A high-efficiency extrusion preparation method for high-temperature resistant aluminum-based composite materials

Abstract

The present invention discloses a high-efficiency extrusion preparation method for a high-temperature resistant aluminum-based composite material, belonging to the technical field of aluminum-based composite materials. The method comprises: (1) hot-pressing a mixed powder of TiO2 and Al twice to prepare an ingot having a low-strength TiO2 / Al at one end and a high-strength (Al2O3+Al3Ti) / Al at the other end; (2) using the low-strength end as an extrusion starter to complete extrusion to obtain a profile; and (3) subjecting the extruded profile to high-temperature treatment to obtain a high-temperature resistant (Al2O3+Al3Ti) / Al composite material having uniform composition and properties. This method can prepare a high-strength, high-temperature resistant composite material and obtain the desired profile by extrusion, while avoiding subsequent machining, effectively improving material utilization and reducing preparation costs.

Description

Technical Field

[0001] The present invention relates to the technical field of aluminum-based composite materials, and in particular to a high-efficiency extrusion preparation method for high-temperature resistant aluminum-based composite materials. Background Art

[0002] Traditional high-strength aluminum alloys generally operate below 100°C, with their strength deteriorating dramatically above 200°C. Commonly used high-temperature aluminum alloys like 2A16 and ZL205 only have an instantaneous tensile strength of around 100 MPa at 300°C. Therefore, at temperatures above 250°C, titanium alloys and stainless steel are often used to manufacture structural components, making lightweight structural design difficult.

[0003] Aluminum-based composites with ceramic particles as the reinforcement phase can have very excellent high-temperature thermal stability. Among them, Al2O3 particles have good compatibility with the aluminum matrix and have excellent stability at high temperatures. However, it is difficult for Al2O3 introduced by conventional external addition methods to have an orientation relationship with the aluminum matrix, the reinforcement efficiency is low, and large-scale addition will seriously damage the plasticity of the material. Adding TiO2 particles to the aluminum matrix completes the in-situ reaction during the hot pressing process to generate (Al2O3+Al3Ti) / Al, and the material can have extremely high high-temperature strength (literature "Design, microstructure and high temperature properties of in-situAl3Ti and nano-Al2O3 reinforced 2024Al matrix composites from Al-TiO2 system": Journal of Alloys and Compounds, 2019, 775: 290). However, this material has high high-temperature strength and is difficult to deform, so it is difficult to extrude and deform to obtain profiles and further improve performance. Patent No. 201611079376.1 provides a method for preparing and extruding high-volume-fraction composite materials. However, this method requires other easily deformable materials as ingots. The surface of the extruded material is coated with a layer of low-strength material, which requires additional machining to remove. This results in low material utilization and increases the material preparation cost.

[0004] Based on the above background, this patent provides a high-efficiency preparation and extrusion method for high-temperature resistant aluminum-based composite materials that have both high-temperature mechanical properties and deformation capabilities and do not require subsequent machining. Summary of the Invention

[0005] The purpose of the present invention is to provide a high-efficiency extrusion preparation method for high-temperature resistant aluminum-based composite materials, which uses aluminum powder and TiO2 particles as raw materials, forms a material billet with a soft front end and a hard back end through two sintering processes, then uses the low-strength material at the front end as the extrusion ingot to complete the extrusion deformation, and finally uses high-temperature treatment to make the low-strength material outside the extruded material complete in-situ reaction, thereby achieving homogenization of the entire material composition and mechanical properties.

[0006] To achieve the above object, the technical solutions adopted by the present invention are as follows:

[0007] A high-efficiency extrusion preparation method for a high-temperature resistant aluminum-based composite material comprises the following steps:

[0008] (1) Aluminum powder and TiO2 particles are blended to obtain a mixed powder, and a portion of the mixed powder is cold pressed to obtain a compact I;

[0009] (2) subjecting the compact I obtained after the pressing and molding in step (1) to high-temperature powder metallurgy sintering to obtain ingot I;

[0010] (3) placing the remaining portion of the mixed powder in step (1) and the billet I obtained after sintering in step (2) in the same mold, placing the powder at one end of the billet I, and cold pressing again to obtain a compact II;

[0011] (4) performing low-temperature powder metallurgy sintering on the compact II obtained after the compacting in step (3) to obtain an ingot II;

[0012] (5) Extruding the billet II obtained in step (4) to obtain an extruded sample; the front end of the billet II is a low-strength material (the portion corresponding to the second powder loading) and the rear end is a high-strength material (the portion corresponding to the billet I). During the extrusion process, one end of the second powder loading is at the front (contacting the extrusion die), and the extrusion ratio is 5:1 to 25:1. During the extrusion process, the material obtained by low-temperature sintering at the front end can be used as an extrusion ingot and flows in the opposite direction of extrusion to coat the surface of the extruded material;

[0013] (6) subjecting the extruded sample obtained in step (5) to high-temperature treatment to obtain a high-temperature resistant aluminum-based composite material with uniform composition.

