High-strength high-thermal-conductivity Al-La-Cu-based aluminum alloy and preparation method thereof

Abstract

The application belongs to the technical field of casting aluminum alloy, and discloses a high-strength and high-thermal-conductivity Al-La-Cu-based aluminum alloy and a preparation method thereof.The high-strength and high-thermal-conductivity Al-La-Cu-based aluminum alloy is composed of the following components in percentage by weight: La: 9-11 %; Cu: 2.5-3.5 %; impurity elements: ≤0.20 %; and the balance of Al. The method comprises the following steps: 1) determining the components and contents of a first precursor alloy and a second precursor alloy according to the target alloy Al-La-Cu-based aluminum alloy; the first precursor alloy is an Al-La alloy; the second precursor alloy is an Al-Cu alloy; the raw materials of the two precursor alloys are respectively melted to obtain two melts; 2) mixing the two melts after cooling to 5-20 ℃ above the liquidus line, and extrusion casting to obtain the high-strength and high-thermal-conductivity Al-La-Cu-based aluminum alloy. The aluminum alloy has high strength and good thermal conductivity. The method is simple.

Description

Technical Field

[0001] This invention belongs to the field of cast aluminum alloy technology, specifically relating to a high-strength, high-thermal-conductivity Al-La-Cu-based aluminum alloy and its preparation method. Background Technology

[0002] With the increasing demand for lightweight and efficient thermal management in automobiles, aluminum alloys, due to their low density, high specific strength, good thermal conductivity, and excellent casting properties, have broad application prospects in engine cylinder heads, cylinder blocks, and heat dissipation structural components. However, engines and related hot-end components are often exposed to high-temperature environments during service, with some areas reaching temperatures above 200°C. Traditional cast aluminum alloys are prone to problems such as decreased strength, insufficient structural stability, and inadequate thermal conductivity to meet application requirements under these conditions.

[0003] Rare earth aluminum alloys, especially Al-RE based alloys, typically exhibit high eutectic temperatures, good melt flowability, and high second-phase thermal stability due to the low solid solubility and slow diffusion rate of rare earth elements in the aluminum matrix. These characteristics make them highly promising for applications in heat-resistant cast aluminum alloys. Among these, light rare earth elements such as La and Ce are relatively abundant and inexpensive, and can form thermally stable rare earth intermetallic compound phases with Al, which is beneficial for improving the microstructure stability of the alloy at high temperatures.

[0004] However, Al-RE based rare earth aluminum alloys also have certain shortcomings. While single Al-RE alloys possess good heat resistance and casting fluidity, their room temperature strength is typically low, making it difficult to directly meet the high strength requirements of load-bearing structural components such as engine cylinder heads and blocks. Furthermore, under ordinary casting conditions, the rare earth eutectic phases in Al-RE alloys tend to exhibit large sizes and uneven distribution, hindering the synergistic improvement of alloy strength, plasticity, and thermal conductivity. Therefore, further improvements in the microstructure and overall properties of Al-RE based rare earth aluminum alloys are needed through alloy composition design and process control.

[0005] To address the above problems, existing technologies have proposed several solutions, but they still have certain limitations.

[0006] Chinese patent CN110373574A discloses a near-eutectic high-strength heat-resistant Al-Ce aluminum alloy and its preparation method. It uses Ce as the main rare earth element and incorporates multiple alloying elements such as Fe, Mg, Si, Cu, Co, B, Ti, V, Cr, Mn, and Ni to improve the alloy's room-temperature and high-temperature strength. This method demonstrates that based on the Al-RE eutectic system and combined with multi-element composite alloying, the heat resistance of rare earth aluminum alloys can be effectively improved. However, the alloy composition system is relatively complex, and performance improvement mainly relies on the synergistic strengthening of multiple alloying elements. The introduction of numerous alloying elements also increases the difficulty of composition control and solidification structure regulation.

[0007] Chinese patent application CN119800164A discloses a high-elongation, high-thermal-conductivity TiB2-Al-Ce-La-Fe alloy, its preparation method, and its applications. This method introduces TiB2 granular phases into the Al-Ce-La-Fe alloy by adding an Al-TiB2 master alloy, thereby improving the alloy microstructure and increasing thermal conductivity and elongation. This method demonstrates that microstructure refinement has a positive effect on improving the overall performance of Al-RE-based rare-earth aluminum alloys. However, the external particle refinement route has high requirements for particle size, dispersion uniformity, and interfacial bonding state, and the process stability and microstructure uniformity are easily affected by the particle introduction method.

