Low-cost high-plasticity cast Al-Mg alloy and preparation method thereof

Abstract

The invention relates to a low-cost high-plasticity cast Al-Mg alloy and a preparation method thereof, and belongs to the field of metal materials and metallurgy. The alloy comprises the following elements of, by mass, 3.5%-4.5% of Mg, 0.5%-1.5% of Fe, 1.75%-2.25% of Si, 0.1%-0.4% of Mo, 0.02%-0.10% of Ti, 0.05%-0.2% of Mn and the balance Al. The raw materials are subjected to melting, refining, refining, external field treatment and gravity casting to obtain the alloy material. The prepared alloy is excellent in casting performance, the content of Fe, Mo and Si elements in the components is high, low-price secondary aluminum can be adopted as the raw material, the alloy can obtain high plasticity without heat treatment, the process is simple, the production efficiency is high, the production cost is remarkably reduced, the progress is remarkable, and the application range of the Al-Mg series cast aluminum alloy is widened.

Description

Technical Field

[0001] This invention relates to the field of aluminum alloys, and more particularly to a low-cost, high-plasticity cast Al-Mg alloy and its preparation method. Background Technology

[0002] The development of integrated die-casting technology has accelerated the process of automotive lightweighting and is of great significance for achieving dual-carbon goals. This technology allows castings to achieve high strength and toughness without heat treatment. Currently, the most mature materials used are mainly Al-Si alloys, but the Fe content in these alloys is strictly limited, generally below 0.4%, resulting in high alloy costs. Furthermore, under gravity casting conditions, Al-Si alloys typically exhibit a yield strength of 70-80 MPa and an elongation of 6-8%. In contrast, Al-Mg cast aluminum alloys possess high strength and good plasticity, making them a potential heat-treatment-free material. However, their application range is limited due to their lower casting formability compared to Al-Si alloys.

[0003] Chinese patent CN104630578A discloses a high-plasticity cast aluminum alloy and its preparation method. The composition is: Si 7.5-13.5%, Mg 0.5-0.8%, Mn 0.2-0.5%, Ti 0.1-0.4%, RE 0.01-1%, Fe ≤ 0.4%, P ≤ 100ppm, Sr 100-600ppm, with the balance being Al. The prepared material achieves an elongation at break of 18%. However, due to the need for solution aging treatment, it cannot be used in heat-treated materials. Furthermore, the Fe content is below 0.4%, making it impossible to use recycled aluminum for preparation, resulting in high costs. Chinese patent CN110079714A discloses a non-heat-treated, high-strength, high-toughness die-cast aluminum-magnesium-copper alloy and its preparation method. The composition is: Mg 4.5-7.5%; Mn 0.6-0.9%; Cu 0.5-1.5%; Ti 0.1-0.2%; Be 0.004-0.006%; RE 0.01-0.2%; other impurities ≤0.4%, balance Al. This alloy can achieve the following under die-casting conditions: yield strength 180-200 MPa, tensile strength 310-330 MPa, and elongation 6-10%. While the alloy exhibits high strength, its high Mg content leads to a high tendency for hot cracking during casting. Furthermore, the Fe and Si impurities are both less than 0.4%, making it unsuitable for use with recycled aluminum, resulting in high costs. Therefore, how to prepare high-plasticity and high-toughness aluminum alloys using low-cost recycled aluminum has become a pressing technical challenge for the automotive industry. Summary of the Invention

[0004] To address the aforementioned problems in the prior art, this invention provides a low-cost, high-plasticity cast Al-Mg alloy material and its preparation method.

[0005] To achieve the above objectives, the main technical solutions adopted by the present invention include:

[0006] A low-cost, high-plasticity cast Al-Mg alloy comprises the following elements by mass percentage: Mg 3.5-4.5%, Fe 0.5-1.5%, Si 1.75-2.25%, Mo 0.1-0.4%, Ti 0.05-0.10%, Mn 0.05-0.2%, with the balance being Al.

[0007] In one embodiment of the present invention, the mass ratio of Mg to Si in the alloy is Mg:Si = 1.8~2.1:1.

[0008] In one embodiment of the present invention, the mass ratio of Mo to Mn in the alloy is Mo:Mn = 1.5~2:1.

[0009] In one embodiment of the present invention, the content of AlFe(Mn,Mo)Si phase in the alloy is 0.18-0.62%.

[0010] In one embodiment of the present invention, the average size of the AlFe(Mn,Mo)Si phase is 4.7-19.4 μm.

[0011] A method for preparing a low-cost, high-plasticity cast Al-Mg alloy includes the following steps:

[0012] S1: Prepare the melt: Melt the waste aluminum ingot, blow air, remove slag, obtain a pure melt, and measure the composition; then heat the aluminum liquid to 750-780℃ and add aluminum manganese and aluminum silicon master alloys to supplement Mn and Si elements to the target content;

[0013] S2: Remelt the Al5Mo master alloy, hold it at 830-850℃ for 10-20 min, then cool it down to 730-750℃ and sonicate it for 10-15 min, and then add it to the S1 melt;

[0014] S3: After the mixed melt cools down to 680-700℃, add pure magnesium and hold for 30 minutes; after heating to 710-720℃, add aluminum-titanium-boron master alloy, melt it completely and let it stand for later use.

