High-strength and high-toughness cast aluminum alloy and preparation method and application thereof

Abstract

The invention discloses a high-strength and high-toughness cast aluminum alloy as well as a preparation method and application thereof, and the cast aluminum alloy comprises the following components in percentage by mass: 4%-11% of Si, 0.2%-0.8% of Mg, 0.3%-1.8% of Cu, 0.10%-0.14% of Ti, 0-1.0% of Zn, 0.10%-0.30% of Fe, 0.015%-0.030% of Sr and the balance of Al and inevitable impurities. Zn + Cu is less than or equal to 2%, and Cu / Mg is greater than or equal to 2; the preparation method comprises the following steps: carrying out heat treatment on an aluminum alloy ingot; the heat treatment comprises three stages of solid solutions, and the temperatures of the three stages are respectively 490-500 DEG C, 530-540 DEG C and 545-555 DEG C. The aluminum alloy is high in tensile strength and yield strength and high in ductility, the solid solution time is remarkably shortened during preparation, and the production cost is remarkably reduced.

Description

Technical Field

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

[0002] Hypoeutectic aluminum-silicon alloy Al-Si is widely used in new energy vehicles due to its good casting performance, medium strength, and excellent corrosion resistance. At present, the cast aluminum alloy materials used for automobile chassis or related structural parts are mainly A356 series cast aluminum alloys. The main components of the alloy include silicon (Si) between 6.5% and 7.5%, magnesium (Mg) content between 0.20% and 0.40%, and iron (Fe), copper (Cu), manganese (Mn), zinc (Zn) and titanium (Ti) are strictly controlled within a lower threshold. After T6 heat treatment, the yield strength of A356 cast aluminum alloy is ≥220MPa and the tensile strength is ≥300MPa. It is mainly used for a series of important parts such as automobile wheel hubs, front and rear subframes of chassis, steering knuckles, control arms, etc. However, the strength and toughness of A356 material are not high, which restricts the weight reduction effect and production of the above parts. A356 cast aluminum alloy can no longer meet the comprehensive performance requirements of new energy vehicles in the new era for complex geometric dimensions, cost and other parts.

[0003] Patent CN114250389A discloses a high-strength and toughness cast aluminum alloy and its heat treatment process. The percentage content of each component of the cast aluminum alloy is: Si: 5~8.5wt%, Cu: 1~3wt%, Mg: 0.3~0.5wt%, Zn: 0.5~1.0wt%, Fe: 0.1~0.2wt%, Ti: 0.1~0.3wt%, Cr: 0.1~0.3wt% Zr: 0.1~0.3wt%, Sr: 0.02~0.06wt%, mixed rare earth Re: 0.20~0.4wt%, the sum of other unavoidable impurity elements not more than 0.15wt%, and the balance aluminum. In the heat treatment process, the solid solution parameters are: 480℃±1℃ for 4h±0.2h, 500℃±1℃ for 6h, 525℃±1℃ for 6h, quenching water temperature 70~90℃; aging parameters: 175±1℃ for 7±0.2h. However, the solid solution efficiency of the aluminum alloy is low, the overall solid solution time is too long, exceeding 16h, which is not conducive to production, and the change of Fe phase is not considered, which is not conducive to the improvement of alloy strength and elongation.

[0004] Patent CN102676961B discloses a copper-rich cast hypoeutectic aluminum-silicon alloy with a composition of Al-7%Si-0.35%Mg-1.5%~3.5%Cu. The process adopts a three-stage solid solution, which is 485℃±5℃ insulation for 7~8h, 515℃±5℃ insulation for 4~6h, 535℃±5℃ insulation for 2~4h, and aging at 170℃±5℃ insulation for 7~10h; however, the solid solution time of this process is too long (total length exceeds 13h), the energy consumption is large, and only the change of Cu phase is considered, and the Mg atoms in the π-Fe phase are not considered. Its performance can be further improved.

