GB2249511A - Bonding Aluminium-Lithium Alloys - Google Patents
Bonding Aluminium-Lithium Alloys Download PDFInfo
- Publication number
- GB2249511A GB2249511A GB9006889A GB9006889A GB2249511A GB 2249511 A GB2249511 A GB 2249511A GB 9006889 A GB9006889 A GB 9006889A GB 9006889 A GB9006889 A GB 9006889A GB 2249511 A GB2249511 A GB 2249511A
- Authority
- GB
- United Kingdom
- Prior art keywords
- bonding
- temperature
- pieces
- faying surfaces
- faying
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
- 229910001148 Al-Li alloy Inorganic materials 0.000 title claims abstract description 11
- FCVHBUFELUXTLR-UHFFFAOYSA-N [Li].[AlH3] Chemical compound [Li].[AlH3] FCVHBUFELUXTLR-UHFFFAOYSA-N 0.000 title claims abstract description 9
- 239000001989 lithium alloy Substances 0.000 title claims abstract description 9
- 238000000034 method Methods 0.000 claims abstract description 19
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims abstract description 10
- 239000000155 melt Substances 0.000 claims abstract description 7
- 238000002844 melting Methods 0.000 claims abstract description 6
- 230000008018 melting Effects 0.000 claims abstract description 6
- 239000011261 inert gas Substances 0.000 claims abstract description 5
- 229910052710 silicon Inorganic materials 0.000 claims description 7
- 239000010703 silicon Substances 0.000 claims description 7
- 238000009499 grossing Methods 0.000 claims description 4
- 239000007789 gas Substances 0.000 claims description 2
- 238000009792 diffusion process Methods 0.000 abstract description 7
- 239000011863 silicon-based powder Substances 0.000 abstract description 3
- 239000007791 liquid phase Substances 0.000 abstract description 2
- 238000010438 heat treatment Methods 0.000 abstract 1
- 239000000463 material Substances 0.000 description 12
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 6
- 229910045601 alloy Inorganic materials 0.000 description 6
- 239000000956 alloy Substances 0.000 description 6
- 239000004411 aluminium Substances 0.000 description 5
- 229910052782 aluminium Inorganic materials 0.000 description 5
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 5
- 230000004048 modification Effects 0.000 description 5
- 238000012986 modification Methods 0.000 description 5
- 229910052744 lithium Inorganic materials 0.000 description 4
- 229910052751 metal Inorganic materials 0.000 description 4
- 239000002184 metal Substances 0.000 description 4
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 3
- 229910052786 argon Inorganic materials 0.000 description 3
- 229910052749 magnesium Inorganic materials 0.000 description 3
- 239000011777 magnesium Substances 0.000 description 3
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 2
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 description 2
- 239000011324 bead Substances 0.000 description 2
- 238000007707 calorimetry Methods 0.000 description 2
- 238000001816 cooling Methods 0.000 description 2
- 229910052802 copper Inorganic materials 0.000 description 2
- 239000010949 copper Substances 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 239000002245 particle Substances 0.000 description 2
- 239000012071 phase Substances 0.000 description 2
- 238000007747 plating Methods 0.000 description 2
- 238000010405 reoxidation reaction Methods 0.000 description 2
- 238000011282 treatment Methods 0.000 description 2
- 229910000838 Al alloy Inorganic materials 0.000 description 1
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- 229910001069 Ti alloy Inorganic materials 0.000 description 1
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 1
- 230000004888 barrier function Effects 0.000 description 1
- 239000011230 binding agent Substances 0.000 description 1
- 229910002092 carbon dioxide Inorganic materials 0.000 description 1
- 239000001569 carbon dioxide Substances 0.000 description 1
- 238000005336 cracking Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 230000005496 eutectics Effects 0.000 description 1
- 239000004615 ingredient Substances 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 238000005498 polishing Methods 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- HBMJWWWQQXIZIP-UHFFFAOYSA-N silicon carbide Chemical compound [Si+]#[C-] HBMJWWWQQXIZIP-UHFFFAOYSA-N 0.000 description 1
- 229910010271 silicon carbide Inorganic materials 0.000 description 1
- 229910052709 silver Inorganic materials 0.000 description 1
- 239000004332 silver Substances 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 238000010301 surface-oxidation reaction Methods 0.000 description 1
- 239000010936 titanium Substances 0.000 description 1
- 229910052719 titanium Inorganic materials 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
- 229910052725 zinc Inorganic materials 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K20/00—Non-electric welding by applying impact or other pressure, with or without the application of heat, e.g. cladding or plating
