CN114231800B - High-performance low-carbon aluminum alloy and preparation method thereof - Google Patents

High-performance low-carbon aluminum alloy and preparation method thereof Download PDF

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CN114231800B
CN114231800B CN202111665663.1A CN202111665663A CN114231800B CN 114231800 B CN114231800 B CN 114231800B CN 202111665663 A CN202111665663 A CN 202111665663A CN 114231800 B CN114231800 B CN 114231800B
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aluminum alloy
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carbon
temperature
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CN114231800A (en
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王俊升
刘鑫秀
王兵
杨兴海
田光元
李全
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Beijing Institute of Technology BIT
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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
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C1/00—Making non-ferrous alloys
    • C22C1/02—Making non-ferrous alloys by melting
    • C22C1/026—Alloys based on aluminium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C1/00—Making non-ferrous alloys
    • C22C1/02—Making non-ferrous alloys by melting
    • C22C1/03—Making non-ferrous alloys by melting using master alloys
    • 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
    • C22F1/002—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working by rapid cooling or quenching; cooling agents used therefor
    • 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

Abstract

The invention provides a high-performance low-carbon aluminum alloy and a preparation method thereof, belonging to the technical field of aluminum alloy materials. The paint comprises the following chemical compositions: by mass percent, si:6 to 8%, cu:3 to 5 percent, mg: 0.2-0.6%, fe is less than or equal to 0.8%, mn:0.3 to 0.6%, ti:0.02 to 0.04%, la:0.05 to 0.15 percent, and the balance of Al and inevitable impurities. By component optimization and process parameter adjustment, the yield strength of the casting reaches more than 400MPa, the tensile strength reaches more than 430MPa, the hardness reaches more than 155HV, and the elongation reaches more than 4.0%. The invention serves the national important strategy of 'carbon peak reaching and carbon neutralization', the manufacturing process is pollution-free, the carbon emission is only 5 percent of that of the high-performance aluminum alloy structural member produced by electrolytic aluminum, and the bottleneck problem that the regenerated aluminum alloy can not be applied to high-end products is thoroughly solved.

Description

High-performance low-carbon aluminum alloy and preparation method thereof
Technical Field
The invention relates to the technical field of aluminum alloy materials, in particular to a high-performance low-carbon aluminum alloy and a preparation method thereof.
Background
The aluminum alloy has the advantages of low density, high specific strength, good corrosion resistance, recyclability and the like, and is widely applied to the fields of automobiles, aerospace and the like, but the high energy consumption and carbon emission in the aluminum electrolysis process restrict the further development of the industry. Aiming at the national important strategy of 'carbon peak reaching and carbon neutralization' and the core technical problem of 'low-carbon aluminum' in China, the regenerated cast aluminum alloy technology reduces carbon emission by more than 95%, and has good application value and development prospect.
The aluminum-silicon alloy is the most important cast aluminum alloy because of good casting performance, small shrinkage tendency and easy product forming. However, the enrichment of Fe element, coarse grains, micro holes and the existence of plate-like eutectic silicon hinder the performance improvement.
CN102071341A discloses a cast aluminum-silicon alloy for an engine cylinder cover and a heat treatment process, wherein the alloy comprises the following chemical components in percentage by weight: si:5.0 to 7.0 percent; cu:3.0 to 4.0 percent; mg:0.2 to 0.4 percent; mn:0.1 to 0.3 percent; zr:0.10 to 0.20 percent; ti:0.15 to 0.25 percent; b:0.01 to 0.05 percent; sr:0.02 to 0.09 percent; RE:0.1 to 0.3 percent; fe <0.3%; al: and (4) the balance. The rare earth Re adopts mixed rare earth. The heat treatment process adopts different primary solid solution temperatures of 500 plus or minus 5 ℃ and secondary solid solution temperatures of 520 plus or minus 5 ℃, the final tensile strength is 325-355 MPa, and the strengthening effect is not obvious enough.
CN113355567A discloses an aluminum-silicon cast aluminum alloy and a preparation method thereof, wherein the aluminum-silicon cast aluminum alloy comprises the following components in parts by weight: si: 7.2-7.4%, mg:0.4 to 0.8%, B:0.003 to 0.007 percent, sr: 0.005-0.01%, ti:0.05 to 0.15%, re: 1-2%, cu is less than or equal to 0.1%, and the balance is Al. The Re element with the content of 1-2% is added into the aluminum-silicon alloy, so that higher toughness can be obtained, but the technology adds more rare earth elements, the precipitation restriction performance of a rare earth-rich phase is improved, and the cost control is not facilitated.
