• Journal of the Korean Society for Heat Treatment
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• v.21 no.1
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• pp.3-9
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• 2008

Al-Co-N thin films, Al-Co-N/Al-N and Al-Co-N/Al-Co multilayers containing various amounts of Co content were deposited by using a two-facing targets type dc sputtering (TFTS) system. The films were also annealed successively and isothermally at different annealing temperatures. Irrespective of Co content and preparation methods, all the as-deposited films were observed non-magnetized. It was found that annealing conditions can control the magnetic and electrical properties as well as the microstructure of the films.

• Korean Journal of Metals and Materials
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• v.50 no.11
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• pp.861-866
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• 2012

A dense nanostructured TiN-AlN composite was prepared from high-energy ball milled TiN-AlN mixture powders by pulsed current activated sintering (PCAS). A highly dense TiN-AlN bulk composite was obtained within 2 minutes at $1500^{\circ}C$ with the simultaneous application of 80 MPa pressure and pulsed current. The fine crystalline structure of the TiN-AlN mixture, which was obtained by high-energy milling, was effectively maintained during PCAS and resulted in the enhancement of the mechanical properties. The micro hardness and fracture toughness of TiN-AlN composite were $1780kg/mm^2$ and $5MPa.m^{1/2}$, respectively. The mechanical properties were higher than monolithic AlN or TiN.

• Journal of Powder Materials
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• v.20 no.4
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• pp.285-290
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• 2013

$Ti_2AlN$ composites are a laminated compounds that posses unique combination of typical ceramic properties and typical metallic(Ti alloy) properties. In this paper, the powder synthesis, SPS sintering, composite characteristics and machinability evaluation were systematically conducted. The random orientation characteristics and good crystallization of the $Ti_2AlN$ phase are observed. The electrical and thermal conductivity of $Ti_2AlN$ is higher than that of Ti6242 alloy. A machining test was carried out to compare the effect of material properties on micro electrical discharge drilling for $Ti_2AlN$ composite and Ti6242 alloy. Also, mixture table as a kind of tables of orthogonal arrays was used to know how parameter is main effective at experimental design. Consequently, hybrid $Ti_2AlN$ ceramic composites showed good machining time and electrode wear shape under micro ED-drilling process. This conclusion proves the feasibility in the industrial applications.

• The Korean Journal of Ceramics
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• v.6 no.1
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• pp.32-36
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• 2000

Pyrolytic preparations of Ti-Al-N ceramics from three blended precursors were investigated. The precursors were prepared stirring ($HA1N^{i}Pr_m$ and an aminolysis product of $Ti(NMe_2)_4$ with $MeHNCH_2CH_2$NHMe in $C_6/H_6$ . IR and $^1H\;NMR $analyses suggested that essentially no Ti-N-Al bonds were present in the precursors. Pyrolysis of the precursors under $NH_3-N_2$led to the formation of brown solids with ceramic yields of about 30%, and the Ti-Al ratios in the pyrolyzed products were close to those of the precursors. XRD analysis of the pyrolyzed product from the precursor with Ti:Al=5:1 indicated the formation of a NaCl-type compound as the only crystalline phase. Pyrolysis of the precursor with Ti:Al=2:1 led to the formation of AlN besides the major NaCl-type compound. A ceramic composite containing AlN and the NaCl-type compound was formed by pyrolysis of the precursor with Ti:Al=1:2.

• Journal of the Korean Ceramic Society
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• v.34 no.4
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• pp.406-412
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• 1997

Al2O3/SiC hybrid-composite has been fabricated by the conventional powder process. The addition of $\alpha$-Al2O3 as seed particles in the transformation of ${\gamma}$-Al2O3 to $\alpha$-Al2O3 provided a homogeneity of the microstructure. The grain growth of Al2O3 are significantly surpressed by the addition of nano-size SiC particles. Dislocation were produced due to the difference of thermal expansion coefficient between Al2O3 and SiC and piled up on SiC particles in Al2O3 matrix, resulting in transgranular fracture. The high fracture strength of the composite was contributed to the grain refinement and the transgranular fracture mode. The addition of SiC platelets to Al2O3/SiC nano-composite decreased the fracture strength, but increased the fracture toughness. Coated SiC platelets with nitrides such as BN and Si3N4 enhanced fracture toughness much more than non-coated SiC platelets by enhancing crack deflection.