[0008] In summary, existing Al-RE-based rare earth aluminum alloys primarily improve their properties through multi-element composite alloying, composite rare earth strengthening, or external particle refinement. While these methods have achieved some success, they still suffer from problems such as complex composition systems, high raw material costs, or reliance on external particles for microstructure refinement. Therefore, it is necessary to develop a rare earth aluminum alloy preparation method that simplifies composition and synergistically improves strength and thermal conductivity, based on a low-cost light rare earth alloy system, by introducing appropriate strengthening elements and combining solidification forming process control. Summary of the Invention

[0009] To overcome the shortcomings of existing technologies, the present invention aims to provide a high-strength, high-thermal-conductivity Al-La-Cu-based aluminum alloy and its preparation method. The present invention uses La as the main rare-earth element and Cu as a strengthening and microstructure-regulating element to construct an Al-La-Cu-based aluminum alloy system. Furthermore, by synergistically controlling the alloy's solidification microstructure and casting density through controlled diffusion solidification and extrusion casting, a cast rare-earth aluminum alloy with both high strength and good thermal conductivity is obtained.

[0010] The objective of this invention is achieved through the following technical solution:

[0011] A high-strength, high-thermal-conductivity Al-La-Cu-based aluminum alloy, composed of the following components by weight percentage:

[0012] La: 9-11 wt.%;

[0013] Cu: 2.5-3.5 wt.%;

[0014] Impurity elements: ≤0.20 wt.%;

[0015] The balance is Al.

[0016] The preparation method of the high-strength, high-thermal-conductivity Al-La-Cu-based aluminum alloy includes the following steps:

[0017] 1) Precursor alloy smelting: Based on the target alloy Al-La-Cu-based aluminum alloy, determine the composition and content of the first and second precursor alloys, and the mass ratio of the first and second precursor alloys is (2.5~3.5):1; the first precursor alloy is an Al-La alloy, which is obtained by melting pure aluminum and an aluminum-lanthanum intermediate alloy; the second precursor alloy is an Al-Cu alloy, which is obtained by melting pure aluminum and an aluminum-copper intermediate alloy; melt the raw materials of the first precursor alloy and melt the raw materials of the second precursor alloy to obtain the first precursor alloy melt and the second precursor alloy melt respectively;

[0018] 2) Cool the first precursor alloy melt to 5-20°C above the first precursor alloy liquidus line, and cool the second precursor alloy melt to 5-20°C above the second precursor alloy liquidus line; then mix the first precursor alloy melt and the second precursor alloy melt evenly and add them to the preheated extrusion casting mold cavity.

[0019] 3) Apply pressure to the mixed melt entering the mold cavity to solidify it under pressure and obtain a high-strength, high-thermal-conductivity Al-La-Cu-based aluminum alloy.

[0020] Step 1) The two melts are refined and purified separately; the refining and purification process refers to adding refining agent, stirring and removing slag, wherein the refining agent is a mixture of YT-J-1 and YT-D-4 in a 1:1 mass ratio.

[0021] In step 1), the melting temperature of the raw material of the first precursor alloy is 750-800℃, and the melting temperature of the raw material of the second precursor alloy is 750-800℃.

[0022] The aluminum-lanthanum master alloy is Al-20La master alloy; the aluminum-copper master alloy is Al-50Cu master alloy.

[0023] In step 2), when the target alloy contains 10 wt.% La and 3 wt.% Cu, the first precursor alloy melt and the second precursor alloy melt are cooled to 665–680 °C and 632–647 °C, respectively.

[0024] The mass ratio of the first precursor alloy melt to the second precursor alloy melt is (2.5~3.5):1, preferably 3:1.

[0025] The preheating temperature is 180~220℃.

[0026] Step 3) Conditions for extrusion casting: extrusion pressure is 60~70 MPa, and holding time is 10~20 s.

[0027] The principle of this invention:

[0028] This invention is based on Al-La-Cu-based rare-earth aluminum alloys. La has low solid solubility in the Al matrix, enabling it to form thermally stable Al-La intermetallic compound phases. These rare-earth phases exhibit good high-temperature stability, which is beneficial for improving the alloy's heat resistance and casting performance. Simultaneously, due to the low solid solubility of La in the Al matrix, its influence on Al matrix lattice distortion and electron scattering is relatively limited, which helps maintain the alloy's good thermal conductivity.

