A low-cost cast aluminum alloy suitable for high-temperature use and a preparation method thereof

Abstract

The present invention relates to the technical field of non-ferrous metal material preparation, and specifically relates to a low-cost cast aluminum alloy suitable for high-temperature use and a preparation method thereof, including alloy components with the following mass percentages: Si: 9%, Cu: 1%, Mg: 0.5%, Fe: 0.3%, Cr: 0.2%, Ti: 0.32%, V: 0.2%, Mn: 0.2%, Zr: 0.1%, Mo: 0.2%, Sr: 0.008%, the total amount of other impurities ≤ 0.1%, and the balance is Al; the present invention also discloses a preparation method of a low-cost cast aluminum alloy suitable for high-temperature use, including the following steps: S1. Batching: Set the corresponding preparation quality. The present invention comprehensively considers the high-temperature performance and production cost of the material, mainly optimizes the composition by compounding and adding six transition metal elements to the base alloy, and develops a cast aluminum alloy material with excellent comprehensive mechanical properties and low cost in a high-temperature environment, especially above 300°C, so as to solve the problems of insufficient high-temperature performance and high cost of existing cast aluminum alloys.

Description

Technical Field

[0001] The present invention relates to the technical field of non-ferrous metal material preparation, and particularly relates to a low-cost cast aluminum alloy suitable for high-temperature use and a preparation method thereof. Background Art

[0002] With the rapid development of fields such as aerospace, automobiles, ships, and weapons, the application of aluminum alloys is becoming more and more extensive, and the requirements for their performance are also constantly improving. For example, for cast heat-resistant aluminum alloys, it is required to have sufficient strength and toughness at high temperatures, as well as good oxidation resistance and creep resistance. Al-Si-Cu-Mg cast aluminum alloy has become a widely used alloy system in aluminum alloys due to its good mechanical properties, casting properties, and thermal conductivity, and is in wide demand in fields such as aerospace, automobiles, ships, and weapons. However, for the current traditional Al-Si-Cu-Mg cast aluminum alloy, its main strengthening phases Al2Cu, Mg2Si, and Q-Al5Cu2Mg8Si6 can only improve the room-temperature strength. When the temperature is above 170°C, the strengthening phases transform from metastable phases to stable phases with an incoherent structure and coarsen or even dissolve, resulting in a significant decline in mechanical properties, and it is difficult to meet the harsh requirements such as high temperature resistance, thermal stability, and high specific strength in these fields.

[0003] In terms of improving the high-temperature performance of Al-Si-Cu-Mg cast aluminum alloy, the following several methods are mainly adopted at present: (1) Microalloying. Microalloying is an important means to improve the high-temperature performance of Al-Si-Cu-Mg cast aluminum alloy. It mainly adds appropriate amounts of transition metal elements (such as Cr, Ti, V, Mn, Zr, Mo, etc.) or rare earth elements (such as Sc, Y, Ce, La, etc.) to the alloy to increase the matrix solid solubility, reduce the stacking fault energy, and generate a second phase with a high melting point, high density, high hardness, and good thermal stability, thereby significantly improving the mechanical properties of the alloy. However, some rare earth elements are difficult to be applied in large-scale industrial production due to their high prices; (2) Optimizing the heat treatment process. An excellent heat treatment process can eliminate the casting internal stress of Al-Si-Cu-Mg cast aluminum alloy, make the alloy tissue composition uniform, enhance the alloy dimensional stability, precipitate a microstructure with good thermal stability, low solubility, low diffusivity, and good combination with the matrix at high temperatures, and play a dispersion strengthening role, thereby effectively improving the high-temperature performance of the alloy; (3) Optimizing the casting process. Through the optimization of the casting process, high-quality castings can be obtained, the stability of the casting process can be improved, the casting cost can be reduced, and the performance and service life of the castings can be enhanced.

