Rare earth metal doped aluminum alloy composite modifier and preparation method therefor

Abstract

A rare earth (RE) metal doped aluminum alloy composite modifier, characterized by comprising the following components in percentage by mass: 0.85%-1.5% of Sr; 4.85%-7.15% of RE; and the balance being A1; and the ratio of the mass fraction of the RE to the mass fraction of the Sr is not less than 3.0 and not greater than 9.0. The modifier contains an Al-Sr-RE phase with fine crystal grains and uniform distribution, and compared with a conventional Sr modifier, the modifier has the advantages of lower modifier addition amount during modification, short inoculation time, long aging time, and high quality. Moreover, when an Al-Si alloy is added into the modifier, the modifier has a cast state tensile strength of 283.3 MPa and a yield strength of 180.9 MPa, and a good modification effect is achieved.

Description

A rare earth metal-doped aluminum alloy composite modifier and preparation method thereof Technical Field

[0001] The present invention relates to the technical field of cast aluminum alloys, and in particular to a rare earth metal-doped aluminum alloy composite modifier and a preparation method thereof. Background Art

[0002] The Al-Si series of cast aluminum alloys boast excellent fluidity, low thermal expansion and contraction, good weldability, and corrosion resistance, making them widely used in the automotive, electronics, and communications sectors. However, their relatively low plasticity limits their application in key automotive structural components.

[0003] In the Al-Si series of alloys, Si combines with Al to form a binary eutectic with excellent fluidity, but this fluidity increases and then decreases with Si content. Because Si has extremely low solubility in Al and its elastic modulus is more than twice that of Al, the Si phase becomes the primary source of cracks in the alloy.

[0004] The volume fraction of the Si phase is linearly related to the Si content, and its morphology, size, and distribution directly determine the alloy's plasticity. The eutectic structure exhibits coarse, needle-like flakes, which damage the Al matrix to a certain extent and cause stress concentration at the tips of the Si phase needles and certain corners. This makes the Si phase susceptible to spalling during machining, resulting in a rough and uneven machined surface, seriously affecting the quality of the casting.

[0005] In order to better exert the performance of hypoeutectic Al-Si alloy, it is usually necessary to modify the eutectic structure so that the eutectic silicon grows into multi-branched fibers and is more diffusely distributed in the matrix phase.

[0006] This reduces the scattering effect of irregular eutectic silicon on heat transfer electrons and eliminates the splitting effect of eutectic silicon on the alloy matrix, improving the thermal conductivity and mechanical properties of the alloy product. For example, the Si phase of unmodified A356 aluminum alloy after gravity casting is slender needle-like flakes with an elongation of only 3-4%.

[0007] However, after modification with Sr, Si transforms into fine fibers, which improves the plasticity of the casting. Therefore, modification of Si is one of the key strategies to improve the plasticity of Al-Si cast aluminum alloys.

[0008] Sr is the most common eutectic silicon modifier, achieving optimal modification effects when the Sr content in the melt is 200-500 ppm. However, due to its active chemical properties and its susceptibility to oxidation and burning, Sr content gradually decreases with holding time, severely impacting the timeliness and remelting properties of Sr modification. Furthermore, Sr is prone to gas absorption, increasing the tendency for casting defects such as porosity and looseness, significantly reducing alloy performance. Further research and development is required to overcome this drawback.

[0009] In view of this, the present invention is proposed. Technical issues

[0010] In order to overcome the above-mentioned defects of the prior art, the object of the present invention is to provide a rare earth metal-doped aluminum alloy composite modifier and a preparation method thereof.

[0011] In order to achieve the purpose of the present invention, the technical solutions adopted are as follows:

[0012] A rare earth metal-doped aluminum alloy composite modifier, calculated by mass percentage, comprising:

[0013] Sr 0.85-1.5%;

[0014] RE 4.85%-7.15%;

[0015] The margin is A1,

[0016] The RE is one or more of La and Ce;

[0017] The purity of the Sr is not less than 99.0%;

[0018] The Al is pure aluminum with a purity of 99.7% or more;

[0019] The mass fraction ratio of the RE to the Sr is not less than 3.0 and not more than 9.0.

