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WO2024225720A1 - Plaque épaisse d'alliage d'aluminium-zinc-magnésium-cuivre à haute résistance et son procédé de production - Google Patents

Plaque épaisse d'alliage d'aluminium-zinc-magnésium-cuivre à haute résistance et son procédé de production Download PDF

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Publication number
WO2024225720A1
WO2024225720A1 PCT/KR2024/005456 KR2024005456W WO2024225720A1 WO 2024225720 A1 WO2024225720 A1 WO 2024225720A1 KR 2024005456 W KR2024005456 W KR 2024005456W WO 2024225720 A1 WO2024225720 A1 WO 2024225720A1
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Prior art keywords
aluminum
zinc
magnesium
thick plate
aluminum alloy
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English (en)
Korean (ko)
Inventor
조용희
김형욱
이윤수
김원경
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Korea Institute of Materials Science KIMS
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Korea Institute of Materials Science KIMS
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D21/00—Casting non-ferrous metals or metallic compounds so far as their metallurgical properties are of importance for the casting procedure; Selection of compositions therefor
    • B22D21/02—Casting exceedingly oxidisable non-ferrous metals, e.g. in inert atmosphere
    • B22D21/04—Casting aluminium or magnesium
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/46—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals
    • 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 technical idea of the present invention relates to a method for manufacturing an aluminum alloy, and more specifically, to a high-strength aluminum-zinc-magnesium-copper alloy thick plate and a method for manufacturing the same.
  • the 7000 series aluminum alloy has a disadvantage in that, although the strength increases as the content of added elements such as zinc, magnesium, and copper increases, the fraction of secondary phases inside the casting increases, making it easy for casting defects to occur, and the mechanical properties deteriorate due to these secondary phases. Therefore, there is an increasing demand for thick plates with excellent mechanical properties by reducing the fraction of secondary phases and having fine grains.
  • hot rolling of mass-produced 7000 series aluminum alloy slabs is usually performed using hot rolling rolls heated to a high temperature.
  • heating the hot rolling rolls is expensive. Therefore, a technology is required to manufacture aluminum alloy thick plates by hot rolling 7000 series aluminum alloy slabs at room temperature without heating the hot rolling rolls.
  • the technical problem to be achieved by the technical idea of the present invention is to provide a high-strength aluminum-zinc-magnesium-copper alloy thick plate and a method for manufacturing the same, which can perform hot rolling using hot rolling rolls at room temperature, and improve mechanical properties by preventing defects by reducing the secondary phase fraction.
  • a high-strength aluminum-zinc-magnesium-copper alloy thick plate and a method for manufacturing the same are provided.
  • the method for manufacturing the high-strength aluminum-zinc-magnesium-copper alloy thick plate may include a casting step of melting alloy elements corresponding to an aluminum alloy including 5 wt% to 8 wt% of zinc (Zn), 2 wt% to 3 wt% of magnesium (Mg), 1 wt% to 2 wt% of copper (Cu), and the remainder being aluminum (Al) and other unavoidable impurities, and casting the molten metal to form an aluminum alloy cast material; a multi-stage homogenization step of performing a multi-stage homogenization treatment on the aluminum alloy cast material to form an aluminum alloy homogenized material; a reheating step of heating the aluminum alloy homogenized material to a temperature in the range of 300°C to 400°C; and a hot rolling step of hot-rolling the reheated aluminum alloy homogenized material to form an aluminum alloy thick plate.
  • a casting step of melting alloy elements corresponding to an aluminum alloy including 5 wt% to 8 wt% of zinc (
  • the multi-stage homogenization treatment step may include a step of first homogenizing the aluminum alloy cast material at a temperature ranging from 450° C. to 475° C. for more than 6 hours to less than 24 hours; and a step of second homogenizing the aluminum alloy cast material subjected to the first homogenization treatment at a temperature ranging from 470° C. to 490° C. for 1 hour to less than 4 hours.
  • the temperature of the second homogenization treatment step may be higher than the temperature of the first homogenization treatment step.
  • the hot rolling step can be performed using a hot rolling roll at room temperature.
  • the method may further include a solution treatment step of solution treating the aluminum alloy thick plate at a temperature ranging from 420°C to 500°C for 30 minutes to 5 hours.
  • the method may further include an aging treatment step of aging the aluminum alloy thick plate at a temperature ranging from 100° C. to 200° C. for 5 to 30 hours.
  • the method may further include a solution treatment step of treating the aluminum alloy thick plate with a solution at a temperature ranging from 420° C. to 500° C. for 30 minutes to 5 hours; and an aging treatment step of treating the aluminum alloy thick plate with a solution at a temperature ranging from 100° C. to 200° C. for 5 hours to 30 hours.
  • the aluminum alloy may further include at least one of chromium (Cr) of 0.3 wt% or less, titanium (Ti) of 0.1 wt% or less, and zirconium (Zr) of 0.1 wt% or less.
  • Cr chromium
  • Ti titanium
  • Zr zirconium
  • the aluminum alloy casting material may have an average grain size in a range of 50 ⁇ m to 80 ⁇ m.
  • the aluminum alloy casting material may have a thickness in a range of 120 mm to 200 mm, and the aluminum alloy thick plate may have a thickness in a range of 25 mm to 40 mm.
