CN1965098A - Heat treatable Al-Zn-Mg alloy for aerospace and automotive castings - Google Patents

Abstract

A heat treatable aluminum alloy for shaped castings includes from about 3.5-5.5 % Zn, from about 1-1.5 % Mg, less than about 1 % Si, less than about 0.30 % Mn, and less than about 0.3 % Fe and other incidental impurities.

Description

The heat treatable Al-Zn-Mg alloy that is used for aviation and automobile casting

(cross reference of related application)

The application requires the rights and interests of the U.S. Provisional Application sequence number 60/564813 of submission on April 22nd, 2004, incorporates it into this paper by reference at this.The application also is closely related with the patent application of submitting to simultaneously with the application " heat treatable Al-Zn-Mg-Cu alloy (Heat treatable Al-Zn-Mg-Cu Alloy for Aerospaceand Automotive) that is used for aviation and automobile casting ", incorporates it into this paper by reference at this.

Technical field

The present invention is the aluminium alloy that is used for the special-shaped casts of aviation and automobile, comprise the foundry goods of this alloy and make the method for the cast component of this alloy.

Background technology

The cast aluminium part is used in the structure applications in the automotive suspension with weight reduction.The most frequently used group of alloys Al-Si ₇-Mg has the good breakdown point of determining.In order to obtain lighter weight part, need have the more high-intensity material of definite designing material performance.At present, by the cast material that A356.0 makes, promptly the most frequently used Al-Si ₇-Mg alloy can guarantee the tensile yield strength and 8% or bigger unit elongation of ultimate tensile strength, the 220MPa (31908psi) of 290MPa (42060psi) reliably.

The many instead of alloy that exist and register show and compare Al-Si ₇The intensity that-Mg alloy is high.But, these alloys castability, corrosion potential or mobile aspect show the problem that is difficult for overcoming.Therefore these substituting alloys are unsuitable for using.

Under the high-intensity situation of needs, often use forging product.These products are usually than cast article costliness.If cast article can be used for replacing forging product and do not lose intensity, unit elongation, erosion resistance, fatigue strength etc., there are sizable cost savings potentiality so.All be like this in automobile and aerospace applications.

Show and compare Al-Si ₇The tensile strength that-Mg material is high and the casting alloy of fatigue resistance are desirable.These raisings can be used for alleviating the weight of new parts or existing part, can utilize the improvement material property that these parts are redesigned to obtain big advantage.

Summary of the invention

Alloy of the present invention is the Al-Zn-Mg base alloy that is used for low pressure permanent mold casting or semipermanent mold casting, squeeze casting, high pressure diecasting, pressure die casting or gravitational casting, lost foam casting (lost foam), investment cast, vacuum casting (V-mold casting) or sand casting, and this alloy has following composition range (all being unit with the weight percent):

Zn: about 3.5～5.5%;

Mg: about 0.8～1.5%;

Si: less than about 1.0%;

Mn: less than about 0.30%; With

Fe and other incidental impurities: less than about 0.30%.

Can use the highest about 1.0% silicon to improve castability.Can use lower level silicon to improve intensity.Use for some, can use the highest about 0.3% manganese to improve castability.In other was used, manganese should be avoided.

This alloy also can comprise such as TiB2, TiB ₂Or the grain-refining agent of titanium carbide TiC and/or such as the anti-recrystallizing reagent of zirconium or scandium.If use TiB2 as grain-refining agent, the boron concentration in the alloy can be 0.0025～0.05% so.Similarly, if use titanium carbide as grain-refining agent, the carbon concentration in the alloy can be 0.0025～0.05% so.Typical grain-refining agent is to comprise TiC or TiB ₂Aluminium alloy.

If use zirconium to prevent grain growing in the solution heat treatment process, its consumption is usually less than 0.2% so.Also can in being lower than 0.3% scope, use scandium.

The objective of the invention is to, provide have good strength, be applicable to the good castability that forms shaped casting, a class aluminium alloy of good solidity to corrosion and good thermal-shock resistance.Thin grain-size is normally desirable for intensity and outward appearance, and the parts that apply bright finish coat for anodizing then are especially true.

In one aspect, the present invention is the aluminium alloy that comprises about 3.5～5.5% Zn, about 0.8～1.5% Mg.It comprises less than about 1% Si, Mn less than about 0.30% and less than about 0.30% Fe and other incidental impurities.

In another aspect, but the present invention be a kind ofly comprise about 3.5～5.5%Zn, about 0.8～1.5%Mg, less than about 1%Si, less than about 0.30%Mn with less than the thermal treatment shaping foundry goods of the aluminium alloy of about 0.30% Fe and other incidental impurities.

In another aspect, but the present invention is a kind of method of preparation heat-treatable aluminum alloy shaped casting.This method comprises: preparation comprises about 3.5～5.5%Zn, about 0.8～1.5%Mg, less than about 1%Si, less than about 0.30%Mn with less than the melt of the aluminium alloy of about 0.30% Fe and other incidental impurities.This method also comprises: casting at least a portion melt in being configured to produce the mold of shaped casting; Make melt solidifying; With from mold, shift out shaped casting.