[0020] In a preferred embodiment of the present invention, when the rare earth metal-doped aluminum alloy composite modifier is used to modify Al-Si cast aluminum alloy, the addition amount thereof is 1.5-2.5%.

[0021] A method for preparing a rare earth metal-doped aluminum alloy composite modifier comprises the following steps:

[0022] Metal remelting steps:

[0023] Melting the aluminum material and the raw material containing Sr and RE to obtain a melt;

[0024] The composite modifier is cast into a uniformly distributed Al-Sr-RE aluminum alloy composite modifier block containing an Al4 (SrRE) phase and an Al111RE3 phase.

[0025] Slag removal and degassing steps:

[0026] The aluminum alloy composite modifier block is subjected to argon rotary spray refining, and after the refining is completed, the surface slag needs to be salvaged;

[0027] Degassing effect testing steps:

[0028] Carry out in-furnace hydrogen measurement and K-mode fracture inspection on the products after slagging and degassing;

[0029] Steps for pouring into blocks:

[0030] After the mold is preheated, a release agent is sprayed on the mold surface and then the finished product is cast.

[0031] In a preferred embodiment of the present invention, the metal remelting step is specifically as follows: first, the aluminum material is completely melted at a temperature of 750-800°C to obtain a melt, a covering agent accounting for 0.02%-0.03% of the mass of the melt is added, and the raw material containing Sr and RE is added to the melt using a bell jar.

[0032] In a preferred embodiment of the present invention, the covering agent composition is: MgCl2: 38%~52%, KCl: 32~40%, BaCl2: 5~8%, CaF2: 3~5%.

[0033] In a preferred embodiment of the present invention, the argon rotary jet refining is specifically a molten aluminum rotary degasser with a rotor made of graphite;

[0034] Before refining, the graphite spin nozzle needs to be placed above the aluminum liquid and baked for about 15 minutes. After the temperature reaches 300°C, the machine is turned on for spin blowing refining. The purity of the graphite is 99.99%;

[0035] The purity of the argon gas used is 99.99%, the rotation speed of the rotary blowing head is 150-160r / min, and the rotary blowing refining time is 15-20min.

[0036] In a preferred embodiment of the present invention, the hydrogen is measured in the furnace by taking a spoonful of molten aluminum, placing it in the working chamber of the machine, and taking out the metal block after vacuuming for four minutes. The metal block is sawed in the middle and its cross section is observed. The minimum grade of the cross section is grade 3, otherwise the degassing operation is repeated.

[0037] In a preferred embodiment of the present invention, the K-die fracture detection uses a dedicated K-die, into which molten aluminum is poured, and after cooling, it is broken along the concave portion, and its fracture condition is observed. If the fracture is free of impurities, it is qualified, otherwise the degassing operation is repeated.

[0038] In a preferred embodiment of the present invention, the preheated temperature of the mold is 300°C.

[0039] In a preferred embodiment of the present invention, the finished product is a cylindrical sample with a weight of 100-1000 g and a diameter of about 10-100 mm.

[0040] In addition, an embodiment of the present invention further provides a method for preparing an Al-Si cast aluminum alloy, which is prepared using the above-mentioned composite modifier and has the advantage of excellent alloy properties.

[0041] It should also be noted that in the embodiments of the present invention, the rare earth metal-doped composite modifier of the aforementioned embodiment is used to modify the Al-Si cast aluminum alloy, and the addition amount of the rare earth metal-doped composite modifier is 1.5% to 2.5%. By limiting the addition amount, compared to the prior art, it not only saves costs but also effectively improves alloy strength, ensures modification efficiency, and achieves a good modification effect.

[0042] The beneficial effects of the present invention are:

[0043] The rare earth metal-doped aluminum alloy composite modifier contains fine-grained and evenly distributed Al-Sr-RE phase, which allows the added elements to be more evenly distributed in the metal to be modified. Compared with traditional Sr modifiers, it has the advantages of lower modifier addition amount during modification, shorter incubation time, longer aging time, low cost, high quality, and remeltability.

