WO2007102831A1 - High strength aluminum alloys and process for making the same - Google Patents
High strength aluminum alloys and process for making the same Download PDFInfo
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- WO2007102831A1 WO2007102831A1 PCT/US2006/010684 US2006010684W WO2007102831A1 WO 2007102831 A1 WO2007102831 A1 WO 2007102831A1 US 2006010684 W US2006010684 W US 2006010684W WO 2007102831 A1 WO2007102831 A1 WO 2007102831A1
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- 229910000838 Al alloy Inorganic materials 0.000 title claims abstract description 13
- 238000000034 method Methods 0.000 title claims description 17
- 229910045601 alloy Inorganic materials 0.000 claims abstract description 83
- 239000000956 alloy Substances 0.000 claims abstract description 83
- 229910052706 scandium Inorganic materials 0.000 claims abstract description 23
- 229910052802 copper Inorganic materials 0.000 claims abstract description 22
- 229910052726 zirconium Inorganic materials 0.000 claims abstract description 18
- 229910052749 magnesium Inorganic materials 0.000 claims abstract description 16
- 229910052725 zinc Inorganic materials 0.000 claims abstract description 14
- 230000032683 aging Effects 0.000 claims abstract description 12
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims abstract description 4
- 229910052782 aluminium Inorganic materials 0.000 claims abstract description 4
- 239000012535 impurity Substances 0.000 claims abstract description 4
- 229910052720 vanadium Inorganic materials 0.000 claims abstract description 4
- 238000010438 heat treatment Methods 0.000 claims description 13
- 230000008018 melting Effects 0.000 claims description 10
- 238000002844 melting Methods 0.000 claims description 10
- 238000001125 extrusion Methods 0.000 claims description 8
- 230000005496 eutectics Effects 0.000 claims description 5
- 238000005266 casting Methods 0.000 claims description 3
- 241000288673 Chiroptera Species 0.000 claims description 2
- 238000005242 forging Methods 0.000 claims description 2
- 229910052742 iron Inorganic materials 0.000 claims description 2
- 239000010949 copper Substances 0.000 abstract description 24
- 239000011777 magnesium Substances 0.000 abstract description 18
- SIXSYDAISGFNSX-UHFFFAOYSA-N scandium atom Chemical compound [Sc] SIXSYDAISGFNSX-UHFFFAOYSA-N 0.000 abstract description 14
- 239000011701 zinc Substances 0.000 abstract description 11
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 abstract description 10
- 229910018569 Al—Zn—Mg—Cu Inorganic materials 0.000 abstract description 7
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 abstract description 6
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 abstract description 4
- 230000015572 biosynthetic process Effects 0.000 abstract description 3
- 238000000265 homogenisation Methods 0.000 abstract description 3
- -1 homogenization Substances 0.000 abstract description 3
- 239000000203 mixture Substances 0.000 description 11
- 239000000243 solution Substances 0.000 description 7
- 238000001953 recrystallisation Methods 0.000 description 6
- QCWXUUIWCKQGHC-UHFFFAOYSA-N Zirconium Chemical compound [Zr] QCWXUUIWCKQGHC-UHFFFAOYSA-N 0.000 description 5
- 230000000694 effects Effects 0.000 description 5
- 238000012545 processing Methods 0.000 description 5
- 238000005275 alloying Methods 0.000 description 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 3
- 238000007792 addition Methods 0.000 description 2
- 238000003483 aging Methods 0.000 description 2
- 230000008901 benefit Effects 0.000 description 2
- 230000000052 comparative effect Effects 0.000 description 2
- 238000005260 corrosion Methods 0.000 description 2
- 230000007797 corrosion Effects 0.000 description 2
- 230000007423 decrease Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 230000009467 reduction Effects 0.000 description 2
- 239000006104 solid solution Substances 0.000 description 2
- 229910000881 Cu alloy Inorganic materials 0.000 description 1
- 229910017539 Cu-Li Inorganic materials 0.000 description 1
- 229910019086 Mg-Cu Inorganic materials 0.000 description 1
- 230000018199 S phase Effects 0.000 description 1
- 229910001297 Zn alloy Inorganic materials 0.000 description 1
- 239000000470 constituent Substances 0.000 description 1
- 230000001276 controlling effect Effects 0.000 description 1
- 230000002596 correlated effect Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 239000003112 inhibitor Substances 0.000 description 1
- 239000001989 lithium alloy Substances 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 238000000386 microscopy Methods 0.000 description 1
- 238000009877 rendering Methods 0.000 description 1
- 238000012552 review Methods 0.000 description 1
- 238000005096 rolling process Methods 0.000 description 1
- 238000005728 strengthening Methods 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C21/00—Alloys based on aluminium
- C22C21/10—Alloys based on aluminium with zinc as the next major constituent
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
- C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
- C22F1/04—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of aluminium or alloys based thereon
- C22F1/053—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of aluminium or alloys based thereon of alloys with zinc as the next major constituent
Definitions
- the present invention relates, in general, to a high strength aluminum alloy ' based on the Al-Zn-Mg-Cu alloy system and a process for forming the same.