[0005] Patent CN106282685B discloses a high-strength cast aluminum alloy, which is composed of Si 6.0-8.0%, Cu0.5-2.0%, Mg 0.2-0.6%, Ti 0.05-0.30%, Gd 0.05-0.5%, Sr 0.01-0.05%, Fe≤0.20%, impurity elements≤0.50%, and the balance is aluminum. The solid solution scheme adopted in the heat treatment process is: keep warm for 6-8 hours at 500-520℃, then continue to heat to 525-550℃ and keep warm for 8-10 hours; age at 150-180℃, keep warm for 7-9 hours, and finally take out of the furnace and air cool to room temperature. However, the solid solution time of this process is also as long as 14 to 18 hours, and the Mg content in the π-Fe phase is not maximized and the β-Fe phase is not melted, and the strength of the aluminum alloy needs to be further improved. Summary of the invention

[0006] The object of the present invention is to overcome one or more deficiencies in the prior art and to provide a high-strength and high-toughness cast aluminum alloy having high tensile strength and yield strength and high elongation, and the solution time during preparation is significantly shortened and the production cost is significantly reduced.

[0007] The present invention also provides a method for preparing the cast aluminum alloy.

[0008] The invention also provides a use of the cast aluminum alloy.

[0009] In order to achieve the above object, the present invention adopts the following technical solutions:

[0010] A method for preparing a cast aluminum alloy, wherein the cast aluminum alloy comprises, by mass percentage, 4% to 11% Si, 0.2% to 0.8% Mg, 0.3% to 1.8% Cu, 0.10% to 0.14% Ti, 0% to 1.0% Zn, 0.10% to 0.30% Fe, 0.015% to 0.030% Sr, and the balance is Al and unavoidable impurities; the total mass percentage of Zn and Cu is less than or equal to 2.0%; the mass ratio of Cu to Mg is greater than or equal to 2;

[0011] The preparation method comprises the steps of preparing aluminum alloy ingots from various raw material components; and the step of heat treating the aluminum alloy ingots; the heat treatment comprises the following steps performed in sequence:

[0012] Primary solution treatment: keep warm at 490-500℃;

[0013] Secondary solution treatment: keep warm at 530-540℃;

[0014] Level 3 solution treatment: keep warm at 545-555℃.

[0015] In the prior art, the designed alloy composition leads to an increase in the second phase. For example, the Cu content increases too much, or micro-alloying elements such as Mn, Cr, and Zr are added to form a large number of second phases that are difficult to dissolve back, which not only reduces the elongation of the alloy, but also increases the density of the alloy. In addition, the existing aluminum alloy composition design leads to a long solid solution time, often exceeding 14 hours, which not only causes a large amount of energy consumption, but also promotes the growth of the Si phase and reduces the elongation of the alloy. In addition, the solid solution process of the existing aluminum alloy usually only considers the change of the Cu phase, and does not consider the dissolution of the Mg element in the π-Fe phase, resulting in less Mg element in the process of forming the nanophase. The increase in Cu content will also reduce the melting point of the Cu-containing phase, resulting in the inability to increase the solid solution temperature and the inability of the needle-shaped β-AlSiFe phase to melt. The inventor of the present application has found through research that by designing a reasonable aluminum alloy composition, especially by controlling the content of Zn and Cu, and the mass ratio of Cu and Mg, and adjusting the solid solution scheme and solid solution temperature, adopting a three-stage solid solution treatment, and controlling the temperature of each solid solution treatment, the second phase generation that is difficult to dissolve back can be reduced, the alloy elongation can be ensured, the Cu-containing phase can be fully dissolved, and the total solid solution time can be significantly shortened, energy consumption can be reduced, and Si phase coarsening can be avoided at the same time. The aluminum alloy composition of the present invention can be graded for solid solution, and the solid solution temperature can be increased to 550°C, which can maximize the dissolution of the Mg element in the π-Fe phase, promote the further increase of the alloy strength, help to fuse the smaller β-AlSiFe phase, and improve the alloy elongation.

[0016] In some embodiments, in the cast aluminum alloy, the total mass percentage of Zn and Cu is 0.3-2.0%.

[0017] In some embodiments, in the cast aluminum alloy, the mass ratio of Cu to Mg is 2-9.

[0018] In some embodiments, the cast aluminum alloy includes Zn, and the mass percentage of Zn is 0.1% to 1.0%. Adding Zn element can not only improve the strength of aluminum alloy products, but also shorten the time of aging treatment.

[0019] In some embodiments, in the cast aluminum alloy, Mg accounts for 0.25% to 0.5% by mass.

[0020] In some embodiments, in the cast aluminum alloy, Cu accounts for 0.7% to 1.4% by mass.

[0021] In some embodiments, the time of the primary solution treatment is 0.5 to 1 h.

[0022] In some embodiments, the secondary solution treatment is performed for 4 to 6 hours.

