CN1965097A - Heat treatable Al-Zn-Mg-Cu 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 1-3% Mg, about 0.05-0.5% Cu, and less than about 1% Si.

Description

The heat treatable Al-Zn-Mg-Cu 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 alloy 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, the foundry goods that is made of this alloy and the method for making the cast component of this alloy.

Background technology

The cast aluminium part is used in the structure applications in the outstanding part of automobile 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 1～3%;

Cu: about 0.05～0.5%;

Si: less than about 1.0%;

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

Mn: 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 alloy, 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.Can in being lower than 0.3% scope, use scandium equally.

In the T6 state, tensile yield strength that alloy shows than can from A356.0-T6 obtain high by 50%, keep close unit elongation simultaneously.This detail design that will make desired strength be higher than the alloy that can easily obtain at present in Al-Si-Mg alloy such as A356.0-T6 or A357.0-T6 becomes possibility.The fatigue property of T6 state increases by 30% than A356.0-T6 material.

In one aspect, the present invention comprises about 3.5～5.5%Zn, about 1～3%Mg, about 0.05～0.5% Cu aluminium alloy, and it comprises the aluminium alloy less than about 1%Si.

In another aspect, but the present invention a kind ofly comprises about 3.5～5.5%Zn, about 1～3%Mg, about 0.05～0.5%Cu and less than the thermal treatment shaping foundry goods of the aluminium alloy of about 1%Si.

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 1～3%Mg, about 0.05～0.5%Cu and less than the melt of the aluminium alloy of about 1%Si.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

Fig. 1 is the photo that shrinks the cutting surface of the cutting sample of the prior art A356.0 alloy of casting in the mold (shrinkage mold), shows the shrinkage cracking tendency of prior art A356.0 alloy;

Fig. 2 is the photo on cutting surface that similarly shrinks second sample of the technology A356.0 that casts in the mold with Fig. 1, the shrinkage cracking tendency of technique of display A356.0 alloy;

Fig. 3 is the photo that shrinks the cutting surface of the alloy sample of casting in the mold of the present invention, and showing does not have shrinkage cracking;

Fig. 4 is the photo that similarly shrinks the cutting surface of alloy of the present invention second sample of casting in the mold with Fig. 3, and showing does not have shrinkage cracking;

Fig. 5 provides the intensity and the unit elongation data of the directional freeze sample of the present invention under the T6 state;

Fig. 6 is the photo according to preceding steering knuckle (knuckle) foundry goods of alloy of the present invention, shows the position that obtains tension specimen;

Fig. 7 is the tension specimen that cuts from the foundry goods shown in Fig. 6 at T5 and the intensity after the T6 thermal treatment and the chart of unit elongation data in addition;

Fig. 8 is the tired response of the S-N of this alloy under the T6 state (ASTM E 466 tests, graphic representation R=-1) of comparing with the response of prior art A356.0-T6;

Fig. 9 is the graphic representation that shows staged (staircase) fatigue test of alloy of the present invention under the T6 state of comparing with the response of prior art A356.0-T6 with the average fatigue strength of A356.0-T6;

Figure 10 is the diagram that shows the depth of erosion of alloy of the present invention after Huey test of comparing with prior art alloy A 356;

Figure 11 is alloy according to the present invention Photomicrograph in sample as cast condition side after Huey test;

Figure 12 is alloy according to the present invention Photomicrograph in the sample process side after Huey test;

Figure 13 is the Photomicrograph of prior art alloy A 356 after Huey test;

Figure 14 is the diagram that provides the stress corrosion (cracking) test result of the alloy of the present invention that changes with different copper levels;

Figure 15 shows copper and the magnesium level diagram to the influence of the stress corrosion crack of alloy of the present invention.

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%Zn obviously comprises about 3.6,3.7,3.8 and 3.9% 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.

Table I provides the composition data of tested alloy.First and the third line that expression is formed is the foundry goods about directional freeze.Second row is the composition about using in the shaped casting.This shaped casting is a preceding steering knuckle shown in Figure 6.