  • the high-strength aluminum-zinc-magnesium-copper alloy thick plate contains 5 wt% to 8 wt% of zinc (Zn), 2 wt% to 3 wt% of magnesium (Mg), 1 wt% to 2 wt% of copper (Cu), and the remainder being aluminum (Al) and other unavoidable impurities, and the aluminum-zinc-magnesium-copper alloy thick plate can satisfy a yield strength (YS): 450 MPa or more, a tensile strength (UTS): 520 MPa or more, and an elongation (EL): 10% or more.
  • YS yield strength
  • UTS tensile strength
  • EL elongation
  • the aluminum-zinc-magnesium-copper alloy thick plate can have a recrystallized fraction of 50 to 80 volume%.
  • the aluminum-zinc-magnesium-copper alloy thick plate may further include at least one of 0.3 wt% or less of chromium (Cr), 0.1 wt% or less of titanium (Ti), and 0.1 wt% or less of zirconium (Zr).
  • Cr chromium
  • Ti titanium
  • Zr zirconium
  • a method for manufacturing a high-strength aluminum-zinc-magnesium-copper alloy thick plate can provide a high-strength aluminum-zinc-magnesium-copper alloy thick plate having excellent mechanical properties by minimizing the fraction of compounds existing in a casting material through a multi-stage homogenization treatment to improve the mechanical properties of the thick plate, and controlling the reheating heat treatment temperature to suppress breakage occurring during rolling for hot rolling using a roll at room temperature.
  • FIG. 1 is a process flow diagram schematically showing a method for manufacturing a high-strength aluminum-zinc-magnesium-copper alloy thick plate according to one embodiment of the present invention.
  • FIG. 2 is a schematic diagram showing changes in process time and process temperature in a method for manufacturing a high-strength aluminum-zinc-magnesium-copper alloy thick plate according to one embodiment of the present invention.
  • FIGS. 3a to 3c are graphs showing the results of thermodynamic calculations for aluminum alloy design in a method for manufacturing a high-strength aluminum-zinc-magnesium-copper alloy thick plate according to one embodiment of the present invention.
  • FIG. 4 is an optical microscope photograph showing the microstructure of an aluminum alloy casting manufactured according to a method for manufacturing a high-strength aluminum-zinc-magnesium-copper alloy thick plate according to an embodiment of the present invention.
  • FIGS. 5a and 5b are differential scanning calorimetry graphs of an aluminum alloy manufactured according to a method for manufacturing a high-strength aluminum-zinc-magnesium-copper alloy thick plate according to one embodiment of the present invention.
  • FIGS. 6 and 7 are optical microscope photographs showing changes in the microstructure according to the homogenization time of an aluminum alloy manufactured according to a method for manufacturing a high-strength aluminum-zinc-magnesium-copper alloy thick plate according to an embodiment of the present invention.
  • FIGS. 8a and 8b are graphs showing the compound fraction according to the homogenization time of an aluminum alloy manufactured by a method for manufacturing a high-strength aluminum-zinc-magnesium-copper alloy thick plate according to an embodiment of the present invention.
  • FIGS. 9a and 9b are graphs showing the hardness according to the homogenization time of an aluminum alloy manufactured by a method for manufacturing a high-strength aluminum-zinc-magnesium-copper alloy thick plate according to an embodiment of the present invention.
  • FIG. 10 is a photograph showing the results of hot rolling according to the reheating temperature of an aluminum alloy manufactured by a method for manufacturing a high-strength aluminum-zinc-magnesium-copper alloy thick plate according to an embodiment of the present invention.
  • FIGS. 11a, 11b, and 11c are scanning electron microscope photographs showing cross-sections of aluminum alloy plates manufactured by a method for manufacturing high-strength aluminum-zinc-magnesium-copper alloy plates according to one embodiment of the present invention.
  • FIG. 12 is a graph showing the strength and elongation of an aluminum alloy plate manufactured by a method for manufacturing a high-strength aluminum-zinc-magnesium-copper alloy plate according to an embodiment of the present invention.
  • FIG. 13 is a graph showing fatigue characteristics of an aluminum alloy thick plate manufactured by a method for manufacturing a high-strength aluminum-zinc-magnesium-copper alloy thick plate according to an embodiment of the present invention.
  • FIG. 14 is a graph showing the fracture toughness of an aluminum alloy plate manufactured by a method for manufacturing a high-strength aluminum-zinc-magnesium-copper alloy plate according to an embodiment of the present invention.
  • alloy is used to refer to other elements added intentionally or unintentionally, excluding aluminum, in an aluminum-zinc-magnesium-copper alloy thick plate.
  • compound described in this specification means all kinds of compounds that are not dissolved in an aluminum matrix but are formed as precipitates or crystallized at grain boundaries or within grains and are distinguished, and includes secondary phases commonly referred to in aluminum alloys.
  • the technical idea of the present invention is to provide a high-strength aluminum-zinc-magnesium-copper alloy thick plate having excellent mechanical properties and a method for manufacturing the same by controlling the composition range and optimizing the multi-stage homogenization heat treatment and reheating temperature, thereby enabling hot rolling using room temperature rolling rolls.
