CA2465683C - Aluminum-silicon alloys having improved mechanical properties - Google Patents
Aluminum-silicon alloys having improved mechanical properties Download PDFInfo
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- CA2465683C CA2465683C CA2465683A CA2465683A CA2465683C CA 2465683 C CA2465683 C CA 2465683C CA 2465683 A CA2465683 A CA 2465683A CA 2465683 A CA2465683 A CA 2465683A CA 2465683 C CA2465683 C CA 2465683C
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
- C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
- C22F1/04—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of aluminium or alloys based thereon
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C21/00—Alloys based on aluminium
- C22C21/02—Alloys based on aluminium with silicon as the next major constituent
- C22C21/04—Modified aluminium-silicon alloys
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
- C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
- C22F1/04—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of aluminium or alloys based thereon
- C22F1/043—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of aluminium or alloys based thereon of alloys with silicon as the next major constituent
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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 ~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 µm2 and/or an average distance between the silicon particles .lambda.Si of less than 4 µm and/or an average spheroidization density .xi.Si of greater than 10.
Description
Aluminum-Silicon Allovs Having Improved Mechanical Properties Field of the Invention The present invention relates to a method for improving the mechanical properties of aluminum-silicon alloys. More specifically, the present invention relates to a thermal-treatment process for improving the ductility of articles consisting of a cast or wrought alloy with an eutectic phase, which contains preferably refined or purified aluminum-silicon or optionally other alloys and/or impurities, said articles being subjected to an annealing treatment and subsequent aging.
Background of the Invention Further, the present invention relates to an aluminum-silicon alloy that contains at least one processing element, optionally magnesium, as well as additional alloying and/or contaminating elements with an eutectic phase consisting essentially of an a-Al matrix and silicon exudates.
With silicon, aluminum forms a simple eutectic system, the eutectic point being at a silicon concentration of 12.5%-wt and a temperature of 577°C.
By alloying magnesium, which can be dissolved in the a-AI matrix up to a content of at most 0.47%-wt at a temperatufe of 550°C, it is possible to achieve a considerable increase in the strength of the material by means of thermal treatment and the MgZSi exudates formed thereby.
When an Al-Si-Mg smelt cools, the residual smelt can harden eutectically, when silicon in it separates out in a coarse, lamellar form. For a considerable time, it has been part of the prior art that sodium or strontium be added to alloys of this kind and thereby impede the growth of the silicon crystals during hardening; this is referred to as enrichment or refinement and always results in improvement of the mechanical properties, in particular to an improvement of elongation at fracture.
The mechanical properties of semiproducts or of objects of aluminum alloys can be greatly influenced by thermal treatment methods, and the thermal-treatment states are 2~
defined in European Standard EN 515. In this Standard, the letter F stands for "production state" and T stands for "thermally treated to stable states." The particular thermal treatment state is characterized by the number that is associated with the letter T.
In the description appended below, the thermal-treatment states of the material are, indicated by the following short forms:
F - production state TS - quenched from the production temperature and thermally aged T6 - solution quenched and thermally aged T6x - thermally treated according to the present invention T4x - thermally treated according to the present invention On the one hand, the properties of the material and, on the other hand, the costs or economic factors involved in production are important for marketing or the industrial use of objects that are of Al-Si alloys, since in particular long annealing treatments at high temperatures and the straightening processes that may be necessitated by so-called gravitational creep during protracted annealing are themselves costly.
In principle, it can be said that an Al-Si alloy in State F has for the most part a low material strength Rp and a relatively high value for elongation at fracture A.
At a thermal treatment state T5, which is to say quenched from the production temperature and thermally aged, for example at 155°C to 199°C
for a period of 1 to 12 hours, higher strength values Rp will be achieved, but at a low elongation at fracture number A of the samples.
At a thermal-treatment state corresponding to T6, with solution annealing at a temperature of, for example, 540°C for a period of 12 hours and subsequent thermal aging, it is possible to achieve a significant increase in the strength of the material at an almost equally great elongation at fracture of the samples, or ductility of the material as compared to State F. The long duration of the solution annealing permits advantageous diffusion of the magnesium atoms in the material, for example, whereby after quenching 3~ ' and thermal aging of the article fine, evenly distributed Mg2Si exudates are formed in the a-Ai matrix, and these exudates result in a decisive increase in the strength of the material.
As discussed heretofore, solution annealing at high temperatures and for protracted periods entails the disadvantages of gravitational creep and costly temperature-time treatment. For reasons of economy, very frequently achieving great strength and good ductility of the material by T6 is abandoned and a treatment state T5 is selected for the article. The lesser strength that results from T5 must if necessary be compensated for by making design changes to the component in question.
