Heat-treatment-free high-toughness aluminum-magnesium-silicon alloy and preparation method thereof

Abstract

The invention relates to a heat-treatment-free high-toughness aluminum-magnesium-silicon alloy and a preparation method thereof, belongs to the technical field of aluminum alloys, and solves the problems that a heat-treatment-free aluminum alloy in the prior art is not high in toughness and cannot meet the production of large thin-wall components. The invention relates to a heat-treatment-free high-toughness aluminum-magnesium-silicon alloy, which comprises the following elements in percentage by mass: 7 to 9 percent of Mg, 2 to 3 percent of Si, 0.1 to 0.4 percent of Mn, 0.05 to 0.2 percent of Ti, 0.05 to 0.1 percent of Zr, 0.01 to 0.05 percent of B, 0.01 to 0.1 percent of Cu, 0.05 to 0.2 percent of Zn, 0.05 to 0.1 percent of Ca, 0.05 to 0.1 percent of RE, 0.003 to 0.005 percent of Be, 0 to 0.15 percent of Fe, less than or equal to 0.15 percent of other uncontrollable impurity elements and the balance of Al. And preparation of the heat-treatment-free high-toughness aluminum-magnesium-silicon alloy is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of aluminum alloys, and in particular to a high-strength and tough aluminum-magnesium-silicon alloy that can be exempted from heat treatment and a preparation method thereof. Background Art

[0002] The rapid development of new energy vehicles, led by electric vehicles, has promoted the application of aluminum alloy, a lightweight material, in new energy vehicle components. When the integrated die-casting technology is applied to body structural parts, the traditional solution treatment and subsequent quenching process will cause blistering and deformation of large thin-walled structural parts, and the subsequent artificial correction will greatly increase the process cost. Therefore, the development and application of heat-treatment-free aluminum alloys have become an inevitable choice for integrated aluminum alloy die-casting components.

[0003] However, the main problem with heat-treatment-free aluminum alloys at present is that their strength and toughness cannot meet the design requirements of high-quality casting products, and both need to be further improved to meet the actual use requirements of high-quality and high-performance aluminum alloy die-castings for new energy vehicles. Summary of the invention

[0004] In view of the above analysis, an embodiment of the present invention aims to provide a high-strength and tough aluminum-magnesium-silicon alloy that can be exempted from heat treatment and a preparation method, so as to solve at least one of the problems that the existing aluminum alloys that do not require heat treatment have low strength and toughness and cannot meet the production requirements of large thin-walled components.

[0005] On the one hand, an embodiment of the present invention provides a high-strength and tough aluminum-magnesium-silicon alloy that can be exempted from heat treatment. The contents of elements in the alloy include, by mass percentage: Mg: 7% to 9%, Si: 2% to 3%, Mn: 0.1% to 0.4%, Ti: 0.05% to 0.2%, Zr: 0.05% to 0.1%, B: 0.01% to 0.05%, Cu: 0.01% to 0.1%, Zn: 0.05% to 0.2%, Ca: 0.05% to 0.1%, RE: 0.05% to 0.1%, Be: 0.003% to 0.005%, Fe: 0 to 0.15%, and the total content of other uncontrollable impurity elements is controlled to be ≤0.15%, and the balance is Al.

[0006] On the other hand, an embodiment of the present invention provides a method for preparing a high-strength and tough aluminum-magnesium-silicon alloy that can be free of heat treatment, which is used for preparing the aluminum-magnesium-silicon alloy, comprising the following steps:

[0007] Step 1, batching and smelting: Si, Mn, Cu, and Al are batched according to the mass percentage of the components and put into a smelting furnace, and Mg, Ti, Zr, B, Zn, Ca, and RE are added after the temperature is raised to 730-735°C;

[0008] Step 2, refining and pouring: degassing and refining the aluminum alloy melt obtained in step 1, then slag removal, standing and pouring;

[0009] Step 3, die casting: cooling the aluminum melt after the treatment in step 2, performing die casting, maintaining the pressure, taking out the casting, quenching, and preparing a high-strength and tough aluminum-magnesium-silicon alloy.

[0010] Preferably, in the degassing refining in step 2, the degassing method adopts the rotary blowing argon method, the degassing time is 20 to 30 minutes, and the gas flow rate is 1 to 5 L / min.

[0011] Specifically, after degassing and slagging in step 2, the mixture is allowed to stand for 20 to 30 minutes before pouring.

[0012] Furthermore, in step 3, the melt is cooled to 680-720° C. for die casting.

[0013] Furthermore, before performing the die-casting in step 3, the die-casting mold is preheated to 150-250°C.

[0014] Furthermore, the die-casting process parameters in step 3 are as follows: the speed of the melt being pressed into the mold is 0.1 to 1.5 m / s, the injection pressure ratio is 40 to 200 MPa, and the holding time is 2 to 10 s.

[0015] Furthermore, the quenching temperature in step 3 is 30-60°C.