[0029] However, the room temperature strength of a single Al-La alloy is relatively limited, making it difficult to directly meet the requirements of high-strength structural components. This invention introduces an appropriate amount of Cu into the Al-La alloy. Cu can participate in the solidification process of Al-La-based alloys, promoting the formation of Cu-containing eutectic structures or Al-La-Cu related ternary phases, thereby altering the alloy's solidification path and second-phase morphology, and improving the alloy's strengthening effect. Controlling the Cu content within the range of 2.5–3.5 wt.% is beneficial in two ways: firstly, it facilitates the formation of an appropriate amount of Cu-containing strengthening phase, improving alloy strength; secondly, it avoids excessive Cu content leading to an overabundance of Cu-rich phases or brittle eutectic structures, which could result in decreased plasticity and impaired thermal conductivity.

[0030] This invention employs a combined manufacturing method of controlled diffusion solidification and extrusion casting. During controlled diffusion solidification, a first precursor alloy melt with different compositions and temperatures is poured into a second precursor alloy melt for mixing. Rapid heat exchange and solute diffusion occur between the two melts during mixing, resulting in temperature and compositional fluctuations within the mixed melt. Due to the different rates of thermal and solute diffusion, localized undercooling can occur, promoting multi-point nucleation and refining the eutectic structure in the Al-La-Cu alloy while improving the distribution of the second phase.

[0031] The two melts are mixed and rapidly stirred before being quickly poured into a preheated extrusion casting mold cavity. The mixed melt then solidifies under the pressure of extrusion casting. Extrusion casting improves the feeding capacity of the alloy during solidification, reduces casting defects such as shrinkage cavities and porosity, and increases the density of the casting. Controlled diffusion solidification primarily promotes nucleation and microstructure refinement through melt mixing, while extrusion casting primarily improves casting densification through pressure solidification. The synergistic effect of these two processes is beneficial for obtaining Al-La-Cu-based rare earth aluminum alloy castings with fine microstructure, uniform second-phase distribution, and high casting density.

[0032] The present invention has the following advantages and beneficial effects:

[0033] (1) The alloy system of the present invention is relatively simple. La is used as the main rare earth element and Cu is used as the strengthening and microstructure control element, avoiding reliance on multiple expensive rare earth elements or complex multi-element composite strengthening, resulting in lower raw material costs and easier composition control.

[0034] (2) The rare earth aluminum alloy of the present invention has high strength. Cu element can participate in the formation of Cu-containing second phase or Al-La-Cu related eutectic structure, which improves the strengthening effect of the alloy; controlled diffusion solidification further refines the eutectic structure, which is beneficial to improving the mechanical properties of the alloy.

[0035] (3) The rare earth aluminum alloy of the present invention has good thermal conductivity. The contents of La and Cu are reasonably controlled to avoid excessive alloying elements dissolving in the Al matrix and causing serious lattice distortion. At the same time, the overall performance of the alloy is improved by refining the microstructure and regulating the distribution of the second phase.

[0036] (4) The manufacturing method of the present invention can improve the microstructure and density of castings. Controlled diffusion solidification can promote nucleation and refine the microstructure, while squeeze casting can improve feeding capacity and reduce porosity and shrinkage defects. The synergy of the two is beneficial to obtaining rare earth aluminum alloy castings with uniform microstructure and high density. Attached Figure Description

[0037] Figure 1 The image shows the SEM microstructure of the ordinary cast Al-10La alloy in Comparative Example 1.

[0038] Figure 2 The image shows the SEM microstructure of the ordinary cast Al-10La-3Cu alloy in Comparative Example 2.

[0039] Figure 3 The image shows the SEM microstructure of the Al-10La-3Cu alloy prepared by controlled diffusion solidification and extrusion casting in Example 1.

[0040] Figure 4 Here is a SEM microstructure of the extrusion-cast Al-10La alloy in Comparative Example 3;

[0041] Figure 5 The image shows the SEM microstructure of the extrusion-cast Al-10La-3Cu alloy in Comparative Example 4. Detailed Implementation

[0042] The present invention will be described in further detail below with reference to specific embodiments and comparative examples, but the implementation of the present invention is not limited thereto. In the following embodiments and comparative examples, the alloy composition is expressed as a percentage by mass.