[0015] S4: Refined;

[0016] S5: Field handling;

[0017] S6: Molding.

[0018] In one embodiment of the present invention, the Al5Mo master alloy is melted in an induction melting furnace in step S2; the melt obtained in step S2 is added to the melt in S1 through a ceramic conduit.

[0019] In one embodiment of the present invention, the refining step S4 includes further heating the melt to 740-760°C, mixing high-purity argon gas and refining agent and introducing them into the melt, and stirring with a graphite rotor for 5-10 minutes.

[0020] In one embodiment of the present invention, the field treatment of step S5 includes ultrasonic treatment of the aluminum alloy melt at 590-620°C; the ultrasonic treatment power is 200-500W, the output frequency is 19-21kHz, and the time is 5-30min.

[0021] In one embodiment of the present invention, an aluminum alloy casting is obtained after forming in step S6; the tensile strength of the aluminum alloy casting is 243~263MPa and the elongation is 9.9~11.6%.

[0022] The beneficial effects of this invention are as follows: It creatively combines Mn and Mo, and through optimized alloy composition design, allows the Fe content to be controlled within the range of 0.5-1.5%. Simultaneously, even with a high Fe content, the Fe-rich phase does not agglomerate or coarsen into needle-like structures, and the elongation of the material does not deteriorate. This allows for the use of low-cost scrap aluminum ingots and reduces the amount of high-cost Mo added, thus lowering raw material costs. Furthermore, the gravity casting and heat-free preparation process ensures that the prepared Al-Mg alloy still possesses good mechanical properties. Simultaneously, by controlling the specific element ratios and phase structure, the alloy achieves high plasticity in the as-cast state, eliminating the need for subsequent heat treatment and enabling compatibility with high-Fe-content recycled aluminum, thereby reducing material costs. The high plasticity in the as-cast state meets the requirements for heat-free processing. Compared with existing technologies, the aluminum alloy material prepared by this invention has significantly lower costs, and the preparation method is simple, with good process stability and high process controllability. Attached Figure Description

[0023] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained from these drawings without creative effort.

[0024] Figure 1 These are as-cast metallographic images of the alloy prepared in Example 1 of this invention;

[0025] Figure 2 These are microstructure photographs of castings made from the alloy prepared in Example 3 of this invention;

[0026] Figure 3 These are the energy dispersive spectroscopy (EDS) results of the alloy prepared in Example 3 of this invention;

[0027] Figure 4 These are the tensile curves of the alloys prepared in Examples 1 and 2 of this invention. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] This application proposes a low-cost, high-plasticity cast Al-Mg alloy comprising the following elements by mass percentage: Mg 3.5-4.5%, Fe 0.5-1.5%, Si 1.75-2.25%, Mo 0.1-0.4%, Ti 0.05-0.10%, Mn 0.05-0.2%, with the balance being Al.

[0030] In this embodiment, a low-cost, high-plasticity cast Al-Mg alloy contains the following elements by mass percentage. The magnesium content is 3.5-4.5%. In practical applications, this content can be achieved by adding pure magnesium blocks or aluminum-magnesium master alloys during the smelting process. For example, industrial-grade magnesium ingots can be directly added to the molten aluminum, or a pre-alloyed aluminum-magnesium master alloy can be used as a supplement. This is mainly to provide a foundation for the alloy's strength. Furthermore, the iron content is set within the range of 0.5-1.5%. Specifically, this can be achieved by using recycled aluminum raw materials with a high iron content, such as using scrap aluminum ingots with an Fe content of 1.0% as the base material, or by mixing aluminum materials from different sources. This allows the use of low-cost recycled aluminum to reduce material costs. The silicon content is controlled within the range of 1.75-2.25%. In practical applications, aluminum-silicon master alloys or pure silicon can be added, such as adding an aluminum-silicon intermediate with a silicon content of 20%, or directly adding high-purity silicon powder. This is mainly used to optimize the alloy's fluidity and reduce its brittleness. Furthermore, the molybdenum content is 0.1-0.4%, which can be understood as being added through an aluminum-molybdenum master alloy, such as using an Al5Mo master alloy dissolved in the melt, primarily to improve the microstructure. The titanium content is 0.05-0.10%, specifically achieved through an aluminum-titanium-boron master alloy, for example, using aluminum-titanium-boron wire with a titanium content of 5% for grain refinement, mainly for grain refinement. Furthermore, the manganese content is 0.05-0.2%, which in practical applications can be added using an aluminum-manganese master alloy, such as an aluminum-manganese master alloy with a manganese content of 10%, its role being to assist in performance improvement. The balance is composed of aluminum, serving as the matrix material to provide structural integrity. Thus, through the precise proportions of the above elements, this application solves the technical problem of achieving high plasticity and good casting performance while allowing for a higher iron content to reduce costs by using recycled aluminum. Specifically, this alloy design allows the iron content to be increased to 0.5-1.5%, significantly reducing raw material costs, while maintaining the necessary mechanical properties through the proportions of other elements. As a preferred embodiment, the combination of the above elements can directly obtain suitable casting properties under heat treatment-free conditions.

