CN117904497A - High-strength and high-toughness cast aluminum alloy with low copper content and preparation method thereof - Google Patents
High-strength and high-toughness cast aluminum alloy with low copper content and preparation method thereof Download PDFInfo
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- 229910000838 Al alloy Inorganic materials 0.000 title claims abstract description 129
- 239000010949 copper Substances 0.000 title claims abstract description 48
- 229910052802 copper Inorganic materials 0.000 title claims abstract description 33
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 title claims abstract description 27
- 238000002360 preparation method Methods 0.000 title abstract description 16
- 229910045601 alloy Inorganic materials 0.000 claims abstract description 94
- 239000000956 alloy Substances 0.000 claims abstract description 94
- 230000032683 aging Effects 0.000 claims abstract description 47
- 238000010438 heat treatment Methods 0.000 claims abstract description 38
- 239000006104 solid solution Substances 0.000 claims abstract description 38
- 239000000126 substance Substances 0.000 claims abstract description 7
- 229910052719 titanium Inorganic materials 0.000 claims abstract description 4
- 229910052725 zinc Inorganic materials 0.000 claims abstract description 3
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 40
- 238000010791 quenching Methods 0.000 claims description 30
- 230000000171 quenching effect Effects 0.000 claims description 30
- 238000007670 refining Methods 0.000 claims description 27
- 238000000034 method Methods 0.000 claims description 22
- 229910052786 argon Inorganic materials 0.000 claims description 20
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 20
- 239000000243 solution Substances 0.000 claims description 18
- 238000007528 sand casting Methods 0.000 claims description 15
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 12
- 229910052782 aluminium Inorganic materials 0.000 claims description 12
- 229910018134 Al-Mg Inorganic materials 0.000 claims description 10
- 229910018467 Al—Mg Inorganic materials 0.000 claims description 10
- 238000007664 blowing Methods 0.000 claims description 10
- 239000000155 melt Substances 0.000 claims description 10
- 239000003607 modifier Substances 0.000 claims description 10
- 239000002893 slag Substances 0.000 claims description 10
- 238000004519 manufacturing process Methods 0.000 claims description 9
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- 229910018565 CuAl Inorganic materials 0.000 abstract description 3
- 238000001556 precipitation Methods 0.000 abstract description 3
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- 229910018520 Al—Si Inorganic materials 0.000 abstract description 2
- 230000000052 comparative effect Effects 0.000 description 34
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- 239000010936 titanium Substances 0.000 description 10
- 239000011159 matrix material Substances 0.000 description 8
- 238000005728 strengthening Methods 0.000 description 6
- 229910021364 Al-Si alloy Inorganic materials 0.000 description 5
- 229910019086 Mg-Cu Inorganic materials 0.000 description 4
- 229910019752 Mg2Si Inorganic materials 0.000 description 4
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 4
- 238000003776 cleavage reaction Methods 0.000 description 4
- 239000013078 crystal Substances 0.000 description 4
- 229910018566 Al—Si—Mg Inorganic materials 0.000 description 3
- 229910000676 Si alloy Inorganic materials 0.000 description 3
- 230000005496 eutectics Effects 0.000 description 3
- 230000010287 polarization Effects 0.000 description 3
- 230000007017 scission Effects 0.000 description 3
- 229910052710 silicon Inorganic materials 0.000 description 3
- 229910018182 Al—Cu Inorganic materials 0.000 description 2
- 229910019018 Mg 2 Si Inorganic materials 0.000 description 2
- 239000000654 additive Substances 0.000 description 2
- 230000000996 additive effect Effects 0.000 description 2
- 238000005275 alloying Methods 0.000 description 2
- CSDREXVUYHZDNP-UHFFFAOYSA-N alumanylidynesilicon Chemical compound [Al].[Si] CSDREXVUYHZDNP-UHFFFAOYSA-N 0.000 description 2
- 230000033228 biological regulation Effects 0.000 description 2
- 238000003754 machining Methods 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 239000011780 sodium chloride Substances 0.000 description 2
- 229910018137 Al-Zn Inorganic materials 0.000 description 1
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- 229910018563 CuAl2 Inorganic materials 0.000 description 1
- 229910007981 Si-Mg Inorganic materials 0.000 description 1
- 229910008316 Si—Mg Inorganic materials 0.000 description 1
- 229910000831 Steel Inorganic materials 0.000 description 1
- 229910001069 Ti alloy Inorganic materials 0.000 description 1
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Abstract
The invention relates to a high-strength and high-toughness cast aluminum alloy with low copper content and a preparation method thereof, belonging to the technical field of alloys. In order to solve the problems of insufficient strength, low toughness, low elongation, poor corrosion resistance and the like of Al-Si series alloy, the invention provides a high-strength and high-toughness cast aluminum alloy with low copper content, and the chemical components comprise Si 7.2～7.4％、Cu0.48～0.52％、Mg 0.55～0.6％、Mn 0.021～0.25％、Ti 0.14～0.16％、Zn 0.01～0.02％、Be0.025～0.035％、Sr 0.03％、Fe≤0.07％, percent by mass and the balance of Al. The Cu content in the cast aluminum alloy is reduced, the tensile strength, the yield strength and the elongation are improved through solid solution aging heat treatment, the precipitation of CuAl 2 phase is reduced, and the corrosion resistance of the alloy is improved.
