• 한국재료학회지
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• 제16권8호
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• pp.511-515
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• 2006

The dispersion hardened $Cu-TiB_2$ composites are a promising candidate for applications as electrical contact materials. The $Cu-TiB_2$ composites for electrical contact materials can reduce material cost and resource consumption caused by wear, due to their good mechanical and electrical properties. In this study, we investigated the wear phenomenon for $Cu-TiB_2$ composites fabricated with hot extrusion, by varying particle sizes and volume fractions of $TiB_2$. The wear tests were performed under the dry sliding condition with a fixed total sliding distance of 40 m. The contact loads at a constant speed of 3.5 Hz were 20, 40, 60, and 80 N. The friction coefficients and wear losses were measured during wear tests. Worn surfaces and wear debris after wear tests were investigated using the scanning electron microscope and the optical microscope. The microstructures of interface between Cu matrix and $TiB_2$ particle before and after wear tests were studied by the transmission electron microscope.

• 한국재료학회지
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• 제14권1호
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• pp.73-77
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• 2004

The mechanical and electrical properties of $Cu-TiB_2$ composites prepared by hot extrusion and cold drawing according to the variation of $TiB_2$ contents and the size of $TiB_2$ particle have been studied. The experimental results showed that the electrical conductivity was decreased with increasing the $TiB_2$ content, and their tensile strength and hardness increased inversely. In the case of the same content of $TiB_2$ particle, the smaller $TiB_2$ particle, the higher their mechanical properties. The electrical conductivity of $Cu-TiB_2$ composites showed more than 70%IACS. Their yield strength and hardness were more than 120 MPa and HRB 60～70, respectively.

• 한국재료학회지
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• 제15권12호
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• pp.824-828
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• 2005

In this study the effect of the content of $TiB_2$ on wear properties was investigated. $Cu-TiB_2$ composites have been fabricated by hot extrusion. Sliding wear tests were peformed by a pin-on-disk type wear test machine under dry condition and loads varied with from 20N to 80N at sliding speed 3.5Hz. The test results showed that the wear losses and the friction coefficients decreased with increasing $Cu-TiB_2$ volume fraction and increasing the size of $Cu-TiB_2$ particle. Wear property of $10{\mu}m,\;5 vol\%\; TiB_2$ specimen was excellent all of the wear specimens. It is thought that the increase of plastic flow resistivity due to uniform distribution of $10{\mu}m,\;5 vol\%\; TiB_2$ wear specimen would improve wear property. The worn surface and wear debris were examined by optical microscope and scanning electron microscope.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2004년도 추계학술대회 논문집
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• pp.704-709
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• 2004

The wear behavior and the mechanical property of Cu-$TiB_2$ composites were examined. Cu-$TiB_2$ composites were fabricated by hot extrusion and cold drawing with $TiB_2$ contents(1$\∼$5vol.$\%$) and the size of $TiB_2$ particles(10$\mu$m and 20$\mu$m). The pin-an-disk wear test was carried out under dry sliding wear conditions which loads varied with from 20N to 100N. At the time, counterpart wear material used SM45C. The experimental results showed that the friction coefficient and wear rate decreased with increasing the $TiB_2$ contents and decreasing the size of $TiB_2$ particle. Also, the depth of plastically deformed zone decreased with increasing the $TiB_2$ contents and decreasing the size of $TiB_2$ particle.

• Composites Research
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• 제19권2호
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• pp.28-34
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• 2006

고온자전합성법과 스파크 플라즈마 소결법으로 여러 가지 $TiB_2$ 함유량을 갖는 $Cu-TiB_2$ 금속복합재료를 제조하였다. 점용접 전극과 미끄럼 접촉재로 사용하기 위해 인장특성, 경도, 마모저항 등의 물성치를 조사하였다. 강화재의 형상, 크기, 부피분율 등에 의해 복합재료의 특성이 달라지므로 유효물성치를 예측하기 위한 모델링이 필수적이다. 유한요소해석결과 유효탄성 계수가 실험치와 일치하는 것을 확인하였고 Eshelby 모델, Mori-Tanaka의 평균장 이론이 결합된 Eshelby 모델, 혼합법칙 등으로 복합재료의 탄성계수를 예측한 결과 Mori-Tanaka의 평균장 이론이 결합된 Eshelby 모델이 실험치를 사장 잘 묘사하는 것으로 나타났다.

• 한국재료학회지
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• 제15권12호
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• pp.809-813
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• 2005

A copper matrix composite reinforced by turbulent in-situ $TiB_2$ nanoparticle was Prepared by reactions of boron ana titanium. The microstructure, mechanical and electrical properties of the as-drawn composites were investigated. The results showed that the formed $TiB_2$ particles, which had a size of about from 50 to 200nm, exhibited a homogeneous dispersion in the copper matrix. Due to their reinforcement, the hardness and Young's modulus of $Cu-TiB_2$ composites were enhanced with increasing the cooling rate. Moreover, the electrical conductivity of the composites were improved with increasing the cooling rate.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2005년도 춘계학술발표대회 및 제8회 신소재 심포지엄 논문개요집
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• pp.286-286
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• 2005

• 한국재료학회지
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• 제15권1호
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• pp.61-65
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• 2005

The titanium $diboride(TiB_2)$ has high strength(750MPa), high melting point $(3225^{\circ}C)\;and\;10\%$ IACS electrical conductivity. On this account, the dispersion hardening $Cu-TiB_2$ composites(MMCs) are a promising candidate for applications as electrical contact materials. MMCs for electrical contact materials can reduce material cost and resource consumption caused by wear, due to its good mechanical and electrical property. In this study, we attempt to prepare MMCs with various volume fraction and particle size of $TiB_2$ by means of hot extruded and cold drawn process. Dry sliding wear tests were performed on a pin-on-disk type wear tester, sliding against SM45C under the different applied loads. After wear testing, the microstructures of the worn surfaces were observed by SEM and the microhardnesses of the subsurface zone were measured.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part2
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• pp.1203-1204
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• 2006

Cu-$TiB_2$ nanocomposite powders were synthesized by combining high-energy ball-milling of Cu-Ti-B mixtures and subsequent self-propagating high temperature synthesis (SHS). Cu-40wt.%$TiB_2$ powders were produced by SHS reaction and ball-milled. The milled SHS powder was mixed with Cu powders by ball milling to produce Cu-2.5wt.%$TiB_2$ composites. $TiB_2$ particles less than 250nm were formed in the copper matrix after SHS-reaction. The releative density, electrical conductivity and hardness of specimens sintered at $650-750^{\circ}C$ were nearly 98%, 83%IACS and 71HRB, respectively. After heat treatment at 850 to $950^{\circ}C$ for 2 hours under Ar atmosphere, hardness was descedned by 15%. Our Cu-$TiB_2$ composite showed good thermal stability at eleveated temperature.

• 한국분말재료학회지
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• 제10권3호
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• pp.168-171
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• 2003

Interpenetrating phase composites of $TiB_2$-Cu system were produced via Spark-Plasma Sintering (SPS) oi nanocomposite powders. Under simultaneous action of pressure, temperature and electric current titanium diboride nanoparticles distributed in copper matrix move, agglomerate and form a fine-grained skeleton. Increasing SPS-temperature and he]ding time promote densification due to local melting of copper matrix When copper melting is avoided the compacts contain 17-20% porosity but titanium diboride skeleton is still formed representing the feature of SPS . High degree of densification and formation of titanium diboride network result in increased hardness of high-temperature SPS-compacts.