KR20090127185A - Alloy composition and preparation thereof - Google Patents

Abstract

The disclosure relates to a high strength Aluminum-Zinc-Magnesium-Copper-Zirconium alloy semi-products of composition Al-Zn(8-12.5)wt%-Mg (1.2-2.0)wt%-Cu(1.4-2.2)wt%-Zr(0.10-0.18)wt% and its method of preparation. The alloy semi-product could be further processed into high strength alloy extrusions or high strength alloy thin sheets.

Description

Alloy composition and its manufacturing method {ALLOY COMPOSITION AND PREPARATION THEREOF}

High strength aluminum-zinc-magnesium having a composition of Al- (8-12.5) wt% Zn- (1.2-2.0) wt% Mg- (1.4-2.2) wt% Cu- (0.10-0.18) wt% -Zr It provides a copper-zirconium alloy composition. The present invention also provides a method for producing an alloy semifinished product which is further processed into high strength alloy extrudates or alloy sheets.

Aluminum-zinc-magnesium-copper-zirconium (Al-Zn-Mg-Cu-Zr) alloys are highly demanded for critical applications of varying strength in the aerospace and defense industries. Such alloys are typically processed in the form of sheets, plates, extrusions, forgings, etc. for various structural applications. When applied to aerospace, one of the application requirements is to process these alloys in the form of sheets of less than 0.3 mm in thickness, in which case the Al alloys are used in combination with fibers (preferably glass fibers). This results in the formation of fiber-metal laminated (FML) composites. The strength properties of Al alloy thin plates used in FML composites play an important role in determining the tensile yield strength of FML composites (Ad Viot and J.W.Gannnink, Gibre Metal laminates: An Introduction, Kluwer Academic Publishers, The Netherlands, 2001). In addition, Al alloys having a thickness of less than 0.3 mm are preferred for this purpose because they improve drapeability.

U.S. Patents 4,477,292 and 4,832,758 disclose aluminum-zinc-magnesium-copper-zirconium (Al-Zn-Mg-Cu-Zr) alloys as high-strength aluminum alloys that can be produced through ingot metallurgy. The improved strength properties of this class of alloys improve certain properties (in terms of density versus strength and Young's modulus, etc.) and therefore can significantly reduce weight, and the focus of developing such alloys is to focus on various metallurgical processes. Through improving the strength.

U.S. Patent Nos. 4,699,673 and 4,988,394, and U.S. Patent Application 20060191609, disclose methods for making thin sheets of Al-Zn-Mg-Cu-Zr alloys having a thickness of 1.2 mm or less. However, these patent documents do not disclose any information on the manufacturing method of the high strength Al-Zn-Mg-Cu-Zr sheet having a thickness of 0.3 mm or less. A problem associated with maintaining high strength in these products is that recrystallization occurs, resulting in more significant cracking as the sheet is progressively thinner. However, due to the non-disclosure of the details of such thin sheet processing, there is no information on this subject in this document.

One of the Al-Zn-Mg-Cu-Zr alloys known in the art, namely AA 7055 (Aluminium Company of America (ALCOA) technical data is available at www.millproducts-alcoa.com) is Al- (7.6- 8.4) wt% Zn- (l.8-2.3) wt% Mg- (2-2.6) wt% Cu- (0.08-0.25) wt% Zr. Typical tensile properties for extrusion of the 7055 T7751 in the longitudinal direction (ie along the extrusion direction) are as follows: 0.2% proof stress = 655 MPa, UTS = 669 MPa, elongation = 11%. T77 tempers have strength characteristics corresponding to peak aged T6 tempers, but have similar stress corrosion cracking resistance as T76 tempers (ALCOA publication.Light Metal Age, October, 1991, p. 14).

U.S. Patent Application 20040099352 discloses another high strength Al-Zn-Mg-Cu-Zr alloy as 8.2-10% Zn, 1.95-2.5% Cu, 1.9-2.5% Mg, 0.05-0.25% Zr (unit: wt%). An alloy containing is disclosed. When produced by the extrusion process and maximum age, the alloy has a 0.2% yield strength of 703 MPa. Another Al-Zn-Mg-Cu-Zr-based high-strength alloy containing scandium and processed by extrusion and heat treatment to produce the maximum aged T6 temper is Al- 8.6 Zn- 2.6 Mg- 2.4 Cu-0.2 wt% It has a composition of Sc and an unknown amount of Zr [Metall. Mater. Trans. A, 30A, 1017, 1999]. Typical tensile properties of this material are as follows: 0.2% PS = 689 MPa, UTS = 715 MPa, elongation = 11.8%. However, recent studies have shown that Al-Zn-Mg-Cu-Zr alloys with a Zn content of less than 8.5% and Mg and Cu contents of less than 2% by weight, respectively, have a similar 0.2% PS or higher at maximum age temper. It shows that 0.2% PS can be achieved (Minerals & Metals Review, 10, 2005, p. 65), which adds Sc to achieve about 700 MPa of 0.2% PS in the maximum aged extrudates of these alloys. It is also not necessary and also means that the Zn content should not exceed 8.5%.