Description
Technical Field
The invention belongs to the technical field of alloys, and particularly relates to a high-strength and high-toughness cast aluminum alloy with low copper content and a preparation method thereof.
Background
The aluminum alloy has good electrical conductivity and thermal conductivity, has relatively low density compared with steel, copper alloy, titanium alloy and the like, has good plasticity, non-magnetism and small elastic modulus, and is easy to form a compact oxide film on the surface, thereby having excellent corrosion resistance. The cast aluminum alloy has excellent casting performance, and various parts can be produced in batches according to the requirements of application requirements, part shape, dimensional accuracy, mechanical properties and the like. The device is mainly used for aircraft shells in the aerospace field, engine cases of aeroengines, engine accessory cases, air inlets, lips, blades, pump bodies, hanging frames and other parts. In the field of automobile manufacturing, cast aluminum alloy has important applications, including parts such as cylinder blocks, cylinder heads, gearboxes and pistons of automobile engines, automobile hubs, instrument and meter housings, booster pump bodies and the like. The application in the field of ships is also very wide, such as ship cargo tanks, ship engine pumps, pistons, shells and the like.
The matrix of the cast aluminum alloy is Al element, the main alloying element of the matrix is Si, cu, mg, zn, and the main third additive elements are Mn, fe, ni, ti and the like. The chemical components have great influence on the mechanical property, casting property, machining property and the like of the alloy. Currently, cast aluminum alloys are classified into four types, al-Si, al-Cu, al-Mg, and Al-Zn. The Al-Si alloy is an important series of cast aluminum alloys, and accounts for about 80% of the total yield of cast aluminum alloys. Because of the good fluidity and relatively small shrinkage porosity and hot cracking tendency, castings with compact structures can be obtained. The Al-Si alloy has good casting performance and is suitable for casting large complex thin-wall castings. On the basis of the addition of microelements, the mechanical properties of the alloy can be greatly improved. Casting an A1-Si-Mg alloy is an important branch of the A1-Si alloy, wherein Mg is used as a third additive element, so that not only is the fluidity of the alloy improved and the casting performance improved, but also the Mg 2 Si phase is generated after heat treatment of solid solution and aging as a main strengthening element, the mechanical property of the alloy is obviously improved, but the plasticity is reduced while the strength of the alloy is increased along with the increase of the Mg element. This is because with the increase of Mg content, the eutectic Si phase in the structure coarsens, so that other microelements are required to be added, and the composition of the alloy is adjusted to obtain the corresponding structure and the required mechanical properties. The Al-Cu alloy can be strengthened by heat treatment and has higher mechanical property compared with the Al-Si alloy, but the Al-Cu alloy has wider crystallization range and poorer casting property, and the addition of a large amount of Cu element causes corrosion to be aggravated.
The main technical approach for developing high-strength and high-toughness casting Al-Si alloy is component optimization and regulation and control of a preparation method, in particular to regulation and control of a heat treatment method. The Cu element is added into the cast Al-Si-Mg alloy to form an Al-Si-Mg-Cu cast alloy, and the solution aging heat treatment is adopted to strengthen the alloy, so that the mechanical property is improved, the cast alloy has excellent casting property and machining property, and better comprehensive mechanical property, can be widely applied to various fields of aerospace, automobiles, ocean engineering and the like, and is used for casting large complex thin-wall aluminum alloy precision castings. However, the existing cast Al-Si-Mg-Cu alloy has excessive Cu content, the potential difference between the formed CuAl 2 phase and the matrix is larger, so that the corrosion resistance is reduced, and the performance of the cast under the heat treatment condition of the traditional cast Al-Si-Mg alloy can not meet the increasing high performance requirements in the fields of aerospace, automobiles, ocean engineering and the like. Therefore, the novel casting Al-Si-Mg-Cu alloy with low copper content and high strength and toughness and the heat treatment process thereof have important significance.
Disclosure of Invention
The invention provides a high-strength and high-toughness cast aluminum alloy with low copper content and a preparation method thereof, which are used for solving the problems of insufficient strength, low toughness, low elongation, poor corrosion resistance and the like of Al-Si series alloy.
The technical scheme of the invention is as follows:
a high-strength and high-toughness cast aluminum alloy with low copper content comprises the following chemical components in percentage by mass, and the balance of ：Si：7.2～7.4％、Cu：0.48～0.52％、Mg：0.55～0.6％、Mn：0.021～0.25％、Ti：0.14～0.16％、Zn：0.01～0.02％、Be：0.025～0.035％、Sr：0.03％、Fe≤0.07％, is Al.
A preparation method of a high-strength and high-toughness cast aluminum alloy with low copper content comprises the following steps:
Firstly, preparing aluminum alloy through smelting, refining and sand casting;
step two, placing the aluminum alloy obtained in the step one into a heat treatment furnace for solid solution treatment, wherein the solid solution treatment temperature is 540-550 ℃, and the solid solution treatment time is 13-15 h;
Step three, placing the aluminum alloy treated in the step two into water for quenching;
and fourthly, placing the aluminum alloy treated in the third step into 155-165 ℃ for aging treatment for 5-7 h.