- the alloys are particularly suited for use in sporting goods and aerospace applications.
- the highest strength aluminum alloys known at this time are based on the aluminum-zinc-magnesium-copper system.
- Commercial high-strength alloys currently being produced include AA7055 (nominally 8% Zn-2% Mg-2.2% Cu-0.10% Zr), AA7068 (nominally 7.8% Zn-2.5% Mg-2.0% Cu-0.10% Zr) and a Kaiser Aluminum alloy designated K749 (nominally 8% Zn-2.2% Mg-1.8% Cu-0.14% Zr). From the published phase relationships at 86O 0 F for an alloy containing 8% Zn, one can note that K749 is near a phase boundary, while the other two alloys are in multiple phase fields.
- Rich alloys provide more solute, which is potentially available for age hardening to higher strength levels; effective processing ensures that the solute is available for strengthening and not out of solution as second phases, which detract from fracture toughness; and maintaining an unrecrystallized microstructure optimizes both strength and toughness.
- the present invention comprises aluminum alloys based on the Al- Zn-Mg-Cu alloy system that preferably include high levels of zinc and copper, but modest levels of magnesium. As an option, small amounts of scandium can also be employed to prevent recrystallization.
- Each of the alloys preferably includes at least 8.5% Zn and 2.25% Cu by weight. Higher levels of each of these elements up to about 10.5% Zn and 3.0% Cu can be used. However, modestly lower amounts of Mg (max 1.85%) are preferably used to allow higher levels of the Cu.
- the preferred ranges of all elements in the alloys include by weight, 8.5-10.5% Zn, 1.4-1.85 % Mg, 2.25-3.0% Cu, and at least one element from the group Zr, V, or Hf not exceeding about 0.5%, the balance substantially aluminum and incidental impurities.
- 0.05-0.30% Sc is also included in the alloys to prevent recrystallization.
- toughness decreases as the total weight percentage of magnesium and copper increases. Experiments have established that the ideal range of these two elements be between 4.1 and 4.5% combined. Still further, the total weight percent of Zn, Cu and Mg is ideally between 13.0 and 14.5%.
- a homogenization process is preferably employed after alloy ingot casting in which a slow rate of temperature increase is employed as the alloy is heated as near as possible to its melting temperature.
- the rate of increase is limited to 20°F/hr. or less to minimize the amount of low melting point eutectic phases and thereby further enhance fracture toughness of the alloy.
- the product is exposed to a temperature range of 175-310 degrees F for 3 to 30 hours.
- the first step is followed by heating at 310 to 360 degrees F for 2 to 24 hours.
- the product is heated at 175 to 300 degrees F for 1 to 30 hours.
- the second and third aging steps can be used without the first aging step.
- Al-Zn-Mg-Cu alloy system such that they can be more effectively employed in numerous applications.
- Specific products or items in which the subject alloys can be employed include, among others, sporting goods including baseball and soft ball bats, golf shafts, lacrosse sticks, tennis rackets, and arrows; and aerospace application including aerospace components such as wing plates, bulkheads, fuselage stringers, and structural extrusions and forgings; and ordnance parts such as sabots and missile launchers.
- FIG. 1 is a graph depicting T6 strength (YTS and UTS) as a function of the total alloy content in weight percent for a number of sample alloys formed in accordance with the preferred embodiments;
- FIG. 2 is a graph depicting fracture toughness as a function of combined percentages of Cu and Mg for sample alloys formed in accordance with the preferred embodiments;
- FIG. 3 is an equilibrium diagram which depicts the phase relationships at
- FIG. 4 is a graph illustrating the effect of the ratio of Mg to Cu on fracture toughness for the alloys formed in accordance with the preferred embodiments;
- FIG. 5 is a graph depicting second phase volume percent as a function of heating rate in a formation process for Alloy AA7068.
