• 한국분말재료학회지
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• 제18권4호
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• pp.359-364
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• 2011

Zr-Ti alloy powders were successfully synthesized by magnesium thermal reduction of metal chlorides. The evaporated and mixed gasses of $ZrCl_4+TiCl_4$ were injected to liquid magnesium and the chloride components were reduced by magnesium leading to the formation of $MgCl_2$. The released Zr and Ti atoms were then condensed to particle forms inside the mixture of liquid magnesium and magnesium chloride, which could be dissolved fully in post process by 1~5% HCl solution at room temperature. By the fraction-control of individually injected $ZrCl_4$ and $TiCl_4$ gasses, the final compositions of produced alloy powders were changed in the ranges of Zr-0 wt.%~20 wt.%Ti and their purity and particle size were about 99.4% and the level of several micrometers, respectively.

• 비파괴검사학회지
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• 제30권4호
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• pp.324-329
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• 2010

원자력발전소에서 사용되고 있는 연료봉은 지르코늄 합금 튜브에 동봉되어 있는 이산화우라늄 펠릿으로 구성되어 있다. 펠릿 표면은 원자로를 가동시키는 동안 국부 핫스팟을 예방하기 위해 튜브로 장전된 후 작은 구멍, 균열, 칩핑 결함이 없어야 한다. 본 논문은 X-선 단층촬영 시뮬레이션을 통하여 핵 연료봉 펠릿의 표면 결함을 검출하기 위한 타당성을 조사하였다. 병렬과 팬빔 여과후 역투영 방법을 이용하여 재구성된 영상은 시뮬레이션 데이터와 MPS(missing pellet surface) 영상데이터의 접근성을 확인하였다.

• 한국주조공학회지
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• 제30권6호
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• pp.217-223
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• 2010

Foamed metal has become an attractive material, which has unique physical, thermal, acoustic, damping and mechanical properties, because large amount of pores are distributed in the metal matrix. Therefore, metal foam can be used for the light weight application in automotive, locomotive, aerospace fields. Aluminum foams have been developed successfully and will be employed in the next generation of energy absorption boxes. Magnesium alloys are most eligible candidate to substitute aluminum alloy, especially for lower density and higher damping properties in wide industrial fields. Magnesium alloy foams are expected to be particularly advantageous due to two thirds the density of aluminum. However, foaming magnesium have been weakness of high activity, difficult processing and very dangerous. In order to upgrade this problem, AM50 magnesium alloy which has better characteristic is safe to use through foaming time and alloying element in this study.

• 한국수소및신에너지학회논문집
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• 제15권4호
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• pp.266-273
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• 2004

The objective of this study is an understanding of stress corrosion cracking of metals that is recognized to mostly limit the lifetime of the structural materials by comparing the features of delayed hydride cracking of zirconium alloys with those of stress corrosion cracking (SCC) of Ni-based alloys and hydrogen cracking of stainless steels. To this end, we investigated a dependence of delayed hydride cracking (DHC) velocity on the applied stress intensity factor and yield strength, and correlated a temperature dependence of the striation spacing and the DHC velocity. We reviewed a similarity of the features between the DHC of zirconium alloys, the SCC of Ni-based alloys and turbine rotor steels, and the hydrogen cracking of stainless steels and discussed the SCC phenomenon in metals with our DHC mode.

• 한국재료학회지
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• 제25권8호
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• pp.376-385
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• 2015

The effects of Nb and Cr addition on the microstructure, corrosion and oxide characteristics of Zr based alloys were investigated. The corrosion tests were performed in a pressurized water reactor simulated-loop system at $360^{\circ}C$. The microstructures were examined using OM and TEM, and the oxide properties were characterized by low-angle X-ray diffraction and TEM. The corrosion test results up to 360 days revealed that the corrosion rates were considerably affected by Cr content but not Nb content. The corrosion resistance of the Zr-xNb-0.1Sn-yCr quaternary alloys was improved by an increasing Nb/Cr ratio. The crystal structure of the precipitates was affected by a variation of the Nb/Cr ratio. The Zr-Nb beta-enriched precipitates were mainly formed in the high Nb/Cr ratio alloy while $Zr(NbCr)_2$ precipitates were frequently observed in the low Nb/Cr ratio alloy. The studies of oxide characteristics revealed that the corrosion resistance was related to the crystal structure of the precipitate.

• 대한기계학회논문집A
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• 제28권2호
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• pp.189-195
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• 2004

The pressure tubes, which contain high temperature heavy water and fuel, are within the core of a CANDU nuclear reactor, and are thus subjected to high stresses, temperature gradient, and neutron flux. Further, it is well known that pressure tubes of cold-worked Zr-2.5Nb materials result in hydrogen diffusion, which create fully-hydrided regions (frequently called Blister). Thus a proper investigation of hydrogen diffusion within zirconium-alloy nuclear components, such as CANDU pressure tube and fuel channels is essential to predict the structural integrity of these components. In this respect, this paper presents numerical investigation of hydrogen diffusion to quantify the hydrogen concentration fur blister growth of CANDU pressure tube. For this purpose, coupled temperature-hydrogen diffusion analyses are performed by means of two-dimensional finite element analysis. Comparison of predicted temperature field and blister with published test data shows good agreement.

