Diffusion bonding of aluminium and aluminium alloys

Claim 2

A process of diffusion bonding components at least one of which is made of aluminium or an aluminium alloy and which is liable to form a surface coating of aluminium oxide, which process comprises grit blasting the components made of aluminium or aluminium alloy in areas that are to be bonded to other components, chemically treating the grit blasted components to remove surface aluminium oxide and subsequently heating and pressing the components together without substantial plastic deformation of the components to produce a diffusion bond.

Claim 3

A process of superplastically forming an article made from two or more components, at least one of which is made of aluminium or an aluminium alloy and which is liable to form a surface coating of aluminium oxide and at least one of which is capable of being superplastically formed, which process comprises grit blasting the components made of aluminium or aluminium alloy in areas that are to be bonded to other components, chemically treating the grit blasted components to remove surface aluminium oxide, applying stop-off material to areas of the components that it is desired not to bond to other components (unbonded areas), subsequently heating and pressing the components together without substantial plastic deformation of the components to produce a composite structure having at least one unbonded area surrounded by at least one area in which the said components are joined together by diffusion bonding, heating the composite structure to a temperature at which superplastic forming can take place and introducing pressurised gas into the unbonded area to superplastically form the said composite into a desired shape.

Claim 4

A process of superplastically forming an article made from two or more components, at least one of which is made of aluminium or an aluminium alloy and which is liable to form a surface coating of aluminium oxide and at least one of which is capable of being superplastically formed, which process comprises grit blasting the components made of aluminium or aluminium alloy in areas that are to be bonded to other components, chemically treating the grit blasted components to remove surface aluminium oxide, applying stop-off material to areas of the components that it is desired not to bond to other components (unbonded areas), subsequently heating and pressing the components together without substantial plastic deformation of the components to produce a composite structure having at least one unbonded area surrounded by at least one area in which the said components are joined together by diffusion bonding, heating the composite structure to a temperature at which superplastic forming can take place and introducing pressurised gas into the unbonded area to superplastically form the said composite into a desired shape.

Claim 5

A process as claimed in claim 1 or in claim 2, wherein the components are pre-treated prior to grit blasting to remove the layer of aluminium oxide.

Claim 6

A process as claimed in claim 3, wherein the said pre-treatment comprises subjecting the components to a deoxidising solution or an acid etch, e.g. using sulphuric and/or chromic acid.

Claim 7

A process as claimed in any one of claims 1 to 4, wherein the chemical treatment step between the grit blasting step and the diffusion bonding step is performed with a deoxidising solution, e.g. a non-chromated composition.

Claim 8

A process as claimed in claim 5, wherein the deoxidising solution is an acid.

Claim 9

A process as claimed in claim 6, wherein the deoxidising solution is a non-oxidising acid.

Claim 10

A process as claimed in any one of claims 1 to 7, wherein the diffusion bonding is conducted at a temperature of 500 to 580 o C for 2 to 5 hours.

Claim 11

A process as claimed in claim 8, wherein the diffusion bonding is conducted at a temperature in the range of from 540 to 560 o C.