Patent Application
20220333265
7xxx aluminum alloys are aluminum alloys having zinc and magnesium as their primary alloying ingredients, besides aluminum. It would be useful to facilitate adhesive bonding of 7xxx aluminum alloys to itself and other materials (e.g., for automotive applications).
Broadly, the present disclosure relates to methods of preparing 7xxx aluminum alloys for production of a functionalized layer thereon (e.g., for adhesive bonding) and 7xxx aluminum alloy products relating thereto. Referring now to
Still referring to
In one embodiment, and referring now to
After the cleaning step (210), the 7xxx aluminum alloy product is generally subjected to an oxide removal step (220), which thins and/or removes the oxide layer (20). The oxide removal step (220) may comprise, for instance, exposing the cleaned 7xxx aluminum alloy surface to a caustic solution (e.g., NaOH), then rinsing, then exposing the 7xxx aluminum alloy surface to an acidic solution (e.g., nitric acid), and then rinsing again. Other types of oxide thinning methodologies may be employed. After the oxide removal step (220), little or none of the as-received surface oxide layer is present on the 7xxx aluminum alloy body surface. After the oxide thinning, the 7xxx aluminum alloy product generally comprises a prepared oxide layer (30). This prepared oxide layer (30) is thinner than the as-received oxide layer (20), generally having an average (mean) thickness of about 5-10 nanometers, or thereabouts. The prepared oxide layer (30) also generally comprises a non-uniform (e.g., scalloped) topography. This prepared oxide layer generally (30) facilitates the subsequent anodizing (300) and creating a functional layer (400) steps.
Referring now to
The thickness of the anodic oxide layer (40) may be measured by XPS (X-ray Photoelectron Spectroscopy) using a sputter rate relative to an aluminum oxide standard having a verified oxide thickness. For instance, the oxide thickness may be determined based on a sputter rate relative to a measured thickness of Al2O3 that was determined using a commercially available SiO2 sputter-rate standard, which may have a known thickness of 50 nm or 100 nm, for instance. The aluminum oxide standard material may be an Al2O3 layer that was deposited via e-beam evaporation onto a silicon wafer, and may have a corresponding thickness of 50 nm or 100 nm, for instance. The relative ratio of the SiO2/Al2O3 sputtering is approximately 1.6.
The anodizing conditions used to produce the thin anodic oxide layer (40) may vary depending on the acidic electrolyte solution used. In one embodiment, the acidic electrolyte solution comprises one of sulfuric acid, phosphoric acid, chromic acid, and oxalic acid. In one embodiment, the anodizing solution consists essentially of sulfuric acid (e.g., is essentially a 10-20 wt. % sulfuric acid solution). In another embodiment, the anodizing solution consist essentially of phosphoric acid (e.g., is essentially a 5-20 wt. % phosphoric acid solution). In yet another embodiment, the anodizing solution consist essentially of chromic acid. In another embodiment, the anodizing solution consist essentially of oxalic acid. In one embodiment, the anodizing solution has a temperature of from 60 to 100° F. during anodizing. In one embodiment, the anodizing solution has a temperature of at least 65° F. during anodizing. In another embodiment, the anodizing solution has a temperature of at least 70° F. during anodizing. In one embodiment, the anodizing solution has a temperature of not greater than 95° F. during anodizing. In another embodiment, the anodizing solution has a temperature of not greater than 90° F. during anodizing.
After the anodizing step (300), the combined thickness of the prepared oxide layer (30) and the anodic oxide layer (40) should be at least 15 nanometers thick, but not greater than 150 nanometers thick (i.e., the combined thickness of layer (30) plus layer (40) should be from 15-100 nanometers). As described in further detail below, in step (400), a functionalized layer is created after the anodizing step (300). This creating step (400) includes exposing the anodized 7xxx aluminum alloy product to an appropriate phosphorous-containing organic acid (e.g., an organophosphoric or an organophosphonic acid). If the combined thickness of the prepared oxide layer (30) and the anodic oxide layer (40) is less than 15 nanometers thick, then insufficient penetration of phosphorous may occur in the creating step (400). If the combined thickness of the prepared oxide layer (30) and the anodic oxide layer (40) is more than 150 nanometers thick, then adhesive bonding performance (after the creating step (400)) may be degraded.
