CN101193839A

CN101193839A - High strength aluminum alloys and process for making the same

Info

Publication number: CN101193839A
Application number: CNA2006800173184A
Authority: CN
Inventors: C·E·布鲁克斯; R·C·多沃德; R·D·帕金森; R·A·马鲁斯卡; M·沙阿巴夫
Original assignee: Kaiser Aluminum and Chemical Corp
Current assignee: Kaiser Aluminum and Chemical Corp
Priority date: 2005-03-24
Filing date: 2006-03-22
Publication date: 2008-06-04
Anticipated expiration: 2026-03-22
Also published as: CN101193839B; EP1902150B1; US20100180988A1; SI1902150T1; WO2007102831A1; WO2007102831A8; EP1902150A1; EP1902150A4; US20060213591A1

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

Aldural and preparation method thereof

The cross reference of related application

The application contains the relevant theme of theme of No. the 10/829391st, the U.S. Patent application submitted on April 22nd, 2004.

Background of invention

1. invention field

The present invention relates generally to aldural based on the Al-Zn-Mg-Cu alloy system and preparation method thereof.Although be not limited thereto, alloy of the present invention is particularly suitable for sports goods and aviation articles for use.

2. background note

Present known maximum intensity aluminium alloy is based on aluminium-zinc-magnesium-copper system.The present commercialization high-strength alloy of producing comprises AA7055 (nominal 8%Zn-2%Mg-2.2%Cu-0.10%Zr), AA7068 (nominal 7.8%Zn-2.5%Mg-2.0%Cu-0.10%Zr), is called the Kaiser aluminium alloy (nominal 8%Zn-2.2%Mg-1.8%Cu-0.14%Zr) of K749.K749 is near phase boundary as can be seen in the facies relationship of 860  for the alloy that contains 8%Zn from document, and other two kinds of alloys are in heterogeneous zone.In the later case, be not that all alloying elements all are in the sosoloid when 860 , not only can not be used for aging sclerosis, and remaining not dissolving mutual-assistance toughness reduces after thermal treatment.Can dissolve more solute although carry out solution heat treatment at the comparatively high temps that surpasses 860 , but must take more care to guarantee that eutectic melting does not take place alloy, this is a problem common in the industrial cast alloys, causes the Local enrichment zone owing to microsegregation takes place in the casting cycle.

In many application of sports goods and aviation articles for use and so on, need stronger alloy based on aluminium-zinc-magnesium-copper system, and the toughness of sacrificial alloy not.But this needs have proposed a problem, because generally speaking, along with the tensile strength increase of aluminium alloy, its toughness descends.

Summary of the invention

The present invention has solved the problems referred to above with several different methods.More specifically, there are three kinds of different approach when keeping the alloy toughness, to improve the intensity of alloy: rich alloy (rich alloy) chemistry; Handle so that the alloy maximizing efficiency; Prevent recrystallize.Rich alloy provides more may can be used in the aging solute that is hardened to higher strength level; Effectively handle and guarantee that solute can be used in and strengthen and do not break away from from solution as second, solute breaks away from from solution as second can reduce fracture toughness; Maintenance can make intensity and toughness reach optimization without the microstructure of recrystallization.

For by using the rich alloy chemistry that tensile strength is increased and not sacrificing toughness, the present invention includes aluminium alloy based on the Al-Zn-Mg-Cu alloy system and preferably include high-load zinc and copper but the magnesium of moderate contents.As selection scheme, can also use a small amount of scandium to prevent recrystallization.Each alloy preferably comprises the Zn of at least 8.5 weight % and the Cu of 2.25 weight %.The upper content limit of these elements can be about 10.5%Zn and 3.0%Cu.But, preferably use the Mg (maximum 1.85%) of suitable low levels so that the content of Cu can be high.The preferable range of all elements comprises 8.5-10.5 weight %Zn in the alloy, 1.4-1.85 weight %Mg, and 2.25-3.0 weight %Cu is no more than about 0.5% Zr, V or at least a element among the Hf, and surplus is aluminium and incidental impurity basically.In preferred embodiment, also comprise 0.05-0.30%Sc in the alloy, to prevent recrystallization.In addition, have been found that the overall weight percent along with magnesium and copper increases, the alloy toughness descends.The ideal range of verified these the two kinds of elements of experiment is to amount to 4.1% to 4.5%.In addition, the weight percentage sum of Zn, Cu and Mg is preferably between 13.0% to 14.5%.