Further, the smelting process in the first step comprises the following steps: after preheating the crucible, adding high-purity aluminum ingot, al-12Si and Al-50Cu intermediate alloy, adding Al-Mg intermediate alloy when the temperature of the alloy melt is raised to 720 ℃ for the first time, adding Al-10Sr modifier when the temperature of the alloy melt reaches 730-740 ℃ and preserving heat for 10min, and adding Al-5Ti-B refiner when the temperature of the alloy melt reaches 730 ℃ and preserving heat for 10min.
Further, the crucible is preheated by firstly preserving the temperature of the crucible at 500 ℃ for 30min and then heating to 750 ℃ for 30min.
Further, the refining process in the first step is as follows: when the temperature of the molten aluminum alloy is reduced to 725 ℃, high-purity argon is introduced to carry out melt refining treatment by adopting a rotary blowing method, the purity of the argon is 99.99%, the rotating speed is 600r/min, and the treatment time is 5-6 min.
Further, the sand casting process in the first step is as follows: and (5) slag skimming is carried out when the temperature of the melt obtained after refining treatment is reduced to 710 ℃, and sand casting is carried out.
Further, in the second step, the solid solution temperature is 545 ℃.
Further, the temperature rising speed in the furnace of the solution treatment in the second step is controlled to be 10 ℃/min.
Further, the water temperature of the quenching in the step three is controlled to be 25-35 ℃ and the quenching time is 40s.
Further, the temperature rising speed of the aging in the fourth step is controlled to be 10 ℃/min.
The invention has the beneficial effects that:
The main phase composition of the high-strength and high-toughness cast aluminum alloy with low copper content provided by the invention is equal to alpha-Al matrix, eutectic Si, mg2Si phase and beta-Al 5FeSi, and w-Al2Cu5Si4Mg4 phase can appear after 0.5% of Cu element is added into the alloy. Compared with the traditional Al-Si-Mg aluminum alloy, the low-copper-content cast aluminum alloy provided by the invention improves the tensile strength, the yield strength and the elongation by adding a small amount of Cu element for alloying, and compared with the traditional Al-Si-Mg-Cu aluminum alloy, the low-copper-content high-strength high-toughness cast aluminum alloy provided by the invention reduces the Cu content, and through subsequent heat treatment, the tensile strength, the yield strength and the elongation are improved, the precipitation of CuAl 2 phase is reduced, and the corrosion resistance of the alloy is improved.
The preparation method of the high-strength and high-toughness cast aluminum alloy with low copper content has the advantages of simple process, low cost and short time consumption, can improve the performance of the cast aluminum alloy obtained by sand casting, greatly improves the tensile strength and the yield strength of the alloy, and has good elongation.
Drawings
FIG. 1 is a graph showing the mechanical properties of the aluminum alloy after solution aging treatment of example 1 and comparative example 1;
FIG. 2 is a graph showing the mechanical properties of the aluminum alloys after solution aging treatment of comparative example 2 and comparative example 3;
FIG. 3 is a SEM scanning image of a fracture of an aluminum alloy after solution aging treatment of example 1;
FIG. 4 is a SEM scanning image of a fracture of an aluminum alloy after solution aging treatment of comparative example 1;
FIG. 5 is a SEM scanning image of the fracture of an aluminum alloy after solution aging treatment of comparative example 4;
FIG. 6 is a SEM scanning image of a fracture of an aluminum alloy after solution aging treatment of comparative example 5;
FIG. 7 is an electrochemical polarization curve of the aluminum alloy after solution aging treatment of example 1 and comparative example 1 in a 3.5wt.% NaCl solution.
Detailed Description
The following embodiments are used for further illustrating the technical scheme of the present invention, but not limited thereto, and all modifications and equivalents of the technical scheme of the present invention are included in the scope of the present invention without departing from the spirit and scope of the technical scheme of the present invention. The process equipment or apparatus not specifically noted in the following examples are all conventional equipment or apparatus in the art, and the raw materials and the like used in the examples of the present invention are commercially available unless otherwise specified; unless specifically indicated, the technical means used in the embodiments of the present invention are conventional means well known to those skilled in the art.
Example 1
The embodiment provides a high-strength and high-toughness cast aluminum alloy with low copper content, which comprises the following chemical components in percentage by mass: si:7.4%, cu:0.52%, mg:0.6%, mn:0.2%, ti:0.14%, zn:0.014%, be:0.028%, sr:0.03%, fe:0.07%, the balance being Al.
Si and Cu play a quite important role as main elements in ZL114A, such as the fluidity of the alloy is improved, the tensile strength is increased, the elongation is reduced and the cutting processability is deteriorated along with the increase of Si content; cu can be dissolved in an aluminum matrix or form various strengthening phases such as CuA1 in an alloy, and the strength and hardness of the alloy can be remarkably improved, but the elongation thereof is reduced.
