Sc, zr composite microalloyed high temperature wear-resistant 6061 aluminum alloy and its preparation method by deformation aging

Abstract

The application discloses a kind of Sc, Zr composite microalloying high-temperature wear-resistant 6061 aluminum alloy and its deformation aging preparation method.The aluminum alloy is composed of the following components: Sc, Zr, Mg, Si, Cu, the balance is Al and inevitable impurities.Preparation method includes: smelting casting→homogenization→solid solution treatment→cold rolling→aging treatment.The application forms Al3(Sc,Zr) core-shell nano precipitate phase by Sc, Zr synergistic microalloying, combined with dislocation strengthening introduced by deformation aging, solves the defect of abnormal deterioration of single Sc microalloying in 120℃ medium temperature zone wear resistance, the tensile strength of the obtained alloy is increased by ≥23% compared with conventional 6061 aluminum alloy, and the wear loss at 150℃ is reduced by ≥26%, suitable for high-temperature heavy-load working conditions of aluminum alloy moving parts.

Description

Technical Field

[0001] This invention belongs to the field of non-ferrous metal material processing and tribology technology, specifically relating to a Sc and Zr composite microalloyed high-temperature wear-resistant 6061 aluminum alloy and its deformation aging preparation method. Background Technology

[0002] 6061 aluminum alloy (Al-Mg-Si system) is commonly used in aerospace, automotive manufacturing, and precision machinery industries to manufacture moving parts such as pistons, scroll disks, and bearing cages due to its high specific strength, good corrosion resistance, and excellent machinability. However, after T6 treatment, conventional 6061 aluminum alloy exhibits relatively low hardness and wear resistance, making it prone to early wear failure under harsh conditions such as high temperature and heavy load, which makes it difficult to meet the increasingly demanding requirements for long service life and high reliability in equipment.

[0003] To improve the mechanical properties and thermal stability of aluminum alloys, existing research has attempted to incorporate trace amounts of Sc and Zr elements. These elements can generate nanoscale, fully coherent Al3(Sc,Zr) composite phases in situ within the matrix, significantly refining the grain size and producing a dispersion strengthening effect. However, in the process of developing this invention, the applicant discovered the following technical obstacles when applying this Sc and Zr microalloying technology to 6061 aluminum alloy to improve its tribological properties:

[0004] 1. Existing research on the performance of Sc and Zr microalloyed aluminum alloys mainly focuses on room temperature tensile properties. There are few systematic reports on their wear behavior and wear mechanism under near-real service conditions such as high temperature and wet friction, and there is a lack of effective performance evaluation basis.

[0005] 2. The applicant unexpectedly discovered that 6061 aluminum alloy with only added Sc exhibits an abnormal phenomenon when subjected to friction in a medium-temperature range of approximately 120°C, with a significantly increased wear rate compared to room temperature, i.e., the existence of a "medium-temperature adhesive wear sensitive zone." This phenomenon is not documented in existing publicly available literature, and there is currently no effective solution.

[0006] 3. For Al3(Sc,Zr) composite phases formed by the synergistic addition of Sc and Zr, the quantitative or semi-quantitative correlation between its microscopic parameters (such as the size, distribution, and volume fraction of the core-shell structure phase) and the transformation of the final wear mechanism (such as adhesive wear, abrasive wear, and oxidative wear) is currently poorly understood, making it difficult to guide the development of high wear-resistant aluminum alloys from the perspective of microstructure design.

[0007] 4. For 6061 aluminum alloy with Sc and Zr composite microalloying, how to further improve its mechanical and wear resistance properties by optimizing deformation and aging processes (such as introducing cold rolling pre-deformation after solution treatment) has not been fully explored and clarified.

[0008] The aforementioned technical obstacles have restricted the development and application of high-performance, high-temperature wear-resistant 6061 aluminum alloys. There is an urgent need to provide an aluminum alloy material and its preparation method that can overcome the defects of medium-temperature wear resistance degradation caused by single Sc microalloying and possess excellent room-temperature and high-temperature mechanical and tribological properties. Summary of the Invention

[0009] In view of the above, it is necessary to provide a Sc and Zr composite microalloyed high temperature and wear resistant 6061 aluminum alloy and its deformation aging preparation method. Under the premise of ensuring good plasticity of the alloy, it significantly improves its room temperature and high temperature strength, especially solving the problem of abnormal deterioration of wear performance in the mid-temperature range of 120℃, and achieving excellent wear resistance in a wide temperature range.