Summar~of the Invention It is the objective of the present invention to create a new, cost-effective method of thermal treatment, with which the ductility of the material can be greatly increased without causing major losses of material strength as compared to T6, or with which significantly greater ductility and greater material strength can be achieved in comparison to T5.
It is also an objective of the present invention to describe a microstructure of an article of the type described in the introduction hereto, which results in advantageous mechanical properties of the material.
The objective of this method is achieved in that the solution annealing is conducted as shock annealing comprising rapid heating of the material to an annealing temperature of 400°C to 555°C, maintaining it at this temperature for a period of at most 14.8 minutes, and subsequent forced cooling, essentially to room temperature.
The advantages that are obtained are that the highest ductility values are achieved for the material by a simple high-temperature brief annealing. In addition, the so-called shock annealing causes little or no component deformation or warping of the article, so that there is no need to straighten it. The short-time annealing treatment is very economical and can be incorporated very easily into a production sequence, for example by using a continuous heating furnace. Material strength can be adjusted by an adapted thermal 4~
aging technology. With the majority of Al-Si alloys, the greatest increase will be achieved if, as can be provided for, the shock annealing is effected with a holding time of less than 6.8 minutes, preferably for a time span ranging from 1.7 up to at most 5 minutes.
If the article is thermally aged after the shock annealing, it is advantageous to do this at a temperature in the range between 150°C and 200°C, for a period ranging from 1 to 14 hours.
It can also be advantageous from the material standpoint if the aging of the article that follows shock annealing be effected as cold aging, essentially at room temperature.
The additional objective of the present invention is achieved in that the silicon exudates are spheroidized in the eutectic phase and have a cross-sectional area As;, of less than 4 ~m2.
The formula for determining the cross-sectional area is shown below, the factors being:
n AS; _ ~ ~ A 5 4 wm2 n ka, As; = average surface of the silicon particles in ~.mz A = average surface of the silicon particles per image, in p.m2 n = number of images sampled The advantages of a microstructure of this kind are essentially that crack initiation in the material caused by spheroidization of the Si exudates and by their fineness is significantly reduced and ductility of the material is improved. In other words, the spheroidization and small size result in a favourable morphology of the brittle eutectic silicon and lead to significantly higher values for the material's elongation at fracture. In the case of mechanical loading, the stress peaks on the Si-Al phase boundary surface are 5' reduced. A transcrystalline break was also found during tests, and this indicates the highest ductility of the material.
From the method standpoint, but also for high values for elongation at fracture, it can be advantageous if the silicon exudates in the eutectic phase be spheroidized and have an average cross-sectional area of less than 2~.mz.
If, as was shown during development, the solution. according to the present invention is realized in that the average free path length between the silicon particles ~,5; in the eutectic phase defined as the root of a square measured surface divided by the number of silicon particles contained within it is of as a size that is less than 4pm, preferably less than 3pm, and in particular less than 2 Vim, an especially homogeneous stress distribution at low stress peak values will be achieved in the material that is stressed, since the spacing between the small-surface silicon particles essentially effects the flow behaviour of the material in a corresponding stress state. Determination of the distance between the silicon particles ~,s;, is shown formally below.
n AQuadrat ~ 4 ~ N s;iicon wherein ~,s; = average spacing between of the silicon particles in ~m2 A Quadrat = square reference surface, in ~.m2 Ns;,;~o" = number of silicon particles n = number of images sampled Although solution annealing as in the prior art which is effected as long-time annealing for 2 to 12 hours for diffusion of the alloying components that are effective for hardening and their enrichment in the mix crystal entails spheroidization of the silicon particles as a secondary effect, the particles are very large and distributed unevenly as a result of the long annealing time; this can have a deleterious effect on the material's behaviour at fracture. It was most surprising that a eutectic silicon network can be spheroidized according to the present invention by brief shock annealing for a short time span of just a few minutes, whereby an advantageous microstructure of the material can be achieved. In this connection, it is important that the temperature for the shock annealing be a high as possible, although below the lowest smelting phase, preferably 5 to 20°C below this.
With increasing annealing times, the silicon particles are subjected to a diffusion-controlled growth, the initially favourable high spheroidization density ~s;
becoming smaller.
In one solution to the task of the present invention, the highest ductility of an article of an Al-Si alloy was found if the mean spheroidization density ~s;, defined as the number of spheroidized eutectic silicon particles per .100~m2 , has a value that is greater than 10, and preferably greater than 20.
n ~S;=n~A'x100>_ 10 ~s; = Average spheroidization density of the eutectic Si particles Nsn;~o" = Number of silicon particles A = Reference surface in ~m2 n = Number of images sampled The following is once again a formal specification of the formula.