- FIG. 6 is a graph illustrating the effect of scandium on strength of an Al-8%
- Example 1 illustrate how alloy modifications and efficient processing operations can be used to enhance the properties of the Al-Zn-Mg-Cu alloy system in accordance with the preferred embodiments of the present invention, such that they can be more effectively utilized in sporting goods and aerospace applications.
- Example 1 illustrate how alloy modifications and efficient processing operations can be used to enhance the properties of the Al-Zn-Mg-Cu alloy system in accordance with the preferred embodiments of the present invention, such that they can be more effectively utilized in sporting goods and aerospace applications.
- a heretofore unexplored region of the Al-Zn-Mg-Cu alloy system consists of compositions comprising about 9% to 10% zinc, 2.2% to 2.8% copper, and 1.6% to 2.0% magnesium.
- the alloy compositions listed in Table 1 were cast as 9-in. diameter billets: note that all these alloys contain about 0.05% scandium, an element which in combination with zirconium is effective in preventing recrystallization.
- the billets were homogenized at 880F (F means degrees Fahrenheit) and extruded to seamless 4-in. diameter tubes with a 0.305 in. wall thickness.
- the extrusions were solution heat treated at 880F, quenched in cold water and "peak” aged to the T6 temper (24-hr soak at 250F). They were tested for tensile properties in the longitudinal direction and sections from all of the extrusions were cut and flattened to pieces about 12" square, which were also solution heat treated at 880F, quenched in cold water and peak aged. These flattened sections were tested for fracture toughness (ASTM B645) in the T-L orientation. The tensile and fracture toughness properties are listed in Table 2.
- compositions lying below the demarcation line between the solid solution and the Al + S phase regions are single phase alloys, which have superior fracture toughness values for a given strength level, compared to those in the 2-phase region.
- the best combinations of strength and toughness are associated with alloys near the solvus line, which is why the 2.7% Cu/1.9% Mg composition has a relatively low toughness level.
- the preferred compositions therefore lie within the dashed lines that run approximately parallel to the solvus. These relationships are defined by controlling the total copper plus magnesium concentrations between 4.1% and 4.5%.
- the subject alloy can be over aged beyond peak strength in a second step at temperatures in the 310-360F temperature range for 2 to 24 hours to provide a desirable combination of strength and corrosion resistance.
- Another preferred embodiment includes a final aging treatment in a third step at a lower temperature in the range 175-300F for 1 to 30 hours, which provides an additional strength benefit with no loss in corrosion properties.
- the alloy can be subjected only to the aforementioned second and third aging steps by skipping the first step.
- FIG. 4 compares the toughness levels of these alloys on the basis of Mg/Cu ratio with the invention alloys, using those compositions that have similar strength levels (93- 95 ksi) and total Mg + Cu contents (4.0-4.2%).
- the ingots were homogenized at 875F using a 50F/hr heating rate and air cool, and then reheated to 800F and extruded to a 0.25" by 3" flat bar. Sections of each extrusion were annealed at 775F for 3 hr, cooled 50F/hr to 450F, held 4 hr and cooled 50F/hr to room temperature. The sections were then cold rolled to 0.040" sheet using five pass reductions (84% total reduction). The sheets were solution heat treated at 885F for 30 min, quenched in cold water, and then aged to the peak strength condition (10 hr at 305F). The as-extruded bars were also heat treated similarly and both products were tested for transverse tensile properties, as listed below. The specific effects of scandium on strength are also shown in FIG. 6.
- the strongest alloy in both extrusion and sheet form contains 0.06% Sc (with 0.11% Zr)
- 0.06% Sc is effective in raising the strength of the sheet product by about 6 ksi.
- 3. 0.22% Sc in the absence of zirconium raises the strength of the sheet product by only 1 ksi, and lowers the extrusion strength by about 6 ksi.
- the effectiveness of only 0.06% Sc in preventing recrystallization was confirmed by comparing the microstructures of the sheet products containing (a) 0.11% Zr, (b) 0.11% Zr + 0.06% Sc, and (c) 0.22% Sc (no Zr) .
- the preferred range in the alloys for Sc is 0.05-0.30%, with a more preferred range of 0.05-0.10%.
Abstract
High strength aluminum alloys based on the Al-Zn-Mg-Cu alloy system preferably include high levels of zinc and copper, but modest levels of magnesium, to provide increased tensile strength without sacrificing toughness. Preferred ranges of the elements include by weight, 8.5-10.5% Zn, 1.4-1.85 % Mg, 2.25-3.0% Cu and at least one element from the group Zr, V, or Hf not exceeding about 0.5%, the balance substantially aluminum and incidental impurities. In addition, small amounts of scandium (0.05-0.30%) are also preferably employed to prevent recrystalization. During formation of the alloys, homogenization, solution heat treating and artificial aging processes are preferably employed.