In order to make the process interalloy efficient maximum that forms alloy, preferably alloy cast ingot after, carry out the homogenizing processing, wherein when alloy is heated to as far as possible temperature near its fusing point, adopt slower temperature rise rate.Particularly, for the last 20-30  that is lower than fusing point, temperature rise rate be limited in be equal to or less than 20 /hour, thereby make the amount of low melting point eutectic phase minimum, further improve the fracture toughness of alloy.Make ingot casting form final shape in case use to extrude with the rolling step, then product preferably carries out solution heat treatment at 870-900 , carries out temper(ing) then.Can carry out burin-in process by making one step of product experience, two steps or three step heat treatment processes.In the first step, product was at Temperature Treatment 3-30 hour of 175-310 .In the second optional step, be that the temperature at 310-360  heated 2-24 hour the first step after.At last, in optional third step, product heated 1-30 hour in the temperature of 175-300 .As the scheme that another kind is selected, can use the second and the 3rd aging step, and not carry out the first aging step.

Above-mentioned alloy and treatment measures have improved the character of Al-Zn-Mg-Cu alloy system, make them can more effectively be used for many application.Can use the specific product or the article of alloy of the present invention to comprise: sports goods comprises the Baseball and Softball rod, golf club, crosse, tennis racket and arrow; The aviation articles for use comprise aerospace parts, and for example wing plate, bulkhead, body longeron, structure are extruded part and forging; Weapon component, for example shell case and missile launcher.

Brief Description Of Drawings

In conjunction with the drawings preferred implementation of the present invention being carried out following detailed description can clearly understand the features and advantages of the present invention, wherein:

Fig. 1 has described the funtcional relationship of T6 intensity (YTS and UTS) with total alloy percentage composition of the many sample alloy that form according to preferred implementation;

Fig. 2 has described the funtcional relationship of total percentage composition of the Cu of fracture toughness and the sample alloy that forms according to preferred implementation and Mg;

Fig. 3 is the equilibrium phase diagram of the funtcional relationship of the percentage composition of Cu and Mg in facies relationship that is illustrated in 885  and the alloy that contains 9%Zn that forms according to preferred implementation;

Fig. 4 represents the influence of the ratio of Mg and Cu to the fracture toughness of the alloy of foundation preferred implementation formation;

Fig. 5 represents the second phase volume percentage ratio and the funtcional relationship that forms heating rate in the alloy A A7068 process;

Fig. 6 represents the influence of scandium to the intensity of Al-8%Zn-2.2%Mg-1.9%Cu alloy.

The detailed description of preferred implementation

Following examples have illustrated alloy modification and effectively handled is the character that how to be used to improve according to the Al-Zn-Mg-Cu alloy system of preferred implementation of the present invention, thereby makes them can more effectively be used for sports goods and aviation articles for use.

Embodiment 1

Also there is not at present the compositing range of the Al-Zn-Mg-Cu alloy system of research to comprise about 9% to 10% zinc, 2.2% to 2.8% bronze medal and 1.6% to 2.0% magnesium.Alloy shown in the table 1 is cast into the blank of 9 inch diameters: notice that these alloys contain 0.05% the scandium of having an appointment, a kind ofly be used in combination the element that can effectively prevent recrystallization with zirconium.