[0016] Furthermore, the method for preparing the heat-treatment-free high-strength and tough aluminum-magnesium-silicon alloy also includes a low-temperature aging treatment at a temperature of 150 to 200° C. for a time of 20 minutes to 5 hours.

[0017] On the other hand, an embodiment of the present invention further provides a vehicle body structure die-casting, which uses the high-strength and toughness aluminum-magnesium-silicon alloy as a raw material or an alloy obtained by the heat treatment-free high-strength and toughness aluminum-magnesium-silicon alloy preparation method as a raw material. The die-casting includes a new energy vehicle subframe, a shock tower, and a battery module.

[0018] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0019] 1. The aluminum alloy of the present invention optimizes the composition of the main component elements, introduces high Mg and Si elements, forms a high volume fraction Mg2Si phase, and makes the alloy have excellent flow and casting properties, suitable for die casting. By selecting and optimizing the content of micro-alloying elements, the α-Al grains of the alloy are refined and a solid solution strengthening effect is generated in the α-Al matrix. At the same time, a Mg2Si strengthening phase is formed at the grain boundary, so that the die casting does not need heat treatment and has excellent strength and toughness in the cast state, which is particularly suitable for the production of large thin-walled structural parts;

[0020] The introduction of trace Mn elements improves the morphology of the iron-rich phase, trace Ti, B, and Zr elements refine the α-Al grains, the introduction of trace Cu and Zn elements plays a solid solution strengthening role, the introduction of trace Ca and RE elements refines the Mg2Si precipitation phase, and the introduction of trace Be elements reduces the burning and oxidation caused by the addition of Mg elements.

[0021] 2. The present invention improves the poor fluidity and thermal cracking problems of Al-Mg alloys by introducing Si element into Al-Mg alloys to form Al-Mg2Si eutectic phase. At the same time, the present invention reduces the burning and oxidation caused by the addition of Mg element by introducing trace Be element, solves the serious problem of melt oxidation and hydrogen absorption caused by high Mg content, thereby significantly improving the strength and plasticity indicators of the alloy.

[0022] 3. The die castings prepared from the aluminum alloy of the present invention have excellent strength and toughness in the cast state (without heat treatment), with a tensile strength of 330-350 MPa, a yield strength of 180-200 MPa, and an elongation of 11-13%, which are superior to the currently developed Al-Mg cast aluminum alloys.

[0023] 4. The strength and toughness of the die castings prepared by the aluminum alloy of the present invention are further improved by low-temperature aging. A large number of nano-sized Al2Cu and MgZn2 composite particles are precipitated by low-temperature aging, and the strengthening effect is significantly better than the effect of adding Cu or Zn elements alone. Due to the introduction of trace Ti and Zr elements, the size and morphology of submicron eutectic silicon and iron-rich second phase are stable and not coarsened, and the mechanical properties of the alloy are further improved, with a tensile strength of 360-380 MPa, a yield strength of 210-230 MPa, and an elongation of 9-11%.

[0024] 5. The die-castings made of the aluminum alloy of the present invention do not require heat treatment or only undergo low-temperature aging treatment (no high-temperature solution treatment is required) to meet the strength and toughness requirements of integrated body structure die-castings represented by new energy vehicle subframes, shock towers, and battery modules. This not only avoids deformation and blistering of large vehicle structural parts during high-temperature heat treatment, but also saves energy, which is in line with the dual-carbon development direction.

[0025] In the present invention, the above-mentioned technical solutions can also be combined with each other to achieve more preferred combination solutions. Other features and advantages of the present invention will be described in the subsequent description, and some advantages can become obvious from the description, or can be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained through the contents particularly pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The drawings are only for the purpose of illustrating particular embodiments and are not to be considered limiting of the present invention. Like reference symbols denote like components throughout the drawings.

[0027] Figure 1 Microstructure of the die casting prepared in Example 1 of the present invention Figure 1 ;

[0028] Figure 2 Microstructure of the die casting prepared in Example 1 of the present invention Figure 2 . DETAILED DESCRIPTION

[0029] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not used to limit the scope of the present invention.

[0030] At present, the strength and toughness of heat-treatment-free aluminum alloys are difficult to meet the design requirements of high-quality casting products. Although the existing metal mold low-pressure casting can achieve the preparation of high-strength and toughness aluminum alloys, low-pressure casting is not suitable for the production of thin-walled parts (thickness of 1 to 4 mm), and there are problems such as difficulty in designing the casting system, high requirements for melt purity and relatively low production efficiency. Therefore, there is an urgent need to develop heat-treatment-free aluminum alloys and preparation methods suitable for the production of high-strength and tough large thin-walled structural parts.

[0031] On the one hand, a specific embodiment of the present invention discloses a high-strength and tough aluminum-magnesium-silicon alloy that can be exempted from heat treatment. The contents of elements in the alloy include, by mass percentage: Mg: 7% to 9%, Si: 2% to 3%, Mn: 0.1% to 0.4%, Ti: 0.05% to 0.2%, Zr: 0.05% to 0.1%, B: 0.01% to 0.05%, Cu: 0.01% to 0.1%, Zn: 0.05% to 0.2%, Ca: 0.05% to 0.1%, RE: 0.05% to 0.1%, Be: 0.003% to 0.005%, Fe: 0 to 0.15%, and the total content of other uncontrollable impurity elements is controlled to be ≤0.15%, and the balance is Al.

