Preparation method of large-deformation auxiliary high-homogeneity aluminum-silicon intermediate alloy

Abstract

The invention discloses a preparation method of a large-deformation auxiliary high-homogeneity aluminum-silicon intermediate alloy. The method comprises the following steps: 1, mixing aluminum powder and silicon powder to obtain aluminum-silicon mixed powder; 2, performing cold isostatic pressing on the aluminum-silicon mixed powder; 3, vacuum sintering; 4, removing oxide skin on the surface; 5, carrying out plastic deformation at ultralow temperature after sheathing; and sixthly, homogenizing treatment is conducted, and the high-homogeneity aluminum-silicon intermediate alloy is obtained. According to the method, the powder metallurgy method is combined with ultralow-temperature extrusion severe plastic deformation, intermediate alloy densification and primary silicon crushing and homogenization are achieved under three-way pressure stress, the aluminum-silicon intermediate alloy high in density, refined in grain and high in homogeneity is obtained, and the aluminum-silicon intermediate alloy has the advantages of being high in purity and homogeneity, low in impurity element content and good in mechanical property. The method is suitable for adding materials in the preparation process of aluminum-silicon alloy and titanium alloy.

Description

Technical Field

[0001] The invention relates to the technical field of master alloy preparation, and in particular to a method for preparing a large deformation-assisted high-homogeneity aluminum-silicon master alloy. Background Art

[0002] At present, the process of preparing aluminum-silicon master alloy by melting and remelting aluminum ingots is complicated and has a long production and processing cycle. At the same time, directly adding crystalline silicon to aluminum melt will cause great burning loss, especially silicon powder is not suitable for preparing aluminum-silicon alloy by direct addition and smelting. The density of aluminum liquid and silicon is similar, which makes aluminum liquid easy to float on the surface of the melt, and it is difficult to accurately control the composition of aluminum-silicon master alloy. Aluminum and silicon have large melting point differences and density differences. Aluminum is almost insoluble in silicon. The maximum solubility of silicon in aluminum at 577°C is only 1.65%. Therefore, it can be considered that silicon in the alloy exists in the form of pure silicon; when the silicon content exceeds 13%, its organization contains a large amount of primary silicon, and the size of the primary silicon is relatively large. In addition, the brittleness of the alloy makes it difficult to use traditional plastic deformation to assist homogenization. There is a bottleneck in the preparation technology of aluminum-silicon master alloy, and cost reduction and efficiency improvement are imminent.

[0003] The patent with publication number CN103233135A discloses a method for preparing aluminum-silicon master alloy by microwave sintering, which uses metal silicon powder and aluminum powder as raw materials, presses and forms them, and then sinters them at 1100℃~1200℃ for 1h~3h to prepare aluminum-silicon master alloy. This method can reduce the oxidation of the alloy and reduce the segregation and agglomeration of silicon elements, but the degree of alloying of silicon and aluminum elements is low when only the direct sintering method is used, the gas discharge inside the blank is blocked, and there is large primary silicon crystal, and the alloy uniformity is poor.

[0004] Patent publication number CN105543517A discloses a method for preparing an aluminum-silicon master alloy, which involves wrapping industrial silicon particles with aluminum foil and then smelting them. This method can effectively solve the problem of silicon oxidation during the preparation of the master alloy, but it still cannot effectively solve the problem of silicon segregation and processing difficulties.

[0005] The patent with publication number CN117165877A discloses a preparation method for improving the performance of aluminum alloys. The aluminum alloy forging blank is heated after multi-directional forging in the range of -196℃ to -120℃, and the mechanical properties can be improved after aging treatment. This method fully refines the second phase through the strong shearing effect of ultra-low temperature deformation, and uses low temperature conditions to suppress dynamic recovery and produce high-density dislocations. In the subsequent solid solution process, the second phase after crushing is fully dissolved, the recrystallization nucleation points are increased, the grains of the material are refined, and the microstructure of the material is improved, thereby improving the mechanical properties of the component. However, multi-directional forging cannot be achieved for aluminum-silicon intermediate alloys with greater brittleness, and the ultra-low temperature plasticization effect cannot be fully exerted, making it difficult to solve the homogenization problem.