The addition of small amounts of Ti and B to the alloy can result in significant refinement of the structure. The main function of Ti in aluminum alloy is to refine crystal grains, and the refining function of Ti is mainly from peritectic reaction occurring at 655 ℃:
L+TiAl3→α(Al)
According to the "eutectic" refinement principle, a small amount of Ti forms fine TA in the alloy; the particles are used as the crystal core of the peritectic reaction product alpha (Al), so that the alpha phase is greatly thinned, the CuA12 phase can be more fully dissolved and distributed more uniformly during heat treatment, the effect of preventing grain boundary sliding is fully exerted, and the strengthening effect is improved. At the same time, a small amount of Ti can also improve the thermal tendency of the alloy, because the grain refinement delays the time for forming a crystal skeleton when the alloy is solidified, and the fine grains have larger connecting surfaces, so that the alloy has better mechanical properties near the solid phase temperature. However, the Ti content in the aluminum alloy cannot be too high, otherwise free TiA13 is generated, and the mechanical properties of the alloy are reduced after aggregation. The Ti content in the Al-Si alloy is generally controlled to be 0.1% -0.2%.
Among the microelements, B is the most sensitive and obvious in use effect, and can delay the decay process while enhancing the refining effect. The effect of B in the alloy is that the refining effect of Ti can be enhanced, the effect of adding B into aluminum and the alloy thereof is much better than that of A1-Ti without B, and the attenuation time can be prolonged. Thus, ti and B are added as an A1-Ti-B master alloy in this example.
In addition, the tensile strength of the alloy can be increased by adding Mg into the alloy, a small amount of Mg can form a Mg2Si phase in the aluminum-silicon alloy, the Mg2Si phase is dissolved into a solid solution as a solid solution strengthening phase when being heated, and is separated out as a dispersion phase during aging treatment, so that the crystal lattice of the solid solution is distorted, and the effects of strengthening the alloy and improving the hardness are achieved. When Mg and Cu are simultaneously present in the aluminum-silicon alloy, a W (A1 MgsSiCu) reinforced phase is formed, and the reinforced effect is better than that of CuAl2 and Mg2Si, so that the mechanical property of the alloy is further improved. However, the addition of Mg causes a decrease in the elongation of the alloy, and the content of Mg in the alloy should be controlled to be 0.65% or less in order to maintain a certain plasticity of the alloy.
The embodiment provides a preparation method of a cast aluminum alloy with low copper content, which comprises the following specific steps:
Firstly, preserving heat of a crucible at 500 ℃ for 30min, then heating to 750 ℃ for 30min, adding a high-purity aluminum ingot, al-12Si and Al-50Cu intermediate alloy into the preheated crucible, adding the Al-Mg intermediate alloy when the temperature of an alloy melt is firstly raised to 720 ℃, adding an Al-10Sr modifier and preserving heat for 10min when the temperature of the alloy melt reaches 730-740 ℃, and adding an Al-5Ti-B refiner and preserving heat for 10min when the temperature of the alloy melt reaches 730 ℃;
When the temperature of the molten aluminum alloy is reduced to 725 ℃, high-purity argon is introduced to carry out melt refining treatment by adopting a rotary blowing method, the purity of the argon is 99.99%, the rotating speed is 600r/min, and the treatment time is 5-6 min.
Slag skimming is carried out when the temperature of the melt obtained after refining treatment is reduced to 710 ℃, and sand casting is carried out to obtain aluminum alloy;
Step two, placing the obtained aluminum alloy into a heat treatment furnace for solid solution treatment, wherein the temperature rising speed in the furnace is controlled to be 10 ℃/min, the solid solution treatment temperature is 545 ℃, timing is started after the temperature in the furnace rises to the target temperature, and the solid solution treatment time is 14h;
Step three, placing the aluminum alloy treated in the step two into water for quenching, wherein the water temperature for quenching is controlled to be 25-35 ℃ and the quenching time is 40s;
And fourthly, placing the aluminum alloy treated in the third step in an incubator for ageing treatment, wherein the ageing treatment temperature is 155 ℃, the heating speed is controlled to be 10 ℃/min, the timing is started after the temperature in the oven is increased to the target temperature, and the ageing treatment time is 6h.
Example 2
The embodiment provides a cast aluminum alloy with low copper content, which comprises the following chemical components in percentage by mass: si:7.4%, cu:0.52%, mg:0.6%, mn:0.2%, ti:0.14%, zn:0.014%, be:0.028%, sr:0.03%, fe:0.07%, the balance being Al.
The embodiment provides a preparation method of a cast aluminum alloy with low copper content, which comprises the following specific steps:
Firstly, preserving heat of a crucible at 500 ℃ for 30min, then heating to 750 ℃ for 30min, adding a high-purity aluminum ingot, al-12Si and Al-50Cu intermediate alloy into the preheated crucible, adding the Al-Mg intermediate alloy when the temperature of an alloy melt is firstly raised to 720 ℃, adding an Al-10Sr modifier and preserving heat for 10min when the temperature of the alloy melt reaches 730-740 ℃, and adding an Al-5Ti-B refiner and preserving heat for 10min when the temperature of the alloy melt reaches 730 ℃;
When the temperature of the molten aluminum alloy is reduced to 725 ℃, high-purity argon is introduced to carry out melt refining treatment by adopting a rotary blowing method, the purity of the argon is 99.99%, the rotating speed is 600r/min, and the treatment time is 5-6 min.