U.S. Patent Application 20050056353 discloses another high strength Al-Zn-Mg-Cu-Zr-Sc alloy, 8.5-11% Zn, 1.8-2.4% Mg, 1.8-2.6% Cu, 0.05-0.30% Sc and Zr, V And 0.5 wt% or less of at least one element of the group consisting of Hf is disclosed. This alloy, when produced by the extrusion process and the maximum age, has a 0.2% yield strength of 670 to 715 MPa. U.S. Patent Application 20050072497 discloses another high strength Al-Zn-Mg-Cu-Zr alloy, 8.3-14% Zn, 0.3-2% Cu, 0.5-4.5% Mg, 0.03-0.15% Zr in weight percent And 0.02-0.7 wt% of at least one element from the group consisting of Sc, Hf, La, Ce, Nd is disclosed. This alloy, when produced by the extrusion process and the maximum age, has a 0.2% yield strength of 670-783 MPa.

The main disadvantage of Sc-containing alloys is that they are expensive. Another limitation of the aforementioned alloys is that scandium mines are not available in many countries, including India. Recent studies have shown that the presence of Sc in Al-Zn-Mg-Cu-Zr alloys reduces fatigue properties (Scripta Materialia, Vol. 52, p. 645, 2005).

Therefore, very high strength aluminum-zinc-magnesium with various applications, especially in the defense industry where a wide range of extrudates are used for various applications, such as aerospace applications where sheet thicknesses of less than 0.3 mm are required. There is a need for continued development for -copper-zirconium (Al-Zn-Mg-Cu-Zr) alloys.

Summary of the Invention

The invention relates to aluminum-zinc-magnesium-copper having a composition of Al- (8-12.5) wt% Zn- (1.2-2.0) wt% Mg- (1.4-2.2) wt% Cu- (0.10-0.18) wt% Zr It provides a zirconium alloy and a method of manufacturing the same. The present invention also provides a method for producing an alloy semifinished product which is further processed into high strength alloy extrudates or alloy sheets.

In one aspect, the invention provides Al- (11.5-12.5) wt% Zn- (1.3-2.0) wt% Mg- (1.5-2.2) wt% Cu- (0.12-0.18) wt% Zr- Zinc-magnesium-copper-zirconium alloy (Al-Zn-Mg-Cu-Zr) alloy extrudates are provided.

In another aspect, the invention provides Al- (8-10) wt% Zn- (1.2-2.0) wt% Mg- (1.4-2.2) wt% Cu- (0.12-0.18) wt% Zr- A zinc-magnesium-copper-zirconium alloy (Al-Zn-Mg-Cu-Zr) alloy sheet is provided.

In one aspect, the present invention is to enable the alloy to maintain the increased solute supersaturation in the subsequent heat treatment and machining process by effective dissolution of the solid solution product, while at the same time to obtain high strength during aging treatment, Provided is a method for producing an Al-Zn-Mg-Cu-Zr alloy using a two-step homogenization process.

In another aspect, the present invention utilizes an alloy composition and extrusion process parameters that are optimized to achieve high strength of the alloy by inevitably maintaining a grain boundary structure that is not recrystallized and imparting a solutionzing effect in the extrusion process. To provide an Al-Zn-Mg-Cu-Zr alloy extrudate.

In another aspect, the invention provides an optimized alloy composition, homogenization treatment, in order to enable the alloy to achieve high strength and minimize the extent of edge cracking by maintaining grain boundaries that are not necessarily recrystallized in most of the sheet. Provided is a method for producing an Al—Zn—Mg—Cu—Zr alloy thin plate using rolling parameters and an intermediate annealing treatment.

In yet another aspect, the present invention provides a method of making an Al-Zn-Mg-Cu-Zr alloy using two-step artificial aging so that the alloy can achieve reproducible strength properties.

In another aspect, the present invention provides a method of making an Al-Zn-Mg-Cu-Zr alloy sheet having very large strength and less than 0.3 mm in thickness.

Detailed description of the invention

The present invention provides an aluminum-zinc-magnesium-copper-zirconium (Al-Zn-Mg-Cu-Zr) alloy having the following composition in weight percent:

Zn 8-12.5;

Mg 1.2-2.0;

Cu 1.4-2.2; And

Zr 0.10-0.18.

The present invention provides an aluminum-zinc-magnesium-copper-zirconium (Al-Zn-Mg-Cu-Zr) alloy semifinished product having the following composition in weight percent:

Zn 8-12.5;

Mg 1.2-2.0;

Cu 1.4-2.2; And

Zr 0.10-0.18.

In one aspect, the present invention provides an aluminum-zinc-magnesium-copper-zirconium (Al-Zn-Mg-Cu-Zr) alloy extrudate having the following composition in weight percent:

Zn 11.5-12.5;

Mg 1.3-2.0;

Cu 1.5-2.2; And

Zr 0.12-0.18.