  • a high-strength aluminum-zinc-magnesium-copper alloy thick plate which is one aspect of the present invention, contains 5 to 8 wt% of zinc (Zn), 2 to 3 wt% of magnesium (Mg), 1 to 2 wt% of copper (Cu), and the remainder being aluminum (Al) and other unavoidable impurities.
  • the high-strength aluminum-zinc-magnesium-copper alloy thick plate may further include at least one of 0.3 wt % or less of chromium (Cr), 0.1 wt % or less of titanium (Ti), and 0.1 wt % or less of zirconium (Zr).
  • the high-strength aluminum-zinc-magnesium-copper alloy thick plate may further include at least one of 0.01 wt % to 0.3 wt % of chromium (Cr), 0.01 wt % to 0.1 wt % of titanium (Ti), and 0.01 wt % to 0.1 wt % of zirconium (Zr).
  • the role and content of each component included in the high-strength aluminum-zinc-magnesium-copper alloy thick plate according to the present invention will be described as follows.
  • the content of the component elements all refers to weight%.
  • Zinc (Zn) 5 wt% to 8 wt%
  • Zinc is an element that improves the strength of aluminum-zinc-magnesium-copper alloy thick plates.
  • the zinc content is less than 5 wt%, it may be difficult to secure strength.
  • the zinc content exceeds 8 wt%, the fluidity of the molten metal may decrease, resulting in poor castability, and segregation may occur in the center of the alloy thick plates being manufactured, which may deteriorate the mechanical properties. Therefore, it is preferable that zinc be added in an amount of 5 wt% to 8 wt% of the total weight of the thick plates.
  • Magnesium is a solid-solution reinforcing element that is dissolved in the matrix of an aluminum-zinc-magnesium-copper alloy thick plate to improve strength and formability.
  • the magnesium content is less than 2 wt%, it may be difficult to secure strength and improve formability.
  • the magnesium content exceeds 3 wt%, the elongation is significantly reduced, which may cause cracks. Therefore, it is preferable that magnesium is added in an amount of 2 wt% to 3 wt% of the total weight of the thick plate.
  • Copper is an element that improves the strength and formability of aluminum-zinc-magnesium-copper alloy thick plates.
  • the copper content is less than 1 wt%, it may be difficult to secure strength and improve formability.
  • the copper content exceeds 2 wt%, cracks may form due to segregation during casting. Therefore, it is preferable that copper be added in an amount of 1 wt% to 2 wt% of the total weight of the thick plate.
  • Chromium has the effect of suppressing recrystallization and thus refining grains, and can be added as a refiner in the form of, for example, an aluminum master alloy containing chromium, but is not limited to, the above-mentioned refiner.
  • the content of chromium is less than 0.01 wt%, the effect of refining grains may not be present.
  • the content of chromium exceeds 0.3 wt%, coarse intermetallic compounds may be formed, thereby reducing ductility. Therefore, it is preferable that chromium be added in an amount of 0.5 wt% or less, for example, 0.01 wt% to 0.3 wt%, of the total weight of the thick plate.
  • Titanium has the effect of suppressing recrystallization and refining grains, and can be added as a refining agent containing titanium, for example, an aluminum master alloy containing titanium, for example, Al-5Ti-1B, which is an Al-Ti-B grain refining agent, but is not limited to the above-mentioned refining agents.
  • a refining agent containing titanium for example, an aluminum master alloy containing titanium, for example, Al-5Ti-1B, which is an Al-Ti-B grain refining agent, but is not limited to the above-mentioned refining agents.
  • the content of titanium is less than 0.01 wt%, the effect of refining grains may not be present.
  • the content of titanium exceeds 0.1 wt%, a coarse intermetallic compound may be formed, which may reduce ductility. Therefore, titanium is preferably added in an amount of 0.1 wt% or less of the total weight of the thick plate, for example, 0.01 wt% to 0.1 wt
  • Zirconium has the effect of suppressing recrystallization and refining grains, and can be added as a refiner in the form of, for example, an aluminum master alloy containing zirconium, but is not limited to, the above-mentioned refiner.
  • the content of zirconium is less than 0.01 wt%, the effect of refining grains may not be present.
  • zirconium exceeds 0.1 wt%, coarse intermetallic compounds may be formed, which may reduce ductility. Therefore, zirconium is preferably added in an amount of 0.1 wt% or less of the total weight of the thick plate, for example, 0.01 wt% to 0.1 wt%.
  • the technical idea of the present invention is not limited to the composition of the alloy, and can comprehensively include alloy compositions that can be used as 7000 series aluminum alloy thick plates, such as 7075 series, 7050 series, and 7068 series.
  • the high-strength aluminum-zinc-magnesium-copper alloy thick plate can have its mechanical properties variously changed by subsequent hot rolling and heat treatment.
  • the above high-strength aluminum-zinc-magnesium-copper alloy thick plate can satisfy, for example, yield strength (YS): 450 MPa or more, tensile strength (UTS): 520 MPa or more, and elongation (EL): 10% or more, and can satisfy, for example, yield strength (YS): 450 MPa to 650 MPa, tensile strength (UTS): 520 MPa to 720 MPa, and elongation (EL): 10% to 16%.