[0004] Patent CN115261681A discloses a heat-resistant rare earth aluminum alloy material. In the alloy, Si, Cu, Mg, Mn, Ni, Fe, Ti, Sm, and Y or Y-based mixed rare earth elements are added in a reasonable proportion. The as-cast material obtained is subjected to T6 heat treatment: solution temperature 545 °C, time 10 h; aging temperature 200 °C, time 8 h. This heat treatment method improves the comprehensive mechanical properties of the alloy. The tensile strength of the alloy at room temperature is 285 MPa, the yield strength is 172 MPa, and the elongation is 3%; the tensile strength at 300 °C is 150 MPa, the yield strength is 99 MPa, and the elongation is 13%. However, the improvement in the mechanical properties of the alloy, especially the high-temperature properties, is limited, and there is still room for further improvement.

[0005] Patent CN110129631A discloses a high-strength and tough heat-resistant aluminum alloy material for internal combustion engines. Elements such as Si, Cu, Mg, Fe, Ni, Cr, Ti, La, Ce, and Sc are added to the alloy in a certain proportion. The obtained aluminum alloy material has high strength and toughness, high thermal fatigue resistance, and high thermal stability. The tensile strength of the alloy at room temperature is 336 MPa, and the elongation is 2%; the tensile strength at 350 °C is 112 MPa, and the elongation is 8%; the tensile strength at 425 °C is 62 MPa, and the elongation is 10%; the rotary bending fatigue strength at 350 °C reaches 53 MPa. However, due to the relatively high cost of the rare earth element Sc, the material cost is high, and it is not suitable for large-scale industrial production.

[0006] In view of this, considering comprehensively from the aspects of the high-temperature properties and production cost of the material, it is urgent to develop a cast aluminum alloy material with excellent comprehensive mechanical properties and low cost under high-temperature environments, especially above 300 °C, to solve the problems of insufficient high-temperature properties and high cost of existing Al-Si-Cu-Mg cast aluminum alloys. Summary of the Invention

[0007] The purpose of the present invention is to solve the deficiencies existing in the prior art and propose a low-cost cast aluminum alloy suitable for high-temperature use and its preparation method.

[0008] To achieve the above purpose, the present invention adopts the following technical solutions:

[0009] A low-cost cast aluminum alloy suitable for high-temperature use and its preparation method, including alloy components with the following mass percentages: Si: 9%, Cu: 1%, Mg: 0.5%, Fe: 0.3%, Cr: 0.2%, Ti: 0.32%, V: 0.2%, Mn: 0.2%, Zr: 0.1%, Mo: 0.2%, Sr: 0.008%, the total amount of other impurities ≤ 0.1%, and the balance is Al.

[0010] Preferably, the raw materials for obtaining alloy components are Al, Mg, Al-30%Si, Al-50%Cu, Al-10%Cr, Al-10%Ti, Al-10%V, Al-10%Mn, Al-5%Zr, Al-5%Mo, Al-5%Ti-1%B, Al-10%Sr master alloy, 4 g of C2Cl6 refining agent and 3.5 g of drossing agent.

[0011] Furthermore, the raw materials of each element are specified, which facilitates accurate acquisition and ensures the precise supply of raw materials.

[0012] Preferably, the purity of the Al is 99.70% and the purity of the Mg is 99.99%.

[0013] Furthermore, the quality of the basic raw materials is ensured.

[0014] The present invention also provides a method for preparing a low-cost cast aluminum alloy suitable for high-temperature use, comprising the following steps:

[0015] S1. Batching: Set the corresponding preparation quality, and based on the preparation quality, perform proportioning, and weigh the corresponding raw materials according to the chemical composition and mass percentage content of the alloy to be prepared.

[0016] S2. Drying: Place the weighed Al-30%Si, Al-50%Cu, Al-10%Mg, Al-10%Cr, Al-10%Ti, Al-10%V, Al-10%Mn, Al-5%Zr, Al-5%Mo, Al-5%Ti-1%B, Al-10%Sr master alloy, C2Cl6 refining agent and drossing agent in a drying furnace for drying.

[0017] S3. Melting: Melt the raw materials and perform slag skimming operation.

[0018] S4. Detection: Take samples from the furnace for composition detection, and continuously adjust the addition amounts of various raw materials until the error between the measured composition and the composition of the invented alloy is less than 0.1 wt%.

[0019] S5. Casting: Cool the aluminum melt to 720 °C, pour it into a metal mold, and cool it to room temperature in the air to obtain an as-cast aluminum alloy material.