In another aspect, the present invention provides an aluminum-zinc-magnesium-copper-zirconium (Al-Zn-Mg-Cu-Zr) alloy sheet having the following composition in weight percent:

Zn 8-10;

Mg 1.2-2.0;

Cu 1.4-2.2; And

Zr 0.12-0.18.

In another aspect, the present invention provides an aluminum having a composition of Al- (8-12.5) wt% Zn- (1.2-2.0) wt% Mg- (1.4-2.2) wt% Cu- (0.10-0.18) wt% Zr Provides a method for producing a zinc-magnesium-copper-zirconium (Al-Zn-Mg-Cu-Zr) alloy semifinished product. This method includes the following steps:

a. Melting a charge mixture of primary aluminum and an Al-33wt% Cu master alloy;

b. Adding pure zinc element after raising the temperature of the molten charge;

c. Superheating the molten charge and adding Al-50wt% Mg master alloy and Mg-28wt% Zr master alloy;

d. Adding grain refinement nuclei pellets at reduced temperature;

e. Adding degassing pellets;

f. Pouring molten metal into a preheated metal mold under argon atmosphere; And

g. Solidifying to obtain a cast alloy billet or slab.

In one aspect, the present invention provides a method for producing an aluminum-zinc-magnesium-copper-zirconium (Al-Zn-Mg-Cu-Zr) alloy semifinished product, the primary aluminum having a purity of 99.80% or more.

In another aspect, the present invention provides a method for melting a charge mixture comprising 76.38-84.81 wt% primary aluminum and 4.54-6.97 wt% master alloy at an induction furnace by melting at a temperature of 720-730 ° C. It provides a method for producing a semi-aluminum-zinc-magnesium-copper-zirconium (Al-Zn-Mg-Cu-Zr) alloy comprising a.

In another aspect, the present invention provides a method for preparing an Al-Zn-Mg-Cu-Zr alloy semifinished product, which adds 8.15-12.65 wt% of pure elemental Zn to the melt and the temperature is increased to 735-745 ° C. Raise and then add 2.04-3.32 wt% Al-50 wt% Mg master alloy and 0.46-0.68 wt% Mg-28 wt% Zr master alloy and superheat the molten alloy at 755-765 ° C. for 10-15 minutes. It involves doing.

In another aspect, the present invention provides a method for preparing a semi-finished Al-Zn-Mg-Cu-Zr alloy, which lowers the temperature of the superheated molten alloy to 735-740 ° C. and 0.01 for grain refinement. Adding -0.1 kg of nuclear pellets. The nuclear pellet is dipotassium titanium hexafluoride (K ₂ TiF ₆ ) or potassium tetrafluoroborate (KBF ₄ ).

In another aspect, the present invention provides a method for preparing an Al-Zn-Mg-Cu-Zr alloy semifinished product, the method comprising degassing a dissolved gas such as hydrogen and removing it from the molten metal, which degassing is 0.01 It is carried out using degassing pellets such as -0.5 kg of hexachloroethane (C ₂ Cl ₆ ).

In another aspect, the present invention provides a process for the preparation of an Al-Zn-Mg-Cu-Zr alloy semifinished product, wherein the process is characterized by quenching the molten metal under an argon atmosphere at a lowered temperature of 710-720 ° C, between Pouring into an appropriately sized metal mold preheated to temperature.

In another aspect, the present invention provides a method for producing an Al-Zn-Mg-Cu-Zr alloy semifinished product, which comprises solidifying a melt to obtain a cast alloy billet or slab.

As used herein, the term alloy semifinished product refers to a cast alloy billet or slab.

In one aspect, the invention provides a method of making a high strength Al-Zn-Mg-Cu-Zr alloy extrudate, the method comprising the following steps:

a. Homogenizing, scalping and extruding the cast alloy billet; And

b. Solution-quenching and quenching, followed by stretching the alloy extrudate to achieve a permanent set of 1-1.5% followed by artificial aging to obtain the maximum aged high strength alloy extrudate.

In another aspect, the invention provides Al- (11.5-12.5) wt% Zn- (1.3-2.0) wt% Mg- (1.5-2.2) wt% Cu- (0.12-0.18) wt% Provided is a method for preparing a Zn-Mg-Cu-Zr alloy extrudate, the method comprising the following steps:

a. Melting a charging mixture of primary aluminum and Al-33wt% Cu master alloy;

b. Adding pure zinc element after raising the temperature of the molten charge;

c. Superheating the molten charge and adding Al-50wt% Mg master alloy and Mg-28wt% Zr master alloy;

d. Adding grain refinement nuclei pellets at reduced temperature;

e. Adding degassing pellets;

f. Pouring molten metal into a preheated metal mold under argon atmosphere;

g. Solidifying to obtain a cast alloy billet or slab.

h. Homogenizing, scalping and extruding the cast alloy billet;

i. Treating with the solution and quenching and stretching the alloy extrudate to achieve a permanent strain of 1-1.5%; And

j. Artificial aging to obtain the maximum aged high strength alloy extrudates.