[0031] This low-cost, high-plasticity castable Al-Mg alloy achieves the technical goal of balancing material cost reduction and high-plasticity casting performance under high iron content conditions by precisely controlling the mass percentage range of each element. Specifically, magnesium is controlled within the range of 3.5% to 4.5%, ensuring sufficient strength and plasticity while avoiding the tendency for casting hot cracking caused by excessive magnesium content. Iron is set within the range of 0.5% to 1.5%, allowing the direct use of recycled aluminum with high iron content as raw material, significantly reducing raw material costs. Furthermore, through the synergistic effect of silicon, molybdenum, and manganese, the potentially harmful brittle phases formed by iron are effectively suppressed, preventing the iron-rich phase from agglomerating and coarsening into needle-like structures, instead forming fine, blocky AlFe(Mn,Mo)Si phases, thus maintaining good elongation performance under high iron content conditions. The silicon content is limited to between 1.75% and 2.25%, avoiding insufficient melt fluidity due to excessively low silicon content or brittleness due to excessively high silicon content. Molybdenum is added at 0.1% to 0.4%, combined with manganese at 0.05% to 0.2%, reducing the use of high-cost molybdenum through a manganese-molybdenum composite mechanism. Manganese can partially replace molybdenum, forming a more economical composite phase structure, thus further optimizing material costs while ensuring performance. Titanium is controlled within the range of 0.05% to 0.10%, effectively refining the microstructure as a grain refiner and enhancing the alloy's plasticity and toughness. The remaining aluminum acts as the matrix, providing a stable alloy framework and ensuring the integrity of the overall structure. Therefore, this technical solution effectively resolves the contradiction between high plasticity and good casting performance while allowing the use of high-iron-content recycled aluminum to reduce material costs, avoiding the negative impact of harmful phase formation on elongation, and thus achieving the goal of obtaining high-plasticity Al-Mg cast aluminum alloys under heat treatment-free conditions.

[0032] In one embodiment of the present invention, the mass ratio of Mg to Si in the alloy is Mg:Si = 1.8~2.1:1.

[0033] The Mg / Si mass ratio refers to the ratio of magnesium to silicon in the alloy. This ratio can be achieved by precisely controlling the amount of magnesium and silicon added to the raw materials. For example, it can be adjusted during the smelting process by changing the proportions of aluminum-magnesium master alloys and aluminum-silicon master alloys, or by directly supplementing with pure metallic elements. The purpose of setting this ratio is to ensure that Si fully participates in the composite reaction process with Fe, Mn, and Mo, avoiding abnormal increases in the size or uneven distribution of the AlFe(Mn,Mo)Si phase due to an imbalance in the ratio, thus providing a basis for optimizing the microstructure.

[0034] Specifically, the proposed solution systematically regulates the reaction kinetics between elements in the melt by strictly limiting the Mg:Si mass ratio to the range of 1.8 to 2.1:1. At this ratio, Si can fully participate in the complex reaction with Fe, Mn, and Mo, promoting the formation of fine and uniformly distributed AlFe(Mn,Mo)Si phases, rather than coarse and harmful phases. Simultaneously, this ratio ensures that the Mg content is relatively sufficient but not excessive, effectively avoiding the risk of hot cracking caused by high Mg content, while the Si content is maintained near the critical saturation point, both fully consuming impurity Fe elements to reduce their negative effects and preventing excess Si from causing the precipitation of brittle phases. Through this mechanism, the reaction process between elements is stably controlled, and the formation and distribution of the AlFe(Mn,Mo)Si phase are optimized, thereby directly improving the alloy's plasticity during the casting stage.

[0035] As a preferred embodiment, the specific implementation of the scheme of this application is as follows: In the alloy preparation process, after determining the initial element content through melt composition analysis, magnesium element is supplemented by aluminum-magnesium master alloy and silicon element is supplemented by aluminum-silicon master alloy, so that the mass ratio of the two is precisely controlled within the range of 1.8~2.1:1, for example, set to 2.0:1, to ensure the stability of the phase formation process.

[0036] Through the above scheme, this application effectively suppressed the abnormal size increase and uneven distribution of the AlFe(Mn,Mo)Si phase, significantly reduced the hot cracking tendency when using recycled aluminum with high Fe content, thereby improving the plasticity of the alloy and achieving synergistic optimization of low-cost raw materials and high elongation performance.

[0037] In one embodiment of the present invention, the mass ratio of Mo to Mn in the alloy is Mo:Mn = 1.5~2:1; by combining Mn and Mo, the amount of high-cost Mo element added is reduced, thereby further reducing the cost.