[0032] The following is a detailed description of the effects and dosage of the components in the present invention:

[0033] Mg: Combines with Si element to form Mg2Si strengthening phase. When added in high amount, high volume fraction Mg2Si is formed to improve the fluidity and strength of the alloy. Too high amount will reduce the elongation of the alloy. The optimized composition is 7-9%.

[0034] Si: forms Mg2Si strengthening phase with Mg element. Too much addition will form eutectic Si phase and reduce the elongation of the alloy. The optimized composition is 2-3%.

[0035] Mn: Improves the morphology of Fe-rich phase and increases the strength and plasticity of the alloy. The optimized composition is 0.1-0.4%.

[0036] Ti: refines α-Al grains and improves alloy strength and plasticity. Too much will form coarse Al3Ti phase and reduce alloy plasticity. The optimized composition is 0.05-0.2%.

[0037] Zr: refines α-Al grains and improves alloy strength and plasticity. Too much Zr will form coarse Al3Zr phase and reduce alloy plasticity. The optimized composition is 0.05-0.1%.

[0038] B: forms TiB2 with Ti, which can serve as nucleation particles to refine α-Al grains and improve the strength and plasticity of the alloy. The optimized composition is: 0.05~0.2%.

[0039] Cu: solid solution in α-Al matrix, improves alloy strength, precipitates Al2Cu particles during low temperature aging, excessive amount reduces alloy elongation, optimized composition: 0.01~0.1%.

[0040] Zn: solid solution in α-Al matrix, improves alloy strength, precipitates MgZn2 particles during low temperature aging, excessive amount reduces alloy elongation, optimized composition: 0.01~0.1%.

[0041] Ca: refines the Mg2Si phase and improves the elongation of the alloy. Excessive Ca-rich phase forms and reduces the strength and plasticity of the alloy.

[0042] RE: refines the Mg2Si phase, improves the elongation of the alloy, and forms excessive RE-rich phase, which reduces the strength and plasticity of the alloy.

[0043] Be: reduces the burning and oxidation of Mg element. The optimized composition is 0.003-0.005%.

[0044] Fe: Reduces the tendency of castings to stick to the mold. Excessive addition will form a needle-shaped Fe-rich phase, reducing the strength and plasticity of the alloy. After optimization, the composition is 0-0.15%.

[0045] like Figure 1 As shown, the composition structure of the high-strength and tough aluminum-magnesium-silicon alloy of the present invention includes dendritic primary α-Al and Mg2Si phases; Figure 2 for Figure 1 Magnified microstructure shows fine fibrous Mg2Si morphology, which provides the alloy with higher strength and toughness.

[0046] The RE element is La, Ce or a mixture of several of them, which have the same function and the proportion is not limited.

[0047] The aluminum alloy forms a high volume fraction Mg2Si strengthening phase by introducing high Mg and Si elements to exert a second phase strengthening effect; trace Mn elements are introduced to improve the morphology of the iron-rich phase, trace Ti, B, and Zr elements are introduced to refine α-Al grains, trace Cu and Zn elements are introduced to exert a solid solution strengthening effect, trace Ca and RE elements are introduced to refine the Mg2Si precipitation phase, causing the morphology of the Mg2Si precipitation phase to undergo a fiberization transformation, and trace Be elements are introduced to reduce the burning and oxidation caused by the addition of Mg elements.

[0048] The high-strength and toughness aluminum-magnesium-silicon alloy has a small crystallization temperature interval, and its Mg2Si phase has a large solidification latent heat and specific heat capacity; due to the refinement of α-Al grains and the refinement of Mg2Si precipitation phases, the alloy of the present invention has the characteristics of small linear shrinkage coefficient, thermal cracking and shrinkage tendency, etc., and can well take into account the requirements of both mechanical properties and casting properties. Therefore, the alloy is not only suitable for die casting, but also can be used for low-pressure casting, metal mold casting, extrusion casting, sand casting and semi-solid casting, and is widely used; preferably, the aluminum alloy is prepared by die casting, which has a simple process and low requirements on melt purity, and does not require heat treatment or only requires low-temperature aging treatment to obtain high strength and toughness.

[0049] On the other hand, a specific embodiment of the present invention further discloses a method for preparing a high-strength and tough aluminum-magnesium-silicon alloy that can be free of heat treatment, comprising the following steps:

[0050] Step 1, batching and smelting: Si, Mn, Cu, and Al are batched according to the mass percentage of the components and put into a smelting furnace, and Mg, Ti, Zr, B, Zn, Ca, and RE are added after the temperature is raised to 730-735°C;

[0051] Step 2, refining and pouring: degassing and refining the aluminum alloy melt obtained in step 1, then slag removal, standing and pouring;

[0052] Step 3, die casting: cooling the aluminum melt after the treatment in step 2, performing die casting, maintaining the pressure, taking out the casting, quenching, and preparing the aluminum alloy die casting.

