Screening method and preparation method of Al-Si-Mn-Mg quaternary intermediate alloy for high-melting-point Mn element

Abstract

The invention discloses a screening method for an Al-Si-Mn-Mg quaternary intermediate alloy aiming at a high-melting-point Mn element. The screening method comprises the following steps: 1, setting phase diagram calculation and setting parameters of solidification simulation; 2, calculating a result and a solidification simulation result based on the phase diagram; and 3, intermediate alloy components meeting the screening requirements are confirmed. The screening conditions need to meet three screening conditions at the same time, the condition 1 is that the Si element, the Mn element and the Mg element meet the alloy components Al-(9-11) d Si-(0.5-0.8) d Mn-(0.2-0.5) d Mg, and the parameter d is larger than or equal to 4; the second condition is that the phase content of the intermediate alloy meets the conditions that f (Si) is larger than or equal to 30 mol%, and f (Al8Mn5) is larger than or equal to 5 mol%; and the third condition is that the semisolid temperature interval delta T of the intermediate alloy is larger than or equal to 50 DEG C, and the semisolid interval in the solidification process of the intermediate alloy needs to meet the condition that the solid phase ratio f (s) is equal to 0.2-0.8. The invention further discloses a preparation method of the Al-Si-Mn-Mg quaternary intermediate alloy aiming at the high-melting-point Mn element and a preparation method of the cast Al-Si-Mn-Mg alloy aiming at the high-melting-point Mn element.

Description

Technical Field

[0001] The present invention relates to the field of aluminum alloy material preparation, and in particular to a screening method and a preparation method of an Al-Si-Mn-Mg quaternary master alloy targeting a high-melting-point Mn element. Background Art

[0002] Cast Al-Si-Mn-Mg alloys, or AlSi10MnMg alloys, possess high strength and hardness, capable of withstanding the high temperatures and high pressures encountered during engine operation. They are commonly used in the manufacture of engine components such as cylinder blocks, cylinder heads, and pistons. AlSi10MnMg alloys also possess excellent thermal conductivity and electromagnetic shielding properties, effectively dissipating heat and preventing electromagnetic interference. They are commonly used in the manufacture of electronic device casings such as laptops, tablets, and mobile phones. However, the complex production process and raw material selection of multi-element cast aluminum alloys directly impact production costs, efficiency, and the performance of the cast aluminum alloys. Traditionally, the raw materials used in the casting of AlSi10MnMg alloys are typically industrial-pure Al, pure Si, an Al-Mn master alloy, and pure Mg. These raw materials are melted and uniformly mixed in a resistance furnace or induction melting furnace. This method offers a simple process flow and a short production cycle. However, for complex quaternary alloys like AlSi10MnMg alloys, the melting process is prone to Mn segregation and Mg volatilization, increasing the alloy's production cost.

[0003] A common solution currently involves using master alloys instead of pure elements to prepare Al-Si alloys. Common master alloys include AlSi20 and AlMg50. The principle is that master alloys have a lower melting point than pure metals, effectively shortening the alloy's smelting time and promoting the uniform distribution of alloying elements in the cast Al-Si alloy. For example, in existing document 1 (Liu Shuji, CN118910444A, "An Improved Method for Melting and Preparing Aluminum-Silicon Alloy Castings," 2024-09-11), a near- / hypereutectic aluminum-silicon alloy Al-xSi (10≤x≤22) ingot is used as the aluminum-silicon master alloy. Pure aluminum is added in a specific ratio (1:a) and heated to melt. Pure Mg, Al-Ti-B, Al-Sr, and other elements are then added to adjust the aluminum liquid composition and transform the melt. Mg, a susceptible element to burning, is added as pure Mg blocks (≥99.5%) and placed in a launder between the melting furnace and the standing furnace, ultimately producing the desired Al-Si alloy melt. Although this technical solution proposes a method for preparing cast Al-Si alloy using an intermediate alloy, the elements in the intermediate alloy are single and the content is low, which does not effectively simplify the alloy preparation process. In addition, the direct contact between pure Mg and high-temperature melt will cause oxidation and burning of Mg.

[0004] Design and preparation of multi-element master alloy can effectively simplify the preparation process of cast Al-Si alloy, but the introduction of multiple elements in the master alloy will increase the difficulty of element content control in the master alloy preparation process, and chemical reaction or intermetallic compound may occur between different alloy elements. For example, in the existing literature 2 (Chen Weiping, CN107794419A, A multi-element master alloy for aluminum alloy and its preparation method, 2018.03.13), a multi-element master alloy containing Mg 2-6%, Mn 0.2-0.8%, Sc 0.08-0.8%, and Zr 0.08-0.4% is prepared by molten salt aluminothermic reduction method. Although this technical solution increases the element composition of the master alloy, the low element content directly leads to a high dosage of the master alloy in subsequent use, which cannot achieve the purpose of reducing production difficulty, and this technical solution is also not suitable for the production of cast Al-Si alloy. At the same time, such molten salt aluminothermic reduction method also has the technical problems of difficulty in separating the reaction products from the alloy melt during preparation and generation of harmful gases.