[0038] The mass ratio of Mo to Mn refers to the mass ratio of molybdenum to manganese in the alloy. This ratio can be achieved by adjusting the addition ratio of aluminum-manganese master alloy and aluminum-molybdenum master alloy. Specifically, this can be achieved by controlling the amount of master alloy added or by selecting master alloys with different compositions. The purpose of setting this ratio range is to ensure that Mn can effectively participate in the alloy phase transformation process and replace some of the function of Mo. The aim is to balance the need to reduce the amount of high-cost Mo with the maintenance of the alloy's plasticity, and to avoid waste of Mo or decrease in plasticity due to imbalance in the ratio.

[0039] Specifically, the solution proposed in this application precisely limits the mass ratio range of Mo and Mn, enabling Mn to form a synergistic effect with Mo during alloy solidification. Since Mn is an inherent low-cost component in recycled aluminum, it can partially replace the role of Mo in the AlFe(Mn,Mo)Si phase at a specific ratio, thereby reducing the absolute amount of Mo while maintaining phase structure stability. Given that the cost of Mo is significantly higher than that of Mn, this ratio control mechanism effectively reduces the need for adding high-cost Mo by optimizing the element ratio, while avoiding plasticity deterioration due to insufficient Mo content or cost increases caused by excessive addition, thus achieving substantial optimization of raw material costs.

[0040] As a specific implementation method, the scheme of this application is implemented as follows: During the smelting process, the amount of aluminum-manganese master alloy and aluminum-molybdenum master alloy added is calculated in advance to ensure that the mass ratio of Mo and Mn elements in the melt is strictly controlled within the range of 1.5 to 2:1; In actual operation, the aluminum-manganese master alloy can be added to the melt for preliminary melting first, and then the aluminum-molybdenum master alloy is added in batches and stirred thoroughly according to the real-time composition detection results to ensure uniform element distribution; This implementation method utilizes the inherent Mn element content in the recycled aluminum raw material and precisely controls the ratio through external supplementation, which not only makes full use of recycled aluminum resources, but also avoids the excessive use of Mo element.

[0041] In one embodiment of the present invention, the content of AlFe(Mn,Mo)Si phase in the alloy is 0.18-0.62%.

[0042] Among them, the AlFe(Mn,Mo)Si phase refers to the intermetallic compound phase formed by iron, manganese, molybdenum and silicon. It can be realized by adopting a dispersed fine particle morphology or a continuous network structure. The purpose is to optimize the microstructure by controlling the phase content and avoid performance dispersion caused by the fluctuation of phase content. The specific morphology of this phase can be controlled by adjusting the melting process parameters. Its essence is to balance the strengthening effect and plasticity loss.

[0043] Specifically, the solution of this application strictly limits the content of the AlFe(Mn,Mo)Si phase to the range of 0.18% to 0.62%, so that the phase forms a uniformly dispersed reinforcing network in the aluminum matrix. When the content is within this range, the phase particles effectively pin the dislocation movement to improve strength, while inhibiting the excessive aggregation of phase particles to avoid the formation of stress concentration points. Combined with the aforementioned limited elemental composition ratio, this content range and the synergistic effect of Mg, Si, Mo and Mn elements ensure the stable bonding between the phase and the matrix interface, thereby achieving simultaneous optimization of plasticity and strength under heat treatment-free conditions.

[0044] As a specific implementation method, the solution of this application is implemented as follows: During the smelting process, by precisely controlling the proportion of waste aluminum ingots and the order of addition of intermediate alloys, the AlFe(Mn,Mo)Si phase exists in the alloy matrix in the form of uniformly distributed fine particles. The phase particles exhibit a diffuse distribution characteristic at the microscale, effectively dispersing external stress and maintaining the continuity of the matrix.

[0045] In one embodiment of the present invention, the average size of the AlFe(Mn,Mo)Si phase is 4.7-19.4 μm.

[0046] The average size of the AlFe(Mn,Mo)Si phase refers to the average diameter of this intermetallic compound phase in the alloy microstructure. It can be achieved by adjusting the cooling rate and process parameters during the melting process. The purpose is to ensure that the phase particle size is appropriate, which can effectively hinder dislocation movement to provide a strengthening effect, while avoiding local stress concentration caused by excessive size.

[0047] Specifically, by precisely controlling the average size of the AlFe(Mn,Mo)Si phase within the range of 4.7-19.4 μm, the phase particles can be uniformly distributed in the matrix. When the lower limit is 4.7 μm, the particles have a sufficient size to effectively hinder dislocation movement and avoid insufficient strengthening effect. When the upper limit is 19.4 μm, the particles are not too large and cause stress concentration, reducing the risk of crack initiation, thereby ensuring high elongation while maintaining high tensile strength.

[0048] As a specific implementation method, the solution of this application is implemented as follows: the average size of the AlFe(Mn,Mo)Si phase is set to about 10μm.

[0049] A method for preparing a low-cost, high-plasticity cast Al-Mg alloy includes the following steps:

[0050] S1: Prepare the melt: Melt the waste aluminum ingot, blow air, remove slag, obtain a pure melt, and measure the composition; then heat the aluminum liquid to 750-780℃ and add aluminum manganese and aluminum silicon master alloys to supplement Mn and Si elements to the target content;

[0051] S2: Remelt the Al5Mo master alloy, hold it at 830-850℃ for 10-20 min, then cool it down to 730-750℃ and sonicate it for 10-15 min, and then add it to the melt obtained in the previous step.

