• Journal of the Korean Ceramic Society
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• v.41 no.2
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• pp.125-130
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• 2004

The effect of SiC particle size on the microstructures and mechanical properties of A1$_2$O$_3$-SiC composite was investigated. Two types of SiC powders having average particle sizes of 0.15 ${\mu}{\textrm}{m}$ and 3 ${\mu}{\textrm}{m}$ were used. The grain growth in the specimen containing 0.15 ${\mu}{\textrm}{m}$ SiC was effectively inhibited due to the fine SiC particles. However, after the formation of some abnormal grains, fast and exaggerated grain growth occurred which led to the microstructure of large grains with irregular shape. Fracture strength decreased due to the abnormal large grains. On the other hand, for specimen containing 3 ${\mu}{\textrm}{m}$ SiC showed normal grain growth behavior from initial sintering stage. Large SiC particles, however, effectively inhibited exaggerated grain growth after nucleation of a few abnormal grains. As a consequence, microstructure consisted of homogeneous elongated grains. In the A1$_2$O$_3$-2.5SiC(0.15 ${\mu}{\textrm}{m}$)-2.5SIC(3 ${\mu}{\textrm}{m}$) composite fabricated by mixing the two types of SiC powder, abnormal grain growth occurred. However, the good fracture strength was maintained regardless of microstructural changes in this specimen.

• Composites Research
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• v.21 no.6
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• pp.15-22
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• 2008

Reversed plane bending fatigue tests were conducted on SiC particle aluminum composite. The initiation and growth behaviors of small surface fatigue cracks were continuously monitored by the replica technique and investigated in detail. The fatigue life of MMC is shorter than that of matrix because there exists interface debonding of SiC particles and matrix on the whole face of the notch part in the casting metal matrix composite(MMC). The coalescence of micro-cracks was observed in the tests conducted at high stress levels. Due to the coalescence, a higher crack growth rate of small cracks rather than those of long cracks was recognized in da/dn-$K_{max}$ relationship.

• Journal of Powder Materials
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• v.16 no.6
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• pp.416-423
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• 2009

Diamond/SiC composites are appropriate candidate materials for heat conduction as well as high temperature abrasive materials because they do not form liquid phase at high temperature. Diamond/SiC composite consists of diamond particles embedded in a SiC binding matrix. SiC is a hard material with strong covalent bonds having similar structure and thermal expansion with diamond. Interfacial reaction plays an important role in diamond/SiC composites. Diamond/SiC composites were fabricated by high temperature and high pressure (HPHT) sintering with different diamond content, single diamond particle size and bi-modal diamond particle size, and also the effects of composition of diamond and silicon on microstructure, mechanical properties and thermal properties of diamond/SiC composite were investigated. The critical factors influencing the dynamics of reaction between diamond and silicon, such as graphitization process and phase composition, were characterized. Key factor to enhance mechanical and thermal properties of diamond/SiC composites is to keep strong interfacial bonding at diamond/SiC composites and homogeneous dispersion of diamond particles in SiC matrix.

• Journal of the Korean Society for Heat Treatment
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• v.15 no.2
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• pp.82-92
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• 2002

In the present investigation wear behavior of the 6061AI composites reinforced with 5, 10, 20% SiC particles for dry sliding against a SM45C counterface was studied as a function of load and sliding velocity. Sliding wear tests were conducted at two loads(19.6 and 49N) and three sliding velocities(0.2, 1 and 2 m/sec) at constant sliding distance of 4000 m using pin-on-disk machine under room temperature. Presence of SiC reinforcement particles in the composites has displayed a transition from mild to severe wear at relatively higher applied load and sliding velocity compare to that of the matrix metal. As the volume fraction of SiC particles increased, the transition moved to a more severe wear conditions. Eventually, mild wear prevailed at a most severe wear conditions in this study, that was 49N load and 2 m/sec sliding velocity in 20% SiC particle/6061AI composite.

• Journal of Powder Materials
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• v.6 no.3
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• pp.246-250
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• 1999

The effects of the ${\beta}-Si_3N_4$ starting particle size and $\alpha$/$\beta$ phase transformation during sintering process on the microstructure evolution of Yttrium $\alpha$-Sialon ceramics were investigated. As-received ${\beta}-Si_3N_4$ powder (mean particle size: 0.54$\mu$m) and classified ${\beta}-Si_3N_4$ powder(mean particle size: $0.26\mu{m}$) were used as starting powders. With decreasing the starting particle size, the growth of elongated grains was enhanced, which resulted in the whisker -like microstructure with elongated grains. These results were discussed in relation to the two-dimensional nucleation and growth theory. In the specimen heat treated at $1600^{\circ}C$ for 10h before sintering at $1950^{\circ}C$for 1h under 40atm(2-step sintering), the grain size was smaller than of the 1-step sintering at 195$0^{\circ}C$ for 1h. However, bimodal microstructure evolution were not not remarkable in both sample, which is ascribed to the $\alpha$-phase contents existing in ${\beta}-Si_3N_4$ starting powder.