Slag skimming is carried out when the temperature of the melt obtained after refining treatment is reduced to 710 ℃, and sand casting is carried out to obtain aluminum alloy;
step two, placing the obtained aluminum alloy into a heat treatment furnace for solid solution treatment, wherein the temperature rising speed in the furnace is controlled to be 10 ℃/min, the solid solution treatment temperature is 540 ℃, timing is started after the temperature in the furnace rises to the target temperature, and the solid solution treatment time is 13h;
Step three, placing the aluminum alloy treated in the step two into water for quenching, wherein the water temperature for quenching is controlled to be 25-35 ℃ and the quenching time is 40s;
And fourthly, placing the aluminum alloy treated in the third step in an incubator for ageing treatment, wherein the ageing treatment temperature is 160 ℃, the heating speed is controlled to be 10 ℃/min, the timing is started after the temperature in the oven is increased to the target temperature, and the ageing treatment time is 5 hours.
Example 3
The embodiment provides a cast aluminum alloy with low copper content, which comprises the following chemical components in percentage by mass: si:7.4%, cu:0.52%, mg:0.6%, mn:0.2%, ti:0.14%, zn:0.014%, be:0.028%, sr:0.03%, fe:0.07%, the balance being Al.
The embodiment provides a preparation method of a cast aluminum alloy with low copper content, which comprises the following specific steps:
Firstly, preserving heat of a crucible at 500 ℃ for 30min, then heating to 750 ℃ for 30min, adding a high-purity aluminum ingot, al-12Si and Al-50Cu intermediate alloy into the preheated crucible, adding the Al-Mg intermediate alloy when the temperature of an alloy melt is firstly raised to 720 ℃, adding an Al-10Sr modifier and preserving heat for 10min when the temperature of the alloy melt reaches 730-740 ℃, and adding an Al-5Ti-B refiner and preserving heat for 10min when the temperature of the alloy melt reaches 730 ℃;
When the temperature of the molten aluminum alloy is reduced to 725 ℃, high-purity argon is introduced to carry out melt refining treatment by adopting a rotary blowing method, the purity of the argon is 99.99%, the rotating speed is 600r/min, and the treatment time is 5-6 min.
Slag skimming is carried out when the temperature of the melt obtained after refining treatment is reduced to 710 ℃, and sand casting is carried out to obtain aluminum alloy;
step two, placing the obtained aluminum alloy into a heat treatment furnace for solid solution treatment, wherein the temperature rising speed in the furnace is controlled to be 10 ℃/min, the solid solution treatment temperature is 550 ℃, timing is started after the temperature in the furnace rises to the target temperature, and the solid solution treatment time is 15h;
Step three, placing the aluminum alloy treated in the step two into water for quenching, wherein the water temperature for quenching is controlled to be 25-35 ℃ and the quenching time is 40s;
And fourthly, placing the aluminum alloy treated in the third step in an incubator for ageing treatment, wherein the ageing treatment temperature is 165 ℃, the heating speed is controlled to be 10 ℃/min, the timing is started after the temperature in the oven is increased to the target temperature, and the ageing treatment time is 7h.
Comparative example 1
The comparative example provides a cast aluminum alloy comprising, in mass percent: si:7.45%, cu:0.01%, mg:0.601%, mn:0.021%, ti:0.152%, zn:0.012%, be:0.03%, sr:0.03%, fe:0.077% and the balance Al.
The preparation method of the cast aluminum alloy of the comparative example comprises the following steps:
Firstly, preserving heat of a crucible at 500 ℃ for 30min, then heating to 750 ℃ for 30min, adding a high-purity aluminum ingot, al-12Si and Al-50Cu intermediate alloy into the preheated crucible, adding the Al-Mg intermediate alloy when the temperature of an alloy melt is firstly raised to 720 ℃, adding an Al-10Sr modifier and preserving heat for 10min when the temperature of the alloy melt reaches 730-740 ℃, and adding an Al-5Ti-B refiner and preserving heat for 10min when the temperature of the alloy melt reaches 730 ℃;
When the temperature of the molten aluminum alloy is reduced to 725 ℃, high-purity argon is introduced to carry out melt refining treatment by adopting a rotary blowing method, the purity of the argon is 99.99%, the rotating speed is 600r/min, and the treatment time is 5-6 min.
Slag skimming is carried out when the temperature of the melt obtained after refining treatment is reduced to 710 ℃, and sand casting is carried out to obtain aluminum alloy;
Step two, placing the obtained aluminum alloy into a heat treatment furnace for solid solution treatment, wherein the temperature rising speed in the furnace is controlled to be 10 ℃/min, the solid solution treatment temperature is 545 ℃, timing is started after the temperature in the furnace rises to the target temperature, and the solid solution treatment time is 14h;
Step three, placing the aluminum alloy treated in the step two into water for quenching, wherein the water temperature for quenching is controlled to be 25-35 ℃ and the quenching time is 40s;
And fourthly, placing the aluminum alloy treated in the third step in an incubator for ageing treatment, wherein the ageing treatment temperature is 155 ℃, the heating speed is controlled to be 10 ℃/min, the timing is started after the temperature in the oven is increased to the target temperature, and the ageing treatment time is 6h.
