A melt composite treatment method for improving mechanical and thermal conductivity properties of cast aluminum alloys

Abstract

The application discloses a melt composite treatment method with the advantages of improving the mechanical properties and heat conduction performance of cast aluminum alloy, which comprises the following steps: carrying out boronization treatment on Al-Si series cast aluminum alloy melt to remove transition elements such as V, Ti and Cr, reduce the solid solubility of the above-mentioned elements in the aluminum matrix, reduce the degree of lattice distortion, and improve the heat conductivity of the alloy; further carrying out heat preservation and liquid transfer treatment on the melt to guarantee the removal effect of the above-mentioned elements; and adding Al-Sr-RE composite modifier with a specific content to modify the eutectic silicon in the alloy. Through the cooperation of the above-mentioned treatment methods, the obtained aluminum alloy has excellent mechanical properties and heat conduction performance, can greatly meet the performance requirements of the market and existing products, and has the significance of wide popularization and application.

Description

Technical Field

[0001] This invention relates to the field of aluminum alloy materials technology, and more specifically, to a melt composite treatment method that improves both the mechanical and thermal conductivity properties of cast aluminum alloys. Background Technology

[0002] Al-Si cast aluminum alloys possess excellent castability, a low coefficient of thermal expansion, and moderate strength and plasticity, making them widely used in the automotive, electronics, and communications industries. With the trend towards lightweighting in new energy vehicles and the integration of structural and functional components in 5G communication systems, the requirements for the strength, toughness, and thermal conductivity of aluminum alloy castings are becoming increasingly stringent. For example, the tensile strength of 5G communication base station heat sinks has increased from 220 MPa to 280 MPa, the elongation from 3% to over 8%, and the thermal conductivity from 120 W / m·K to over 165 W / m·K. Currently, the main method for improving the mechanical properties of alloys is to increase the amount of strengthening elements; however, conventional strengthening elements affect the plasticity and thermal conductivity of the alloy. In recent years, both domestic and international researchers have explored the use of composite additions of trace elements to refine the alloy microstructure, thereby improving the mechanical properties and thermal conductivity of castings.

[0003] CN 113481395 A discloses a composite treatment method for improving the thermal conductivity of cast Al-Si alloys. This method involves sequentially adding AlB, AlLa, AlCe, and AlSr master alloys to Al-Si melt for composite modification treatment. The main modifying element contents are: B: 0.08–0.15%; La: 0.05–0.1%; Ce: 0.3–0.7%; Sr: 0.05%–0.1%. The thermal conductivity of the alloy is increased by more than 15%.

[0004] CN109518041B discloses a composite treatment method for simultaneously improving the thermal conductivity and mechanical properties of die-cast aluminum alloys. This method mainly includes alloy melting, impurity element precipitation and melt purification, and alloy microstructure modification and refinement. Impurity elements are removed by controlling the total amount of boron (B), and composite microstructure refinement and modification are achieved by controlling the content and type of Sr (0.02-0.2%) and RE (0.1-0.3%), ultimately improving the thermal conductivity and mechanical properties of the alloy, with the thermal conductivity increasing by more than 10%.

[0005] The aforementioned patents improve alloy plasticity and mechanical properties by adding various composite modifiers to refine the matrix structure and eutectic silicon. However, CN 113481395 A contains high levels of B, Sr, and RE, resulting in high costs and potential poisoning effects between Sr and B. CN109518041B improves alloy mechanical properties and thermal conductivity by adding Sr and RE in combination, refining the grain size and modifying the eutectic silicon. However, the high RE content also leads to high costs, and grain refinement is not conducive to improving thermal conductivity.

[0006] In view of this, the present invention is proposed. Summary of the Invention

[0007] The purpose of this invention is to provide a melt composite treatment method that improves both the mechanical and thermal conductivity properties of cast aluminum alloys, thereby addressing the aforementioned technical problems.

[0008] This invention is implemented as follows:

[0009] This invention provides a melt composite treatment method that improves both the mechanical and thermal conductivity properties of cast aluminum alloys. The method includes:

[0010] The alloy composition of the cast aluminum alloy melt is adjusted, and after adjusting the temperature, an Al-B master alloy is added to it, followed by heat treatment. After heat treatment, the melt is converted to liquid, the temperature is adjusted and refined, and then a composite modifier is added to the refined melt. After mixing, the melt is cast into ingots.

[0011] The cast aluminum alloy in this invention includes Al-Si based cast aluminum alloys. Optionally, the cast aluminum alloy can be ZL101 aluminum alloy, ZL102 aluminum alloy, ZL107 aluminum alloy or ZL109 aluminum alloy, or other Al-Si based cast aluminum alloys.