Description
High Strength Aluminum Alloys and Process for Making the Same Cross Reference to Related Applications
[0001] This application contains subject matter that is related to the subject matter set forth in US Application No. 10/829,391, which was filed on April 22, 2004. Background Of The Invention
1. Field of the Invention
[0002] The present invention relates, in general, to a high strength aluminum alloy ' based on the Al-Zn-Mg-Cu alloy system and a process for forming the same. Although not limited thereto, the alloys are particularly suited for use in sporting goods and aerospace applications.
2. Description of the Background Art
[0003] The highest strength aluminum alloys known at this time are based on the aluminum-zinc-magnesium-copper system. Commercial high-strength alloys currently being produced include AA7055 (nominally 8% Zn-2% Mg-2.2% Cu-0.10% Zr), AA7068 (nominally 7.8% Zn-2.5% Mg-2.0% Cu-0.10% Zr) and a Kaiser Aluminum alloy designated K749 (nominally 8% Zn-2.2% Mg-1.8% Cu-0.14% Zr). From the published phase relationships at 86O0F for an alloy containing 8% Zn, one can note that K749 is near a phase boundary, while the other two alloys are in multiple phase fields. In the latter case all the alloying elements are not in solid solution at 86O0F, and are not only unavailable for age hardening, but the undissolved phases remaining after heat treatment detract from toughness. Although solution heat treating at a higher temperature than 86O0F will dissolve more of the solute, care has to be taken to ensure that the alloy does not undergo eutectic melting, which is a common problem in commercially cast alloys that have locally enriched regions as a result of microsegregation that occurred during casting. [0004] There is a need in many applications, such as sporting goods and aerospace applications, for even stronger alloys based on the aluminum-zinc-magnesium-copper system that do not sacrifice toughness. However, this requirement presents a problem because, in general, as the tensile strength of an aluminum alloy is increased, its toughness decreases. Summary of the Invention [0005] The present invention addresses the foregoing need in a number of ways.
More particularly, there are three distinct avenues for increasing an alloy's strength while maintaining its toughness: rich alloy chemistries; processing to maximize alloying effectiveness; and preventing recrystallization. Rich alloys provide more solute, which is potentially available for age hardening to higher strength levels; effective processing ensures
that the solute is available for strengthening and not out of solution as second phases, which detract from fracture toughness; and maintaining an unrecrystallized microstructure optimizes both strength and toughness.
[0006] To provide increased tensile strength without sacrificing toughness through the use of rich chemistries, the present invention comprises aluminum alloys based on the Al- Zn-Mg-Cu alloy system that preferably include high levels of zinc and copper, but modest levels of magnesium. As an option, small amounts of scandium can also be employed to prevent recrystallization. Each of the alloys preferably includes at least 8.5% Zn and 2.25% Cu by weight. Higher levels of each of these elements up to about 10.5% Zn and 3.0% Cu can be used. However, modestly lower amounts of Mg (max 1.85%) are preferably used to allow higher levels of the Cu. The preferred ranges of all elements in the alloys include by weight, 8.5-10.5% Zn, 1.4-1.85 % Mg, 2.25-3.0% Cu, and at least one element from the group Zr, V, or Hf not exceeding about 0.5%, the balance substantially aluminum and incidental impurities. In the preferred embodiments, 0.05-0.30% Sc is also included in the alloys to prevent recrystallization. Additionally, it has been found that toughness decreases as the total weight percentage of magnesium and copper increases. Experiments have established that the ideal range of these two elements be between 4.1 and 4.5% combined. Still further, the total weight percent of Zn, Cu and Mg is ideally between 13.0 and 14.5%. [0007] To maximize alloying effectiveness during formation of the alloys, a homogenization process is preferably employed after alloy ingot casting in which a slow rate of temperature increase is employed as the alloy is heated as near as possible to its melting temperature. In particular, for the last 20-300F below the melting temperature, the rate of increase is limited to 20°F/hr. or less to minimize the amount of low melting point eutectic phases and thereby further enhance fracture toughness of the alloy. Once the ingot is formed into finished shape using extrusion and rolling steps, for example, the product is preferably solution heat treated at 870 to 900 degrees F and then artificially aged. The aging process can be carried out by exposing the product to a one, two or three step heat treatment process. In the first step, the product is exposed to a temperature range of 175-310 degrees F for 3 to 30 hours. In the optional second step, the first step is followed by heating at 310 to 360 degrees F for 2 to 24 hours. Finally, in the third optional step, the product is heated at 175 to 300 degrees F for 1 to 30 hours. As a still further option, the second and third aging steps can be used without the first aging step. [0008] The foregoing alloys and processing operations enhance the properties of the