Work has shown that essentially each AI-Si alloy that contains the eutectic can be provided with a structure according to the present invention, when the articles formed therefrom has high material-ductility values. The improvement of the goods and an improvement of elongation at fracture are particularly efficient if the article is manufactured by the thixocasting method.
Brief Description of the Drawings The present invention will be described in greater detail below on the basis of test results and drawings as appended hereto. The drawings show the following:
Background of the Invention Further, the present invention relates to an aluminum-silicon alloy that contains at least one processing element, optionally magnesium, as well as additional alloying and/or contaminating elements with an eutectic phase consisting essentially of an a-Al matrix and silicon exudates.
With silicon, aluminum forms a simple eutectic system, the eutectic point being at a silicon concentration of 12.5%-wt and a temperature of 577°C.
By alloying magnesium, which can be dissolved in the a-AI matrix up to a content of at most 0.47%-wt at a temperatufe of 550°C, it is possible to achieve a considerable increase in the strength of the material by means of thermal treatment and the MgZSi exudates formed thereby.
When an Al-Si-Mg smelt cools, the residual smelt can harden eutectically, when silicon in it separates out in a coarse, lamellar form. For a considerable time, it has been part of the prior art that sodium or strontium be added to alloys of this kind and thereby impede the growth of the silicon crystals during hardening; this is referred to as enrichment or refinement and always results in improvement of the mechanical properties, in particular to an improvement of elongation at fracture.
The mechanical properties of semiproducts or of objects of aluminum alloys can be greatly influenced by thermal treatment methods, and the thermal-treatment states are 2~
defined in European Standard EN 515. In this Standard, the letter F stands for "production state" and T stands for "thermally treated to stable states." The particular thermal treatment state is characterized by the number that is associated with the letter T.
In the description appended below, the thermal-treatment states of the material are, indicated by the following short forms:
F - production state TS - quenched from the production temperature and thermally aged T6 - solution quenched and thermally aged T6x - thermally treated according to the present invention T4x - thermally treated according to the present invention On the one hand, the properties of the material and, on the other hand, the costs or economic factors involved in production are important for marketing or the industrial use of objects that are of Al-Si alloys, since in particular long annealing treatments at high temperatures and the straightening processes that may be necessitated by so-called gravitational creep during protracted annealing are themselves costly.
In principle, it can be said that an Al-Si alloy in State F has for the most part a low material strength Rp and a relatively high value for elongation at fracture A.
At a thermal treatment state T5, which is to say quenched from the production temperature and thermally aged, for example at 155°C to 199°C
for a period of 1 to 12 hours, higher strength values Rp will be achieved, but at a low elongation at fracture number A of the samples.
At a thermal-treatment state corresponding to T6, with solution annealing at a temperature of, for example, 540°C for a period of 12 hours and subsequent thermal aging, it is possible to achieve a significant increase in the strength of the material at an almost equally great elongation at fracture of the samples, or ductility of the material as compared to State F. The long duration of the solution annealing permits advantageous diffusion of the magnesium atoms in the material, for example, whereby after quenching 3~ ' and thermal aging of the article fine, evenly distributed Mg2Si exudates are formed in the a-Ai matrix, and these exudates result in a decisive increase in the strength of the material.
As discussed heretofore, solution annealing at high temperatures and for protracted periods entails the disadvantages of gravitational creep and costly temperature-time treatment. For reasons of economy, very frequently achieving great strength and good ductility of the material by T6 is abandoned and a treatment state T5 is selected for the article. The lesser strength that results from T5 must if necessary be compensated for by making design changes to the component in question.
Summar~of the Invention It is the objective of the present invention to create a new, cost-effective method of thermal treatment, with which the ductility of the material can be greatly increased without causing major losses of material strength as compared to T6, or with which significantly greater ductility and greater material strength can be achieved in comparison to T5.
It is also an objective of the present invention to describe a microstructure of an article of the type described in the introduction hereto, which results in advantageous mechanical properties of the material.
The objective of this method is achieved in that the solution annealing is conducted as shock annealing comprising rapid heating of the material to an annealing temperature of 400°C to 555°C, maintaining it at this temperature for a period of at most 14.8 minutes, and subsequent forced cooling, essentially to room temperature.
The advantages that are obtained are that the highest ductility values are achieved for the material by a simple high-temperature brief annealing. In addition, the so-called shock annealing causes little or no component deformation or warping of the article, so that there is no need to straighten it. The short-time annealing treatment is very economical and can be incorporated very easily into a production sequence, for example by using a continuous heating furnace. Material strength can be adjusted by an adapted thermal 4~
aging technology. With the majority of Al-Si alloys, the greatest increase will be achieved if, as can be provided for, the shock annealing is effected with a holding time of less than 6.8 minutes, preferably for a time span ranging from 1.7 up to at most 5 minutes.