Description of drawings

Accompanying drawing provides the result of the ASTM G44 stress corrosion (cracking) test of the Al-Zn-Mg alloy that has and do not have copper.

Embodiment

When any numerical range of mentioning here, these scopes should be understood that to comprise each integer and/or the mark between described stated range minimum and the maximum value.For example, the scope of about 3.5～5.5 weight %Zn obviously comprises about 3.6,3.7,3.8 and 3.9% so upwards and comprise all intermediate values of 5.3,5.35,5.4,5.475 and 5.499% Zn always.This is equally applicable to other numerical property and/or elemental range of described here each.

Compare with the copper bearing Al-Zn-Mg alloy phase of similar bag, alloy according to the present invention is carried out.Make sample with 0.1 ℃/second rate of cooling directional freeze.In table 1, provide the result.

Table 1

Directional solidification casting T5 and T6 performance
								T5			T6
Alloy	Tensile strength	Yield strength	E％	Tensile strength	Yield strength	E％
							Al-4.5Zn-1.2Mg	266	192	10	275	223.5	10
265.5	198	8	268	222.5	10
						Al-4.5Zn-1.2Mg-0.4Si		238	174.5	10	309	230.5	16
238.5	173.5	10	312.5	233	16
							Al-4.5Zn-1.2Mg-0.25Cu	285.5	207	10	269.5	210.5	10
287	205	12	276	210.5	14
						Al-4.5Zn-1.2Mg-0.25Cu- 0.12Zr		295	229	4	338.5	278.5	12
298.5	227.5	4	329.5	266	10

First kind of alloy shown in the table 1 is Al-4.5Zn-1.2Mg.Two samples that are respectively T5 and T6 state (temper) are tested.For two samples of this alloy of T5 and T6 state, be that unit provides tensile strength and yield strength with the megapascal (MPa), provide unit elongation with per-cent.This alloy is embodiments of the invention.

Second kind of alloy shown in the table 1 also has the composition in the scope of the invention.It comprises Al-4.5Zn-1.2Mg-0.4Si.Under the T5 state, the value of this tensile strength of alloys and yield strength is lower than last a kind of alloy.But under the T6 state, the value of its tensile strength, yield strength and unit elongation is significantly higher than a kind of alloy.

The third alloy shown in the table 1 is not in compositing range of the present invention.Providing of it is in order to compare.The value of the third alloy tensile strength and yield strength and unit elongation under the T5 state is than second kind of alloy height of T5 state, but under the T6 state, the value of tensile strength, yield strength and unit elongation is lower than second kind of alloy.

The 4th kind of alloy shown in the table 1 be not also in compositing range of the present invention.Providing of it also is in order to compare.The data declaration that provides may prevent the effect of the zirconium of grain growing.The result of T6 state shows the value of very high tensile strength, yield strength and unit elongation.

In first factory is on probation, test mechanical property, and in table 2, provide the result according to the shaped casting of alloy of the present invention.

Table 2

First factory tries out Al-3.5Zn-0.97Mg
					State	Sample number	Tensile strength	Yield strength	E％
T5	1	219	175	14.6
					2	211	169	8.6
	As cast condition	3	185	147					15.03
4					189	152	15.95

Being used for first factory composition on probation is Al-3.5Zn-0.97Mg.Be that unit provides tensile strength and yield strength with the megapascal (MPa) in the table, and be that unit provides unit elongation with per-cent.Two samples of test T5 state, and two samples of test as cast condition material.The unit elongation of noticing the as cast condition material has 15.03% and 15.95% outlier.

The alloy of the magnesium more than also comprising slightly to the alloy of comparing table 1 in second factory is on probation is tested.In table 3, provide second factory data on probation.

Table 3

Second factory tries out Al-3.5Zn-1.1Mg
				Tensile strength	Yield strength	E％	State
210	161	16.7	160℃/1hr
				215	145	6.5	160℃/6hrs
246	175	10.5	143℃/32hrs

Data in the table 3 are about comprising the alloy of Al-3.5Zn-1.1Mg.This is according to alloy of the present invention.Provide three kinds of different heat treated data.First kind is 160 ℃ of insulations 1 hour, and second kind is 160 ℃ of insulations six hours, and the third is 143 ℃ of insulations 32 hours.Tensile strength and yield strength value in this table are represented with megapascal (MPa), and unit elongation is represented with per-cent.

Table 4 provides the data of the alloy identical with sample in the table 3.The sample of report carries out T6 thermal treatment in the his-and-hers watches 4, and this thermal treatment is 471 ℃ of insulations 3 hours, 10 hours cold-water quench subsequently of 527 ℃ of insulations then.Then such as table 4 record sample is carried out timeliness, obtain the stress result in the table 4 then.In the table first row is about only carrying out the sample of natural aging.