Table 1. alloy composition

Alloy	Weight %
	Weight %							Si	Fe	Cu	Mg	Zn	Zr	Sc
	179 180 189 190 191 192 200 202 203 204 209 213 214 215 216	0.04 0.04 0.04 0.03 0.03 0.04 0.04 0.04 0.04 0.03 0.04 0.03 0.03 0.04 0.03	0.07 0.09 0.08 0.09 0.11 0.10 0.09 0.12 0.10 0.10 0.08 0.07 0.09 0.09 0.10	2.47 2.71 2.14 2.31 2.35 2.33 2.58 2.46 2.69 2.88 2.64 2.42 2.56 2.57 2.81	1.83 1.89 1.89 1.86 1.81 1.87 1.64 1.66 1.78 1.58 1.49 1.63 1.44 1.73 1.60	8.87 8.95 8.60 9.21 9.63 10.13 8.84 8.87 8.94 8.78 8.78 9.65 9.50 9.82 9.65	0.14 0.13 0.12 0.13 0.13 0.12 0.12 0.13 0.13 0.12 0.14 0.13 0.14 0.12 0.13	Si	Fe	Cu	Mg	Zn	Zr	Sc	0.06 0.06 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05

Blank is in 880F homogenizing (F represents Fahrenheit degree), and extruding and forming diameter is 4 inches seamless tube, and thickness of pipe is 0.305 inch.Extrude part and carry out solution heat treatment at 880F, quenching in cold water, " peak value (peak) " aging (peak aged) is to T6 degree of temper (the equal thermal treatment of 250F 24 hours).Test their tensile properties longitudinally, extrude a part cutting part from all, flatten the workpiece that becomes about 12 square inches (12 " square), this workpiece also carries out solution heat treatment at 880F, quenching in cold water, and it is aging to carry out peak value.Test the fracture toughness (ASTMB645) of part on the T-L orientation of these pressings.Stretching and fracture toughness character are shown in Table 2.

Table 2. stretches and fracture toughness character

％Zn	％Cu	％Mg	Intensity (ksi)		Toughness (ksi rt.in)
			Intensity (ksi)		Toughness (ksi rt.in)		UTS	YTS	Kq	Kp
			8.60 9.21 9.63 10.13 8.87 8.95 8.84 8.87 8.94 8.78 8.78 9.65 9.50 9.82 9.65	2.14 2.31 2.35 2.33 2.47 2.71 2.58 2.46 2.69 2.88 2.64 2.42 2.56 2.57 2.81	1.89 1.86 1.81 1.87 1.83 1.89 1.64 1.66 1.78 1.58 1.49 1.63 1.44 1.73 1.60	97.1 100.1 99.9 103.2 101.1 102.9 98.6 98.4 100.0 99.1 96.4 100.3 98.5 102.6 100.6	UTS	YTS	Kq	Kp	88.5 93.9 94.2 97.8 92.2 93.7 93.8 92.8 94.2 93.8 91.9 96.3 94.9 98.2 97.1	25.2 22.4 20.9 21.2 20.9 20.1 23.1 25.3 24.2 24.8 24.8 24.7 26.2 21.9 20.0	30.5 27.5 25.4 24.0 23.9 20.5 25.8 22.2 22.4 21.9 22.9 21.3 21.2 18.2 18.4

As can be seen from Table 2, the tensile yield strength of most of alloy all surpasses 90ksi, and two kinds of compositions reach about 98ksi.As shown in Figure 1, intensity is closely related with total alloy content, every increase by one percent by weight, and the tension surrender is slight to increase about 4.8ksi.In the equilibrium phase explained of homogenizing and solution heat treatment temperature the reason of this phenomenon.Fig. 3 has shown that how relevant the composition shown in the table 1 is with the alloy that contains nominal 9% zinc at the magnesium of 885F and the solubility limit of copper.The composition of the line of delimitation between sosoloid and Al+S region (being solvus) below is a single-phased alloy, and the alloy phase ratio of this alloy and 2 regions has more superior fracture toughness for given strength level.The best of breed of intensity and toughness is those alloys near solvus, Here it is why the composition of 2.7%Cu/1.9%Mg have lower tenacity levels.Therefore, be positioned at almost in the dotted line scope parallel preferred the composition with solvus.These relations are controlled at 4.1% to 4.5% by the total concn with copper and magnesium and limit.