In conclusion, the mechanical properties of the aluminum-silicon alloy still need to be further improved.
Disclosure of Invention
The invention aims to provide a high-performance low-carbon aluminum alloy and a preparation method thereof, which greatly improve the mechanical property and can meet the high requirements of automobile structural parts in the manufacturing and application processes, in particular to new energy automobiles.
In order to solve the technical problems, the invention provides the following technical scheme:
the first aspect provides a high-performance low-carbon aluminum alloy, which comprises the following chemical compositions: by mass percent, si:6 to 8%, cu:3 to 5 percent, mg: 0.2-0.6%, fe is less than or equal to 0.8%, mn:0.3 to 0.6%, ti:0.02 to 0.04%, la:0.05 to 0.15 percent, and the balance of Al and inevitable impurities.
Preferably, in mass percent, si:7 to 8%, cu:3 to 4 percent, mg: 0.2-0.4%, fe is less than or equal to 0.4%, mn:0.3 to 0.4%, ti:0.02 to 0.03%, la:0.06 to 0.14 percent, and the balance of Al and inevitable impurities.
Wherein the ratio of Mn/Fe content is 0.7-1.
Wherein the performance of the casting formed by the high-performance low-carbon aluminum alloy meets the following requirements: the yield strength reaches more than 400MPa, the tensile strength reaches more than 430MPa, the hardness reaches more than 155HV, and the elongation reaches more than 4%.
A second aspect provides a method for preparing the high-performance low-carbon aluminum alloy of the first aspect, comprising:
s1: proportioning raw materials according to the required chemical composition, wherein the raw materials are intermediate alloys of pure aluminum and other raw materials;
s2: preheating the raw materials;
s3: smelting and refining the preheated raw materials, and pouring and cooling after all the raw materials are melted to obtain an aluminum alloy casting;
s4: carrying out solution heat treatment on the aluminum alloy casting by adopting a two-stage solution process: the primary solution treatment temperature is 400-450 ℃, the primary solution treatment time is 4-10 h, the secondary solution treatment temperature is 500-510 ℃, and the secondary solution treatment time is 8-20 h;
s5: and carrying out water quenching and artificial aging on the aluminum alloy casting subjected to the solution heat treatment to obtain the high-performance low-carbon aluminum alloy.
Preferably, in S4, the temperature increase rate in the solution heat treatment is controlled to be 2-8 ℃/min.
Preferably, in S3, the smelting conditions include: the smelting temperature is 710-740 ℃, and the heat preservation time is 10-20min.
Preferably, in S3, the refining conditions include: refining for 10-20min, then removing floating slag on the surface of the melt, and then standing for 15-20 min.
Preferably, in S2, the preheating conditions include: the preheating temperature is 180-200 ℃, and the preheating time is 20-30 min.
Preferably, in S5, the water quenching is carried out to reduce the temperature to 20-30 ℃; after water quenching, artificial aging treatment is carried out in a heat treatment furnace at 170-180 ℃ for 6-18 h.
Preferably, the preparation method further comprises: and in S3, after all the raw materials are melted, preserving heat for 10-15 min, and then pouring.
The inventor of the invention discovers through a great deal of research that on the basis of the conventional aluminum-silicon alloy, from the aspects of material formula and preparation method, by adjusting microalloy components and process parameters, the structure and the second phase can be refined, the harm of an iron-rich phase and micropores is reduced, the effects of fine grain strengthening, precipitation strengthening and second phase strengthening are considered, and the high-performance low-carbon aluminum alloy is developed and can meet the requirement of new energy automobile structural parts on higher performance. The preparation method of the high-performance low-carbon aluminum alloy not only accords with the concepts of energy conservation, emission reduction and green development, but also fully considers the cost, and simultaneously can improve the comprehensive mechanical property of the high-performance low-carbon aluminum alloy material.
