High-strength and high-heat-resistance cast aluminum alloy and preparation method thereof

Abstract

The invention discloses a high-strength and high-heat-resistance cast aluminum alloy and a preparation method thereof, and belongs to the technical field of aluminum alloys. The high-strength and high-heat-resistance cast aluminum alloy comprises, by weight, 11.0 wt%-13.0 wt% of Si, 0.1 wt%-0.3 wt% of Fe, 3.5 wt%-4.5 wt% of Cu, 0.5 wt%-1.5 wt% of Mn, 0.8 wt%-1.2 wt% of Mg, 2.0 wt%-3.0 wt% of Ni, 0.2 wt%-0.4 wt% of Zn, 0.05 wt%-0.3 wt% of Zr, 0.2 wt%-0.4 wt% of Ti and the balance Al and inevitable impurity elements, by designing the components of the Al-Si-Cu-Mg-Ni alloy, the obtained high-strength and high-heat-resistance cast aluminum alloy has the excellent high-temperature mechanical property, and the tensile strength at the temperature of 350 DEG C reaches up to 120 MPa.

Description

Technical Field

[0001] The present invention belongs to the technical field of aluminum alloys, and in particular relates to a high-strength and high-heat-resistant cast aluminum alloy and a preparation method thereof. Background Art

[0002] Aluminum-silicon alloys have the characteristics of low density, high strength, and good fluidity. They are considered to be key materials for achieving lightweight structures and have broad application prospects in industrial fields such as aerospace, automobiles, and ships. Among them, Al-Si-Cu-Mg-Ni alloys are known for their high service temperatures, which can reach 300-350°C. Currently, grades such as ZL109 and M142 have been used to manufacture hot-end components such as automobile engine pistons and cylinder heads. With the continuous improvement of engine power density and fuel economy requirements, the upper temperature limit of hot-end components urgently needs to be increased to 350°C and above. This also places higher demands on the service performance of Al-Si-Cu-Mg-Ni alloys, especially the high-temperature strength at 350°C.

[0003] Microalloying can improve alloy strength by changing the type, morphology, and distribution of the secondary phase in Al-Si-Cu-Mg-Ni alloys. It is a commonly used alloy strengthening method both domestically and internationally. Chinese patent CN101117679A discloses a high-performance aluminum-silicon piston alloy material with the following composition: Si 12-13%, Cu 2.5-4%, Ni 1.7-3%, Mg 0.5-1.2%, Mn 0.1-0.2%, V 0.15-0.5%, Ti 0.23-0.6%, Re 0.15-0.25%, Zn ≤ 0.05%, Fe ≤ 0.7%, with the remainder being Al. This alloy exhibits a room temperature tensile strength of no less than 230 MPa, a tensile strength of no less than 100 MPa at 300°C, and a tensile strength of no less than 80 MPa at 360°C. Chinese patent CN113897520A discloses a high-strength, heat-resistant cast aluminum-silicon alloy for engine pistons. The alloy comprises, by weight, 12.0-15.0% Si, 2.0-4.5% Cu, 0.5-1.5% Mg, 0.2-0.5% Mn, 2.2-4.5% Ni, and 0.1-0.6% Zr. The balance is Al, incidental elements, and unavoidable impurities. The microalloying elements are one or more of Er, Hf, Nb, Nd, Sc, and Ti, with the total amount of these microalloying elements satisfying a ratio of 0.1% ≤ (Er+Hf+Nb+Nd+Sc+Ti) wt% ≤ 0.9%. This alloy exhibits superior high-temperature performance to the currently used ZL109 alloy, achieving a high-temperature strength of 98 MPa at 350°C.

[0004] Although the addition of various microalloying elements has significantly improved the high-temperature strength of Al-Si-Cu-Mg-Ni alloys, their high-temperature performance at 350°C is still relatively low. Therefore, there is an urgent need to develop a cast heat-resistant aluminum alloy with a tensile strength exceeding 110 MPa above 350°C to meet the higher requirements of the automotive field for high-performance hot-end component materials. Summary of the Invention

[0005] In order to solve the above technical problems, the present invention proposes a high-strength and high-heat-resistant cast aluminum alloy and a preparation method thereof.