[0052] S3: After the mixed melt cools down to 680-700℃, add pure magnesium and hold for 30 minutes; after heating to 710-720℃, add aluminum-titanium-boron master alloy, melt it completely and let it stand for later use.

[0053] S4: Refined;

[0054] S5: Field handling;

[0055] S6: Molding.

[0056] By systematically combining the order of element addition with process parameters, particularly through high-temperature melting followed by cooling and ultrasonic treatment before adding elements to the Al5Mo master alloy, the formation and size of the AlFe(Mn,Mo)Si phase are precisely controlled, achieving high plasticity and good casting performance under Fe content conditions of 0.5-1.5%. Specifically, this method optimizes the smelting process, allowing the use of recycled aluminum raw materials with higher iron content, breaking through the strict limitations on Fe content in traditional Al-Si alloys and significantly reducing material costs. Simultaneously, through precise control of the Mg:Si mass ratio of 1.8~2.1:1 and the Mn-Mo composite mechanism, the coarsening of the iron-rich phase into a needle-like structure is effectively suppressed, avoiding a decrease in elongation performance. Furthermore, the control of a specific temperature sequence reduces the risk of magnesium oxidation and burn-off, and external field treatment further refines the grains, ensuring a balance between high plasticity and strength in the alloy under heat-free conditions.

[0057] In one embodiment of the present invention, in step S2, an induction melting furnace is used to melt the Al5Mo master alloy; the melt obtained in step S2 is added to the melt in S1 through a ceramic conduit.

[0058] In practical applications, induction melting furnaces refer to melting equipment that uses the principle of electromagnetic induction to achieve non-contact heating. They can be implemented using medium-frequency induction melting furnaces, high-frequency induction melting furnaces, or industrial-frequency induction melting furnaces. Their purpose is to avoid local overheating and oxidation losses caused by direct contact between the flame or electrodes and the melt. Among them, ceramic conduits can be understood as melt transfer channels made of high-temperature resistant ceramic materials. They can be implemented using alumina ceramics, silicon nitride ceramics, or silicon carbide ceramics. Their purpose is to provide a chemically inert interface to effectively prevent metal contamination and the mixing of reactive impurities.

[0059] Specifically, the proposed solution utilizes an induction melting furnace for non-contact heating of the Al5Mo master alloy, achieving efficient thermal control and environmental isolation during the melting process, thus reducing the oxidation loss of Mo. Simultaneously, the chemical inertness and high-temperature stability of the ceramic conduit are used to transfer the melt into the Si melt, avoiding reactive contact between the metal conduit and the melt, thereby ensuring melt purity. This combined approach maintains the expected formation conditions of the AlFe(Mn,Mo)Si phase, providing a homogeneous melt foundation for subsequent ultrasonic and external field treatments, ultimately supporting the performance stability of the high-ductility Al-Mg alloy.

[0060] In one embodiment of the present invention, the refining step S4 includes further heating the melt to 740-760°C, mixing high-purity argon gas and refining agent and introducing them into the melt, and stirring with a graphite rotor for 5-10 minutes.

[0061] The process of further heating the melt to 740-760℃ involves controlling the melt within a suitable temperature range for impurity reaction. This aims to prevent insufficient refining agent activity due to excessively low temperatures or element burn-out due to excessively high temperatures, ensuring that impurities react fully without disrupting the alloy element balance under high Fe content conditions in recycled aluminum. Introducing a mixture of high-purity argon and refining agent into the melt involves simultaneously introducing inert gas and chemical treatment agents into the melt. This utilizes the inert environment of argon to prevent secondary oxidation of the melt, while the refining agent specifically decomposes oxides, enhancing the adsorption and removal capabilities of impurity phases such as Fe and Si through a synergistic effect. Stirring with a graphite rotor for 5-10 minutes involves using a rotating component made of a specific material to promote melt flow. This can be achieved using graphite stirrers with varying speed ranges. The purpose is to avoid additional contamination through the chemical stability of graphite. The stirring process ensures uniform melt flow, promoting full contact between the refining agent and impurities. Time control ensures thorough reaction while preventing gas entrainment and porosity.

[0062] Through the above-mentioned scheme, this application effectively improves the purity of the melt and significantly reduces the residual amount of oxides and harmful inclusions in high-Fe content recycled aluminum, thereby solving the problem of decreased alloy plasticity and strength stability caused by low impurity removal efficiency, and providing a reliable melt purification guarantee for obtaining high-plasticity cast Al-Mg alloys.

[0063] In one embodiment of the present invention, the field treatment in step S5 includes ultrasonic treatment of the aluminum alloy melt at 590-620°C; the ultrasonic treatment power is 200-500W, the output frequency is 19-21kHz, and the time is 5-30min.