If the article is thermally aged after the shock annealing, it is advantageous to do this at a temperature in the range between 150°C and 200°C, for a period ranging from 1 to 14 hours.
It can also be advantageous from the material standpoint if the aging of the article that follows shock annealing be effected as cold aging, essentially at room temperature.
The additional objective of the present invention is achieved in that the silicon exudates are spheroidized in the eutectic phase and have a cross-sectional area As;, of less than 4 ~m2.
The formula for determining the cross-sectional area is shown below, the factors being:
n AS; _ ~ ~ A 5 4 wm2 n ka, As; = average surface of the silicon particles in ~.mz A = average surface of the silicon particles per image, in p.m2 n = number of images sampled The advantages of a microstructure of this kind are essentially that crack initiation in the material caused by spheroidization of the Si exudates and by their fineness is significantly reduced and ductility of the material is improved. In other words, the spheroidization and small size result in a favourable morphology of the brittle eutectic silicon and lead to significantly higher values for the material's elongation at fracture. In the case of mechanical loading, the stress peaks on the Si-Al phase boundary surface are 5' reduced. A transcrystalline break was also found during tests, and this indicates the highest ductility of the material.
From the method standpoint, but also for high values for elongation at fracture, it can be advantageous if the silicon exudates in the eutectic phase be spheroidized and have an average cross-sectional area of less than 2~.mz.
If, as was shown during development, the solution. according to the present invention is realized in that the average free path length between the silicon particles ~,5; in the eutectic phase defined as the root of a square measured surface divided by the number of silicon particles contained within it is of as a size that is less than 4pm, preferably less than 3pm, and in particular less than 2 Vim, an especially homogeneous stress distribution at low stress peak values will be achieved in the material that is stressed, since the spacing between the small-surface silicon particles essentially effects the flow behaviour of the material in a corresponding stress state. Determination of the distance between the silicon particles ~,s;, is shown formally below.
n AQuadrat ~ 4 ~ N s;iicon wherein ~,s; = average spacing between of the silicon particles in ~m2 A Quadrat = square reference surface, in ~.m2 Ns;,;~o" = number of silicon particles n = number of images sampled Although solution annealing as in the prior art which is effected as long-time annealing for 2 to 12 hours for diffusion of the alloying components that are effective for hardening and their enrichment in the mix crystal entails spheroidization of the silicon particles as a secondary effect, the particles are very large and distributed unevenly as a result of the long annealing time; this can have a deleterious effect on the material's behaviour at fracture. It was most surprising that a eutectic silicon network can be spheroidized according to the present invention by brief shock annealing for a short time span of just a few minutes, whereby an advantageous microstructure of the material can be achieved. In this connection, it is important that the temperature for the shock annealing be a high as possible, although below the lowest smelting phase, preferably 5 to 20°C below this.
With increasing annealing times, the silicon particles are subjected to a diffusion-controlled growth, the initially favourable high spheroidization density ~s;
becoming smaller.
In one solution to the task of the present invention, the highest ductility of an article of an Al-Si alloy was found if the mean spheroidization density ~s;, defined as the number of spheroidized eutectic silicon particles per .100~m2 , has a value that is greater than 10, and preferably greater than 20.
n ~S;=n~A'x100>_ 10 ~s; = Average spheroidization density of the eutectic Si particles Nsn;~o" = Number of silicon particles A = Reference surface in ~m2 n = Number of images sampled The following is once again a formal specification of the formula.
Work has shown that essentially each AI-Si alloy that contains the eutectic can be provided with a structure according to the present invention, when the articles formed therefrom has high material-ductility values. The improvement of the goods and an improvement of elongation at fracture are particularly efficient if the article is manufactured by the thixocasting method.
Brief Description of the Drawings The present invention will be described in greater detail below on the basis of test results and drawings as appended hereto. The drawings show the following:
7 .
Figure 1: Bar chart showing mechanical values for material as a function of thermal treatment state;
Figure As in Figure 1 2:
Figure REM image of a cut 3:
Figure As in Figure 3 4:
Figure Mean surface of the Si exudates 5:
Figure As in Figure 5 6:
Figure Mean free path length between 7: the Si particles Figure Mean spheroidization density 8:
Figure 9: Bar chart showing material mechanical properties of various Al-Si alloys Table 1: Numerical values for Figure 9.