In one embodiment, the combined thickness of the prepared oxide layer (30) and the anodic oxide layer (40) is at least 20 nanometers. In another embodiment, the combined thickness of the prepared oxide layer (30) and the anodic oxide layer (40) is at least 25 nanometers. In one embodiment, the combined thickness of the prepared oxide layer (30) and the anodic oxide layer (40) is not greater than 135 nanometers thick. In another embodiment, the combined thickness of the prepared oxide layer (30) and the anodic oxide layer (40) is not greater than 125 nanometers thick. In yet another embodiment, the combined thickness of the prepared oxide layer (30) and the anodic oxide layer (40) is not greater than 115 nanometers thick. In another embodiment, the combined thickness of the prepared oxide layer (30) and the anodic oxide layer (40) is not greater than 105 nanometers thick. In yet another embodiment, the combined thickness of the prepared oxide layer (30) and the anodic oxide layer (40) is not greater than 100 nanometers thick. In another embodiment, the combined thickness of the prepared oxide layer (30) and the anodic oxide layer (40) is not greater than 95 nanometers thick. In yet another embodiment, the combined thickness of the prepared oxide layer (30) and the anodic oxide layer (40) is not greater than 90 nanometers thick. In another embodiment, the combined thickness of the prepared oxide layer (30) and the anodic oxide layer (40) is not greater than 85 nanometers thick. In yet another embodiment, the combined thickness of the prepared oxide layer (30) and the anodic oxide layer (40) is not greater than 80 nanometers thick. In another embodiment, the combined thickness of the prepared oxide layer (30) and the anodic oxide layer (40) is not greater than 75 nanometers thick. In yet another embodiment, the combined thickness of the prepared oxide layer (30) and the anodic oxide layer (40) is not greater than 70 nanometers thick. In another embodiment, the combined thickness of the prepared oxide layer (30) and the anodic oxide layer (40) is not greater than 65 nanometers thick, or thinner.
Still referring to
In another approach (not illustrated), the anodizing step (300) comprises anodizing in an appropriate phosphoric acid solution for a time sufficient and under conditions sufficient to create the anodic oxide layer (40). In one embodiment, the voltage applied is from 10-20 volts, and the anodizing time is not greater than 120 seconds. In one embodiment, the anodizing comprises anodizing in phosphoric acid (e.g., a 5-20 wt. % phosphoric acid solution) having a temperature of from 80-100° F. (e.g., 90° F.) and at 13-18 volts for 10 to 60 seconds, or similar conditions, as required to facilitate production of the anodic oxide layer of suitable thickness. Other appropriate phosphoric anodizing conditions can be used.
After the anodizing step (300) and any appropriate intervening steps (e.g., rinsing), the method may include creating a functional layer (400) via an appropriate chemical (e.g., a phosphorus-containing organic acid). In one embodiment, the creating step (400) may include contacting the anodized 7xxx aluminum alloy product with any of the phosphorus-containing organic acids disclosed in U.S. Pat. No. 6,167,609 to Marinelli et al., which is incorporated herein by reference. A layer of polymeric adhesive may then be applied to the functionalized layer (e.g., for joining to a metal support structure to form a vehicle assembly). The creating step (400) may alternatively use conversion coatings in lieu of a phosphoric containing organic acid. For instance, conversion coatings employing titanium or titanium with zirconium may be used. Thus, in one embodiment, after anodizing, the anodic oxide layer is contacted with a Ti-type or TiZr-type conversion coating to create the functionalization layer.
Prior to creating the functional layer (400), the prepared 7xxx aluminum alloy product may be further prepared, such as by rinsing the prepared 7xxx aluminum alloy product. To create the functional layer, the prepared 7xxx aluminum alloy product is generally exposed to an appropriate chemical, such as an acid or base. In one embodiment, the chemical is a phosphorous-containing organic acid. The organic acid generally interacts with aluminum oxide in the prepared oxide layer to form a functionalized layer. The organic acid is dissolved in water, methanol, or other suitable organic solvent, to form a solution that is applied to the 7xxx aluminum alloy product by spraying, immersion, roll coating, or any combination thereof. The phosphorus-containing organic acid may be an organophosphonic acid or an organophosphinic acid. The pretreated body is then rinsed with water after the acid application step. In another embodiment, the chemical is a Ti-type or TiZr-type conversion coating.