[0006] To achieve the above objectives, the present invention provides the following technical solutions:

[0007] The invention provides a high-strength and high-heat-resistant cast aluminum alloy, comprising the following components in weight percentage: Si 11.0-13.0wt%, Fe 0.1-0.3wt%, Cu 3.5-4.5wt%, Mn 0.5-1.5wt%, Mg 0.8-1.2wt%, Ni 2.0-3.0wt%, Zn 0.2-0.4wt%, Zr 0.05-0.3wt%, Ti 0.2-0.4wt%, and the balance being Al and unavoidable impurity elements.

[0008] Furthermore, the high-strength and high-heat-resistant cast aluminum alloy includes the following components in weight percentage: Si11.0~12.5wt%, Fe 0.1~0.2wt%, Cu 3.5~4.0wt%, Mn 0.5~1.5wt%, Mg0.8~1.0wt%, Ni2.5~3.0wt%, Zn 0.3~0.4wt%, Zr 0.05~0.2wt%, Ti 0.2~0.3wt%, and the balance is Al and unavoidable impurity elements.

[0009] Furthermore, the high-strength and high-heat-resistant cast aluminum alloy has a tensile strength of 115 to 120 MPa at 350° C. and an elongation of 2.7 to 3.4%.

[0010] The present invention also provides a method for preparing the high-strength and high-heat-resistant cast aluminum alloy described in the above technical solution, comprising the following steps: melting the aluminum alloy raw material to obtain an aluminum alloy melt, and casting to obtain an aluminum alloy ingot; performing a two-stage solid solution treatment and a two-stage aging treatment on the aluminum alloy ingot to obtain the high-strength and high-heat-resistant cast aluminum alloy.

[0011] Furthermore, the aluminum alloy raw materials include aluminum ingots, magnesium ingots, industrial silicon, copper wire, zinc ingots, aluminum-manganese master alloys, aluminum-nickel master alloys, aluminum-zirconium master alloys and aluminum-titanium master alloys.

[0012] Furthermore, the preparation process of the aluminum alloy melt includes the following steps:

[0013] A. Aluminum ingots, industrial silicon, zinc ingots, aluminum-manganese master alloys, aluminum-nickel master alloys, aluminum-titanium master alloys, and aluminum-zirconium master alloys are first melted, and then skimmed, stirred, and re-skimmed to obtain a melt;

[0014] B. adding copper wire and magnesium ingot to the melt 1, performing slagging, stirring and re-slagging after the second melting to obtain melt 2;

[0015] C. adding a refining agent to the melt 2 for refining, allowing it to stand, skimming, stirring, and skimming again to obtain a melt 3;

[0016] D. Degassing and refining the melt 3, and obtaining the aluminum alloy melt after standing and slagging.

[0017] Furthermore, in step A, the first melting temperature is 770-780° C.; and / or,

[0018] In step B, the second melting temperature is 750-760°C.

[0019] Furthermore, in step C, the mass of the refining agent is 0.2% of the mass of the melt 2; the refining temperature is below 750° C., and the refining time is 10 to 15 minutes.

[0020] Furthermore, in step D, the degassing and refining gas is argon, and the degassing and refining time is 10 to 15 minutes; and / or,

[0021] The standing time is ≥10 min.

[0022] Furthermore, the two-stage solution treatment includes a primary solution treatment and a secondary solution treatment; the temperature of the primary solution treatment is 475-490° C., and the holding time is 2-5 hours; the temperature of the secondary solution treatment is 490-510° C., and the holding time is 2-5 hours; and / or,

[0023] The two-stage aging treatment includes a primary aging treatment and a secondary aging treatment; the temperature of the primary aging treatment is 200-230° C., and the holding time is 4-6 hours; the temperature of the secondary aging treatment is 230-255° C., and the holding time is 2-4 hours.