[0014] In the above step (1), the average particle size of the aluminum powder is 0.1-200 μm, the average particle size of the TiO2 particles is 0.01-100 μm, and the blending method is mechanical mixing or ball milling mixing; the TiO2 particle content in the mixed powder obtained after blending is 3-25wt%.

[0015] In the above step (1), the pressed powder accounts for 60-90% of the total powder mass, and the density reaches 60-80% after cold pressing.

[0016] In the above step (2), the high-temperature powder metallurgy sintering adopts vacuum hot pressing sintering, cold isostatic pressing, hot isostatic pressing or discharge ion beam sintering process under atmosphere or vacuum conditions, and the sintering temperature in the high-temperature powder metallurgy sintering is 605-655°C.

[0017] In the above step (3), the density of the newly charged powder after cold pressing reaches 40-60%.

[0018] In the above step (4), the low-temperature powder metallurgy sintering adopts vacuum hot pressing sintering, cold isostatic pressing, hot isostatic pressing or discharge ion beam sintering process under atmosphere or vacuum conditions, and the sintering temperature in the low-temperature powder metallurgy sintering is 550-600°C.

[0019] In the above step (5), the extrusion temperature is 300-500°C.

[0020] In the above step (6), the high temperature treatment temperature is 600-630° C. and the time is 2-12 hours.

[0021] The advantages and beneficial effects of the (Al2O3+Al3Ti) / Al high temperature resistant aluminum-based composite material preparation and extrusion method of the present invention are as follows:

[0022] 1. Compared with traditional high-temperature aluminum alloys, the aluminum-based composite material prepared by the present invention has higher high-temperature strength and thermal stability.

[0023] 2. Compared with Al2O3 / Al prepared by the external addition method, the Al2O3+Al3Ti introduced in situ in the present invention has a higher reinforcement efficiency, thereby reducing the reinforcement phase content and improving the plasticity of the material.

[0024] 3. Compared with the (Al2O3+Al3Ti) / Al directly obtained by one-step hot pressing, the present invention has low-strength TiO2 / Al at the extrusion front end, which can play the role of extrusion ingot, making the material easier to flow. TiO2 / Al acts as a lubricant between the mold and the difficult-to-deform (Al2O3+Al3Ti) / Al, reducing the tensile stress generated by the friction between the billet surface and the mold, and placing the (Al2O3+Al3Ti) / Al in a three-dimensional compressive stress state, making it easier to plastically deform.

[0025] 4. Compared with the method of adding a guide ingot to the front end of the billet by welding or other methods in the later stage, the present invention can directly transform the external low-strength material into high-strength (Al2O3+Al3Ti) / Al by high-temperature treatment in the later stage, thereby making the material utilization rate close to 100% and eliminating the high machining cost.

[0026] 5. The aluminum-based composite material prepared by the present invention has excellent high-temperature mechanical properties and can be extruded into final profiles. Therefore, the material combines mechanical properties with deformation capacity, has high material utilization, and can eliminate machining costs, enabling large-scale industrial production and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of hot extrusion molding of the present invention. DETAILED DESCRIPTION

[0028] The present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0029] In the following examples, billet II is hot extruded to obtain an extruded sample, wherein the front end of the extruded sample is a low-strength material (the portion corresponding to the second loading of powder) and the rear end is a high-strength material (the portion corresponding to billet I). During the extrusion process, the second loaded powder is at the front end (in contact with the extrusion die) and billet I is at the rear end (in contact with the extrusion rod). During the extrusion process, the material obtained by low-temperature sintering at the front end can be used as an extrusion ingot and flows in a direction opposite to the extrusion direction to coat the surface of the extruded material.

[0030] Example 1:

[0031] This embodiment is a high-efficiency preparation method for high-temperature resistant aluminum-based composite materials. The preparation process is as follows: Figure 1 , as follows:

[0032] Spherical aluminum powder with an average particle size of 10μm was mixed with TiO2 particles with an average particle size of 0.04μm using a high-energy ball mill. The resulting mixed powder contained 6wt% TiO2 particles. 90% of the mixed powder was removed and cold-pressed at 200MPa. The mixture was then sintered in a vacuum furnace at 620°C for 2 hours to produce Ingot I. After cooling, the mold was opened and one end was loaded with the remaining 10% of the mixed powder. The mixture was cold-pressed again and sintered in a vacuum furnace at 580°C to produce Ingot II. The sintered Ingot II was hot-extruded at 450°C with an extrusion ratio of 16:1, with the end loaded with the last 10% of the powder facing forward. The extruded material was then treated at 610°C for 8 hours to obtain the final aluminum-based composite material.

[0033] The (Al2O3+Al3Ti) / Al extruded profile manufactured using this embodiment can achieve uniform composition and mechanical properties without machining; after testing, the extruded profile has a strength of 246 MPa at 350°C, and the strength decay is less than 5% after being kept at 350°C for more than 2000 hours.