The term “organophosphonic acid” includes acids having the formula Rm[PO(OH)2]n wherein R is an organic group containing 1-30 carbon atoms, m is the number of organic groups and is about 1-10, and n is the number of phosphonic acid groups and is about 1-10. Some suitable organophosphonic acids include vinyl phosphonic acid, methylphosphonic acid, ethylphosphonic acid, octylphosphonic acid and styrenephosphonic acid
The term “organophosphinic acid” includes acids having the formula RmR′o[PO(OH)]n wherein R is an organic group containing 1-30 carbon atoms, R′ is hydrogen or an organic group containing 1-30 carbon atoms, m is the number of R groups and is about 1-10, n is the number of phosphinic acid groups and is about 1-10, and o is the number of R′ groups and is about 1-10. Some suitable organophosphinic acids include phenylphosphinic acid and bis-(perfluoroheptyl)phosphinic acid.
In one embodiment, a vinyl phosphonic acid surface treatment is used that forms essentially a monolayer with aluminum oxide in the surface layer. The coating areal weight may be less than about 15 mg/m2. In one embodiment, the coating areal weight is only about 3 mg/m2.
An advantage of these phosphorus-containing organic acids is that the pretreatment solution contains less than about 1 wt. % chromium and preferably essentially no chromium. Accordingly, environmental concerns associated with chromate conversion coatings are eliminated.
Due to the functionalization, the anodic oxide layer (40) may include phosphorous. In one embodiment, a surface phosphorous content of the anodic oxide layer is at least 0.2 mg/m2 (average). As used herein, “surface phosphorus content” means the average amount of phosphorus at the surface of the anodic oxide layer (40) as measured by XRF (X-Ray Fluorescence). The area of collection should be at least 3 cm×3 cm (1.25 inches by 1.25 inches) across the functionalized surface. In one embodiment, a surface phosphorous content of the anodic oxide layer is at least 0.3 mg/m2 (average). In another embodiment, a surface phosphorous content of the anodic oxide layer is at least 0.4 mg/m2 (average). In yet another embodiment, a surface phosphorous content of the anodic oxide layer is at least 0.5 mg/m2 (average). In another embodiment, a surface phosphorous content of the anodic oxide layer is at least 0.6 mg/m2 (average). In yet another embodiment, a surface phosphorous content of the anodic oxide layer is at least 0.7 mg/m2 (average). The surface phosphorous content of the anodic oxide layer is generally not greater than 4.65 mg/m2 (average).
When the functionalization solution is a phosphorous-containing organic acid, the functionalization generally results in the phosphorus being bound to an organic group (R) as shown in
The functionalized 7xxx aluminum alloy product may be cut in desired sizes and shapes and/or worked into a predetermined configuration. Castings, extrusions and plate may also require sizing, for example by machining, grinding or other milling process, and prior to the application of the methods described herein. Shaped assemblies made in accordance with the invention are suitable for many components of vehicles, including automotive bodies, body-in-white components, doors, trunk decks and hood lids. The functionalized 7xxx aluminum alloy products may be bonded to a metal support structure using a polymeric adhesive.
In manufacturing automotive components, it is often necessary to join the functionalized 7xxx aluminum alloy material to an adjacent structural member. Joining functionalized 7xxx aluminum alloy materials may be accomplished in two steps. First, a polymeric adhesive layer may be applied to the functionalized 7xxx aluminum alloy product, after which it is pressed against or into another component (e.g., another functionalized 7xxx aluminum alloy product; a steel product; a 6xxx aluminum alloy product; a 5xxx aluminum alloy product; a carbon reinforced composite). The polymeric adhesive may be an epoxy, a polyurethane or an acrylic.