[0023] In some embodiments, the time of the three-stage solution treatment is 2 to 4 hours.

[0024] In some embodiments, the preparation method further comprises the steps of quenching and cooling the aluminum alloy ingot and performing aging treatment on the aluminum alloy ingot after the heat treatment.

[0025] In some embodiments, the aging treatment is performed at a temperature of 165-175°C.

[0026] In some embodiments, the aging treatment time is 6 to 10 hours.

[0027] In some embodiments, the preparation method further comprises the step of performing a pre-aging treatment on the aluminum alloy ingot after the quenching and cooling and before the aging treatment.

[0028] Single-stage aging treatment may slightly reduce the elongation of the alloy while improving strength. The method of pre-aging treatment before aging treatment is helpful for aluminum alloy to precipitate dispersed and fine strengthening phases, which can reduce the extent of reduction in elongation of aluminum alloy products and improve the strength of the alloy. Pre-aging treatment before aging treatment can make the precipitated phase dispersed and fine, thereby reducing the degree of reduction in elongation of cast aluminum alloy, further improving strength and maintaining elongation. Pre-aging treatment can form a denser GP zone, which helps to improve the strength of the alloy.

[0029] In some embodiments, the pre-aging treatment temperature is 100-120°C.

[0030] In some embodiments, the pre-aging treatment time is 2 to 4 hours.

[0031] In some embodiments, the step of making each raw material component into an aluminum alloy ingot includes the steps of melting, refining, and modifying each raw material component to make the aluminum alloy ingot.

[0032] In some embodiments, the raw material components include aluminum ingot, Al-Si master alloy, Al-Fe master alloy, Al-Cu master alloy, magnesium, Al-Sr master alloy and optionally zinc.

[0033] In some embodiments, the preparation method comprises the following steps:

[0034] 1) melting the aluminum ingot to obtain an aluminum melt;

[0035] 2) adding the Al-Si master alloy, the Al-Fe master alloy and the Al-Cu master alloy to the aluminum melt, adding the magnesium and optionally the zinc after melting, and removing the scum on the surface of the melt;

[0036] 3) adding a refining agent to the melt for refining and slagging;

[0037] 4) adding the Al-Sr master alloy into the melt for modification and degassing;

[0038] 5) Casting the melt to obtain an aluminum alloy ingot;

[0039] 6) heat treating the aluminum alloy ingot, specifically comprising:

[0040] Primary solution treatment: heating the aluminum alloy ingot from room temperature to 490-500° C. at a heating rate of 3-10° C. / min, and keeping the temperature for 0.5-1 h;

[0041] Secondary solution treatment: The aluminum alloy ingot obtained by the primary solution treatment is heated from 490-500°C to 530-540°C at a heating rate of 3-6°C / min and kept at this temperature for 4-6h;

[0042] Three-stage solution treatment: the aluminum alloy ingot obtained by the two-stage solution treatment is heated from 530-540°C to 545-555°C at a heating rate of 2-3°C / min, and kept at this temperature for 2-4h;

[0043] 7) quenching and cooling the heat-treated aluminum alloy ingot in water to room temperature;

[0044] 8) Pre-aging treatment: the alloy obtained after quenching and cooling is heated from room temperature to 100-120°C at a heating rate of 3-10°C / min and kept at this temperature for 2-4h;

[0045] 9) Aging treatment: heating the alloy after pre-aging treatment to 165-175° C. at a heating rate of 3-6° C. / min and keeping the temperature for 6-10 hours to obtain the cast aluminum alloy.

[0046] The present invention also provides a cast aluminum alloy prepared by the above-mentioned method for preparing the cast aluminum alloy.

[0047] In some embodiments, after the aging treatment, the cast aluminum alloy has a tensile strength of more than 400 MPa, a yield strength of more than 315 MPa, and an elongation of more than 6.7% at room temperature.

[0048] The present invention also provides the use of the aforementioned cast aluminum alloy in the preparation of automobile chassis structural parts, engines or transmission components.

[0049] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art:

[0050] The present invention designs a reasonable aluminum alloy composition, especially controls the contents of Zn and Cu, and the mass ratio of Cu and Mg, adjusts the solid solution scheme and the solid solution temperature, adopts a three-stage solid solution treatment, and controls the temperature of each stage of the solid solution treatment, thereby reducing the generation of a second phase that is difficult to dissolve back, ensuring the elongation of the alloy, dissolving all the Cu-containing phases back, significantly shortening the total solid solution time, reducing energy consumption, and avoiding the coarsening of the Si phase.