  • the above high-strength aluminum-zinc-magnesium-copper alloy thick plate can have a recrystallization fraction of 50 to 80 volume%.
  • the recrystallization fraction can be reduced by adding chromium (Cr), zirconium (Zr), etc. It can also be changed by the reduction ratio during hot rolling.
  • FIG. 1 is a process flow diagram schematically showing a method (S100) for manufacturing a high-strength aluminum-zinc-magnesium-copper alloy thick plate according to one embodiment of the present invention.
  • FIG. 2 is a schematic diagram showing changes in process time and process temperature in a method for manufacturing a high-strength aluminum-zinc-magnesium-copper alloy thick plate according to one embodiment of the present invention.
  • the method (S100) for manufacturing the high-strength aluminum-zinc-magnesium-copper alloy thick plate includes a casting step (S110); a multi-stage homogenization treatment step (S120); a reheating step (S130); a hot rolling step (S140); a solution treatment step (S150); and an aging treatment step (S160).
  • the above casting step (S110) is a step of casting after melting alloy elements constituting the aluminum-zinc-magnesium-copper alloy plate to form a molten metal.
  • alloy elements corresponding to an aluminum alloy including 5 wt% to 8 wt% of zinc (Zn), 2 wt% to 3 wt% of magnesium (Mg), 1 wt% to 2 wt% of copper (Cu), and the remainder including aluminum (Al) and other unavoidable impurities may be melted to form a molten metal.
  • the molten metal may further include at least one of 0.3 wt% or less of chromium (Cr), 0.1 wt% or less of titanium (Ti), and 0.1 wt% or less of zirconium (Zr).
  • the above alloying elements can be melted in a graphite crucible using a high-frequency induction melting furnace at a temperature at which the alloying elements are completely melted.
  • the alloying elements can be added individually, or all or part of the alloying elements can be added in the form of a master alloy.
  • zinc can be added to the aluminum molten metal in the form of a pure element, or in the form of an aluminum-zinc master alloy having a high zinc content. This method can also be applied to other additive elements such as magnesium and copper.
  • the above molten metal can be poured into a slab mold and solidified to form an aluminum alloy casting.
  • the above aluminum alloy casting can be performed by a DC (direct chilled) continuous casting method, but this is exemplary and the technical idea of the present invention is not limited thereto.
  • the above aluminum alloy casting material can be air-cooled to room temperature.
  • this is exemplary, and a case in which subsequent multi-stage homogenization treatment is continuously performed immediately after casting without air-cooling is also included in the technical concept of the present invention.
  • the above aluminum alloy casting material may have a crystal grain size of 150 ⁇ m or less and an average crystal grain size in the range of 50 ⁇ m to 80 ⁇ m.
  • the multi-stage homogenization treatment step (S120) is a step of heating and homogenizing the aluminum alloy casting material to form an aluminum alloy homogenized material.
  • the multi-stage homogenization treatment step (S120) may include a first homogenization treatment step and a second homogenization treatment step.
  • the aluminum alloy casting material can be first homogenized at a temperature ranging from 450°C to 475°C for more than 6 hours to less than 24 hours.
  • the first homogenization treatment step can be performed for, for example, from 9 hours to 12 hours.
  • the aluminum alloy casting material that has been subjected to the first homogenization treatment can be subjected to the second homogenization treatment at a temperature in the range of 470°C to 490°C for 1 hour to less than 4 hours.
  • the temperature of the second homogenization treatment step is preferably higher than the temperature of the first homogenization treatment step.
  • the first homogenization treatment step can be performed at a temperature of 460°C for 12 hours
  • the second homogenization treatment step can be performed at a temperature of 475°C for 2 hours.
  • homogenization treatment homogenization of the internal structure of the aluminum alloy is achieved, and in particular, compounds precipitated during the casting process can be re-dissolved into the aluminum matrix.
  • the total time required for the homogenization treatment can be reduced.
  • the aluminum alloy homogenized material formed by the above homogenization treatment can be air-cooled to room temperature.
  • the aluminum alloy homogenizer can be ground to remove surface defects, thereby preventing occurrence of defects in subsequent hot rolling.
  • the above reheating step (S130) is a step of reheating the aluminum alloy homogenized material for hot rolling.
  • the above reheating step (S130) can be performed by heating the aluminum alloy homogenized material and maintaining it at a temperature in the range of 300°C to 400°C for 1 to 4 hours, and can be performed by maintaining it for about 2 hours, for example.
  • the present invention has the technical characteristic of using hot rolling rolls at room temperature.
  • the reheating temperature is important. If the reheating temperature is lower than 300°C, the load applied to the hot rolling roll increases, making hot rolling impossible. If the reheating temperature is 400°C or higher, the thermal shock caused by the temperature difference between the aluminum alloy homogenizer and the hot rolling roll may be too large, causing the rolled material to be destroyed during hot rolling.
  • the above hot rolling step (S140) is a step of forming an aluminum alloy thick plate by hot rolling the reheated aluminum alloy homogenized material at a temperature ranging from 300°C to 400°C.
  • the above hot rolling can be performed using a pair of hot rolling rolls that rotate at a speed of 50 m/min to 70 m/min and have a temperature in the range of room temperature, for example, 0°C to 40°C.