[0006] Therefore, it is necessary to propose a large deformation assisted high-homogeneity aluminum-silicon master alloy preparation method, aiming to solve the problem of how to prepare an aluminum-silicon master alloy with high density, refined grains and high homogeneity. Summary of the invention

[0007] The technical problem to be solved by the present invention is to provide a method for preparing a high-homogeneity aluminum-silicon intermediate alloy assisted by large deformation in view of the deficiencies of the above-mentioned prior art. The method adopts a powder metallurgy method to prepare a sintered preform of the intermediate alloy, and then combines ultra-low temperature extrusion with large plastic deformation, and realizes the densification of the intermediate alloy, the crushing of the primary silicon crystal and the homogenization through ultra-low temperature processing with three-way compressive stress, so as to obtain an aluminum-silicon intermediate alloy with high density, fine grains and high homogeneity, which solves the problems of large aluminum burnout and complex preparation process in the existing aluminum-silicon intermediate alloy melting and remelting aluminum ingot method, insufficient alloying degree of aluminum and silicon elements in direct vacuum sintering, and high brittleness of the intermediate alloy, which is difficult to achieve homogenization through traditional deformation heat treatment.

[0008] In order to solve the above technical problems, the technical solution adopted by the present invention is: a large deformation assisted high homogeneity aluminum-silicon master alloy preparation method, characterized in that the method comprises the following steps:

[0009] Step 1, uniformly mixing aluminum powder and silicon powder with a mass purity of more than 99.5% to obtain aluminum-silicon mixed powder; the mass content of silicon powder in the aluminum-silicon mixed powder is 10% to 60%;

[0010] Step 2: Place the aluminum-silicon mixed powder obtained in step 1 into a cold isostatic pressing mold, vacuum seal it, and maintain the pressure at 200 MPa to 300 MPa for 5 to 10 minutes to obtain a cold isostatic pressing block;

[0011] Step 3: vacuum sintering the cold isostatic pressed block obtained in step 2 at 580° C. to 650° C. for 2 h to 4 h to obtain an aluminum-silicon master alloy sintered preform;

[0012] Step 4: removing 1 mm to 3 mm of oxide scale from the surface of the aluminum-silicon master alloy sintered preform obtained in step 3;

[0013] Step 5: Wrap the aluminum-silicon master alloy sintered preform after the oxide scale is removed in step 4 with an aluminum sheath, and put it into an extrusion die, and then perform plastic deformation at an extrusion ratio of 2 to 10:1 at an ultra-low temperature below -150°C to obtain a master alloy extruded billet;

[0014] Step 6: homogenize the master alloy extrusion billet obtained in step 5 at 350° C. to 450° C. for 1 h to 3 h, and obtain a highly homogeneous aluminum-silicon master alloy after removing the aluminum sheath.

[0015] The above-mentioned large deformation assisted high-homogeneity aluminum-silicon master alloy preparation method is characterized in that the composition and particle size of the aluminum powder in step one conform to the GB / T 2085.2-2019 "Aluminum Powder" standard, and the composition and particle size of the silicon powder conform to the YS / T724-2016 "Silicon Powder for Polysilicon" standard.

[0016] The above-mentioned large deformation assisted high-homogeneity aluminum-silicon master alloy preparation method is characterized in that the particle sizes of the aluminum powder and the silicon powder are both -200 mesh to -325 mesh. By controlling the particle sizes of the raw aluminum powder and silicon powder, the problem of insufficient density of the aluminum-silicon master alloy sintered preform due to excessively large particle sizes is avoided, and the problem of high cost caused by the high price of raw powder with too small particle sizes is avoided.

[0017] The above-mentioned large deformation assisted high-homogeneity aluminum-silicon master alloy preparation method is characterized in that the rotation speed of the uniform mixing of the aluminum powder and the silicon powder in step one is 30r / min to 60r / min, and the mixing time is 2h to 4h.