[0012] In some preferred embodiments, adjusting the alloy composition of the cast aluminum alloy melt includes: melting the aluminum alloy raw material, measuring the alloy composition, and adjusting it according to the difference between the measured composition and the alloy composition, wherein V, Ti, Cr, Sr, Ce and La do not need to be adjusted.

[0013] In some preferred embodiments, the melt temperature is adjusted to 660–750°C after the alloy composition is adjusted. Optionally, the melt temperature can be adjusted to 660°C, 670°C, 680°C, 690°C, 700°C, 710°C, 720°C, 730°C, 740°C, or 750°C, or any value between 660°C and 750°C.

[0014] In some preferred embodiments, the mass fraction of B in the Al-B master alloy is 2% to 10%. Optionally, the mass fraction of B can be 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10%.

[0015] In some preferred embodiments, B is added to the melt in the Al-B master alloy, and the amount added satisfies the following calculation formula in relation to the contents of V, Zr, and Ti in the melt:

[0016] W (B) = (0.3~0.6)W (V) +(0.1~0.4)W (Ti+Cr) .

[0017] In this invention, the boronizing treatment of the melt is to remove transition elements such as V, Ti, and Cr, reduce the solid solubility of these elements in the aluminum matrix, decrease the degree of lattice distortion, and improve the thermal conductivity of the alloy. When B is added, B will form high-temperature particles MB2 with elements such as V, Ti, and Cr, and will sink to the bottom of the furnace under its own gravity.

[0018] In some preferred embodiments, the heat treatment time is 30 to 60 minutes. Optionally, the heat treatment time can be 30 minutes, 40 minutes, 50 minutes or 60 minutes, or any value within the range of 30 to 60 minutes.

[0019] In this invention, to ensure the removal of transition elements such as V, Ti, and Cr, two additional steps—melt holding and liquid transfer—are added. The holding process provides sufficient time for the reaction and sedimentation of MB2, ensuring its sedimentation efficiency. Subsequently, the clean melt with low B, V, Cr, and Ti content from the upper part is introduced into the holding furnace via liquid transfer. Finally, the small amount of molten aluminum remaining at the bottom of the furnace is skimmed out, achieving separation and purification. This small amount of molten aluminum remaining at the bottom can be used to prepare alloys containing V, Cr, and Ti.

[0020] Meanwhile, by rationally designing the content of B and combining it with liquid transfer treatment, the inventors reduced the content of residual B in the melt, thus preventing B from forming compounds with Sr and affecting the deterioration effect of Sr.

[0021] In some preferred embodiments, the composite modifier includes an Al-Sr-RE composite modifier.

[0022] In some preferred embodiments, the Sr content in the Al-Sr-RE composite modifier is 3%–12%, and the RE content is 4%–15%. Optionally, the Sr content in the Al-Sr-RE composite modifier can be 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, or 12%, and the RE content can be 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, or 15%.

[0023] In some preferred embodiments, the Sr / RE mass ratio in the Al-Sr-RE composite modifier is 0.2 to 3. Optionally, the Sr / RE mass ratio can be 0.2, 0.5, 1, 1.2, 1.6, 2, 2.4, or 3, or any value between 0.2 and 3.

[0024] In some preferred embodiments, RE is one or both of La and Ce.

[0025] In this invention, a composite modifier is used to treat the melt in order to modify the second phase in the alloy, especially eutectic silicon. Sr in the Al-Sr-RE composite modifier is used to lower the nucleation temperature of eutectic silicon, increase its nucleation undercooling and nucleation efficiency, and promote the transformation of the eutectic silicon morphology to a fibrous structure. The addition of RE adsorbs at the nucleation front of the eutectic silicon, further improving the nucleation undercooling and nucleation efficiency, and utilizing its ratio with the atomic radius of Si, promotes the twinning transformation of the eutectic silicon, further refining its size and improving its sphericity. On the other hand, the reduction in the eutectic silicon nucleation temperature increases the growth temperature range of primary α-Al, coarsens the grains, and is beneficial for improving the thermal conductivity of the alloy.

[0026] To improve the efficiency of composite modification, the composite modifier of this invention is added in the form of an Al-Sr-RE master alloy, with the two elements doped together as Al4(Sr) RE ) phase and Al 11 (RE Sr The presence of )3 reduces the loss of Sr and its tendency to absorb hydrogen, thereby improving the stability and yield of Sr.

