High-toughness metamorphic hypereutectic aluminum-silicon-copper alloy and preparation method thereof

Abstract

The invention relates to a high-toughness metamorphic hypereutectic aluminum-silicon-copper alloy and a preparation method thereof, and the hypereutectic aluminum-silicon-copper alloy comprises the following components in percentage by weight: 16-20% of Si, 4-6% of Cu, and Filt. 1.3%, Znlt; , 1.5%, Mglt; 0.6%, Mn < lt >; the content is 0.5%, and the content is Nilt; %, 0.3%, Tilt; the aluminum alloy comprises the following components in percentage by weight: 0.3% of Sr, 0.03-0.18% of Sr, 0.01-0.06% of Er and the balance A trace Sr + Er composite modification and high-temperature smelting method is adopted, so that the organization structure of the hypereutectic aluminum-silicon-copper alloy is effectively refined, the morphology of primary silicon and the morphology of eutectic silicon are obviously improved, and the mechanical property of the hypereutectic aluminum-silicon-copper alloy is obviously improved. In the modification method disclosed by the invention, the addition amount of the rare earth Er element is extremely low (less than or equal to 0.06%), but the modification effect is obvious, the modification process is simple and stable, the modification cost of the hypereutectic aluminum-silicon-copper alloy can be effectively reduced, and the application occasion of the hypereutectic aluminum-silicon-copper alloy is expanded.

Description

Technical Field

[0001] The invention belongs to the technical field of materials and preparation, and relates to the modification of a hypereutectic aluminum-silicon-copper alloy and a preparation method thereof. Background Art

[0002] Hypereutectic aluminum-silicon-copper alloys are widely used in wear-resistant and heat-resistant parts such as automobile engine pistons, compressors, and transmission parts due to their good heat resistance and wear resistance, low thermal expansion coefficient, excellent casting performance, and high specific strength. However, due to the excessively high silicon content (generally 16-20%), there are a large number of coarse and irregular blocky primary silicon and needle-shaped eutectic silicon in the organization of hypereutectic aluminum-silicon-copper alloys, which will seriously split the matrix, cause stress concentration, and damage the strength and plasticity of the hypereutectic aluminum-silicon-copper alloy, which is not conducive to the application of hypereutectic aluminum-silicon-copper alloys in industrial wear-resistant and heat-resistant parts such as automobile engine pistons and compressors. Therefore, effectively refining the primary silicon and eutectic silicon in hypereutectic aluminum-silicon-copper alloys and improving their mechanical properties are key issues that need to be solved urgently, which is of great significance for the industrial application of hypereutectic aluminum-silicon-copper alloys.

[0003] At present, in order to solve the problem of coarse primary silicon and eutectic silicon in hypereutectic aluminum-silicon-copper alloy, there are related technologies to modify and refine primary silicon and eutectic silicon by adding P elements, rare earth elements, Al-Ti-B refiners, etc., so as to improve the mechanical properties of the alloy. For example, in patent: CN113549793A, 0.3~0.4% Cu-P master alloy and 0.3~0.5% rare earth (La-Ce) are used to modify the hypereutectic Al-Si-Cu alloy. After modification, the size of primary silicon is refined from 140 μm to 55 μm, the eutectic silicon is in the shape of short rods, and the tensile strength of the cast alloy is increased from 126MPa before modification to 167MPa. Patent: CN107326228B modifies the hypereutectic Al-Si alloy by adding 0.1~0.8% Al-5Ti-1B and 0.2~1.0% rare earth ytterbium. The size of the primary silicon after modification is about 41 μm, and the eutectic silicon is short rod-shaped. Patent: CN106521260B modifies the hypereutectic Al-Si alloy by using 0.8%~1.2% mixed rare earth (Pr+Y). After modification, the size of the primary silicon is reduced from 96 μm before modification to 41 μm, and the eutectic silicon changes from needle-like to vermicular. The tensile strength and elongation of the cast alloy are increased from 93MPa and 1.12% before modification to 143MPa and 2.79%, respectively. Although relevant technologies have proposed solutions for the refinement of primary silicon and eutectic silicon in hypereutectic aluminum-silicon alloys and effectively improved the mechanical properties, there are still problems such as insufficient modification effect (eutectic silicon is not refined into tiny particles) and large amount of rare earth addition. High addition of rare earth will cause a sharp increase in production costs (the market price of common rare earth elements is 200-1500 yuan / kg). Therefore, it is still necessary to further develop a method with excellent modification effect and low cost to meet the demand for high-quality, low-cost hypereutectic aluminum-silicon-copper alloys in industrial applications. Summary of the invention