[0064] Specifically, the ultrasonic treatment temperature refers to the temperature control range during ultrasonic treatment of aluminum alloy melt, which can be set between 590-620℃. This range is selected based on the thermodynamic properties of the melt, maintaining suitable melt fluidity to facilitate ultrasonic energy transfer while avoiding excessive temperature that could lead to Mg element burn-out. The ultrasonic treatment power refers to the intensity of ultrasonic energy applied to the melt, which can be controlled within the range of 200-500W. This provides sufficient energy to refine the AlFe(Mn,Mo)Si phase and reduce dendrite segregation, while preventing insufficient power from effectively activating the melt or excessive power from causing melt splashing. In practical applications, the ultrasonic treatment frequency refers to the vibration frequency of the ultrasonic waves, which can be set between 19-21kHz to promote the removal of bubbles and inclusions in the melt. The narrow frequency band ensures frequency stability. Finally, the ultrasonic treatment time refers to the duration of ultrasonic waves acting on the melt, which can be set between 5-30 minutes to ensure sufficient treatment to achieve grain refinement and defect reduction, while avoiding excessive time that could lead to reduced efficiency or excessive melt disturbance.

[0065] In one embodiment of the present invention, an aluminum alloy casting is obtained after forming in step S6; the tensile strength of the aluminum alloy casting is 243~263MPa and the elongation is 9.9~11.6%.

[0066] Among them, aluminum alloy castings refer to aluminum alloy parts formed by casting process, which can be achieved by gravity casting, die casting or low pressure casting, etc.; tensile strength refers to the ability of a material to resist fracture under tensile load, which can be tested by a universal testing machine; elongation refers to the degree of plastic deformation that occurs in a material during the tensile process, which can be calculated by measuring the elongation of the gauge length of the specimen.

[0067] Specifically, this application's scheme systematically verifies the comprehensive effectiveness of the preparation method under heat-free conditions by setting specific ranges for tensile strength and elongation. Precise control of elemental proportions ensures the formation of the AlFe(Mn,Mo)Si phase at optimized content and size. This phase effectively disperses and strengthens the matrix while suppressing localized weakening caused by impurity segregation. Simultaneously, the synergistic effect of ultrasonic treatment of the Al5Mo master alloy in step S2 and external ultrasonic treatment in step S5 refines the grain structure and suppresses coarsening of the AlFe(Mn,Mo)Si phase, thereby mitigating brittleness under high Fe content recycled aluminum conditions. The achievement of these performance indicators directly reflects the precise control of the microstructure by the preparation process, ensuring that the casting possesses both high strength and high elongation under heat-free conditions.

[0068] As a preferred embodiment, the solution of this application is implemented as follows: In step S6, the melt is poured into a preheated metal mold, and after cooling, it is demolded to obtain an aluminum alloy casting; subsequently, standard tensile specimens are cut from the casting for testing. The test results show that the tensile strength of the casting is stable at 243-263 MPa, and the elongation is 9.9-11.6%, confirming that the material has excellent comprehensive mechanical properties in the heat-free state.

[0069] Through the above scheme, this application effectively verifies the stable control capability of the preparation method on the quality of castings, ensures that the material has both high strength and high plasticity under heat treatment-free conditions, solves the performance fluctuation problem caused by high Fe content recycled aluminum, and avoids the casting hot cracking tendency of high Mg alloys.

[0070] Example 1:

[0071] The chemical composition (mass percentage) of a low-cost, high-plasticity cast Al-Mg alloy in this embodiment is as follows: Mg 4.5%, Fe 1.5%, Si 2.5%, Mo 0.3%, Ti 0.10%, Mn 0.2%, with the balance being Al.

[0072] This embodiment relates to a low-cost, high-plasticity casting method for preparing Al-Mg alloys:

[0073] S1: Melt preparation: Melt waste aluminum ingots, blow air, remove slag, obtain pure melt, and measure composition; then heat the aluminum liquid to 770℃ and add aluminum-manganese and aluminum-silicon master alloys to supplement Mn and Si elements to the target content;

[0074] S2: Melt the Al5Mo master alloy in an induction melting furnace, hold at 830℃ for 20 minutes, cool down to 730℃ and sonicate for 15 minutes, then add it to the S1 melt through a ceramic conduit.

[0075] S3: After the mixed melt cools down to 700℃, add pure magnesium and hold for 30 minutes; after heating to 720℃, add aluminum-titanium-boron master alloy, melt it completely and let it stand for later use.

[0076] S4: Refining, the melt is heated to 740℃, high-purity argon and refining agent are mixed and introduced into the melt, and stirred by a graphite rotor for 5 minutes;

[0077] S5: External field treatment, ultrasonic treatment of the aluminum alloy melt at 620℃, ultrasonic treatment power 200W, output frequency 21kHz, time 30min.

[0078] S6: Gravity casting, followed by rapid heating to 720℃ and pouring into a copper mold to obtain aluminum alloy material.

[0079] The content, average size, and mechanical properties of the iron-rich phase in the aluminum alloy obtained in Example 1 are shown in Table 1.