Al-Zn-Mg-Cu alloy system, such that they can be more effectively employed in numerous
applications. Specific products or items in which the subject alloys can be employed include, among others, sporting goods including baseball and soft ball bats, golf shafts, lacrosse sticks, tennis rackets, and arrows; and aerospace application including aerospace components such as wing plates, bulkheads, fuselage stringers, and structural extrusions and forgings; and ordnance parts such as sabots and missile launchers. Brief Description of the Drawings
[0009] The features and advantages of the present invention will become apparent form the following detailed description of a preferred embodiment thereof, taken in conjunction with the accompanying drawings, in which: [0010] FIG. 1 is a graph depicting T6 strength (YTS and UTS) as a function of the total alloy content in weight percent for a number of sample alloys formed in accordance with the preferred embodiments;
[0011] FIG. 2 is a graph depicting fracture toughness as a function of combined percentages of Cu and Mg for sample alloys formed in accordance with the preferred embodiments;
[0012] FIG. 3 is an equilibrium diagram which depicts the phase relationships at
8850F as a function of percentages of Cu and Mg for an alloy formed in accordance with the preferred embodiments that contains 9% Zn; [0013] FIG. 4 is a graph illustrating the effect of the ratio of Mg to Cu on fracture toughness for the alloys formed in accordance with the preferred embodiments;
[0014] FIG. 5 is a graph depicting second phase volume percent as a function of heating rate in a formation process for Alloy AA7068; and
[0015] FIG. 6 is a graph illustrating the effect of scandium on strength of an Al-8%
Zn-2.2% Mg- 1.9% Cu alloy. Detailed Description of the Preferred Embodiments
[0016] The following examples illustrate how alloy modifications and efficient processing operations can be used to enhance the properties of the Al-Zn-Mg-Cu alloy system in accordance with the preferred embodiments of the present invention, such that they can be more effectively utilized in sporting goods and aerospace applications. Example 1
[0017] A heretofore unexplored region of the Al-Zn-Mg-Cu alloy system consists of compositions comprising about 9% to 10% zinc, 2.2% to 2.8% copper, and 1.6% to 2.0% magnesium. The alloy compositions listed in Table 1 were cast as 9-in. diameter billets: note
that all these alloys contain about 0.05% scandium, an element which in combination with zirconium is effective in preventing recrystallization.
[0018] The billets were homogenized at 880F (F means degrees Fahrenheit) and extruded to seamless 4-in. diameter tubes with a 0.305 in. wall thickness. The extrusions were solution heat treated at 880F, quenched in cold water and "peak" aged to the T6 temper (24-hr soak at 250F). They were tested for tensile properties in the longitudinal direction and sections from all of the extrusions were cut and flattened to pieces about 12" square, which were also solution heat treated at 880F, quenched in cold water and peak aged. These flattened sections were tested for fracture toughness (ASTM B645) in the T-L orientation. The tensile and fracture toughness properties are listed in Table 2.
Table 2. Tensile and fracture toughness properties
[0019] As can be seen from Table 2, tensile yield strengths well in excess of 90 ksi were obtained in most of the alloys, with two compositions achieving about 98 ksi. As shown in FIG. 1, strength correlated well with the total alloy content, with each wt. pet. adding about 4.8 ksi to the yield strength. The equilibrium phase relations at the homogenizing and solution heat treatment temperature explain the reason for this behavior. FIG. 3 shows how the compositions listed in Table 1 relate to the magnesium and copper solubility limits at 885F for alloys containing a nominal zinc level of 9%. Compositions lying below the demarcation line between the solid solution and the Al + S phase regions (i.e., the solvus) are single phase alloys, which have superior fracture toughness values for a given strength level, compared to those in the 2-phase region. The best combinations of strength and toughness are associated with alloys near the solvus line, which is why the 2.7% Cu/1.9% Mg composition has a relatively low toughness level. The preferred compositions therefore lie within the dashed lines that run approximately parallel to the solvus. These relationships are defined by controlling the total copper plus magnesium concentrations between 4.1% and 4.5%.
