A bonding material includes: a copper foil; and a sinterable bonding film formed on one surface of the copper foil. The bonding film contains a copper powder and a solid reducing agent. The bonding material is used for bonding to a bonding target having, on its surface, at least one metal selected from the group consisting of gold, silver, copper, nickel, and aluminum. The bonding material is also used as a material for wire bonding. A bonded structure is also provided in which a bonding target having a metal layer formed on its surface and a copper foil are electrically connected to each other via a bonding layer formed of a sintered structure of a copper powder, wherein the metal layer contains at least one metal selected from the group consisting of gold, silver, copper, nickel, and aluminum.

An aluminum alloy for flux-free brazing provided for brazing performed via an Al—Si-based brazing material without a flux in a non-oxidizing atmosphere without depressurization, includes: by mass %, 0.01% to 2.0% of Mg; and 0.005% to 1.5% of Bi, wherein in the aluminum alloy, there are more than 10 Mg—Bi-based compounds having a diameter of 0.01 μm or more and less than 5.0 μm in terms of equivalent circle diameter per 10,000-μm.sup.2 visual field and there are less than 2 Mg—Bi-based compounds having a diameter of 5.0 μm or more per 10,000-μm.sup.2 visual field in a cross section parallel to a rolling direction, and in the aluminum alloy, there are less than 5 Bi particles having a diameter of 5.0 μm or more in terms of equivalent circle diameter per 10,000-μm.sup.2 visual field in the cross section parallel to the rolling direction.

A closed impeller (1) includes an impeller main body (2), which is composed of an aluminum alloy and has blades (22) that protrude from a hub (21). A shroud (3) covers the blades. The blades and the shroud are joined together by brazed joints (4). The shroud (3) is formed from a brazing sheet (30) that comprises a core material (31), which is composed of an aluminum alloy, and a filler material layer (320), which is disposed on on an outermost surface (33) of the shroud that opposes or faces the blades when the shroud is brazed to the blades.

A brazing sheet for flux-free brazing has an outermost surface brazing filler metal layer, consisting of an Al—Si-based alloy containing 2 to 13% Si in mass %, and an intermediate brazing filler metal layer, consisting of an Al—Si—Mg-based alloy containing 4 to 13% Si and 0.1 to 5.0% Mg in mass %, which are cladded on one or both sides of a core material. In the outermost surface brazing filler metal layer, the number of Si particles having a circle equivalent diameter of 1.75 μm or more is 10% or more of the number having a circle equivalent diameter of 0.8 μm or more, as observed in the direction of the surface layer. The intermediate brazing filler metal layer contains less than 3000 per 10000 μm.sup.2 of Si particles having a circle equivalent diameter of 0.25 μm or more, as observed in a cross section of the brazing filler metal layer.

A multi-layered brazing sheet product having an aluminium core alloy layer provided on one or both sides with a brazing clad layer material, and an inter-layer material positioned between the aluminium core alloy layer and at least one of the brazing clad layer materials, wherein the brazing layer material(s) is made from an 4xxx-series aluminium alloy having 5% to 15% Si and up to 3% Mg, and wherein the inter-layer material is made from a 1xxx-series aluminium alloy having a purposive addition of Mg of 0.10% to 2.0%. The invention relates also to the use of the brazing sheet product in a fluxless controlled atmosphere brazing process.

An aluminum alloy brazing sheet used for brazing of an aluminum material in an inert gas atmosphere or in vacuum is formed of a two-layer material in which a brazing material and a core material are stacked in this order. The core material is formed of an aluminum alloy and has a grain size of 20 to 300 μm, and the aluminum alloy contains Mn of 0.50 to 2.00 mass %, Mg of 0.40 to 2.00 mass %, Si of 1.50 mass % or less, and Fe of 1.00 mass % or less, with the balance being aluminum and inevitable impurities. The brazing material is formed of an aluminum alloy containing Si of 4.00 to 13.00 mass % with the balance being aluminum and inevitable impurities, and, in a drop-type fluidity test, a ratio α (α=K.sub.a/K.sub.b) of a fluid coefficient K.sub.a is 0.50 or more.

An aluminum alloy brazing sheet may include a sacrificial material having a function of a brazing material on at least one surface of a core material, wherein the sacrificial material has a composition containing: in a mass %, 2% to 5% of Si; 3% to 5% of Zn; and an Al balance with inevitable impurities the core material is made of an Al—Mn-based alloy, an in the core material before brazing, Al—Mn based secondary particles having an equivalent circle diameter of 100 to 400 nm are distributed with a number density of 0.3 to 5 particles/μm.sup.2.

A strip intended for the manufacture of brazed heat exchangers, having a core made of an alloy with the composition (weight %):

Si: 0.10-0.30%, preferably 0.15-0.25%
Fe<0.25%, preferably 0.1-0.2%
Cu: 0.85-1.1%, preferably 0.9-1.0%
Mn: 1.2-1.7%, preferably 1.2-1.4%
Mg: 0.1-0.3%, preferably 0.1-0.21%
Zn<0.1%
Ti 0.05-0.20%, preferably 0.06-0.15%, more preferably 0.06-0.1%
optionally up to 0.15% of Bi and/or Y
other elements <0.05% each and <0.15% in total,
remainder aluminium.

A joining method includes the steps of placing a brazing element between an interface area of a first ceramic piece and an interface area of a second ceramic piece to create a joining pre-assembly, placing the components of said joining pre-assembly into a process chamber, removing oxygen from said process chamber, and heating at least said brazing element of said joining pre-assembly, thereby hermetically joining said first ceramic piece to said second ceramic piece. The brazing element consists of Nickel and Carbon.

A brazing sheet (1) includes a core material (11) composed of an Al alloy that contains 0.20-3.0 mass % of Mg; and a filler material (12) layered on the core material and composed of an Al alloy that contains Mg, 6.0-13.0 mass % of Si, and more than 0.050 mass % and 1.0 mass % or less of Bi. The Mg concentration of the filler material becomes continuously lower in a direction from a boundary (122) with the core material to an outermost surface (121). The Mg concentration of the filler material is 0.150 mass % or less at a first depth from the outermost surface that is ⅛ of a thickness (t.sub.f) of the filler material and is 5-90% of the amount of Mg in the core material at a second depth from the outermost surface that is ⅞ of the thickness of the filler material.