[0051] The present invention makes the second phase dissolve back as efficiently as possible through reasonable component design and heat treatment process, and the prepared aluminum alloy has high strength and high toughness, and can be suitable for automotive structural parts. The aluminum alloy composition and heat treatment process of the present invention realize the dissolution of the π-Fe phase, promote more Mg elements to dissolve back into the matrix, which is conducive to further improving the strength of the alloy.

[0052] The aluminum alloy composition and heat treatment process of the present invention can shorten the solid solution time, improve the solid solution efficiency, avoid further increase of Si phase, inhibit the reduction of elongation, and make the elongation of aluminum alloy products high. At the same time, the three-stage solid solution method at a specific temperature of the heat treatment process avoids overburning of the low-temperature phase and further improves the dissolution efficiency.

[0053] After aging treatment, the cast aluminum alloy of the present invention has a tensile strength of more than 400 MPa, a yield strength of more than 315 MPa and an elongation of more than 6.7% at room temperature. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 It is a schematic diagram of the solid solution stage of a specific embodiment of the present invention;

[0055] Figure 2 This is the backscattering image after heat treatment of Example 1;

[0056] Figure 3 This is the backscattering image of Example 2 after heat treatment. DETAILED DESCRIPTION

[0057] The inventors of the present application have discovered through research that after adding more than 0.3% of Cu element to the cast aluminum alloy, θ(Al2Cu) phase and Q(Al5Mg8Cu2Si6) phase will be formed. The melting temperature of the θ(Al2Cu) phase is about 500°C, and this phase dissolves very quickly when heated to near the melting temperature. And the melting temperature of the θ(Al2Cu) phase decreases with the increase of Cu content, which is approximately between 525°C and 550°C. Therefore, the solution temperature must be below the melting temperature of the Q phase and the θ phase to ensure that overburning is not caused. The prior art mostly uses a solution temperature lower than the melting temperature of the θ phase, which will result in excessive time consumption, that is, the solution time is too long. The two-stage solid solution process in the prior art first uses a solid solution temperature lower than the θ phase for heat preservation, and then heats up to near the melting temperature of the Q phase after a period of heat preservation. The two-stage solid solution method is conducive to improving the solid solution efficiency, but the aluminum alloy composition design of the prior art is unreasonable, resulting in low solid solution efficiency, long solid solution time, and the formation of a large number of intermetallic compounds. In addition, due to the inevitable presence of Fe elements, π-Fe phases will also be formed, and the π-Fe phase contains some Mg elements. After the aluminum alloy undergoes the high-temperature solid solution of the present invention, the Mg elements in the π-Fe phase will dissolve back into the matrix, and the transformed β-Fe will fuse, which can not only improve the strength of the aluminum alloy, but also reduce the damage to the elongation and maintain a high elongation.

[0058] The present invention adopts a suitable alloy composition and a three-stage solid solution heat treatment process, so that the early solid solution can efficiently and quickly dissolve all the Q phases, so as to continue to increase the temperature and ensure the dissolution of the Mg element in the π phase. Through reasonable component design and heat treatment process configuration, the heat treatment efficiency is maximized while ensuring the toughness of the alloy.

[0059] The present invention controls the Cu / Mg ratio to be greater than 2 and the Cu content to be within the range of 0.3% to 1.8%, thereby forming less Q phase and eliminating the need to use elements such as Mn, Zr, and Cr. This saves costs and reduces the generation of intermetallic compounds during the solid solution process, thereby helping to improve the dissolution efficiency. Meanwhile, the Zn element is added, the aging time is reduced, and the aging efficiency and alloy strength are improved.

[0060] In the preparation method of the present invention, the second-stage solid solution temperature in the solid solution process of the alloy is as high as 535°C, while other secondary solid solution temperatures in the prior art are generally below 520°C. Compared with other multi-stage solid solution processes, the present invention can accelerate the dissolution efficiency by greatly increasing the second-stage solid solution temperature without overburning.

[0061] The present invention adds the consideration of the dissolution of π-Fe during the solid solution process, while other existing solid solution processes usually do not consider this point. Since the first two stages of solid solution processes have already made all the Cu-containing phases with low melting points dissolve back, raising the temperature to about 550°C will not cause overburning. At this temperature, more Mg elements dissolve back into the matrix, and more nanophases are precipitated in the subsequent aging process, thereby improving the strength of the alloy. At the same time, smaller-sized β-Fe will be melted, thereby promoting the improvement of the elongation of the alloy.