[0024] Compared with the prior art, the present invention has the following advantages and technical effects:

[0025] (1) By designing the composition of the Al-Si-Cu-Mg-Ni alloy, the present invention obtains a high-strength and high-heat-resistant cast aluminum alloy with excellent high-temperature mechanical properties. The tensile strength at 350°C is as high as 120 MPa, which is 20% higher than that of existing similar aluminum alloy materials.

[0026] (2) The preparation process of the high-strength and high-heat-resistant cast aluminum alloy provided by the present invention is compatible with existing production equipment and can be used for large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The accompanying drawings, which constitute part of the present invention, are provided to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are provided to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0028] Figure 1 The microstructure of the aluminum alloy ingot obtained in step (6) of Example 1;

[0029] Figure 2 The microstructure of the aluminum alloy ingot obtained in step (6) of Example 2;

[0030] Figure 3 This is a high-temperature tensile curve diagram of the high-strength and high-heat-resistant cast aluminum alloy prepared in Example 1 and Example 2. DETAILED DESCRIPTION

[0031] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0032] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0033] An embodiment of the present invention provides a high-strength and high-heat-resistant cast aluminum alloy, comprising the following components in weight percentage: Si 11.0-13.0wt%, Fe 0.1-0.3wt%, Cu 3.5-4.5wt%, Mn 0.5-1.5wt%, Mg 0.8-1.2wt%, Ni 2.0-3.0wt%, Zn 0.2-0.4wt%, Zr 0.05-0.3wt%, Ti 0.2-0.4wt%, and the balance being Al and unavoidable impurity elements;

[0034] In a further preferred embodiment, the composition of the high-strength and high-heat-resistant cast aluminum alloy is as follows: Si11.0~12.5wt%, Fe 0.1~0.2wt%, Cu 3.5~4.0wt%, Mn 0.5~1.5wt%, Mg0.8~1.0wt%, Ni 2.5~3.0wt%, Zn 0.3~0.4wt%, Zr 0.05~0.2wt%, Ti 0.2~0.3wt%, and the balance is Al and unavoidable impurity elements.

[0035] In a preferred embodiment, the total mass fraction of the impurity elements is ≤0.15%, and the mass fraction of a single impurity element is ≤0.05%.

[0036] In an optional embodiment, the composition of the high-strength and high-heat-resistant cast aluminum alloy is as follows: Si 12.5wt%, Fe0.2wt%, Cu 4.0wt%, Mn 1.5wt%, Mg 0.8wt%, Ni 2.5wt%, Zn 0.3wt%, Zr0.2wt%, Ti 0.2wt%, and the remainder is Al and unavoidable impurity elements; wherein the mass fraction of a single impurity element is ≤0.05%, and the total mass fraction of the impurity elements is ≤0.15%.

[0037] In another optional embodiment, the composition of the high-strength and high-heat-resistant cast aluminum alloy is as follows: Si 11.0wt%, Fe0.1wt%, Cu 3.5wt%, Mn 0.5wt%, Mg 1.0wt%, Ni 3.5wt%, Zr 0.2wt%, Ti0.3wt%, and the remainder is Al and unavoidable impurity elements; wherein the mass fraction of a single impurity element is ≤0.05%, and the total mass fraction of the impurity elements is ≤0.15%.

[0038] The reasons for setting the content of each alloying element in the high-strength and high-heat-resistant cast aluminum alloy provided by the present invention and the mechanism of action are as follows: The present invention adjusts the component ratio of conventional silicon aluminum alloy and simultaneously adds appropriate proportions of zinc, manganese, zirconium, titanium and other elements to synergistically improve the metallographic structure of the alloy, thereby improving the tensile strength and elongation. Specifically: zinc dissolves in the aluminum matrix to produce solid solution strengthening and forms a strengthening phase MgZn2 with magnesium, significantly improving the tensile strength; manganese and iron form a massive (Fe, Mn)Al6 phase, replacing the needle-shaped FeAl3 phase, reducing stress concentration points and improving toughness; the MnAl6 dispersed phase hinders grain boundary migration, refines recrystallized grains, and reduces the tendency to hot cracking; manganese dissolves in the aluminum matrix to slightly improve strength, zirconium forms Al3Zr nanoparticles, and titanium forms TiAl3, which serve as heterogeneous nucleation cores and significantly refine the solidification structure. The Al3Zr phase pins grain boundaries and dislocations, inhibits recrystallization, and the grain refinement strengthening effect enhances room temperature strength. Cu forms Al2Cu phase and Q phase (Al5Cu2Mg8Si6), both of which are strengthening phases and are one of the main strengthening elements of the alloy. Secondly, Ni and other elements form AlNi3 phase, Al3CuNi phase, and Al7Cu4Ni phase, all of which are high-temperature strengthening phases. Under ultra-high temperature conditions, the high-melting-point Ni-rich phase has the effect of pinning dislocations, thereby improving high-temperature performance.