[0043] The raw materials used in this invention are pure Al, Al-20La master alloy, and Al-50Cu master alloy. After cutting and polishing, the resulting alloys are observed using a scanning electron microscope to observe their microstructure, and the microstructure and comprehensive properties of the alloys are evaluated by combining XRD phase analysis, room temperature tensile property testing, and thermal conductivity testing.

[0044] Comparative Example 1

[0045] To illustrate the microstructure characteristics of Al-La binary rare earth aluminum alloys under ordinary casting conditions, an Al-10La alloy prepared by ordinary casting was used as Comparative Example 1. The alloy composition of this comparative example was: La 10 wt.%, with the balance being Al.

[0046] The preparation method of this comparative aluminum alloy includes the following steps:

[0047] 1) Preheating: Place the metal mold in a 200℃ constant temperature chamber for preheating;

[0048] 2) According to the target alloy composition, weigh pure Al and Al-20La master alloy, place them in a crucible, and melt them in a resistance furnace at a high temperature of 800-850℃. After melting, stir for 2 minutes to promote homogenization. After the melt cools to the casting temperature of 680-720℃, add refining agent (YT-J-1 and YT-D-4 in a mass ratio of 1:1, 1% of the melt mass) to purify and stir to remove slag.

[0049] 3) After the temperature of the alloy melt stabilizes, pour the alloy melt into the preheated metal mold at a casting temperature of 680-720℃. After cooling and solidification, Al-10La alloy ingots are obtained.

[0050] Figure 1 This is a SEM microstructure image of the ordinary cast Al-10La alloy obtained in this comparative example. Figure 1 It can be seen that the alloy microstructure is mainly composed of a dark gray α-Al matrix and a bright white Al-La eutectic phase. The bright white second phase is mostly distributed in the form of elongated strips, plates, or lamellar structures, with some regions containing relatively coarse eutectic phases, and the orientation and size of the second phase vary in different regions.

[0051] Comparative Example 2

[0052] To illustrate the effect of Cu addition on the microstructure of Al-La based rare earth aluminum alloys under ordinary casting conditions, an Al-10La-3Cu alloy prepared by ordinary casting was used as Comparative Example 2. The alloy composition of this comparative example was: La 10 wt.%, Cu 3 wt.%, with the balance being Al.

[0053] The preparation method of this comparative aluminum alloy includes the following steps:

[0054] 1) Preheating: Place the metal mold in a 200℃ constant temperature chamber for preheating;

[0055] 2) According to the target alloy composition, weigh pure Al, Al-20La master alloy and Al-50Cu master alloy, place them in a crucible, and melt them in a resistance furnace at a high temperature of 800-850℃. After melting, stir for 2 minutes to promote homogenization. After the melt cools to the casting temperature of 680-720℃, add refining agent to purify and stir to remove slag.

[0056] 3) After the temperature of the alloy melt stabilizes, pour the alloy melt into the preheated metal mold at a casting temperature of 680-720℃. After cooling and solidification, obtain the Al-10La-3Cu alloy ingot.

[0057] Figure 2 This is a SEM microstructure image of the conventionally cast Al-10La-3Cu alloy obtained in this comparative example. Figure 2 It can be seen that after adding Cu, the amount of bright white second phase in the alloy increases significantly, and more lamellar and strip-shaped eutectic structures appear in the microstructure. In some areas, relatively coarse bright white phases or eutectic clusters can be observed.

[0058] Example 1

[0059] To illustrate the effectiveness of this invention, an Al-10La-3Cu alloy prepared by controlled diffusion solidification and extrusion casting is used as Example 1. The alloy composition of this example is: La 10 wt.%, Cu 3 wt.%, impurity elements ≤0.20 wt.%, and the balance being Al.

