CN1602368A - Aluminum-silicon alloys having improved mechanical properties - Google Patents

Abstract

The invention relates to a heat treatment method for articles composed of substantially Al-Si alloys that contain a eutectic phase, and to articles that consist of these alloys. In order to improve the ductility of the material or to increase the elongation after fracture, an annealing process is carried out in the form of shock annealing, said process comprising the following steps: rapidly heating the material to an annealing temperature of from 400 to 555 DEG C, maintaining it at this temperature for a period of not more than 14.8 minutes, force-cooling it, and then aging the article. The inventive article comprises spheroidized silicon precipitations in the eutectic phase portion with an average plane of section ASi of less than 4 mu m2 and/or an average distance between the silicon particles lambda Si of less than 4 mu m and/or an average spheroidization density xi Si of greater than 10.

Description

Aluminium-silicon-alloy that mechanical property is improved

The present invention relates to a kind of method that is used to improve aluminium-silicon-alloy mechanical performance.In particular, the present invention relates to a kind of heat treating method that improves object materials ductility, this object is made of cast alloys that has the eutectic phase component or plastic metal, it preferably contains modified (veredelten) or purified aluminium-element silicon, other alloying elements and/or impurity element are also randomly arranged, and this object then carries out the timeliness effect after anneal.

The invention still further relates to a kind of object, this object is to be made of the aluminium-silicon that has the eutectic phase component-alloy, it preferably has at least a modified element (Veredelungselement), randomly also contain magnesium and other alloys and/or impurity element, eutectic phase component wherein mainly is made of α-Al matrix and silicon precipitation.

Aluminium and silicon form a kind of simple eutectic system, and wherein, Si concentration is that eutectoid point appears when being 577 ℃ in 12.5 weight % and temperature.

By addition element magnesium and through thermal treatment and formed Mg ₂The Si precipitation can significantly improve the intensity of material, and when magnesium was about 550 ℃ in temperature, the maximum amount that can be dissolved in α-Al matrix was 0.47 weight %.

Can solidify to eutectic residual melt by cooling Al-Si-Mg melt, wherein silicon is with flaky thick form precipitation.Prior art for a long time is to mix sodium or strontium in this alloy, stops the growth of silicon crystal when solidifying thus, is referred to as modifiedly or refining, can improve mechanical property, particularly extension at break unlimitedly.

Basically can influence the mechanical property of aluminium alloy work in-process or object by heat treating method, by European standard EN515 definition as-heat-treated condition.According to standard, in steady state letter F=production status, T=is heat treated.The numerical table that each as-heat-treated condition is arranged after by tee shows.

In addition, below represent the following as-heat-treated condition of material with dummy suffix notation in the explanation:

F is a production status

T5 is from the quenching of production temperature and carries out the thermal life effect

T6 is liquation annealing and carries out the thermal life effect

T6x is according to thermal treatment of the present invention

T4x is according to thermal treatment of the present invention

When using the object that constitutes by the Al-Si alloy for being fit to market demand or industry, material property is important on the one hand, but production cost or economic conditions also are important on the other hand, because anneal under high temperature more for a long time, and essential during long term annealing to pass through the indispensable aligning process (Nacchrichtvorg  nge) that so-called gravity creep carries out be expensive.

Basically can confirm that the Al-Si alloy of F state has little strength of materials value R mostly _pWith higher extension at break coefficient A.

At as-heat-treated condition T5, i.e. the quenching of production temperature and carry out the thermal life effect is for example in the time of 155 ℃ to 190 ℃, during 1 to 12 hour, though reach the intensity level R of sample _pHigher, but extension at break coefficient A is lower.

The as-heat-treated condition of corresponding T6, promptly for example liquation carries out the thermal life effect subsequently 540 ℃ of annealing temperatures 12 hours, and F compares with state, and under the situation that the ductility of the extension at break of sample or material equates substantially, but the intensity of material improves greatly.For example, the liquation annealing time is long, and the magnesium atom in the material is advantageously spread, and therefore, after object quenching and thermal life are used, forms the Mg that distributes very evenly in α-Al matrix ₂The Si precipitation, this precipitation improves the strength of materials fatefully.

But, during high temperature liquation is carried out long term annealing and handle the shortcoming that exists, as mentioned above, i.e. Bu Fen gravitational creep and expensive temperature-time degree of treatment.Therefore, from economically, many-sided consideration on the maximum intensity that reaches material and the good ductility is not selected T6, and is selected the treated state T5 of object.Randomly must compensate the low strength of materials that determines because of T5 by the structure that changes member.

At this situation, the invention provides a kind of novel, economic heat treating method, this method can significantly improve the ductility of material, compare with T6, the strength of materials is not had big interference, perhaps compare, obtain showing the higher ductility and the higher strength of materials with T5.