Comparative example 2
The comparative example provides a cast aluminum alloy comprising, in mass percent: si:7.4%, cu:0.52%, mg:0.6%, mn:0.2%, ti:0.14%, zn:0.014%, be:0.028%, sr:0.03%, fe:0.07%, the balance being Al.
The preparation method of the cast aluminum alloy of the comparative example comprises the following steps:
Firstly, preserving heat of a crucible at 500 ℃ for 30min, then heating to 750 ℃ for 30min, adding a high-purity aluminum ingot, al-12Si and Al-50Cu intermediate alloy into the preheated crucible, adding the Al-Mg intermediate alloy when the temperature of an alloy melt is firstly raised to 720 ℃, adding an Al-10Sr modifier and preserving heat for 10min when the temperature of the alloy melt reaches 730-740 ℃, and adding an Al-5Ti-B refiner and preserving heat for 10min when the temperature of the alloy melt reaches 730 ℃;
When the temperature of the molten aluminum alloy is reduced to 725 ℃, high-purity argon is introduced to carry out melt refining treatment by adopting a rotary blowing method, the purity of the argon is 99.99%, the rotating speed is 600r/min, and the treatment time is 5-6 min.
Slag skimming is carried out when the temperature of the melt obtained after refining treatment is reduced to 710 ℃, and sand casting is carried out to obtain aluminum alloy;
Step two, placing the obtained aluminum alloy into a heat treatment furnace for solid solution treatment, wherein the temperature rising speed in the furnace is controlled to be 10 ℃/min, the solid solution treatment temperature is 545 ℃, timing is started after the temperature in the furnace rises to the target temperature, and the solid solution treatment time is 14h;
Step three, placing the aluminum alloy treated in the step two into water for quenching, wherein the water temperature for quenching is controlled to be 25-35 ℃ and the quenching time is 40s;
And fourthly, placing the aluminum alloy treated in the third step in an incubator for ageing treatment, wherein the ageing treatment temperature is 175 ℃, the heating speed is controlled to be 10 ℃/min, the timing is started after the temperature in the oven is increased to the target temperature, and the ageing treatment time is 12h.
Comparative example 3
The comparative example provides a cast aluminum alloy comprising, in mass percent: si:7.45%, cu:0.01%, mg:0.601%, mn:0.021%, ti:0.152%, zn:0.012%, be:0.03%, sr:0.03%, fe:0.077% and the balance Al.
The preparation method of the cast aluminum alloy of the comparative example comprises the following steps:
Firstly, preserving heat of a crucible at 500 ℃ for 30min, then heating to 750 ℃ for 30min, adding a high-purity aluminum ingot, al-12Si and Al-50Cu intermediate alloy into the preheated crucible, adding the Al-Mg intermediate alloy when the temperature of an alloy melt is firstly raised to 720 ℃, adding an Al-10Sr modifier and preserving heat for 10min when the temperature of the alloy melt reaches 730-740 ℃, and adding an Al-5Ti-B refiner and preserving heat for 10min when the temperature of the alloy melt reaches 730 ℃;
When the temperature of the molten aluminum alloy is reduced to 725 ℃, high-purity argon is introduced to carry out melt refining treatment by adopting a rotary blowing method, the purity of the argon is 99.99%, the rotating speed is 600r/min, and the treatment time is 5-6 min.
Slag skimming is carried out when the temperature of the melt obtained after refining treatment is reduced to 710 ℃, and sand casting is carried out to obtain aluminum alloy;
Step two, placing the obtained aluminum alloy into a heat treatment furnace for solid solution treatment, wherein the temperature rising speed in the furnace is controlled to be 10 ℃/min, the solid solution treatment temperature is 545 ℃, timing is started after the temperature in the furnace rises to the target temperature, and the solid solution treatment time is 14h;
Step three, placing the aluminum alloy treated in the step two into water for quenching, wherein the water temperature for quenching is controlled to be 25-35 ℃ and the quenching time is 40s;
And fourthly, placing the aluminum alloy treated in the third step in an incubator for ageing treatment, wherein the ageing treatment temperature is 175 ℃, the heating speed is controlled to be 10 ℃/min, the timing is started after the temperature in the oven is increased to the target temperature, and the ageing treatment time is 12h.
Comparative example 4
The comparative example provides a cast aluminum alloy comprising, in mass percent: si:7.4%, cu:0.52%, mg:0.6%, mn:0.2%, ti:0.14%, zn:0.014%, be:0.028%, sr:0.03%, fe:0.07%, the balance being Al.
The preparation method of the cast aluminum alloy of the comparative example comprises the following steps:
Firstly, preserving heat of a crucible at 500 ℃ for 30min, then heating to 750 ℃ for 30min, adding a high-purity aluminum ingot, al-12Si and Al-50Cu intermediate alloy into the preheated crucible, adding the Al-Mg intermediate alloy when the temperature of an alloy melt is firstly raised to 720 ℃, adding an Al-10Sr modifier and preserving heat for 10min when the temperature of the alloy melt reaches 730-740 ℃, and adding an Al-5Ti-B refiner and preserving heat for 10min when the temperature of the alloy melt reaches 730 ℃;
When the temperature of the molten aluminum alloy is reduced to 725 ℃, high-purity argon is introduced to carry out melt refining treatment by adopting a rotary blowing method, the purity of the argon is 99.99%, the rotating speed is 600r/min, and the treatment time is 5-6 min.