[0034] Comparative Example 1

[0035] Spherical aluminum powder with an average particle size of 10 μm was mixed with TiO2 particles with an average particle size of 0.04 μm using a high-energy ball mill. The resulting mixed powder contained 6 wt% TiO2. The entire mixed powder was cold-pressed at 200 MPa and sintered in a vacuum furnace at 620°C for 2 hours. The sintered ingot was then hot-extruded at 450°C with an extrusion ratio of 16:1. However, cracking occurred during the extrusion process, and the desired profile could not be obtained.

[0036] Comparative Example 2

[0037] Spherical aluminum powder with an average particle size of 10 μm was mixed with TiO2 particles with an average particle size of 0.04 μm using a high-energy ball mill. The resulting mixed powder contained 6% TiO2 by weight. The mixed powder was cold-pressed at 200 MPa and sintered in a vacuum furnace at 620°C for 2 hours. A 6060 aluminum alloy pad was welded to the front end of the sintered ingot as an extrusion starter, and then hot extruded at 450°C with an extrusion ratio of 16:1.

[0038] The surface of the obtained material has a layer of 6061 aluminum alloy with uneven composition and mechanical properties, which needs to be removed by mechanical processing, resulting in low material utilization, complex preparation process and high cost.

[0039] Example 2

[0040] Spherical aluminum powder with an average particle size of 10 μm is mixed with TiO2 particles with an average particle size of 2 μm using a high-energy ball mill. The resulting mixed powder contains 20% TiO2 particles by weight. 80% of the mixed powder is cold-pressed at 200 MPa and sintered in a vacuum furnace at 620°C for 2 hours. After cooling, the mold is opened and the remaining 20% ​​of the mixed powder is loaded at one end. The mold is cold-pressed again and sintered in a vacuum furnace at 580°C. The sintered ingot is hot-extruded at 450°C with an extrusion ratio of 16:1, with the end with the 20% powder loaded last facing the front. The extruded material is then heat-treated at 620°C for 10 hours to obtain the final product.

[0041] This embodiment was used to manufacture (Al2O3+Al3Ti) / Al extruded profiles, achieving uniform composition and mechanical properties without machining. Testing showed that the extruded profiles had a strength of 290 MPa at 350°C and exhibited a strength loss of less than 5% after being held at 350°C for more than 2,000 hours.

[0042] The above embodiments describe the present invention, but the embodiments are only intended to further illustrate the features and advantages of the present invention, rather than to limit the claims of the present invention.

Claims

1. A high-efficiency extrusion preparation method for high-temperature resistant aluminum-based composite materials, characterized by: The high-efficiency extrusion preparation method comprises the following steps: (1) Aluminum powder and TiO2 particles are blended to obtain a mixed powder, and a portion of the mixed powder is cold pressed to obtain a compact I; (2) subjecting the compact I obtained after the compacting in step (1) to high-temperature powder metallurgy sintering to obtain ingot I; the high-temperature powder metallurgy sintering adopts vacuum hot pressing sintering, hot isostatic pressing or discharge ion beam sintering process, and the sintering temperature in the high-temperature powder metallurgy sintering is 605-655°C; (3) placing the remaining portion of the mixed powder in step (1) and the billet I obtained after sintering in step (2) in the same mold, placing the powder at one end of the billet I, and cold pressing again to obtain a compact II; (4) performing low-temperature powder metallurgy sintering on the compact II obtained after the compacting in step (3) to obtain an ingot II; the low-temperature powder metallurgy sintering adopts a vacuum hot pressing sintering, hot isostatic pressing or discharge ion beam sintering process, and the sintering temperature in the low-temperature powder metallurgy sintering is 550-600°C; (5) Extruding the billet II obtained in step (4) to obtain an extruded sample; during the extrusion process, the end of the second powder loading is in front and contacts the extrusion die, and the extrusion ratio is 5:1-25:

1. During the extrusion process, the material obtained by low-temperature sintering at the front end is used as an extrusion ingot and flows in the opposite direction of extrusion to coat the surface of the extruded material; the extrusion temperature is 300-500°C; the front end of the billet II is a low-strength material, that is, the part corresponding to the second powder loading; The rear end is made of high-strength material, which is the part corresponding to billet I; (6) The extruded sample obtained in step (5) is subjected to high temperature treatment at a temperature of 600-630°C for a time of 2-12 hours to obtain a high temperature resistant aluminum-based composite material with uniform composition.

2. The high-efficiency extrusion preparation method of high-temperature resistant aluminum-based composite material according to claim 1, characterized in that: In step (1), the average particle size of the aluminum powder is 0.1-200 μm, the average particle size of the TiO2 particles is 0.01-100 μm, and the blending method is mechanical mixing or ball milling mixing; the TiO2 particle content in the mixed powder obtained after blending is 3-25wt%.

3. The high-efficiency extrusion preparation method of high-temperature resistant aluminum-based composite material according to claim 1, characterized in that: In step (1), the pressed powder accounts for 60-90% of the total powder mass, and the density reaches 60-80% after cold pressing.

4. The high-efficiency extrusion preparation method of high-temperature resistant aluminum-based composite material according to claim 1, characterized in that: In step (3), the density of the newly charged powder after cold pressing reaches 40-60%.

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