[0080] like Figure 1 The image shown is a photograph of the as-cast metallographic structure of the alloy prepared in Example 1. It can be seen that the as-cast structure is uniformly distributed in the alloy, and no slender needle-like Fe-rich phases were observed, indicating that the Fe-rich phases are transformed into AlFe(Mn,Mo)Si, thus ensuring that the alloy has good elongation.

[0081] Example 2:

[0082] The chemical composition of a low-cost, high-plasticity cast Al-Mg alloy in this embodiment is as follows: Mg 3.5%, Fe 0.5%, Si 1.75%, Mo 0.1%, Ti 0.05%, Mn 0.05%, with the balance being Al.

[0083] This embodiment relates to a low-cost, high-plasticity casting method for preparing Al-Mg alloys:

[0084] S1: Prepare the melt: Melt the waste aluminum ingot, blow air, remove slag, obtain a pure melt, and measure the composition; then heat the aluminum liquid to 750℃ and add aluminum manganese and aluminum silicon master alloys to supplement Mn and Si elements to the target content;

[0085] S2: Melt the Al5Mo master alloy in an induction melting furnace, hold at 850℃ for 15 minutes, cool down to 740℃ and sonicate for 12 minutes, then add it to the S1 melt through a ceramic conduit.

[0086] S3: After the mixed melt cools down to 680℃, add pure magnesium and hold for 30 minutes; after heating to 720℃, add aluminum-titanium-boron master alloy, melt it completely and let it stand for later use.

[0087] S4: Refining, the melt is heated to 750°C, high-purity argon and refining agent are mixed and introduced into the melt, and stirred by a graphite rotor for 10 minutes;

[0088] S5: External field treatment, ultrasonic treatment of the aluminum alloy melt at 590℃, ultrasonic treatment power 350W, output frequency 20kHz, time 20min.

[0089] S6: Gravity casting, followed by rapid heating to 710℃ and pouring into a copper mold to obtain aluminum alloy material.

[0090] The content, average size, and mechanical properties of the iron-rich phase in the aluminum alloy obtained in Example 2 are shown in Table 1.

[0091] Example 3:

[0092] The chemical composition (mass percentage) of a low-cost, high-plasticity cast Al-Mg alloy in this embodiment is as follows: Mg 4.0%, Fe 1.0%, Si 1.9%, Mo 0.18%, Ti 0.08%, Mn 0.1%, with the balance being Al.

[0093] This embodiment relates to a low-cost, high-plasticity casting method for preparing Al-Mg alloys:

[0094] S1: Melt preparation: Melt waste aluminum ingots, blow air, remove slag, obtain pure melt, and measure composition; then heat the aluminum liquid to 780℃ and add aluminum-manganese and aluminum-silicon intermediate alloys to supplement Mn and Si elements to the target content;

[0095] S2: Melt the Al5Mo master alloy in an induction melting furnace, hold at 840℃ for 10 min, cool to 750℃ and sonicate for 10 min, then add it to the S1 melt through a ceramic conduit.

[0096] S3: After the mixed melt cools down to 690℃, add pure magnesium and hold for 30 minutes; after heating to 720℃, add aluminum-titanium-boron master alloy, melt it completely and let it stand for later use.

[0097] S4: Refining, the melt is heated to 760°C, high-purity argon and refining agent are mixed and introduced into the melt, and stirred by a graphite rotor for 7 minutes;

[0098] S5: External field treatment, ultrasonic treatment of the aluminum alloy melt at 600℃, ultrasonic treatment power 500W, output frequency 19kHz, time 5min.

[0099] S6: Gravity casting, followed by rapid heating to 730℃ and pouring into a copper mold to obtain aluminum alloy material.

[0100] The content, average size, and mechanical properties of the iron-rich phase in the aluminum alloy obtained in Example 3 are shown in Table 1.

[0101] like Figure 2 The image shown is a microstructure photograph of the casting of the alloy prepared in Example 3. It can be seen that the microstructure mainly consists of black Mg2Si phase and blocky and irregularly shaped eutectic phases; no acicular second phase was observed. This indicates that the morphology of the Fe-rich phase in the microstructure is significantly improved.

[0102] like Figure 3 The image shows the energy dispersive spectroscopy (EDS) results of the alloy prepared in Example 3; through... Figure 3 Further analysis can confirm the elemental distribution in the alloy and the transformation of the Fe-rich phase from acicular to AlFe(Mn,Mo)Si phase, thereby improving the alloy's plasticity.

[0103] Figure 4These are the tensile curves of the alloys prepared in Examples 1 and 2. It can be confirmed that the tested alloys exhibit excellent plasticity at both the upper and lower limits of the alloy composition.

[0104] Comparative Example 1:

[0105] The chemical composition (mass percentage) of the Al-Mg alloy material cast in this comparative example is: Mg 4.0%, Fe 1.0%, Si 1.9%, Ti 0.08%, Mn 0.1%, with the balance being Al.