In addition, the purpose of this invention is to provide a kind of microtexture that begins the object of the favourable mechanical property of materials of having of described class.

The purpose of present method is achieved in that promptly with impact type annealing carries out the liquation anneal, comprising: being heated rapidly to 400-555 ℃ annealing temperature, is 14.8 minutes in the soaking time the longest of this temperature, forces to be cooled to room temperature basically then.

Advantage of the present invention mainly is, adopts simple high temperature-short annealing to reach the ductility value of object maximum.In addition, so-called impact type anneal makes the deformation of member or deformation of body reduce so randomly not need self aligning up to not taking place.Anneal also has higher economic value rapidly, and can for example by continuous furnace, incorporate in the production process with plain mode.At least can regulate the strength of materials by a kind of adjusting process of thermal life effect subsequently.Be less than 6.8 minutes if can be advantageously provided the hold-time of impact type anneal, preferred 1.7 to randomly maximum 5 minutes, then improves ductility to greatest extent under the dominant situation of the quantity of Al-Si alloy.

Carry out the thermal life effect of object after the impact type annealing, being about to it, to place 1-14 hour under 150-200 ℃ of temperature be favourable.

If impact type annealing back also is favourable to material technology then carrying out the timeliness effect of object under the room temperature with the cold ageing effect substantially.

Another object of the present invention is such realization, though the nodularization of the silicon of eutectic phase component precipitation, its average cross section A _SiLess than 4 μ m ²

Below the formula in cross section is calculated in expression,

$A_{\mathrm{Si}}=\frac{1}{n}\underset{k=1}{\overset{n}{\mathrm{\&Sigma;}}}A\&le;4\mathrm{\&mu;}{\mathrm{<figure-callout\; id="2"\; label="m"\; filenames="A0282178600121.png,A0282178600122.png"\; state="\{\{state\}\}">m</figure-callout>}}^2$

Parametric representation wherein:

A _SiThe average area of=silicon particle (μ m ²)

The average area of the silicon particle of every photo of A=(μ m ²)

N=measures number of times

The advantage of this microtexture mainly is, because sedimentary nodularization of silicon and purifying have reduced the initial crack of material basically, and improved material ductility.In other words, nodularization and small size make brittle eutectic silicon have suitable form, fundamentally cause the higher extension at break value of material.Stress concentration when having reduced mechanical load on the Si-Al phase interface.Also find the transgranular fracture of material in the test, therefore demonstrate the highest ductility.

If the silicon of eutectic phase component precipitation is nodularization, and average cross section is less than 2 μ m ², then the high extension at break value for complete processing and material is favourable.

Pointed as R﹠D work, if be implemented as follows the present invention, promptly be defined as foursquare survey area divided by the mean free path λ between the silicon particle of the eutectic phase component of the root of the number of its contained silicon particle according to goal of the invention _SiValue less than 4 μ m, preferably less than 3 μ m, especially preferably, then when minimum peak stress, reach special uniform stress distribution in the material of load, because the spacing of small area silicon particle has mainly influenced the rheological property of material under the corresponding stressed condition less than 2 μ m.Calculate the average headway λ of silicon particle once more with following formula _Si

λ _SiThe average headway of=silicon particle

A _Square=foursquare reference plane (μ m ²)

N _SiliconThe number of=Si particulate

N=measures the number of photo

The liquation annealing of prior art is the long term annealing at 2 to 12 hours, so that the alloy compositions diffusion of sclerization is arranged, and be enriched in the mixed crystal, though also cause the side effect of nodularization silicon particle, but because annealing for a long time, these Particle Distribution are very big and coarse, and this fracture property to material is unfavorable.According to the present invention, surprisingly,, can in the short period of time of several minutes, make eutectic silicon crystal lattice nodularization, thereby obtain favourable material microstructure by impact type annealing rapidly.At this, importantly impact type annealed temperature should be high as far as possible, but should be lower than minimum fusion phase temperature, preferably low 5 to 20 ℃.

Make silicon particle carry out the growth of controlled diffusion with the prolongation annealing time, make originally favourable high nodularization density ξ this moment _SiDiminished.

Find when realizing the object of the invention, if be defined as per 100 μ m ²The average nodularization density ξ of the number of the eutectic silicon particle of nodularization _SiGreater than 10, and preferred 20, and then the ductility of Al-Si alloy object is the highest.

${\mathrm{\&xi;}}_{\mathrm{Si}}=\frac{1}{n}\underset{k=1}{\overset{n}{\mathrm{\&Sigma;}}}\frac{N_{\mathrm{Si}}}{A}\&times;100\&GreaterEqual;10$

ξ _SiThe average nodularization density of=eutectic silicon particle

N _SiliconThe number of=Si particulate

A=reference plane (μ m ²)

N=measures the number of photo

Related formula explanation as previously mentioned.