Slag skimming is carried out when the temperature of the melt obtained after refining treatment is reduced to 710 ℃, and sand casting is carried out to obtain aluminum alloy;
Step two, placing the obtained aluminum alloy into a heat treatment furnace for solid solution treatment, wherein the temperature rising speed in the furnace is controlled to be 10 ℃/min, the solid solution treatment temperature is 545 ℃, timing is started after the temperature in the furnace rises to the target temperature, and the solid solution treatment time is 14h;
Step three, placing the aluminum alloy treated in the step two into water for quenching, wherein the water temperature for quenching is controlled to be 25-35 ℃ and the quenching time is 40s;
And fourthly, placing the aluminum alloy treated in the third step in an incubator for ageing treatment, wherein the ageing treatment temperature is 165 ℃, the heating speed is controlled to be 10 ℃/min, the timing is started after the temperature in the oven is increased to the target temperature, and the ageing treatment time is 12h.
Comparative example 5
The comparative example provides a cast aluminum alloy comprising, in mass percent: si:7.45%, cu:0.01%, mg:0.601%, mn:0.021%, ti:0.152%, zn:0.012%, be:0.03%, sr:0.03%, fe:0.077% and the balance Al.
The preparation method of the cast aluminum alloy of the comparative example comprises the following steps:
Firstly, preserving heat of a crucible at 500 ℃ for 30min, then heating to 750 ℃ for 30min, adding a high-purity aluminum ingot, al-12Si and Al-50Cu intermediate alloy into the preheated crucible, adding the Al-Mg intermediate alloy when the temperature of an alloy melt is firstly raised to 720 ℃, adding an Al-10Sr modifier and preserving heat for 10min when the temperature of the alloy melt reaches 730-740 ℃, and adding an Al-5Ti-B refiner and preserving heat for 10min when the temperature of the alloy melt reaches 730 ℃;
When the temperature of the molten aluminum alloy is reduced to 725 ℃, high-purity argon is introduced to carry out melt refining treatment by adopting a rotary blowing method, the purity of the argon is 99.99%, the rotating speed is 600r/min, and the treatment time is 5-6 min.
Slag skimming is carried out when the temperature of the melt obtained after refining treatment is reduced to 710 ℃, and sand casting is carried out to obtain aluminum alloy;
Step two, placing the obtained aluminum alloy into a heat treatment furnace for solid solution treatment, wherein the temperature rising speed in the furnace is controlled to be 10 ℃/min, the solid solution treatment temperature is 545 ℃, timing is started after the temperature in the furnace rises to the target temperature, and the solid solution treatment time is 14h;
Step three, placing the aluminum alloy treated in the step two into water for quenching, wherein the water temperature for quenching is controlled to be 25-35 ℃ and the quenching time is 40s;
And fourthly, placing the aluminum alloy treated in the third step in an incubator for ageing treatment, wherein the ageing treatment temperature is 165 ℃, the heating speed is controlled to be 10 ℃/min, the timing is started after the temperature in the oven is increased to the target temperature, and the ageing treatment time is 12h.
FIG. 1 is a graph showing the mechanical properties of aluminum alloys after solution aging treatment of example 1 and comparative example 1, wherein UTS represents tensile strength, YS represents yield strength, and El represents elongation; the results showed that the aluminum alloys of example 1 and comparative example 1 had tensile strength averages 366.6MPa and 348.6MPa, respectively, yield strength averages 314.6MPa and 296.44MPa, respectively, and elongation averages 5.2% and 5.04% respectively after heat treatment at 545℃for 14 hours and aging at 155℃for 6 hours.
FIG. 2 is a graph showing the comparison of the mechanical properties of the aluminum alloys after solution aging treatment of comparative example 2 and comparative example 3, and shows that the aluminum alloys of comparative example 2 and comparative example 3 are subjected to solution aging treatment at 545 ℃ for 14 hours, the average tensile strength after aging treatment at 175 ℃ for 12 hours is 368MPa and 348.25MPa, the average yield strength is 343.36MPa and 332.02MPa, and the average elongation is 2% and 1.9%.
As can be seen from fig. 1 and 2, the aluminum alloy containing a small amount of Cu in example 1 has higher mechanical properties, which is mainly related to the w-Al2Cu5Si4Mg4 phase which brings about higher solid solution strengthening effect and a small amount of precipitation by the Cu element solid solution in the matrix. However, although the yield strength of the aluminum alloy is obviously improved after aging for 12 hours at 175 ℃, the elongation is greatly reduced, which is mainly related to nano Mg2Si phase dispersed and precipitated in a matrix in the aging process.