After the adhesive is applied, the components may be spot welded together, e.g., in a joint area of applied adhesive. Spot welding may increase peel strength of the assembly and may facilitate handling during the time interval before the adhesive is completely cured. If desired, curing of the adhesive may be accelerated by heating the assembly to an elevated temperature. The assembly may then be passed through a paint preparation process (e.g., a zinc phosphate bath or zirconium based treatment), dried, electrocoated, and subsequently painted with an appropriate finish.
Referring now to
As used in the context of
In one embodiment of the method, when the as-bonded 7xxx aluminum alloy product is in the form of a single-lap-joint specimen having an aluminum metal-to-second material joint overlap of 0.5 inches, the as-bonded 7xxx aluminum alloy product achieves completion of 45 stress durability test (SDT) cycles according to ASTM D1002 (10). In one embodiment, a residual shear strength of the single-lap-joint specimen after completing the 45 SDT cycles is at least 80% of an initial shear strength. In another embodiment, the residual shear strength of the single-lap-joint specimen after completing the 45 SDT cycles is at least 85% of the initial shear strength. In yet another embodiment, the residual shear strength of the single-lap-joint specimen after completing the 45 SDT cycles is at least 90% of the initial shear strength.
The method may optionally comprise one or more thermal exposure steps. For instance, purposeful thermal exposure steps may be applied before the preparing step (200), before the anodizing step (300), and/or after the creating step (400). The thermal exposure step(s) may result in the production of a thermal oxide layer on the 7xxx aluminum alloy product. In one embodiment, the total thickness of the prepared oxide layer plus the thermal oxide layer plus the anodic oxide layer is from 15-150 nanometers, as described above relative to
In one embodiment, the total thickness of the prepared oxide layer plus the thermal oxide layer plus the anodic oxide layer is at least 20 nanometers. In another embodiment, the total thickness of the prepared oxide layer plus the thermal oxide layer plus the anodic oxide layer is at least 25 nanometers. In one embodiment, the total thickness of the prepared oxide layer plus the thermal oxide layer plus the anodic oxide layer is not greater than 135 nanometers thick. In another embodiment, the total thickness of the prepared oxide layer plus the thermal oxide layer plus the anodic oxide layer is not greater than 125 nanometers thick. In yet another embodiment, the total thickness of the prepared oxide layer plus the thermal oxide layer plus the anodic oxide layer is not greater than 115 nanometers thick. In another embodiment, the total thickness of the prepared oxide layer plus the thermal oxide layer plus the anodic oxide layer is not greater than 105 nanometers thick. In yet another embodiment, the total thickness of the prepared oxide layer plus the thermal oxide layer plus the anodic oxide layer is not greater than 100 nanometers thick. In another embodiment, the total thickness of the prepared oxide layer plus the thermal oxide layer plus the anodic oxide layer is not greater than 95 nanometers thick. In yet another embodiment, the total thickness of the prepared oxide layer plus the thermal oxide layer plus the anodic oxide layer is not greater than 90 nanometers thick. In another embodiment, the total thickness of the prepared oxide layer plus the thermal oxide layer plus the anodic oxide layer is not greater than 85 nanometers thick. In yet another embodiment, the total thickness of the prepared oxide layer plus the thermal oxide layer plus the anodic oxide layer is not greater than 80 nanometers thick. In another embodiment, the total thickness of the prepared oxide layer plus the thermal oxide layer plus the anodic oxide layer is not greater than 75 nanometers thick. In yet another embodiment, the total thickness of the prepared oxide layer plus the thermal oxide layer plus the anodic oxide layer is not greater than 70 nanometers thick. In another embodiment, the total thickness of the prepared oxide layer plus the thermal oxide layer plus the anodic oxide layer is not greater than 65 nanometers thick, or thinner.