[0004] The purpose of the present invention is to provide a high-strength and tough modified hypereutectic aluminum-silicon-copper alloy and a preparation method thereof, in order to address the problems that the existing hypereutectic aluminum-silicon-copper alloy has insufficient modification effect and a high amount of rare earth added leading to increased production costs. The alloy has the characteristics of significant modification effect and low modification cost.

[0005] The present invention is achieved through the following technical solutions.

[0006] The high-strength and toughness modified hypereutectic aluminum-silicon-copper alloy described in the present invention is characterized in that, based on the total weight of the high-strength and toughness modified hypereutectic aluminum-silicon-copper alloy, it contains the following components in mass percentage: Si: 16-20%, Cu: 4-6%, Fe<1.3%, Zn<1.5%, Mg<0.6%, Mn<0.5%, Ni<0.3%, Ti<0.3%, Sr: 0.03%~0.18%, Er: 0.01%~0.06%, and the balance is Al.

[0007] Preferably, the addition ratio of Sr and rare earth element Er is 3:1.

[0008] The method for preparing a high-strength and toughness modified hypereutectic aluminum-silicon-copper alloy described in the present invention is characterized by comprising the following steps.

[0009] S1: Melt the hypereutectic aluminum-silicon-copper alloy to obtain aluminum liquid, and control the temperature of the aluminum liquid to be superheated to 850~900℃.

[0010] S2: Add Al-Sr master alloy and Al-Er master alloy to the superheated aluminum liquid and keep it warm for 25-30 min. During the insulation process, stir it gently with a graphite rod for 1 min every 10 min.

[0011] S3: After the insulation is completed, the furnace temperature is controlled to drop, and argon gas is introduced for refining. After the temperature is lowered, the slag on the surface of the aluminum liquid is removed, and the aluminum liquid is poured into a mold for solidification to obtain a high-strength and tough hypereutectic aluminum-silicon-copper alloy.

[0012] Preferably, in step S3, the cooling target temperature in the cooling process is 700°C, and the cooling rate is 15-20°C / min.

[0013] Preferably, in step S3, the mold is an iron mold or a copper mold.

[0014] Compared with the prior art, the invention has the following beneficial effects.

[0015] (1) The present invention provides a high-strength and toughness modified hypereutectic Al-Si-Cu alloy and a preparation method thereof, which can give full play to the significant modification effect of Sr and rare earth elements Er on primary silicon and eutectic silicon in the hypereutectic Al-Si-Cu alloy, and effectively improve the modification effect and further inhibit the growth of primary silicon by increasing the melt temperature, so that both eutectic silicon and primary silicon are effectively refined, thereby greatly improving the mechanical properties of the hypereutectic Al-Si-Cu alloy. The high-strength and toughness modified hypereutectic aluminum-silicon-copper alloy of the present invention has a primary silicon size reduced from ~65 μm before modification to ~35 μm, the eutectic silicon changes from coarse needles to point particles, the tensile strength is increased from 126.05 MPa before modification to 191.61 MPa, the specified plastic extension strength (Rp0.2) is increased from 63.39 MPa before modification to 128.63 MPa, the elongation is increased from 0.28% before modification to 0.74%, and the micro-Vickers hardness is increased from 123.15 HV before modification to 135.72 HV.

