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Vol.41, No.9, 539 ~ 551, 2003
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| Title |
| Hot Deformation and Thermal Expansion Behavior of Fe-Ni-Co Low Thermal Expansion Alloy |
| 이기안 Lee Gi An , 박종혁 Park Jong Hyeog , 조봉현 Jo Bong Hyeon , 남궁정 Nam Gung Jeong , 김문철 Kim Mun Cheol |
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| Abstract |
| The high temperature deformation behavior and the effect of hot compression on the thermal expansion behavior of Fe-29Ni-17Co low thermal expansion Kovar alloy were investigated in the compressive temperature range of 900~1300℃ at the strain rate range of 25~0.01 sec.^(-1). The temperature (T) and strain rate (ε˙) dependence of the flow stress (σ_(0.7)) could be well described by hyperbolic sine law as ε˙= A [sinh(0.0084 σ)^(5.2018)] exp(-330.41/RT). Surface hot cracking and significant voids around grain boundary could be found at low temperature below 1000℃ and low strain rate (0.01 sec.^(-1)). Thermal expansion coefficient α_(30~400) generally increased with increasing compressive temperature. Moreover, α_(30~400) remarkably increased as strain rate decreased at high temperature above 1100℃. However the thermal expansion coefficient α_(30~400) of low compressive temperatures (900℃ and 1000℃) anomalously increased especially at high strain rates. Experimental results indicated that not only α phase appearance but also grain size had definite influence on the thermal expansion behavior with hot deformation. The correlation between microstructure and thermal expansion behavior of Kovar alloy were also discussed. |
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| Key Words |
| Kovar, Hot compression, Zener-Holloman parameter, Low thermal expansion, Grain size, α phase |
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