[0018] The above-mentioned large deformation assisted high homogeneity aluminum-silicon master alloy preparation method is characterized in that the vacuum sintering in step 3 maintains a vacuum degree of 5×10 -2 Below Pa.

[0019] The above-mentioned large deformation assisted high-homogeneity aluminum-silicon master alloy preparation method is characterized in that the plastic deformation in step five is extrusion deformation under triaxial compressive stress at an ultra-low temperature of -150°C to -196°C, the ultra-low temperature is achieved by liquid nitrogen and / or liquid argon coolant, and the extrusion deformation rate is 2mm / s to 20mm / s.

[0020] The above-mentioned large deformation assisted high-homogeneity aluminum-silicon master alloy preparation method is characterized in that the high-homogeneity aluminum-silicon master alloy obtained in step six is ​​crushed to obtain aluminum-silicon master alloy blocks, or is machined to obtain aluminum-silicon master alloy chips.

[0021] The above-mentioned large deformation assisted high-homogeneity aluminum-silicon master alloy preparation method is characterized in that the particle size of the aluminum-silicon master alloy block is 1mm to 20mm, and the specifications of the aluminum-silicon master alloy chips are thickness not exceeding 1mm, length not exceeding 20mm, and width not exceeding 10mm.

[0022] Compared with the prior art, the present invention has the following advantages:

[0023] 1. The present invention adopts vacuum sintering after pressing uniformly mixed aluminum powder and silicon powder, which reduces the oxidation of the alloy and the segregation and agglomeration of silicon elements, improves the uniformity of the aluminum-silicon master alloy, and realizes the preparation of high-silicon content aluminum-based master alloy.

[0024] 2. The present invention utilizes the property of improved plasticity of aluminum-silicon alloy at ultra-low temperature, and prepares highly homogeneous aluminum-silicon intermediate alloy by ultra-low temperature extrusion and large plastic deformation. Ultra-low temperature three-way compressive stress deformation fully refines large-sized primary silicon crystals, and utilizes low temperature conditions to inhibit the dynamic recovery of the aluminum matrix, generate high-density dislocations, increase recrystallization nucleation points, achieve densification of the aluminum-silicon intermediate alloy, crushing of the primary silicon crystals and homogenization, and obtain an aluminum-silicon intermediate alloy with high density and refined grains.

[0025] 3. The present invention homogenizes the intermediate alloy extrusion billet after large plastic deformation to achieve full dissolution of the primary silicon phase after crushing, obtains a small-sized and evenly distributed silicon phase, and obtains a highly homogeneous aluminum-silicon intermediate alloy.

[0026] 4. The high-homogeneity aluminum-silicon intermediate alloy prepared by the present invention has the characteristics of high purity and high homogeneity, and the content of impurity elements is low. When it is used as an additive material in the preparation process of aluminum-silicon alloy and titanium alloy, it not only has a low melting temperature and a short melting time, which is beneficial to minimize segregation and ensure the service performance of the material, but also can improve production efficiency and alloy yield.

[0027] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is the metallographic structure diagram of the highly homogeneous AlSi10 master alloy chips prepared in Example 1 of the present invention.

[0029] Figure 2 This is a physical picture of the highly homogeneous AlSi10 master alloy chips prepared in Example 1 of the present invention.

[0030] Figure 3 This is the metallographic structure diagram of the highly homogeneous AlSi30 intermediate alloy block prepared in Example 2 of the present invention.

[0031] Figure 4 This is a physical picture of the highly homogeneous AlSi60 intermediate alloy block prepared in Example 3 of the present invention. DETAILED DESCRIPTION

[0032] Example 1

[0033] This embodiment includes the following steps:

[0034] Step 1: 900 g of aluminum powder with a mass purity of 99.95% and 100 g of silicon powder with a mass purity of 99.9% are uniformly mixed using a powder mixer. The composition and particle size of the aluminum powder conform to the GB / T2085.2-2019 "Aluminum Powder" standard, and the composition and particle size of the silicon powder conform to the YS / T 724-2016 "Silicon Powder for Polysilicon" standard. The particle sizes of the aluminum powder and the silicon powder are both -200 mesh. The speed of the powder mixer for uniform mixing is 30 r / min, and the mixing time is 2 h to obtain an aluminum-silicon mixed powder with a mass content of 10% of silicon powder;