Specifically, the technical scheme of the invention has the following beneficial effects:
in the scheme, the contents of elements such as Si, mn and La in the aluminum-silicon alloy are adjusted, so that the adverse effects of coarse grains, iron-rich phases, holes and coarse eutectic silicon in the cast aluminum alloy can be reduced; wherein, concrete reflection is:
1. by adjusting the addition of Mn element and compositely adding a grain refiner Al-Ti-B (B is one of unavoidable elements) and rare earth La, the number of holes and the content of beta-Fe in the casting are obviously reduced, the conversion of eutectic silicon from a plate shape to a coralline shape is promoted, grains are refined, and the strength and the plasticity of the casting are improved at the same time;
2. the method is suitable for a small amount of La element, and can obviously adsorb H in the alloy casting, thereby reducing holes; la has a certain degree of metamorphism to coarse eutectic silicon, promotes the transformation of the eutectic silicon from plate shape to coral shape, and weakens the splitting effect of the eutectic silicon on a matrix. As the rare earth element is a surface active element, the rare earth element can be enriched on a solid-liquid interface in the casting process, the generated component is overcooled, the growth of crystal grains is hindered, and the fine crystal strengthening effect is enhanced. However, excessive rare earth elements are easy to form hard and brittle phases, and the plasticity of the casting is reduced. The addition amount of La in the invention can fully exert the beneficial effect of rare earth without generating the waste of raw materials and the performance damage.
The yield strength of the high-performance low-carbon aluminum alloy casting provided by the invention reaches more than 400MPa, the tensile strength reaches more than 430MPa, the hardness reaches more than 155HV, and the elongation rate reaches more than 4%. The invention conforms to the national important strategy of carbon peak reaching and carbon neutralization, has no pollution in the manufacturing process, can not discharge carbon to 5 percent of the high-performance aluminum alloy structural part produced by electrolytic aluminum, thoroughly solves the bottleneck problem that the regenerated aluminum alloy can not be applied to high-end products, and improves the engineering technical problems of compactness of the internal structure of the cast ingot, stress concentration caused by micropore aggregation and coarse second phase and the like.
In a preferred scheme of the invention, the ratio of Mn/Fe content is suitable, wherein Mn can replace Fe atoms in the iron-rich phase to a certain extent, so that the harm of the iron-rich phase is reduced; the proper amount of Mn element can promote the conversion of the ferrite from needle shape to skeleton shape, and further improve the mechanical property of the obtained material. While an excessive amount of Mn element causes an increase in the volume fraction of the Fe-rich phase, thereby deteriorating the mechanical properties thereof.
The preparation method of the invention can further improve the mechanical property of the material by utilizing a heat treatment process, particularly adopts a two-stage solution treatment process, wherein the heat preservation at 400-450 ℃ for 4-10 hours promotes the dissolution of the low-melting-point nonequilibrium eutectic phase in advance, and in the two-stage solution treatment, the single-stage solid solution does not dissolve the large second phase which is melted into the matrix at 500-510 ℃ under the same temperature without overburning, so that the supersaturation degree of the alloy is increased, and the aging strengthening effect is improved.
Drawings
Fig. 1 is a microstructure morphology of the alloy after corrosion in the embodiment 1 and the embodiment 2 of the present invention, which is used for observing and quantifying the secondary dendrite arm spacing of the alloy, wherein: (a) The photograph was taken with a microscope in example 1, and (b) was taken with a microscope in example 2.
Fig. 2 is a microstructure morphology of the alloy in the embodiment 1 and the embodiment 2 of the present invention after the eutectic silicon is modified, wherein: (a) The photograph was taken with a microscope in example 1, and (b) was taken with a microscope in example 2.
Fig. 3 is a microstructure of the alloy of the embodiment 1 and the embodiment 2 of the invention for observing the morphological transformation of the iron compound, wherein: (a) The SEM image of example 1 is shown, and (b) the SEM image of example 2 is shown.
Detailed Description
In order to make the technical problems, technical solutions and advantages of the present invention more apparent, the following detailed description is given with reference to the accompanying drawings and specific embodiments.
The first aspect provides a high-performance low-carbon aluminum alloy, which comprises the following chemical compositions: by mass percent, si:6 to 8%, cu:3 to 5 percent, mg: 0.2-0.6%, fe is less than or equal to 0.8%, mn:0.3 to 0.6%, ti:0.02 to 0.04%, la:0.05 to 0.15 percent, and the balance of Al and inevitable impurities.
In the high-performance low-carbon aluminum alloy, al, si, cu and Mg are used as basic components, mn, ti and La are used as additive components, a proper amount of Mn is added particularly for the enrichment problem of Fe element in cast aluminum alloy, a proper amount of rare earth element La and a refiner Al-Ti-B (B is one of inevitable impurities) are selected for composite addition, and the alloy structure is optimized based on the synergistic regulation and control effect of the Mn, the La and the refiner Al-Ti-B, so that the comprehensive mechanical property of the high-performance low-carbon aluminum alloy is improved.