[0039] In a preferred embodiment, the high-strength and high-heat-resistant cast aluminum alloy has a tensile strength of 115 to 120 MPa at 350° C. and an elongation of 2.7 to 3.4%.

[0040] The present invention also provides a method for preparing a high-strength and high-heat-resistant cast aluminum alloy, comprising the following steps: melting an aluminum alloy raw material to obtain an aluminum alloy melt, and casting to obtain an aluminum alloy ingot; and subjecting the aluminum alloy ingot to a two-stage solid solution treatment and a two-stage aging treatment to obtain the high-strength and high-heat-resistant cast aluminum alloy.

[0041] In a preferred embodiment, the aluminum alloy raw materials include aluminum ingots, magnesium ingots, industrial silicon, copper wire, zinc ingots, aluminum-manganese master alloys, aluminum-nickel master alloys, aluminum-zirconium master alloys and aluminum-titanium master alloys; as a typical but non-limiting example, the aluminum-manganese master alloy is selected from AlMn10; the aluminum-nickel master alloy is selected from AlNi20; the aluminum-zirconium master alloy is selected from AlZr10; and the aluminum-titanium master alloy is selected from AlTi10.

[0042] In a preferred embodiment, the preparation process of the aluminum alloy melt includes the following steps:

[0043] A. Aluminum ingots, industrial silicon, zinc ingots, aluminum-manganese master alloys, aluminum-nickel master alloys, aluminum-titanium master alloys, and aluminum-zirconium master alloys are first melted, and then skimmed, stirred, and re-skimmed to obtain a melt;

[0044] B. adding copper wire and magnesium ingot to the melt 1, performing slagging, stirring and re-slagging after the second melting to obtain melt 2;

[0045] C. adding a refining agent to the melt 2 for refining, allowing it to stand, skimming, stirring, and skimming again to obtain a melt 3;

[0046] D. Degassing and refining the melt 3, and obtaining the aluminum alloy melt after standing and slagging.

[0047] In a preferred embodiment, in step A, the first melting temperature is 770-780°C.

[0048] In a preferred embodiment, in step B, the second melting temperature is 750-760°C.

[0049] In a preferred embodiment, in step C, the mass of the refining agent is 0.2% of the mass of the melt 2; the refining temperature is below 750°C, more preferably 740-750°C; and the refining time is 10-15 minutes.

[0050] In a preferred embodiment, in step D, the degassing and refining gas is argon, and the degassing and refining time is 10 to 15 minutes.

[0051] In a preferred embodiment, in step D, the standing time is ≥10 min, more preferably 10 to 20 min.

[0052] In a preferred embodiment, the casting process is specifically as follows: casting the aluminum alloy melt into a preheated cast iron mold to obtain an aluminum alloy ingot; the preheating temperature is 120-140°C.

[0053] In a preferred embodiment, the two-stage solution treatment includes a primary solution treatment and a secondary solution treatment; the temperature of the primary solution treatment is 475-490°C, and the holding time is 2-5h; the temperature of the secondary solution treatment is 490-510°C, and the holding time is 2-5h. The heating rate during the two-stage solution treatment is 10°C / min. The present invention uses a two-stage solution treatment to first dissolve the low-melting-point Cu-rich phase into the aluminum matrix at a relatively low temperature, and then raises the temperature to dissolve other elements in the alloy into the aluminum matrix to reach a supersaturated solid solution state, and then combines it with a two-stage aging process to allow the alloy elements to precipitate quickly and form a fine and dispersed strengthening phase with other elements.