[0020] Although the properties described above were obtained with a "standard" T6 temper aging treatment by exposing the shaped products to heat of between 175 and 310F for 3 to 30 hours (24 hr at 250F was specifically used), as with most Al-Zn-Mg-Cu alloys, other practices may also be advantageous, depending on the desired combination of properties. For example, a tube from composition #213, when drawn to a tube 2.625" in diameter with a 0.110" wall thickness and aged by a 2-step practice of 8 hr at 250F plus 4 hr at 305F had
yield and tensile strengths of 100.9 ksi and 102.6 ksi, respectively. Similarly, the subject alloy can be over aged beyond peak strength in a second step at temperatures in the 310-360F temperature range for 2 to 24 hours to provide a desirable combination of strength and corrosion resistance. Another preferred embodiment includes a final aging treatment in a third step at a lower temperature in the range 175-300F for 1 to 30 hours, which provides an additional strength benefit with no loss in corrosion properties. As yet another alternative, the alloy can be subjected only to the aforementioned second and third aging steps by skipping the first step.
Example 2
[0021] To compare the invention alloy with other commercial high-zinc alloys such as AA7036, AA7056 and AA7449, which have higher Mg/Cu ratios in the range 1.0 to 1.4, the following alloys were prepared as described in Example 1. Table 3. Compositions of Comparative Alloys
The yield strengths and toughness values for these alloys are listed in the following table.
Table 4. Mechanical Properties of Comparative Alloys
[0022] FIG. 4 compares the toughness levels of these alloys on the basis of Mg/Cu ratio with the invention alloys, using those compositions that have similar strength levels (93- 95 ksi) and total Mg + Cu contents (4.0-4.2%).
Example 3
[0023] As noted earlier it is important that undissolved second phases do not remain after processing so that fracture toughness can be maximized. This is especially important in alloys that are rich in alloy content, and lie near an equilibrium solvus phase boundary. To
illustrate how homogenizing practice can affect the amount of such undissolved phase(s), samples of as-cast AA7068 alloy billet were heated from 850F at various rates in a differential scanning calorimeter (DSC), and the energy associated with eutectic melting, which started at about 885F was measured. This energy measurement is directly proportional to the amount of undissolved second phase remaining at the incipient melting point, and the relationship between these factors has been determined by quantitative microscopy. FIG. 5 shows how heating rate affects the amount of this phase as determined from the DSC data. [0024] Note that a slow heating rate of about 1 OF/hr reduces the amount of second phase to a level below 1 vol.%. One would expect that a ~5F/hr heating rate would reduce the "soluble" portion to near zero. We also note that for heating rates of 10-20F/hr, the volume fraction of undissolved eutectic is no greater than the amount of insoluble Fe- containing constituent (independent of heating rate or homogenization temperature) at a nominal 0.12% Fe level (approx. 1 vol.%). Example 4 [0025] It has been recognized for a number of years that scandium in combination with zirconium is an effective recrystallization inhibitor. A Russian review article states "it is desirable to add scandium to aluminum alloys in a quantity from 0.1 to 0.3% together with zirconium (0.05-0.15%)". However, "the greatest effect .... is observed for alloys not containing alloy elements combining with scandium in insoluble phases...; with a limited copper content [scandium combines with copper] alloying with scandium together with zirconium of Al-Zn-Mg-Cu and Al-Cu-Li alloys is possible". As such, "commercial alloys based on Al-Zn-Mg-Sc-Zr (01970, 01975) have been developed".
[0026] Two potential drawbacks to scandium additions to 7XXX alloys containing about 2% copper are evident: 1) the copper level is high enough to combine with scandium, thereby rendering it ineffective, and
2) the high price of scandium; at the 0.2% level it would add about $10 a pound to the cost of the aluminum alloy. [0027] It would therefore be economically and technically attractive if scandium levels could be effectively used below those recommended in the Russian literature.
[0028] Alloys of the compositions listed in the following table were prepared as 5" diameter billets, which were processed as described below. Although the sample alloys contained more Mg and less Cu than the preferred alloys discussed previously, it is believed that the effect of Sc addition to the alloys would be essentially the same for the preferred
alloys.
[0029] The ingots were homogenized at 875F using a 50F/hr heating rate and air cool, and then reheated to 800F and extruded to a 0.25" by 3" flat bar. Sections of each extrusion were annealed at 775F for 3 hr, cooled 50F/hr to 450F, held 4 hr and cooled 50F/hr to room temperature. The sections were then cold rolled to 0.040" sheet using five pass reductions (84% total reduction). The sheets were solution heat treated at 885F for 30 min, quenched in cold water, and then aged to the peak strength condition (10 hr at 305F). The as-extruded bars were also heat treated similarly and both products were tested for transverse tensile properties, as listed below. The specific effects of scandium on strength are also shown in FIG. 6.