The functions of the components comprise:
al, si, cu and Mg are basic components of the alloy, and the addition of Si can reduce and avoid heat cracking and improve the casting performance of the alloy; cu element has certain solid solution strengthening effect and Al precipitated by aging 2 Cu has obvious aging strengthening effect; mg element improves the tensile strength of the casting. Wherein Si may be selected from any of 6%,6.5%,7%,7.5%,8% and any value between adjacent values, cu may be selected from any of 3%,3.5%,4%,4.5%,5% and any value between adjacent values, and Mg may be selected from any of 0.2%,0.3%,0.4%,0.5%,0.6%,0.7%,0.8% and any value between adjacent values.
Mn, ti and La are used as additive components and have positive effects on regulation and control of organization and performance, mn is a high-efficiency Fe neutralizing element, promotes the conversion of beta-Fe to alpha-Fe, reduces the cutting effect of the beta-Fe on a matrix and reduces stress concentration; la has various optimization functions on casting structures, has strong adsorption effect on H elements, and can obviously reduce the number of air holes; the La element is enriched at the front end of the solid-liquid interface, so that the growth of crystal grains is hindered, the La element is added with Ti in a composite way, the fine grain strengthening effect is enhanced, and the improvement of strength and plasticity are considered; the La element has a certain modification effect on the coarse flaky eutectic silicon, and the addition of a small amount of La can promote the transformation of the eutectic silicon from a flaky shape to a coral shape and a granular shape; in addition, similar to Mn, la also promotes the conversion of iron-rich phases to less harmful types to reduce the damage. Wherein, mn can be selected from any value of 0.3%,0.35%,0.4%,0.45%,0.5%,0.55%,0.6% and any value between adjacent points, ti can be selected from any value of 0.02%,0.03%,0.035%,0.04% and any value between adjacent points, and La can be selected from any value of 0.05%,0.07%,0.1%,0.13%,0.15% and any value between adjacent points.
Preferably, the ratio of Si:7 to 8%, cu:3 to 4 percent, mg: 0.2-0.4%, fe is less than or equal to 0.4%, mn:0.3 to 0.4%, ti:0.02 to 0.03%, la:0.06 to 0.14 percent, and the balance of Al and inevitable impurities.
Preferably, the ratio of Mn/Fe content is 0.7 to 1. Under the preferable scheme, the Mn element can replace Fe atoms in the iron-rich phase to a certain extent, so that the harm of the iron-rich phase is reduced; the proper amount of Mn element can promote the conversion of the ferrite from needle shape to skeleton shape, and further improve the mechanical property of the obtained alloy material. While an excessive amount of Mn element causes an increase in the volume fraction of the Fe-rich phase, thereby deteriorating the mechanical properties thereof.
Wherein the performance of the casting formed by the high-performance low-carbon aluminum alloy meets the following requirements: the yield strength reaches more than 400MPa, the tensile strength reaches more than 430MPa, the hardness reaches more than 155HV, and the elongation reaches more than 4%.
A second aspect provides a method for preparing the high-performance low-carbon aluminum alloy of the first aspect, comprising:
s1: proportioning raw materials according to the required chemical composition, wherein the raw materials are intermediate alloys of pure aluminum and other raw materials;
s2: preheating the raw materials;
s3: smelting and refining the preheated raw materials, and pouring and cooling after all the raw materials are melted to obtain an aluminum alloy casting;
s4: carrying out solution heat treatment on the aluminum alloy casting by adopting a two-stage solution process: the primary solution treatment temperature is 400-450 ℃, the primary solution treatment time is 4-10 h, the secondary solution treatment temperature is 500-510 ℃, and the secondary solution treatment time is 8-20 h;
s5: and carrying out water quenching and artificial aging on the aluminum alloy casting subjected to the solution heat treatment to obtain the high-performance low-carbon aluminum alloy.
In S1, it is understood that the master alloy of other raw materials includes: aluminum-silicon, aluminum-iron, aluminum-manganese, aluminum-copper, aluminum-lanthanum, aluminum-magnesium, aluminum-titanium-boron and other intermediate alloys.
In the present invention, generally, in addition to the compounding according to the composition of the resulting material, the loss or accumulation in each production step should be considered, for example, the burning loss of 20% of the Mg element and the accumulation of the Fe element in the master alloy. Which are well known in the art and will not be described in detail herein.