Detailed Description of the Preferred Embodiments In Figure l, a bar chart shows the Rpo.2 limiting values and the values for elongation at fracture A of samples manufactured from a test component produced from an AlSi7Mg0.3 alloy, said component having been produced by the thixocasting method.
The values for thermal treatment state T6 (12 hours 540°C + 4 hours 160°C) of the material are compared to those that were achieved with the T6x method according to the present invention after shock annealing far 1 minute (T6x1), after 3 minutes (T6x3) and after 5 minutes (T6x5) at a temperature of 540°C. All the samples were hot-aged (4 hours) at a temperature of 160°C. The results of the tensile test show that the samples display significantly higher values for elongation at fracture after shock annealing, the T6x3 effecting an increase of A by approximately 60% as compared to T6.
In Figure 2, using identically produced samples, the state values F, T4x3, T5, T6x3 and T6 are compared in a bar chart with respect to Rp o,2 and elongation at fracture A. When compared, they display marked increases of the values for elongation at fracture. As can be seen from Figure 2, the material can be aged cold (T4x3) or hot (T6x3) after shock annealing for 3 minutes in order to obtain the superior elongation at fracture characteristics according to the present invention.
Figure 3 and Figure 4 show raster electron microscope images of Si exudates.
With respect to the imaging and evaluation method, it must be noted that it is essential to have binary images available in order to permit quantitative evaluation. The images were captured with a raster electron microscope for an annealing period of 2 hours inclusive, after which the cut was etched for 30 seconds using a solution of 99.5% water and 0.5%
liquid acid. After annealing for 4 hours, the cut was etched with Keller solution and the images could be captured by optical microscope. All the images were processed digitally using Adobe Photoshop 5, and evaluated with the Leica QWin V2.2 image analysis software; the minimal detection surface amounted to 0.1 pmt. Figure 3 shows the AlSi7Mg0.3 after a normal T6 annealing time of 12 house , using an REM
image.
Figure 4 shows the microstructure of the same material after shock annealing for three minutes. It is clear that even after a very short time there is spheroidization of the silicon exudates (Figure 4) and the diffusion-controlled growth of these can be seen after long annealing times (Figure 3).
Figure 5 and Figure 6 show the mean cut surface As; of the silicon particles during cut testing as a function of the annealing time at 540°C. The increase of average cross-sectional area of the silicon particles, which characterizes the size of the particles, can be clearly seen from the details of Figure 4 with the logarithmic time axis. The increase of the average silicon surface within the first 60 minutes, which is governed by diffusion, can be clearly seen from Figure 6. The average size of the silicon particles, which increases with annealing time, is to a large extent dependent on the initial size of the silicon particles in the eutectic. Since an extremely well refined and finely divided silicon is present in this particular case, in some cases that involve silicon particles that has not been refined so well which is to say with initially larger silicon particles the time in which a critical average silicon surface As; of approximately 4p.m2 can be achieved can be shorter.
Figure 1: Bar chart showing mechanical values for material as a function of thermal treatment state;
Figure As in Figure 1 2:
Figure REM image of a cut 3:
Figure As in Figure 3 4:
Figure Mean surface of the Si exudates 5:
Figure As in Figure 5 6:
Figure Mean free path length between 7: the Si particles Figure Mean spheroidization density 8:
Figure 9: Bar chart showing material mechanical properties of various Al-Si alloys Table 1: Numerical values for Figure 9.
Detailed Description of the Preferred Embodiments In Figure l, a bar chart shows the Rpo.2 limiting values and the values for elongation at fracture A of samples manufactured from a test component produced from an AlSi7Mg0.3 alloy, said component having been produced by the thixocasting method.
The values for thermal treatment state T6 (12 hours 540°C + 4 hours 160°C) of the material are compared to those that were achieved with the T6x method according to the present invention after shock annealing far 1 minute (T6x1), after 3 minutes (T6x3) and after 5 minutes (T6x5) at a temperature of 540°C. All the samples were hot-aged (4 hours) at a temperature of 160°C. The results of the tensile test show that the samples display significantly higher values for elongation at fracture after shock annealing, the T6x3 effecting an increase of A by approximately 60% as compared to T6.
In Figure 2, using identically produced samples, the state values F, T4x3, T5, T6x3 and T6 are compared in a bar chart with respect to Rp o,2 and elongation at fracture A. When compared, they display marked increases of the values for elongation at fracture. As can be seen from Figure 2, the material can be aged cold (T4x3) or hot (T6x3) after shock annealing for 3 minutes in order to obtain the superior elongation at fracture characteristics according to the present invention.
Figure 3 and Figure 4 show raster electron microscope images of Si exudates.