[0027] In some preferred embodiments, when the Al-Sr-RE composite modifier is added to the melt, the amount of Sr and RE added is 0.02% to 0.08% of the mass of the composite modifier. Optionally, the total amount of Sr and RE added is 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, or 0.08% of the melt mass.

[0028] To enhance the role of rare earth elements in complex metamorphism, this application strictly controls the types and contents of rare earth phases. Ce and La are the cheapest rare earth elements; their contents are set between 0.02% and 0.06%, which ensures the activity of rare earth elements, reduces the formation temperature of rare earth phases, and also helps control costs.

[0029] In this invention, the inventors adjust the ratio of Al-Sr-RE, the Sr / RE mass ratio, and the total amount of (Sr+RE) to adapt to alloys with different Si contents and other alloying element contents, thereby obtaining high-quality aluminum alloy castings with both mechanical and thermal conductivity properties.

[0030] In some preferred embodiments, the ingot casting process includes: allowing the melt to stand, removing slag, adding a covering agent to its surface, and then introducing it into the casting equipment after degassing and impurity removal to complete the ingot casting.

[0031] Specifically, the ingot casting process includes: letting the melt stand for 25-40 minutes, removing slag, and then sprinkling a layer of covering agent on the surface of the melt; the melt is then introduced into a holding furnace through a flow channel, an online degassing box, and a ceramic filter plate before being directly supplied to the casting equipment or foundry to form the ingot.

[0032] Optionally, the settling time can be 25 min, 28 min, 30 min, 32 min, 35 min or 40 min, or any value between 25 and 40 min.

[0033] The present invention has the following beneficial effects:

[0034] This invention removes transition elements such as V, Ti, and Cr by borizing the Al-Si based cast aluminum alloy melt, reducing their solid solubility in the aluminum matrix, decreasing lattice distortion, and improving the alloy's thermal conductivity. Further, the removal of these elements is ensured through heat treatment and liquidization. Finally, a specific amount of Al-Sr-RE composite modifier is added to modify the eutectic silicon in the alloy. This combination of treatments results in an aluminum alloy with excellent mechanical and thermal conductivity properties, significantly meeting market and existing product material performance requirements, and thus possessing broad applicability. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0036] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0037] The materials used in the embodiments of the present invention are alloys such as ZL101, ZL102, ZL107, and ZL109 from GB / T 1173-2013 "Cast Aluminum Alloys".

[0038] Example 1

[0039] This embodiment provides a melt composite treatment method that improves both the mechanical and thermal conductivity properties of cast aluminum alloys. The specific operation steps are as follows:

[0040] S1. Alloy melting. The ZL101 aluminum alloy raw material (excluding Mg) is put into the furnace for melting. After the raw material is completely melted, a sample is taken to test the alloy composition.

[0041] S2. Alloy composition adjustment. Adjust the alloy composition according to the difference between the measured composition and the alloy composition. V, Ti, Cr and Sr, Ce, La do not need to be adjusted.

[0042] S3. Boring and heat preservation treatment. After the composition is qualified, adjust the melt temperature to 720℃; according to the calculation formula: W (B) = (0.3~0.6)W (V) +(0.1~0.4)W (Ti+Cr) Add 0.6% Al-3B master alloy and stir the melt to ensure that the master alloy is completely dissolved, then hold at the temperature for 40 minutes.

[0043] S4. Liquid Transfer and Refining. After the holding period, the liquid is transferred to the holding furnace and industrial pure magnesium is added; the temperature is adjusted to 730℃, and a refining agent is introduced using high-purity inert gas as a carrier.

[0044] S5. Composite Modification. Immediately after refining, add 0.4% Al-6Sr-13RE composite modifier by mass of the melt and stir the melt to promote the dissolution of the modifier.

[0045] S6. Ingot casting. After the melt has been allowed to stand for 25 minutes, the slag is removed, and then a layer of covering agent is sprinkled on the surface of the aluminum melt. The melt is then introduced into a holding furnace through an online degassing box and a ceramic filter plate before being directly supplied to the casting equipment or foundry to form ingots.

[0046] Example 2

[0047] This embodiment provides a melt composite treatment method that improves both the mechanical and thermal conductivity properties of cast aluminum alloys. The specific operation steps are as follows:

[0048] S1. Alloy melting. The ZL102 aluminum alloy raw material is put into the furnace for melting. After the raw material is completely melted, a sample is taken to test the alloy composition.

[0049] S2. Alloy composition adjustment. Adjust the alloy composition according to the difference between the measured composition and the alloy composition. V, Ti, Cr and Sr, Ce, La do not need to be adjusted.