[0053] Preferably, the aluminum in the raw materials of step 1 is an industrial pure aluminum ingot, the magnesium is a pure magnesium ingot, the zinc is a pure zinc ingot, the silicon is an aluminum-silicon master alloy, the manganese is an aluminum-manganese master alloy, the titanium is an aluminum-titanium master alloy, the zirconium is an aluminum-zirconium master alloy, the boron is an aluminum-boron master alloy, the copper is an aluminum-copper master alloy, the calcium is an aluminum-calcium master alloy, the rare earth is an aluminum-rare earth master alloy, and the beryllium is an aluminum-beryllium master alloy;

[0054] Moreover, adding alloying elements such as Zr, Ti, and B at higher temperatures can reduce composition segregation and improve the accuracy of composition control, thereby ensuring the stability of the alloy's performance, more effectively refining the grains, and improving the alloy's strength and toughness.

[0055] Furthermore, in the degassing refining described in step 2, the degassing method adopts a rotary argon blowing method.

[0056] Specifically, during the degassing and refining process, the degassing time is 20 to 30 minutes, and the gas flow rate is 1 to 5 L / min; the introduction of argon gas can effectively replace the hydrogen in the aluminum melt, reduce the hydrogen content in the aluminum melt, and thus improve the mechanical properties of the aluminum alloy; through the rotary blowing method, the argon gas can be broken into fine bubbles, and the bubbles take away the hydrogen and slag in the aluminum liquid during the rising process, thereby achieving the purpose of purifying the aluminum liquid.

[0057] It should be noted that in step 2, after slagging, the casting is performed after standing for 20 to 30 minutes; during the standing process, non-metallic inclusions in the melt have time to float to the surface of the melt, thereby reducing the inclusion content in the casting, improving the purity and achieving the best degassing effect.

[0058] Furthermore, in step 3, cooling the melt to 680-720° C. helps balance fluidity, reduce defects, and extend mold life.

[0059] Specifically, before performing the die-casting in step 3, the die-casting mold is preheated to a temperature of 150-250°C.

[0060] Improper mold temperature setting will affect the performance of the casting. Too low a temperature will lead to difficulty in casting molding, incomplete filling and cold shut defects; too high a temperature will lead to defects such as bubbles, sticking and shrinkage holes on the casting surface, and reduce the service life of the mold.

[0061] Furthermore, the die-casting process parameters in step 3 are as follows: the speed of the melt being pressed into the mold is 0.1 to 1.5 m / s, the injection pressure ratio is 40 to 200 MPa, and the holding time is 2 to 10 s.

[0062] Specifically, the speed of pressing into the mold is 0.1m / s, 0.5m / s, 1m / s, and 1.5m / s, the injection pressure is 40MPa, 50MPa, 80MPa, 100MPa, 150MPa, and 200MPa, and the holding time is 2s, 5s, 8s, and 10s.

[0063] Preferably, the quenching temperature in step 3 is 30-60° C., which increases the surface hardness of the casting and reduces wear and corrosion of the casting during use.

[0064] The aluminum alloy die casting obtained in step 3 has a tensile strength of 330-350 MPa, a yield strength of 180-200 MPa, and an elongation of 11-13% in the cast state.

[0065] Furthermore, the method for preparing the heat-treatment-free high-strength and tough aluminum-magnesium-silicon alloy further includes low-temperature aging treatment, and the strength and toughness of the aluminum alloy casting are further improved by low-temperature aging;

[0066] Preferably, the low-temperature aging temperature is 150-200° C., and the time is 20 min-5 h.

[0067] A large number of nano-sized Al2Cu and MgZn2 composite particles are precipitated through low-temperature aging, and the strengthening effect is significantly better than that of adding Cu or Zn elements alone. Due to the introduction of trace Ti and Zr elements, the size and morphology of submicron eutectic silicon and iron-rich second phase are stable and not coarsened, and the mechanical properties of the alloy are further improved. The aluminum alloy castings after low-temperature aging treatment have a tensile strength of 360-380MPa, a yield strength of 210-230MPa, and an elongation of 9-11%.

[0068] On the other hand, an embodiment of the present invention further provides a vehicle body structure die-casting, which uses the high-strength and toughness aluminum-magnesium-silicon alloy as a raw material or an alloy obtained by the heat treatment-free high-strength and toughness aluminum-magnesium-silicon alloy preparation method as a raw material. The die-casting includes a new energy vehicle subframe, a shock tower, and a battery module.