- B23K20/22—Non-electric welding by applying impact or other pressure, with or without the application of heat, e.g. cladding or plating taking account of the properties of the materials to be welded
- B23K20/233—Non-electric welding by applying impact or other pressure, with or without the application of heat, e.g. cladding or plating taking account of the properties of the materials to be welded without ferrous layer
- B23K20/2336—Non-electric welding by applying impact or other pressure, with or without the application of heat, e.g. cladding or plating taking account of the properties of the materials to be welded without ferrous layer both layers being aluminium
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K20/00—Non-electric welding by applying impact or other pressure, with or without the application of heat, e.g. cladding or plating
- B23K20/24—Preliminary treatment
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Pressure Welding/Diffusion-Bonding (AREA)
Abstract
Aluminium-lithium alloys are bonded by a liquid phase diffusion bonding process. One or each of the faying surfaces is surface-modified using a laser to promote surface melting under inert gas cover and silicon powder is incorporated into the melt pool. On heating to a bonding temperature in the range 550-570 degrees Celsius the surface modified region melts and permits the pieces to be bonded under light pressure in a short time, eg 15 minutes. <IMAGE>
Description
BONDING ALUMINIUM-LITHIUM ALLOYS
This invention relates to a process for bonding aluminium-lithium alloys. The process might be described as a diffusion bonding process although a liquid phase is utilised in the process and the bond is confined to a prescribed area delimited by the zone of melting.
Aluminium based alloys are difficult to diffusion bond in the usual ways adopted for say metals such as titanium because of the tenacious oxide film present on such materials which forms a barrier to atomic diffusion. Various ways have been tried to diffusion bond aluminium materials. One way of doing this is by removing the oxide layer through bombardment of the metal with ions of an inert gas and then immediately plating the cleaned surface with a suitable metal in conditions which avoid reoxidation of the underlying surface. Silver and copper have both been used as the plating metal. Use of this process limits the size of the workpiece that can be bonded because of the need to clean and plate within a vacuum chamber.
The present invention overcomes this limitations on workpiece size as it does not require a vacuum chamber. The invention is particularly intended for bonding pieces of aluminium-lithium alloys as a step preliminary to subsequent superplastic forming.
The diffusion bonding-superplastic forming process is already in widespread use for titanium alloys and there is considerable interest in applying the same sort of process to aluminium materials, particularly aluminium-lithium materials, if the problems of bonding them can be overcome in a satisfactory way.
It has already been reported that some aluminium-lithium alloys such as AA 8090 have good superplastic forming properties.
The present invention is a process for bonding aluminium-lithium alloys pieces comprising first modifying a portion of one or each of the faying surfaces, by tracking a laser beam shrouded by inert gas over each such portion so as to cause local melting of the surface and incorporating a silicon particulate into melt pool, then smoothing the faying surfaces to the degree, if any, necessary to provide flat surfaces for bonding then placing and holding the faying surfaces against each other under light pressure, raising the temperature of the pieces in the bond region to a temperature in the range of 550 to 570 degrees
Celsius and then maintaining this temperature until the pieces are bonded.
In this specification and claims the term "aluminium-lithium alloy" should be taken to mean such an alloya as has aluminium as principal ingredient which includes at least one percent by weight of lithium. These alloys are believed by @@ to be easier to diffusion bond than the general run of aluminium alloys and some of them at least exhibit excellent superplastic forming properties.
The term "light pressure" as used in this specification and claims should be taken to mean a pressure which causes substantially no signifficant deformation in the section of the bonded material, say a pressure of 500PSI (3.MPa) or less. This level of pressure is convenient because it correspond to the level of external pressure available in a superplastic forming plant. Moreover it is of course always desirable to use the minimum of compressive force necessary to create a sound bond.