[0005] According to the existing literature 1 and the existing literature 2, the existing technology cannot effectively improve the element content of the master alloy. The reason is that increasing the element content of the master alloy will directly lead to an increase in the melting point of the master alloy, thereby re-creating the technical problem represented by element segregation when not using the master alloy, ultimately affecting the composition accuracy and performance consistency of the cast Al alloy. Therefore, it is necessary to improve the master alloy preparation process to increase the element content of the master alloy while obtaining a uniform structure.

[0006] For example, in the existing literature 3 (Hao Yonggang, CN119194144A, A large deformation assisted high homogenization aluminum silicon master alloy preparation method, 2024-12-17), AlSi10, AlSi30 and AlSi60 master alloys are prepared by adopting the method of powder metallurgy combined with ultra-low temperature extrusion large plastic deformation. This technical solution effectively increases the element content in the master alloy and obtains a uniform master alloy structure. However, compared with traditional melting methods, the powder metallurgy production process includes powder preparation, uniform mixing, forming, sintering and post-processing, etc. Each step requires a certain time and process control, especially in the powder pressing and sintering link, the production cycle is relatively long. Compared with melting, the production efficiency is low due to the limitation of the size of the pressing mold and other conditions, which is also not conducive to large-scale industrial production.

[0007] In addition, existing document 4 (Lu Shuxing, CN116100013A, A Vacuum Induction Melting and Casting Furnace and Method for Preparing AlMn Master Alloy, 2023-5-12) uses a vacuum induction casting furnace to prepare AlMn master alloys with a Mn content of 65.4-90.2%. However, this technical solution significantly increases the Mn content in the master alloy. The high Mn content directly leads to a significant increase in the melting point of the master alloy, which in turn has two unfavorable consequences: 1. The use of a vacuum induction casting furnace during the preparation of the master alloy increases the requirements for production equipment; 2. The problem of element segregation occurs during the subsequent preparation of the AlSi10MnMg alloy.

[0008] According to existing documents 3 and 4, the current solution for increasing the Mn content in the master alloy directly leads to changes in the alloy preparation process or production equipment, which in turn makes the master alloy production method unable to achieve mass production and industrial application.

[0009] The inventors of the present invention have previously discovered that by screening and preparing an Al-Si-Mg ternary master alloy through phase diagram calculation and simultaneously introducing Mg via a semi-solid process, the problem of oxidation and burning during the smelting process can be resolved. This allows for the rapid preparation of cast A356 alloys based on the Al-42Si-1.8Mg master alloy, ultimately simplifying the preparation process for cast Al-Si alloys and improving the uniformity and performance stability of the alloy. However, subsequent research has revealed that when this technical solution is directly applied to the Al-Si-Mn-Mg quaternary system, the introduction of Mn directly increases the alloy's melting point, alters the semi-solid state, and generates new phases, due to the melting point of Mn (1246°C), which is significantly higher than the boiling point of Mg (1090°C). The direct consequence of these substantial differences is that when the smelting temperature is lowered, Mn exhibits a delayed dissolution, resulting in the presence of undissolved particles. Conversely, when the smelting temperature is increased, Mg experiences severe volatilization and burning at high temperatures, causing the Mg content in the alloy to deviate from the target composition range. Summary of the Invention

[0010] The present invention aims to provide a method for screening and preparing an Al-Si-Mn-Mg quaternary master alloy containing the high-melting-point element Mn. The method screens the composition of the Al-Si-Mn-Mg alloy by calculating a phase diagram. Furthermore, the method reduces alloy element losses during the smelting process by adjusting the preparation process. The basic principles underlying the above-mentioned invention are as follows:

[0011] 1. Introducing Mn element in Al-Si-Mg alloy, forming Al8Mn5 phase in as-cast alloy, and based on the characteristics that the melting point of intermediate alloy changes with the increase of Si content and Mn content, and the phase transformation process and phase content change during solidification, the melting point and phase composition of Al-Si-Mn-Mg alloy are predicted by phase diagram calculation, and the composition range of intermediate alloy is determined;

[0012] 2. When the solid phase rate in the melt is in the range of 20-80%, the intermediate alloy is in semi-solid state, and the viscosity of the melt in semi-solid state is large, so that the raw material can be buried at a lower temperature, and the technical effect of isolating oxygen to reduce the volatilization loss of Mg element is obtained; based on the above principle, the semi-solid interval of intermediate alloy with different composition is obtained by solidification simulation, and the subsequent control of melting temperature and semi-solid temperature finally realizes the avoidance of Mg element volatilization caused by too high temperature and Mn element segregation caused by too low temperature.

[0013] To achieve the above-mentioned purposes, the application adopts the following solutions:

[0014] A screening method for Al-Si-Mn-Mg quaternary intermediate alloy of high melting point Mn element, comprising the following steps:

[0015] Step 1, setting of phase diagram calculation and parameter setting of solidification simulation, phase diagram calculation includes selection of phase diagram type and setting of alloy element type, solidification simulation includes selection of calculation model, setting of alloy element type and composition;

[0016] Step 2, based on the results of phase diagram calculation and solidification simulation, setting the intermediate alloy composition screening conditions, the screening conditions include composition range and temperature range, and the screening conditions need to meet 3 screening conditions at the same time;

[0017] Step 3, confirming the intermediate alloy composition meeting the screening requirements, in the thermodynamic phase diagram of Al-Si-Mn-Mg alloy, selecting the liquidus projection plane, and confirming the phase composition area meeting the screening requirements in step 2;