[0069] In summary, the aluminum alloy of the present invention optimizes the composition of the main component elements, introduces high Mg and Si elements, forms a high volume fraction Mg2Si phase, so that the alloy has excellent flow and casting properties and is suitable for die casting. By selecting and optimizing the content of micro-alloying elements, the alloy α-Al grains are refined and a solid solution strengthening effect is produced in the α-Al matrix. At the same time, a second phase strengthening phase is formed at the grain boundary, so that the die casting does not require heat treatment and has excellent strength and toughness in the cast state, which is particularly suitable for the production of large thin-walled structural parts; trace Mn elements are introduced to improve the morphology of the iron-rich phase, trace Ti, B, and Zr elements are used to refine the α-Al grains, trace Cu and Zn elements are introduced to exert a solid solution strengthening effect, trace Ca and RE elements are introduced to refine the Mg2Si precipitation phase, and trace Be elements are introduced to reduce the burning and oxidation generated when the Mg element is added, which solves the serious problem of melt oxidation and hydrogen absorption caused by high Mg content, thereby significantly improving the strength and plasticity indicators of the alloy.

[0070] The heat treatment-free high-strength and tough aluminum-magnesium-silicon alloy and its preparation method of the present invention are described below in conjunction with specific embodiments.

[0071] Example 1

[0072] The present embodiment provides a high-strength and toughness cast aluminum alloy that does not require heat treatment and a preparation method thereof.

[0073] The specific components and mass percentages are shown in Table 1.

[0074] The specific preparation process includes the following steps:

[0075] Step 1, batching and smelting: put the calculated and weighed industrial pure aluminum ingots, aluminum silicon master alloys, aluminum manganese master alloys, and aluminum copper master alloys into a smelting furnace, heat up to 730° C., and after they are completely melted, add the calculated and weighed pure magnesium ingots, pure zinc ingots, aluminum titanium master alloys, aluminum zirconium master alloys, aluminum boron master alloys, aluminum calcium master alloys, aluminum rare earth master alloys, and aluminum beryllium master alloys into the melt;

[0076] Step 2, refining and pouring: the aluminum alloy melt obtained in step 1 is degassed and refined by a rotary argon injection method, the degassing time is 20 minutes, the gas flow rate is 1L / min, and then the scum on the surface of the melt is skimmed off, and then the melt is kept warm and allowed to stand for 30 minutes, and the scum on the surface of the melt is skimmed off again after standing;

[0077] Step 3, die casting: cool the melt prepared in step 2 to 690°C, pour the aluminum alloy liquid into the pressure chamber of the die casting machine for die casting, and then the molten metal is pressed into the mold at a speed of 0.1m / s under the action of the die casting machine punch. The mold preheating temperature is 200°C, the injection pressure is 150MPa, the holding time is 5s, and the casting is taken out and quenched at a quenching temperature of 50°C to obtain a cast aluminum alloy structural part.

[0078] Step 4, low temperature aging heat treatment: the aluminum alloy structural part obtained in step 3 is subjected to low temperature aging heat treatment, the aging temperature is 200°C, the time is 2h, and then the component is taken out and air-cooled to obtain a heat-treated aluminum alloy structural part.

[0079] The tensile strength, yield strength and elongation of the aluminum alloy structural parts in the cast state and heat treatment state (only aging treatment, no high temperature solution treatment) were measured respectively. The specific results are shown in Table 2.

[0080] Example 2

[0081] The present embodiment provides a high-strength and toughness cast aluminum alloy that does not require heat treatment and a preparation method thereof.

[0082] The specific components and mass percentages are shown in Table 1.

[0083] The specific preparation process includes the following steps:

[0084] Steps 1 to 3 are the same as those in Example 1;

[0085] Step 4, low temperature aging heat treatment: The aluminum alloy die casting obtained in step (3) is subjected to low temperature aging heat treatment at an aging temperature of 180°C for 3 hours, after which the casting is taken out and air-cooled.

[0086] The tensile strength, yield strength and elongation of the aluminum alloy structural parts in the cast state and heat treatment state (only aging treatment, no high temperature solution treatment) were measured respectively. The specific results are shown in Table 2.

[0087] Example 3

[0088] The present embodiment provides a high-strength and toughness cast aluminum alloy that does not require heat treatment and a preparation method thereof.

[0089] The specific components and mass percentages are shown in Table 1.

[0090] The specific preparation process includes the following steps:

[0091] Steps 1 to 3 are substantially the same as those of Example 1, except that in step 3, the injection punch speed is 1 m / s, the injection pressure is 100 MPa, and the holding time is 8 s;

[0092] Step 4, low temperature aging heat treatment: The aluminum alloy die casting obtained in step (3) is subjected to low temperature aging heat treatment at an aging temperature of 180°C for 3 hours, after which the casting is taken out and air-cooled.

[0093] The tensile strength, yield strength and elongation of the aluminum alloy structural parts in the cast state and heat treatment state (only aging treatment, no high temperature solution treatment) were measured respectively. The specific results are shown in Table 2.

[0094] Example 4

[0095] The present embodiment provides a high-strength and toughness cast aluminum alloy that does not require heat treatment and a preparation method thereof.