[0020] S6. Heat treatment: First, place the obtained as-cast material in an environment of 500 °C for 4 h, then place it in an environment of 550 °C for 5 h, and then immediately perform quenching in warm water at 60 °C; after quenching, first place the material in an environment of 10 °C for 3 h, then place it in an environment of 190 °C for 7 h, and finally take it out and air-cool.

[0021] Preferably, the drying temperature of the drying furnace in S2 is 150 °C, and the operating time of the drying furnace is 1.5 h.

[0022] Preferably, the melting in S3 includes the following steps:

[0023] In the first step, the weighed pure Al, Al-30%Si, and Al-50%Cu master alloys are placed in a graphite crucible in an electromagnetic induction melting furnace and heated to 730 °C.

[0024] In the second step, after the alloy is completely melted, dried pure Mg is added.

[0025] In the third step, subsequently, the temperature of the aluminum melt is adjusted to 740 °C, dried C2Cl6 refining agent and slagging agent are added, kept warm and static for 5 min, and the first slag skimming is carried out.

[0026] In the fourth step, the temperature of the aluminum melt is continuously raised to 800 °C, dried Al-10%Cr, Al-10%Ti, Al-10%V, Al-10%Mn, Al-5%Zr, and Al-5%Mo master alloys are added, and electromagnetic stirring is applied simultaneously.

[0027] In the fifth step: after the stirring is completed, the temperature of the aluminum melt is adjusted to 740 °C, dried grain refiner Al-5%Ti-1%B and modifier Al-10%Sr are added, kept warm and static for 5 min.

[0028] In the sixth step: dried C2Cl6 refining agent and slagging agent are added, kept warm and static for 5 min, and the second slag skimming is carried out.

[0029] Preferably, the metal mold in S5 is at 200 °C.

[0030] Preferably, the electromagnetic stirring frequency is 10 - 15 Hz, and the stirring time is 3 - 5 min.

[0031] Preferably, the heat treatment in S6 adopts a two-stage solution + two-stage aging heat treatment method, and its specific method is: solution treatment: the as-cast specimen is kept warm at 500 °C for 4 h, then placed in an environment of 540 - 550 °C and kept warm for 4 - 5 h, and then immediately quenched in warm water at 50 - 60 °C; two-stage aging: the specimen after solution treatment is kept warm at 100 °C for 3 h, then placed in an environment of 180 - 200 °C and kept warm for 7 - 9 h, and then taken out and air-cooled.

[0032] The beneficial effects of the present invention are:

[0033] 1. The present invention discloses a low-cost Al-Si-Cu-Mg cast aluminum alloy suitable for use at 300°C high temperature and its preparation method. The composition is optimized mainly by compounding and adding six transition metal elements (Cr, Ti, V, Mn, Zr, Mo) to the Al-Si-Cu-Mg base alloy. The various transition metal intermediate phases generated are stable at high temperatures, greatly improving the high-temperature performance of the alloy;

[0034] 2. The preparation process disclosed by the present invention is simple and easy to implement, convenient to operate, with excellent high-temperature performance of the material and low cost, suitable for large-scale industrial production, and has very great application prospects in the fields of aerospace, automobiles, ships, weapons, etc.;

[0035] 3. The alloy material prepared by the present invention appropriately increases the content of impurity Fe, reduces the material cost to a certain extent, is conducive to the recycling and reuse of waste aluminum, and the Fe-rich phase modified by the transition metal element makes a great contribution to the improvement of the high-temperature performance of the alloy;

[0036] 4. Electromagnetic stirring is applied during the melting process of the present invention, which can not only accelerate the melting speed of the alloy, but also greatly reduce element segregation, make the distribution of each element more uniform, and achieve the purpose of refining grains and improving the quality of the ingot;

[0037] 5. The alloy material prepared by the present invention can precipitate thermally stable strengthening phases with finer grains and more uniform distribution through the method of double-stage solution treatment + double-stage aging treatment, so as to obtain higher tensile strength, yield strength and elongation at fracture;

[0038] 6. The alloy material prepared by the present invention has excellent comprehensive mechanical properties at room temperature and high temperature. Taking the alloy in Example 1 as an example, at room temperature, the tensile strength is: 376 MPa, the yield strength is: 330 MPa, and the elongation at fracture is: 5.0%; at 300°C high temperature, the tensile strength is: 175 MPa, the yield strength is: 167 MPa, and the elongation at fracture is: 8.7%;

