Method for improving high-temperature temperature-bearing performance of hypoeutectic aluminum-silicon alloy

Abstract

This invention relates to the field of high-performance aluminum alloy materials and component manufacturing, and provides a method for improving the high-temperature resistance of hypoeutectic aluminum-silicon alloys. The invention uses industrial pure aluminum, an aluminum-silicon master alloy, pure magnesium, and an Al-6%TiB2 master alloy prepared by a mixed salt reaction method as alloy raw materials. The alloy composition, by mass fraction, includes: Si: 3.5–7.5%, Mg: 0.3–0.4%, TiB2: 0–5%, with the remainder being Al and other impurity elements. Indirect extrusion casting technology is used to prepare aluminum-silicon alloy castings with different mass fractions of TiB2 particles. The TiB2 particles are uniformly distributed and tightly aggregated with the alloy matrix, significantly improving the material's high-temperature resistance and mechanical properties under medium- and high-temperature conditions.

Description

Technical Field

[0001] This invention relates to the field of manufacturing high-performance aluminum alloy materials and components, and in particular to a method for improving the high-temperature heat-bearing performance of hypoeutectic aluminum-silicon alloys. Background Technology

[0002] Aluminum-silicon alloys possess advantages such as high specific strength, good castability, excellent wear and corrosion resistance, and low cost, leading to their widespread application in the automotive and aerospace industries. However, due to the relatively simple elemental composition of aluminum-silicon alloys, their mechanical properties are significantly inferior to high-strength aluminum alloys such as aluminum-copper and aluminum-zinc alloys. Furthermore, in commonly used hypoeutectic aluminum-silicon alloys, such as ZL101 and ZL104, the main room-temperature strengthening phases, such as Mg2Si, tend to coarsen and grow at temperatures above 200°C, resulting in relatively poor heat resistance. Therefore, achieving a simultaneous improvement in both room-temperature and high-temperature mechanical properties of aluminum-silicon alloys is crucial for overcoming limitations in their application areas.

[0003] Particle-reinforced aluminum matrix composites can achieve significant improvements in mechanical properties by introducing a large number of hard particle reinforcing phases into the aluminum alloy matrix. Furthermore, the high-melting-point particle phases can stably exert their strengthening effect at high temperatures, thereby enhancing the high-temperature performance of the aluminum alloy matrix. Among various particle reinforcing phases, TiB2 particles possess characteristics such as high melting point, high strength, and high hardness, while also exhibiting good wettability and interfacial compatibility with the aluminum-silicon alloy matrix. Therefore, TiB2 particles can simultaneously exert both hard phase strengthening and grain refinement effects, achieving a synergistic improvement in the room-temperature and high-temperature properties of the matrix material.

[0004] Meanwhile, different casting processes also have a significant impact on aluminum-silicon alloy castings. Extrusion casting is an advanced precision casting process characterized by molten metal being filled and solidified under high pressure by a punch, resulting in aluminum alloy castings with fine, dense microstructures and excellent mechanical properties. However, due to the flow characteristics of the melt during filling and solidification in extrusion casting, aluminum-silicon alloy extrusion castings exhibit typical microstructural inhomogeneity, specifically the presence of large eutectic Si agglomerates in the sample microstructure. These large, brittle eutectic agglomerates negatively affect the performance of the extrusion castings. Therefore, improving the microstructural inhomogeneity of aluminum-silicon alloy extrusion castings is crucial for further enhancing their performance.

[0005] This invention achieves the preparation of aluminum-silicon alloy extrusion castings by introducing TiB2 particles into an aluminum-silicon alloy matrix and combining it with an extrusion casting process. The TiB2 particles in the microstructure act as a hard reinforcing phase, providing secondary phase strengthening, and also homogenize eutectic agglomeration through their synergistic distribution with eutectic Si at grain boundaries. Combining these two effects, the addition of TiB2 can achieve synergistic optimization of the microstructure and properties of the aluminum-silicon alloy extrusion castings. Summary of the Invention

[0006] This invention addresses the problem of poor mechanical properties of hypoeutectic aluminum-silicon alloys under high-temperature conditions in currently widely used alloys. It proposes a method to improve the high-temperature resistance of hypoeutectic aluminum-silicon alloys by introducing TiB2 particles as a reinforcing phase and combining it with extrusion casting technology to prepare high-strength aluminum-silicon alloy castings. The addition of TiB2 particles can play a role in both strengthening the second phase and homogenizing the eutectic agglomerate structure, thereby achieving synergistic optimization of the microstructure and properties of the castings.