Table I: alloy composition

The composition of sample (weight %)
										Zn	Mg	Si	Cu	Mn	Fe	Ti	B
Directional solidification castings	4.28	1.99	0.04	0.01	0.00	0.04	0.00	0.0005
									The casting steering knuckle	4.2	2	＜0.1	0.2	0.05	＜0.1	0.06	0.02
Directional solidification castings	4.57	2.03	0.04	0.31	0.04	0.05	0.06	0.02

Table II provides the room-temperature mechanical property of the directional solidificating alloy of forming shown in the first and the 3rd data line with Table I.The directional solidification castings that first data line in the Table II constitutes about natural aging five after week, by the alloy of first data line in the Table I.Second data line in the table 2 is about the same alloy after the T5 thermal treatment, and the 3rd data line is about this alloy after the T6 thermal treatment.In Table II the 4th and the 5th data line are about the alloy in the bottom line of table 1, and this alloy is a copper master alloy.This alloy also passes through T6 thermal treatment.

Table II: directional solidification castings room-temperature mechanical property

State	TYS(MPa)	UTS(MPa)	E1(％)
				F5 (5 all natural aging)	185	322	18
T5	245	323	14
				T6	338	359	7
T6 (high Cu) rate of cooling: 1 ℃/second	382	424	12
				T6 (high Cu) rate of cooling: 0.2 ℃/second	372	412	9

Provide the development of the mechanical property of directional freeze sample of the present invention during the thermal treatment among Fig. 5.In first data line of table 1, provide the composition of these samples.Solution heat treatment is in 1030  (554 ℃) insulation 8 hours, cold-water quench and artificial aging subsequently then.After the artificial aging of various amounts, from stove, take out sample and carry out mechanical test.The performance of measuring is TYS, UTS and per-cent unit elongation.The artificially aged time length is 15 hours.During initial 6 hours, temperature is 250  (121 ℃).For subsequently 9 hours, temperature was 320  (160 ℃).The value of TYS and UTS is with reference to the scale on the left side; The value of per-cent unit elongation is with reference to the scale on the right.

Table III provides the data of the preceding steering knuckle foundry goods shown in Fig. 6.This is according to alloy of the present invention, and has the composition that provides in table 1 second data line.In Fig. 6, marked the position of tension specimen 1,2 and 3.To testing through the heat treated foundry goods of T5 with through the heat treated foundry goods of T6, this T5 thermal treatment is by forming 160 ℃ of insulations in 6 hours, this T6 thermal treatment by 554 ℃ of insulations 8 hours then cold-water quench solution heat treatment and form 121 ℃ of insulations 6 hours with 160 ℃ of artificial agings that are incubated 6 hours.

Steering knuckle room-temperature mechanical property before Table III: the CS

Sample position	State	TYSMPa	USMPa	Unit elongation (%)
					1	T5	163.4	237.9	6
2	189.6	259.2	5
				3	170.3		253.0	10
1	T6	357.8	388.9						6
				2	375.8	419.9	11
3		356.5	400.6					13

Notice, in Table III, for the alloy of T5 and T6 state, all obtain high tensile strength values and good unit elongation.It shall yet further be noted that this composition is the composition that provides in second data line of Table I.In Fig. 7, mark and draw the data that provide in the Table III.

Graphic representation among Fig. 8 shows the tired response of the S-N of the alloy of the present invention of comparing with the response of prior art alloy A 356.0-T6.This test is ASTM E466, R=-1.After 100000 circulations, alloy of the present invention obviously is better than the prior art alloy as can be seen.

Fig. 9 is the graphic representation that shows the staged fatigue test of alloy of the present invention under the T6 state of comparing with the response of prior art alloy A 356.0-T6 with the mean value of the A356.0-T6 that calculates.The composition of alloy of the present invention is the composition that provides in second data line of table 1.

With sample solution heat treatment under the temperature of 526 ℃ or 554 ℃, quenching and under 160 ℃ temperature artificial aging 6 hours.As top see, when comparing with the A356.0-T6 material, the fatigue of these samples response improves greatly.

The average fatigue strength of alloy of the present invention is 109.3 3MPa, and standard deviation is 9.02MPa.The standard deviation of average fatigue strength is 3.01MPa.A356.0 T6 is 10 ⁷The average fatigue strength of the calculating of circulation time is 70MPa.

Use name to be called the erosion resistance of the ASTM G110 corrosion test test alloy of the present invention of " Standard Practice for Evaluating IntergranularCorrosion Resistance of Heat Treatable Aluminum Alloys byImmersion in Sodium Chloride+Hydrogen Peroxide Solution ".