Although above-mentioned character is to carry out " standard " T6 tempering burin-in process by the product that will be shaped in 175-310F heating 3-30 hour (particularly preferably in 250F heating 24 hours) to reach, just like most of Al-Zn-Mg-Cu alloys, but according to required properties of combination, it also is favourable using other embodiment.For example, will forming #213, to be drawn into diameter be 2.625 ", thickness of pipe is 0.110 " pipe, and by the 2-footwork aging 8 hours of 250F, the yield strength and the tensile strength of the pipe that obtains after 305F is aging 4 hours are respectively 100.9ksi and 102.6ksi.Similarly, can be in second step, the temperature in the 310-360F temperature range is handled the overaging that surpasses aging intensity that described alloy carried out 2-24 hour, thereby the combination of required intensity and erosion resistance is provided.Another preferred embodiment is included in the third step, and the lesser temps in the 175-300F scope carries out 1-30 hour final burin-in process, and this processing is further gained in strength, and can not damage corrosion-resistance properties.Perhaps, can only carry out the above-mentioned second and the 3rd aging step and omit first step alloy.

Embodiment 2

For alloy more of the present invention and other have the high zinc alloy of commodity such as AA7036, AA7056 and the AA7449 of higher Mg/Cu ratio (1.0-1.4), according to the following alloy of embodiment 1 described preparation.

The composition of table 3. comparative alloy

Alloy number	Weight %
	Weight %							Si	Fe	Cu	Mg	Zn	Zr	Sc
	36 39 43 47	0.03 0.04 0.03 0.04	0.06 0.05 0.03 0.06	1.91 1.28 1.44 1.59	2.17 2.74 2.62 2.34	9.02 9.02 9.04 8.95	0.15 0.13 0.13 0.14	Si	Fe	Cu	Mg	Zn	Zr	Sc	0.05 0.06 0.05 0.06

The yield strength and the toughness values of these alloys are shown in the following table.

The mechanical properties of table 4. comparative alloy

Alloy	The Mg/Cu ratio	％(Mg+Cu)	Yield strength (ksi)	Kpmax(ksi rtin.)
Alloy	The Mg/Cu ratio	％(Mg+Cu)	Yield strength (ksi)	Kpmax(ksi rtin.)	36 47 43 39	1.14 1.47 1.77 2.14	4.08 3.93 3.99 4.02	94.9 93.9 93.9 92.7	24.5 22.7 21.3 20.2

Fig. 4 has compared the tenacity levels of alloy that has the composition of similar strength level (93-95ksi) and total Mg+Cu content (4.0-4.2%) based on these alloys of Mg/Cu ratio and use of the present invention.

Embodiment 3

As previously noted, undissolved second no longer residual after processing be very important, can make fracture toughness reach maximum value like this.This point is abundant and particularly important near the alloy at place, balance solid solution phase boundary line for alloying constituent.For the amount that illustrates how homogenizing influences the undissolved phase of this class if being handled, use differential scanning calorimeter (DSC) to begin to heat from 850F, measure the energy relevant that begins from about 885F with eutectic melting with the AA7068 alloy billet sample of different speed with casting.This energy measure be directly proportional in undissolved second residual mutually the amount of first fusing point, the mutual relationship between these factors is determined by quantitative microscopic method.Fig. 5 has shown how heating rate influences the amount of this phase of being determined by the DSC data.

Notice that about 10F/ hour slow heating rate reduces to the amount of second phase and is lower than 1 volume %.Can estimate that about 5F/ hour heating rate will make " solvable " part reduce near 0.The inventor is also noted that the heating rate for 10-20F/ hour, undissolved eutectiferous volume fraction is no more than the amount (irrelevant with heating rate or homogenization temperature) of the composition of the insoluble Fe of containing, and the nominal content of Fe is 0.12%Fe (about 1 volume %) in the described composition.