In another aspect, the present invention provides a method for producing a high strength Al-Zn-Mg-Cu-Zr alloy extrudate, in which the homogenization treatment is carried out in two steps. The first step is carried out 25-35 hours at 440-450 ℃, the second step is carried out 20-30 hours at 450-460 ℃ and then cooled in air. Homogenization treatment eliminates dendritic segregation of the cast microstructure and enables more effective dissolution of the solidified product, thereby increasing the alloying solute in subsequent heat treatment and machining processes to obtain high strength during aging. It helps to maintain supersaturation.

Scalping treatment on the homogenized billet removes the oxide layer formed on the surface. Casting defects are detected by nondestructive testing on scalped billets.

In another aspect, the present invention provides a method for preparing a high strength Al-Zn-Mg-Cu-Zr alloy extrudate, wherein the solution treatment is performed at 450-460 ° C. for 1-2 hours and then water cooled at room temperature. quenching). The extrudate is then stretched for stress relief to achieve 1-1.5% permanent strain.

In yet another aspect, the present invention provides a method of making a high strength Al-Zn-Mg-Cu-Zr alloy extrudates, wherein the process comprises 6- at 90-100 ° C. in a first step for the stretched alloy extrudates. Aging is carried out for 8 hours and in a second step, artificial aging is carried out at 120-125 ° C. for 20-25 hours. By this treatment it is possible to obtain maximum strength in the alloy extrudate in a reproducible manner.

In another aspect, the present invention provides a method for producing a high strength Al-Zn-Mg-Cu-Zr alloy extrudate, which inevitably maintains the grain boundary structure that is not recrystallized and has a solution treatment effect in the extrusion process. By using the alloy composition and extrusion process parameters optimized to achieve high strength of the alloy.

In another aspect, the present invention provides a method of making a high strength Al-Zn-Mg-Cu-Zr alloy extrudates having a 0.2% tensile P.S. of at least 750 MPa.

In one aspect, the present invention provides a method for producing a high strength Al-Zn-Mg-Cu-Zr alloy sheet, the method comprising the following steps:

a. Homogenizing the cast alloy slab, scalping and hot rolling to form a sheet, and then cold rolling the sheet with intermediate annealing to obtain an alloy sheet of the required thickness; And

b. Treating with the solution and quenching, followed by artificial aging to obtain the maximum aged high strength alloy sheet.

In another aspect, the invention provides Al- (8-10) wt% Zn- (1.2-2.0) wt% mg- (1.4-2.2) wt% Cu- (0.12-0.18) wt% Zr Provided is a method for preparing a -Zn-Mg-Cu-Zr alloy sheet, the method comprising the following steps:

a. Melting a charging mixture of primary aluminum and Al-33wt% Cu master alloy;

b. Adding pure zinc element after raising the temperature of the molten charge;

c. Superheating the molten charge and adding Al-50wt% Mg master alloy and Mg-28wt% Zr master alloy;

d. Adding grain refinement nuclei pellets at reduced temperature;

e. Adding degassing pellets;

f. Pouring molten metal into a preheated metal mold under argon atmosphere;

g. Solidifying to obtain a cast alloy slab.

h. Homogenizing, scalping and hot rolling the cast alloy slab into a sheet, and then cold rolling the sheet with intermediate annealing to obtain an alloy sheet of the required thickness;

i. Treating with the solution and quenching; And

j. Artificial aging to obtain a maximum aged high strength alloy sheet.

In another aspect, the present invention provides a method for producing a high strength Al-Zn-Mg-Cu-Zr alloy sheet, in which the homogeneous treatment of the cast alloy slab is performed, the first step being 25- at 445-455 ° C. 35 hours, the second step is 10-20 hours at 455-465 ℃ and then cooled in air. The homogenization treatment removes segregation of dendrites in the cast structure. Scalping on the homogenized slab removes the oxide layer formed on the surface. Scalping slabs are subjected to non-destructive testing to detect casting defects.

In another aspect, the present invention provides a method of making a high strength Al-Zn-Mg-Cu-Zr alloy sheet, in which the method is 425-435 ° C. for a scalped slab (with an initial thickness of 100 mm). Hot rolling at a linear velocity of 20 m / min at an initial billet temperature in the range yields a plate about 22 mm thick. These plates are cross-rolled using the same initial billet temperature and rolling speed to finally produce a sheet about 5 mm thick. During the hot rolling process, the thickness of the billet is reduced by 4-8% by three passes and intermediate annealed at 415-435 ° C. for 15-25 minutes. This cycle continues until a 22 mm thick target plate is followed by a 5 mm thick sheet. The intermediate annealing treatment is carried out for the purpose of stress relief.