• Composites Research
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• v.36 no.2
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• pp.101-107
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• 2023

In this study, aluminum nitride (AlN) reinforced aluminum (Al) matrix composites are fabricated via plasma arc melting under a nitrogen atmosphere. Within a minute of the chemical reaction between Al and N, dispersed AlN with the shape of transient and lamellar layers is in situ formed in the Al matrix. The composite contains 10 vol.% AlN reinforcements with low thermal resistance and strong bonding at the interfaces, which leads to the unique combination of thermal expansivity and conductivity in the resulting composites. The coefficient of thermal expansion of the composite can be further reduced when Si was alloyed into the Al matrix, which proposes the potential of the in situ Al matrix composites for thermal management applications.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.9
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• pp.2374-2385
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• 1994

SiCw/Al composite material is especially attractive because of their superior specific strength, specific stiffness, corrosion fatigue resistance, creep resistance, and wear resistance compared with the corresponding wrought Al alloy. In this study, Fatigue crack growth behavior and fatigue crack path morphology(FCPM) of SiC whisker reinforced Al 6061 alloy with 25% SiC volume fraction and Al 6061 allay were performed. Result of the fatigue crack growth test sgiwed that fatigue crack growth rate of SiCw/Al 6061 composite was slower than that of Al 6061 matrix therefore it was confirmed that Sic whisker have a excellent fatigue resistance. And Al 6061 matrix had only FCPM perpendicular to loading direction. On the other hand SiCw/Al 6061 composite had three types in fatigue crack path morphology. First type is that both sides FCPM of artificial notch are perpendicular to loading direction. Second type is that a FCPM in artifical notch has slant angle to loading direction and the other side FCPM is perpendicular to loading direction. Third type is that both sides FCPM of notch have slant angle to loading direction. It was considered that this kinds of phenomena were due to non-uniform distribution of SiC whisker and confirmed by SEM observation for fracture mechanism study.

• Journal of the Korean Ceramic Society
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• v.30 no.4
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• pp.316-324
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• 1993

Three types of dispersed, coated and mechanically mixed SiC reinforced Al2O3 composite powders were used to investigate the effect of composite powder type on sintering characteristics and properties of Al2O3-SiC composites. Sinterability of coated type composite powders was superior to that of other composite powders when they were pressureless sintered at 1500~1$700^{\circ}C$ for 2h in Ar atmosphere. However, sinterabilities (>98% TD) of each type of composite powders were similar when they were hot pressed at 180$0^{\circ}C$ for 1h under 30MPa in N2 atmosphere. SiC powders were randomly distributed in the specimen prepared from dispersed type composite powders, whereas homogeneously distributed for coated type specimens. It was found that SiC powders inhibited the grain growth of Al2O3, and fracture toughness was increased by the increment of crack growth resistance due to residual stress by secondary SiC particles within Al2O3 grains.

• Korean Journal of Materials Research
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• v.15 no.11
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• pp.730-734
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• 2005

Cr-Al-Si-N coatings were deposited on WC-Co substrates by a hybrid coating system of arc ion plating and DC magnet :on sputtering technique in $N_2/Ar$ mixture. The Cr-tll-Si-N coatings were synthesized with different Si contents. Their microstructure and mechanical properties were systematically investigated. The average size of crystallites largely decreases with the increase of Si content compared with Cr-Al-N. The microhardness of Cr-Al-Si-N coatings largely increases from 24 to 55 GPa. The enhanced hardness is believed to originate from the microstructural change by the fine composite microstructure of Cr-Al-N coatings with Si addition. The average friction coefficient of Cr-Al-Si-N coatings decreases from 0.84 to 0.45 with increasing Si content up to $16\;at.\%$.

• Journal of the Korean Ceramic Society
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• v.33 no.1
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• pp.101-109
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• 1996

The mechanical propertieso f sintered AlN with the addition of alumina were investigated The flexural strength of the AlN dispersed ALON specimens was higher than that of ALON and fracture toughness showed similar tendency. The high-temperature flexural strength of specimens which 50 and 64.3 mol% alumina was added to AlN was constant up to 100$0^{\circ}C$ with about 290 and 420 MPa respectively but abruptly decreased at 120$0^{\circ}C$ In the specimens which contained 5 and 30mol% alumina the flexural strength increased to about 14% at 100$0^{\circ}C$ and did not decrease at 120$0^{\circ}C$ compared to at room temperature.