[0018] In step 1, the selection of phase diagram type is that the calculated phase diagram is the liquidus projection plane and liquidus temperature contour of Al-Si-Mn ternary system, Pandat software is adopted, and PhaseProjection in PanPhaseDiagram phase diagram module is selected for calculation;

[0019] The calculation step of the liquidus temperature contour is 100℃;

[0020] The setting of alloy element type in the phase diagram calculation is that the alloy element type includes Al element, Si element, Mn element and Mg element;

[0021] The calculation model of the solidification simulation is selected by using Pandat software and selecting the Scheil-Gulliver model in the PanPhaseDiagram phase diagram module for solidification simulation;

[0022] The composition setting in the solidification simulation is Si: 10d, Mn: 0.6d, Mg: 0.35d, and the balance is Al, where d ≥ 4;

[0023] In step 2, the screening conditions for the intermediate alloy composition simultaneously meet the following three screening conditions:

[0024] The intermediate alloy composition screening condition 1 is that the Si element, the Mn element and the Mg element satisfy the alloy composition Al-(9-11)dSi-(0.5-0.8)dMn-(0.2-0.5)dMg, wherein the parameter d≥4,

[0025] The second screening condition for the composition of the intermediate alloy is that the phase content of the intermediate alloy satisfies the following conditions: f(Si)≥30mol%, f(Al8Mn5)≥5mol%,

[0026] The intermediate alloy composition screening condition 3 is that the semi-solid temperature range of the intermediate alloy is ΔT ≥ 100°C;

[0027] In the screening condition 3, the semi-solid period of the solidification process of the master alloy must meet the solid phase ratio: f(s)=0.2-0.8.

[0028] A preparation method for an Al-Si-Mn-Mg quaternary master alloy targeting a high-melting-point Mn element comprises the following steps: first, raw materials are prepared in a satisfactory mass ratio, pure Al, pure Si, an Al-20Mn master alloy, and an Al-20Si master alloy are placed in a crucible, then, the crucible and the master alloy are preheated at a preheating temperature to remove moisture in the crucible and the alloy, then, the alloys are heated at a smelting temperature, and after the pure Al, pure Si, the Al-20Mn master alloy, and the Al-20Si master alloy are melted, scum and oxide scale on the surface are removed to obtain an aluminum alloy melt, then, the Al-50Mg master alloy is wrapped with aluminum foil and preheated at the preheating temperature, and the temperature of the aluminum alloy melt is lowered to a semi-solid temperature range, then, the preheated Al-50Mg master alloy is pressed into the semi-solid aluminum alloy melt, and finally, the alloy is cast at a casting temperature and solidified and cooled to obtain an Al-Si-Mn-Mg quaternary master alloy produced by a semi-solid process;

[0029] The preheating temperature of the crucible and the master alloy is 200-400°C;

[0030] The melting temperature of the master alloy is 900-1200°C;

[0031] The casting temperature of the master alloy is 800-1100°C.

[0032] A preparation method for casting an Al-Si-Mn-Mg alloy based on an Al-Si-Mn-Mg quaternary master alloy comprises the following steps: first, weighing pure Al and a master alloy to meet a mass ratio condition, placing the pure Al in a crucible, then preheating the crucible at a preheating temperature to remove moisture in the crucible and the alloy, then heating at a melting temperature, and after the pure Al is melted, removing surface slag and oxide scale, then wrapping the master alloy with aluminum foil and preheating it at a preheating temperature, pressing the preheated master alloy into the pure Al melt, fully stirring it for a stirring time, then standing it at the melting temperature for 1 hour, fully stirring it every 20 minutes during the standing process, then adjusting the casting temperature, and casting the melt into a permanent mold preheated at the preheating temperature, and solidifying and cooling it to obtain a cast Al-Si-Mn-Mg alloy;

[0033] The preheating temperature of the crucible and raw materials is 200-400°C;

[0034] The melting temperature of the cast Al-Si-Mn-Mg alloy is 750-850°C;

[0035] The casting temperature of the Al-Si-Mn-Mg alloy is 700-750°C.

[0036] The technical effects of the present invention have been tested and the specific contents are as follows:

[0037] SEM examination revealed that the Al-Si-Mn-Mg quaternary master alloy contained α-Al, primary Si, and eutectic Si phases. The Al8Mn5 phase and Mg2Si phase were also present. Statistical analysis of the area ratios of the primary and eutectic Si phases revealed that the measured phase composition of the Al-50Si-3.0Mn-1.5Mg alloy was 30.3 mol% primary Si and 15.2 mol% eutectic Si. The measured phase composition of the Al-60Si-3.6Mn-1.8Mg alloy was 41.2 mol% primary Si and 11.5 mol% eutectic Si. The measured total content of primary Si and eutectic Si was generally consistent with the calculated total content. The SEM and statistical results demonstrate that the master alloy screening method can accurately predict the phase composition and content of the primary phases in master alloys.