  • the speed of the hot rolling rolls is less than 50 m/min, it may be difficult to generate shear deformation, which helps improve the formability of the thick plate by giving rolling deformation to the entire thick plate.
  • the speed of the hot rolling rolls exceeds 70 m/min, it may not be possible to cause deformation to the center of the thick plate.
  • the above hot rolling can be performed at a reduction ratio of less than 4% to less than 10%, and can be performed at an average reduction ratio of 7%.
  • the reduction ratio is less than 4%, the process time and cost may increase because many repeated rollings must be performed.
  • the reduction ratio is 10% or more, significant cracks may occur in the thick plate, which may deteriorate the surface quality and mechanical properties.
  • the above hot rolling can be performed repeatedly until a desired thickness is obtained.
  • the aluminum alloy casting material or the aluminum alloy homogenized material before performing hot rolling can have a thickness in the range of 120 mm to 200 mm (120T to 200T), and the aluminum alloy thick plate formed by performing hot rolling can have a thickness in the range of 25 mm to 40 mm (25T to 40T).
  • the aluminum alloy thick plate After performing the above hot rolling step (S140), the aluminum alloy thick plate can be cooled to room temperature by air cooling, for example, to a temperature in the range of 0°C to 40°C.
  • the hot-rolled aluminum alloy thick plate is solution treated.
  • the above-described solution treatment step (S150) can be performed by heating the aluminum alloy thick plate and maintaining it at a temperature in the range of, for example, 420°C to 500°C for 30 minutes to 5 hours, and can be performed at, for example, 470°C for 1 hour.
  • water-cooling quenching is performed so that the aluminum alloy thick plate can be cooled to room temperature, for example, to a temperature in the range of 0°C to 40°C.
  • the solution treatment the product phase formed by hot rolling can be decomposed, and the compositional uniformity of the aluminum matrix can be improved.
  • water-cooling quenching is performed so that the aluminum alloy thick plate can be cooled to room temperature, for example, to a temperature in the range of 0°C to 40°C.
  • the aluminum alloy thick plate that has been solution-treated is subjected to aging treatment.
  • the aging treatment step (S160) can be performed by heating the aluminum alloy thick plate and maintaining it at a temperature ranging from 100°C to 200°C for 5 to 30 hours, for example, and can be performed at 120°C for 24 hours, for example.
  • water cooling quenching may be performed so that the aluminum alloy thick plate may be cooled to room temperature, for example, to a temperature in the range of 0°C to 40°C.
  • solute elements may be extracted from the supersaturated solid solution to form an aging precipitation phase.
  • water cooling quenching may be performed so that the aluminum alloy thick plate may be cooled to room temperature, for example, to a temperature in the range of 0°C to 40°C.
  • the above solution treatment step (S150) and the aging treatment step (S160) may be performed sequentially. Alternatively, only the solution treatment step (S150) may be performed, or only the aging treatment step (S160) may be performed.
  • Table 1 shows the alloy composition of an aluminum alloy manufactured according to a method for manufacturing a high-strength aluminum-zinc-magnesium-copper alloy thick plate according to one embodiment of the present invention.
  • the alloy composition in Table 1 refers to weight %, and the remainder includes aluminum (Al) and inevitable impurities.
  • Table 1 shows the target composition and actual composition of aluminum alloys.
  • the target composition for example, "Al-5.6Zn-2.5Mg-1.5Cu” means that it contains 5.6 wt% zinc, 2.5 wt% magnesium, and 1.5 wt% copper, and the remainder is aluminum, etc.
  • Table 1 shows the contents of chromium (Cr), titanium (Ti), and zirconium (Zr) added as refiners.
  • Cr chromium
  • Ti titanium
  • Zr zirconium
  • the contents of iron (Fe) and silicon (Si) which were added as unavoidable impurities but not intentionally, are shown underlined.
  • the ratio of zinc to magnesium (Zn/Mg) was 2.24 for the cast material, the first homogenizer, and Example 1, 2.48 for Example 2, and 3.12 for Example 3.
  • Aluminum alloy castings were manufactured by performing DC continuous casting of the aluminum alloys in Table 1.
  • the castings had dimensions of 350 mm in width, 150 mm in thickness, and 600 mm in length.
  • FIGS. 3A to 3C are graphs showing the results of thermodynamic calculations for aluminum alloy design in a method for manufacturing a high-strength aluminum-zinc-magnesium-copper alloy thick plate according to one embodiment of the present invention.
  • FIG. 3A is for the case of Example 1
  • FIG. 3B is for the case of Example 2
  • FIG. 3C is for the case of Example 3.
  • the change in phase formed according to temperature when the zinc content changes is shown.
  • the compound mainly formed in the aluminum alloy is the MgZn 2 phase.
  • the Al 3 Mg 2 phase, the Al 13 Cr 2 phase, and the T-(Mg 32 (Al, Zn) 49 ) phase are formed. According to thermodynamic calculations, as the zinc content increases, the fraction of the total compound formed in the aluminum alloy increases from 6.3 vol% to 7.5 vol%.
