Significant reduction in thermal expansion of a low-carbon steel sheet by depositing a Fe-Ni alloy thin film
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Significant reduction in thermal expansion of a low-carbon steel sheet by depositing a Fe–Ni alloy thin film Sang Sub Kima) and Yong Bum Park Department of Materials Science and Metallurgical Engineering, Research and Development Center for Automobile’s Parts and Materials, Sunchon National University, Sunchon 540-742, Korea (Received 9 August 1999; accepted 25 October 1999)
A 3-m-thick Fe–Ni alloy thin film was deposited on a 0.2-mm-thick low-carbon steel substrate by radio-frequency magnetron sputtering, and the properties of the film were investigated. The film exhibits a columnar growth structure and a fiber texture with the relationship of (110)film//(111)substrate. A thermal cycle test showed good adhesion between the film and the substrate. Most importantly, the Fe–Ni alloy deposition results in a significant reduction in thermal expansion of the whole specimen. These results suggest that a properly deposited Fe–Ni alloy film could be applied to a low-carbon steel sheet to significantly reduce its thermal expansion. Such reduced thermal expansion would enhance the image resolution of a shadow mask made of a low-carbon steel sheet. Fe–Ni alloys have been receiving great attention because of their various interesting thermomechanical and magnetic properties. For instance, Invar, Fe–36.5 wt% Ni, shows an extremely low thermal expansion behavior, which is called the Invar anomaly. Such a low thermal expansion property has been applied to various functional devices and standard specimens.1 Other Fe–Ni alloys have outstanding magnetic properties. Many attempts have been made to examine the thermal, mechanical, and magnetic properties of the Fe–Ni alloys. Some models explaining the Invar anomaly have also been proposed.2–5 One of the most important applications of Invar is in shadow masks, which are the components that guide electron beams in cathode ray tubes. Electrons normally pass through holes in the shadow mask. However, some electron beams strike the shadow mask, raising its temperature, and expanding the holes. This eventually results in the deterioration of image resolution. Therefore, materials for a shadow mask need a low thermal expansion to reduce such doming effects.6 In practice, however, low-carbon steel sheet with a larger thermal expansion than Invar has been often used for low-grade shadow masks at the expense of the image resolution because of its much lower price than Invar. It is likely that a low-carbon steel sheet supporting a properly deposited Fe–Ni alloy film may exhibit a lower
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Address all correspondence to this author. Present address: 4th Group, National Institute for Research in Inorganic Materials, Namiki 1-1, Tsukuba, Ibaraki 305-0044, Japan e-mail: [email protected]
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J. Mater. Res., Vol. 15, No. 1, Jan 2000 Downloaded: 17 Apr 2015
thermal expansion than a bare one. In an attempt to explore the possibility combining the extremely lowthermal expansion property of Invar and the low cost of a low-ca
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