In another aspect, the present invention provides a method for producing a high strength Al-Zn-Mg-Cu-Zr alloy sheet, wherein the method is subjected to cold rolling at room temperature over a plurality of steps on a hot rolled sheet. Each step involves reducing the thickness by 15-25% by three passes, intermediate annealing at 415-425 ° C. for 15-25 minutes and then cooling in air. The intermediate annealing treatment is carried out for the purpose of stress relief. The cold rolling process and subsequent intermediate annealing process are repeated until the sheet thickness is reduced to 0.28 mm, i.e. less than 0.3 mm.

In another aspect, the present invention provides a method for producing a high strength Al-Zn-Mg-Cu-Zr alloy sheet, wherein the solution treatment for the rolled sheet is carried out at 450-560 ° C. for 1-1.5 hours. And water cooled at room temperature.

In another aspect, the present invention provides a method for producing a high-strength Al-Zn-Mg-Cu-Zr alloy sheet, aged in 90-100 ℃ in the first step for 6-8 hours, in the second step A two-step artificial aging treatment is performed, aged at 115-125 ° C. for 20-30 hours. By this treatment, maximum strength can be obtained in the alloy.

In another aspect, the present invention provides a high strength Al-Zn-Mg-Cu-Zr alloy in the form of a sheet with reproducible high strength properties, i.e., 0.2% tensile PS of at least 623 MPa at maximum aging temper and a thickness of less than 0.3 mm. It provides a method of manufacturing.

The foregoing and other features and advantages of the invention will be better understood from the following detailed description, claims and drawings.

1 is an optical micrograph showing a grain boundary structure partially recrystallized in the maximum aged extrudate.

 FIG. 2 is an optical micrograph showing the grain boundary structure not recrystallized in the 0.28 mm thick maximum aged alloy sheet of the present invention.

 3 is a transmission electron micrograph showing the subgrain structure present in the non-recrystallized portion of the maximum aged alloy extrudates of the present invention.

4 is a transmission electron micrograph showing a uniform and precise distribution of the reinforcing η 'precipitate in the maximum aged alloy extrudates of the present invention.

5 is a transmission electron micrograph showing a uniform and precise distribution of the reinforcing η 'precipitates in the 0.28 mm thick maximum aged alloy sheet of the present invention.

The foregoing and other aspects of the invention are described in more detail by the following examples, which are provided with the intention of illustrating the embodiments of the invention without intending to limit the scope thereof. .

Example 1: Preparation of Al-11.8wt% Zn-1.4wt% Mg-1.8wt% Cu-0.16wt% Zr

For the 15 kg alloy melt of the present invention, 11.98 kg of primary aluminum (purity 99.80 wt% Al and the remainder are 0.15 wt% Fe and 0.05 wt% Si impurities) and 0.864 kg Al-33 wt% Cu master alloy Charged into an induction furnace. The charge mixture was dissolved at 725 ° C. To this, 1.7 kg of pure Zn was added in ingot form. When the charge was dissolved, the temperature of the melt was raised to 740 ° C. and 0.364 kg of Al-50 wt% Mg master alloy and 0.092 kg of Mg-28 wt% Zr master alloy were added sequentially. The charge was superheated to 760 ° C. and held at this temperature for 10 minutes. The temperature was lowered back to 740 ° C. and 0.03 kg of nuclear pellets were added for grain refinement. After 5 minutes, 0.04 kg of degassing pellets were added for degassing. The molten alloy was poured into an appropriately sized metal mold preheated (to 150 ° C.) at 720 ° C. under argon atmosphere.

The melt was solidified and then the casting defect portion was removed from the ingot. A cylindrical casting billet of 95 mm diameter and 250 mm height was obtained. The billet was subjected to a two-step homogenization process, which included treatment at 445 ° C. for 24 hours, followed by 455 ° C. for 24 hours, followed by cooling in air. The billet was scalped and machined to produce a 74 mm diameter cylindrical billet and cut into two parts along its length. Extrusion was performed on the cylindrical billets having a diameter of 74 mm and a height of 125 mm. The extrusion process was performed on billets at an initial billet temperature of 420 ° C., an extrusion ram speed of 3 mm / sec and an extrusion rate of 20: 1. The extrudate was subjected to a solution treatment for 1.5 hours at 460 ° C., followed by water cooling at ambient temperature, a two step aging treatment comprising a first step of treating at 100 ° C. for 8 hours and a second step of treating at 120 ° C. for 24 hours. Carried out. This heat treatment achieves maximum strength in the alloy. Tensile ages were used to evaluate tensile properties (see Table 1).