[0054] In a preferred embodiment, the two-stage aging treatment includes a primary aging treatment and a secondary aging treatment; the temperature of the primary aging treatment is 200-230°C, and the holding time is 4-6 hours; the temperature of the secondary aging treatment is 230-255°C, and the holding time is 2-4 hours. The heating rate during the two-stage aging treatment is 10°C / min. The present invention uses a two-stage aging treatment to first uniformly precipitate the Cu element in the supersaturated solid solution in the form of GP zones at a lower aging temperature, and then accelerates the precipitation of Cu and Ni elements to form a dispersed high-temperature strengthening phase by increasing the aging temperature. The dispersed high-temperature strengthening phase can effectively hinder dislocation movement, thereby improving the strength of the material at high temperatures. At the same time, the fine and evenly distributed strengthening phase can make the material deform uniformly, thereby improving the elongation of the material at high temperatures.

[0055] The room temperature in the embodiments of the present invention refers to "25±2°C".

[0056] Unless otherwise specified, the raw materials in the examples of the present invention were purchased from commercial sources.

[0057] Example 1

[0058] A high-strength and high-heat-resistant cast aluminum alloy is composed of the following components in weight percentage: Si 12.5wt%, Fe 0.2wt%, Cu 4.0wt%, Mn 1.5wt%, Mg 0.8wt%, Ni 2.5wt%, Zn 0.3wt%, Zr 0.2wt%, Ti 0.2wt%, with the remainder being Al and unavoidable impurity elements; wherein the mass fraction of a single impurity element is ≤0.05%, and the total mass fraction of the impurity elements is ≤0.15%.

[0059] The preparation method of the above-mentioned high-strength and high-heat-resistant cast aluminum alloy comprises the following steps:

[0060] (1) Based on the weight percentages of the above alloying elements and taking into account the burnout during the alloy smelting process and the alloy composition and content in the scrap, calculate the weights of the required high-purity aluminum ingot (99.99%), magnesium ingot, industrial pure silicon, copper wire, zinc ingot, aluminum-manganese master alloy AlMn10, aluminum-nickel master alloy AlNi20, aluminum-zirconium master alloy AlZr10, and aluminum-titanium master alloy AlTi10. Based on the calculated results, weigh the various alloy raw materials;

[0061] (2) adding high-purity aluminum ingots, industrial pure silicon, zinc ingots, aluminum-manganese master alloy AlMn10, aluminum-nickel master alloy AlNi20, aluminum-titanium master alloy AlZr10, and aluminum-zirconium master alloy AlTi10 into a melting furnace preheated to 780° C., and skimming the slag after all the raw materials are melted to obtain melt 1;

[0062] (3) When the temperature of melt 1 drops to 760°C, use a graphite rod to press the copper wire and magnesium ingot into melt 1 to prevent them from floating to the liquid surface and coming into contact with air. After the copper wire and magnesium ingot are completely melted, they are skimmed, stirred, and skimmed again to obtain melt 2.

[0063] (4) When the temperature of melt 2 drops to 750°C, a refining agent (0.2% of the total mass of melt 2) wrapped in aluminum foil is pressed into melt 2 using a graphite rod to prevent the refining agent from floating to the liquid surface and contacting the air. After refining for 10 minutes, the refining agent is skimmed, stirred, and skimmed again to obtain melt 3.

