• 열처리공학회지
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• 제18권5호
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• pp.312-317
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• 2005

The precipitation process in Cu-0.2 wt.%Cr-0.05 wt.%Zr alloys has been studied by electrical electrical resistivity measurements. The kinetics of precipitation could be well described by Johnson-Mehl-Avrami equation, $f(t)=1-\exp(-kt^n)$. The values of n were found to be in the range of 0.36~0.42 at first stage and 1.3~1.6 at second stage. The activation energy was determined by cross-cut method and was 80~89 kJ/mol. The value is similar to the energy for the migration of either a vacancy or a vacancy-solute complex through the lattice.

• 한국재료학회지
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• 제4권8호
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• pp.906-914
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• 1994

상온과 액체질소온도에서 압축시험을 통하여 $LI_{2}$단상함금 및 $LI_{2}$상에 제 2상을 수 %또는 20%정도 포함하는 합금조성을 선택하였다. 일반적으로 제 2상을 20%정도 포함하는 2상합금들은 $Ll_{2}$단상합금에 비해 항복강도는 높으나 연성은 좋지 않았다. 그러나 $Cr_{2}AI$을 제 2상으로하는 20%정도 포함하는 Al-21Ti-23Cr합금은 다른 합금들에 비해 비교적 높은 항복강도와 함계 우수한 연성을 나타내었다. 또한 $Li_{2}$단상합금 및 $Cr_{2}Al$을 수% 포함하는 2상합금에 대한 소성거동도 조사하였다. 균질화처리 후에 제 2상의 양은 줄었으나 pore의 양은 증가하였다. 균질화처리 후에 $Ll_{2}$단상조직에서 나타나는 pore의 양은 Cr의양이 증가할수록 줄어들었으며, Cr 의 양이 더욱 증가하여 $Cr_{2}$Al이 제2상으로 생성될 때는 pore가 완전히 소멸하였다. 변형속도를 $1.2 \times 10^{-4}/s$와 $1.2 \times 10^{-2}/s$의 두가지 조건으로 변화시키면서 압축시험을 행하여 합금의 연성에 미치는 환경취성의 영향을 조사하였다. $LI_{2}$단상합금인 AI-25Ti-10Cr합금이 환경취성의 영향을 가장 적게 받는 것으로 나타났다. 그러나 pore의 생성, 환경취성, ingot 주조조직 등을 종합평가해 보면 $Cu_{2}Al$을 제 2상으로 20%정도 포함하는 Ak-21Ti-23Cr합금이 가장 우수한 인장연싱율을 나타낼 것으로 기대된다.

• 대한기계학회논문집A
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• 제30권6호
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• pp.670-677
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• 2006

Vacuum interrupters are used in various switch-gear components such as circuit breakers, distribution switches, contactors. The electrodes of a vacuum interrupter are manufactured of sinter-forged Cu-Cr material for good electrical and mechanical characteristics. Since the closing velocity is 1-2m/s and impact deformation of the electrode depends on the strain-rate at the given velocity, the dynamic material property of the sinter-forged Cu-Cr alloy is important to design the vacuum interrupter reliably and to identify the impact characteristics of a vacuum interrupter accurately. This paper is concerned with the dynamic material properties of sinter-forged Cu-Cr alloy for various strain rates. The amount of chrome is varied from 10 wt% to 30 wt% in order to investigate the influence of the chrome content on the dynamic material property. The high speed tensile test machine is utilized in order to identify the dynamic property of the Cu-Cr alloy at the intermediate strain-rate and the split Hopkinson pressure bar is used at the high strain-rate. Experimental results from both the quasi-static and the high strain-rate up to the 5000/sec are interpolated with respect to the amount of chrome in order to construct the Johnson-Cook and the modified Johnson-Cook model as the constitutive relation that should be applied to numerical simulation of the impact behavior of electrodes.

• 한국재료학회지
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• 제11권5호
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• pp.405-412
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• 2001

본 연구에서는 $360^{\circ}C$ 물 및 $360^{\circ}C$, 70ppm LiOH 수용액 분위기의 static autoclave를 이용하여 새롭게 개발한 Zr 신합금 (Zr-0.4Nb-0.8Sn-xFeCrMn, Zr-0.2Nb-1.1Sn-xFeCrMn, Zr-1.0Nb-xFeCu) 의 부식 특성을 평가하였다. 합금의 미세구조를 광학현미경과 TEM을 이용하여 관찰하였고, 부식시험 중에 생성된 산화막은 SEM과 XRD를 이용하여 단면 및 결정구조를 조사하였다. 부식시험 결과, 3종의 합금 모두 $360^{\circ}C$ 물 분위기보다 $360^{\circ}C$, 70ppm LiOH 수용액 분위기에서의 부식저항성이 감소하였으며 특히, High Nb 합금의 경우 급격한 가속 부식현상을 나타내었다. 합금원소 첨가량과 관련하여 Nb의 함량을 고용도 이내로 줄이고 Sn을 적절히 첨가한 조성의 합금이 Sn을 첨가하지 않고 고용도 이상의 Nb을 가진 합금보다 우수한 부식저항성을 나타내었다. 또한 최종열처리가 부식에 미치는 영향의 경우에, 완전재결정 조직의 합금이 부분재결정 조직을 가진 합금보다 부식저항성이 감소되었는데 이는 기지조직에서 석출하늘 제 2상의 크기 및 분포에 의한 영향으로 사료된다.