[0060] The preparation method of the high-strength, high-thermal-conductivity Al-La-Cu-based aluminum alloy in this embodiment includes the following steps:

[0061] 1) Preheating: Preheat the extrusion casting mold to 200℃;

[0062] 2) Based on the target Al-10La-3Cu alloy composition, determine the composition and mass ratio of the first and second precursor alloys, and calculate the raw material usage of the two precursor alloys; wherein, the first precursor alloy is an Al-xLa alloy, the second precursor alloy is an Al-xCu alloy, and x is determined according to the target alloy composition and the mass ratio of the two precursor alloys. In this embodiment, the mass ratio of the first precursor alloy to the second precursor alloy is 3:1, and pure Al, Al-20La master alloy, and Al-50Cu master alloy are weighed;

[0063] 3) The two precursor alloys are placed in two crucibles and melted in an electric resistance furnace at temperatures of 750-800℃ to obtain a first precursor alloy melt and a second precursor alloy melt; wherein the first precursor alloy melt is a melt with a high melting point and a large mass, and the second precursor alloy melt is a melt with a low melting point and a small mass.

[0064] 4) Cool the two melts to 5–20 °C above their respective liquidus lines; in this embodiment, the liquidus temperatures of the first precursor alloy and the second precursor alloy are 660 °C and 627 °C, respectively. The first precursor alloy melt is cooled to 665–680 °C (e.g., 672 °C); the second precursor alloy melt is cooled to 632–647 °C (e.g., 640 °C).

[0065] 5) The first precursor alloy melt is poured into the second precursor alloy melt for mixing, wherein the mass ratio of the first precursor alloy melt to the second precursor alloy melt is 3:1;

[0066] 6) Quickly stir and mix the molten mixture, then rapidly pour the molten mixture into the preheated (200℃) extrusion casting mold cavity;

[0067] 7) Apply pressure to the mixed melt entering the mold cavity to solidify it under pressure and obtain a high-strength, high-thermal-conductivity Al-La-Cu-based aluminum alloy; wherein the extrusion pressure is 65 MPa and the holding time is 15 s.

[0068] Figure 3 This is a SEM microstructure image of the Al-10La-3Cu alloy prepared by controlled diffusion solidification and extrusion casting in this embodiment. Figure 3 It can be seen that the alloy microstructure contains a dark gray α-Al matrix, a bright white lamellar eutectic structure, and a small amount of relatively coarse second phase. The bright white eutectic structure is generally distributed in lamellar or short strip shapes, with smaller spacing between the second phases in local areas, and the microstructure is relatively continuous.

[0069] In this embodiment, the calculation of each component, raw material, and content in step 2) is as follows: Taking 100g of Al-10La-3Cu target alloy as an example, the mass of La in the target alloy is 100g × 10% = 10g, the mass of Cu is 100g × 3% = 3g, and the mass of Al is 87g. Since the mass ratio of the first precursor alloy to the second precursor alloy is 3:1, the mass of the first precursor alloy is 100g × 3 / 4 = 75g, and the mass of the second precursor alloy is 100g × 1 / 4 = 25g. The first precursor alloy is an Al-xLa alloy, and all La is provided by the Al-20La master alloy. Therefore, the amount of Al-20La master alloy used is 10g ÷ 20% = 50g; this 50g Al-20La master alloy contains 10g of La and 40g of Al. To achieve a total mass of 75g for the first precursor alloy, 75g - 50g = 25g of pure Al needs to be added. Therefore, the first precursor alloy is prepared by combining 50g of Al-20La master alloy and 25g of pure Al, with a composition of Al-13.33La. The second precursor alloy is an Al-xCu alloy, with all Cu provided by the Al-50Cu master alloy. Therefore, the amount of Al-50Cu master alloy used is 3g ÷ 50% = 6g; this 6g Al-50Cu master alloy contains 3g Cu and 3g Al. To achieve a total mass of 25g for the second precursor alloy, 25g - 6g = 19g of pure Al needs to be added. Therefore, the second precursor alloy is prepared by combining 6g of Al-50Cu master alloy and 19g of pure Al, with a composition of Al-12Cu. After mixing the two precursor alloys, the total mass of Al is 65g + 22g = 87g, the mass of La is 10g, and the mass of Cu is 3g. Therefore, the overall composition is Al-10La-3Cu.

[0070] Example 2

[0071] To further illustrate the effectiveness of this invention within its compositional range, an Al-10.5La-2.7Cu alloy prepared by controlled diffusion solidification and extrusion casting was used as Example 2. The alloy composition of this example was: La 10.5 wt.%, Cu 2.7 wt.%, impurity elements ≤0.20 wt.%, and the balance being Al.

[0072] The preparation method in this embodiment is the same as in Embodiment 1.