[0044] The addition of composite rare earth RE greatly reduces the cost of rare earth composite modifier, and after slagging degassing and degassing effect testing, the hydrogen content of the composite modifier can be greatly reduced, resulting in a high-quality composite modifier that can be used for factory and laboratory modification.

[0045] An embodiment of the present invention also provides a method for preparing an Al-Si cast aluminum alloy, which is prepared using the above-mentioned composite modifier and has the advantage of excellent alloy properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figures 1 and 2 are the microstructures of the aluminum alloy (AlSi10MnMg) before and after modification. Figure (a) shows the microstructure of the alloy without adding a modifier; Figure (b) shows the microstructure of the alloy after adding the Al-10Sr modifier; and Figure (c) shows the microstructure of the alloy after adding the Al-Sr-RE modifier of the present invention. DETAILED DESCRIPTION

[0047] To make the purpose, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Where the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased commercially. The process of the preparation method of the above-mentioned rare earth metal-doped composite modifier is described in detail below through specific examples:

[0048] Example 1

[0049] This embodiment provides a rare earth metal-doped composite modifier, which includes the following components by mass percentage: 0.85% Sr, 4.85% RE, and 94.3% Al; and is prepared by the following method:

[0050] S1: Pure aluminum material is placed in a crucible resistor and heated to 750°C. After the aluminum material is completely melted, a covering agent (composition: MgCl2: 48%, KCl: 39%, BaCl2: 8%, CaF2: 5%) with a mass of 0.02% of the melt is added. Subsequently, a material containing Sr, La, and Ce is pressed into the melt using a Ti alloy bell jar.

[0051] S2: Heat to 800℃, wait until the raw materials are completely melted, take samples to test the composition; then use argon cyclone refining method to remove slag and gas from the aluminum liquid, with the ventilation time of 15 minutes and the graphite rotor speed of 150r / min. After the refining, remove the slag from the surface of the aluminum liquid.

[0052] S3: The degassing effect is tested using two methods: hydrogen measurement in the furnace and K-mold fracture testing. The hydrogen meter results in a grade of 1. After the K-mold fracture testing, there is no impurity on the fracture surface. The degassing is qualified.

[0053] S4: Heat the mold to 300℃ for pouring. Spray a uniform layer of release agent before pouring. Pour the mold into a cylindrical sample with a weight of 100g and a diameter of about 10mm, and vacuum pack it.

[0054] Example 2

[0055] This embodiment provides a rare earth metal-doped composite modifier, which includes the following components by mass percentage: 0.95% Sr, 5.00% RE, and 94.05% Al; and is prepared by the following method:

[0056] S1: Pure aluminum material is placed in a crucible resistor and heated to 750°C. After the aluminum material is completely melted, a covering agent (composition: MgCl2: 48%, KCl: 39%, BaCl2: 8%, CaF2: 5%) with a mass of 0.02% of the melt is added. Subsequently, a material containing Sr, La, and Ce is pressed into the melt using a Ti alloy bell jar.

[0057] S2: Heat to 800℃, wait until the raw materials are completely melted, take samples to test the composition; then use argon cyclone refining method to remove slag and gas from the aluminum liquid, with the ventilation time of 15 minutes and the graphite rotor speed of 150r / min. After the refining, remove the slag from the surface of the aluminum liquid.

[0058] S3: The degassing effect is tested using two methods: hydrogen measurement in the furnace and K-mold fracture testing. The hydrogen meter results in a grade of 2. After the K-mold fracture testing, there are no impurities on the fracture surface. The degassing is qualified.

[0059] S4: Heat the mold to 300℃ for pouring. Spray a uniform layer of release agent before pouring. Pour the mold into a cylindrical sample with a weight of 200g and a diameter of about 30mm, and vacuum pack it.