In the present invention, the raw materials may be pretreated by those skilled in the art as required, including but not limited to, all raw materials are pretreated by surface polishing, ultrasonic oscillation, etc. to remove oxides and impurities.
Preferably, in S2, the preheating conditions include: the preheating temperature is 180-200 ℃, and the preheating time is 20-30 min.
The skilled person can select the equipment needed for the above steps according to the needs, including but not limited to molds, crucibles, clamps, etc. The required equipment is preferably subjected to the preheating, and after sufficient drying, is used. Preferably, the crucible used is heated for 20-30min at 130-160 ℃ in advance, the inner surface of the crucible is coated with boron nitride coating, and then the preheating is carried out before the smelting.
Preferably, in S3, the smelting conditions include: the smelting temperature is 710-740 ℃, preferably 720-740 ℃. Under the optimized scheme, the smelting temperature is proper, the crystal grains can be promoted to grow properly, and segregation is avoided, so that the mechanical property of the obtained alloy can be improved. When the smelting temperature is too high, the alloy is seriously burnt in a short time, and the crystal grains are coarse, and when the smelting temperature is too low, the segregation of the molten metal is serious.
Preferably, in S3, the smelting conditions include: the heat preservation time is 10-20min.
It is understood that the refining is performed immediately after the melting is performed, so that the temperature of the refining is the same as the melting temperature.
Preferably, in S3, the refining conditions include: refining for 10-20min, then removing floating slag on the surface of the melt, and then standing for 15-20 min.
One skilled in the art can add protective agents or additives to the melting and refining to protect the alloy melt or to facilitate melting and refining, respectively. Preferably, a covering agent and a refining agent are added in the refining, and the amount of the covering agent and the amount of the refining agent are respectively and independently 0.5-1 wt% of the total amount of the raw materials.
The time of addition of each raw material can be determined as desired by one skilled in the art. Generally, pure aluminum, aluminum silicon, aluminum iron, aluminum manganese and aluminum copper intermediate alloy are added in the smelting, then aluminum lanthanum, aluminum magnesium and aluminum titanium boron intermediate alloy are sequentially added into the melt with the surface scum removed after the refining, stirring (preferably stirring for 3-5 min) is carried out, and then the casting is carried out.
Preferably, the preparation method further comprises: and in S3, after all the raw materials are melted, preserving heat for 10-15 min, and then pouring.
The temperature of the casting can be determined as desired by the person skilled in the art, for example around 730 ℃.
Preferably, in S4, the temperature rise rate in the solution heat treatment is controlled to be 2-8 ℃/min.
Preferably, in S5, the water quenching is carried out to reduce the temperature to 20-30 ℃; after the water quenching, the artificial aging treatment is carried out in a heat treatment furnace with the temperature of 120-180 ℃, preferably 170-180 ℃ for 6-18 h.
In S5, the cooling is preferably air cooling.
The high-performance low-carbon aluminum alloy can meet the high requirements of new energy automobile parts.
The present invention is illustrated in detail by the following examples.
Example 1
A high-performance low-carbon aluminum alloy comprises the following chemical components in percentage by mass: 7.23% of Si, 3.38% of Cu, 0.26% of Mg, 0.39% of Fe, 0.38% of Mn, 0.02% of Ti, 0.07% of La, and the balance of Al and inevitable impurities.