[0039] In summary: The present invention comprehensively considers the high-temperature performance and production cost of the material. The composition is optimized mainly by compounding and adding six transition metal elements (Cr, Ti, V, Mn, Zr, Mo) to the Al-Si-Cu-Mg base alloy, and by applying electromagnetic stirring and optimizing the heat treatment process, a cast aluminum alloy material with excellent comprehensive mechanical properties and low cost in a high-temperature environment, especially above 300°C, is developed to solve the problems of insufficient high-temperature performance and high cost of existing Al-Si-Cu-Mg cast aluminum alloys. Brief Description of the Drawings

[0040] Figure 1 It is a step diagram of a preparation method of a low-cost cast aluminum alloy suitable for high-temperature use proposed by the present invention;

[0041] Figure 2 The melting step diagram of a low-cost cast aluminum alloy suitable for high-temperature use and its preparation method proposed by the present invention;

[0042] Figure 3 The microstructure diagrams of the alloys prepared in Examples 1-3 of the present invention;

[0043] Figure 4 The mechanical property diagrams of the alloys and the base alloy in Examples 1-3 of the present invention. Detailed implementation manners

[0044] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments.

[0045] Refer to Figures 1-4 A low-cost cast aluminum alloy suitable for high-temperature use includes alloy components with the following mass percentages: Si: 9%, Cu: 1%, Mg: 0.5%, Fe: 0.3%, Cr: 0.2%, Ti: 0.32%, V: 0.2%, Mn: 0.2%, Zr: 0.1%, Mo: 0.2%, Sr: 0.008%, the total amount of other impurities ≤ 0.1%, and the balance is Al. The raw materials for obtaining the alloy components are Al, Mg, Al-30%Si, Al-50%Cu, Al-10%Cr, Al-10%Ti, Al-10%V, Al-10%Mn, Al-5%Zr, Al-5%Mo, Al-5%Ti-1%B, Al-10%Sr master alloys, 4 g of C2Cl6 refining agent and 3.5 g of slagging agent. The purity of Al is 99.70%, and the purity of Mg is 99.99%.

[0046] Example 1

[0047] The alloy components and their corresponding mass percentages in this example are: Si: 9%, Cu: 1%, Mg: 0.5%, Fe: 0.3%, Cr: 0.2%, Ti: 0.32%, V: 0.2%, Mn: 0.2%, Zr: 0.1%, Mo: 0.2%, Sr: 0.008%, the total amount of other impurities ≤ 0.1%, and the balance is Al.

[0048] The specific preparation process of the above alloy is as follows:

[0049] (1) Ingredients: The raw materials were weighed according to the chemical composition and mass percentage of the pre-prepared alloy, including pure Al (99.70%), pure Mg (99.99%), and Al-30%Si, Al-50%Cu, Al-10%Cr, Al-10%Ti, Al-10%V, Al-10%Mn, Al-5%Zr, Al-5%Mo, Al-5%Ti-1%B, Al-10%Sr master alloys, as well as 4g of C2Cl6 refining agent and 3.5g of slag remover.

[0050] (2) Drying: Place the weighed Al-30%Si, Al-50%Cu, Al-10%Mg, Al-10%Cr, Al-10%Ti, Al-10%V, Al-10%Mn, Al-5%Zr, Al-5%Mo, Al-5%Ti-1%B, Al-10%Sr master alloys, C2Cl6 refining agent and slag remover in a drying furnace at 150°C and dry for 1.5 h;

[0051] (3) Melting: The weighed pure Al, Al-30% Si, and Al-50% Cu master alloys were placed in a graphite crucible in an electromagnetic induction melting furnace and heated to 730°C. After the alloy was completely melted, dried pure Mg was added. The aluminum melt temperature was then adjusted to 740°C, and dried C2Cl6 refining agent and slag remover were added. The mixture was kept warm and allowed to stand for 5 minutes before the first slag removal. The aluminum melt temperature was further raised to 800°C, and dried Al-10% Cr, Al-10% Ti, Al-10% V, Al-10% Mn, Al-5% Zr, and Al-5% Mo master alloys were added while electromagnetic stirring was applied. After stirring, the aluminum melt temperature was adjusted to 740°C, and dried refiner Al-5% Ti-1% B and modifier Al-10% Sr were added. The mixture was kept warm and allowed to stand for 5 minutes. Finally, add the dried C2Cl6 refining agent and slag remover, keep warm and let it stand for 5 minutes, and then carry out the second slag removal;