The result shows that the every kind of Al-Si alloy that contains the eutectic phase basically all can have structure of the present invention, and the object of Xing Chenging has high material ductility value thus.If be equipped with object, all be effective especially then to improving quality and improving extension at break with the thixo casting legal system.

Further specify the present invention by test result and photo below:

Fig. 1 bar graph: the mechanical value that depends on the material of as-heat-treated condition

Fig. 2 is same

The REM photo of Fig. 3 section

Fig. 4 is same

The relation of sedimentary average area of Fig. 5 Si and annealing time

Fig. 6 is same

Mean free path between Fig. 7 Si particulate

The average nodularization density of Fig. 8

Fig. 9 bar graph: the mechanical property of the material of different al-Si alloy

The numerical value of table 1 Fig. 9

Table 1

	???????????F		???????????T5		?????????T6×3		?????????????T6
									Scheme	???Rp[MPa]	??A[％]	???Rp[MPa]	?A[％]	???Rp[MPa]	??A[％]	???Rp[MPa]	????A[％]
????Alsi7Mg03	????121.7	??13.0	????167.5	??9.9	????228.5	??16.7	????259.8	????10.6
									????Alsi7Mg05	????143.9	??10.4	????175.8	??9.3	????240.2	??13.9	????311.7	????9.1
????Alsi7Mgx	????159.8	??8.3	????197.2	??6.8	????265.2	??10.1	????322.9	????7.6
									????Alsi6Mgx	????159.7	??10.2	????195.3	??7.8	????250.6	??8.9	????318.6	????6.5
????Alsi5Mgx	????154.9	??10.1	????189.6	??7.5	????240.6	??9.5	????313.6	????8.7
									????+Mn04	????157.1	??10.6	????183.7	??6.9	????252.7	??7.4	????322.7	????7.6
????+Mn08	????154.8	??9.9	????184.0	??6.6	????255.9	??6.7	????324.4	????4.9
									????AlSi5Mgxx	????211.7	??3.5	????256.4	??2.5	????242.1	??5.1	????291.6	????5.3

Fig. 1 represents the R of the sample of the test component that made by alloy A lSi7Mg0.3 with bar graph _P0.2Yield point value and extension at break value A, this alloy component prepares with thixo casting method (Thixocastingverfahren).The value of material hot treatment state T6 (12 hours 540 ℃+4 hours 160 ℃) with adopt the inventive method at 1 minute (T6 * 1) back of 540 ℃ of following impact types annealing, 3 minutes (T6 * 3) back and the T6 that obtained after (T6 * 5) in 5 minutes * compare.All sample carries out thermal life effect (4 hours) under 160 ℃.Tensile test result shows that the extension at break value of the sample after the impact type anneal is obviously higher, compares with T6, and state T6 * 3 cause A to raise about 60%.

The state value that has compared the sample of same manufacturing once more with bar graph among Fig. 2 is the R of F, T4 * 3, T5, T6 * 3 and T6 _P0.2With extension at break A.Show that more once more the extension at break value obviously raises.As can be seen from Figure 2, in order to obtain outstanding extension at break performance of the present invention, impact type annealing is after 3 minutes, cold ageing effect (T4 * 3) or the thermal life effect (T6 * 3) that can carry out material.

Fig. 3 and Fig. 4 represent the sedimentary electron scanning micrograph of Si.Note image pickup method and evaluation method:, must use suitable binary photo for can quantitative evaluation Photomicrograph (Schliffbilder).Take with scanning electronic microscope, reach 2 hours up to annealing time, the solution with 99.5% water and 0.5% hydrofluoric acid corroded abrasive disc 30 seconds in advance afterwards.Anneal after 4 hours, corrode abrasive disc with Keller solution, and with optics microscope photographing photo.All photos are with Adobe Photoshop 5.0 progressive number aftertreatments, and with picture analyzing program Leica Qwin V2.2 evaluation, wherein Zui Xiao area of detection is 0.1 μ m ²Fig. 3 shows the materials A lSi7Mg0.3 of conventional T6-annealing after 12 hours that takes with REM.Fig. 4 provides the microtexture of the material of impact type anneal after 3 minutes again.Silicon precipitation obviously nodularization (Fig. 4) after short period of time, behind the long annealing time self controlled diffusion grow (Fig. 3) be conspicuous.

Fig. 5 and Fig. 6 depend on the silicon particle average cross section A of 540 ℃ of following annealing times when representing the abrasive disc test _SiDescription according to Fig. 4 can obviously find out, the average cross section of silicon particle that with the particle size is feature is along with logarithmic time shaft increases.From the detailed description of Fig. 6, can observe the increase of the average silicon area that in initial 60 minutes, causes owing to diffusion.Depend primarily on the initial size of Si particulate in the eutectic mixture along with the silicon particle mean sizes of annealing time increase.Owing to there is the special good modified silicon that distributes with purification under described situation, accidental can shorten the time under the modified not so good situation of silicon particle (particulate is bigger when showing beginning), interior crucial average silicon area A of this time _SiReach about 4 μ m ²

The test-results of Fig. 7 represents to depend on the variation of average headway of the Si particulate of annealing time.The average headway that can obviously observe the Si inclusion increases.