It has been observed by differential calorimetry that at a temperature in the region of 550 degrees Celsius some phase change occurs within the surface-modified material containing the silicon particulate below the melting temperature of siliconaluminium eutectic, and it is believed that this contributes to the bonding of the pieces. The temperature of the aluminiumlithium pieces must not exceed 570 degrees Celsius for any appreciable period if loss of lithium and magnesium from free surfaces and consequent loss of strength is to be avoided. A bonding temperature of approximately 560 degrees Celsius is preferred for the AA 8090 alloy at least. A preferred superplatic forming temperature for AA 8090 alloy is 530 degrees Celsius and forming temperature the material within the surface-modified portions is solid and serves to hold the bonded pieces together.
It is preferred that the silicon particulate is incorporated within the melt pool by introducing it directly to the pool as a stream of power under pressure of an inert gas such as argon.
Alternatively the particulate can be admixed with a binder and applied to the surface of the materials before the transit of the laser.
It is not necessary for each of the faying surfaces to be subjected to the surface modifying treatment, however this is the preferred arrangement. When both of the faying surfaces are so modified the modified portions are placed against each other in registration for subsequent bonding.
In the surface modified portions prior to the imposition of the subsequent stages of the bonding process, the silicon is largely present in the form of angular particles. At the completion of the bonding process the form of the particles has been changed to a less angular form suggesting that they have undergone changes in composition at least at their surface. Moreover, there is evidence that the surrounding zone of the parent material has been modified by depletion of lithium and magnesium. These indications confirm the existence of the phase changes predicted by differential calorimetry. The melting which takes place serves to disrupt any surface oxide present on the surface of the surface-modified portions and any abutting unmodified surface.
Normal precautions should be taken to remove the bulk of any surface oxidation from the faying surface by the mechanical means in the surface smoothing stage of the bonding process.
Normal precautions should be takent also to avoid undue delay between the surface preparation stage and the next stage of bonding to minimise reoxidation. The materials should be kept for this period in a dry atmoshere and out of contact with water
The faying surfaces should be carefully degreased after smoothing before proceeding with the remaining stages of the bonding process.
The invention is now described by way of example with reference to the accompanying drawing which is a schematic diagram of a laser surface modification equipment. No invention is alleged in respect of this equipment.
The equipment comprises a laser 1 producing a beam 2 which is directed onto a workpiece 3 through a nozzle 4. Within the nozzle 4 a lens 5 serves to converge the laser beam 1 and the beam width may be adjusted as required by variation of the lens to workpiece separation. Argon is introduced into the nozzle through a passage 6 and this serves to shroud the workpiece in the vicinity of the melt pool created by the laser beam, which is indicated at 7, and prevents oxidation of the melt. Adjacent the nozzle 3 there is a tube 8 through which particulate silicon or particulate silicon admixed with aluminium is fed from a hopper 9 to enter the melt pool. This is supplied under its own argon pressure. The equipment as shown in the drawing is held in a stationary position above the workpiece 2 and the latter is moved beneath it on a travelling table to provide the necessary traverse motion.
The invention has been applied to the bonding of AA 8090 alloy in a manner representative of a diffusior bonding-superplastic forming regime. AA 8090 alloy has a nominal composition by weight as follows: A1 -2.5%Li -1.3%Cu -0.8%Mg -0.12%Zn -0.1% maximum Fe 0.05 maximum Si. Sheet specimens of this material in 1,6 mm and 4mm gauges have been bonded following a variety of surface modification treatments. Using the apparatus as illustrated above with a 2kW carbon dioxide laser a surface modification was made by along a linear track. The silicon powder was first sieved to remove any fraction greater than 125 m and then heated to remove moisture and any volatile inclusions before introduction to the hooper 8. The sheet specimens were degreased and dried prior to commencement of the surface modification. The laser was used at powers ranging from 1.1 to 2kW, typically at 1.8kW. Beam diameters of 1 to 7mm were used and tracking speeds varied from 20 to 110mm/s. The intention was to produce a linear track of surface modification incorporating silicon powder with minimal protrusion beyond the level of the surrounding material but with sufficient depth to ensure continuity when the protruding bead had been removed.
