| Title |
Effects of Cold Working and Heat Treatment on the Thermal Expansion Property of Fe-29%Ni-17%Co Low Thermal Expansion Alloy |
| Authors |
이기안(Kee Ahn Lee); 권진한(Jin Han Gwon); 박종혁(Jong Hyuk Park) |
| DOI |
https://doi.org/10.3365/KJMM.2015.53.1.66 |
| ISSN |
1738-8228(ISSN), 2288-8241(eISSN) |
| Keywords |
alloys; cold working; microstructure; X-ray diffraction; low thermal expansion |
| Abstract |
The changes to thermal expansion and mechanical properties by cold working were investigated in the Fe-29%Ni-17%Co (wt%) low thermal expansion alloy. The Fe-29%Ni-17%Co alloy was cold rolled gradually and prepared for plating with reduction ratios of 0%, 20%, 40%, 60%, and 80%. The effect of annealing on the property was also studied. Thermal expansion was measured from 25 ℃ to 600 ℃ using a vacuum differential dilatometer. We found that the thermal expansion coefficient (α30~400) slightly decreased (at a reduction ratio of 20%) and then remarkably increased (above reduction ratios of 40%) with increasing reduction ratios of cold rolling. The thermal expansion coefficient (α30~400) sharply decreased after heat treatment. Yield and tensile strengths continuously increased and elongation decreased by cold rolling. Microstructural observation and XRD analysis results showed that the α phase significantly increased as the reduction ratio increased. The slight decrease of the thermal expansion coefficient below a reduction ratio of 20% could be explained by the destruction of short-range ordering and decrease in grain size. The significant increase in the thermal expansion coefficient with cold rolling attributed to the appearance of the α phase. The correlation between the microstructural cause and invar effect of the low thermal expansion behavior is also discussed. (Received April 7, 2014) |