Amorphous brazing foil

Types of alloy used for brazing
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An amorphous brazing foil (ABF) is a type of eutectic amorphous metal utilized as a filler metal in the brazing process. Similar to other filler metals, ABFs comprise multiple transition metals like nickel, iron, and copper, combined with metalloids such as silicon, boron, and phosphorus. These alloys can be transformed into a ductile, amorphous foil through rapid solidification by adjusting the metalloid concentration to or near the eutectic point.[1]

Production

The production of an amorphous metal can be achieved by cooling the liquid alloy extremely rapidly, in order to avoid forming a crystal structure. This is traditionally done using melt spinning, which produces a 0.5–125 mm wide strip with a thickness of 20–50 μm. After cooling, the metal can be made into parts or preforms by cutting, stamping, etching, or other methods.[2]

Properties

One fundamental property of amorphous brazing foils are their relatively low melting points, ranging from 830 to 1200 °C, which is key to their use as fill metals. Because of their ductility and flexibility, they can be used as a replacement for paste- or powder-form fill metals. This has the added benefits of eliminating soot formation, due to the absence of residual organic solvents found in pastes; and minimizing the formation of surface oxides, which is a common issue with gas-atomized powders.[1]

Usage

Amorphous brazing foils are typically used for brazing, a metallurgy process by which two pieces of metal are joined by melting and cooling a third "fill metal" at their joint. The use of preforms increases the capability of ABFs for use on an industrial scale, even being able to be assembled by machine.[1]

References

  1. ^ a b c Rabinkin, A. (June 1, 2004). "Brazing with (NiCoCr)–B–Si amorphous brazing filler metals: Alloys, processing, joint structure, properties, applications". Science and Technology of Welding and Joining. 9 (3): 181–199. doi:10.1179/136217104225012300. ISSN 1362-1718. S2CID 136671451 – via Taylor & Francis Online.
  2. ^ Greer, A. Lindsay (1995-03-31). "Metallic Glasses". Science. 267 (5206): 1947–1953. Bibcode:1995Sci...267.1947G. doi:10.1126/science.267.5206.1947. ISSN 0036-8075. PMID 17770105. S2CID 12452422.

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