[0052] (4) Testing: Samples are taken from the furnace for composition testing, and the amount of raw materials added is continuously adjusted until the error between the measured composition and the composition of the invented alloy is less than 0.1 wt%;

[0053] (5) Casting: The aluminum melt is further cooled to 720°C, poured into a metal mold preheated to 200°C, and cooled to room temperature in air to obtain an aluminum alloy cast material;

[0054] (6) Heat treatment: The as-cast material obtained is first kept at 500 °C for 4 h, then at 550 °C for 5 h, and then immediately quenched in warm water at 60 °C; after quenching, the material is first kept at 100 °C for 3 h, then at 190 °C for 7 h, and finally taken out for air cooling.

[0055] For the aluminum alloy material prepared in this example, the tensile strength at room temperature is: 376 MPa, the yield strength is: 330 MPa, and the elongation at the fracture is: 5.0%; the tensile strength at 300 °C is: 175 MPa, the yield strength is: 167 MPa, and the elongation at the fracture is: 8.7%.

[0056] Example 2

[0057] The alloy components and their corresponding mass percentages in this example are the same as those in Example 1.

[0058] The specific preparation process of the above alloy is as follows:

[0059] (1) The batching process is the same as that in Example 1;

[0060] (2) The drying process is the same as that in Example 1;

[0061] (3) The melting process is the same as that in Example 1;

[0062] (4) The detection process is the same as that in Example 1;

[0063] (5) The casting process is the same as that in Example 1;

[0064] (6) Heat treatment: The as-cast material obtained is first kept at 500 °C for 4 h, then at 550 °C for 4 h, and then immediately quenched in warm water at 60 °C; after quenching, the material is first kept at 100 °C for 3 h, then at 190 °C for 7 h, and finally taken out for air cooling.

[0065] For the aluminum alloy material prepared in this example, the tensile strength at room temperature is: 369 MPa, the yield strength is: 323 MPa, and the elongation at the fracture is: 4.3%; the tensile strength at 300 °C is: 165 MPa, the yield strength is: 158 MPa, and the elongation at the fracture is: 7.9%.

[0066] Example 3

[0067] The alloy components and their corresponding mass percentages in this example are the same as those in Example 1.

[0068] The specific preparation process of the above alloy is as follows:

[0069] (1) The batching process is the same as that in Example 1;

[0070] (2) The drying process is the same as that in Example 1;

[0071] (3) The smelting process is the same as that in Example 1;

[0072] (4) The detection process is the same as that in Example 1;

[0073] (5) The casting process is the same as that in Example 1;

[0074] (6) Heat treatment: The as-cast material obtained is first kept at 500 °C for 4 h, then at 540 °C for 5 h, and then immediately quenched in warm water at 60 °C; after quenching, the material is first kept at 100 °C for 3 h, then at 190 °C for 7 h, and finally taken out and air-cooled.

[0075] For the aluminum alloy material prepared in this example, the tensile strength at room temperature is: 373 MPa, the yield strength is: 326 MPa, and the elongation at the fracture is: 4.7%; the tensile strength at 300 °C is: 171 MPa, the yield strength is: 164 MPa, and the elongation at the fracture is: 8.4%.

[0076] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution of the present invention and its inventive concept, makes equivalent substitutions or changes, and all should be covered by the protection scope of the present invention.

Claims

1. A low-cost cast aluminum alloy suitable for high-temperature use, comprising alloy components with the following mass percentages: Si: 9%, Cu: 1%, Mg: 0.5%, Fe: 0.3%, Cr: 0.2%, Ti: 0.32%, V: 0.2%, Mn: 0.2%, Zr: 0.1%, Mo: 0.2%, Sr: 0.008%, the total amount of other impurities ≤ 0.1%, and the balance is Al. At room temperature, the tensile strength is: 376 MPa, the yield strength is: 330 MPa, and the elongation at the fracture is: 5.0%; at 300 °C high temperature, the tensile strength is: 175 MPa, the yield strength is: 167 MPa, and the elongation at the fracture is: 8.7%.