In one approach, a thermal exposure may be completed before the preparing step (200) (i.e., after the receiving step (100) and before the preparing step (200)). In one embodiment, a solution heat treatment and quench (a solutionizing treatment) may be completed on as received F-temper product, after which the preparing step (200) is completed. For instance, an as-received 7xxx aluminum alloy product may be in the F-temper (as fabricated). Prior to the preparing step (200), the 7xxx aluminum alloy product may be formed into a predetermined shaped product, such as an automotive component (e.g., door outer and/or inner panels, body-in-white components (A-pillars, B-pillar, or C-pillars), hoods, deck lids, and similar components). This forming step may be completed at elevated temperatures, and may, therefore subject the 7xxx aluminum alloy product to various thermal practices (e.g., consistent with a solutionizing treatment (i.e., a solution heat treatment plus quench), when warm or hot forming and then die quenched). To further develop the strength (or other properties) of the formed 7xxx aluminum alloy product, the formed 7xxx aluminum alloy product may be artificially aged, which artificial aging may occur before the preparing step (200), before the anodizing step (300), and/or after the creating step (400). In one embodiment, one or more artificial aging steps follow a solutionizing treatment, after which the preparing step (200) is completed. In another embodiment, artificial aging is completed on an as-received W-temper or T-temper product, after which the preparing step (200) is completed. Paint baking may then occur after the creating step (400).
In one approach, a thermal exposure may be completed before the anodizing step (200) (i.e., after the preparing step (100) and before the anodizing step (200)). For instance, a solution heat treatment and quench (a solutionizing treatment) may be completed on a prepared F-temper product, after which the anodizing step (200) is completed. For instance, an as-received 7xxx aluminum alloy product may be in the F-temper (as fabricated). After the preparing step (200) and prior to the anodizing step (300), the 7xxx aluminum alloy product may be formed into a predetermined shaped product, such as an automotive component (e.g., door outer and/or inner panels, body-in-white components (A-pillars, B-pillar, or C-pillars), hoods, deck lids, and similar components). This forming step may be completed at elevated temperatures, and may, therefore subject the 7xxx aluminum alloy product to various thermal practices (e.g., consistent with a solutionizing treatment (i.e., a solution heat treatment plus quench), when warm or hot forming and then die quenched). To further develop the strength (or other properties) of the formed 7xxx aluminum alloy product, the formed 7xxx aluminum alloy product may be artificially aged, which artificial aging may occur before the anodizing step (300), and/or after the creating step (400).
In one embodiment, one or more artificial aging steps follow a solutionizing treatment, after which the anodizing step (300) is completed. In another embodiment, artificial aging is completed on an as-received W-temper or T-temper product, after which the preparing step (200) is completed. Paint baking may then occur after the creating step (400)
Any of the thermal exposure steps described above may be combined, as applicable, to complete the product. For instance, a thermal exposure may be completed both prior to preparing (200) and prior to anodizing (300). Paint baking may then occur after the creating step (400)
When utilized, the artificial aging may facilitate realization of any of an underaged, peak aged, or overaged temper. As may be appreciated, the 7xxx aluminum alloy product may be formed before an artificial aging step, or after an artificial aging step, if utilized.
The methods disclosed herein are generally applicable to 7xxx aluminum alloy products, such as those including copper resulting in the formation of copper-bearing intermetallic particles. In one approach, the 7xxx aluminum alloy product comprises 2-12 wt. % Zn, 1-3 wt. % Mg, and 0-3 wt. % Cu (e.g., 1-3 wt. % Cu). In one embodiment, the 7xxx aluminum alloy product is one of a 7009, 7010, 7012, 7014, 7016, 7116, 7032, 7033, 7034, 7036, 7136, 7037, 7040, 7140, 7042, 7049, 7149, 7249, 7349, 7449, 7050, 7150, 7055, 7155, 7255, 7056, 7060, 7064, 7065, 7068, 7168, 7075, 7175, 7475, 7178, 7278, 7081, 7181, 7085, 7185, 7090, 7093, 7095, 7099, or 7199 aluminum alloy, as defined by the Aluminum Association Teal Sheets (2015). In one embodiment, the 7xxx aluminum alloy is 7075, 7175, or 7475. In one embodiment, the 7xxx aluminum alloy is 7055, 7155, or 7225. In one embodiment, the 7xxx aluminum alloy is 7065. In one embodiment, the 7xxx aluminum alloy is 7085 or 7185. In one embodiment, the 7xxx aluminum alloy is 7050 or 7150. In one embodiment, the 7xxx aluminum alloy is 7040 or 7140. In one embodiment, the 7xxx aluminum alloy is 7081 or 7181. In one embodiment, the 7xxx aluminum alloy is 7178.