  • Table 2 shows the homogenization treatment conditions of an aluminum alloy manufactured according to a method for manufacturing a high-strength aluminum-zinc-magnesium-copper alloy thick plate according to one embodiment of the present invention.
  • FIG. 4 is an optical microscope photograph showing the microstructure of an aluminum alloy casting manufactured according to a method for manufacturing a high-strength aluminum-zinc-magnesium-copper alloy thick plate according to an embodiment of the present invention.
  • the aluminum alloy casting material had a grain size of about 150 ⁇ m or less and a microstructure with an average grain size in the range of 50 ⁇ m to 80 ⁇ m.
  • the aluminum alloy casting material had a compound fraction of about 3.4 vol% (vol%) in the range of 3.2 vol% to 3.6 vol%.
  • partial melting may occur at a high temperature. It is desirable to prevent such partial melting and minimize the fraction of compounds formed by precipitation or crystallization. Since such partial melting is an endothermic reaction, a peak appears in a differential scanning calorimetry (DSC) graph, and thus the homogenization temperature that prevents partial melting can be determined.
  • DSC differential scanning calorimetry
  • FIGS. 5a and 5b are differential scanning calorimetry graphs of an aluminum alloy manufactured according to a method for manufacturing a high-strength aluminum-zinc-magnesium-copper alloy thick plate according to one embodiment of the present invention.
  • the starting temperature of the peak indicating partial melting was about 477.7°C
  • the peak temperature was about 481.2°C
  • the ending temperature was about 491.0°C.
  • the internal temperature deviation of the homogenization treatment furnace is about 15°C. Accordingly, since the first homogenization treatment should be controlled to be below the starting temperature at which the peak starts due to partial melting, about 460°C is analyzed as the preferable temperature.
  • the aluminum alloy casting material was subjected to primary homogenization at 460°C for 12 hours to produce the aluminum alloy primary homogenized material.
  • the starting temperature of the peak indicating partial melting was about 492.8°C
  • the peak temperature was about 499.6°C
  • the ending temperature was about 503.2°C.
  • the internal temperature deviation of the homogenization treatment furnace is about 15°C. Accordingly, since the secondary homogenization treatment should be controlled to be below the starting temperature at which the peak starts due to partial melting, about 475°C is analyzed as the preferable temperature.
  • the aluminum alloy primary homogenizer was subjected to secondary homogenization at 475°C for 2 hours to produce an aluminum alloy secondary homogenizer.
  • the reason why the peak start temperature of the aluminum alloy primary homogenization material is higher than that of the aluminum alloy casting material is that some of the compounds that cause partial melting are dissolved into the aluminum matrix through the primary homogenization treatment, so the content of the compounds is lowered, which is analyzed to be the reason why the start temperature at which partial melting occurs increases.
  • Example 1 The above aluminum alloy secondary homogenizer corresponds to Example 1, and a two-stage multi-homogenization treatment was performed.
  • Examples 2 and 3 differ from Example 1 only in alloy composition, and the homogenization treatment was manufactured by a multi-stage homogenization treatment at the same temperature and time.
  • FIGS. 6 and 7 are optical microscope photographs showing changes in the microstructure according to the homogenization time of an aluminum alloy manufactured according to a method for manufacturing a high-strength aluminum-zinc-magnesium-copper alloy thick plate according to an embodiment of the present invention.
  • the microstructure of the aluminum alloy casting material subjected to the first homogenization treatment at 460°C for 6 to 48 hours is shown.
  • the aluminum alloy casting material had a compound fraction of about 3.4 vol% immediately after casting.
  • the compound fraction continued to decrease until 36 hours, whereas the compound fraction increased again at 48 hours.
  • the compound existing at the grain boundary indicated by the white arrow was found when the aluminum alloy casting material was homogenized for 6 hours, but was not found when the homogenization treatment was performed for 12 hours or longer. Therefore, as a result of optimization considering the minimization of the compound fraction and the minimization of the homogenization treatment time, it is preferable to perform the first homogenization treatment at 460°C for 12 hours.
  • the aluminum alloy primary homogenizer is a case where the primary homogenization treatment was performed at 460°C for 12 hours as shown in Fig. 6, and the compound fraction was found to be 1.18 volume%.
  • FIG. 7 the microstructure of the aluminum alloy primary homogenization material that was subjected to secondary homogenization treatment for varying times from 1 hour to 24 hours at 475°C is shown.
  • the secondary homogenization treatment time of the aluminum alloy cast material increased, the compound fraction continued to decrease for up to 24 hours.
  • the secondary homogenization treatment time for which the compound fraction is lowered to 1% by volume or less is 2 hours or longer. Therefore, as a result of optimization considering the minimization of the compound fraction and the minimization of the homogenization treatment time, it is preferable to perform the secondary homogenization treatment at 475°C for 2 hours.
  • the compound fraction was 3.42 vol% in the above aluminum alloy cast material, and the compound fraction was reduced to 1.18 vol% in the above aluminum alloy primary homogenized material that was subjected to the first homogenization treatment at 460°C for 12 hours, and the compound fraction was reduced to 0.84 vol% in the above aluminum alloy primary homogenized material that was subjected to the second homogenization treatment at 475°C for 2 hours. Therefore, according to the present invention, the compound (secondary phase) fraction can be achieved to less than 1 vol% in a short period of time.
