The

filler metal A filler metal is a metal added in the making of a joint through welding, brazing, or soldering. Soldering Soldering and brazing processes rely on a filler metal added to the joint to form the junction between the base metal parts. Soft solderin ...

(FM)

alloy An alloy is a mixture of chemical elements of which at least one is a metal. Unlike chemical compounds with metallic bases, an alloy will retain all the properties of a metal in the resulting material, such as electrical conductivity, ductility, ...

s that can be produced as amorphous brazing foils (ABF) are eutectic compositions formed by

transition metal In chemistry, a transition metal (or transition element) is a chemical element in the d-block of the periodic table (groups 3 to 12), though the elements of group 12 (and less often group 3) are sometimes excluded. They are the elements that can ...

s such as

nickel Nickel is a chemical element with symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel is a hard and ductile transition metal. Pure nickel is chemically reactive but large pieces are slow to ...

iron Iron () is a chemical element with symbol Fe (from la, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, right in fr ...

, copper, etc., in combination with

metalloid A metalloid is a type of chemical element which has a preponderance of properties in between, or that are a mixture of, those of metals and nonmetals. There is no standard definition of a metalloid and no complete agreement on which elements are ...

s, such as

silicon Silicon is a chemical element with the symbol Si and atomic number 14. It is a hard, brittle crystalline solid with a blue-grey metallic luster, and is a tetravalent metalloid and semiconductor. It is a member of group 14 in the periodic tab ...

boron Boron is a chemical element with the symbol B and atomic number 5. In its crystalline form it is a brittle, dark, lustrous metalloid; in its amorphous form it is a brown powder. As the lightest element of the ''boron group'' it has th ...

and

phosphorus Phosphorus is a chemical element with the symbol P and atomic number 15. Elemental phosphorus exists in two major forms, white phosphorus and red phosphorus, but because it is highly reactive, phosphorus is never found as a free element on Ea ...

. In conventional crystalline state, all these materials are inherently brittle and cannot be produced in continuous forms such as foil, wire, etc. Therefore, they were available only as powders, pastes, or their derivates. On the other hand, the very presence of metalloids at or near the eutectic concentration promotes the rapid solidification (RS) conversion of such alloys into a ductile amorphous foil.

Production

The production of amorphous alloys requires a manufacturing technology that operates on the basis of the necessary cooling rates, which is known as rapid solidification, or

melt spinning Melt spinning is a metal forming technique that is typically used to form thin ribbons of metal or alloys with a particular atomic structure. Some important commercial applications of melt spun metals include high-efficiency transformers (Amorp ...

technology. Amorphous structures are characterized by the absence of a crystal lattice or a long range order. With this random, spatially uniform arrangement of the constituent atoms, their structure is similar to that of liquids. The nature of this production process is the reason why amorphous alloys are offered only in the form of thin, ductile metal foils. Subsequently, tapes, parts and preforms can be made by e.g. slitting, cutting, stamping and etching.

Properties

Amorphous brazing foils are compositionally much more uniform even after crystallization, they melt over a narrow temperature range under transient heating. This is a consequence of the shorter distances over which atoms of different elements have to diffuse in order to form a uniform liquid phase. The resulting instant melting and their superior flow characteristic is only one of the important features of ABFs. The absence of the residual organic solvent bases evident in powder paste/tapes correspondingly eliminates soot formation and furnace fouling. The low level of gaseous impurities in ABFs, due to the specific characteristics of its production technology, is an attractive feature for vacuum furnace brazing.

Usage

ABFs are available as strip with a width from 0.5 mm to 125 mm and a thickness from 20 µm to 50 µm. Preforms can be easily produced by using punch and die, cutting/slitting, photochemical etching, and other methods. It is simple to use foils and preforms at automatic production and assembling steps. The use of foils and preforms reduces waste and enhances manufacturing efficiency. Drying and evaporation operations, which are required with powder/paste and tape forms, are not necessary. The optimal amount of

brazing Brazing is a metal-joining process in which two or more metal items are joined together by melting and flowing a filler metal into the joint, with the filler metal having a lower melting point than the adjoining metal. Brazing differs from we ...

material can be easily applied to the component and, in just one heating cycle, ABFs create uniform braze joints of outstanding quality.

External links

Metal Leaching of Brazed Stainless Steel Joints into Drinking Water

Nickel-Chromium-Based Amorphous Brazing Foils for Continuous Furnace Brazing of Stainless Steel

New Amorphous Brazing Foils for Exhaust Gas Application

Brazing With (NiCoCr)-B-Si Amorphous Brazing Filler Metals: Alloys, Processing, Joint Structure, Properties, Applications

Brazing Cemented Carbides: Specifics, Braze Optimization and Custom-Designed Amorphous Brazing Filler Metals

Brazing with Amorphous Foil Preforms

Amorphous Brazing Foils VITROBRAZE
Metallurgy Brazing and soldering