[0038] SEM-EDS analysis revealed uniform distribution of Mg and Si in the Al-Si-Mg quaternary master alloy, with no elemental segregation. The Si, Mn, and Mg contents of the Al-50Si-3.0Mn-1.5Mg alloy were 49.6±3.5wt.%, 2.8±0.8wt.%, and 1.7±0.1wt.%, respectively. The Si, Mn, and Mg contents of the Al-60Si-3.6Mn-1.8Mg alloy were 61.6±5.9wt.%, 3.5±0.1wt.%, and 2.1±0.7wt.%, respectively. SEM-EDS analysis confirmed that the Mg content in the master alloys was consistent with the actual addition amount. The semi-solid-state method eliminated the issue of burnout of the low-melting-point Mg during the preparation process, resulting in the accurate preparation of a multi-component master alloy containing both high-melting-point Mn and low-melting-point Mg.

[0039] Direct reading spectroscopy (DES) analysis revealed that the cast Al-Si-Mn-Mg alloy prepared using the Al-50Si-3.0Mn-1.5Mg quaternary master alloy as raw material contained Si, Mn, and Mg elements within the target composition range. The composition remained stable with increasing holding time, and there was no significant burnout of Mg during the holding process. DES test results demonstrate that the cast AlSi10MnMg alloy prepared using the Al-Si-Mn-Mg quaternary master alloy can achieve a uniform alloy structure and accurate alloy composition in a short period of time.

[0040] The present invention has the following beneficial effects:

[0041] 1. The high-melting-point Mn element was introduced by the smelting method, and the low-melting-point Mg element was introduced by the semi-solid method. Through solidification simulation and phase diagram calculation, the temperature during the smelting process was selected and adjusted to avoid the segregation of the Mn element and the volatilization and burning loss of the Mg element, thereby improving the microstructure consistency and composition accuracy of the cast AlSi10MnMg alloy;

[0042] 2. Through composition design and process design, the Al-Si-Mn-Mg quaternary master alloy was screened and prepared, and a uniform master alloy structure was obtained, which simplified the preparation process of the cast AlSi10MnMg alloy and reduced energy consumption in the production process. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 It is the liquid phase projection surface diagram of Al-Si-Mn ternary system;

[0044] Figure 2 The solidification paths and semi-solid interval diagrams of Example 1, Example 2, Comparative Example 1 and Comparative Example 2;

[0045] Figure 3The SEM-BSE images of Example 1 and Example 2;

[0046] Figure 4 The SEM-EDS composition distribution diagrams of Example 1 and Example 2 are shown. Specific implementation methods

[0047] Example 1

[0048] A method for screening Al-Si-Mn-Mg quaternary master alloys containing a high-melting-point Mn element, comprising the following steps:

[0049] Step 1: Set up phase diagram calculation and solidification simulation parameters. Phase diagram calculation includes selecting the phase diagram type and setting the alloying element types. Solidification simulation includes selecting the calculation model and setting the alloying element types and compositions.

[0050] The phase diagram type is selected as follows: the calculated phase diagram is the liquid phase projection surface and liquidus temperature contour line of the ternary system, and the calculation is performed using Pandat software and Phase Projection in the PanPhaseDiagram phase diagram module;

[0051] The calculation step size of the liquidus temperature contour line is 100°C;

[0052] The alloy element types calculated in the phase diagram are set as Al, Si and Mn;

[0053] The calculation model of the solidification simulation is selected by using Pandat software and selecting the Scheil-Gulliver model in the PanPhaseDiagram phase diagram module for solidification simulation;

[0054] The composition setting in the solidification simulation is Si: 10d, Mn: 0.6d, Mg: 0.35d, and the balance is Al, where d ≥ 4;

[0055] Step 2: Based on the phase diagram calculation results and the solidification simulation results, set the intermediate alloy composition screening conditions. The screening conditions include the composition range and the temperature range. The screening conditions must meet the three screening conditions at the same time, specifically,

[0056] The composition screening condition 1 of the master alloy is to meet the alloy composition Si: (9-11) d wt.%, Mn: (0.5-0.8) d wt.%, Mg: (0.2-0.5) d wt.%, wherein the parameter d≥4, and the balance is Al;

[0057] The second screening condition for the composition of the intermediate alloy is that the phase content of the intermediate alloy satisfies the following conditions: f(Si)≥30mol%, f(Al8Mn5)≥5mol%.

[0058] The intermediate alloy composition screening condition 3 is that the semi-solid temperature range of the intermediate alloy is ΔT ≥ 100°C;

[0059] Step 3: Confirm the composition of the intermediate alloy that meets the screening requirements. In the Al-Si-Mn alloy thermodynamic phase diagram, select the liquid phase projection surface and the phase composition area that meets the screening requirements in step 2. The phase composition area that meets the screening requirements is named area 1. The specific area is as follows: Figure 1 shown.

[0060] To demonstrate the effectiveness of the master alloy screening method, an Al-50Si-3.0Mn-1.5Mg master alloy was prepared within Region 1. Solidification simulations were performed to calculate the content of each phase in the alloy's solidified structure. In Example 1, the calculated content of the Al8Mn5 phase was 10.8 mol%. The molar fractions of the primary Si phase and eutectic Si phase obtained using the screening method are shown in Table 1.