[0007] To achieve the above objectives, the present invention provides a method for improving the high-temperature heat-bearing performance of hypoeutectic aluminum-silicon alloys, wherein the material composition, by mass percentage, includes: Si: 3.5-7.5%, Mg: 0.3-0.4%, TiB2: 0-5%, with the remainder being Al and other impurity elements.

[0008] This invention also provides a method for improving the high-temperature heat resistance of hypoeutectic aluminum-silicon alloys, with the following production steps:

[0009] Step (1) Alloy raw material preparation: Cut and weigh industrial pure aluminum, Al-30Si master alloy, pure magnesium and Al-6TiB2 master alloy according to the designed composition;

[0010] Step (2) Melting: 1) Place the weighed industrial pure aluminum and Al-30Si master alloy into a melting furnace and heat to 800℃ and hold; 2) After the alloy is completely melted, cool the melt temperature to 750℃, then add the weighed Al-6TiB2 master alloy according to the designed addition amount into the melt and hold until completely melted; 3) After further reducing the alloy melt temperature to 730℃, add the weighed pure magnesium into the melt and hold until completely melted; 4) Perform argon rotary blowing treatment on the alloy melt, and then let the melt stand to remove slag; 5) Perform ultrasonic vibration treatment on the melt to make the TiB2 particles in the melt uniformly dispersed;

[0011] Step (3) Perform extrusion casting: Pour the above-treated molten metal into the barrel of the extrusion casting equipment and perform the subsequent indirect extrusion casting process to obtain aluminum-silicon alloy extrusion castings.

[0012] Furthermore, the Al-6TiB2 master alloy in step (1) is prepared by a mixed fluoride salt reaction method, and the stoichiometric ratio of B / Ti is designed to be 2.2:1.

[0013] Furthermore, in step (2), the rotational blowing treatment time is 30 min and the rotation speed is 200 r / min.

[0014] Furthermore, in step (2), the power of the ultrasonic melt treatment is 2.5 kW, the vibration frequency is 20 kHz, and the treatment time is 0~5 min.

[0015] Furthermore, in step (3), the pouring temperature of the extrusion casting process is 700~750℃, and the mold temperature is 220℃.

[0016] Furthermore, in step (3), the extrusion casting pressure is 120 MPa, the injection speed is 110 mm / s, and the holding time is 15 s.

[0017] The method for improving the high-temperature heat-resistant properties of hypoeutectic aluminum-silicon alloys disclosed in this invention has the following advantages over existing technologies:

[0018] (1) In this invention, Al-6TiB2 intermediate alloy is prepared in situ by mixed salt reaction method, and then TiB2 reinforcing particles are introduced into commonly used hypoeutectic aluminum-silicon alloy matrix by remelting and dilution. TiB2 particles, as hard reinforcing phase, can achieve synergistic improvement of room temperature and high temperature performance of aluminum-silicon alloy matrix through the effects of second phase strengthening and grain refinement.

[0019] (2) The present invention combines the remelting dilution method with indirect extrusion casting technology to prepare high heat-resistant aluminum-silicon alloy castings. As a liquid precision casting process, the present invention has the advantages of simple process flow, high preparation efficiency and stable and controllable casting quality. It is easy to realize industrial production. More importantly, the extrusion casting process can solve the forming problem of reduced casting performance caused by adding TiB2 to increase the viscosity of the alloy melt. At the same time, the pressure-assisted solidification conditions of the overall forming process can better promote the homogenization of TiB2 and the good combination with the alloy matrix, laying the foundation for performance improvement.

[0020] (3) The stoichiometric ratio of B / Ti elements in the Al-6TiB2 master alloy design used in this invention is 2.2:1, that is, B element is in excess compared to Ti element. Compared with the traditional Ti-excess type Al-Ti-B master alloy, the hexagonal plate-like morphology of TiB2 particles in the master alloy used in this invention is improved due to the presence of excess B element, and its morphology is more equiaxed, thus having a better strengthening effect on the aluminum alloy matrix. Attached Figure Description

[0021] Figure 1 The room temperature and high temperature tensile mechanical properties of hypoeutectic aluminum alloy materials prepared using the present invention are determined. Detailed Implementation

[0022] The present invention will be further described below through specific embodiments.

