Korean Journal of Materials Research, Vol.11, No.2, 104-114, February, 2001
Nb과 Sn 첨가에 따른 Zr 합금의 재결정 및 TEP 거동
Recrystallization TEP Behavior of Zr-based alloy by addition of Nb and Sn
초록
Zr-Sn-Nb 합금의 재결정에 미치는 Nb과 Sn의 첨가영향을 연구하기 위해 냉간압연한 시편을 300 ? C ~75 0 ? C 의 온도구간에서 열처리한 후에 미소경도와 TEP (Thermoelectric Power)를 측정하여 재결정 거동을 조사하였으며 광학현미경, 주사전자 현미경 (SEM), 투과전자현미경 (TEM)으로 미세조직을 관찰하였다 미소경도 및 미세조직의 분석 결과에 따르면, Nb과 Sn의 첨가에 의해 재결정 활성화 에너지가 증가하여 재결정이 지연되었으며, 재결정 완료 이후의 결정립 성장도 억제되었음을 관찰하였다. Zr내의 고용도가 매우 낮은 Nb의 첨가는 석출물을 쉽게 형성하는 반면에 고용도가 비교적 큰 Sn은 기지상 내에 대부분 고용되어 석출물의 양이 매우 작았으나, Sn 첨가에 의한 재결정의 지연 효과가 더욱 컸다. Nb보다 Sn의 첨가가 Zr 합금의 재결정 거동을 효과적으로 지연시킨 것은 고용도가 높은 SR에 의한 치환형 고용체 형성과정에서 발생된 응력장이 전위의 이동을 효과적으로 억제했기 때문으로 생각된다. 한편, 회복과 재결정이 진행됨에 따라 전자 산란인자의 감소로 TEP는 증가하였으며, 재결정이 완료되면 TEP의 포화가 발생하였다. 석출물의 형성은 석출물 주변의 용질농도 감소로 인한 전자 산란인자의 감소에 기인하여 TEP의 증가를 가져왔다.
To investigate the effects of the addition of Nb and Sn on the recrystallization of Zr- Sn-Nb alloys, both Vickers micro-hardness test and TEP measurement were carried out on cold-worked specimens annealed at various temperatures from 300 ? C to 75 0 ? C . The microstructures of heat treated specimens were analyzed by optical microscope, SEM, and TEM. The study of microhardness and microstructures showed that both recrystallization process and grain growth were retarded as the activation energy was increased by the addition of Nb and Sn. Especially, the addition of Sn was more effective on retarding recrystallization. Precipitates were formed more easily when Nb was added because the solubility of Nb into Zr is lower than that of Sn. However, the recrystallization process was affected more by Sn than Nb because the strain field formed by substitutional Sn repressed the dislocation movement. TEP was increased due to the decrease of electron scattering as recovery and recrystallization were proceeded and saturated when the recrystallization completed. However, when precipitates formed, TEP was increased because the decrease of solute concentration near the precipitates caused the decrease of electron scattering.
- Joeng YH, et al., KAERI report RR-1580/95 (1995) (1995)
- Garzarolli F, Schumann R, Steinberg E, 'Corro-sion of Optimized Zircaloy for BWR fuel elements', ASTM STP 1245, 709 (1994) (1994)
- Sano N, Takeda K, J. Nucle. Mat., 252, 63 (1998)
- Isobe T, Matsu Y, 'Development of Highly Corrosion Resistant Zirconium-Based Alloys', ASTM STP 1132, (1991) (1991)
- Cotterill P, Mould PR, Recrystallization and Grain Growth in Metals, 15 (1976)
- Charquet D, Hahn R, Ortlieb E, Gross JP, Wadier JF, ASTM STP, 1023, 405 (1988)
- Nes E, 'Recrystallization and Grain Growth of Multi-Phase and Particle Containing Materials', Proceeding of the 1st international symposium on metallurgy and materials science, 93 (1980) (1980)
- Versaci RA, Ipohorski M, J. Nucl. Mat., 116, 321 (1983)
- Jeong YH, Korean J. Mater. Res., 6(6) (1996)
- Chandra T, Weiss I, Jonas JJ, Metallurgical Science, 10, 97 (1982)
- Chandra T, Weiss I, Jonas JJ, Can. Metall. Quart., 20, 421 (1981)
- Haessner F, Hornbogen E, Mukherjee M, Z. metallkunde, 57, 270 (1966)
- Porter DA, Easterling KE, Phase Transforma-tion in Metals and Alloys, 46 (1981)
- Cahn RW, Davis RG, Phil. Mag., 5, 1119 (1960)
- NEY JOSE LUIGGI, Metall. Mater. Trans. B, 28B, 125 (1997)