In this test, the sample immersion is comprised the NaCl of 57g/L and the H of 10mL/L ₂O ₂(30%) in the solution 6～24 hour.Then with the sample crosscut, and under opticmicroscope, check the corrosive type (intergranular corrosion or spot corrosion) and the degree of depth.

Figure 10 provides for alloy according to the present invention and alloy A 356.0 diagram at the depth of erosion of ASTM G110 corrosion test after 6 hours and 24 hours.

Figure 11 and Figure 12 are the Photomicrograph of alloy of the present invention after ASTM G110 corrosion test exposes 24 hours.In these Photomicrographs, can see considerably less intergranular corrosion.

Figure 13 is the Photomicrograph of A356.0 alloy after ASTM G110 corrosion test exposes 24 hours.In this Photomicrograph, can see considerable intergranular corrosion.

Corrosion test is carried out in the ASTM G44 test of also using name to be called " Standard Practice for Exposure of Metals andAlloys by Alternate Immersion in Neutral 3.5%Sodium ChlorideSolution ".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.Repeat circulation in this 1 hour continuously.In process of the test, the crackle and the inefficacy of sample are made regular check on.

Table IV is given in the composition according to various alloys of the present invention that uses in the ASTM G44 test.

Table IV

Sample number	Alloy composition
							Zn	Mg	Cu	Ti	B	Zr
	59	4.23	1.5	0.29	0.029	0.0055							＜0.001
86							4.41	1.49	0.23	0.036	0.0038	n/a
	110	4.39	1.74	0.28	0.057	0.0129							＜0.001
117							4.39	1.74	0.28	0.057	0.0129	＜0.001
	138	4.19	1.99	0.26	0.073	0.015							＜0.001
159							4.31	1.93	0.24	0.105	0.0252	0.1127
	A	4.43	2.05		0.06	0.0208
B							4.5	2	0.2	0.06	0.02	n/a
	C	4.5	1.2
D							4.5	1.2

Table V is given in the test-results of the alloy composition that provides in the Table IV.

Table V: ASTM G44 test with alloy of different Mg and Cu content

Round or S number	State	Stress level (MPa)	The per-cent of TYS	F/N	To the fate that lost efficacy
						59 (steering knuckles)	T5	152.37	75％	0/5
86 (steering knuckles)	T6	239.25	75％	4/5	17，17，22，28
						110 (steering knuckles)	T5	154.44	75％	0/5
117 (steering knuckles)	T6	196.50	75％	0/5
						138 (steering knuckles)	T6	247.52	75％	2/5	45，61
159 (steering knuckles)	T6	270.27	75％	3/5	11，11，11
						A	T5	186.16	75％	5/5	4，4，4，7，64
B	T6	182.02	50％	4/4	7，11，13，19
						C	T5	135.83	75％	0/5
D	T6	194.43	75％	0/5

Figure 14 is the diagram that provides the result of these tests.As can be seen, for alloy of the present invention and under these high magnesium levels, increasing copper can provide the enhanced stress corrosion dehiscence resistant.

Figure 15 shows copper and the magnesium level diagram to the influence of the stress corrosion crack of alloy of the present invention.This figure shows, for have 1.5～2% magnesium according to alloy of the present invention, wish to comprise 0.25～0.3% copper.

Table VI and VII provide the result on probation of factory who carries out revision test (shot) from single liquid metal pool.Try out April 4 for one and carry out; One June 4 carry out and one carried out September 4.In every day, all compositions of making foundry goods all change slightly.

Table VI provides the compositing range of the sample of taking from each test day.These compositions comprise high-caliber magnesium and copper, are expected to provide especially high strength level.

Table VI: the scope of MCC factory alloy composition on probation

Date	Si	Fe	Mn	Cu	Mg	Zn	Ti	B	Zr
										April 4	0.05- 0.09	0.03- 0.04	0.03- 0.04	0.22- 0.27	1.9- 2.2	4.1- 4.7	0.03- 0.06	0.001- 0.0007	0.00- 0.15
June 4	0.03- 0.09	0.04- 0.08	0.04- 0.05	0.24- 0.29	1.5- 2.0	4.6- 4.9	0.03- 0.11	0.008- 0.025	0.00- 0.12
										September 4	0.04- 0.05	0.14- 0.20	0.03- 0.04	0.27- 0.32	2.1- 2.3	4.4- 4.9	0.04- 0.07	0.0006 - 0.0037	0.13- 0.14

Table VII provides stress data, ultimate tensile strength, tensile yield strength and the unit elongation of four different positionss in each foundry goods.The row of expression sample number mark each foundry goods.Locative row limit each mechanical test sample that cuts from foundry goods.