[0023] Example 1

[0024] This embodiment provides a method for preparing 3%TiB2 / Al-7Si-0.4Mg aluminum-silicon alloy material using the content of this invention. The specific implementation method is as follows:

[0025] Step (1) Alloy raw material preparation: Cut and weigh industrial pure aluminum, Al-30Si master alloy, pure magnesium and Al-6TiB2 master alloy according to the composition ratio of Si:7%, Mg:0.4%, TiB2:3%, and the remainder is Al and other impurity elements.

[0026] Step (2) Melting: 1) Place the weighed industrial pure aluminum and Al-30Si master alloy into a melting furnace and heat to 800℃ and hold; 2) After the alloy is completely melted, lower the melt temperature to 750℃ and add Al-6TiB2 master alloy to the melt, and hold until completely melted; 3) Further lower the alloy melt temperature to 730℃ and add pure magnesium to the melt; 4) Perform argon rotary blowing treatment on the melt at a speed of 220 r / min for 30 min, and then let the melt stand to remove slag; 5) Perform ultrasonic vibration treatment on the melt at a power of 2.5 kW and a vibration frequency of 20 kHz for 5 min.

[0027] Step (3) Extrusion casting: The above-treated alloy melt is poured into the barrel and indirect extrusion casting is performed. The pouring temperature is 730℃, the casting pressure is 120MPa, the injection speed is 110 mm / s, the mold temperature is 220℃, and the holding time is 15 s.

[0028] Comparative Example 1

[0029] This comparative example provides a method for preparing 0%TiB2 / Al-7Si-0.4Mg aluminum-silicon alloy material by extrusion casting. The specific implementation method is as follows:

[0030] Step (1) Alloy raw material preparation: Cut and weigh industrial pure aluminum, Al-30Si master alloy and pure magnesium according to the composition ratio of Si:7%, Mg:0.4%, and the remainder being Al and other impurity elements;

[0031] Step (2) Melting: 1) Place the weighed industrial pure aluminum and Al-30Si master alloy into the melting furnace and heat it to 800℃ and hold it there; 2) After the alloy is completely melted, lower the temperature of the melt to 730℃ and add pure magnesium to the melt, and hold it until it is completely melted; 3) Perform argon rotary blowing on the melt at a speed of 220 r / min for 30 min, and then let the melt stand to remove slag.

[0032] Step (3) Extrusion casting: The above-treated alloy melt is poured into the barrel and indirect extrusion casting is performed. The pouring temperature is 730℃, the casting pressure is 120MPa, the injection speed is 110 mm / s, the mold temperature is 220℃, and the holding time is 15 s.

[0033] Comparative Example 2

[0034] This comparative example provides a gravity casting method for preparing a 0%TiB2 / Al-7Si-0.4Mg aluminum-silicon alloy material. The specific implementation method is as follows:

[0035] Step (1) Alloy raw material preparation: Cut and weigh industrial pure aluminum, Al-30Si master alloy and pure magnesium according to the composition ratio of Si:7%, Mg:0.4%, and the remainder being Al and other impurity elements;

[0036] Step (2) Melting: 1) Place the weighed industrial pure aluminum and Al-30Si master alloy into the melting furnace and heat it to 800℃ and hold it there; 2) After the alloy is completely melted, lower the temperature of the melt to 730℃ and add pure magnesium to the melt, and hold it until it is completely melted; 3) Perform argon rotary blowing on the melt at a speed of 220 r / min for 30 min, and then let the melt stand to remove slag.

[0037] Step (3) Gravity casting: The above-treated alloy melt is poured into a metal mold at a pouring temperature of 730°C.

[0038] Comparative Example 3

[0039] This comparative example provides a gravity casting method for preparing a 3%TiB2 / Al-7Si-0.4Mg aluminum-silicon alloy material. The specific implementation method is as follows:

[0040] Step (1) Alloy raw material preparation: Cut and weigh industrial pure aluminum, Al-30Si master alloy, pure magnesium and Al-6TiB2 master alloy according to the composition ratio of Si:7%, Mg:0.4%, TiB2:3%, and the remainder is Al and other impurity elements.

[0041] Step (2) Melting: 1) Place the weighed industrial pure aluminum and Al-30Si master alloy into a melting furnace and heat to 800℃ and hold; 2) After the alloy is completely melted, lower the melt temperature to 750℃ and add Al-6TiB2 master alloy to the melt, and hold until completely melted; 3) Further lower the alloy melt temperature to 730℃ and add pure magnesium to the melt; 4) Perform argon rotary blowing treatment on the melt at a speed of 220 r / min for 30 min, and then let the melt stand to remove slag; 5) Perform ultrasonic vibration treatment on the melt at a power of 2.5 kW and a vibration frequency of 20 kHz for 5 min.