[0016] (2) The present invention can give full play to the powerful modification effect of Sr and rare earth Er elements on hypereutectic aluminum-silicon-copper alloy under trace addition (rare earth Er addition amount ≤ 0.06%), significantly improve the mechanical properties of hypereutectic aluminum-silicon-copper alloy, and the addition of extremely low rare earth Er elements can reduce the modification cost of hypereutectic aluminum-silicon-copper alloy. Under the addition amount of Sr and rare earth Er of the present invention, the industrial application cost of hypereutectic aluminum-silicon-copper alloy only increases by 300-500 yuan / ton (the market price of Al-Sr alloy is 20-100 yuan / kg, and the market price of Al-Er alloy is 200-300 yuan / kg). Compared with other high-addition rare earth modification methods, the cost can be reduced by 40%, which helps to meet the demand for high-quality, low-cost hypereutectic aluminum-silicon-copper alloy in industrial applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is the microstructure diagram of the hypereutectic aluminum-silicon-copper alloy material obtained in Example 1.

[0018] Figure 2 This is the microstructure diagram of the hypereutectic aluminum-silicon-copper alloy material obtained in Example 2.

[0019] Figure 3 This is the microstructure diagram of the hypereutectic aluminum-silicon-copper alloy material obtained in Example 3.

[0020] Figure 4 This is the microstructure diagram of the hypereutectic aluminum-silicon-copper alloy material obtained in Example 4.

[0021] Figure 5 This is the microstructure diagram of the hypereutectic aluminum-silicon-copper alloy material obtained in Comparative Example 1.

[0022] Figure 6This is the microstructure diagram of the hypereutectic aluminum-silicon-copper alloy material obtained in Comparative Example 2.

[0023] Figure 7 This is the microstructure diagram of the hypereutectic aluminum-silicon-copper alloy material obtained in Comparative Example 3.

[0024] Figure 8 This is the microstructure diagram of the hypereutectic aluminum-silicon-copper alloy material obtained in Comparative Example 4. DETAILED DESCRIPTION

[0025] The present invention is further described below in conjunction with embodiments. The description of the embodiments is only for facilitating the understanding and application of the present invention, but not for limiting the protection of the present invention. Example 1

[0026] Embodiment 1 provides a high-strength and toughness modified hypereutectic aluminum-silicon-copper alloy. The element composition of the high-strength and toughness hypereutectic aluminum-silicon-copper alloy material of this embodiment is as follows by mass percentage: Si: 17%, Cu: 4.5%, Fe: 0.5%, Zn: 0.7%, Mg: 0.6%, Mn: 0.2%, Ni: 0.01%, Ti: 0.01%, Sr: 0.09%, Er: 0.03%, and the balance is Al. The preparation method thereof comprises the following steps.

[0027] S1: Melting the hypereutectic aluminum-silicon-copper alloy to obtain aluminum liquid, and controlling the temperature of the aluminum liquid to be superheated to 900°C.

[0028] S2: Add Al-Sr master alloy and Al-Er master alloy to the superheated aluminum liquid and keep it warm for 30 min. During the insulation process, stir it gently with a graphite rod for 1 min every 10 min.

[0029] S3: After the insulation is completed, the furnace temperature is controlled to drop to 700°C, and the cooling rate is 20°C / min. Argon gas is introduced during the cooling process for refining. After the cooling is completed, the slag on the surface of the aluminum liquid is removed, and the aluminum liquid is poured into an iron mold and a copper mold for solidification to obtain a high-strength and tough hypereutectic aluminum-silicon-copper alloy. Example 2

[0030] Embodiment 2 provides a high-strength and toughness modified hypereutectic aluminum-silicon-copper alloy. The element composition of the high-strength and toughness hypereutectic aluminum-silicon-copper alloy material of this embodiment is as follows by mass percentage: Si: 17%, Cu: 4.5%, Fe: 0.5%, Zn: 0.7%, Mg: 0.6%, Mn: 0.2%, Ni: 0.01%, Ti: 0.01%, Sr: 0.135%, Er: 0.045%, and the balance is Al. The preparation method thereof comprises the following steps.

[0031] S1: Melting the hypereutectic aluminum-silicon-copper alloy to obtain aluminum liquid, and controlling the temperature of the aluminum liquid to be superheated to 900°C.

[0032] S2: Add Al-Sr master alloy and Al-Er master alloy to the superheated aluminum liquid and keep it warm for 30 minutes. During the insulation process, stir it gently with a graphite rod for 1 minute every 10 minutes.