Embodiment 4

Have realized that for many years the combination of scandium and zirconium is effective recrystallization inhibitor.Mention " scandium of adding 0.1-0.3% and the zirconium of 0.05-0.15% are favourable in aluminium alloy " in Muscovite one piece of summary.But, " for do not contain insoluble mutually in the alloy of scandium bonded alloying element ...., observe maximum effect ...; When copper [scandium combines with copper] limited amount, be fine " with the zirconium alloying of scandium and Al-Zn-Mg-Cu and Al-Cu-Li alloy.Therefore, " developed commercial alloy " based on Al-Zn-Mg-Sc-Zr (01970,01975).

Two shortcomings that the interpolation scandium may cause in the 7XXX alloy that contains 2% bronze medal of having an appointment are tangible:

1) copper content is too high, and be enough to combine, thereby make scandium invalid with scandium,

2) the price height of scandium; About 0.2% content will make the cost of aluminium alloy increase about $10/ pound.

Therefore, if use effectively below the content that scandium can be advised in being lower than Russian document, then be very attracting on economy and technology.

It is 5 that the alloy of the composition that following table is listed is prepared into diameter " blank, according to hereinafter described handling.Although this alloy sample contains more Mg and less Cu than the preferred alloy of being discussed before, believe the preferred alloy of the same acquisition of the effect of in alloy, adding Sc.

Alloy number	Weight %
	Weight %							Si	Fe	Cu	Mg	Zn	Zr	Sc
	A B C D E	0.03 0.03 0.03 0.03 0.03	0.04 0.05 0.05 0.04 0.05	1.95 1.86 1.89 1.84 1.95	2.20 2.17 2.18 2.12 2.18	8.07 8.05 8.09 8.11 8.08	0.11 0.00 0.11 0.12 0.11	Si	Fe	Cu	Mg	Zn	Zr	Sc	0.00 0.22 0.06 0.11 0.22

The heating rate of using 50F/ hour is at 875F homogenizing ingot bar, and air cooling, and then be heated to 800F, extruding is 0.25 " * 3 " flat bars.A part of respectively extruding part is cooled to 450F 755F annealing 3 hours with 50F/ hour speed, keeps 4 hours, with 50F/ hour speed cool to room temperature.Then, these parts to subtract thick (always subtracting thick rate is 84%) cold rolling by five passages be 0.040 " thin slice.Thin slice carried out solution heat treatment 30 minutes at 885F, and quenching in cold water is aged to peak strength state (handling 10 hours at 305F) then.The rod of extruding carries out similar thermal treatment, and the cross directional stretch character of two kinds of products of test is shown in hereinafter.Also shown the specific effect of scandium among Fig. 6 to intensity.

Alloy number	％Zr	％Sc	UTS(ksi)		Yield strength (ksi)
			UTS(ksi)		Yield strength (ksi)		Extrude part	Thin slice	Extrude part	Thin slice
			A B C D E	0.11 0 0.11 0.12 0.11	0 0.22 0.06 0.11 0.22	94.7 88.2 95.7 95.2 94.5	Extrude part	Thin slice	Extrude part	Thin slice	90.7 92.0 97.1 96.6 96.5	91.4 86.1 92.2 92.2 91.1	87.8 88.4 93.3 93.3 92.5

By these results can clearly draw following some:

1. no matter extrude or sheet form, the strongest alloy contains 0.06%Sc (and 0.11%Zr).

2. be 0.1% o'clock at Zr content, 0.06%Sc can be effectively improves about 6ksi with the intensity of sheet product.