[0106] The preparation method of the Al-Mg alloy involved in this comparative example is as follows:

[0107] S1: Melt preparation: Melt waste aluminum ingots, blow air, remove slag, obtain pure melt, and measure composition; then heat the aluminum liquid to 780℃ and add aluminum-manganese and aluminum-silicon intermediate alloys to supplement Mn and Si elements to the target content;

[0108] S2: Melt the Al5Mo master alloy in an induction melting furnace, hold at 840℃ for 10 min, cool to 750℃ and sonicate for 10 min, then add it to the S1 melt through a ceramic conduit.

[0109] S3: After the mixed melt cools down to 690℃, add pure magnesium and hold for 30 minutes; after heating to 720℃, add aluminum-titanium-boron master alloy, melt it completely and let it stand.

[0110] S4: Refining, the melt is heated to 760°C, high-purity argon and refining agent are mixed and introduced into the melt, and stirred by a graphite rotor for 7 minutes;

[0111] S5: Gravity casting, followed by rapid heating to 730℃ and pouring into a copper mold to obtain aluminum alloy material.

[0112] The mechanical properties of the aluminum alloy obtained in Comparative Example 1 are shown in Table 1. Comparative Example 1 does not contain Mo and was not subjected to any external field treatment. Compared to Example 3, its elongation is significantly reduced. This indicates that, on the one hand, the Fe phase disrupts the matrix, and on the other hand, the coarse dendrites reduce the elongation.

[0113] Table 1. Room temperature tensile properties of the alloys obtained in Examples 1-3 and Comparative Example 1 of the present invention.

[0114] alloy Content of AlFe(Mn,Mo)Si phase Average size (μm) of AlFe(Mn,Mo)Si phase Tensile strength (MPa) Yield strength (MPa) Elongation (%) Example 1 0.62 19.4 263 116 9.9 Example 2 0.18 4.7 243 103 11.6 Example 3 0.33 6.4 246 108 10.3 Comparative Example 1 / / 226 92 4.8

[0115] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent modifications made based on the content of the present invention's specification and drawings, or direct or indirect applications in related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A low-cost, high-plasticity cast Al-Mg alloy, characterized in that, The following elements are included by mass percentage: Mg 3.5-4.5%, Fe 0.5-1.5%, Si 1.75-2.25%, Mo 0.1-0.4%, Ti 0.05-0.10%, Mn 0.05-0.2%, with the balance being Al.

2. The low-cost, high-plasticity cast Al-Mg alloy according to claim 1, characterized in that: The mass ratio of Mg to Si in the alloy is Mg:Si = 1.8~2.1:

1.

3. The low-cost, high-plasticity cast Al-Mg alloy according to claim 1, characterized in that: The mass ratio of Mo to Mn in the alloy is Mo:Mn = 1.5~2:

1.

4. The low-cost, high-plasticity cast Al-Mg alloy according to claim 1, characterized in that: The content of AlFe(Mn,Mo)Si phase in the alloy is 0.18-0.62%.

5. A low-cost, high-plasticity cast Al-Mg alloy according to claim 4, characterized in that: The average size of the AlFe(Mn,Mo)Si phase is 4.7-19.4 μm.

6. A method for preparing a low-cost, high-plasticity cast Al-Mg alloy as described in any one of claims 1-5, characterized in that, Includes the following steps: S1: Prepare the melt: Melt the waste aluminum ingot, blow air, remove slag, obtain a pure melt, and measure the composition; then heat the aluminum liquid to 750-780℃ and add aluminum manganese and aluminum silicon master alloys to supplement Mn and Si elements to the target content; S2: Remelt the Al5Mo master alloy, hold it at 830-850℃ for 10-20 min, then cool it down to 730-750℃ and sonicate it for 10-15 min, and then add it to the S1 melt; S3: After the mixed melt cools down to 680-700℃, add pure magnesium and hold for 30 minutes; after heating to 710-720℃, add aluminum-titanium-boron master alloy, melt it completely and let it stand for later use. S4: Refined; S5: Field handling; S6: Molding.

7. The method for preparing a low-cost, high-plasticity cast Al-Mg alloy according to claim 6, characterized in that: In step S2, the Al5Mo master alloy is melted in an induction melting furnace; the melt obtained in step S2 is added to the melt in S1 through a ceramic conduit.

8. The method for preparing a low-cost, high-plasticity cast Al-Mg alloy according to claim 6, characterized in that: The refining step S4 includes further heating the melt to 740-760°C, mixing high-purity argon gas and refining agent and introducing them into the melt, and stirring with a graphite rotor for 5-10 minutes.

9. The method for preparing a low-cost, high-plasticity cast Al-Mg alloy according to claim 6, characterized in that: The field treatment in step S5 includes ultrasonic treatment of the aluminum alloy melt at 590-620℃; the ultrasonic treatment power is 200-500W, the output frequency is 19-21kHz, and the time is 5-30min.

10. The method for preparing a low-cost, high-plasticity cast Al-Mg alloy according to claim 6, characterized in that: After forming in step S6, an aluminum alloy casting is obtained; the tensile strength of the aluminum alloy casting is 243~263MPa, and the elongation is 9.9~11.6%.

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