[0033] S3: After the insulation is completed, the furnace temperature is controlled to drop to 700°C, and the cooling rate is 20°C / min. Argon gas is introduced during the cooling process for refining. After the cooling is completed, the slag on the surface of the aluminum liquid is removed, and the aluminum liquid is poured into an iron mold and a copper mold for solidification to obtain a high-strength and tough hypereutectic aluminum-silicon-copper alloy. Example 3

[0034] Embodiment 3 provides a high-strength and toughness modified hypereutectic aluminum-silicon-copper alloy. The element composition of the high-strength and toughness hypereutectic aluminum-silicon-copper alloy material of this embodiment is as follows by mass percentage: Si: 17%, Cu: 4.5%, Fe: 0.5%, Zn: 0.7%, Mg: 0.6%, Mn: 0.2%, Ni: 0.01%, Ti: 0.01%, Sr: 0.18%, Er: 0.06%, and the balance is Al. The preparation method thereof comprises the following steps.

[0035] S1: Melting the hypereutectic aluminum-silicon-copper alloy to obtain aluminum liquid, and controlling the temperature of the aluminum liquid to be superheated to 900°C.

[0036] S2: Add Al-Sr master alloy and Al-Er master alloy to the superheated aluminum liquid and keep it warm for 30 minutes. During the insulation process, stir it gently with a graphite rod for 1 minute every 10 minutes.

[0037] S3: After the insulation is completed, the furnace temperature is controlled to drop to 700°C, and the cooling rate is 20°C / min. Argon gas is introduced during the cooling process for refining. After the cooling is completed, the slag on the surface of the aluminum liquid is removed, and the aluminum liquid is poured into an iron mold and a copper mold for solidification to obtain a high-strength and tough hypereutectic aluminum-silicon-copper alloy. Example 4

[0038] Embodiment 4 provides a high-strength and toughness modified hypereutectic aluminum-silicon-copper alloy. The element composition of the high-strength and toughness hypereutectic aluminum-silicon-copper alloy material of this embodiment is as follows by mass percentage: Si: 17%, Cu: 4.5%, Fe: 0.5%, Zn: 0.7%, Mg: 0.6%, Mn: 0.2%, Ni: 0.01%, Ti: 0.01%, Sr: 0.18%, Er: 0.06%, and the balance is Al. The preparation method thereof comprises the following steps.

[0039] S1: Melting the hypereutectic aluminum-silicon-copper alloy to obtain aluminum liquid, and controlling the temperature of the aluminum liquid to be superheated to 850°C.

[0040] S2: Add Al-Sr master alloy and Al-Er master alloy to the superheated aluminum liquid and keep it warm for 30 minutes. During the insulation process, stir it gently with a graphite rod for 1 minute every 10 minutes.

[0041] S3: After the insulation is completed, the furnace temperature is controlled to drop to 700°C, and the cooling rate is 15°C / min. Argon gas is introduced during the cooling process for refining. After the cooling is completed, the slag on the surface of the aluminum liquid is removed, and the aluminum liquid is poured into an iron mold and a copper mold for solidification to obtain a high-strength and tough hypereutectic aluminum-silicon-copper alloy.

[0042] Comparative example 1.

[0043] Compared with Example 4, the difference of Comparative Example 1 is that the superheating temperature of the aluminum liquid in Preparation Method S1 is 800°C.

[0044] Calculated by mass percentage, the content of Sr element added in this comparative example is 0.18%, the content of Er element added is 0.06%, and the element composition of the high strength and toughness hypereutectic aluminum-silicon-copper alloy material prepared in this comparative example is: Si: 17%, Cu: 4.5%, Fe: 0.5%, Zn: 0.7%, Mg: 0.6%, Mn: 0.2%, Ni: 0.01%, Ti: 0.01%, Sr: 0.18%, Er: 0.06%, and the balance is Al.

[0045] Comparative example 2.

[0046] Compared with Example 4, the difference of Comparative Example 2 is that the superheating temperature of the aluminum liquid in Preparation Method S1 is 750°C.