[0064] (5) The temperature of the melt 3 is maintained at 750° C., and the melt 3 is refined with argon for 15 minutes. After standing and keeping the temperature for 20 minutes, the melt 3 is skimmed to obtain an aluminum alloy melt;

[0065] (6) casting the aluminum alloy melt into a preheated cast iron mold at a preheating temperature of 130° C. to obtain an aluminum alloy ingot;

[0066] (7) The aluminum alloy ingot is placed in a box furnace and heated to 475°C and kept warm for 4 hours, then heated to 510°C and kept warm for 4 hours at a heating rate of 10°C / min, then quenched with 80°C hot water and cooled to room temperature; the aluminum alloy ingot after double-stage solid solution treatment is heated to 200°C and kept warm for 4 hours, then heated to 255°C and kept warm for 2 hours at a heating rate of 10°C / min, and then air-cooled to room temperature to obtain a high-strength and high-heat-resistant cast aluminum alloy.

[0067] Example 2

[0068] A high-strength and high-heat-resistant cast aluminum alloy, comprising the following components in weight percentage: Si 11.0wt%, Fe 0.1wt%, Cu 3.5wt%, Mn 0.5wt%, Mg 1.0wt%, Ni 3.0wt%, Zr 0.2wt%, Ti 0.3wt%, with the remainder being Al and unavoidable impurity elements; wherein the mass fraction of a single impurity element is ≤0.05%, and the total mass fraction of the impurity elements is ≤0.15%;

[0069] The preparation method of the high-strength and high-heat-resistant cast aluminum alloy is the same as that in Example 1.

[0070] The aluminum alloy ingots obtained in step (6) of Example 1 and Example 2 were subjected to microstructural observation, and the results are shown in FIG. Figure 1 and Figure 2 .

[0071] Figure 1 This is the microstructure diagram of the aluminum alloy ingot obtained in step (6) of Example 1. Figure 2 The microstructure of the aluminum alloy ingot obtained in step (6) of Example 2 is shown in FIG. Figure 1 and Figure 2 It can be seen that the second phase in the aluminum alloy ingots obtained in Example 1 and Example 2 is mainly eutectic Si, Al3CuNi, Al3Ni, Al7Cu4Ni and Al5Cu2Mg8Si6 phases. Figure 1 and Figure 2 The total volume fraction of the intermetallic compound phase calculated by software is between 10% and 14%.

[0072] The high strength and high heat resistant cast aluminum alloy prepared in Example 1 and Example 2 was subjected to high temperature tensile test (GB / T228.2-2015 Metallic Materials Tensile Test Part 2: High Temperature Test Method) and the results are shown in Figure 3 .

[0073] Figure 3 The high temperature tensile curves of the high strength and high heat resistant cast aluminum alloy prepared in Example 1 and Example 2 are shown. Figure 3 It can be seen that the high-strength and high-heat-resistant cast aluminum alloy prepared in Example 1 has a tensile strength of 120 MPa at 350°C and an elongation of 3.4%; the high-strength and high-heat-resistant cast aluminum alloy prepared in Example 2 has a tensile strength of 115 MPa at 350°C and an elongation of 2.7%.

[0074] Comparative Example 1

[0075] A cast aluminum alloy consists of the following components in weight percentage: Si 12.5wt%, Fe 0.2wt%, Cu 4.0wt%, Mn 2.0wt%, Mg 0.8wt%, Ni 2.5wt%, Zn 0.3wt%, Zr 0.2wt%, Ti 0.2wt%, with the balance being Al and unavoidable impurity elements; wherein the mass fraction of a single impurity element is ≤0.05%, and the total mass fraction of the impurity elements is ≤0.15%.

[0076] The preparation method is the same as that of Example 1.

[0077] Comparative Example 2

[0078] A cast aluminum alloy consists of the following components in weight percentage: Si 12.5wt%, Fe 0.2wt%, Cu 4.0wt%, Mn 1.5wt%, Mg 0.8wt%, Ni 1.5wt%, Zn 0.3wt%, Zr 0.2wt%, Ti 0.2wt%, with the remainder being Al and unavoidable impurity elements; wherein the mass fraction of a single impurity element is ≤0.05%, and the total mass fraction of the impurity elements is ≤0.15%.

[0079] The preparation method is the same as that of Example 1.