[0035] Step 2: Place the aluminum-silicon mixed powder obtained in step 1 into a cold isostatic pressing mold, vacuum seal it, and maintain the pressure at 200 MPa for 5 minutes to obtain a cold isostatic pressing block;

[0036] Step 3: The cold isostatic pressed block obtained in step 2 is kept at 580°C for 4 hours for vacuum sintering, and the vacuum degree is maintained at 5×10 -2 Pa or less, and the aluminum-silicon master alloy sintered preform is obtained;

[0037] Step 4: removing 1 mm of oxide scale from the surface of the aluminum-silicon master alloy sintered preform obtained in step 3;

[0038] Step 5: Wrap the aluminum-silicon master alloy sintered preform after the oxide skin is removed in step 4 with an aluminum sheath, and put it into an extrusion die, and then extrude it under a three-axis compressive stress with an extrusion ratio of 10:1 at an ultra-low temperature of -160°C, and the extrusion deformation rate is 20 mm / s to obtain a master alloy extruded billet; the ultra-low temperature is achieved by a liquid nitrogen coolant;

[0039] Step 6: The intermediate alloy extrusion billet obtained in step 5 is homogenized by keeping it at 350° C. for 1 hour, and after removing the aluminum sheath, high-homogeneity AlSi10 intermediate alloy chips are obtained by machining, and the specifications of the high-homogeneity AlSi10 intermediate alloy chips are 0.1 mm in thickness, 15 mm in length, and 8 mm in width.

[0040] Figure 1 The metallographic structure diagram of the highly homogeneous AlSi10 master alloy chips prepared in this embodiment is shown in FIG. Figure 1 It can be seen that the highly homogeneous AlSi10 master alloy chips contain a large amount of dendritic aluminum because they are below the eutectic point.

[0041] Figure 2 This is a physical picture of the highly homogeneous AlSi10 master alloy chips prepared in this embodiment. Figure 2 It can be seen that the surface of the highly homogeneous AlSi10 master alloy chips has a metallic natural luster without abnormal color.

[0042] Example 2

[0043] This embodiment includes the following steps:

[0044] Step 1: 7kg of aluminum powder with a purity of 99.95% by mass and 3kg of silicon powder with a purity of 99.9% by mass are uniformly mixed with a double-action powder mixer. The composition and particle size of the aluminum powder conform to the GB / T2085.2-2019 "Aluminum Powder" standard, and the composition and particle size of the silicon powder conform to the YS / T 724-2016 "Silicon Powder for Polysilicon" standard. The particle sizes of the aluminum powder and the silicon powder are both -325 mesh. The speed of the powder mixer for uniform mixing is 50r / min, and the mixing time is 3h to obtain an aluminum-silicon mixed powder with a mass content of 30% of silicon powder;

[0045] Step 2: Place the aluminum-silicon mixed powder obtained in step 1 into a cold isostatic pressing mold, seal it in vacuum, and then maintain the pressure at 250 MPa for 8 minutes to obtain a cold isostatic pressing block;

[0046] Step 3: The cold isostatic pressed block obtained in step 2 is kept at 610°C for 3 hours for vacuum sintering, and the vacuum degree is maintained at 3.0×10 -3 Pa or less, and the aluminum-silicon master alloy sintered preform is obtained;

[0047] Step 4: removing 2 mm of oxide scale from the surface of the aluminum-silicon master alloy sintered preform obtained in step 3;

[0048] Step 5: Wrap the aluminum-silicon master alloy sintered preform after the oxide skin is removed in step 4 with an aluminum sheath, and put it into an extrusion die, and then extrude it under a three-axis compressive stress with an extrusion ratio of 5:1 at an ultra-low temperature of -180°C, and the extrusion deformation rate is 10 mm / s to obtain a master alloy extruded billet; the ultra-low temperature is achieved by liquid nitrogen and / or liquid argon coolant;

[0049] Step 6: homogenize the intermediate alloy extrusion billet obtained in step 5 at 400° C. for 2 hours, remove the aluminum sheath and obtain a highly homogeneous AlSi30 intermediate alloy block by crushing, wherein the particle size of the highly homogeneous AlSi30 intermediate alloy block is 1 mm to 10 mm.