[0047] Calculated by mass percentage, the content of Sr element added in this comparative example is 0.18%, the content of Er element added is 0.06%, and the element composition of the high strength and toughness hypereutectic aluminum-silicon-copper alloy material prepared in this comparative example is: Si: 17%, Cu: 4.5%, Fe: 0.5%, Zn: 0.7%, Mg: 0.6%, Mn: 0.2%, Ni: 0.01%, Ti: 0.01%, Sr: 0.18%, Er: 0.06%, and the balance is Al.

[0048] Comparative example 3.

[0049] Compared with Example 4, the difference of Comparative Example 3 is that the superheat temperature of the aluminum liquid in Preparation Method S1 is 700° C., there is no cooling stage in Preparation Method S3, the argon refining time is 5 minutes after the insulation time of 25 minutes.

[0050] Calculated by mass percentage, the content of Sr element added in this comparative example is 0.18%, the content of Er element added is 0.06%, and the element composition of the high strength and toughness hypereutectic aluminum-silicon-copper alloy material prepared in this comparative example is: Si: 17%, Cu: 4.5%, Fe: 0.5%, Zn: 0.7%, Mg: 0.6%, Mn: 0.2%, Ni: 0.01%, Ti: 0.01%, Sr: 0.18%, Er: 0.06%, and the balance is Al.

[0051] Comparative example 4.

[0052] Compared with Example 4, the difference of Comparative Example 4 is that Sr and Er modifying elements are not added, the superheating temperature of the aluminum liquid in Preparation Method S1 is 900° C., and the cooling rate in Preparation Method S3 is 20° C. / min.

[0053] Calculated by mass percentage, the element composition of the high-strength and toughness hypereutectic aluminum-silicon-copper alloy material prepared in this comparative example is: Si: 17%, Cu: 4.5%, Fe: 0.5%, Zn: 0.7%, Mg: 0.6%, Mn: 0.2%, Ni: 0.01%, Ti: 0.01%, and the balance is Al.

[0054] The mechanical properties of the hypereutectic aluminum-silicon-copper alloy materials prepared in Examples 1-4 and Comparative Examples 1-4 were tested, and the specific test results are shown in Table 1 (test standards: GB / T 10623-2008, GB / T 228.1-2021).

[0055] Table 1: Mechanical properties of hypereutectic aluminum-silicon-copper alloy materials prepared in Examples 1-4 and Comparative Examples 1-4 .

[0056] The average size of primary silicon and the morphology of eutectic silicon were measured for the hypereutectic aluminum-silicon-copper alloy materials prepared in Examples 1-4 and Comparative Examples 1-4. The specific test results are shown in Table 2.

[0057] Table 2: Average size of primary silicon and morphology of eutectic silicon in hypereutectic aluminum-silicon-copper alloy materials prepared in Examples 1-4 and Comparative Examples 1-4 .

[0058] The present invention adopts a composite modification method of trace amounts of Sr and rare earth Er elements to refine and modify the primary silicon and eutectic silicon in the hypereutectic aluminum-silicon-copper alloy, and effectively improves the modification effect and further inhibits the growth of primary silicon by increasing the melt temperature, so that both the eutectic silicon and the primary silicon are significantly refined, thereby greatly improving the mechanical properties of the hypereutectic aluminum-silicon-copper alloy. It can be seen from the mechanical property data of Examples 1-3 and Comparative Example 4 in Table 1 that the composite addition of Sr and Er can still exert a strong modification effect at a low trace content, and significantly improves the mechanical properties of hypereutectic aluminum-silicon-copper. The tensile strength of the hypereutectic aluminum-silicon-copper alloy is increased from 126.05 MPa before modification to 191.61 MPa, the specified plastic elongation strength (Rp0.2) is increased from 63.39 MPa before modification to 128.63 MPa, the elongation is increased from 0.28% before modification to 0.74%, and the micro-Vickers hardness is increased from 123.15 HV before modification to 135.72 HV. It can be seen from the mechanical property data of Examples 1-4 and Comparative Examples 1-4 in Table 1 that the high melt temperature of 850-900°C can enhance the effect of the composite modification of Sr and Er elements. Under the melt temperature condition of 700-850°C, the effect of the composite modification of Sr and Er elements on improving the mechanical properties of the hypereutectic Al-Si-Cu alloy decreases as the melt temperature decreases.