[0080] Comparative Example 3

[0081] A cast aluminum alloy consists of the following components in weight percentage: Si 12.5wt%, Fe 0.2wt%, Cu 4.0wt%, Mn 1.5wt%, Mg 0.8wt%, Ni 3.5wt%, Zn 0.3wt%, Zr 0.2wt%, Ti 0.2wt%, with the balance being Al and unavoidable impurity elements; wherein the mass fraction of a single impurity element is ≤0.05%, and the total mass fraction of the impurity elements is ≤0.15%.

[0082] The preparation method is the same as that of Example 1.

[0083] Comparative Example 4

[0084] A cast aluminum alloy consists of the following components in weight percentage: Si 12.5wt%, Fe 0.2wt%, Cu 4.0wt%, Mn 1.5wt%, Mg 0.8wt%, Ni 2.5wt%, Zn 0.3wt%, Ti 0.2wt%, with the balance being Al and unavoidable impurity elements; wherein the mass fraction of a single impurity element is ≤0.05%, and the total mass fraction of the impurity elements is ≤0.15%.

[0085] The preparation method steps are as follows:

[0086] (1) Based on the weight percentages of the above alloying elements and taking into account the burnout during the alloy smelting process and the alloy composition and content in the scrap, calculate the weights of the required high-purity aluminum ingot (99.99%), magnesium ingot, industrial pure silicon, copper wire, zinc ingot, aluminum-manganese master alloy AlMn10, aluminum-nickel master alloy AlNi20, and aluminum-titanium master alloy AlTi10. Based on the calculated results, weigh the various alloy raw materials;

[0087] (2) adding high-purity aluminum ingots, industrial pure silicon, zinc ingots, aluminum-manganese master alloy AlMn10, aluminum-nickel master alloy AlNi20, and aluminum-titanium master alloy AlZr10 into a melting furnace preheated to 780° C., and skimming off the slag after all the raw materials are melted to obtain melt 1;

[0088] (3) to (7) are the same as in Example 1.

[0089] Comparative Example 5

[0090] The composition of the cast aluminum alloy is different from that of Example 1. The difference is that step (7) is: heating the aluminum alloy ingot to 255°C in a furnace at a heating rate of 10°C / min, keeping it warm for 6 hours, and then air-cooling it to room temperature to obtain a cast aluminum alloy.

[0091] The high temperature tensile properties of the cast aluminum alloys in Comparative Examples 1 to 5 were tested using the same method as in Example 1. The results are shown in Table 1.

[0092] Table 1

[0093]

[0094] As can be seen from Table 1, in Comparative Example 1, the Mn element is added. The Mn element can improve the morphology of the Fe-containing phase, and excessive Mn elements will increase the brittleness of the alloy. In Comparative Examples 2-3, reducing or increasing the Ni element has a significant impact on the high-temperature performance of the alloy. If Ni is too low, the high-temperature performance is insufficient, and if it exceeds 3.0%, the Ni-rich phase will be coarse, resulting in a decrease in the elongation of the alloy. In Comparative Example 4, the absence of the Zr element will result in coarse grains of the material, because the Zr element has a more obvious grain refining effect, resulting in insufficient high-temperature performance of the alloy. Comparative Example 5 adopts a single-stage heat treatment, and the strength of the alloy decreases. This is because the single-stage treatment cannot dissolve and precipitate the elements step by step, making it difficult to achieve the fine dispersion distribution effect of the strengthening phase achieved by the double-stage heat treatment.

[0095] In summary, the Al-Si-Cu-Mg-Ni alloy designed in the present invention is a new type of heat-resistant cast aluminum alloy with high strength and excellent heat resistance. Its tensile strength at 350°C exceeds 115 MPa and can reach up to 120 MPa, which is more than 15% higher than that of existing similar aluminum alloy materials. In addition, the aluminum alloy designed in the present invention has a simple preparation process, is compatible with existing production equipment, and can be mass-produced.

[0096] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A high-strength and high-heat-resistant cast aluminum alloy, characterized in that: The invention comprises the following components in weight percentage: Si 11.0-13.0wt%, Fe 0.1-0.3wt%, Cu 3.5-4.5wt%, Mn 0.5-1.5wt%, Mg 0.8-1.2wt%, Ni 2.0-3.0wt%, Zn 0.2-0.4wt%, Zr 0.05-0.3wt%, Ti 0.2-0.4wt%, and the balance is Al and unavoidable impurity elements.