With respect to the imaging and evaluation method, it must be noted that it is essential to have binary images available in order to permit quantitative evaluation. The images were captured with a raster electron microscope for an annealing period of 2 hours inclusive, after which the cut was etched for 30 seconds using a solution of 99.5% water and 0.5%
liquid acid. After annealing for 4 hours, the cut was etched with Keller solution and the images could be captured by optical microscope. All the images were processed digitally using Adobe Photoshop 5, and evaluated with the Leica QWin V2.2 image analysis software; the minimal detection surface amounted to 0.1 pmt. Figure 3 shows the AlSi7Mg0.3 after a normal T6 annealing time of 12 house , using an REM
image.
Figure 4 shows the microstructure of the same material after shock annealing for three minutes. It is clear that even after a very short time there is spheroidization of the silicon exudates (Figure 4) and the diffusion-controlled growth of these can be seen after long annealing times (Figure 3).
Figure 5 and Figure 6 show the mean cut surface As; of the silicon particles during cut testing as a function of the annealing time at 540°C. The increase of average cross-sectional area of the silicon particles, which characterizes the size of the particles, can be clearly seen from the details of Figure 4 with the logarithmic time axis. The increase of the average silicon surface within the first 60 minutes, which is governed by diffusion, can be clearly seen from Figure 6. The average size of the silicon particles, which increases with annealing time, is to a large extent dependent on the initial size of the silicon particles in the eutectic. Since an extremely well refined and finely divided silicon is present in this particular case, in some cases that involve silicon particles that has not been refined so well which is to say with initially larger silicon particles the time in which a critical average silicon surface As; of approximately 4p.m2 can be achieved can be shorter.
The change of the average distance between the silicon particles as a function of annealing time is shown in Figure 7, using test results. The increase in the average spacing of the silicon inclusions can be clearly seen.
Finally, Figure 8 shows the decrease of the average spheroidization density ~;, is shown as a function of annealing time. The sharp decrease of the average spheroidization density begins as soon as at 1.7 minutes and drops from a value of <10 for ~s;
to a pronounced loss of ductility. At higher annealing temperatures, the value can be reached after 14 to 25 minutes, when a density value of greater than 20 has to be provided for a much higher value for elongation at fracture.
The bar chart at Figure 9 shows the measured values for limit of elongation and elongation at fracture that follow from Table 1, for eight different Al-Si alloys. In all of these alloys, an increase in the ductility of the material is achieved according to the present invention.
Finally, Figure 8 shows the decrease of the average spheroidization density ~;, is shown as a function of annealing time. The sharp decrease of the average spheroidization density begins as soon as at 1.7 minutes and drops from a value of <10 for ~s;
to a pronounced loss of ductility. At higher annealing temperatures, the value can be reached after 14 to 25 minutes, when a density value of greater than 20 has to be provided for a much higher value for elongation at fracture.
The bar chart at Figure 9 shows the measured values for limit of elongation and elongation at fracture that follow from Table 1, for eight different Al-Si alloys. In all of these alloys, an increase in the ductility of the material is achieved according to the present invention.
Claims (11)
1. A thermal-treatment process for improving the ductility of articles consisting of a cast or wrought alloy with a eutectic phase, which contains preferably refined or purified aluminum-silicon or optionally other alloys and/or impurities, said articles being subjected to an annealing treatment and subsequent aging, characterized in that the annealing is effected as shock annealing comprising rapid heating of the material to an annealing temperature of 400°C to 555°C, maintaining it at this temperature for a holding period from preferably at least 1.7 minutes to at most 14.8 minutes, and subsequently force cooling it to essentially room temperature.
2. The process as defined in claim 1, characterized in that the shock annealing is effected with a holding time of less than 6.8 minutes, preferably with a time span from at least 1.7 minutes to a maximum of 5 minutes if necessary.
3. The process as defined in any one of claims 1 or 2, characterized in that the aging of the article, which follows the shock annealing, is effected as thermal aging at a temperature in the range between 150°C and 200°C with a period from 1 to 14 hours.
4. The process as defined in any one of claims 1 to 3, characterized in that the aging of the article that follows the shock annealing is effected as cold aging at essentially room temperature.
5. An article of an aluminum-silicon alloy, optionally containing other alloys and/or impurities such as magnesium, manganese, iron and the like, with a eutectic phase, consisting essentially of an .alpha.Al matrix and silicon exudates, characterized in that the silicon exudates are spheroidized in the eutectic phase and have an average cross-sectional area A Si of less than 4µm2.