[0060] Example 3

[0061] This embodiment provides a rare earth metal-doped composite modifier, comprising the following components by mass percentage: 1.05% Sr, 5.15% RE (35% La and 65% Ce), and 93.80% Al; and is prepared by the following method:

[0062] S1: Pure aluminum material is placed in a crucible resistor and heated to 750°C. After the aluminum material is completely melted, a covering agent (composition: MgCl2: 48%, KCl: 39%, BaCl2: 8%, CaF2: 5%) with a mass of 0.03% of the melt is added. Subsequently, a material containing Sr, La, and Ce is pressed into the melt using a Ti alloy bell jar.

[0063] S2: Heat to 800℃, wait until the raw materials are completely melted, take samples to test the composition; then use argon cyclone refining method to remove slag and gas from the aluminum liquid, with the ventilation time of 15 minutes and the graphite rotor speed of 150r / min. After the refining, remove the slag from the surface of the aluminum liquid.

[0064] S3: The degassing effect is tested using two methods: hydrogen measurement in the furnace and K-mold fracture testing. The hydrogen meter results in a grade of 3. After the K-mold fracture testing, there is no impurity on the fracture surface. The degassing is qualified.

[0065] S4: Heat the mold to 300℃ for pouring. Spray a uniform layer of release agent before pouring. Pour the mold into a cylindrical sample with a weight of 500g and a diameter of about 50mm, and vacuum pack it.

[0066] Example 4

[0067] This embodiment provides a method for preparing an Al-Si cast aluminum alloy, wherein the rare earth metal-doped composite modifier prepared in Example 1 is used to modify an AlSi10MnMg series aluminum-silicon cast alloy. The rare earth metal-doped composite modifier is added in an amount of 2.0%, Sr is added in an amount of 0.02%, and RE is added in an amount of 0.10%. Experimental results show that the tensile strength is 270.1 MPa, the yield strength is 193.5 MPa, and the elongation is 6.10.

[0068] Example 5

[0069] This example provides a method for preparing an Al-Si cast aluminum alloy. The rare earth metal-doped composite modifier prepared in Example 2 is used to modify an AlSi10MnMg series aluminum-silicon cast alloy. The rare earth metal-doped composite modifier is added in an amount of 1.5%, Sr in an amount of 0.015%, and RE in an amount of 0.075%. Experimental results show a tensile strength of 265.1 MPa, a yield strength of 188.5 MPa, and an elongation of 5.60.

[0070] Example 6

[0071] This example provides a method for preparing an Al-Si cast aluminum alloy. The rare earth metal-doped composite modifier prepared in Example 3 is used to modify an AlSi10MnMg series aluminum-silicon cast alloy. The rare earth metal-doped composite modifier is added in an amount of 2.5%, Sr in an amount of 0.025%, and RE in an amount of 0.125%. Experimental results show a tensile strength of 283.3 MPa, a yield strength of 180.9 MPa, and an elongation of 6.10.

[0072] Comparative Example 1

[0073] This embodiment provides a method for preparing an Al-Si cast aluminum alloy by remelting an AlSi10MnMg series aluminum-silicon cast alloy and then casting it without adding any modifiers. Experimental results show that the tensile strength is 236.3 MPa, the yield strength is 167.9 MPa, and the elongation is 3.10.

[0074] Comparative Example 2

[0075] This embodiment provides a method for preparing an Al-Si cast aluminum alloy. A conventional Al10Sr-containing Sr-containing modifier is used to modify an AlSi10MnMg series aluminum-silicon cast alloy. The Sr addition level is 0.015%. Experimental measurements show a tensile strength of 245.5 MPa, a yield strength of 169.8 MPa, and an elongation of 4.20.

[0076] Comparative Example 3

[0077] This embodiment provides a method for preparing an Al-Si cast aluminum alloy. A conventional Al10Sr-containing Sr-containing modifier is used to modify an AlSi10MnMg series aluminum-silicon cast alloy. The Sr addition level is 0.020%. Experimental results show a tensile strength of 242.5 MPa, a yield strength of 171.3 MPa, and an elongation of 4.30.