[0059] The average size of the primary silicon and the morphology change results of the eutectic silicon of Examples 1-4 and Comparative Examples 1-4 are shown in Table 2, Figure 1-8 It can be seen that under the conditions of high melt temperature of 850-900℃ and Sr+Er composite modification, the size of primary silicon has been significantly refined, from ~65μm before modification to ~35μm; the morphology of eutectic silicon has also been refined from coarse needles before modification to tiny point-like particles. As the melt temperature decreases, the effect of composite modification of Sr and Er elements also weakens, but under the melt temperature of 700℃, it can still produce a good modification effect on the eutectic silicon structure of hypereutectic aluminum-silicon-copper alloy.

[0060] It can be seen that the present invention can significantly improve the mechanical properties of the hypereutectic aluminum-silicon-copper alloy by adding Sr+Er composite elements and increasing the melt temperature, and improve the toughness of the hypereutectic aluminum-silicon-copper alloy. The addition of Sr+Er elements can significantly inhibit the growth of eutectic silicon and produce a refinement effect on primary silicon. The high melt temperature can improve the refinement effect of Sr+Er elements on primary silicon and eutectic silicon. The process of rapidly cooling from high melt temperature to low temperature casting can inhibit the nucleation and growth of primary silicon, thereby improving the metamorphic effect.

[0061] The advantage of the present invention is that it can give full play to the powerful modification effect of Sr and rare earth Er elements on the hypereutectic aluminum-silicon-copper alloy under trace addition (rare earth Er addition amount ≤ 0.06%), significantly improve the mechanical properties of the hypereutectic aluminum-silicon-copper alloy, help to expand the application occasions of the hypereutectic aluminum-silicon-copper alloy, and has the characteristics of low cost, simple modification process and significant modification effect.

[0062] The above is based on the ideal embodiment of the present invention. Through the above description, relevant staff can make various modifications and changes without departing from the technical idea of ​​the present invention. However, it should be understood that such modifications and changes are within the scope and spirit of the present invention described in the claims. The technical scope of the present invention is not limited to the content of the specification, and its technical scope must be determined according to the scope of the claims.

Claims

1. A high-strength and tough modified hypereutectic aluminum-silicon-copper alloy, characterized in that: Based on the total weight of the high-strength and toughness modified hypereutectic aluminum-silicon-copper alloy, the alloy comprises the following components by mass percentage: Si: 16-20%, Cu: 4-6%, Fe<1.3%, Zn<1.5%, Mg<0.6%, Mn<0.5%, Ni<0.3%, Ti<0.3%, Sr: 0.03%~0.18%, Er: 0.01%~0.06%, and the balance is Al.

2. A high-strength and tough modified hypereutectic aluminum-silicon-copper alloy according to claim 1, characterized in that: The addition ratio of Sr and rare earth Er element is 3:

1.

3. The method for preparing a high-strength and toughness modified hypereutectic aluminum-silicon-copper alloy according to claim 1 or 2, characterized in that: The following steps are involved: S1: Melting the hypereutectic aluminum-silicon-copper alloy to obtain aluminum liquid, and controlling the temperature of the aluminum liquid to be superheated to 850-900°C; S2: Add Al-Sr master alloy and Al-Er master alloy to the superheated aluminum liquid, keep warm for 25-30 min, and stir lightly with a graphite rod for 1 min every 10 min during the heat preservation process; S3: After the insulation is completed, the furnace temperature is controlled to drop, and argon gas is introduced for refining. After the temperature is lowered, the slag on the surface of the aluminum liquid is removed, and the aluminum liquid is poured into a mold for solidification to obtain a high-strength and tough hypereutectic aluminum-silicon-copper alloy.

4. The method for preparing a high-strength and toughness modified hypereutectic aluminum-silicon-copper alloy according to claim 3, characterized in that: In step S3, the target temperature during the cooling process is 700°C, and the cooling rate is 15-20°C / min.

5. The method for preparing a high-strength and toughness modified hypereutectic aluminum-silicon-copper alloy according to claim 3, characterized in that: In step S3, the mold is an iron mold or a copper mold.

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