[0050] Figure 3 This is the metallographic structure diagram of the highly homogeneous AlSi30 master alloy block prepared in this embodiment. Figure 3 It can be seen that the high-homogeneity AlSi30 intermediate alloy block has an aluminum-silicon phase because the Si content is above the eutectic point of 13%. However, the primary silicon in the high-homogeneity AlSi30 intermediate alloy block prepared by the method of the present invention is in the form of small particles and is significantly refined.

[0051] Example 3

[0052] This embodiment includes the following steps:

[0053] Step 1: 4 kg of aluminum powder with a purity of 99.7% by mass and 6 kg of silicon powder with a purity of 99.95% by mass are uniformly mixed with a powder mixer. The composition and particle size of the aluminum powder conform to the GB / T 2085.2-2019 "Aluminum Powder" standard, and the composition and particle size of the silicon powder conform to the YS / T 724-2016 "Silicon Powder for Polysilicon" standard. The particle size of the aluminum powder is -200 mesh, and the particle size of the silicon powder is -325 mesh. The speed of the powder mixer for uniform mixing is 60 r / min, and the mixing time is 4 hours to obtain an aluminum-silicon mixed powder with a mass content of 60% of silicon powder;

[0054] Step 2: Place the aluminum-silicon mixed powder obtained in step 1 into a cold isostatic pressing mold, seal it under vacuum, and maintain the pressure at 300 MPa for 10 minutes to obtain a cold isostatic pressing block;

[0055] Step 3: The cold isostatic pressed block obtained in step 2 is sintered in vacuum at 650°C for 4 hours, and the vacuum degree is maintained at 4.0×10 -3 Pa or less, and the aluminum-silicon master alloy sintered preform is obtained;

[0056] Step 4: removing 3 mm of oxide scale from the surface of the aluminum-silicon master alloy sintered preform obtained in step 3;

[0057] Step 5: Wrap the aluminum-silicon master alloy sintered preform after the oxide skin is removed in step 4 with an aluminum sheath, and put it into an extrusion die, and then extrude it under a three-axis compressive stress with an extrusion ratio of 2:1 at an ultra-low temperature of -196°C, and the extrusion deformation rate is 2 mm / s to obtain a master alloy extruded billet; the ultra-low temperature is achieved by a liquid nitrogen coolant;

[0058] Step 6: homogenize the intermediate alloy extrusion billet obtained in step 5 at 450° C. for 3 hours, remove the aluminum sheath and obtain a highly homogeneous AlSi60 intermediate alloy block by crushing, wherein the particle size of the highly homogeneous AlSi60 intermediate alloy block is 1 mm to 5 mm.

[0059] Figure 4 This is a physical picture of the highly homogeneous AlSi60 master alloy block prepared in this embodiment. Figure 4 It can be seen that the surface of the AlSi60 master alloy block is clean, without visible oil stains, oxide films and other metal and non-metal inclusions.

[0060] The chemical composition of the highly homogeneous aluminum-silicon master alloys prepared in Examples 1 to 3 of the present invention was tested, and the specific results are shown in Table 1 below.

[0061] Table 1 Chemical composition of aluminum-silicon master alloy (wt%)

[0062] element Al Si Fe C O N Example 1 margin 10.5 0.22 0.15 0.17 0.03 Example 2 margin 30.4 0.25 0.18 0.21 0.03 Example 3 margin 60.2 0.3 0.2 0.2 0.05

[0063] As can be seen from Table 1, the percentage of silicon in the high-homogeneity aluminum-silicon master alloys prepared in Examples 1 to 3 of the present invention is close to the designed value, and the content of impurity elements is low, especially carbon, oxygen and nitrogen elements, which means that the high-homogeneity aluminum-silicon master alloys prepared in the present invention completely avoid pollution from the external environment, and at the same time, changes in the preparation process parameters have little effect on the composition of the final high-homogeneity aluminum-silicon master alloy, and the process stability is good.