The preparation method of the alloy comprises the following steps:
s1, selecting raw materials: proportioning the components of the high-performance low-carbon aluminum alloy, wherein the raw material is an intermediate alloy of pure aluminum and other raw materials;
s2, preprocessing: all raw materials are subjected to surface grinding and polishing and ultrasonic oscillation pretreatment to remove the influence of oxides and impurities; before smelting, preheating the raw materials, the mold, the crucible, the clamp and the covering agent at 200 ℃ for 20 minutes, and fully drying for use;
s3, smelting: sequentially adding pure aluminum, aluminum silicon, aluminum iron, aluminum manganese and aluminum copper intermediate alloy in the raw materials preheated in the step S2 into a furnace, raising the temperature in the furnace to 730 ℃, and preserving the temperature for 15min to obtain a melt;
s4, aluminum liquid treatment: fully stirring the melt in the step S3, adding a covering agent (specifically comprising 43.5wt% of NaCl and 56.5wt% of KCl, easy to deliquesce and needing preheating in advance) with the amount of 0.8wt% of the total mass of the raw materials and a refining agent (specifically hexachloroethane, needing no preheating) with the amount of 0.8wt% of the total mass of the raw materials, refining for 10min, removing scum, and standing for 15min;
s5, adding an intermediate alloy: sequentially adding aluminum lanthanum, aluminum magnesium and aluminum titanium boron intermediate alloy into the melt with the scum removed in the step S4, and stirring for 3min;
s6, pouring: pouring at the temperature of 10min and 730 ℃ after the intermediate alloy added in the step S5 is completely melted, and cooling and taking out the high-performance low-carbon aluminum alloy casting;
s7, solution heat treatment: transferring the casting taken out in the S6 into a preheated heat treatment furnace for solution heat treatment: the temperature rise speed in the furnace is 5 ℃/min, a two-stage solid solution process is adopted, the first-stage solid solution treatment temperature is 450 ℃, the treatment time is 4 hours, the second-stage solid solution temperature is 500 ℃, and the solid solution time is 8 hours;
s8, aging treatment: and carrying out water quenching after the solution treatment, cooling to 25 ℃, then transferring to a heat treatment furnace at 180 ℃ for artificial aging treatment for 7 hours, cooling to room temperature after the aging treatment.
The resulting aluminum alloy was sampled and subjected to etching treatment using Kahler's reagent (95wt% H) 2 O、2.5wt％HNO 3 1.5wt% hcl and 1.0wt% hf) etching the sample for 8s. The photo of the etched wafer and the photo of the eutectic silicon modified wafer are shown in FIG. 1 and FIG. 2 (a), respectively. The SEM image of the sample treated in S7 and S8 is shown in fig. 3 (a). And taking 30 sample data of the secondary dendrite arm spacing of each sample, and carrying out statistics on an average value, wherein 8 pictures are respectively adopted for quantitative statistics on the average equivalent diameter and the roundness of the eutectic silicon. The results show that the average secondary dendrite arm spacing in example 1 was 13.89 μm, the average equivalent diameter of eutectic silicon was 3.59 μm, and the average roundness was 0.46.
Performing mechanical property test on the obtained aluminum alloy, wherein the tensile property test is performed at the room temperature of a Suns UTM6104 electronic universal stretcher, the strain rate is 1mm/min, and the experimental result is the average value of 3 samples; microhardness testing using a digital microhardness tester (TMVS-1), load set at 200gf, hold time 10s, 10 replicates per sample and an average value was taken. And (3) measuring the following results: the yield strength reaches 406.65Mpa, the tensile strength reaches 432.17Mpa, the elongation is 4.4%, and the hardness reaches 160.47HV.
Example 2
A high-performance low-carbon aluminum alloy comprises the following chemical components in percentage by mass: 7.29%, cu:3.49%, mg:0.28%, fe:0.38%, mn:0.37%, ti:0.02%, la:0.11%, the balance being aluminum and unavoidable impurities. The alloy was prepared according to the procedure of example 1.
The aluminum alloy obtained was sampled, treated, and tested according to the method of example 1, and the SEM electron micrographs after the etching treatment, the eutectic silicon modification, and the heat treatment were as shown in fig. 1, fig. 2, and fig. 3 (b), respectively. The results show that the average secondary dendrite arm spacing in example 2 was 13.42 μm, the average equivalent diameter of eutectic silicon was 3.63 μm, and the average roundness was 0.47.
The mechanical properties of the obtained aluminum alloy were tested according to the method of example 1, and the results were: the yield strength reaches 403.13Mpa, the tensile strength reaches 438.49Mpa, the elongation is 4.8%, and the hardness reaches 162.35HV.
Example 3
A high-performance low-carbon aluminum alloy comprises the following chemical components in percentage by mass: 7.29% of Si, 3.48% of Cu, 0.27% of Mg, 0.37% of Fe, 0.69% of Mn, 0.02% of Ti, 0.05% of La and the balance of Al and inevitable impurities.
The alloy obtained in this example was tested accordingly as in example 1.
The results show an average secondary dendrite arm spacing of 13.97 μm, an average equivalent eutectic silicon diameter of 3.63 μm, and an average roundness of 0.47.
The mechanical property test result is as follows: the yield strength reaches 403.25Mpa, the tensile strength reaches 425.57Mpa, the elongation is 3.5%, and the hardness reaches 155.82HV.