Example 2: Preparation of Al-12.1wt% Zn-1.5wt% Mg-1.8wt% Cu-0.16wt% Zr

For the 15 kg alloy melt of the present invention, 11.85 kg of primary aluminum (purity 99.80 wt% Al and the remainder are 0.15 wt% Fe and 0.05 wt% Si impurities) and 0.86 kg Al-33 wt% Cu master alloy Charged into an induction furnace. The charge mixture was dissolved at 725 ° C. To this, 1.84 kg of pure Zn was added in ingot form. When the charge was dissolved, the temperature of the melt was raised to 740 ° C. and 0.36 kg of Al-50 wt% Mg master alloy and 0.09 kg of Mg-28 wt% Zr master alloy were added sequentially. The charge was superheated to 760 ° C. and held at this temperature for 10 minutes. The temperature was lowered back to 740 ° C. and 0.03 kg of nuclear pellets were added for grain refinement. After 5 minutes, 0.04 kg of degassing pellets were added for degassing. The molten alloy was poured into an appropriately sized metal mold preheated (to 150 ° C.) at 720 ° C. under argon atmosphere.

The melt was solidified and then the casting defect portion was removed from the ingot. A cylindrical casting billet of 95 mm diameter and 250 mm height was obtained. The billet was subjected to a two-step homogenization process, which included treatment at 445 ° C. for 24 hours, followed by 455 ° C. for 24 hours, followed by cooling in air. The billet was scalped and machined to produce a 74 mm diameter cylindrical billet and cut into two parts along its length. Extrusion was performed on the cylindrical billets having a diameter of 74 mm and a height of 125 mm. The extrusion process was performed on billets at an initial billet temperature of 420 ° C., an extrusion ram speed of 3 mm / sec and an extrusion rate of 20: 1. The extrudate was subjected to a solution treatment for 1.5 hours at 460 ° C., followed by water cooling at ambient temperature, a two step aging treatment comprising a first step of treating at 100 ° C. for 8 hours and a second step of treating at 120 ° C. for 24 hours. Carried out. This heat treatment achieves maximum strength in the alloy. Tensile ages were used to evaluate tensile properties (see Table 2).

Example 3: Preparation of Al-8.3wt% Zn-1.9wt% Mg-1.7wt% Cu-0.18wt% Zr

For the 50 kg alloy melt of the present invention, 41.154 kg of primary aluminum (purity 99.85 wt% Al and the remainder are 0.09 wt% Fe and 0.06 wt% Si impurities) and 2.72 kg Al-33 wt% Cu master alloy Charged into an induction furnace. The charge mixture was dissolved at 725 ° C. To this, 4.225 kg of pure Zn was added in ingot form. When the charge was dissolved, the temperature of the melt was raised to 740 ° C. and 1.562 kg of Al-50 wt% Mg master alloy and 0.339 kg of Mg-28 wt% Zr master alloy were added sequentially. The charge was superheated to 760 ° C. and held at this temperature for 10 minutes. The temperature was lowered back to 740 ° C. and 0.10 kg of nuclear pellets were added for grain refinement. After 5 minutes, 0.25 kg of degassing pellets were added for degassing. The molten alloy was poured into an appropriately sized metal mold preheated (to 150 ° C.) at 720 ° C. under argon atmosphere.

The melt was solidified and then the casting defect portion was removed from the ingot. A rectangular cast billet of 340 mm (length) x 300 mm (width) x 100 mm (thickness) was obtained. This billet was subjected to a two step homogenization annealing process comprising annealing at 450 ° C. for 25 hours, followed by 15 hours at 460 ° C. and then cooling in air. Scalping was performed on the uniformed billets to remove the oxide layer on the billet surface. The billet was hot rolled. Hot rolling was performed at an initial billet temperature of 425 ° C. and a linear velocity of 20 m / min. The thickness of the billet was reduced by 6% in three passes, followed by intermediate annealing for stress relief at 430 ° C. for 20 minutes for stress relief. This same hot rolling cycle was performed until the target plate thickness reached 22 mm. Subsequently cold rolling was performed to achieve a sheet thickness of 5 mm. Cold rolling was performed on the hot rolled sheet. Reduce the thickness by 20% in three passes, intermediate anneal at 420 ° C. for 15 minutes for stress relief, then perform the same cycle treatment on the sheet until a target thickness of 0.28 mm, i.e., less than 0.30 mm, is obtained. Carried out. The sheet was then solution treated at 460 ° C. for 1 hour and then water cooled at room temperature. Artificial aging was performed at 100 ° C. for 8 hours and then artificial aging at 120 ° C. for 24 hours. This heat treatment achieves maximum strength in the alloy. Tensile age was used to evaluate the tensile properties (see Table 3).

