SEM) and energy-dispersive X-ray spectroscopy (EDS). Phase composition and distribution were analyzed by electron probe X-ray microanalysis (EPMA). Results showed that TiB2 particles formed in nanoscale were uniformly distributed in alloyed Fe matrix.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.855-856
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• 2006

In the present work, hot workability of particulate-reinforced Al6061-20%SiC composite produced by direct hot extrusion technique was studied. Uniaxial hot compression test at various temperatures and strain rates was used and the workability behavior was evaluated from the flow curves and the attendant microstructures. It was shown that the presence of SiC particles in the soft Al6061 matrix deteriorates the hot workability. Bulging of the specimens and flow lines were observed, which indicate the plastic instability during hot working. Microstructure of the composites after hot deformation was found to be heterogeneous, i.e. the reinforcement clusters were observed at the flow lines. The mechanism of deformation was found to be controlled primarily by dynamic recrystallization.

• Advanced Composite Materials
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• v.18 no.3
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• pp.287-295
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• 2009

$\beta$-Tricalcium phosphate ($\beta$-TCP) particles reinforced bioresorbable plastics poly-L-lactide (PLLA) composites were prepared by injection molding. The nominal weight ratio of $\beta$-TCP was selected as 5, 10 and 15%. In order to clarify effects of the PLLA crystallinity on the mechanical properties, the specimens were heat treated isothermally. Results of differential scanning calorimetry indicated that the PLLA crystallinity increased with increasing heat treatment temperature. Bending and compressive tests were conducted on the specimen with different $\beta$-TCP contents and crystallinities. The results show that the bending and compressive moduli increased with increasing $\beta$-TCP contents and crystallinity. On the other hand, bending strength decreased with increasing $\beta$-TCP contents. Maximum bending strength was obtained at the heat treatment of $70^{\circ}C$ for 24 h, whereas compressive 0.2% proof strength increased with increasing heat treatment temperature. This difference is attributed to the difference in the microscopic damages.

• Journal of the Korean Ceramic Society
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• v.30 no.12
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• pp.1066-1070
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• 1993

When looked upon as a polycrystalline, ceramics have two basic differences from a single crystal. One is that there exist grain boundaries, the other is that the crystal axes of each small crystal are arranged in random directions. But the crystal axes fo small crystals which compose ceramics may be made to have the tendency of being arranged in a specific direction. This is called that the crystal axes are oriented. The degree of the direction arrangement of the crystal axes is called orientation. In order to orient the crystal axes effectively, the fiberous barium titanates were made through KDC method and the ion exchange method. And then they were arranged through pressing, doctor blade, and syringe. As the result of Lotgering evaluation, the sample oriented through syringe showed the highest orientation. After sintering, though the most particles that had been fiberous shaped became global shape viewed through SEM, the orientation of the crystals was reinforced by means of sintering.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2004.04a
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• pp.219-222
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• 2004

The effects of short fiber and particle hybrid reinforcement on fatigue crack propagation behaviors in aluminum matrix composites have been investigated. Single and hybrid reinforced 6061 aluminum containing same 20 $Al_2O_3\;volume\%$ with four different constituent ratios of short fibers and particles were prepared by squeeze casting method and tested to check the near-threshold and stable crack growth behavior. The fatigue threshold of the composites increased with portion of particle contents and showed the improved crack resistance especially in low stress intensity range. Addition of particle instead of short fiber also increased fracture toughness due to increase of inter-reinforcement distance. These increase in both fatigue threshold and fracture toughness eventually affected the fatigue crack growth behavior such that the crack growth curve shift low to high stress intensity factor value. Overall experimental results were shown that particle reinforcement was enhanced the fatigue crack resistance over the whole stress intensity factor range.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.11a
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• pp.573-576
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• 2004

High performance SFRC composed of mira-sized ultra fine particles is characterized by high strength, high ductility and excellent durability. therefore many researches about materials based on new composition like this are performed recently. many researchers have reported that adding steel fiber to concrete improved its tensile and flexural strength significantly. the main objective of this research is to examine the effect of adding steel fiber on the tensile strength of high performance SFRC. variables considered in this study are w/c ratio and fiber volume fraction.