Surface modified tracks which met these requirements were produced within the following envelope of conditions: tracking speed 25-57mm/s; beam diameter 2-6mm; laser power 1850W. Pieces were prepared for bonding by first grinding off the track bead flat with the original surface and then polishing to a 240 grade silicon carbide grit finish. Bonds were made between pieces having a surface modified track on each of the faying surfaces with these tracks in registration with one another and also between pieces with a surface modified track on only one of them.
The bonds were made by p1 placing the two pieces against one another and holding them together in a clamp under pressure produced by finger adjustment of the clamp screws. These clamped pieces were heated to the bonding temperature of 560 degrees Celsius and held at this temperature for 15 minutes. The clamped pieces were the cooled to 530 degrees Celsius and held at this temperature for 1 hour to simulate the thermal cycle of a superplastic forming step. At the completion of this cycle all the pieces were firmly bonded together There was evidence 0+ discontinuous micro- cracking within the bond which is belived to the result of stressing on cooling. This should be avoidable if a a compressive stress is maintained In the joint during cooling and this can be achIeved by applIcation of gas pressure around the joint to the degree normally imposed as back pressure for the avoidance of cavitation in a superplastic forming stage. All that would be required is an earlier application of this back pressure.
Pressure in the range 300-500 PSI (2-3.5MPa) should be suitable and a pressure of this level could be imposed at the commencement te the bonding process tao. maintained throughout
Claims (6)
- CLAIMS I. A process +or bonding aluminium-lithium alloy pieces comprising firs modifying a portion of one or each of the faying surfaces, by tracking a laser beam shrouded by inert gas over each such portion so as to cause local melting of the surface and incorporating a silicon particulate into the melt pool, then smoothing the faying surfaces to the degree, if any, necessary to provide flat surfaces for banding, then placing and holding the faying surfaces against each other under light pressure, raising the temperature of the pieces in the bond region to a temperature in the range of 550 to 570 degrees Celsius and then maintaining this temperature until the pieces are bonded.
- 2. A process as claimed in claim 1 in which the the faying surfaces are held together for bonding at a temperature in the aforementioned range for a period of between 5 and 30 minutes.
- 3. A process as claimed in claim 1 or claim 2 in which the bonding temperature is approximately 560 degrees Celsius.
- 4. A process as claimed in any one of the preceding claims In which the faying surfaces are pressed together under the acti on of an applied gas pressure of 2 to 3.5 Mpa until cooled well bel ow the bonding temperature.
- 5. A proc0-s as claimed in any one of the preceding claims in which each faying surface of the pieces to be joined is surface modified over a portion thereof and in which these portions are arranged to contact each other and in registration for bonding.
- 6. A process as claimed in claim 1 and substantially nF hereinbefore r4e.soribed with reference to the drawing.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB9006889A GB2249511B (en) | 1990-03-28 | 1990-03-28 | Bonding alumimium-lithium alloys |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB9006889A GB2249511B (en) | 1990-03-28 | 1990-03-28 | Bonding alumimium-lithium alloys |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| GB9006889D0 GB9006889D0 (en) | 1990-05-23 |
| GB2249511A true GB2249511A (en) | 1992-05-13 |
| GB2249511B GB2249511B (en) | 1993-10-06 |
Family
ID=10673378
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB9006889A Expired - Fee Related GB2249511B (en) | 1990-03-28 | 1990-03-28 | Bonding alumimium-lithium alloys |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2249511B (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN107876764B (en) * | 2017-11-16 | 2020-01-21 | 清华大学 | A laser forming head and oxidation control method in the process of laser three-dimensional forming |
-
1990
- 1990-03-28 GB GB9006889A patent/GB2249511B/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| GB9006889D0 (en) | 1990-05-23 |
| GB2249511B (en) | 1993-10-06 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| 732E | Amendments to the register in respect of changes of name or changes affecting rights (sect. 32/1977) | ||
| PCNP | Patent ceased through non-payment of renewal fee |
Effective date: 20040328 |
|
| PCNP | Patent ceased through non-payment of renewal fee |
Effective date: 20040328 |