[0078] Comparative Example 4

[0079] This embodiment provides a method for preparing an Al-Si cast aluminum alloy. A conventional Al10Sr-containing Sr-containing modifier is used to modify an AlSi10MnMg series aluminum-silicon cast alloy. The Sr addition level is 0.025%. Experimental results show a tensile strength of 246.7 MPa, a yield strength of 170.1 MPa, and an elongation of 4.10.

[0080] Comparative Example 5

[0081] This embodiment provides a method for preparing an Al-Si cast aluminum alloy. A conventional Al10RE-containing RE modifier is used to modify an AlSi10MnMg series aluminum-silicon cast alloy. The RE addition level is 0.10%. Experimental results show a tensile strength of 227.3 MPa, a yield strength of 168.8 MPa, and an elongation of 4.90.

[0082] Comparative Example 6

[0083] This embodiment provides a method for preparing an Al-Si cast aluminum alloy. A conventional Al10RE-containing RE modifier is used to modify an AlSi10MnMg series aluminum-silicon cast alloy. The RE addition level is 0.075%. Experimental results show a tensile strength of 226.4 MPa, a yield strength of 155.3 MPa, and an elongation of 4.05.

[0084] Comparative Example 7

[0085] This embodiment provides a method for preparing an Al-Si cast aluminum alloy. A conventional Al10RE-containing RE modifier is used to modify an AlSi10MnMg series aluminum-silicon cast alloy. The RE addition level is 0.125%. Experimental results show a tensile strength of 219.5 MPa, a yield strength of 157.3 MPa, and an elongation of 4.95.

[0086] Comparative Example 8

[0087] This embodiment provides a method for preparing an Al-Si cast aluminum alloy. A conventional Al10Sr modifier containing Sr and an Al10RE modifier containing RE are used to modify an AlSi10MnMg series aluminum-silicon cast alloy. The Sr addition amount is 0.02%, and the RE addition amount is 0.8%. Experimental measurements show that the resulting alloy has a tensile strength of 243.8 MPa, a yield strength of 177.7 MPa, and an elongation of 4.23.

[0088] Comparative Example 9

[0089] This embodiment provides a method for preparing an Al-Si cast aluminum alloy. A conventional Al10Sr modifier containing Sr and an Al10RE modifier containing RE are used to modify an AlSi10MnMg series aluminum-silicon cast alloy. The Sr addition amount is 0.02%, and the RE addition amount is 0.2%. Experimental measurements show that the resulting alloy has a tensile strength of 257.2 MPa, a yield strength of 177.7 MPa, and an elongation of 5.37.

[0090] Comparative Example 10

[0091] This embodiment provides a method for preparing an Al-Si cast aluminum alloy. A conventional Al10Sr modifier containing Sr and an Al10RE modifier containing RE are used to modify an AlSi10MnMg series aluminum-silicon cast alloy. The Sr addition amount is 0.02%, and the RE addition amount is 0.6%. Experimental measurements show that the resulting alloy has a tensile strength of 255.5 MPa, a yield strength of 173.1 MPa, and an elongation of 4.70.

[0092] Comparative Example 11

[0093] This embodiment provides a method for preparing an Al-Si cast aluminum alloy. Conventional Al10Sr modifiers containing Sr and Al10RE modifiers containing RE are used to modify an AlSi10MnMg series aluminum-silicon cast alloy. The Sr addition amount is 0.02%, and the RE addition amount is 0.02%. Experimental measurements show that the resulting alloys have a tensile strength of 247.7 MPa, a yield strength of 160.1 MPa, and an elongation of 5.20.

[0094]

[0095] In summary, the present invention provides a low-cost, fixed-ratio, high-quality rare earth metal-doped aluminum alloy composite modifier and its preparation method, providing an efficient and economical modifier option for factories and laboratories.

[0096] The composite modifier described above was prepared in the laboratory and subjected to multiple tests. The test results demonstrate that, compared to conventional Sr modifiers, the composite modifier of the present invention can further improve alloy strength, maintain high quality, and be remeltable. The addition of mixed rare earth elements (RE) significantly reduces the cost of the rare earth modifier. Deslagging and degassing performance testing confirm the high quality of the composite modifier, significantly reducing its hydrogen content.