[0061] Table 1 Thermodynamic phase diagram theoretical calculation of the Si phase of Al-Si-Mn-Mg master alloy and its actual measured value

[0062]

[0063]

[0064] A method for preparing an Al-Si-Mn-Mg quaternary master alloy containing a high-melting-point Mn element, comprising the following steps:

[0065] First, the raw materials are prepared to meet the conditions of Al-50Si-3.0Mn-1.5Mg alloy in a mass ratio. Specifically, the addition amount of pure Al is 320g, the addition amount of pure Si is 500g, the addition amount of Al-20Mn master alloy is 150g and the addition amount of Al-50Mg master alloy is 30g. Pure Al, pure Si, Al-20Si master alloy and Al-20Mn master alloy are placed in a crucible. Then, the pit furnace is preheated at a preheating temperature of 400℃ to remove water vapor in the crucible and the alloy. After that, the melting temperature is 1200℃ and the pure Al is heated to 1500℃. 1. After pure Si, Al-20Si master alloy, and Al-20Mn master alloy are melted, surface slag and oxide scale are removed to obtain an aluminum alloy melt. Subsequently, the Al-50Mg master alloy is wrapped with aluminum foil and preheated at 150°C. The temperature of the aluminum alloy melt is lowered to a semi-solid temperature range, specifically 750°C. The preheated Al-50Mg master alloy is pressed into the semi-solid aluminum alloy melt. Finally, the alloy is cast at a casting temperature of 1100°C and solidified and cooled to obtain an Al-Si-Mn-Mg quaternary master alloy prepared by a semi-solid process, referred to as a master alloy.

[0066] The casting mold is made of cast iron, and the casting time is less than 30 seconds;

[0067] The semi-solid interval is as follows Figure 2 As shown, the solid phase in the semi-solid melt accounts for 20-80 mol.%;

[0068] In order to prove the phase composition of the master alloy, the test results are as follows: Figure 3 As shown, by statistically analyzing the area ratios of the primary Si phase and the eutectic Si phase, and calculating the amount of matter based on the area ratios of the phases, the statistical results are shown in Table 1.

[0069] α-Al phase is the base phase;

[0070] The primary Si phase is a supersaturated Si crystal in the melt, which has the characteristic of preferential nucleation and growth during the solidification process, that is, it is the first precipitated phase; at the same time, the primary Si phase often presents a relatively coarse block or plate-like structure in the aluminum alloy matrix. Therefore, in the target alloy composition, the primary Si phase plays a role in significantly improving the hardness of the alloy and its wear resistance. At the same time, the dispersed primary Si phase increases the contact area between Si and the melt during the preparation of the cast Al-Si alloy, thereby accelerating the diffusion of Si in the melt and promoting the homogenization of the cast Al-Si alloy.

[0071] The eutectic Si phase is the Si phase formed during the eutectic reaction of aluminum alloys. It has the characteristic of crystallizing and precipitating at the same time as the α-Al phase at a specific temperature and is a key component of the eutectic structure. The eutectic Si phase generally presents a fine needle-like, fibrous or lamellar structure in the aluminum alloy matrix. Therefore, in the design of cast Al-Si alloys, the eutectic Si phase plays a role in refining the alloy structure and improving the comprehensive performance of the alloy's strength and toughness, thereby greatly optimizing the mechanical performance of the alloy under complex stress environments. At the same time, the eutectic Si phase further improves the dispersion of Si in the melt, enabling the Si element to fully diffuse in the Al-Si alloy, thereby shortening the preparation time of cast Al-Si alloys.

[0072] Mg2Si phase is an intermetallic compound with a nanoparticle structure in microstructure. It has a high melting temperature (1358K), a low thermal expansion coefficient (7.5×10 -6 K -1 ) and high Young's modulus (120GPa), and is distributed in a fine and dispersed state in the aluminum matrix. Therefore, the Mg2Si phase can act as a reinforcement, which helps to improve the strength and rigidity of the alloy. At the same time, the presence of the Mg2Si phase promotes the uniform diffusion of the Mg element in the cast Al-Si alloy, reduces the loss of the Mg element, and ensures the accuracy of the composition.

[0073] The Al8Mn5 phase is an intermetallic compound that exhibits a finely dispersed, skeletal or blocky structure within the aluminum matrix. It is a high-temperature stable phase. In Al-Si-Mn-Mg alloys, it primarily strengthens the matrix, improves high-temperature performance, and refines grain size, making it a key factor in enhancing the alloy's overall performance.

[0074] In order to prove the element content of the master alloy, the master alloy was subjected to SEM-EDS surface composition analysis under the conditions of 100 times magnification and 3 statistical positions. The test results are as follows: Figure 4 As shown, the test results are statistically analyzed, and the statistical results are shown in Table 2;

[0075] Table 2 SEM-EDS results of master alloy composition

[0076]

[0077] The test results show that the measured results of the phase composition and element content in the master alloy of Example 1 are consistent with the theoretical addition amount;

[0078] In order to demonstrate the role of the master alloy, that is, the feasibility of preparing a cast Al-Si-Mn-Mg alloy based on the master alloy, the master alloy was used to prepare a cast Al-Si-Mn-Mg alloy.