Example 4: Preparation of Al-9.5wt% Zn-1.6wt% Mg-2.0wt% Cu-0.17wt% Zr

For 50 kg of alloy melt of the present invention, 40.536 kg of primary aluminum (purity 99.85 wt% Al and the remainder are 0.09 wt% Fe and 0.06 wt% Si impurities) and 3.03 kg Al-33 wt% Cu master alloy Charged into an induction furnace. The charge mixture was dissolved at 725 ° C. To this, 4.825 kg of pure Zn in ingot form was added. When the charge was dissolved, the temperature of the melt was raised to 740 ° C. and 1.288 kg of Al-50 wt% Mg master alloy and 0.321 kg of Mg-28 wt% Zr master alloy were added sequentially. The charge was superheated to 760 ° C. and held at this temperature for 10 minutes. The temperature was lowered back to 740 ° C. and 0.10 kg of nuclear pellets were added for grain refinement. After 5 minutes, 0.25 kg of degassing pellets were added for degassing. The molten alloy was poured into an appropriately sized metal mold preheated (to 150 ° C.) at 720 ° C. under argon atmosphere.

The melt was solidified and then the casting defect portion was removed from the ingot. A rectangular cast billet of 340 mm (length) x 300 mm (width) x 100 mm (thickness) was obtained. This billet was subjected to a two step homogenization annealing process comprising annealing at 450 ° C. for 25 hours, followed by 15 hours at 460 ° C. and then cooling in air. Scalping was performed on the homogenized billet to remove the oxide layer on the billet surface. The billet was hot rolled. Hot rolling was performed at an initial billet temperature of 425 ° C. and a linear velocity of 20 m / min. The thickness of the billet was reduced by 6% in three passes, followed by intermediate annealing for stress relief at 430 ° C. for 20 minutes for stress relief. This same hot rolling cycle was performed until the target plate thickness reached 22 mm. Subsequently cold rolling was performed to achieve a sheet thickness of 5 mm. Cold rolling was performed on the hot rolled sheet. Reduce the thickness by 20% in three passes, intermediate anneal at 420 ° C. for 15 minutes for stress relief, then perform the same cycle treatment on the sheet until a target thickness of 0.28 mm, i.e., less than 0.30 mm, is obtained. Carried out. The sheet was then solution treated at 460 ° C. for 1 hour and then water cooled at room temperature. Artificial aging was performed at 100 ° C. for 8 hours and then artificial aging at 120 ° C. for 24 hours. This heat treatment achieves maximum strength in the alloy. Tensile age was used to evaluate the tensile properties (see Table 4).

Example 5: Evaluation of Alloy

Tensile properties were investigated for the alloys of Examples 1-4 of the present invention through a tensile test conducted at ambient temperature using a tensile specimen (25 mm gauge length). The alloys of Examples 1 and 2 were tested on round bar tensile specimens (25 mm gauge length) and the alloys of Examples 3 and 4 were tested on flat specimens. Tables 1 to 4 show the tensile test results for Examples 1 to 4, respectively.

The most noteworthy characteristic of the results was 0.2% P.S. The figures are quite high, ie 0.2% PS is greater than 755 MPa for the high strength alloys of Examples 1 and 2, and 0.2% PS is 623 MPa for the high strength thin alloys of Examples 3 and 4. . 1 shows a partially recrystallized grain boundary structure for the maximum aged alloy extrudates of the present invention. 0.2% P.S. Numerical data indicate that the grain boundary structure (see FIG. 2) not recrystallized in the maximum aged sheet (0.28 mm thickness) of the present invention and the subgrain boundary structure in the non-recrystallized grain boundary structure predominantly in the maximum aged alloy extrudates ( 3). It is also characterized by a uniform and fine distribution of reinforcing η precipitates in the maximum aged alloy extrudate (see FIG. 4) and the alloy sheet (see FIG. 5).

It will be appreciated that the alloys of the present invention are made using primary Al having a purity of 99.85 wt% or less. Therefore, it is understood that the ductility (ie% elongation) of the alloy will be significantly higher when prepared using higher purity, for example 99.9 wt% Al.

Table 1: Tensile Properties of the Maximum Aged Alloy Extruded in Example 1

Serial Number 0.2% PS (MPa) UTS (MPa) Elongation (%) One 755 765 6.1 2 768 782 5.4 3 758 772 5.8 4 762 779 5.7 5 769 779 6.2

Table 2: Tensile Properties of the Maximum Aged Alloy Extruded in Example 2

Serial Number 0.2% PS (MPa) UTS (MPa) Elongation (%) One 760 764 6.8 2 783 789 5.4 3 766 778 5.3 4 780 789 6.5 5 776 781 6.0

Table 3: Tensile Properties of 0.28 mm Thickness of Maximum Aged Alloy Sheets of Example 3

Serial Number 0.2% PS (MPa) UTS (MPa) Elongation (%) One 656 723 4.8 2 657 708 4.7 3 658 715 6.0 4 661 709 4.5 5 655 710 4.5 6 656 717 7.2 7 655 710 6.4 8 650 707 6.5 9 623 681 7.3 10 651 702 6.3

Table 4: Tensile properties of 0.28 mm thick maximum aged alloy sheet of Example 4

Serial Number 0.2% PS (MPa) UTS (MPa) Elongation (%) One 692 755 5.3 2 685 751 4.9 3 689 760 5.1 4 703 778 8.3 5 727 799 9.0 6 705 770 7.9 7 712 772 6.5 8 691 758 6.4 9 690 760 5.0 10 685 746 4.8

The Al-Zn-Mg-Cu-Zr alloy of the present invention has a high strength and can be used in various applications, for example, in the field of aerospace, where a thickness of less than 0.3 mm is required.