2. A low-cost cast aluminum alloy suitable for high-temperature use according to claim 1, characterized in that: The raw materials for obtaining the alloy components are Al, Mg, Al-30%Si, Al-50%Cu, Al-10%Cr, Al-10%Ti, Al-10%V, Al-10%Mn, Al-5%Zr, Al-5%Mo, Al-5%Ti-1%B, Al-10%Sr master alloys, as well as 4 g of C2Cl6 refining agent and 3.5 g of drossing agent.

3. A low-cost cast aluminum alloy suitable for high-temperature use according to claim 2, characterized in that: The purity of the Al is 99.70%, and the purity of the Mg is 99.99%.

4. The preparation method of a low-cost cast aluminum alloy suitable for high-temperature use according to claim 2, characterized in that: It includes the following steps: S1. Batching: Set the corresponding preparation mass and make a ratio based on the preparation mass. Weigh the corresponding raw materials according to the chemical composition and mass percentage of the alloy to be prepared. S2. Drying: Place the weighed Al-30%Si, Al-50%Cu, Al-10%Mg, Al-10%Cr, Al-10%Ti, Al-10%V, Al-10%Mn, Al-5%Zr, Al-5%Mo, Al-5%Ti-1%B, Al-10%Sr master alloys, as well as the C2Cl6 refining agent and the drossing agent in a drying furnace for drying. S3. Melting: Melt the raw materials and perform slag skimming operations. S4. Detection: Take samples from the furnace for composition detection, and continuously adjust the addition amounts of various raw materials until the error between the measured composition and the composition of the alloy is less than 0.1 wt%. S5. Casting: Cool the aluminum melt down to 720 °C and pour it into a metal mold, and cool it to room temperature in the air to obtain the as-cast aluminum alloy material. S6. Heat treatment: First, place the obtained as-cast material in an environment of 500 °C for 4 h, then place it in an environment of 550 °C for 5 h, and then immediately quench it in 60 °C warm water; after quenching, first place the material in an environment of 100 °C for 3 h, then place it in an environment of 190 °C for 7 h, and finally take it out and air-cool it.

5. The preparation method of a low-cost cast aluminum alloy suitable for high-temperature use according to claim 4, characterized in that: In S2, the drying temperature of the drying furnace is 150 °C, and the operating time of the drying furnace is 1.5 h.

6. The preparation method of a low-cost cast aluminum alloy suitable for high-temperature use according to claim 4, characterized in that: The melting in S3 includes the following steps: The first step is to put the weighed pure Al, Al-30%Si, and Al-50%Cu master alloys into a graphite crucible in an electromagnetic induction melting furnace for heating, and raise the temperature to 730 °C. The second step: After the alloy is completely melted, add the dried pure Mg. Step 3: Subsequently, adjust the temperature of the aluminum melt to 740 °C, add the dried C2Cl6 refining agent and drossing agent, hold for 5 min with insulation, and perform the first slag skimming. Step 4: Continue to raise the temperature of the aluminum melt to 800 °C, add the dried master alloys of Al-10%Cr, Al-10%Ti, Al-10%V, Al-10%Mn, Al-5%Zr, and Al-5%Mo, and apply electromagnetic stirring simultaneously. Step 5: After the stirring is completed, adjust the temperature of the aluminum melt to 740 °C, add the dried grain refiner Al-5%Ti-1%B and modifier Al-10%Sr, and hold for 5 min with insulation. Step 6: Add the dried C2Cl6 refining agent and drossing agent, hold for 5 min with insulation, and perform the second slag skimming.

7. The preparation method of a low-cost cast aluminum alloy suitable for high-temperature use according to claim 4, characterized in that: The metal mold in S5 is at 200 °C.

8. The preparation method of a low-cost cast aluminum alloy suitable for high-temperature use according to claim 6, characterized in that: The electromagnetic stirring frequency is 10 - 15 Hz, and the stirring time is 3 - 5 min.

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