Example 4
A high-performance low-carbon aluminum alloy comprises the following chemical components in percentage by mass: 7.38% of Si, 3.52% of Cu, 0.26% of Mg, 0.39% of Fe, 0.38% of Mn, 0.02% of Ti, 0.18% of La, and the balance of Al and inevitable impurities.
The alloy obtained in this example was tested accordingly as in example 1.
The results show an average secondary dendrite arm spacing of 13.40 μm, an average eutectic silicon equivalent diameter of 3.64 μm, and an average roundness of 0.47.
The mechanical property test result is as follows: the yield strength reaches 402.58Mpa, the tensile strength reaches 428.66Mpa, the elongation is 3.9 percent, and the hardness reaches 162.77HV.
Example 5
The procedure is as in example 1, except that the melting temperature is 690 ℃.
The alloy obtained in this example was tested accordingly as in example 1.
The results show an average secondary dendrite arm spacing of 13.42 μm, an average equivalent diameter of eutectic silicon of 3.71 μm, and an average roundness of 0.48.
The mechanical property test result is as follows: the yield strength reaches 406.05Mpa, the tensile strength reaches 435.94Mpa, the elongation is 3.6%, and the hardness reaches 161.83HV.
Comparative example 1
The procedure of example 1 was repeated, except that the solution heat treatment was carried out at a primary solution treatment temperature of 500 ℃ and a secondary solution treatment temperature of 520 ℃. At the moment, the solid solution temperature is too high, and the sample is over-burnt, so that the secondary solid solution temperature does not exceed 510 ℃.
While the foregoing is directed to the preferred embodiment of the present invention, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the appended claims.

Claims (8)

1. A high-performance low-carbon aluminum alloy is characterized by comprising the following chemical components: by mass percent, si:6 to 8%, cu: 3.38-5%, mg: 0.2-0.6%, fe is less than or equal to 0.8%, mn:0.3 to 0.6%, ti:0.02 to 0.04%, la:0.05 to 0.15 percent, and the balance of Al and inevitable impurities;
the ratio of Mn/Fe content is 0.7-1;
the performance of the casting formed by the high-performance low-carbon aluminum alloy meets the following requirements: the yield strength reaches more than 400MPa, the tensile strength reaches more than 430MPa, the hardness reaches more than 155HV, and the elongation reaches more than 4%.
2. The high performance low carbon aluminum alloy of claim 1, wherein the ratio of Si:7 to 8%, cu: 3.38-4%, mg: 0.2-0.4%, fe is less than or equal to 0.4%, mn:0.3 to 0.4%, ti:0.02 to 0.03%, la:0.06 to 0.14 percent, and the balance of Al and inevitable impurities.
3. A method of making the high performance, low carbon aluminum alloy of claim 1, comprising:
s1: proportioning raw materials according to the required chemical composition, wherein the raw materials are intermediate alloys of pure aluminum and other raw materials;
s2: preheating the raw materials;
s3: smelting and refining the preheated raw materials, and pouring and cooling after all the raw materials are melted to obtain an aluminum alloy casting;
s4: carrying out solution heat treatment on the aluminum alloy casting by adopting a two-stage solution process: the primary solution treatment temperature is 400-450 ℃, the primary solution treatment time is 4-10 h, the secondary solution treatment temperature is 500-510 ℃, and the secondary solution treatment time is 8-20 h;
s5: and carrying out water quenching and artificial aging on the aluminum alloy casting subjected to the solution heat treatment to obtain the high-performance low-carbon aluminum alloy.
4. The production method according to claim 3, wherein in S4, the temperature increase rate in the solution heat treatment is controlled to be 2 to 8 ℃/min.
5. The production method according to claim 3, wherein, in S3,
the smelting conditions comprise: the smelting temperature is 710-740 ℃, and the heat preservation time is 10-20min;
the refining conditions include: refining for 10-20min, then removing floating slag on the surface of the melt, and then standing for 15-20 min.
6. The method according to claim 3, wherein in S2, the preheating conditions include: the preheating temperature is 180-200 ℃, and the preheating time is 20-30 min.
7. The preparation method according to claim 3, wherein in S5, the water quenching is carried out to reduce the temperature to 20-30 ℃; after water quenching, artificial aging treatment is carried out in a heat treatment furnace at 120-180 ℃ for 6-18 h.
8. The method of claim 3, further comprising: and in S3, after all the raw materials are melted, preserving heat for 10-15 min, and then pouring.
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