[0073] Comparative Example 3

[0074] To illustrate the effect of squeeze casting alone on the microstructure of Al-La alloys, an Al-10La alloy prepared by squeeze casting was used as Comparative Example 3. The alloy composition of this comparative example was: La 10 wt.%, with the balance being Al.

[0075] The preparation method of this comparative aluminum alloy includes the following steps:

[0076] 1) Preheating: Preheat the extrusion casting mold to 200℃;

[0077] 2) According to the target alloy composition, weigh pure Al and Al-20La master alloy, place them in a crucible, and melt them in a resistance furnace at a high temperature of 800-850℃. After melting, stir for 2 minutes to promote homogenization. After the melt cools to the casting temperature of 680-720℃, add refining agent to purify and stir to remove slag.

[0078] 3) After the alloy melt temperature stabilizes, pour the alloy melt into the preheated extrusion casting mold cavity at a casting temperature of 680-720℃. Apply pressure to the melt entering the mold cavity to solidify it under pressure and obtain the extrusion cast Al-10La alloy product. The extrusion pressure is 65 MPa and the holding time is 15 s.

[0079] Figure 4 This is a SEM microstructure image of the extruded Al-10La alloy obtained in this comparative example. Figure 4 It can be seen that the bright white Al-La eutectic phase in the alloy is distributed in a relatively fine lamellar or short strip shape, with small interlamellar spacing in some areas.

[0080] Comparative Example 4

[0081] To illustrate the microstructure characteristics of Cu alloying combined with squeeze casting without controlled diffusion solidification, an Al-10La-3Cu alloy prepared by squeeze casting was used as Comparative Example 4. The alloy composition of this comparative example was: La 10 wt.%, Cu 3 wt.%, with the balance being Al.

[0082] The preparation method of this comparative example includes the following steps:

[0083] 1) Preheating: Preheat the extrusion casting mold to 200℃;

[0084] 2) According to the target alloy composition, weigh pure Al, Al-20La master alloy and Al-50Cu master alloy, place them in a crucible, and melt them in a resistance furnace at a high temperature of 800-850℃. After melting, stir for 2 minutes to promote homogenization. After the melt cools to the casting temperature of 680-720℃, add refining agent to purify and stir to remove slag.

[0085] 3) After the alloy melt temperature stabilizes, pour the alloy melt into the preheated extrusion casting mold cavity at a casting temperature of 680-720℃. Apply pressure to the melt entering the mold cavity to solidify it under pressure and obtain the extrusion cast Al-10La-3Cu alloy product. The extrusion pressure is 65 MPa and the holding time is 15 s.

[0086] Figure 5 This is a SEM micrograph of the extruded Al-10La-3Cu alloy obtained in this comparative example. Figure 5 It can be seen that the alloy microstructure contains a dark gray α-Al matrix, a bright white lamellar eutectic structure, and some relatively coarse bright white second phases. Compared with the squeeze-cast Al-10La alloy, the quantity and type of second phases in the alloy have changed, and Cu-containing second phases or Al-La-Cu related phases appear in the microstructure.

[0087] To further demonstrate the effectiveness of this invention, the alloys obtained in the comparative examples and embodiments were tested for room temperature tensile properties and thermal conductivity. The alloy composition and preparation process of each comparative example and embodiment are shown in Table 1, and the performance test results are shown in Table 2.

[0088] Table 1. Composition and preparation process of each alloy in Comparative Examples 1-4 and Examples 1-2

[0089]

[0090] Table 2 Mechanical properties and thermal conductivity of alloys in Comparative Examples 1-4 and Examples 1-2

[0091]