[0096] The specific components and mass percentages are shown in Table 1.

[0097] The specific preparation process includes the following steps:

[0098] Steps 1 to 3 are substantially the same as those of Example 1, except that in step 3, the injection punch speed is 1.5 m / s, the injection pressure is 60 MPa, and the holding time is 10 s;

[0099] Step 4, low temperature aging heat treatment: The aluminum alloy die casting obtained in step (3) is subjected to low temperature aging heat treatment at an aging temperature of 180°C for 3 hours, after which the casting is taken out and air-cooled.

[0100] The tensile strength, yield strength and elongation of the aluminum alloy structural parts in the cast state and heat treatment state (only aging treatment, no high temperature solution treatment) were measured respectively. The specific results are shown in Table 2.

[0101] Comparative Example 1

[0102] The present embodiment provides a high-strength and toughness cast aluminum alloy that does not require heat treatment and a preparation method thereof.

[0103] The specific components and mass percentages are shown in Table 1.

[0104] The specific preparation process includes the following steps:

[0105] Steps 1 to 3 are the same as those in Example 1;

[0106] Step 4, low temperature aging heat treatment: The aluminum alloy die casting obtained in step (3) is subjected to low temperature aging heat treatment at an aging temperature of 170°C for 1 hour, after which the casting is taken out and air-cooled.

[0107] The tensile strength, yield strength and elongation of the aluminum alloy structural parts in the cast state and heat treatment state (only aging treatment, no high temperature solution treatment) were measured respectively. The specific results are shown in Table 2.

[0108] Comparative Example 2

[0109] The present embodiment provides a high-strength and toughness cast aluminum alloy that does not require heat treatment and a preparation method thereof.

[0110] The specific components and mass percentages are shown in Table 1.

[0111] The specific preparation process includes the following steps:

[0112] Steps 1 to 3 are the same as those in Example 1;

[0113] Step 4, low temperature aging heat treatment: The aluminum alloy die casting obtained in step (3) is subjected to low temperature aging heat treatment at an aging temperature of 160° C. for 4 h, after which the casting is taken out and air-cooled.

[0114] The tensile strength, yield strength and elongation of the aluminum alloy structural parts in the cast state and heat treatment state (only aging treatment, no high temperature solution treatment) were measured respectively. The specific results are shown in Table 2.

[0115] Comparative Example 3

[0116] The present embodiment provides a high-strength and toughness cast aluminum alloy that does not require heat treatment and a preparation method thereof.

[0117] The specific components and mass percentages are shown in Table 1.

[0118] The specific preparation process includes the following steps:

[0119] Steps 1 to 3 are the same as those in Example 1;

[0120] Step 4, low temperature aging heat treatment: The aluminum alloy die casting obtained in step (3) is subjected to low temperature aging heat treatment at an aging temperature of 150° C. for 5 h, after which the casting is taken out and air-cooled.

[0121] The tensile strength, yield strength and elongation of the aluminum alloy structural parts in the cast state and heat treatment state (only aging treatment, no high temperature solution treatment) were measured respectively. The specific results are shown in Table 2.

[0122] Comparative Example 4

[0123] The present embodiment provides a high-strength and toughness cast aluminum alloy that does not require heat treatment and a preparation method thereof.

[0124] The specific components and mass percentages are shown in Table 1.

[0125] The specific preparation process includes the following steps:

[0126] Steps 1 to 3 are the same as those in Example 1;

[0127] Step 4, low temperature aging heat treatment: The aluminum alloy die casting obtained in step (3) is subjected to low temperature aging heat treatment at an aging temperature of 180°C for 30 minutes, after which the casting is taken out and air-cooled.

[0128] The tensile strength, yield strength and elongation of the aluminum alloy structural parts in the cast state and heat treatment state (only aging treatment, no high temperature solution treatment) were measured respectively. The specific results are shown in Table 2.

[0129] Comparative Example 5

[0130] The present embodiment provides a high-strength and toughness cast aluminum alloy that does not require heat treatment and a preparation method thereof.

[0131] The specific components and mass percentages are shown in Table 1.

[0132] The specific preparation process includes the following steps:

[0133] Steps 1 to 3 are the same as those in Example 1;

[0134] Step 4, low temperature aging heat treatment: The aluminum alloy die casting obtained in step (3) is subjected to low temperature aging heat treatment at an aging temperature of 190° C. for 4 h, after which the casting is taken out and air-cooled.

[0135] The tensile strength, yield strength and elongation of the aluminum alloy structural parts in the cast state and heat treatment state (only aging treatment, no high temperature solution treatment) were measured respectively. The specific results are shown in Table 2.

[0136] Comparative Example 6

[0137] The present embodiment provides a high-strength and toughness cast aluminum alloy that does not require heat treatment and a preparation method thereof.

[0138] The specific components and mass percentages are shown in Table 1.