[0064] The above is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent change made to the above embodiment according to the technical essence of the invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. A method for preparing a high-homogeneity aluminum-silicon master alloy assisted by large deformation, characterized in that: The method comprises the following steps: Step 1, uniformly mixing aluminum powder and silicon powder with a mass purity of more than 99.5% to obtain aluminum-silicon mixed powder; the mass content of silicon powder in the aluminum-silicon mixed powder is 10% to 60%; Step 2: Place the aluminum-silicon mixed powder obtained in step 1 into a cold isostatic pressing mold, vacuum seal it, and maintain the pressure at 200 MPa to 300 MPa for 5 to 10 minutes to obtain a cold isostatic pressing block; Step 3: vacuum sintering the cold isostatic pressed block obtained in step 2 at 580° C. to 650° C. for 2 h to 4 h to obtain an aluminum-silicon master alloy sintered preform; Step 4: removing 1 mm to 3 mm of oxide scale from the surface of the aluminum-silicon master alloy sintered preform obtained in step 3; Step 5: Wrap the aluminum-silicon master alloy sintered preform after the oxide scale is removed in step 4 with an aluminum sheath, and put it into an extrusion die, and then perform plastic deformation at an extrusion ratio of 2 to 10:1 at an ultra-low temperature below -150°C to obtain a master alloy extruded billet; Step 6: homogenize the master alloy extrusion billet obtained in step 5 at 350° C. to 450° C. for 1 h to 3 h, and obtain a highly homogeneous aluminum-silicon master alloy after removing the aluminum sheath.

2. The method for preparing a high-homogeneity aluminum-silicon master alloy assisted by large deformation according to claim 1, characterized in that: The composition and particle size of the aluminum powder described in step 1 comply with the GB / T 2085.2-2019 "Aluminum Powder" standard, and the composition and particle size of the silicon powder comply with the YS / T 724-2016 "Silicon Powder for Polysilicon" standard.

3. The method for preparing a large deformation-assisted high-homogeneity aluminum-silicon master alloy according to claim 2, characterized in that: The particle sizes of the aluminum powder and silicon powder are both -200 mesh to -325 mesh.

4. The method for preparing a large deformation-assisted high-homogeneity aluminum-silicon master alloy according to claim 1, characterized in that: The rotation speed of uniformly mixing the aluminum powder and the silicon powder in step 1 is 30 r / min to 60 r / min, and the mixing time is 2 h to 4 h.

5. The method for preparing a large deformation-assisted high-homogeneity aluminum-silicon master alloy according to claim 1, characterized in that: The vacuum sintering in step 3 is performed with a vacuum degree of 5×10 -2 Below Pa.

6. The method for preparing a large deformation-assisted high-homogeneity aluminum-silicon master alloy according to claim 1, characterized in that: The plastic deformation in step five is extrusion deformation under triaxial compressive stress at an ultra-low temperature of -150°C to -196°C, the ultra-low temperature is achieved by liquid nitrogen and / or liquid argon coolant, and the extrusion deformation rate is 2mm / s to 20mm / s.

7. The method for preparing a high-homogeneity aluminum-silicon master alloy assisted by large deformation according to claim 1, characterized in that: The highly homogeneous aluminum-silicon master alloy obtained in step six is ​​crushed to obtain aluminum-silicon master alloy blocks, or is machined to obtain aluminum-silicon master alloy chips.

8. The method for preparing a high-homogeneity aluminum-silicon master alloy assisted by large deformation according to claim 7, characterized in that: The particle size of the aluminum-silicon master alloy block is 1 mm to 20 mm, and the specifications of the aluminum-silicon master alloy chips are that the thickness does not exceed 1 mm, the length does not exceed 20 mm, and the width does not exceed 10 mm.

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