A Si = average surface of the silicon particles in µm2 A = average surface of the silicon particles per image, in µm2 n = number of images sampled
A Si = average surface of the silicon particles in µm2 A = average surface of the silicon particles per image, in µm2 n = number of images sampled
6. The article as defined in claim 5, characterized in that the silicon exudates in the eutectic phase are spheroidized and have an average cross-sectional area of less than 2µm2.
7. An article of an aluminum-silicon alloy, optionally containing other alloys and/or impurities such as magnesium, manganese, iron and the like, with a eutectic phase, consisting essentially of an .alpha.Al matrix and silicon exudates, characterized in that the average free path length between the silicon particles .lambda.Si in the eutectic phase defined as the root of a square measured surface divided by the number of silicon particles contained within it is of as a size that is less than 4um.
wherein .lambda. Si; = average spacing between of the silicon particles in µ2 A Quadrat = square reference surface, in µm2 N Silicon = number of silicon particles n = number of images sampled
wherein .lambda. Si; = average spacing between of the silicon particles in µ2 A Quadrat = square reference surface, in µm2 N Silicon = number of silicon particles n = number of images sampled
8. The article as defined in claim 7, characterized in that the average free path lengths are of a size that is less than 3µm, and preferably less than 2µm.
9. An article of an aluminum-silicon alloy, if necessary with an enriching element and optionally with other alloys and/or impurities such as magnesium, manganese, iron and the like, with a eutectic phase, consisting essentially of an .alpha.Al matrix and silicon exudates, characterized in that the average spheroidization density .zeta.Si, defined as the number of spheroidized eutectic particles per 100µm2 is greater than 10.
.zeta.Si = Mean spheroidization density of the eutectic Si particles N Silicon = Number of silicon particles A = Reference surface in µm2 n = Number of images sampled
.zeta.Si = Mean spheroidization density of the eutectic Si particles N Silicon = Number of silicon particles A = Reference surface in µm2 n = Number of images sampled
10. The article as defined in claim 9, characterized in that the average spheroidization density is greater than 20.
11. The article as defined in any one of claims 5 to 10, produced according to the method set out in any one of claims 1 to 4, characterized in that this is manufactured by the thixocasting method.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| AT0173301A AT411269B (en) | 2001-11-05 | 2001-11-05 | ALUMINUM-SILICON ALLOYS WITH IMPROVED MECHANICAL PROPERTIES |
| ATA1733/2001 | 2001-11-05 | ||
| PCT/AT2002/000309 WO2003040423A1 (en) | 2001-11-05 | 2002-11-05 | Aluminum-silicon alloys having improved mechanical properties |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2465683A1 CA2465683A1 (en) | 2003-05-15 |
| CA2465683C true CA2465683C (en) | 2011-01-18 |
Family
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Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA2465683A Expired - Fee Related CA2465683C (en) | 2001-11-05 | 2002-11-05 | Aluminum-silicon alloys having improved mechanical properties |
Country Status (15)
| Country | Link |
|---|---|
| US (2) | US20050000608A1 (en) |
| EP (1) | EP1442150B1 (en) |
| JP (1) | JP2005508446A (en) |
| KR (1) | KR20050043748A (en) |
| CN (1) | CN100366782C (en) |
| AT (2) | AT411269B (en) |
| CA (1) | CA2465683C (en) |
| DE (1) | DE50209192D1 (en) |
| DK (1) | DK1442150T3 (en) |
| ES (1) | ES2280578T3 (en) |
| HK (1) | HK1071171A1 (en) |
| HU (1) | HUP0401962A2 (en) |
| PT (1) | PT1442150E (en) |
| SI (1) | SI1442150T1 (en) |
| WO (1) | WO2003040423A1 (en) |
Families Citing this family (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US8950468B2 (en) | 2007-05-11 | 2015-02-10 | The Boeing Company | Cooling system for aerospace vehicle components |
| DE102008024524A1 (en) * | 2008-05-21 | 2009-11-26 | Bdw Technologies Gmbh | Method and plant for producing a cast component |