[0139] The specific preparation process includes the following steps:

[0140] Steps 1 to 3 are the same as those in Example 1;

[0141] Step 4: low temperature aging heat treatment: the aluminum alloy die casting obtained in step (3) is subjected to low temperature aging heat treatment at an aging temperature of 200°C for 5 hours, after which the casting is taken out and air-cooled.

[0142] The tensile strength, yield strength and elongation of the aluminum alloy structural parts in the cast state and heat treatment state (only aging treatment, no high temperature solution treatment) were measured respectively. The specific results are shown in Table 2.

[0143] Comparative Example 7

[0144] The present embodiment provides a high-strength and toughness cast aluminum alloy that does not require heat treatment and a preparation method thereof.

[0145] The specific components and mass percentages are shown in Table 1.

[0146] The specific preparation process includes the following steps:

[0147] Steps 1 to 3 are the same as those in Example 1;

[0148] Step 4: low temperature aging heat treatment: the aluminum alloy die casting obtained in step (3) is subjected to low temperature aging heat treatment at an aging temperature of 200°C for 5 hours, after which the casting is taken out and air-cooled.

[0149] The tensile strength, yield strength and elongation of the aluminum alloy structural parts in the cast state and heat treatment state (only aging treatment, no high temperature solution treatment) were measured respectively. The specific results are shown in Table 2.

[0150] Comparative Example 8

[0151] The present embodiment provides a high-strength and toughness cast aluminum alloy that does not require heat treatment and a preparation method thereof.

[0152] The specific components and mass percentages are shown in Table 1.

[0153] The specific preparation process includes the following steps:

[0154] Steps 1 to 3 are the same as those in Example 1;

[0155] Step 4: low temperature aging heat treatment: the aluminum alloy die casting obtained in step (3) is subjected to low temperature aging heat treatment at an aging temperature of 200°C for 5 hours, after which the casting is taken out and air-cooled.

[0156] The tensile strength, yield strength and elongation of the aluminum alloy structural parts in the cast state and heat treatment state (only aging treatment, no high temperature solution treatment) were measured respectively. The specific results are shown in Table 2.

[0157] Comparative Example 9

[0158] The present embodiment provides a high-strength and toughness cast aluminum alloy that does not require heat treatment and a preparation method thereof.

[0159] The specific components and mass percentages are shown in Table 1, which are the same as those in Example 1.

[0160] The specific preparation process includes the following steps:

[0161] Step 1 and step 2 are the same as those in Example 1, except that step 3 adopts a gravity casting method to pour the aluminum alloy melt into a mold for gravity casting.

[0162] The tensile strength, yield strength and elongation of the aluminum alloy structural parts in the cast condition were measured. The specific results are shown in Table 2.

[0163] Table 1 Specific composition and mass percentage (wt%) of aluminum alloy in the embodiment and comparative example

[0164]

[0165]

[0166] Table 2 Mechanical properties of aluminum alloy structural parts in the casting state and heat treatment state in the embodiment and comparative example

[0167] Example Tensile strength(MPa) Yield strength (MPa) Elongation(%) Example 1 (as-cast) 342 186 11.7 Example 2 (as-cast) 344 198 12.3 Example 3 (as-cast) 338 182 12.8 Example 4 (as-cast) 341 185 11.0 Comparative Example 1 (As-cast) 282 170 3.6 Comparative Example 2 (As-cast) 332 175 9.8 Comparative Example 3 (As-cast) 330 180 10.6 Comparative Example 4 (As-cast) 321 176 8.9 Comparative Example 5 (As-cast) 335 172 7.5 Comparative Example 6 (As-cast) 338 150 6.2 Comparative Example 7 (As-cast) 300 166 8.2 Comparative Example 8 (As-cast) 295 170 7.8 Comparative Example 9 (As-cast) 335 180 10.8 Example 1 (Aging Treatment) 360 203 9.0 Example 2 (Aging Treatment) 362 217 9.3 Example 3 (Aging Treatment) 372 222 10.5 Embodiment 4 (aging treatment) 368 215 9.8 Comparative Example 1 (Aging Treatment) 301 208 1.8 Comparative Example 2 (Aging Treatment) 344 195 7.2 Comparative Example 3 (Aging Treatment) 346 194 8.2 Comparative Example 4 (Aging Treatment) 348 185 8.5 Comparative Example 5 (Aging Treatment) 344 186 6.2 Comparative Example 6 (Aging Treatment) 352 170 6.0 Comparative Example 7 (Aging Treatment) 330 175 8.2 Comparative Example 8 (Aging Treatment) 335 182 7.2

[0168] It can be seen from Table 1 that the high-strength and toughness aluminum alloy die-cast structural parts prepared in Examples 1-4 have better strength and toughness than the aluminum alloy die-cast structural parts prepared in Comparative Examples 1-9. The high-strength and toughness aluminum alloy die-cast structural parts prepared in Examples 1-4 have excellent strength and toughness in the cast state, and their mechanical properties can be further improved by aging heat treatment. Therefore, the high-strength and toughness cast aluminum alloy of the present invention that can be free of heat treatment has broad application prospects in the field of integrated die-casting forming of new energy vehicles.