[0062] The above scheme is further described below in conjunction with specific embodiments; it should be understood that these embodiments are used to illustrate the basic principles, main features and advantages of the present invention, and the present invention is not limited to the scope of the following embodiments; the implementation conditions adopted in the embodiments can be further adjusted according to specific requirements, and the implementation conditions not specified are usually the conditions in conventional experiments.

[0063] Unless otherwise specified in the following examples, all raw materials are commercially available or prepared by conventional methods in the art.

[0064] Embodiment 1:

[0065] This example provides a cast aluminum alloy and a preparation method thereof. In terms of mass percentage, the cast aluminum alloy contains: Si 7%, Mg 0.5%, Cu 1.35%, Ti 0.13%, Fe 0.13%, Sr 0.021%, and the remainder is Al and other inevitable impurities.

[0066] The preparation method of the cast aluminum alloy comprises:

[0067] 1) Material preparation: according to the set chemical composition, weigh industrial pure aluminum, Al-20% Si master alloy, pure magnesium, A1-50% Cu master alloy, A1-20% Fe master alloy, Al-10% Sr master alloy, slag remover, refining agent, etc. according to the stoichiometric ratio, and dry them;

[0068] 2) Melting aluminum ingots: placing industrial pure aluminum ingots preheated to 180°C into a melting furnace for melting at a melting temperature of 780°C until all the pure aluminum is melted;

[0069] 3) After cooling the melt of step 2) to 745° C., add Al-20% Si, Al-20% Fe, Al-50% Cu master alloys to the melt, and after all the master alloys are melted, cool to 725° C., stir manually for 3 minutes, add pure magnesium, stir manually for 4 minutes, and remove scum on the surface of the melt after standing for 15 minutes;

[0070] 4) Then cool to 695°C, let stand for 15 minutes, evenly sprinkle sodium-free covering agent on the surface of the melt, wrap the aluminum refining agent with pure aluminum foil and insert it into the graphite bell jar. The amount of refining agent is 0.2% of the melt mass. Press the bell jar into the aluminum liquid about 10 cm from the bottom of the furnace, and move it horizontally to various places in the furnace. The reaction time is about 4 minutes. After the reaction is completed, slag is removed;

[0071] 5) After slagging, the melt temperature is lowered to 730°C, and after being protected by inert gas argon, the Al-10Sr master alloy is added and pressed into the bottom of the smelting furnace for melting. After melting, it is stirred evenly, and after standing for 15 minutes, the furnace composition analysis is performed to detect the composition content of the alloy melt. After the test is qualified, degassing is performed;

[0072] 6) Degassing: The melt was heated to 720°C and degassed by passing argon for 30 minutes. After degassing, the melt was allowed to stand for 20 minutes and the sample was cast.

[0073] 7) Heat treatment and aging process:

[0074] The temperature was raised with the furnace at a rate of 3℃ / min, and the temperature was raised to 500℃ and kept for 0.5h, then raised to 535℃ at a rate of 3℃ / min and kept for 2h, then raised to 550℃ at a rate of 3℃ / min and kept for 4h, and water quenched. After quenching, it was immediately aged, first raised to 120℃ at a rate of 3℃ / min and kept for 2h, then raised to 170℃ at a rate of 3℃ / min and kept for 5h, and finally the aluminum alloy product was obtained. The backscattered photo of the aluminum alloy product is shown in the figure below. Figure 2 As shown, it can be seen that no overburning occurred under this heat treatment condition, and no Cu-containing phase was observed in the figure. Under this heat treatment system, all the Cu-containing phases were dissolved back, and no π-Fe phase was found. Part of the β-Fe phase melted at this high temperature.

[0075] Embodiment 2:

[0076] This example provides a cast aluminum alloy and a preparation method thereof. In terms of mass percentage, the cast aluminum alloy contains: Si 7%, Mg 0.4%, Cu 1.0%, Zn 0.5%, Ti 0.12%, Fe 0.14%, Sr 0.022%, and the remainder is Al and other inevitable impurities.