Table VII: the mechanical property during factory is on probation

Sample	The position	UTS (MPa)	YTS (MPa)	Unit elongation (%)	Sample	The position	UTS (MPa)	YTS (MPa)	Unit elongation (%)
										In April, 2004 test					In June, 2004 test
1-019 1-019 1-019 1-019 1-024 1-024 1-024 1-024 2-007 2-007 2-007 2-007 2-024 2-024 2-024 2-024 3-165 3-165 1-014 1-014 1-014 1-014	1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 1 4 1 2 3 4	337 386 375 405 345 384 388 406 371 382 381 419 349 381 369 408 331 436 371 392 348 392	269 349 357 365 301 355 359 370 330 340 352 378 301 340 342 370 268 382 335 352 318 357	9.9 9.5 3.1 10.6 8.1 8.2 6.3 9.7 4.7 8.2 5.5 9.25 8.5 9.25 3.7 11.7 10.1 8.85 6.1 8.4 5.1 7.5	86 86 86 86 117 117 117 117 138 138 138 138 138 138 159 159 159 159 159 159 166	1 2 3 4 1 2 3 4 1 2 3 4 1L 1U 1 2 3 4 1L 1U 4	268 359 319 366 238 305 291 331 264 367 343 375 373 356 326 392 368 404 407 413 393	216 321 294 339 193 254 244 286 198 320 308 341 334 333 265 352 339 369 359 375 354	9.3 9.2 6.7 6.7 12.3 14.6 8.5 8.4 8.9 8.8 7.5 8.9 6.6 6.4 9.7 11.7 7.2 9.3 9.2 7.9 7.2
										In September, 2004 test
Sample	The position	UTS (MPa)	YTS (MPa)	Unit elongation (%)	Sample	The position	UTS (MPa)	YTS (MPa)	Unit elongation (%)
										79 79 79 79 53 53 53 53 48 48 48 48	1 2 3 4 1 2 3 4 1 2 3 4	326 385 401 387 355 396 396 404 361 393 395 373	267 338 356 357 303 343 349 371 305 342 350 332	12.4 9 9.8 5.6 12.9 10.8 9.5 5.7 11.6 11.1 8.85 6.8	129 129 129 129 151 151 151 151 152 152 152 152	1 2 3 4 1 2 3 4 1 2 3 4	330.5 351.5 369 387.5 284 349 380.5 378 364.5 386 351 382	270.5 296.5 316 352.5 269 302 334.5 365.5 311.5 349 320 347	11 5 11 6 4 10 10 4 10 6 3 6

Notice under these high magnesium and copper level, obtain excellent strength level and good unit elongation.

Described the preferred embodiments of the invention above now, 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 1～3%;

   Cu: about 0.05～0.5%;

   Si: less than about 1%.
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, the concentration of wherein said magnesium is about 1.7～2.3%.
10. 10. aluminium alloy according to Claim 8, the concentration of wherein said copper is about 0.25～0.3%.
11. 11. according to the aluminium alloy of claim 10, the concentration of wherein said copper is about 0.27～0.28%.
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 1～3%;

    Cu: about 0.05～0.5%;

    Si: less than about 1%.
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, the concentration of wherein said magnesium is about 1.8～2.2%.
19. 19. according to the shaped casting of claim 14, the concentration of wherein said copper is about 0.25～0.3%.
20. 20. according to the shaped casting of claim 14, the concentration of wherein said copper is about 0.27～0.28%.
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 1～3%;

    Cu: about 0.05～0.5%;

    Si: less than about 1%;

    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, the concentration of wherein said magnesium is about 1.8～2.2%.
26. 26. according to the method for claim 21, the concentration of wherein said copper is about 0.25～0.3%.
27. 27. according to the method for claim 26, the concentration of wherein said copper is about 0.27～0.28%.

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