[0079] A preparation method for casting an Al-Si-Mn-Mg alloy based on an Al-Si-Mn-Mg quaternary master alloy, specifically comprising the following steps: first, preparing a master alloy and pure Al to meet a composition ratio of 5:1, specifically, adding 200g of the master alloy and 800g of pure Al, placing the pure Al in a crucible, then preheating the crucible at a preheating temperature of 400°C to remove moisture from the crucible and the alloy, and then smelting the pure Al at a melting temperature of 800°C until the pure Al is melted. After calcination, the surface slag and oxide scale are removed. Then, the master alloy is wrapped with aluminum foil and preheated at 150°C. The preheated master alloy is pressed into a pure Al melt and fully stirred for 30 seconds. Then, it is allowed to stand at 800°C for 1 hour. During the standing process, it is fully stirred every 20 minutes. Then, the casting temperature is adjusted to 720°C, and the melt is cast into a permanent mold preheated at 250°C and solidified and cooled to obtain a cast Al-Si-Mn-Mg alloy.

[0080] To demonstrate the uniformity of the microstructure of the resulting cast Al-Si-Mn-Mg alloy and the dissolution of the primary Si phase, metallographic characterization tests were conducted on the cast Al-Si-Mn-Mg alloy at different holding times at a magnification of 50 times. The test results show that the primary Si phase in the master alloy rapidly dissolves during the preparation process of the cast Al-Si-Mn-Mg alloy, resulting in a uniformly structured cast Al-Si-Mn-Mg alloy.

[0081] In order to prove the element content of the obtained cast Al-Si-Mn-Mg alloy, component analysis was carried out by direct reading spectroscopy test. Three test positions were tested for each sample. The test results are shown in Table 3. The measured results of the elemental composition of the intermediate alloy obtained by the preparation method of the present invention are consistent with the target addition amount, that is, the intermediate alloy prepared by the present invention can be used for casting Al-Si-Mn-Mg alloy.

[0082] Table 3 Direct reading spectrometry results of Al-Si alloys prepared using master alloys

[0083]

[0084] Metallographic structure tests and direct reading spectroscopy tests show that the intermediate alloy prepared by the semi-solid method can promote the rapid dissolution of eutectic Si. At the same time, combined with the semi-solid method, the problem of burnout of low-melting-point Mg elements during the smelting process is solved, so that the composition of the obtained cast Al-Si-Mn-Mg alloy is consistent with the design value, and ultimately the preparation process of the cast Al-Si-Mn-Mg alloy is simplified.

[0085] In order to demonstrate the effectiveness of the screening method of the present invention, Example 2, Comparative Example 1 and Comparative Example 2 are provided, wherein:

[0086] The alloy composition of Example 2 satisfies composition region 1, that is, the alloy composition and phase content that meet the screening conditions, and also meet the semi-solid temperature range of the screening conditions. The alloy composition of Example 2 is Al-60Si-3.6Mn-1.8Mg;

[0087] The alloy composition of Comparative Example 1 satisfies composition region 2, i.e., the alloy composition that satisfies the screening conditions, but does not satisfy the phase content and semi-solid temperature range of the screening conditions. The alloy composition of Comparative Example 2 is Al-30Si-1.8Mn-0.9Mg;

[0088] The alloy composition of Comparative Example 2 satisfies composition region 2, that is, the alloy composition that satisfies the screening conditions, and also satisfies the semi-solid temperature range of the screening conditions, but does not meet the phase content of the screening conditions. The alloy composition of Comparative Example 1 is Al-40Si-2.4Mn-1.2Mg;

[0089] Example 2

[0090] A method for screening an Al-Si-Mn-Mg quaternary master alloy for a high-melting-point Mn element, wherein the steps not otherwise specified are the same as those of Example 1, except that: in order to satisfy composition region 1, the alloy mass ratio satisfies the conditions of Al-60Si-3.6Mn-1.8Mg, and the calculated content of the Al8Mn5 phase in Example 2 is 17.9 mol%;

[0091] Furthermore, for the preparation method of the Al-Si-Mn-Mg quaternary master alloy with a high melting point Mn element, the steps unless otherwise specified are the same as those in Example 1, except that: the amount of pure Al added is 184 g, the amount of pure Si added is 600 g, the amount of Al-20Mn master alloy added is 180 g, and the amount of Al-50Mg master alloy added is 36 g. In particular, in Example 2, the change in alloy composition leads to a change in the melting point of the alloy, which has no substantial effect on the selection of the semi-solid temperature, i.e., no adjustment is required.

[0092] The area ratios of the primary Si phase and the eutectic Si phase in Example 2 were statistically analyzed, and the amount fractions of the substances were calculated based on the area ratios of the phases. The statistical results are shown in Table 1. The test results show that the measured amount fractions of the primary Si phase and the eutectic Si phase are consistent with the theoretical calculation results, indicating that the screening method of the present invention is effective and accurate.

[0093] The master alloy of Example 2 was subjected to surface composition analysis using SEM-EDS, and the test results were statistically analyzed. The statistical results are shown in Table 2. The test results show that the measured element contents in the master alloy of Example 2 are consistent with the theoretical addition amounts.