[0077] The preparation method of the cast aluminum alloy comprises:

[0078] 1) Material preparation: according to the set chemical composition, weigh industrial pure aluminum, Al-20% Si master alloy, pure magnesium, pure zinc, A1-50% Cu master alloy, A1-20% Fe master alloy, Al-10% Sr master alloy, slag remover, refining agent, etc. according to the stoichiometric ratio, and dry them;

[0079] 2) Melting aluminum ingots: placing industrial pure aluminum ingots preheated to 150°C into a melting furnace for melting at a melting temperature of 760°C until all the pure aluminum is melted;

[0080] 3) After cooling the melt of step 2) to 740° C., add Al-20% Si, Al-20% Fe, Al-50% Cu master alloys to the melt, and after the master alloys are completely melted, cool to 720° C., stir manually for 4 minutes, add pure magnesium and pure zinc, stir manually for 4 minutes, and remove scum on the surface of the melt after standing for 15 minutes;

[0081] 4)-6): Same as Example 1;

[0082] 7) Heat treatment and aging process:

[0083] The furnace is heated at a rate of 3℃ / min, and the temperature is raised to 495℃ and kept for 0.8h, then raised to 530℃ at a rate of 3℃ / min and kept for 2h, then raised to 545℃ at a rate of 3℃ / min and kept for 3h, water quenched, and immediately aged after quenching, first raised to 125℃ at a rate of 3℃ / min and kept for 1.5h, then raised to 170℃ at a rate of 3℃ / min and kept for 5h, and finally the aluminum alloy product is obtained. The backscattered photo of the aluminum alloy product is shown in the figure below. Figure 3 As shown, it can be seen that after the third stage of higher high-temperature solid solution, the β-Fe phase is almost completely melted, reducing the size of the Fe phase.

[0084] Embodiment 3:

[0085] This example provides a cast aluminum alloy and a preparation method thereof, which are basically the same as Example 2, except that: the composition is different, in terms of mass percentage, the cast aluminum alloy contains: Si 7%, Mg 0.48%, Cu 1.35%, Zn 1.0%, Ti0.13%, Fe 0.14%, Sr 0.021%, and the balance is Al and other inevitable impurities; and the heat treatment and aging process parameters of step 7) are not exactly the same, specifically: heating with the furnace, heating rate 3°C / min, heating to 495°C and keeping warm for 1h, then heating to 530°C at a rate of 3°C / min and keeping warm for 2h, then heating to 545°C at a rate of 3°C / min and keeping warm for 4h, water quenching, aging immediately after quenching, first heating to 120°C at a rate of 3°C / min and keeping warm for 2h, then heating to 170°C at a rate of 3°C / min and keeping warm for 5h, and finally obtaining an aluminum alloy product.

[0086] Embodiment 4:

[0087] This example provides a cast aluminum alloy and a preparation method thereof, which are basically the same as Example 2, except that: the composition is different, in terms of mass percentage, the cast aluminum alloy contains: Si 7%, Mg 0.3%, Cu 0.8%, Zn 0.8%, Ti0.13%, Fe 0.12%, Sr 0.024%, and the balance is Al and other inevitable impurities; and the heat treatment and aging process parameters of step 7) are not exactly the same, specifically: heating with the furnace, heating rate 3°C / min, heating to 495°C and keeping warm for 0.8h, then heating to 530°C at a rate of 3°C / min and keeping warm for 3h, then heating to 545°C at a rate of 3°C / min and keeping warm for 2h, water quenching, aging immediately after quenching, first heating to 115°C at a rate of 3°C / min and keeping warm for 2h, then heating to 170°C at a rate of 3°C / min and keeping warm for 5h, and finally obtaining an aluminum alloy product.

[0088] Embodiment 5:

[0089] This example provides a cast aluminum alloy and a preparation method thereof, which are basically the same as Example 2, except that: the composition is different, in terms of mass percentage, the cast aluminum alloy contains: Si 7%, Mg 0.3%, Cu 1.0%, Zn 0.8%, Ti0.12%, Fe 0.11%, Sr 0.022%, and the balance is Al and other inevitable impurities; and the heat treatment and aging process parameters of step 7) are not exactly the same, specifically: heating with the furnace, heating rate 3°C / min, heating to 495°C and keeping warm for 0.8h, then heating to 530°C at a rate of 3°C / min and keeping warm for 3h, then heating to 545°C at a rate of 3°C / min and keeping warm for 2h, water quenching, aging immediately after quenching, directly heating to 170°C at a rate of 3°C / min and keeping warm for 5h (i.e., no pre-aging treatment is performed), and finally an aluminum alloy product is obtained.