At last, Fig. 8 represents to depend on the average nodularization density ξ of annealing time _SiDecline.Average nodularization density has begun rapid decline in the time of 1.7 minutes, from value ξ _Si＜10 are caused tangible ductility loss.During higher anneal temperature, just reach this value after 14 to 25 minutes, for dominant high extension at break value, density value is predetermined greater than 20.

Fig. 9 provides the elongation border of described 8 the different Al-Si alloys of forming of table 1 and the observed value of extension at break again by bar graph.The material ductility of all alloys of the present invention has all increased.

Claims (11)

1. heat treating method that is used to improve the material ductility of object, this object is made of cast alloys with eutectic phase component or plastic metal, this alloy preferably contains modified or purified aluminium-element silicon, other are also randomly arranged such as magnesium, manganese, alloying element and/or impurity elements such as iron, this object then carries out the timeliness effect after anneal, it is characterized in that, carry out anneal with impact type annealing, it comprises: be heated rapidly to 400-555 ℃ annealing temperature, be preferably at least 1.7 minutes to maximum 14.8 minutes in this following hold-time of temperature, force to be cooled to room temperature basically subsequently.

2. according to the method for claim 1, it is characterized in that the hold-time of impact type anneal, preferred time range was at least 1.7 minutes to randomly maximum 5 minutes less than 6.8 minutes.

3. according to the method for claim 1 or 2, it is characterized in that, under 150 to 200 ℃ temperature, object was carried out the thermal life effect 1-14 hour after the impact type anneal.

4. according to the method for claim 1 to 3, it is characterized in that, after the impact type annealing, under the room temperature object is being carried out the cold ageing effect basically.

5. object that forms by aluminium-silicon alloy with eutectic phase component, this alloy preferably has at least a modified element, randomly also has other such as alloying element and/or impurity elements such as magnesium, manganese, iron, this object mainly by α- _AlMatrix and silicon precipitation constitute, and it is characterized in that, the silicon precipitation in the eutectic phase component is nodularization, its average cross section A _SiLess than 4 μ m ²

$A_{\mathrm{Si}}=\frac{1}{n}\underset{k=1}{\overset{n}{\mathrm{\&Sigma;}}}A\&le;4{\mathrm{\&mu;m}}^2$

A _SiThe average area of=silicon particle (μ m ²)

The average area of the silicon particle of every photo of A=(μ m ²)

N=measures number of times.

6. according to the object of claim 5, it is characterized in that the silicon precipitation in the eutectic phase component is nodularization, average cross section A _SiLess than 2 μ m ²

7. object that forms by aluminium-silicon alloy with eutectic phase component, this alloy preferably has at least a modified element, randomly also has other such as alloying element and/or impurity elements such as magnesium, manganese, iron, this object mainly by α- _AlMatrix and silicon precipitation constitute, and it is characterized in that, are defined as foursquare survey area divided by the mean free path λ between the silicon particle of the eutectic phase component of the root of the number of its contained silicon particle _SiValue less than 4 μ m

λ _SiThe average headway of=silicon particle

A _Square=foursquare reference plane (μ m ²)

N _SiliconThe number of=Si particulate

N=measures the number of photo.

8. according to the object of claim 7, it is characterized in that the value of mean free path is less than 3 μ m, preferably less than 2 μ m.

9. object that constitutes by the aluminium with eutectic phase component-silicon alloy, this alloy preferably has at least a modified element, randomly also has other such as alloying element and/or impurity elements such as magnesium, manganese, iron, this object mainly by α- _AlMatrix and silicon precipitation constitute, and it is characterized in that, are defined as per 100 μ m ²The average nodularization density ξ of the number of the eutectic silicon particle of nodularization _SiGreater than 10

${\mathrm{\&xi;}}_{\mathrm{Si}}=\frac{1}{n}\underset{k=1}{\overset{n}{\mathrm{\&Sigma;}}}\frac{N_{\mathrm{Si}}}{A}\&times;100\&GreaterEqual;10$

ξ _SiThe average nodularization density of=eutectic silicon particle

N _SiliconThe number of=Si particulate

A=reference plane (μ m ²)

N=measures the number of photo.

10. according to the object of claim 9, it is characterized in that the value of average nodularization density is greater than 20.

11. claim 5-10, the object according to claim 1--4 preparation is characterized in that it prepares with the thixo casting method.

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