2. The high-strength and high-heat-resistant cast aluminum alloy according to claim 1, characterized in that: The high-strength and high-heat-resistant cast aluminum alloy includes the following components in weight percentage: Si 11.0-12.5wt%, Fe 0.1-0.2wt%, Cu 3.5-4.0wt%, Mn 0.5-1.5wt%, Mg 0.8-1.0wt%, Ni 2.5-3.0wt%, Zn 0.3-0.4wt%, Zr 0.05-0.2wt%, Ti 0.2-0.3wt%, and the balance is Al and unavoidable impurity elements.

3. The high-strength and high-heat-resistant cast aluminum alloy according to claim 2, characterized in that: The high-strength and high-heat-resistant cast aluminum alloy has a tensile strength at 350° C. of 115 to 120 MPa and an elongation of 2.7 to 3.4%.

4. A method for preparing the high-strength and high-heat-resistant cast aluminum alloy according to any one of claims 1 to 3, characterized in that: The following steps are involved: The aluminum alloy raw material is melted to obtain an aluminum alloy melt, and then cast to obtain an aluminum alloy ingot; The aluminum alloy ingot is subjected to a double-stage solid solution treatment and a double-stage aging treatment to obtain the high-strength and high-heat-resistant cast aluminum alloy.

5. The method for preparing a high-strength and high-heat-resistant cast aluminum alloy according to claim 4, characterized in that: The aluminum alloy raw materials include aluminum ingots, magnesium ingots, industrial silicon, copper wire, zinc ingots, aluminum-manganese master alloys, aluminum-nickel master alloys, aluminum-zirconium master alloys and aluminum-titanium master alloys.

6. The method for preparing a high-strength and high-heat-resistant cast aluminum alloy according to claim 5, characterized in that: The preparation process of the aluminum alloy melt comprises the following steps: A. Aluminum ingots, industrial silicon, zinc ingots, aluminum-manganese master alloys, aluminum-nickel master alloys, aluminum-titanium master alloys, and aluminum-zirconium master alloys are first melted, and then skimmed, stirred, and re-skimmed to obtain a melt; B. adding copper wire and magnesium ingot to the melt 1, performing slagging, stirring and re-slagging after the second melting to obtain melt 2; C. adding a refining agent to the melt 2 for refining, allowing it to stand, skimming, stirring, and skimming again to obtain a melt 3; D. Degassing and refining the melt 3, and obtaining the aluminum alloy melt after standing and slagging.

7. The method for preparing a high-strength and high-heat-resistant cast aluminum alloy according to claim 6, characterized in that: In step A, the first melting temperature is 770-780° C.; and / or, In step B, the second melting temperature is 750-760°C.

8. The method for preparing a high-strength and high-heat-resistant cast aluminum alloy according to claim 6, wherein: In step C, the mass of the refining agent is 0.2% of the mass of the melt 2; the refining temperature is below 750° C., and the refining time is 10 to 15 minutes.

9. The method for preparing a high-strength and high-heat-resistant cast aluminum alloy according to claim 6, wherein: In step D, the degassing and refining gas is argon, and the degassing and refining time is 10 to 15 minutes; and / or, The standing time is ≥10 min.

10. The method for preparing a high-strength and high-heat-resistant cast aluminum alloy according to claim 4, characterized in that: The two-stage solution treatment includes a primary solution treatment and a secondary solution treatment; the primary solution treatment is performed at a temperature of 475-490° C. and a holding time of 2-5 hours; the secondary solution treatment is performed at a temperature of 490-510° C. and a holding time of 2-5 hours; and / or The two-stage aging treatment includes a primary aging treatment and a secondary aging treatment; the temperature of the primary aging treatment is 200-230° C., and the holding time is 4-6 hours; the temperature of the secondary aging treatment is 230-255° C., and the holding time is 2-4 hours.

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