Table 4

Al-3.5Zn-1.1Mg after the T6 thermal treatment
				Aging temp/time	Tensile strength	Yield strength	E％
Natural aging only	274MPa	138MPa	24.5
				160 ℃/6 hours	272MPa	177MPa	16.5
160 ℃/12 hours	287MPa	201MPa	16.0
				160 ℃/18 hours	309MPa	230MPa	15.0
143 ℃/12 hours	270MPa	175MPa	17.5
				143 ℃/32 hours	288MPa	197MPa	15.5
143 ℃/64 hours	311MPa	239MPa	11.5

Also use the ASTM G44 of " Standard Practice for Exposure of Metals andAlloys by Alternate Immersion in Neutral 3.5% Sodium ChlorideSolution " by name to carry out corrosion test.In this test, the sample that is added with stress is carried out circulation in 1 hour, this circulation comprises: immerse in the 3.5%NaCl solution and to be placed in the air of laboratory 50 minutes in 10 minutes then.To the sample stress application to they yield strength 75%, and move this test 180 days.

Accompanying drawing has shown the result of this test.As can be seen, under high magnesium level, need copper to prevent stress corrosion crack.But,, do not need copper for low magnesium level of the present invention (about 1.2%Mg).

Provided the preferred embodiments of the invention above, but should be understood that and in the scope of appended claims, to implement the present invention in other mode.

Claims (27)

1. But 1. heat-treatable aluminum alloy that is used for shaped casting, described aluminium alloy comprises following alloying constituent by weight percentage:

   Zn: about 3.5～5.5%;

   Mg: about 0.8～1.5%;

   Si: less than about 1%;

   Mn: less than about 0.30%; With

   Fe and other incidental impurities: less than about 0.30%.
2. 2. according to the aluminium alloy of claim 1, also comprise at least a grain-refining agent that is selected from boron, carbon and combination thereof.
3. 3. according to the aluminium alloy of claim 2, wherein said at least a grain-refining agent comprises about 0.0025～0.05% boron.
4. 4. according to the aluminium alloy of claim 2, wherein said at least a grain-refining agent comprises about 0.0025～0.05% carbon.
5. 5. according to the aluminium alloy of claim 1, also comprise at least a anti-recrystallizing reagent of selected among zirconium, scandium and combination thereof.
6. 6. according to the aluminium alloy of claim 5, wherein said at least a anti-recrystallizing reagent comprises and is lower than 0.2% zirconium.
7. 7. according to the aluminium alloy of claim 5, wherein said at least a anti-recrystallizing reagent comprises and is lower than 0.3% scandium.
8. 8. according to the aluminium alloy of claim 1, wherein said zinc concentration is about 4.2～4.8%.
9. 9. according to the aluminium alloy of claim 1, wherein said zinc concentration is about 4.4～4.6%.
10. 10. according to the aluminium alloy of claim 1, the concentration of wherein said magnesium is about 1.0～1.4%.
11. 11. according to the aluminium alloy of claim 10, the concentration of wherein said magnesium is about 1.1～1.3%.
12. 12. according to the aluminium alloy of claim 1, the concentration of the iron in the wherein said alloy is less than about 0.3%.
13. 13. according to the aluminium alloy of claim 1, the concentration of the manganese in the wherein said alloy is less than about 0.3%.
14. 14. the shaped casting of an aluminium alloy, wherein said alloy comprises following alloying constituent:

    Zn: about 3.5～5.5%;

    Mg: about 0.8～1.5%;

    Si: less than about 1%;

    Mn: less than about 0.30%; With

    Fe and other incidental impurities: less than about 0.30%.
15. 15. according to the shaped casting of claim 14, this shaped casting is the shaped casting after the T5 thermal treatment.
16. 16. according to the shaped casting of claim 14, this shaped casting is the shaped casting after the T6 thermal treatment.
17. 17. according to the shaped casting of claim 14, wherein said zinc concentration is about 4.2～4.8%.
18. 18. according to the shaped casting of claim 14, wherein said zinc concentration is about 4.4～4.6%.
19. 19. according to the shaped casting of claim 14, the concentration of wherein said magnesium is about 1.0～1.4%.
20. 20. according to the shaped casting of claim 14, the concentration of wherein said magnesium is about 1.1～1.3%.
21. 21. a method of making the aluminium alloy shaped casting, described method comprises:

    The melt of preparation aluminium alloy, described alloy comprises following alloying constituent:

    Zn: about 3.5～5.5%;

    Mg: about 0.8～1.5%;

    Si: less than about 1%;

    Mn: less than about 0.30%;

    Fe and other incidental impurities: less than about 0.30%;

    Be configured to produce at least a portion of casting described melt in the mold of described shaped casting;

    Described melt is solidified in described mold; With

    From described mold, shift out described shaped casting.
22. 22., also comprise described shaped casting carried out T5 thermal treatment according to the method for claim 21.
23. 23., also comprise described shaped casting carried out T6 thermal treatment according to the method for claim 21.
24. 24. according to the method for claim 21, wherein said zinc concentration is about 4.2～4.8%.
25. 25. according to the method for claim 21, wherein said zinc concentration is about 4.4～4.6%.
26. 26. according to the method for claim 21, the concentration of wherein said magnesium is about 1.0～1.4%.
27. 27. according to the method for claim 21, the concentration of wherein said magnesium is about 1.1～1.3%.