| DE102011105447B4 (en) * | 2011-06-24 | 2019-08-22 | Audi Ag | Process for the production of aluminum die-cast parts |
| CN107586939A (en) * | 2017-09-13 | 2018-01-16 | 中信戴卡股份有限公司 | A kind of heat treatment method for aluminium alloy casting rotation wheel |
| CN109706411A (en) * | 2019-02-18 | 2019-05-03 | 东莞宏幸智能科技有限公司 | A kind of solid smelting furnace of aluminum alloy spare part production |
| CN115961223A (en) * | 2022-12-19 | 2023-04-14 | 湖南中创空天新材料股份有限公司 | Method for removing residual stress |
Family Cites Families (10)
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|---|---|---|---|---|
| JPH0747807B2 (en) * | 1992-03-17 | 1995-05-24 | スカイアルミニウム株式会社 | Method for producing rolled aluminum alloy plate for forming |
| JPH07166285A (en) * | 1993-06-08 | 1995-06-27 | Shinko Alcoa Yuso Kizai Kk | Hardened al alloy sheet by baking and production thereof |
| JPH11613A (en) * | 1997-06-13 | 1999-01-06 | Kawasaki Steel Corp | Manufacture of aluminum alloy plate with superior molding properties and coat baking/curing properties |
| US6040059A (en) * | 1997-11-18 | 2000-03-21 | Luk Gmbh & Co. | Component made of an aluminium silicon cast alloy |
| US5985349A (en) * | 1998-11-12 | 1999-11-16 | Kraft Foods, Inc. | Method for manufacture of grated cheese |
| DE19901508A1 (en) * | 1999-01-16 | 2000-08-17 | Bayerische Motoren Werke Ag | Process for the production of castings from aluminum alloys |
| DE19925666C1 (en) * | 1999-06-04 | 2000-09-28 | Vaw Motor Gmbh | Cast cylinder head and engine block component is made of an aluminum-silicon alloy containing aluminum-nickel, aluminum-copper, aluminum-manganese and aluminum-iron and their mixed phases |
| JP2001316747A (en) * | 1999-08-31 | 2001-11-16 | Asahi Tec Corp | NON-Cu CAST Al ALLOY AND HEAT TREATING METHOD THEREFOR |
| JP3857503B2 (en) * | 2000-07-26 | 2006-12-13 | 大同メタル工業株式会社 | Aluminum bearing alloy |
| DE60336534D1 (en) * | 2002-01-11 | 2011-05-12 | Gen Hospital Corp | Device for OCT image acquisition with axial line focus for improved resolution and depth of field |
-
2001
- 2001-11-05 AT AT0173301A patent/AT411269B/en not_active IP Right Cessation
-
2002
- 2002-11-05 JP JP2003542667A patent/JP2005508446A/en active Pending
- 2002-11-05 HU HU0401962A patent/HUP0401962A2/en unknown
- 2002-11-05 CA CA2465683A patent/CA2465683C/en not_active Expired - Fee Related
- 2002-11-05 EP EP02774155A patent/EP1442150B1/en not_active Expired - Lifetime
- 2002-11-05 CN CNB028217861A patent/CN100366782C/en not_active Expired - Fee Related
- 2002-11-05 SI SI200230502T patent/SI1442150T1/en unknown
- 2002-11-05 DE DE50209192T patent/DE50209192D1/en not_active Expired - Lifetime
- 2002-11-05 ES ES02774155T patent/ES2280578T3/en not_active Expired - Lifetime
- 2002-11-05 KR KR1020047006793A patent/KR20050043748A/en active Search and Examination
- 2002-11-05 AT AT02774155T patent/ATE350507T1/en active
- 2002-11-05 DK DK02774155T patent/DK1442150T3/en active
- 2002-11-05 WO PCT/AT2002/000309 patent/WO2003040423A1/en active Application Filing
- 2002-11-05 PT PT02774155T patent/PT1442150E/en unknown
-
2004
- 2004-05-04 US US10/837,665 patent/US20050000608A1/en not_active Abandoned
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2005
- 2005-02-04 HK HK05100996A patent/HK1071171A1/en not_active IP Right Cessation
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2010
- 2010-04-12 US US12/758,381 patent/US20100193084A1/en not_active Abandoned
Also Published As
| Publication number | Publication date |
|---|---|
| DE50209192D1 (en) | 2007-02-15 |
| PT1442150E (en) | 2007-04-30 |
| CN100366782C (en) | 2008-02-06 |
| JP2005508446A (en) | 2005-03-31 |
| AT411269B (en) | 2003-11-25 |
| DK1442150T3 (en) | 2007-05-14 |
| EP1442150A1 (en) | 2004-08-04 |
| US20050000608A1 (en) | 2005-01-06 |
| SI1442150T1 (en) | 2007-06-30 |
| HK1071171A1 (en) | 2005-07-08 |
| WO2003040423A1 (en) | 2003-05-15 |
| US20100193084A1 (en) | 2010-08-05 |
| KR20050043748A (en) | 2005-05-11 |
| ATA17332001A (en) | 2003-04-15 |
| ES2280578T3 (en) | 2007-09-16 |
| HUP0401962A2 (en) | 2005-01-28 |
| EP1442150B1 (en) | 2007-01-03 |
| CN1602368A (en) | 2005-03-30 |
| ATE350507T1 (en) | 2007-01-15 |
| CA2465683A1 (en) | 2003-05-15 |
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