• Journal of the Korean Ceramic Society
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• v.36 no.11
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• pp.1261-1265
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• 1999

Effect of SiC particle size of the densification of Al2O3-SiC composite during pressureless sintering was investigated. Two types of SiC powders having average particle size of 0.15${\mu}{\textrm}{m}$ and 3${\mu}{\textrm}{m}$ were used. Densification rate of the specimen containing 0.15${\mu}{\textrm}{m}$ SiC particles was slower than that of the specimen containg 3${\mu}{\textrm}{m}$ SiC particles. Although the relative density of the specimen containing 0.15${\mu}{\textrm}{m}$ SiC particles was below 90% of theoretical density after sintering at 155$0^{\circ}C$ the complete closure of open pores occurred. Therefore full densification could be obtained by subsequent HIP. On the other hand in the specimen containing 3${\mu}{\textrm}{m}$ SiC particles the complete closed pore was observed at 95% of theoretical density. Such a fast pore closure in the specimen containing 0.15${\mu}{\textrm}{m}$ SiC particles is likely to occur as a result of dense reaction layer formation on the specimen surface which is attributed to the high reactivity of small size particles with sintering atmosphere.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1997.03a
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• pp.81-84
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• 1997

The hot deformation behavior of SiCp/AA2024 composites reinforced with different sizes of SiCp reinforcements (1, 8, 15, 36, and 44${\mu}{\textrm}{m}$) was investigated by hot torsion tests. The hot restoration of the composites depending on the SiCp reinforcements particle size was studied from the effective stress - strain curves. Dynamic recrystallization (DRX) was occurred in the SiCp/AA2024 composites during the hot deformation at 320 - 43$0^{\circ}C$ under a strain rate of 1.0/sec. Also, the critical strain for DRX decreased with decreasing the reinforcement size of SiCp from 44 to 8${\mu}{\textrm}{m}$. The composite reinforced with SiCp of 8${\mu}{\textrm}{m}$ showed the highest flow stress (265 MPa) and the work hardening rate at 32$0^{\circ}C$ under a strain rate of 1.0/sec.

• Journal of Korea Foundry Society
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• v.14 no.6
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• pp.530-540
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• 1994

Aluminium-silicon alloy(JIS AC8A) matrix composites reinforced with SiC particles were fabricated by spray-cast forming process, and the microstructure of powders and preforms produced were studied by using an optical and scanning electron microscopy. SiC particles were co-sprayed by mixed phase injection method during the spray casting process. Most of the composite powders formed by this mixed phase injection method exhibit morphology of particle-embedded type, and some exhibits the morphology of particle attached type due to additional attachment of the SiC particles on the surface of the powders in flight. The preforms deposited were resulted in dispersed type microstructure. The pre-solidified droplets and the deposited preform of SiC-reinforced aluminium alloy exhibit finer equiaxed grain size than that of unreinforced aluminium alloy. Eutectic silicons of granular type are crystallized at the corner of the aluminum grains in the preforms deposited, and some SiC particles seem to act as nucleation sites for primary/eutectic silicon during solidification. Such primary/eutectic silicons seem to retard grain growth during the continued spray casting process. It is envisaged from the microstructural observations for the deposited preform that the resultant distribution of SiC injected particles in the Al-Si microsturcture is affected by the amount of liquid phase in the top part of the preform and by the solidification rate of the preform deposited.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1995.10a
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• pp.172-180
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• 1995

Isothermal interrupted deformation behavior of 10vol.%SICp/AI-Si composites was investigated by hot torsion test at the temperature ranges from 27$0^{\circ}C$ to 43$0^{\circ}C$ and at strain rate range of 1.26X10-2~2.16X10-1/sec. With increasing pass strain, flow stresses were high compared to continuous deformation condition. Fractional softening was increased with temperature imterruption time and pass strain. Fractional softening of 10vol.%SiCp/AI-Si composites was lower than that of AI-Si matrix at 37$0^{\circ}C$. However at high temperature of 43$0^{\circ}C$, SiC particle promoted static softening, diminishing the dislocation density at the interface of AI-Si matrix and reinforcements, then this resulted in higher fractional softening in composites. Both of failure strain improved reducing the fracture of SiC particle and Si precipitates above 32$0^{\circ}C$, however at low temperature of 27$0^{\circ}C$, the softening effect by interrupted deformation was found to be negligible.

• Journal of the Korean Ceramic Society
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• v.27 no.2
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• pp.265-273
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• 1990

Fine Si-Al-OH-C coprecipitate powders were prepared from Si(OC2H5)4, Al(i-OC3H7)3, and carbon black by a hydrolysis method before fabrication of Sialon-SiC composite powder by carbothermal reduction at 1350$^{\circ}C$ for 10h under N2/H2 mixed atmosphere. The characterization of the synthesized Sialon-SiC composite powders was performed using XRD, BET, SEM, TEM and particle size analysis methods. The average particle size and specific surface area of the synthesized Sialon-SiC composite powder were 0.13$\mu\textrm{m}$ and 20.1㎡/g, respectively when Z=1 and N2 : H2=50 : 50.