Claims (21)

An aluminum-zinc-magnesium-copper-zirconium (Al-Zn-Mg-Cu-Zr) alloy comprising the following composition in wt%: Zn 8-12.5; Mg 1.2-2.0; Cu 1.4-2.2; And Zr 0.10-0.18. An aluminum-zinc-magnesium-copper-zirconium (Al-Zn-Mg-Cu-Zr) alloy extrudate comprising the following composition in wt%: Zn 11.5-12.5; Mg 1.3-2.0; Cu 1.5-2.2; And Zr 0.12-0.18. Aluminium-zinc-magnesium-copper-zirconium (Al-Zn-Mg-Cu-Zr) alloy sheet comprising the following composition (wt% units): Zn 8-10; Mg 1.2-2.0; Cu 1.4-2.2; And Zr 0.12-0.18. A process for preparing an aluminum-zinc-magnesium-copper-zirconium (Al-Zn-Mg-Cu-Zr) alloy semifinished product having the composition of claim 1 comprising the following steps: a. Melting a charge mixture of primary aluminum and an Al-33wt% Cu master alloy; b. Adding pure zinc element after raising the temperature of the molten charge; c. Superheating the molten charge and adding Al-50wt% Mg master alloy and Mg-28wt% Zr master alloy; d. Adding grain refinement nuclei pellets at reduced temperature; e. Adding degassing pellets; f. Pouring molten metal into a preheated metal mold under argon atmosphere; And g. Solidifying to obtain a cast alloy billet or slab. The method of claim 4, wherein the primary aluminum has a purity of at least 99.80 wt%. 5. The process of claim 4, wherein the charging mixture comprises 76.38-84.81 wt% primary aluminum and 4.54-6.97 wt% master alloy Al-33 wt% Cu. 6. 5. The method according to claim 4, wherein the pure zinc element is added in the range of 8.15-12.65 wt%. The method of claim 4, wherein the Al-50wt% Mg master alloy added to the charging mixture is 2.04-3.32wt%, and the Mg-28wt% Zr master alloy is 0.46-0.68wt%. The method of claim 4, wherein the grain boundary refinement is performed using about 0.01 to 0.1 kg of nuclear pellets. The method according to claim 4, wherein the degassing is performed using 0.01 to 0.5 kg of degassing pellets. The method of claim 4 further comprising the following steps: a. Homogenizing, scalping and extruding the cast alloy billet; And b. Solution-quenching and quenching, followed by stretching the alloy extrudate to achieve a permanent set of 1-1.5% followed by artificial aging to obtain the maximum aged high strength alloy extrudate. 12. The method of claim 11, wherein the homogenization is performed in a first step of 25-35 hours at 440-450 ° C and a second step of 20-30 hours at 450-460 ° C. The method of claim 11, wherein the extrusion process is performed under an initial billet temperature of 400-430 ° C., an extrusion rate of 15: 1 to 25: 1, and ramspeed conditions of 2-5 mm / s. The method of claim 11 wherein the solution treatment is carried out by performing 1-2 hours at 450-460 ° C. followed by water cooling at room temperature. The method of claim 11, wherein the artificial aging treatment is carried out in a two-step process carried out for 6-8 hours at 90-100 ℃ and 20-25 hours at 120-125 ℃. The method of claim 4 further comprising the following steps: a. Homogenizing, scalping and hot rolling the cast alloy slab into sheets, and then cold rolling the sheet with intermediate annealing to obtain an alloy sheet of the required thickness; And b. Solution treatment, quenching and artificial aging to obtain the maximum aged high strength alloy sheet. 17. The method of claim 16, wherein the homogeneous treatment is performed in a first step of 25-35 hours at 445-455 [deg.] C. and a second step of 10-20 hours at 455-465 [deg.] C. The method of claim 16, wherein the hot rolling process is carried out under an initial billet temperature of 425-435 ℃, linear speed conditions of 20 m / min, the intermediate annealing is carried out for 20 minutes at 415-425 ℃ Way. 17. The process of claim 16 wherein the cold rolling process is carried out in a plurality of stages at room temperature, each stage reducing the thickness by 15-25% by three passes and intermediate annealing at 415-425 [deg.] C. for 15-20 minutes. And then cooling in air. The method according to claim 16, wherein the solution treatment is carried out at 450-460 ° C. for 1-1.5 hours followed by water cooling at room temperature. 17. The method of claim 16, wherein the artificial aging is carried out in a two-step process carried out at 90-100 ° C. for 6-8 hours and then at 115-125 ° C. for 20-25 hours.

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