• 자원리싸이클링
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• 제26권6호
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• pp.3-9
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• 2017

본 연구에서는 anode로 Kroll 공정 처리된 Ti 스폰지를 사용하여 아크 전류, 아크 전압, 플라즈마 가스 종류에 따른 플라즈마 아크 재용해 거동을 조사하였다. 진공펌프의 토출 압력 범위($200{\sim}300kgf/cm^2$)에서는 토출 압력 증가에 따라 주어진 아크 길이에서 아크 전압이 크게 달라지지 않았다. 이것은 작업하는 동안 진공챔버내 압력이 거의 변화하지 않고, 주어진 분위기 압력을 잘 유지함을 의미한다. 여러가지 아크 전류 조건(700~900A)에서, 아크 전류 증가에 따라 아크 전압이 약간 증가하였고, anode 재료변화에 대한 효과도 이전 연구결과와 비교하였다. 분위기 가스가 Ar에서 He으로 변경되는 경우에는 정상상태의 출력이 2배 정도 향상되는 효과가 관찰되었다. 플라즈마 아크 장치의 출력 증가는 Ti 스폰지의 재용해 속도 증가와 함께 잉곳 표면도 양호해졌다. New 스크랩인 타이타늄과 old 스크랩인 지르코늄 합금을 플라즈마 아크 재용해한 결과, 매우 양호한 표면을 갖는 잉곳을 제조할 수 있었다.

• 비파괴검사학회지
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• 제23권4호
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• pp.342-348
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• 2003

Zr(1.32mm) 판재 위 $Be-Zr(100{\mu}m)$ 합금층의 평가를 목적으로 후방산란 초음파 의 입사각 의존성인 프로파일이 여러 입사위치에서 측정되었다. 누설 램(Lamb)파로부터 후방복사된 초음파 프로파일에는 4개의 주요 세부 프로파일이 발견되었다. 세부프로파일들의 정점각과 정점세기는 Be 확산층의 강화효과로 인해 감소하였다. 세부 프로파일들의 존재와 변화가 시편재질의 음향학적 특성, 램파모드들의 군속도 집단적 변화 그리고 표면파의 누설율 차이 등으로 설명되었다 판재 위 얇은 확산층의 평가를 위한 유용한 평가 기법으로 판재로부터의 후방복사 세부 프로파일이 제안되었다.

• 한국재료학회지
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• 제18권11호
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• pp.597-603
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• 2008

Oxide effects experiments on massive hydriding reactions of Zr alloy with hydrogen gas were carried out at $400^{\circ}C$ under 1 atm in a $H_2$ environment with a thermo-gravimetric apparatus (TGA). Experimental results for oxide effects on massive hydriding kinetics show that incubation time is not proportional to oxide thickness. The results also show that the massive hydriding kinetics of pre-filmed Zr alloys follows linear kinetic law and that the hydriding rates are similar to that of oxide-free Zr alloys once massive hydriding is initiated. Unlikely microstructure of the oxide during incubation time, physical defects such as micro-cracks and pores were observed in the oxide after incubation time. Therefore, it seems that the massive hydriding of Zr alloys can be ascribed to short circuit paths and mechanical or physical defects, such as micro-cracks and pores in the oxide, rather than to hydrogen diffusion through the oxide resulting from the increase of oxygen vacancies in the hypo-stoichiometric oxide.

• 한국세라믹학회지
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• 제47권2호
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• pp.106-112
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• 2010

This paper presents some experimental results on incubation time for massive hydriding of Zr alloys with oxide thickness. Oxide effects experiments on massive hydriding reaction of commercial Zr alloy claddings and pre-oxidized Zr alloys with hydrogen gas were carried out in the temperature range from 300 to $400^{\circ}C$ with thermo-gravimetric apparatus. Experimental results for oxide effects on massive hydriding kinetics show that incubation time is not proportional to oxide thickness and that the massive hydriding kinetics of pre-filmed Zr alloys follows linear kinetic law and the hydriding rate are similar to that of oxide-free Zr alloys once massive hydriding is initiated. There was a difference in micro-structures between oxide during incubation time and oxide after incubation time. Physical defects such as micro-cracks and pores were observed in only oxide after incubation time. Therefore, the massive hydriding of Zr alloys seems to be ascribed to short circuit path, mechacical or physical defects, such as micro-cracks and pores in the oxide rather than hydrogen diffusion through the oxide resulting from the increase of oxygen vacancies in the hypostoichiometric oxide.