[0094] Based on the test results of Examples 1 and 2, it can be demonstrated that the Al-Si-Mn-Mg alloy in composition region 1, i.e., the master alloy composition Al-(9-11)d Si-(0.5-0.8)d Mn-(0.2-0.5)d Mg, wherein the parameter d>4, the phase content f(Si) ≥30 mol%, f(Al8Mn5) ≥5 mol%, and the semi-solid temperature range ΔT ≥100°C, all have the following conclusions:

[0095] 1. The screening method of the present invention can accurately predict the content of primary Si phase and eutectic Si phase in the master alloy, obtain dispersed Si phase and Al8Mn5 phase, and promote the rapid diffusion of alloying elements;

[0096] 2. The intermediate alloy obtained by the screening method and preparation method of the present invention uses a semi-solid burial method to introduce the Mg element, which reduces the segregation of the Mn element and the burn-off of the Mg element during the production process, and obtains a uniform intermediate alloy structure and accurate target composition.

[0097] Comparative Example 1

[0098] A method for screening an Al-Si-Mn-Mg quaternary master alloy containing a high-melting-point Mn element, wherein the steps not otherwise specified are the same as those of Example 1, except that: to satisfy composition region 2, the alloy mass ratio satisfies the conditions of Al-30Si-1.8Mn-0.9Mg, the phase content of Comparative Example 1 satisfies f(Si) < 30 mol%, f(Al8Mn5) < 5 mol%, the semi-solid temperature range ΔT of Comparative Example 1 is < 100°C, and no Al8Mn5 phase is generated in the calculated results;

[0099] Furthermore, for the preparation method of the Al-Si-Mn-Mg quaternary master alloy with a high melting point Mn element, the steps unless otherwise specified are the same as those in Example 1, except that: the amount of pure Al added is 592 g, the amount of pure Si added is 300 g, the amount of Al-20Mn master alloy added is 90 g, and the amount of Al-50Mg master alloy added is 18 g; the melting temperature of Comparative Example 1 is 1000°C, the casting temperature is 900°C, and the semi-solid temperature is 600°C.

[0100] The area ratios of the primary Si phase and the eutectic Si phase in Comparative Example 1 were statistically analyzed, and the amount fractions of the substances were calculated based on the area ratios of the phases. The statistical results are shown in Table 1. The test results show that the measured amount fractions of the primary Si phase and the eutectic Si phase are consistent with the theoretical calculation results, indicating that the screening method of the present invention is effective and accurate.

[0101] The SEM analysis of Comparative Example 1 shows that there is a segregation area of ​​Mn element in Comparative Example 1;

[0102] SEM-EDS surface composition analysis was performed on Comparative Example 1, and the test results were statistically analyzed. The statistical results are shown in Table 2. The test results show that the measured results of the Mg and Mn element contents in the master alloy of Comparative Example 1 are inconsistent with the theoretical addition amounts.

[0103] Comparative Example 2

[0104] A method for screening an Al-Si-Mn-Mg quaternary master alloy for a high-melting-point Mn element, wherein the steps not otherwise specified are the same as those of Example 1, except that: to satisfy composition region 2, the alloy mass ratio satisfies the conditions of Al-40Si-2.4Mn-1.2Mg, the phase content of Comparative Example 1 satisfies f(Si)>30mol%, f(Al8Mn5)<5mol%, and the calculated content of Al8Mn5 phase in Comparative Example 2 is 3.5mol%;

[0105] Furthermore, for the preparation method of the Al-Si-Mn-Mg quaternary master alloy with a high melting point Mn element, the steps unless otherwise specified are the same as those in Example 1, except that: the amount of pure Al added is 456 g, the amount of pure Si added is 400 g, the amount of Al-20Mn master alloy added is 120 g, and the amount of Al-50Mg master alloy added is 24 g; the melting temperature of Comparative Example 1 is 1000°C, the casting temperature is 900°C, and the semi-solid temperature range is 650°C.

[0106] The area ratios of the primary Si phase and the eutectic Si phase in Comparative Example 2 were statistically analyzed, and the amount fractions of the substances were calculated based on the area ratios of the phases. The statistical results are shown in Table 1. The test results show that the measured amount fractions of the primary Si phase and the eutectic Si phase are consistent with the theoretical calculation results, indicating that the screening method of the present invention is effective and accurate.

[0107] The surface composition analysis of Comparative Example 2 was performed by SEM-EDS, and the test results were statistically analyzed. The statistical results are shown in Table 2. The test results show that the measured results of the phase composition and element content in the intermediate alloy of Comparative Example 2 are consistent with the theoretical addition amount.

[0108] Compared with Comparative Example 1, Comparative Example 2 and Example 1, it can be seen that the composition region has a significant influence on the preparation of the master alloy, that is, when the alloy composition is Al-(9-11)d Si-(0.5-0.8)d Mn-(0.2-0.5)d Mg, and the parameters d<4, the phase content f(Si)<30 mol%, f(Al8Mn5)<5 mol%, the content of Si phase and Al8Mn5 phase in the alloy is low, and when the Al-Si-Mn-Mg master alloy is used to prepare the cast Al-Si alloy, it cannot meet the element content requirement of the AlSi10MnMg alloy and the phase content requirement for rapid dispersion of Si element and Mn element through primary Si phase and Al8Mn5 phase. The semi-solid temperature interval of Comparative Example 1 is only 70℃, and because the semi-solid temperature interval is small, when the temperature is too high, the solid phase rate in the melt decreases rapidly, and the burying effect of the semi-solid method cannot be met, and when the temperature is too low, the melt is close to solidification, and the element adding operation is difficult, so the semi-solid temperature interval has a significant influence on the alloy composition, that is, when the semi-solid temperature interval of the alloy ΔT<100℃, the Mg element is obviously burned, and the accurate alloy composition cannot be obtained.