• 대한치과기공학회지
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• 제7권1호
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• pp.13-18
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• 1985

Casting alloys, both precious and non-precious, were by heat in order to observe the change in HB and the results were : 1. The hard treatment showed 1.4 - 1.5 times as high as the soft treatment in HB. 2. The experiment shows that Au-Pt should be contained more than 75% to prevent color change. 3. Cu by hard teatment played the greatect part in creasing the solidity of Ag-Cu alloy. 4. Casting Co-Cr alloys showed little difference of HB in heat treatment.

• 한국재료학회지
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• 제28권6호
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• pp.317-323
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• 2018

Crystal structure of the $L1_2$ type $(Al,X)_3Ti$ alloy (X = Cr,Cu) is analyzed by X-ray diffractometry and the nonuniform strain behavior at high temperature is investigated. The lattice constants for the $L1_2$ type $(Al,X)_3Ti$ alloys decrease in the order of the atomic number of the substituted atom X, and the hardness tends to increase. In a compressive test at around 473K for $Al_{67.5}Ti_{25}Cr_{7.5}$, $Al_{65}Ti_{25}Cr_{10}$ and $Al_{62.5}Ti_{25}Cu_{12.5}$ alloys, it is found that the stress-strain curves showed serration, and deformation rate dependence appeared. It is assumed that the generation of serration is due to dynamic strain aging caused by the diffusion of solute atoms. As a result, activation energy of 60-95 kJ/mol is obtained. This process does not require direct involvement. In order to investigate the generation of serrations in detail, compression tests are carried out under various conditions. As a result, in the strain rate range of this experiment, serration is found to occur after 470K at a certain critical strain. The critical strain increases as the strain rate increases at constant temperature, and the critical strain tends to decrease as temperature rises under constant strain rate. This tendency is common to all alloys produced. In the case of this alloy system, the serration at around 473K corresponds to the case in which the dislocation velocity is faster than the diffusion rate of interstitial solute atoms at low temperature.

• 한국신뢰성학회:학술대회논문집
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• 한국신뢰성학회 2002년도 정기학술대회
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• pp.117-120
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• 2002

The addition of minor alloying elements such as Al, Si, Mg, Cr, Zr, and Sn changed the microstructure and the oxidation characteristics of the Cu-40%Zn alloys. Detailed microstructure, scale morphology and the oxidation mechanism were described.

• Corrosion Science and Technology
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• 제11권6호
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• pp.263-269
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• 2012

Copper alloys are commonly applied to ship's propellers, pumps and valves which are serviced in seawater due to their good castability and corrosion resistance. In the environment of high flow velocity, however, erosion damage predominates over corrosion damage. In particular, the cavitation in seawater environment accelerates surface damage to copper alloys, resulting in degradation of products and economic losses and also threatening safety. The surface was coated with WC-27NiCr by high velocity oxygen fuel(HVOF) spraying technique to attain durability and cavitation resistance of copper alloys under high velocity/pressure flow. The cavitation test was performed for the WC-27NiCr coating deposited by HVOF in seawater at the amplitude of $30{\mu}m$ with seawater temperature. The cavitation at $15^{\circ}C$ caused exfoliation of the coating layer in 17.5 hours while that of $25^{\circ}C$ caused the exfoliation in 12.5 hours. When the temperature of seawater was elevated to $25^{\circ}C$ from $15^{\circ}C$, more damage was induced by over 160%. Although WC-27NiCr has good durability, corrosion resistance and eletrochemical stability, the cavitation damage rate of the coating layer could remarkably increase at the elevated temperatures under cavitation environments.

• 한국전기전자재료학회논문지
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• 제34권1호
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• pp.50-55
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• 2021

Copper-chromium alloys have been used as contact materials of vacuum interrupters in circuit breakers, but new materials with highly stable performance are required to break the high voltage and high current barrier due to the recent increase in breaking capacity. In this paper, a new contact material was fabricated from a ternary alloy instead of existing Cu-Cr alloys. Its breaking performance and endurance were verified from a synthetic test and compared with that of various contact materials. The test results verified that the breaking performance of the new contact material was excellent.

• 한국마이크로전자및패키징학회:학술대회논문집
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• 한국마이크로전자및패키징학회 2003년도 기술심포지움 논문집
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• pp.84-87
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• 2003

Since Pb-free solder alloys have been used extensively in microelectronic packaging industry, the interaction between UBM (Under Bump Metallurgy) and solder is a critical issue because IMC (Intermetallic Compound) at the interface is critical for the adhesion of mechanical and the electrical contact for flip chip bonding. IMC growth must be fast during the reflow process to form stable IMC. Too fast IMC growth, however, is undesirable because it causes the dewetting of UBM and the unstable mechanical stability of thick IMC. UP to now. Ni and Cu are the most popular UBMs because electroplating is lower cost process than thin film deposition in vacuum for Al/Ni(V)/Cu or phased Cr-Cu. The consumption rate and the growth rate of IMC on Ni are lower than those of Cu. In contrast, the wetting of solder bumps on Cu is better than Ni. In addition, the residual stress of Cu is lower than that of Ni. Therefore, the alloy of Cu and Ni could be used as optimum UBM with both advantages of Ni and Cu. In this paper, the interfacial reactions of Sn-3.5Ag-0.7Cu solder on Ni-xCu alloy UBMs were investigated. The UBMs of Ni-Cu alloy were made on Si wafer. Thin Cr film and Cu film were used as adhesion layer and electroplating seed layer, respectively. And then, the solderable layer, Ni-Cu alloy, was deposited on the seed layer by electroplating. The UBM consumption rate and intermetallic growth on Ni-Cu alloy were studied as a function of time and Cu contents. And the IMCs between solder and UBM were analyzed with SEM, EDS, and TEM.