[0090] Comparative Example 1:

[0091] This example provides a cast aluminum alloy and a preparation method thereof, which is basically the same as Example 1, except that the alloy is replaced with traditional A356.

[0092] Comparative Example 2:

[0093] This example provides a cast aluminum alloy and a preparation method thereof, which is basically the same as Example 2, except that: Step 7) heat treatment and aging process parameters are not completely the same, specifically: heating with the furnace, heating rate 3℃ / min, heating to 480℃ and keeping for 0.8h, then heating to 520℃ at a rate of 3℃ / min and keeping for 2h, then heating to 530℃ at a rate of 3℃ / min and keeping for 3h, water quenching, aging immediately after quenching, first heating to 125℃ at a rate of 3℃ / min and keeping for 1.5h, then heating to 170℃ at a rate of 3℃ / min and keeping for 5h, and finally obtaining an aluminum alloy product. That is, three-stage solid solution is adopted, but the temperature of each solid solution is lower than the scope of the present invention.

[0094] Comparative Example 3:

[0095] This example provides a cast aluminum alloy and a preparation method thereof, which is basically the same as Example 2, except that: Step 7) heat treatment and aging process parameters are not completely the same, specifically: heating with the furnace, heating rate 3℃ / min, heating to 495℃ and keeping for 0.8h, then heating to 510℃ at a rate of 3℃ / min and keeping for 2h, then heating to 530℃ at a rate of 3℃ / min and keeping for 3h, water quenching, aging immediately after quenching, first heating to 125℃ at a rate of 3℃ / min and keeping for 1.5h, then heating to 170℃ at a rate of 3℃ / min and keeping for 5h, and finally obtaining an aluminum alloy product. That is, three-stage solid solution is adopted, but the temperature of the second and third stages of solid solution is lower than the scope of the present invention.

[0096] Comparative Example 4:

[0097] This example provides a cast aluminum alloy and a preparation method thereof, which is basically the same as Example 2, except that: Step 7) heat treatment and aging process parameters are not completely the same, specifically: heating with the furnace, heating rate 3℃ / min, heating to 495℃ and keeping for 4h, then heating to 535℃ at a rate of 3℃ / min and keeping for 6h, water quenching, aging immediately after quenching, first heating to 125℃ at a rate of 3℃ / min and keeping for 1.5h, then heating to 170℃ at a rate of 3℃ / min and keeping for 5h, and finally obtaining an aluminum alloy product. That is, a two-stage solid solution setting is adopted.

[0098] Performance Test:

[0099] The test method for tensile strength and yield strength at room temperature: GB / T 228-2021; the test method for elongation at room temperature: GB / T 228-2021; the results are shown in Table 1 below.

[0100] Table 1

[0101] Tensile strength / MPa Yield strength / MPa Elongation / % Example 1 420 315 8.2 Example 2 415 322 9.1 Example 3 430 328 8.2 Example 4 405 318 8.5 Example 5 401 314 6.7 Comparative Example 1 300 220 8.4 Comparative Example 2 392 295 6.0 Comparative Example 3 401 298 6.4 Comparative Example 4 398 300 6.3

[0102] It can be seen that the present invention can improve the strength and elongation of the product by adopting a three-stage solid solution setting and setting a specific temperature for each stage of solid solution.

[0103] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

[0104] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

Claims

1. A method for preparing a cast aluminum alloy, characterized in that: In terms of mass percentage, the cast aluminum alloy comprises: Si 4% to 11%, Mg 0.2% to 0.8%, Cu 0.3% to 1.8%, Ti 0.10% to 0.14%, Zn 0 to 1.0%, Fe 0.10% to 0.30%, Sr 0.015% to 0.030%, and the balance is Al and unavoidable impurities; and the total mass percentage of Zn and Cu is less than or equal to 2.0%; the mass ratio of Cu to Mg is greater than or equal to 2; The preparation method comprises the steps of preparing aluminum alloy ingots from various raw material components; and the step of heat treating the aluminum alloy ingots; the heat treatment comprises the following steps performed in sequence: Primary solution treatment: keep warm at 490-500℃; Secondary solution treatment: keep warm at 530-540℃; Level 3 solution treatment: keep warm at 545-555℃.

2. The method for preparing a cast aluminum alloy according to claim 1, characterized in that: In the cast aluminum alloy, the total mass percentage of Zn and Cu is 0.3% to 2.0%.