[0092] As shown in Table 2, when alloyed with only 3 wt.% Cu, the tensile strength of the alloy in Comparative Example 2 only increased from 117.7 MPa to 137.9 MPa compared to Comparative Example 1, indicating a limited increase in strength. At the same time, the elongation after fracture of the alloy decreased from 8.7% to 6.7%, and the thermal conductivity decreased from 181.8 W / (m·K) to 161.2 W / (m·K). This means that although Cu alloying alone is beneficial to improving the strength of Al-La based alloys, it will lead to a decrease in plasticity and thermal conductivity. This invention, by designing an Al-La-Cu alloy system and further employing a controlled diffusion solidification and squeeze casting synergistic process, alters the solidification process of the alloy melt, enabling the formation of a more favorable second-phase microstructure during solidification. Simultaneously, pressure solidification enhances the density of the casting, resulting in an increase in the alloy's tensile strength to 188.0 MPa, yield strength to 80.7 MPa, while maintaining 16.1% elongation after fracture and 167.8 W / (m·K) thermal conductivity, achieving a comprehensive improvement in strength, plasticity, and thermal conductivity. In Comparative Example 3, although squeeze casting alone resulted in a higher elongation after fracture and higher thermal conductivity for the Al-10La alloy, the lack of second-phase strengthening from Cu resulted in a tensile strength of only 123.0 MPa. In Comparative Example 4, although the tensile strength increased to 161.0 MPa after combining Cu alloying with squeeze casting, it was still lower than in Example 1, and its yield strength was only 55.5 MPa. It is evident that neither Cu alloying alone nor extrusion casting alone can achieve a balance of strength, plasticity, and thermal conductivity. However, the synergistic treatment of controlled diffusion solidification and extrusion casting can achieve better overall performance in Al-La-Cu based rare earth aluminum alloys.

Claims

1. A high-strength, high-thermal-conductivity Al-La-Cu-based aluminum alloy, characterized in that: Composed of the following ingredients by weight percentage composition: La: 9-11 wt% Cu: 2.5-3.5 wt% Impurity elements: ≤0.20 wt% The balance is Al; The preparation method of the high-strength, high-thermal-conductivity Al-La-Cu-based aluminum alloy includes the following steps: 1) Precursor alloy smelting: Based on the target Al-La-Cu-based aluminum alloy, determine the composition and content of the first and second precursor alloys, and the mass ratio of the first and second precursor alloys is (2.5~3.5):1; the first precursor alloy is an Al-La alloy, which is obtained by melting pure aluminum and an aluminum-lanthanum intermediate alloy; the second precursor alloy is an Al-Cu alloy, which is obtained by melting pure aluminum and an aluminum-copper intermediate alloy; melt the raw materials of the first precursor alloy and melt the raw materials of the second precursor alloy to obtain the first precursor alloy melt and the second precursor alloy melt respectively; 2) Cool the first precursor alloy melt to 5-20°C above the first precursor alloy liquidus line, and cool the second precursor alloy melt to 5-20°C above the second precursor alloy liquidus line; then mix the first precursor alloy melt and the second precursor alloy melt evenly and add them to the preheated extrusion casting mold cavity. 3) Extrusion casting: Pressure is applied to the mixed melt entering the mold cavity, causing it to solidify under pressure to obtain a high-strength, high-thermal-conductivity Al-La-Cu-based aluminum alloy.

2. The high-strength, high-thermal-conductivity Al-La-Cu-based aluminum alloy according to claim 1, characterized in that: Step 3) Conditions for extrusion casting: extrusion pressure is 60~70 MPa, and holding time is 10~20 s.

3. The high-strength, high-thermal-conductivity Al-La-Cu-based aluminum alloy according to claim 1, characterized in that: La: 9.5-10.5 wt% Cu: 2.7-3.1 wt% Impurity elements: ≤0.20 wt% The balance is Al.

4. The high-strength, high-thermal-conductivity Al-La-Cu-based aluminum alloy according to claim 1, characterized in that: The aluminum-lanthanum master alloy is an Al-20La master alloy; the aluminum-copper master alloy is an Al-50Cu master alloy. The mass ratio of the first pioneer alloy melt to the second pioneer alloy melt is (2.5~3.5):

1.

5. The high-strength, high-thermal-conductivity Al-La-Cu-based aluminum alloy according to claim 4, characterized in that: The mass ratio of the first pioneer alloy melt to the second pioneer alloy melt is 3:

1.

6. The high-strength, high-thermal-conductivity Al-La-Cu-based aluminum alloy according to claim 1, characterized in that: In step 1), the melting temperature of the raw material of the first precursor alloy is 750–800°C, and the melting temperature of the raw material of the second precursor alloy is 750–800°C. The preheating temperature mentioned in step 2) is 180~220℃.

7. The high-strength, high-thermal-conductivity Al-La-Cu-based aluminum alloy according to claim 1, characterized in that: In step 2), when the target alloy contains 10 wt.% La and 3 wt.% Cu, the first precursor alloy melt and the second precursor alloy melt are cooled to 665–680 °C and 632–647 °C, respectively.

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