  • FIGS. 8A and 8B are graphs showing the compound fraction according to the homogenization time of an aluminum alloy manufactured by a method for manufacturing a high-strength aluminum-zinc-magnesium-copper alloy thick plate according to an embodiment of the present invention.
  • FIG. 8A shows a case where the aluminum alloy cast material was first homogenized at 460°C
  • FIG. 8B shows a case where the aluminum alloy first homogenized material was secondarily homogenized at 475°C.
  • the results of optimization considering minimizing the compound fraction and minimizing the homogenization treatment time are that the first homogenization treatment was performed at 460°C for 12 hours, and the second homogenization treatment was performed at 475°C for 2 hours. This is consistent with the results described above with reference to FIGS. 6 and 7.
  • FIGS. 9A and 9B are graphs showing the hardness according to the homogenization time of an aluminum alloy manufactured by a method for manufacturing a high-strength aluminum-zinc-magnesium-copper alloy thick plate according to an embodiment of the present invention.
  • FIG. 9A shows a case where the aluminum alloy cast material was first homogenized at 460°C
  • FIG. 9B shows a case where the aluminum alloy first homogenized material was secondarily homogenized at 475°C.
  • Table 3 is a table showing the hardness according to the homogenization time of an aluminum alloy manufactured by a method for manufacturing a high-strength aluminum-zinc-magnesium-copper alloy thick plate according to an embodiment of the present invention.
  • the aluminum alloy homogenized material subjected to the secondary homogenization treatment was reheated to various temperatures and then hot-rolled using a hot rolling roll at room temperature to produce an aluminum alloy thick plate having a thickness of about 25 mm.
  • the hot rolling condition settings will be described in detail.
  • FIG. 10 is a photograph showing the results of hot rolling according to the reheating temperature of an aluminum alloy manufactured by a method for manufacturing a high-strength aluminum-zinc-magnesium-copper alloy thick plate according to an embodiment of the present invention.
  • the hot rolling result of the aluminum alloy secondary homogenizer of Example 1 is shown.
  • the hot rolling was performed using a hot rolling roll at room temperature.
  • the hot rolling of the aluminum alloy secondary homogenizer was successfully performed.
  • the reheating temperature was 460°C, the aluminum alloy secondary homogenizer was destroyed, making hot rolling impossible.
  • the reheating temperature is 460°C
  • the reheating temperature is reduced to 460°C or lower, the temperature difference between the aluminum alloy secondary homogenizer and the hot rolling roll is reduced, thereby reducing the effect of the thermal shock and enabling hot rolling.
  • Table 4 is a table showing the hot rolling results according to the reheating temperature of an aluminum alloy manufactured by a method for manufacturing a high-strength aluminum-zinc-magnesium-copper alloy thick plate according to one embodiment of the present invention.
  • the hot-rolled aluminum alloy thick plates of Examples 1 to 3 were heated and subjected to a solution treatment at 470°C for 1 hour, cooled with water, and then heated again and aged at 120°C for 12 hours, i.e., the Examples were subjected to a T6 heat treatment.
  • the following mechanical properties were measured and microstructures were observed for the aluminum alloy thick plates that had been subjected to a solution treatment and an aging treatment.
  • FIGS. 11A, 11B, and 11C are scanning electron microscope photographs showing cross-sections of aluminum alloy plates manufactured by a method for manufacturing high-strength aluminum-zinc-magnesium-copper alloy plates according to one embodiment of the present invention.
  • FIG. 11A is for Example 1
  • FIG. 11B is for Example 2
  • FIG. 11C is for Example 3.
  • “RD” represents a rolling direction
  • “ND” represents a direction perpendicular to the rolling direction, i.e., a thickness direction.
  • the examples showed similar microstructures and did not show distinct trends in the change in zinc content.
  • the average grain size of the examples was in the range of 46.8 ⁇ m to 49.1 ⁇ m
  • the kernel average misorientation (KAM) was in the range of 1.14 to 1.21
  • the recrystallized fraction was in the range of 63 to 66 volume%.
  • the recrystallized fraction was defined to include crystals having a GOS (grain orientation spread) value of 0 to 2 degrees in EBSD (Electron Backscatter Diffraction) analysis.
  • FIG. 12 is a graph showing the strength and elongation of an aluminum alloy plate manufactured by a method for manufacturing a high-strength aluminum-zinc-magnesium-copper alloy plate according to an embodiment of the present invention.
  • Table 5 is a table showing the strength and elongation of an aluminum alloy plate manufactured by a method for manufacturing a high-strength aluminum-zinc-magnesium-copper alloy plate according to one embodiment of the present invention.
  • Example 1 500 ⁇ 8.5 571 ⁇ 2.7 14.2 ⁇ 0.6
  • Example 2 545 ⁇ 3.8 608 ⁇ 3.5 13.3 ⁇ 0.5
  • Example 3 591 ⁇ 4.0 653 ⁇ 2.0 13.1 ⁇ 0.6
  • the examples showed similar behavior in strength-elongation curves. As the zinc content of the examples increased, the yield strength and tensile strength increased, and the elongation tended to decrease.