[0050] S3. Boring and heat preservation treatment. After the composition is qualified, adjust the melt temperature to 700℃; according to the calculation formula: W (B) = (0.3~0.6)W (V) +(0.1~0.4)W (Ti+Cr) Add 0.5% Al-4B master alloy and stir the melt to ensure that the master alloy is completely dissolved, then hold at the temperature for 30 minutes.

[0051] S4. Liquid Transfer and Refining. After the heat preservation is completed, the liquid is transferred to the heat preservation furnace; the temperature is adjusted to 720℃, and a refining agent is introduced using high-purity inert gas as a carrier.

[0052] S5. Composite Modification. Immediately after refining, add 1% Al-3Sr-5RE composite modifier by mass of the melt and stir the melt to promote the dissolution of the composite modifier.

[0053] S6. Ingot casting. After the melt has been allowed to stand for 35 minutes, the slag is removed, and then a layer of covering agent is sprinkled on the surface of the aluminum melt. The melt is then introduced into a holding furnace through an online degassing box and a ceramic filter plate before being directly supplied to the casting equipment or foundry to form ingots.

[0054] Example 3

[0055] This embodiment provides a melt composite treatment method that improves both the mechanical and thermal conductivity properties of cast aluminum alloys. The specific operation steps are as follows:

[0056] S1. Alloy melting. The Al-Si cast aluminum alloy raw material is put into the furnace for melting. After the raw material is completely melted, a sample is taken to test the alloy composition.

[0057] S2. Alloy composition adjustment. Adjust the alloy composition according to the difference between the measured composition and the alloy composition. V, Ti, Cr and Sr, Ce, La do not need to be adjusted.

[0058] S3. Boring and heat preservation treatment. After the composition is qualified, adjust the melt temperature to 750℃; according to the calculation formula: W (B) = (0.3~0.6)W (V) +(0.1~0.4)W (Ti+Cr) Add 0.3% Al-10B master alloy and stir the melt to ensure that the master alloy is completely dissolved, then hold at the temperature for 60 minutes.

[0059] S4. Liquid Transfer and Refining. After the holding period, the liquid is transferred to the holding furnace; the temperature is adjusted to 700℃, and a refining agent is introduced using high-purity inert gas as a carrier.

[0060] S5. Composite Modification. Immediately after refining, add 0.3% Al-6Sr-10RE composite modifier by mass of the melt and stir the melt to promote the dissolution of the modifier.

[0061] S6. Ingot casting. After the melt has been allowed to stand for 30 minutes, the slag is removed, and then a layer of covering agent is sprinkled on the surface of the aluminum melt. The melt is then introduced into a holding furnace through an online degassing box and a ceramic filter plate, and then directly supplied to the casting equipment or foundry to form ingots.

[0062] Example 4

[0063] This embodiment provides a melt composite treatment method that improves both the mechanical and thermal conductivity properties of cast aluminum alloys. The specific operation steps are as follows:

[0064] S1. Alloy melting. The Al-Si cast aluminum alloy raw material is put into the furnace for melting. After the raw material is completely melted, a sample is taken to test the alloy composition.

[0065] S2. Alloy composition adjustment. Adjust the alloy composition according to the difference between the measured composition and the alloy composition. V, Ti, Cr and Sr, Ce, La do not need to be adjusted.

[0066] S3. Boring and heat preservation treatment. After the composition is qualified, adjust the melt temperature to 660℃; according to the calculation formula: W (B) = (0.3~0.6)W (V) +(0.1~0.4)W (Ti+Cr) Add 1% Al-2B master alloy and stir the melt to ensure that the master alloy is completely dissolved, then hold at the temperature for 45 minutes.

[0067] S4. Liquid Transfer and Refining. After the heat preservation is completed, the liquid is transferred to the heat preservation furnace; the temperature is adjusted to 720℃, and a refining agent is introduced using high-purity inert gas as a carrier.

[0068] S5. Composite Modification. Immediately after refining, add 0.3% Al-10Sr-11RE composite modifier by mass of the melt and stir the melt to promote the dissolution of the modifier.

[0069] S6. Ingot casting. After the melt has been allowed to stand for 40 minutes, the slag is removed, and then a layer of covering agent is sprinkled on the surface of the aluminum melt. The melt is then introduced into a holding furnace through an online degassing box and a ceramic filter plate, and then directly supplied to the casting equipment or foundry to form ingots.

[0070] Comparative Example 1:

[0071] Compared to Example 1, no boronizing treatment was performed.

