Nano invar alloys and process for producing the same

Abstract

The present invention relates to an electrolyte for producing a novel Fe—Ni alloy having an Ni content in a range of 33 to 42 wt %, specifically a nanocrystalline invar alloy having a grain size of 5 to 15 nm, by electroplating, and preparation conditions thereof. The electrolyte comprises, on the basis of 1 L of water, 32 to 53 g of ferrous sulfate or ferrous chloride, a mixture thereof; 97 g of nickel sulfate, nickel chloride, nickel sulfamate or a mixture thereof; 20 to 30 g of boric acid; 1 to 3 g of sodium saccharin; 0.1 to 0.3 g of sodium lauryl sulfate; and 20 to 40 g of sodium chloride. The Fe—Ni alloy sheet of the present invention exhibits excellent mechanical property compared to the conventional Fe—Ni alloy and a new property, i.e., a negative coefficient of thermal expansion at a given temperature range.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application is a Continuation-In-Part of PCT International Application No. PCT / KR2004 / 000516 filed on Mar. 12, 2004, which designated the United States.FIELD OF THE INVENTION [0002] The present invention relates to an electrolyte for producing a novel Fe—Ni alloy having a Ni content in a range of 33 to 42 wt %, specifically a nanocrystalline invar alloy having a grain size of 5 to 15 nm, by electroplating, and preparation conditions thereof. BACKGROUND OF THE INVENTION [0003] Fe—Ni alloys exhibit various properties according to the Ni content, and low thermal expansion properties are exhibited when the Ni content is in a range of 20% to 50% by weight (see D. R. Rancourt, S. Chehab and G. Lamarche, J. Mag. Mag. Mater. 78 (1989) 129.). Specifically, an alloy consisting of 64% Fe and 36% Ni, which is referred to as “an invar alloy”, has a coefficient of thermal expansion of about zero. The invar alloy has, since its discovery in 1897 ...

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Benefits of technology

[0012] It is still another object of the present invention to provide an Fe—Ni alloy having excellent mechanical properties compared to the conventional invar alloy.

Problems solved by technology

In order to produce a thin invar alloy sheet having a thickness of 0.1 mm or less, it is necessary to carry out a multi-stage rolling process, as disclosed in U.S. Pat. No. 4,94,834, which is, however, complex, and makes it difficult to obtain homogenous product.

Also, this process undesirably requires a high production cost.

Furthermore, there are several problems that large-scale equipment, such as a vacuum melting furnace, forging facility, a hot roller or a multi-stage roller, is required, and a heating process for shaping as requested by final product is quite difficult to perform etc.

Further, coefficients of thermal expansion are undesirably sensitive to impurities involving in the process and a change in the processing conditions (see Metals Handbook, 9th ed.

However, according to the electroplating, since selecting a proper electrolyte or establishing proper processing conditions, such as a temperature or current density, are quite complicated, the use of electroplating for producing desired Fe—Ni alloys has not been successful.

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