[0042] Step (3) Gravity casting: The above-treated alloy melt is poured into a metal mold at a pouring temperature of 730°C.

[0043] Table 1 Tensile properties of materials prepared in the examples and comparative examples at 150°C

[0044] serial number Tensile strength / MPa Yield strength / MPa Example 1 219 140 Comparative Example 1 205 123 Comparative Example 2 177 106 Comparative Example 3 165 110

[0045] Table 1 compares the high-temperature tensile mechanical properties of the alloys prepared in the examples and comparative examples. The results show that the aluminum alloy containing TiB2 particles prepared in Example 1, compared to the aluminum alloy without TiB2 particles under the same forming process in Comparative Example 1, exhibits approximately a 7% improvement in as-cast high-temperature tensile properties and an approximately 14% improvement in yield strength, clearly demonstrating the beneficial effects of the material system design in this invention. A direct comparison of Comparative Examples 2 and 3 shows that, under gravity casting conditions, the addition of TiB2 particles does not achieve the same improvement in high-temperature tensile mechanical properties under the same material system. This indicates that the material system design in this invention must be used in conjunction with the extrusion casting process to achieve the expected positive effects.

[0046] This invention is not limited to the specific embodiments described above. This invention extends to any new features or combinations disclosed in this specification, as well as any new steps or combinations of new methods or processes disclosed herein, all of which should be covered within the scope of protection of this invention.

Claims

1. A method for improving the high-temperature heat-bearing performance of hypoeutectic aluminum-silicon alloys, characterized in that, The alloy composition, by mass percentage, includes: Si: 3.5–7.5%, Mg: 0.3–0.4%, TiB2: 0–5%, with the remainder being Al and other impurity elements.

2. The method for improving the high-temperature heat-bearing performance of hypoeutectic aluminum-silicon alloys as described in claim 1, characterized in that, Includes the following steps: Step (1) Preparation of alloy raw materials: Prepare industrial pure aluminum and Al-30Si master alloy (Al-30Si). wt.%Si, the same below), pure magnesium and Al-6TiB2 master alloy are cut and weighed according to the designed composition and balanced; Step (2) Melting: 1) Put the above weighed industrial pure aluminum and Al-30Si master alloy into the melting furnace and heat it to 800℃ and keep it at that temperature; 2) After the alloy is completely melted, cool the melt temperature to 750℃, and then add the Al-6TiB2 master alloy weighed according to the designed addition amount into the melt and keep it at that temperature until it is completely melted; 3) After further reducing the alloy melt temperature to 730℃, add the weighed pure magnesium into the melt and keep it at that temperature until it is completely melted; 4) Perform argon gas rotary blowing treatment on the alloy melt, and then let the melt stand to remove slag; 5) Perform ultrasonic vibration treatment on the melt to make the TiB2 particles in the melt evenly dispersed; Step (3) Perform indirect extrusion casting: Pour the above-treated metal melt into the barrel of the extrusion casting equipment and perform subsequent indirect extrusion casting molding.

3. The method for improving the high-temperature heat-bearing performance of hypoeutectic aluminum-silicon alloys according to claim 2, characterized in that, The Al-6TiB2 master alloy in step (1) was prepared by a mixed fluoride salt reaction method, and the stoichiometric ratio of B / Ti was designed to be 2.2:

1.

4. The method for improving the high-temperature heat-bearing performance of hypoeutectic aluminum-silicon alloys according to claim 2, characterized in that, In step (2), the rotational blowing treatment time is 30 min and the rotation speed is 200 r / min.

5. The method for improving the high-temperature heat-bearing performance of hypoeutectic aluminum-silicon alloys according to claim 2, characterized in that, In step (2), the ultrasonic melt treatment power is 2.5 kW, the vibration frequency is 20 kHz, and the treatment time is 0~5 min.

6. The method for improving the high-temperature heat-bearing performance of hypoeutectic aluminum-silicon alloys according to claim 2, characterized in that, In step (3), the pouring temperature of the extrusion casting process is 700~750℃ and the mold temperature is 220℃.

7. The method for improving the high-temperature heat-bearing performance of hypoeutectic aluminum-silicon alloys according to claim 2, characterized in that, In step (3), the extrusion casting pressure is 120 MPa, the injection speed is 110 mm / s, and the holding time is 15 s.

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