3. The method for preparing a cast aluminum alloy according to claim 1, characterized in that: In the cast aluminum alloy, the mass ratio of Cu to Mg is 2-9.

4. The method for preparing a cast aluminum alloy according to claim 1, characterized in that: The cast aluminum alloy includes Zn, and the mass percentage of Zn is 0.1% to 1.0%.

5. The method for preparing a cast aluminum alloy according to claim 1, characterized in that: In terms of mass percentage, Mg accounts for 0.25% to 0.5% in the cast aluminum alloy.

6. The method for preparing a cast aluminum alloy according to claim 1, characterized in that: In terms of mass percentage, Cu accounts for 0.7% to 1.4% in the cast aluminum alloy.

7. The method for preparing a cast aluminum alloy according to claim 1, characterized in that: The time of the primary solution treatment is 0.5 to 1 hour.

8. The method for preparing a cast aluminum alloy according to claim 1, characterized in that: The time of the secondary solution treatment is 4 to 6 hours.

9. The method for preparing a cast aluminum alloy according to claim 1, characterized in that: The time of the three-stage solution treatment is 2 to 4 hours.

10. The method for preparing a cast aluminum alloy according to claim 1, characterized in that: The preparation method further comprises the steps of quenching and cooling the aluminum alloy ingot and performing aging treatment after the heat treatment.

11. The method for preparing a cast aluminum alloy according to claim 10, characterized in that: The temperature of the aging treatment is 165-175° C.; and / or the time of the aging treatment is 6-10 hours.

12. The method for preparing a cast aluminum alloy according to claim 10, characterized in that: The preparation method further comprises the step of performing a pre-aging treatment on the aluminum alloy ingot after the quenching and cooling and before the aging treatment.

13. The method for preparing a cast aluminum alloy according to claim 12, characterized in that: The temperature of the pre-aging treatment is 100 to 120° C.; and / or the time of the pre-aging treatment is 2 to 4 hours.

14. The method for preparing a cast aluminum alloy according to claim 1, characterized in that: The step of making the raw material components into aluminum alloy ingots includes the steps of melting, refining, and modifying the raw material components to make the aluminum alloy ingots.

15. The method for preparing a cast aluminum alloy according to claim 1 or 14, characterized in that: The raw material components include aluminum ingot, Al-Si master alloy, Al-Fe master alloy, Al-Cu master alloy, magnesium, Al-Sr master alloy and optionally zinc.

16. The method for preparing a cast aluminum alloy according to claim 15, characterized in that: The preparation method comprises the following steps: 1) melting the aluminum ingot to obtain an aluminum melt; 2) adding the Al-Si master alloy, the Al-Fe master alloy and the Al-Cu master alloy to the aluminum melt, adding the magnesium and optionally the zinc after melting, and removing the scum on the surface of the melt; 3) adding a refining agent to the melt for refining and slagging; 4) adding the Al-Sr master alloy into the melt for modification and degassing; 5) Casting the melt to obtain an aluminum alloy ingot; 6) heat treating the aluminum alloy ingot, specifically comprising: Primary solution treatment: heating the aluminum alloy ingot from room temperature to 490-500° C. at a heating rate of 3-10° C. / min, and keeping the temperature for 0.5-1 h; Secondary solution treatment: The aluminum alloy ingot obtained by the primary solution treatment is heated from 490-500°C to 530-540°C at a heating rate of 3-6°C / min and kept at this temperature for 4-6h; Three-stage solution treatment: the aluminum alloy ingot obtained by the two-stage solution treatment is heated from 530-540°C to 545-555°C at a heating rate of 2-3°C / min, and kept at this temperature for 2-4h; 7) quenching and cooling the heat-treated aluminum alloy ingot in water to room temperature; 8) Pre-aging treatment: the alloy obtained after quenching and cooling is heated from room temperature to 100-120°C at a heating rate of 3-10°C / min and kept at this temperature for 2-4h; 9) Aging treatment: heating the alloy after pre-aging treatment to 165-175° C. at a heating rate of 3-6° C. / min and keeping the temperature for 6-10 hours to obtain the cast aluminum alloy.

17. A cast aluminum alloy prepared by the method for preparing the cast aluminum alloy according to claims 1-16.

18. Use of the cast aluminum alloy according to claim 17 in the preparation of automobile chassis structural parts, engines or transmission components.

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