The 7xxx aluminum alloy product may be in any form, such as in the form of a wrought product (e.g., a rolled sheet or plate product, an extrusion, a forging). The 7xxx aluminum alloy product may alternatively be in the form of a shape-cast product (e.g., a die casting). The 7xxx aluminum alloy product may alternatively be an additively manufactured product. As used herein, “additive manufacturing” means “a process of joining materials to make objects from 3D model data, usually layer upon layer, as opposed to subtractive manufacturing methodologies”, as defined in ASTM F2792-12a entitled “Standard Terminology for Additively Manufacturing Technologies”.
The temper and 7xxx aluminum alloy definitions provided herein are per ANSI H35.1 (2009).
Several samples of a 7xxx aluminum alloy (Al—Zn—Mg—Cu style) product were received and prepared as per step (200) of
Several samples of a 7xxx aluminum alloy (Al—Zn—Mg—Cu style) were processed as per
The samples anodized for 60 seconds successfully completed the required 45 cycles and produced retained lap shear strengths of 7253, 6600, 6851 and 7045 psi in the four replicate specimens (6937 psi, ave., with a stdev (σ) of 278 psi). These residual shear strength results are superior to the typical range of 4500-6000 psi typically observed for adhesively bonded 5xxx and 6xxx alloys prepared by another conventional industry practice. The four residual shear strength results are also consistent, as indicated by the low standard deviation. The samples anodized for only 10 or 45 seconds at 6 ASF did not successfully complete the bond durability testing. Only two of the 45 second anodized samples survived the 45 cycles, and none of the 10 second anodized samples survived the 45 cycle requirement.
As a baseline, four of the same alloy samples were prepared similarly to above, but were held for 60 seconds in the 15 wt. % sulfuric acid anodizing bath at 70° F., without any current applied. The same functional layer was then created (400), per
Several samples of a 7xxx aluminum alloy (Al—Zn—Mg—Cu style) were processed as per
To verify oxide thickness, one of the 10 second anodized samples was analyzed by XPS. The analysis indicated that the anodic oxide layer had a thickness of 28 nm thick, and consisted essentially of aluminum oxides (e.g., Al2O3). See,
As per Example 2, baseline samples were also prepared using the same conditions as the anodized sample, but in the absence of anodizing—the samples, instead, were placed in the 15 wt. % sulfuric acid anodizing bath at 70° F. without any current applied. The same functional layer was then created (400), per
To confirm that different anodizing conditions could be used with this same material, one additional sample of the material was prepared as per
Several additional 7xxx aluminum alloys (Al—Zn—Mg—Cu style) were processed as per
The anodic oxide layers of the 20 second and 40 second anodized sample were then analyzed by XPS. The 20 second anodized sample had an anodic oxide thickness of 72 nm, whereas the 40 second anodized sample has an anodic oxide thickness of 158 nm. These results indicate that the anodic oxide thickness must be maintained “thin” to facilitate subsequent functional layer preparation and adhesive bonding.
Several additional samples of a 7xxx aluminum alloy (Al—Zn—Mg—Cu style) were processed as per
Without being bound to any particular theory, it is believed that the functionalization creates bonds between organic compounds and phosphorous in the anodic oxide layer, an example of which is
Whereas particular embodiments of this invention have been described above for purposes of illustration, it will be evident to those skilled in the art that numerous variations of the details of the present invention may be made without departing from the invention as defined in the appending claims.
This application is a divisional of U.S. patent application Ser. No. 16/542,678, filed Aug. 16, 2019, now U.S. patent Ser. No. ______, which is a continuation of International Patent Application No. PCT/US2018/020979, filed Mar. 5, 2018, which claims the benefit of priority of U.S. Patent Application No. 62/467,652, filed Mar. 6, 2017, each of which is incorporated herein by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 62467652 | Mar 2017 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 16542678 | Aug 2019 | US |
| Child | 17849370 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/US2018/020979 | Mar 2018 | US |
| Child | 16542678 | US |