[0097] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Those skilled in the art will readily appreciate that the present invention is susceptible to various modifications and variations. Any modifications, equivalent substitutions, or improvements within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A rare earth metal-doped aluminum alloy composite modification agent, characterized in that, By mass percentage, it includes: Sr 0.85-1.5%； RE 4.85% - 7.15%; The balance is Al, The RE is one or more of La and Ce; The purity of the RE is not less than 99.0%; the proportion of La component is 0.01% - 99.99%, and the proportion of Ce component is 0.01% - 99.99%; The purity of the Sr is not less than 99.0%; The Al is pure aluminum with a purity above 99.7%; The mass fraction ratio of the RE to the Sr is not less than 3.0 and not higher than 9.

0.

2. The rare earth metal-doped aluminum alloy composite modification agent according to claim 1, wherein, When the rare earth metal - doped aluminum alloy composite modifier is used to modify Al - Si cast aluminum alloy, its addition amount is 1.5% - 2.5%.

3. The preparation method of a rare earth metal-doped aluminum alloy composite modification agent as described in claim 1, wherein It includes the following steps: Metal remelting step: Melting the aluminum material and the raw materials containing Sr and RE to obtain a melt; And casting it into uniformly distributed Al - Sr - RE aluminum alloy composite modifier blocks, and the aluminum alloy composite modifier blocks contain Al4(SrRE) phase and Al111RE3 phase; Slagging and degassing step: Carrying out argon rotary spray refining on the aluminum alloy composite modifier blocks, and after the refining is completed, fishing out the surface scum; Degassing effect detection step: Carrying out in - furnace hydrogen measurement and K - mold fracture detection on the product after slagging and degassing; Casting into blocks step: Pre - heating the mold, spraying a mold release agent on the mold surface, and then carrying out casting to obtain the finished product.

4. The preparation method of a rare earth metal-doped aluminum alloy composite modification agent according to claim 1, characterized in that, The specific metal remelting step is first melting the aluminum material completely at a temperature of 750 - 800 °C to obtain a melt, adding a covering agent accounting for 0.02% - 0.03% of the mass of the melt, and adding the raw materials containing Sr and RE to the melt with a bell - jar.

5. The preparation method of a rare earth metal-doped aluminum alloy composite modification agent according to claim 4, characterized in that, The argon rotary spray refining is specifically carried out using an aluminum liquid rotary degasser with a graphite - material rotating head; Before refining, the graphite rotary nozzle needs to be baked above the aluminum liquid for about 15 minutes. After its temperature reaches 300 °C, start the machine for rotary blowing refining. The purity of the graphite is 99.99%; The purity of the used argon is 99.99%, the rotation speed of the rotary blowing head is 150 - 160 r / min, and the rotary blowing refining time is 15 - 20 minutes.

6. The preparation method of a rare earth metal-doped aluminum alloy composite modification agent according to claim 4, characterized in that, The in - furnace hydrogen measurement is to take a spoonful of aluminum liquid, place it in the working cavity of the machine, evacuate for four minutes, then take out the metal block, saw it open from the middle and observe its cross - section. The lowest grade of the cross - section is grade 3, otherwise re - carry out the degassing operation.

7. The preparation method of a rare earth metal-doped aluminum alloy composite modification agent according to claim 4, characterized in that, The K - mold fracture detection uses a special K - mold. Pour the aluminum liquid into it, break it along the concave part after cooling, and observe the fracture situation. If there are no impurities in the fracture, it is qualified, otherwise re - carry out the degassing operation.

8. The preparation method of a rare earth metal-doped aluminum alloy composite modification agent according to claim 4, characterized in that, The pre - heating temperature of the mold is 300 °C.

9. The preparation method of a rare earth metal-doped aluminum alloy composite modification agent according to claim 4, characterized in that, The finished product is a cylindrical sample with a weight of 100 - 1000 g and a diameter of about 10 - 100 mm.

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