FIGS. 3 to 6 are SEM scanning images of fracture of the aluminum alloy after solution aging treatment of example 1, comparative example 4 and comparative example 5; fig. 3 and 5 show that the fracture of example 1 and comparative example 4 is fully distributed with fine equiaxed ductile pits uniformly distributed, and the area and size of the cleavage plane are smaller, which is a mixed fracture mode and has higher strength and plasticity. While fig. 4 and 6 show that a wide range of irregular cleavage planes with some tearing ridges and a small number of ductile pits can be observed in the fractures of comparative examples 1 and 5, which is a typical quasi-cleavage fracture mode, this phenomenon is mainly related to the second phase which is dispersed and precipitated after high-temperature aging, and the dispersed and precipitated Mg 2 Si and w-Al2Cu5Si4Mg4 phases are brittle phases, and a cleavage effect is generated in the matrix, so that the alloy fractures in brittle fracture.
Fig. 7 is an electrochemical polarization curve of the aluminum alloy after the solution aging treatment of example 1 and comparative example 1 in a 3.5wt.% NaCl solution, and it was found from the observation of fig. 7 that the Cu element content was increased to 0.5%, the corrosion potential of the aluminum alloy was slightly increased, the corrosion tendency of the aluminum alloy was related to the magnitude of the corrosion potential thereof, and the higher the corrosion potential was, the lower the corrosion tendency of the aluminum alloy was. Therefore, when the Cu content is 0.5%, the corrosion potential of the aluminum alloy is-0.82V, showing less corrosion tendency, as compared with the aluminum alloy of comparative example 1; when the Cu content is 0.1%, the corrosion potential of the aluminum alloy is-1.13V, and the corrosion tendency is high. According to the electrochemical parameters of the aluminum alloy measured by tafel linear extrapolation from the polarization curve of fig. 7, the corrosion current density of the aluminum alloy is increased while the Cu element content in the aluminum alloy is increased to 0.5%, the greater the corrosion current density of the aluminum alloy is reflected by the higher corrosion rate, the worse the corrosion resistance of the aluminum alloy is, and the corrosion current density is minimized when the Cu content is 0.1%, so that the corrosion rate of the 0.1% Cu content aluminum alloy is minimized. In summary, the addition of a small amount of Cu has less influence on the corrosion resistance of the material.
Claims (10)
1. A high-strength and high-toughness cast aluminum alloy with low copper content is characterized by comprising ：Si：7.2～7.4％、Cu：0.48～0.52％、Mg：0.55～0.6％、Mn：0.021～0.25％、Ti：0.14～0.16％、Zn：0.01～0.02％、Be：0.025～0.035％、Sr：0.03％、Fe≤0.07％, mass percent of the chemical components and the balance of Al.
2. A method for producing a high strength and toughness cast aluminum alloy having a low copper content as claimed in claim 1, comprising the steps of:
Firstly, preparing aluminum alloy through smelting, refining and sand casting;
step two, placing the aluminum alloy obtained in the step one into a heat treatment furnace for solid solution treatment, wherein the solid solution treatment temperature is 540-550 ℃ and the solid solution treatment time is 13-15 h;
Step three, placing the aluminum alloy treated in the step two into water for quenching;
and fourthly, placing the aluminum alloy treated in the third step into 155-165 ℃ for aging treatment for 5-7 h.
3. The method for producing a high strength and toughness cast aluminum alloy with a low copper content according to claim 2, wherein the smelting process of step one is: after preheating the crucible, adding high-purity aluminum ingot, al-12Si and Al-50Cu intermediate alloy, adding Al-Mg intermediate alloy when the temperature of the alloy melt is raised to 720 ℃ for the first time, adding Al-10Sr modifier when the temperature of the alloy melt reaches 730-740 ℃ and preserving heat for 10min, and adding Al-5Ti-B refiner when the temperature of the alloy melt reaches 730 ℃ and preserving heat for 10min.
4. The method for producing a high strength and toughness cast aluminum alloy with a low copper content according to claim 3, wherein the crucible is preheated by first maintaining the crucible at 500 ℃ for 30min and then heating to 750 ℃ for 30min.
5. The method for producing a high strength and toughness cast aluminum alloy having a low copper content according to any one of claims 2 to 4, wherein the refining process of step one is: when the temperature of the molten aluminum alloy is reduced to 725 ℃, high-purity argon is introduced to carry out melt refining treatment by adopting a rotary blowing method, the purity of the argon is 99.99%, the rotating speed is 600r/min, and the treatment time is 5-6 min.
6. The method for producing a high strength and toughness cast aluminum alloy having a low copper content according to claim 5, wherein the sand casting process of step one is: and (5) slag skimming is carried out when the temperature of the melt obtained after refining treatment is reduced to 710 ℃, and sand casting is carried out.
7. The method of producing a high strength and toughness cast aluminum alloy having a low copper content as claimed in claim 6, wherein said solution temperature in step two is 545 ℃.
8. The method for producing a high strength and toughness cast aluminum alloy with a low copper content according to claim 7, wherein the temperature rise rate in the furnace for the solution treatment in the second step is controlled to be 10 ℃/min.
9. The method for producing a high strength and toughness cast aluminum alloy with a low copper content according to claim 8, wherein the water temperature for quenching in the third step is controlled to be 25-35 ℃ and the quenching time is 40s.
10. The method for producing a high strength and toughness cast aluminum alloy with a low copper content according to claim 9, wherein the temperature rise rate of the aging in the fourth step is controlled to be 10 ℃/min.
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