  • FIG. 13 is a graph showing fatigue characteristics of an aluminum alloy thick plate manufactured by a method for manufacturing a high-strength aluminum-zinc-magnesium-copper alloy thick plate according to an embodiment of the present invention.
  • the fatigue experiment was performed at an R ratio of 0.1, a fatigue cycle frequency of 30 Hz, and room temperature (25°C).
  • the fatigue stress was defined as the stress obtained at 10 7 cycles.
  • the time required for 10 4 cycles was 0.09 hours
  • the time required for 10 5 cycles was 0.93 hours
  • the time required for 10 6 cycles was 9.26 hours
  • the time required for 10 7 cycles was 92.59 hours.
  • Example 1 The fatigue stress tended to increase as the zinc content increased.
  • FIG. 14 is a graph showing the fracture toughness of an aluminum alloy plate manufactured by a method for manufacturing a high-strength aluminum-zinc-magnesium-copper alloy plate according to an embodiment of the present invention.

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  • Crystallography & Structural Chemistry (AREA)
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Abstract

La présente invention concerne : une plaque épaisse d'alliage d'aluminium-zinc-magnésium-cuivre à haute résistance qui peut être laminée à chaud à l'aide de cylindres de laminage à chaud à température ambiante et dans laquelle les propriétés mécaniques sont améliorées par la prévention de défauts consistant en une réduction de la fraction de phases secondaires ; et un procédé de production associé. Selon un mode de réalisation de la présente invention, un procédé de production d'une plaque épaisse d'alliage aluminium-zinc-magnésium-cuivre à haute résistance comprend : une étape de coulage servant à former un matériau coulé en alliage d'aluminium et consistant à couler un métal fondu formé par fusion d'éléments d'alliage correspondant à un alliage d'aluminium contenant de 5 à 8% en poids de zinc (Zn), de 2 à 3% en poids de magnésium (Mg) et de 1 à 2% en poids de cuivre (Cu), le reste comprenant de l'aluminium (Al) et des impuretés inévitables ; une étape de traitement d'homogénéisation en plusieurs étapes servant à soumettre le matériau coulé en alliage d'aluminium à un traitement d'homogénéisation en plusieurs étapes pour former un matériau homogénéisé en alliage d'aluminium ; une étape de réchauffage servant à chauffer le matériau homogénéisé en alliage d'aluminium à une température dans la plage de 300 à 400°C ; et une étape de laminage à chaud servant à laminer à chaud le matériau homogénéisé en alliage d'aluminium réchauffé pour former une plaque épaisse en alliage d'aluminium.
PCT/KR2024/005456 2023-04-24 2024-04-23 Plaque épaisse d'alliage d'aluminium-zinc-magnésium-cuivre à haute résistance et son procédé de production Pending WO2024225720A1 (fr)

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KR102566987B1 (ko) * 2023-04-24 2023-08-14 한국재료연구원 고강도 알루미늄-아연-마그네슘-구리 합금 후판 및 그 제조방법

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JP2008516079A (ja) * 2004-10-05 2008-05-15 アレリス、アルミナム、コブレンツ、ゲゼルシャフト、ミット、ベシュレンクテル、ハフツング 高強度、高靱性Ａｌ−Ｚｎ合金製品およびそのような製品の製造方法
KR20150047246A (ko) * 2013-10-24 2015-05-04 한국기계연구원 결정립이 미세화된 알루미늄-아연-마그네슘-구리 합금 판재의 제조방법
KR20170132116A (ko) * 2017-11-21 2017-12-01 한국기계연구원 소부경화성이 우수한 고강도 알루미늄 합금 판재 및 이의 제조방법
KR20210032429A (ko) * 2018-07-17 2021-03-24 콩스텔리움 뇌프-브리작 성형 및 조립에 적합한 7xxx 알루미늄 합금 박판 시트 제조 방법
KR102566987B1 (ko) * 2023-04-24 2023-08-14 한국재료연구원 고강도 알루미늄-아연-마그네슘-구리 합금 후판 및 그 제조방법

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JPS5690949A (en) * 1979-12-21 1981-07-23 Sumitomo Light Metal Ind Ltd Material for airplane stringer with fine crystal grain and its manufacture
JP2008516079A (ja) * 2004-10-05 2008-05-15 アレリス、アルミナム、コブレンツ、ゲゼルシャフト、ミット、ベシュレンクテル、ハフツング 高強度、高靱性Ａｌ−Ｚｎ合金製品およびそのような製品の製造方法
KR20150047246A (ko) * 2013-10-24 2015-05-04 한국기계연구원 결정립이 미세화된 알루미늄-아연-마그네슘-구리 합금 판재의 제조방법
KR20170132116A (ko) * 2017-11-21 2017-12-01 한국기계연구원 소부경화성이 우수한 고강도 알루미늄 합금 판재 및 이의 제조방법
KR20210032429A (ko) * 2018-07-17 2021-03-24 콩스텔리움 뇌프-브리작 성형 및 조립에 적합한 7xxx 알루미늄 합금 박판 시트 제조 방법
KR102566987B1 (ko) * 2023-04-24 2023-08-14 한국재료연구원 고강도 알루미늄-아연-마그네슘-구리 합금 후판 및 그 제조방법

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