[0030] A number of points are evident from these results:
1. The strongest alloy in both extrusion and sheet form contains 0.06% Sc (with 0.11% Zr)
2. At the 0.1% Zr level, 0.06% Sc is effective in raising the strength of the sheet product by about 6 ksi.
3. 0.22% Sc in the absence of zirconium raises the strength of the sheet product by only 1 ksi, and lowers the extrusion strength by about 6 ksi. The effectiveness of only 0.06% Sc in preventing recrystallization was confirmed by comparing the microstructures of the sheet products containing (a) 0.11% Zr, (b) 0.11% Zr + 0.06% Sc, and (c) 0.22% Sc (no Zr) . In view of the foregoing, the preferred range in the alloys for Sc is 0.05-0.30%, with a more preferred range of 0.05-0.10%.
[0031] Although the present invention has been described in terms of a number of preferred embodiments and variations thereon, it will be understood that numerous additional variations and modifications may be made without departing from the scope of the invention. Thus, it is to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described above.
Claims
1. An aluminum alloy product having high strength with good toughness, containing by weight, 8.5-10.5% Zn, 1.4-1.85 % Mg, 2.25-3.0% Cu, and at least one element from the group Zr, V, or Hf not exceeding about 0;5%, the balance substantially aluminum and incidental impurities.
2. The alloy product of claim 1, wherein said alloy contains about 0.05-0.2% Zr.
3. The alloy product of claim 1, wherein said alloy includes 0.05-0.30% Sc.
4. The alloy product of claim 3, wherein said alloy includes 0.05-0.20% Zr.
5. The alloy product of claim 1, wherein said alloy includes about 0.03-0.10% Si and
0.03-0.12% Fe.
6. The alloy product of claim 1, wherein the combined weight percentages of Mg and Cu range from 4.1 to 4.5%.
7. The alloy product of claim 6, wherein the combined weight percentages of Zn, Mg and Cu range from 13.0 to 14.5%.
8. The aluminum alloy product of claim 1, wherein said product is selected from the group including sporting goods such as baseball and soft ball bats, golf shafts, lacrosse sticks, tennis rackets, and arrows; aerospace components such as wing plates, bulkheads, fuselage stringers, and structural extrusions and forgings; and ordnance parts such as sabots and missile launchers.
9. A process for making an aluminum alloy product containing 8.5-10.5% Zn, 1.4-
1.85 % Mg, 2.25-3.0% Cu, and at least one element from the group Zr, V, or Hf not exceeding about 0.5%, the balance substantially aluminum and incidental impurities, said method including the steps of: casting said alloy product to form an alloy ingot; and
homogenizing said alloy ingot to minimize the amount of low melting point eutectic phases therein by heating said ingot at a heating rate of no more than 20°F/hr. from a first temperature at least about 2O0F below the melting temperature of said ingot to a second temperature of about 50F below said melting temperature.
10. The process of claim 9, wherein said first temperature is about 3O0F below said melting temperature.
11. The process of claim 9, wherein said first temperature is selected to be about 87O0F and said second temperature is selected to be in the range of 885-8900F.
12. The process of claim 9 where the alloy ingot is held at said first temperature for at least 8 hours.
13. The process of claim 9, wherein said alloy contains 0.05-0.30 % Sc.
14. The process of claim 9, wherein said alloy ingot is formed into a shape of a finished product, solution heat treated at 870 to 900 degrees F and then artificially aged in a first aging step by being heated at 175-310 degrees F for 3 to 30 hours.
15. The process of claim 14, wherein said product is exposed to a second aging step by being heated at 310 to 360 degrees F for 2 to 24 hours.
16. The process of claim 15, wherein said alloy product is exposed to a third aging step by being heated at 175 to 300 degrees F for 1 to 30 hours.
17. The process of claim 9, wherein said alloy ingot is formed into a shape of a finished product, solution heat treated and then artificially aged in a first aging step by being heated at 310 to 360 degrees F for 2 to 24 hours.
18. The process of claim 17, wherein said alloy product is exposed to a second aging step by being heated at 175 to 300 degrees F for 1 to 30 hours.