Claims

1. A method for screening Al-Si-Mn-Mg quaternary master alloys for high melting point Mn elements, characterized in that The following steps are involved: Step 1: Set up phase diagram calculation and solidification simulation parameters. Phase diagram calculation includes selecting the phase diagram type and setting the alloying element types. Solidification simulation includes selecting the calculation model and setting the alloying element types and compositions. Step 2: Based on the phase diagram calculation results and the solidification simulation results, set the master alloy composition screening conditions, which include the composition range and the temperature range. The screening conditions must meet all three screening conditions at the same time. Step 3: Confirm the composition of the intermediate alloy that meets the screening requirements. In the Al-Si-Mn-Mg alloy thermodynamic phase diagram, select the liquid phase projection surface and the phase composition area that meets the screening requirements in step 2 to confirm the phase composition area that meets the screening requirements.

2. The screening method according to claim 1, characterized in that: In step 1, the phase diagram type is selected as follows: the liquid phase projection surface and the liquidus temperature contour line of the ternary system are calculated using Pandat software and the Phase Projection in the PanPhaseDiagram phase diagram module is selected; The calculation step size of the liquidus temperature contour line is 100°C; The alloy element types calculated in the phase diagram are set as follows: the alloy element types include Al element, Si element, Mn element and Mg element; The calculation model of the solidification simulation is selected by using Pandat software and selecting the Scheil-Gulliver model in the PanPhaseDiagram phase diagram module for solidification simulation; The composition setting in the solidification simulation is Si: 10d, Mn: 0.6d, Mg: 0.35d, and the balance is Al, where d≥4.

3. The method for screening the master alloy according to claim 1, characterized in that: In step 2, the screening conditions for the intermediate alloy composition simultaneously meet the following three screening conditions: The intermediate alloy composition screening condition 1 is that the Si element, the Mn element and the Mg element satisfy the alloy composition Al-(9-11)dSi-(0.5-0.8)dMn-(0.2-0.5)dMg, wherein the parameter d≥4, The second screening condition for the composition of the intermediate alloy is that the phase content of the intermediate alloy satisfies the following conditions: f(Si)≥30mol%, f(Al8Mn5)≥5mol%, The intermediate alloy composition screening condition 3 is that the semi-solid temperature range of the intermediate alloy is ΔT≥100°C.

4. The method for screening the master alloy according to claim 3, characterized in that: In the screening condition 3, the semi-solid period of the solidification process of the master alloy must meet the solid phase ratio: f(s)=0.2-0.

8.

5. A method for preparing an Al-Si-Mn-Mg quaternary master alloy containing a high-melting-point Mn element, characterized in that: First, raw materials are prepared to meet the mass ratio, and pure Al, pure Si, Al-20Mn master alloy and Al-20Si master alloy are placed in a crucible. Then, the crucible and the master alloy are preheated at a preheating temperature to remove water vapor in the crucible and the alloy. Thereafter, they are heated at a melting temperature. After the pure Al, pure Si, Al-20Mn master alloy and Al-20Si master alloy are melted, surface slag and oxide scale are removed to obtain an aluminum alloy melt. Next, the Al-50Mg master alloy is wrapped with aluminum foil and preheated at a preheating temperature, and the temperature of the aluminum alloy melt is lowered to a semi-solid temperature range. Subsequently, the preheated Al-50Mg master alloy is pressed into the semi-solid aluminum alloy melt. Finally, it is cast at a casting temperature and solidified and cooled to obtain an Al-Si-Mn-Mg quaternary master alloy produced by a semi-solid method.

6. The preparation method according to claim 5, characterized in that: The preheating temperature of the crucible and the master alloy is 200-400°C; The melting temperature of the master alloy is 900-1200°C; The casting temperature of the master alloy is 800-1100°C.

7. A method for preparing an Al-Si-Mn-Mg alloy by casting an Al-Si-Mn-Mg quaternary master alloy, characterized in that The method comprises the following steps: firstly, weighing pure Al and an intermediate alloy so as to meet a mass ratio condition, placing the pure Al into a crucible, then preheating the crucible at a preheating temperature to remove moisture in the crucible and the alloy, then heating at a melting temperature, and after the pure Al is melted, removing surface slag and oxide scale, then wrapping the intermediate alloy with aluminum foil and preheating it at a preheating temperature, pressing the preheated intermediate alloy into the pure Al melt, fully stirring it for a stirring time, then standing it at the melting temperature for 1 hour, fully stirring it every 20 minutes during the standing process, then adjusting the casting temperature, casting the melt into a permanent mold preheated at the preheating temperature, solidifying and cooling it, and thus obtaining a cast Al-Si-Mn-Mg alloy.

8. The preparation method according to claim 7, characterized in that: The preheating temperature of the crucible and raw materials is 200-400°C; The melting temperature of the cast Al-Si-Mn-Mg alloy is 750-850°C; The casting temperature of the Al-Si-Mn-Mg alloy is 700-750°C.

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