[0072] Comparative Example 2:

[0073] Compared to Example 2, the boronizing treatment did not involve melt holding and standing.

[0074] Comparative Example 3:

[0075] Compared to Example 3, the boronizing treatment did not involve liquid transfer.

[0076] Comparative Example 4:

[0077] Compared to Example 4, Al-10Sr was used instead of Al-10Sr-11RE.

[0078] Comparative Example 5

[0079] Compared to Example 1, the total amount of (Sr+RE) in the composite modifier used is 0.15%, of which Sr is 0.05% and RE is 0.1%.

[0080] Comparative Example 6

[0081] Compared to Example 2, the mass fraction of B during the borylation treatment was 0.05%.

[0082] The chemical composition of the alloys before and after composite treatment in Examples 1-4 is shown in Table 1.

[0083] Table 1. Chemical composition (wt.%) of the alloy before and after composite treatment

[0084]

[0085] Experimental Example

[0086] The ingots prepared in Examples 1-4 and Comparative Examples 1-6 were subjected to tensile mechanical properties (including tensile strength and elongation) and thermal conductivity tests, respectively.

[0087] The tensile mechanical properties and thermal conductivity of Examples 1-4 and Comparative Examples 1-6 are shown in Table 2.

[0088] Table 2 Thermal conductivity of tissues from Examples 1-4 and Comparative Examples 1-6

[0089]

[0090] As can be seen from the data in Table 2, the mechanical properties of the alloy were not significantly affected after boronizing, but the thermal conductivity increased by about 10%. After appropriate melt holding and liquid transfer treatment following boronizing, the elongation and thermal conductivity of the alloy both showed significant improvement. Replacing the Al-Sr master alloy with Al-Sr-RE significantly improved the elongation and thermal conductivity of the alloy. As can be seen from Comparative Examples 5 and 6, adjusting the total amount of B and (Sr+RE) in the composite modifier can also affect the tensile mechanical properties and thermal conductivity of Al-Si cast aluminum alloys to some extent.

[0091] In summary, the composite treatment of boronizing, melt holding, liquid transfer, and composite modification in this invention can significantly improve the electrical and thermal conductivity of the alloy, which is of great significance for expanding the application fields of the alloy.

[0092] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A melt composite treatment method that improves both the mechanical and thermal conductivity properties of cast aluminum alloys, characterized in that, include: An Al-B master alloy is added to the melt of cast aluminum alloy, and then it is heat-treated. After the heat preservation is completed, the melt is converted into liquid and refined. Then, Al-Sr-RE composite modifier is added to the refined melt, mixed well, and then cast into ingots. The cast aluminum alloy is ZL101 aluminum alloy, ZL102 aluminum alloy, ZL107 aluminum alloy or ZL109 aluminum alloy. In the Al-B master alloy, the amount of B added to the melt is calculated according to the following formula, which is related to the content of V, Zr, and Ti in the melt: IN (B) =(0.3~0.6)W (V) +(0.1~0.4)W （Ti+Cr） ; When the Al-Sr-RE composite modifier is added to the melt, the total amount of Sr and RE added is 0.02% to 0.08% of the melt mass.

2. The melt composite processing method according to claim 1, characterized in that, The mass fraction of B in the Al-B master alloy is 2% to 10%.

3. The melt composite processing method according to claim 1, characterized in that, The heat preservation treatment time is 30~60 min.

4. The melt composite processing method according to claim 1, characterized in that, The Al-Sr-RE composite modifier contains 3% to 12% Sr and 4% to 15% RE.

5. The melt composite processing method according to claim 4, characterized in that, The Sr / RE mass ratio in the Al-Sr-RE composite modifier is 0.2~3.

6. The melt composite processing method according to claim 5, characterized in that, The RE is one or both of La and Ce.

7. The melt composite processing method according to claim 1, characterized in that, The ingot casting process includes: removing slag from the melt after it has been allowed to stand, adding a covering agent to its surface, and then introducing it into the casting equipment after degassing and impurity removal to complete the ingot casting. The settling time is 25-40 minutes.

8. The melt composite processing method according to any one of claims 1-7, characterized in that, Before adding the Al-B master alloy to the melt, the alloy composition and temperature of the melt are adjusted.

9. The melt composite processing method according to claim 8, characterized in that, Before adding the Al-B master alloy to the melt, adjust the melt temperature to 660~750℃.

10. The melt composite processing method according to claim 9, characterized in that, Before refining, the temperature of the melt after liquid conversion is adjusted.

11. The melt composite processing method according to claim 10, characterized in that, Before refining, adjust the melt temperature to 700~750℃.

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