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β-열처리시 Nb 첨가량과 냉각속도가 Zr 합금의 상변태에 미치는 영향
최병권 ( B. K. Choi ),김현길 ( H. G. Kim ),정용환 ( Y. H. Jeong ) 한국열처리공학회 2004 熱處理工學會誌 Vol.17 No.5
N/A Zr-xNb alloys (x = 0.2, 0.8, 1.5 wt.%) were prepared to study the characteristics of the phase transformation in Zr-Nb system. The samples were heat treated at 0-temperature (1020℃) for 20 min and then cooled with different cooling rate. The microstructures of the specimens having the same compositions were changed with cooling rate and Nb content. The Widmanstatten structure was observed on the furnace-cooled sample. The relationship between α-Widmansta¨tten and β-phase was the {0001}α//{110}β, <112 ̄0>//<111>. The β-phase in Widmansta¨tten structure of Zr-Nb alloys containing Nb more than solubility limit was identified as β_(zr) phase which was a stable phase at high temperature. In the water quenched samples, two kinds of martensite structures were observed depending on the Nb-concentration. The lath martensite was formed in Zr-0.2, 0.8 wt.% Nb alloys and the plate martensite having twins was formed in Zr-1.5 wt.% Nb alloy.
Nb 첨가 Zr 합금의 열처리 조건에 따른 LiOH 용액에서의 부식특성 연구
김현길,정용환,김도훈 대한금속재료학회(대한금속학회) 2000 대한금속·재료학회지 Vol.38 No.5
In order to develop the new zirconium alloys for cladding materials, the effects of Nb addition and the final heat treatment on the microstructure and corrosion characteristics of Zr-xNb(x = 0.2, 1.0 wt.%) alloys were investigated. The 1.0Nb alloy showed higher corrosion resistance than 0.2Nb alloy at 360℃, 70 ppm LiOH solution. The microstructure of oxide films that having equal oxide thickness has been characterized by TEM. The oxide of 1.0Nb alloy was mainly composed of columnar grains but the oxide of 0.2Nb alloys was mainly composed of equiaxed grains. From the XRD analysis of equal oxide thickness, the oxide of 1.0Nb alloy has higher tetra-ZrO₂ volume fraction than 0.2Nb alloys. Also when hydrogen pick-up content and fraction were measured with the corroded specimens of 0.2, 1.0Nb alloy at pre and post transition region, the hydrogen pick-up content and fraction were lower in 1.0Nb than 0.2Nb alloy. From the final heat treatment effect, the 1.0Nb alloy was affected annealing temperature but the 0.2Nb alloy was not.
핵연료 피복관용 Zircaloy-4 및 Zr-Nb 합금의 열처리에 따른 부식 및 기계적 특성 평가
김현길,정용환,이명호,윤영균 대한금속재료학회(대한금속학회) 2000 대한금속·재료학회지 Vol.38 No.7
Effects of final annealing temperature on the corrosion and mechanical behavior, and microstructure were investigated for Zircaloy-4(Zr-1.3Sn-0.2Fe-0.1Cr), Alloy-1(Zr-0.4Nb-0.6Sn-0.4Fe-0.2Cu) and Alloy-2(Zr-1Nb). The corrosion tests were carried out in 360℃ water and 70 ppm LiOH solution in the static mini autoclaves. The mechanical tests were performed using the universal material test machine. The corrosion rate of Zircaloy-4 was not accelerated as the precipitates on Zircaloy-4 grew with the increase of annealing temperature after recrystallization. But the corrosion rate of Alloy-1 and 2 was accelerated due to the formation and growth of β-Zr phases with increasing the annealing temperature. Therefore, the corrosion resistance of the Zr-Nb alloy system could be improved by the control of heat treatment. It was also confirmed that the mechanical properties of Zr-based alloys were affected by the addition of alloying elements, the recrystallization, and the precipitation with annealing temperature.
Zr 합금의 석출물 및 부식특성에 미치는 Fe 와 Mn 첨가 영향
김현길,위명용,정용환,이명호,박상윤 대한금속재료학회(대한금속학회) 1999 대한금속·재료학회지 Vol.37 No.11
In order to Investigate the effects of Fe and Mn on the precipitate and corrosion characteristics of Zr based alloys for nuclear fuel cladding, autoclave corrosion tests on the ternary(Zr-0.8Sn-X) alloys have been carried out at 360℃. The corrosion behavior of Zr-Sn-Fe alloy showed the cubic corrosion rate in the pre-transition region and the linear corrosion rate in the post-transition region. The good corrosion resistance in Zr-Sn-Fe alloy system was observed in Fe contents more than 0.2 wt%. The corrosion behavior of Zr-Sn-Mn alloy was significantly accelerated from the early stage. The lowest weight gain was observed in 0.2 wt% Mn. Based on the precipitate anallysis by TEM, it is thought that the corrosion of Zr-alloys would be related to the size of precipitate.