3. under the situation of no zirconium, 0.22%Sc can only improve 1ksi with the intensity of sheet product, and makes the intensity of extruding part reduce about 6ksi.By relatively contain (a) 0.11Zr, (b) 0.11%Zr+0.06%Sc and (c) microstructure of the sheet product of 0.22%Sc (no Zr) confirmed that 0.06% Sc only can prevent the effectiveness of recrystallization.Find out that from above the preferable range of Sc is 0.05-0.30% in the alloy, preferred scope is 0.05-0.10%.

Although described the present invention according to a plurality of preferred implementations and variant thereof, it should be understood that in the case without departing from the scope of the present invention and can carry out many other variations and modification.Therefore, should understand within the scope of the appended claims, the present invention can be different from the form of described mode and carry out.

Claims

1. alloy product with high strength and good toughness, it contains 8.5-10.5 weight %Zn, 1.4-1.85 weight %Mg, 2.25-3.0 weight %Cu and is no more than at least a Zr of being selected from, the V of about 0.5 weight % or the element of Hf, and its surplus is aluminium and incidental impurity substantially.

2. alloy product as claimed in claim 1 is characterized in that described alloy contains the 0.05-0.2%Zr that has an appointment.

3. alloy product as claimed in claim 1 is characterized in that described alloy comprises 0.05-0.30%Sc.

4. alloy product as claimed in claim 3 is characterized in that described alloy comprises 0.05-0.20%Zr.

5. alloy product as claimed in claim 1 is characterized in that described alloy comprises about 0.03-0.10%Si and 0.03-0.12%Fe.

6. alloy product as claimed in claim 1 is characterized in that, the weight percentage sum of Mg and Cu is 4.1-4.5%.

7. alloy product as claimed in claim 6 is characterized in that, the weight percentage sum of Zn, Mg and Cu is 13.0-14.5%.

8. alloy product as claimed in claim 1 is characterized in that, described product is selected from: sports goods comprises Baseball and Softball rod, golf club, crosse, tennis racket and arrow; Aerospace parts comprises that wing plate, bulkhead, body longeron, structure extrude part and forging; Weapon component comprises shell case and missile launcher.

9. method of making alloy product, described alloy product contains 8.5-10.5 weight %Zn, 1.4-1.85 weight %Mg, 2.25-3.0 weight %Cu and is no more than at least a Zr of being selected from, the V of about 0.5 weight % or the element of Hf, its surplus is aluminium and incidental impurity substantially, said method comprising the steps of:

The described alloy product of casting forms the alloy ingot bar;

By be no more than 20 /hour heating rate described ingot bar be heated to second temperature from first temperature come the described ingot bar of homogenizing, make the amount of low melting point eutectic phase minimum, at least about low 20 , described second temperature is than low approximately 5  of described temperature of fusion than the temperature of fusion of described ingot bar for wherein said first temperature.

10. method as claimed in claim 9 is characterized in that, described first temperature is than low approximately 30  of described temperature of fusion.

11. method as claimed in claim 9 is characterized in that, described first temperature is chosen as about 870 , and described second temperature is chosen as 885-890 .

12. method as claimed in claim 9 is characterized in that, described alloy ingot bar kept 8 hours in described first temperature at least.

13. method as claimed in claim 9 is characterized in that, described alloy contains 0.05-0.30%Sc.

14. method as claimed in claim 9, it is characterized in that described alloy ingot bar forms the shape of the finished product, carries out solution heat treatment at 870-900 , carry out temper(ing) then in the first aging step, the described first aging step is 175-310  heating 3-30 hour.

15. method as claimed in claim 14 is characterized in that, described product carried out the second aging step: 310-360  heating 2-24 hour.

16. method as claimed in claim 15 is characterized in that, described alloy product carried out the 3rd aging step: 175-300  heating 1-30 hour.

17. method as claimed in claim 9 is characterized in that, described alloy ingot bar forms the shape of final product, carries out solution heat treatment, carries out temper(ing) then in the first aging step, and the described first aging step is 310-360  heating 2-24 hour.

18. method as claimed in claim 17 is characterized in that, described alloy product carried out the second aging step: 175-300  heating 1-30 hour.