[0169] The alloy element composition or content of Comparative Examples 1 to 8 does not meet the requirements of the present invention, wherein excessive Mg is added in Comparative Example 1, Mn is not added in Comparative Example 2, Ti, Zr, and B are not contained in Comparative Example 3, Cu and Zn are not added in Comparative Example 4, Cu is not added in Comparative Example 7, and Zn is not contained in Comparative Example 8. As a result, the tensile strength, yield strength, and elongation of the aluminum alloy structural parts in the cast and heat-treated conditions are reduced to varying degrees compared with the embodiments.

[0170] Comparative Example 9 adopts gravity casting. Although its cast strength and toughness are not as good as those of Example 1, since the alloy of the present invention has the characteristics of linear shrinkage coefficient, small thermal cracking and shrinkage tendency, and takes into account the requirements of mechanical properties and casting properties, gravity casting can also achieve better mechanical properties.

[0171] In summary, the aluminum alloy of the present invention optimizes the composition of the main component elements, introduces high Mg and Si elements, forms a high volume fraction Mg2Si phase, so that the alloy has excellent flow and casting properties and is suitable for die casting. By selecting and optimizing the content of micro-alloying elements, the alloy α-Al grains are refined and a solid solution strengthening effect is produced in the α-Al matrix. At the same time, a second phase strengthening phase is formed at the grain boundary, so that the die casting does not require heat treatment and has excellent strength and toughness in the cast state, which is particularly suitable for the production of large thin-walled structural parts; trace Mn elements are introduced to improve the morphology of the iron-rich phase, trace Ti, B, and Zr elements are used to refine the α-Al grains, trace Cu and Zn elements are introduced to exert a solid solution strengthening effect, trace Ca and RE elements are introduced to refine the Mg2Si precipitation phase, and trace Be elements are introduced to reduce the burning and oxidation generated when the Mg element is added, which solves the serious problem of melt oxidation and hydrogen absorption caused by high Mg content, thereby significantly improving the strength and plasticity indicators of the alloy.

[0172] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A high-strength and tough aluminum-magnesium-silicon alloy that can be free of heat treatment, characterized in that: The contents of elements in the alloy include, by mass percentage: Mg: 7% to 9%, Si: 2% to 3%, Mn: 0.1% to 0.4%, Ti: 0.05% to 0.2%, Zr: 0.05% to 0.1%, B: 0.01% to 0.05%, Cu: 0.01% to 0.1%, Zn: 0.05% to 0.2%, Ca: 0.05% to 0.1%, RE: 0.05% to 0.1%, Be: 0.003% to 0.005%, Fe: 0 to 0.15%, and the total content of other uncontrollable impurity elements is controlled to be ≤0.15%, and the balance is Al.

2. A method for preparing a high-strength and tough aluminum-magnesium-silicon alloy that can be free of heat treatment, characterized in that: The preparation method for the aluminum-magnesium-silicon alloy according to claim 1 comprises the following steps: Step 1, batching and smelting: Si, Mn, Cu, and Al are batched according to the mass percentage of the components and put into a smelting furnace, and Mg, Ti, Zr, B, Zn, Ca, and RE are added after the temperature is raised to 730-735°C; Step 2, refining and pouring: degassing and refining the aluminum alloy melt obtained in step 1, then slag removal, standing and pouring; Step 3, die casting: cooling the aluminum melt after the treatment in step 2, performing die casting, maintaining the pressure, taking out the casting, quenching, and preparing a high-strength and tough aluminum-magnesium-silicon alloy.

3. The preparation method according to claim 2, characterized in that: The degassing refining in step 2 adopts a rotary argon blowing method, the degassing time is 20 to 30 minutes, and the gas flow rate is 1 to 5 L / min.

4. The preparation method according to claim 3, characterized in that: In step 2, after degassing and slagging, let it stand for 20 to 30 minutes before pouring.

5. The preparation method according to claim 2, characterized in that: In step 3, the melt is cooled to 680-720° C. for die casting.

6. The preparation method according to claim 2, characterized in that: Before performing die casting in step 3, the die casting mold is preheated to 150-250°C.

7. The preparation method according to claim 2, characterized in that: The die-casting process parameters in step 3 are: the speed of the melt being pressed into the mold is 0.1-1.5 m / s, the injection pressure is 40-200 MPa, and the holding time is 2-10 s.

8. The preparation method according to claim 2, characterized in that: The quenching temperature in step 3 is 30-60°C.

9. The preparation method according to claim 2, characterized in that: The preparation method also includes low-temperature aging treatment, the temperature is 150-200° C., and the time is 20 minutes to 5 hours.

10. A vehicle body structure die casting, characterized in that: The high-strength and toughness aluminum-magnesium-silicon alloy described in claim 1 is used as a raw material, or the alloy prepared by the preparation method described in claims 2 to 9 is used as a raw material, and it is characterized in that the die-casting includes a new energy vehicle subframe, a shock tower, and a battery module.

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