Priority Applications (3)
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SI200632270T SI1902150T1 (en) | 2005-03-24 | 2006-03-22 | High strength aluminum alloys and process for making the same |
CN2006800173184A CN101193839B (en) | 2005-03-24 | 2006-03-22 | High strength aluminum alloys and process for making the same |
EP06849740.3A EP1902150B1 (en) | 2005-03-24 | 2006-03-22 | High strength aluminum alloys and process for making the same |
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US11/087,733 US20060213591A1 (en) | 2005-03-24 | 2005-03-24 | High strength aluminum alloys and process for making the same |
US11/087,733 | 2005-03-24 |
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US (2) | US20060213591A1 (en) |
EP (1) | EP1902150B1 (en) |
CN (1) | CN101193839B (en) |
SI (1) | SI1902150T1 (en) |
WO (1) | WO2007102831A1 (en) |
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US9068252B2 (en) * | 2009-03-05 | 2015-06-30 | GM Global Technology Operations LLC | Methods for strengthening slowly-quenched/cooled cast aluminum components |
US8636855B2 (en) | 2009-03-05 | 2014-01-28 | GM Global Technology Operations LLC | Methods of enhancing mechanical properties of aluminum alloy high pressure die castings |
US9163304B2 (en) | 2010-04-20 | 2015-10-20 | Alcoa Inc. | High strength forged aluminum alloy products |
EP2684224B1 (en) * | 2011-03-07 | 2019-05-08 | Lumileds Holding B.V. | A light emitting module, a lamp, a luminaire and a display device |
US20120247623A1 (en) * | 2011-04-04 | 2012-10-04 | Matuska Robert A | Optimization and Control of Metallurgical Properties During Homogenization of an Alloy |
CN103572129A (en) * | 2013-11-05 | 2014-02-12 | 吴高峰 | Preparation method of aluminum alloy for golf clubs |
CN103572127A (en) * | 2013-11-05 | 2014-02-12 | 吴高峰 | Aluminium alloy for golf clubs |
CN103572128A (en) * | 2013-11-05 | 2014-02-12 | 吴高峰 | Aluminium alloy for golf clubs and preparation method |
CN103898382B (en) * | 2014-03-27 | 2017-01-04 | 北京科技大学 | Superpower high-ductility corrosion Al Zn Mg Cu aluminum alloy materials and preparation method thereof |
CN104152761A (en) * | 2014-07-31 | 2014-11-19 | 天津大学 | Sc-containing Al-Zn-Mg-Cu-Zr alloy and preparation method thereof |
CN104862551B (en) * | 2015-05-21 | 2017-09-29 | 北京科技大学 | Al Mg Cu Zn line aluminium alloys and aluminum alloy plate materials preparation method |
JP6661870B2 (en) * | 2016-05-13 | 2020-03-11 | 日本軽金属株式会社 | Aluminum alloy base tube for bat, bat and method for manufacturing the same |
CN106422240A (en) * | 2016-11-11 | 2017-02-22 | 佛山市南海区卓航五金厂 | Table tennis net frame |
CN107099706A (en) * | 2017-05-02 | 2017-08-29 | 嘉禾福顺机械实业有限公司 | A kind of high rigidity materials for prups and preparation method thereof |
CN109266879A (en) * | 2018-11-20 | 2019-01-25 | 天津百恩威新材料科技有限公司 | A kind of Bradley bistrique and high-strength aluminum alloy are preparing the application in Bradley bistrique |
CN111519057B (en) * | 2020-05-22 | 2021-11-23 | 佛山市三水凤铝铝业有限公司 | Method for prolonging service life of die for preparing aluminum alloy |
CN114346217A (en) * | 2021-12-22 | 2022-04-15 | 中山市奥博精密科技有限公司 | Metal casting and preparation method and application thereof |
CN114457266A (en) * | 2021-12-27 | 2022-05-10 | 有研金属复材技术有限公司 | Ultrahigh-strength and toughness cast aluminum alloy and forming method thereof |
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-
2006
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- 2006-03-22 EP EP06849740.3A patent/EP1902150B1/en not_active Revoked
- 2006-03-22 CN CN2006800173184A patent/CN101193839B/en active Active
- 2006-03-22 WO PCT/US2006/010684 patent/WO2007102831A1/en active Application Filing
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Also Published As
Publication number | Publication date |
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EP1902150B1 (en) | 2018-06-20 |
US20100180988A1 (en) | 2010-07-22 |
SI1902150T1 (en) | 2018-08-31 |
EP1902150A4 (en) | 2016-09-07 |
EP1902150A1 (en) | 2008-03-26 |
CN101193839A (en) | 2008-06-04 |
US20060213591A1 (en) | 2006-09-28 |
CN101193839B (en) | 2010-07-14 |
WO2007102831A8 (en) | 2007-11-29 |
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