[0010] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0011] A Sc / Zr composite microalloyed high-temperature and wear-resistant 6061 aluminum alloy is composed of the following components by mass percentage: Sc 0.10~0.25%, Zr 0.15~0.35%, Mg 0.8~1.2%, Si 0.4~0.8%, Cu 0.15~0.40%, with the balance being Al and unavoidable impurities. In this aluminum alloy, the Fe content is controlled to ≤0.1%, and the content of other individual impurities is ≤0.05% to ensure the alloy's toughness.

[0012] In this invention, the Sc content is 0.15-0.20%, the Zr content is 0.20-0.30%, and the mass ratio of Sc to Zr is 1:1.2-1:1.5.

[0013] In this invention, the Sc content is 0.18% and the Zr content is 0.25%.

[0014] This invention also proposes a method for preparing the above-described aluminum alloy, comprising the following steps:

[0015] (1) Prepare the ingredients according to the above-mentioned composition, melt at 750~780℃, refine and degas, and then cast into ingots at 710~730℃;

[0016] (2) Homogenization treatment: The ingot is kept at 560℃ for 10 hours and then cooled with the furnace;

[0017] (3) Solution treatment: Hold at 530~560℃ for 1~2 hours, then water quench;

[0018] (4) Cold rolling: The billet after solution treatment is cold rolled, with a total deformation of 3% to 10%;

[0019] (5) Aging treatment: Keep warm at 160~180℃ for 8~18 hours, then air cool.

[0020] In this invention, the solution temperature of step (3) is 535±5℃ and the holding time is 1.5 hours; the cold rolling deformation of step (4) is 6±1%; and the aging temperature of step (5) is 175±5℃ and the holding time is 12 hours.

[0021] Furthermore, in this invention, its microstructure contains an L12 structure Al3(Sc,Zr) nanoprecipitate phase that is completely coherent with the α-Al matrix. This precipitate phase has Sc enriched cores and Zr enriched shells, with an average particle size of 5~15 nm and a particle spacing of 30~50 nm.

[0022] In this invention, after cold rolling in step (4) and aging treatment in step (5), the Al3(Sc,Zr) nanophase in the obtained alloy is surrounded by high-density dislocation rings and dislocation entanglements.

[0023] Furthermore, in this invention, the room temperature Vickers hardness is ≥85 HV, the tensile strength is ≥360 MPa, and the elongation after fracture is ≥8%.

[0024] Furthermore, under wet friction conditions, when the grinding pair is GCr15 steel balls and the ambient temperature is 150°C, its wear is reduced by at least 25% compared to 6061 aluminum alloy without added Sc and Zr.

[0025] Furthermore, under wet friction conditions, when the grinding pair is GCr15 steel ball and the ambient temperature is 120°C, its wear is reduced by at least 20% compared to 6061 aluminum alloy with only Sc added under the same conditions, and the wear mechanism is a composite mechanism of abrasive wear and oxidative wear.

[0026] Compared with the prior art, the present invention has at least the following beneficial effects:

[0027] 1. This invention utilizes Sc and Zr composite microalloying to generate in-situ L12 structured Al3(Sc,Zr) core-shell nanoprecipitates in the aluminum matrix, which are completely coherent with the α-Al matrix. Simultaneously, combined with the high-density dislocation structure introduced by the solution-cold rolling-aging process, a triple synergistic effect of grain refinement strengthening, dispersion strengthening, and dislocation strengthening is achieved. The alloy in Example 5 exhibits a room temperature tensile strength of 394.5 MPa, a yield strength of 342.1 MPa, and a hardness of 129.83 HV, representing increases of approximately 23%, 21.6%, and 14.6% respectively compared to the 6061 matrix alloy. Furthermore, the elongation after fracture remains at 8.2%, achieving a good balance between strength and plasticity. This invention also discovers and solves for the first time the problem of the "adhesive wear sensitive zone" in the mid-temperature range of approximately 120°C for 6061 aluminum alloy with only added Sc: the wear amount of the Sc-containing alloy at 120°C is 68% higher than that at 90°C, and the wear mechanism is mainly severe adhesive wear, with a surface roughness Sa value of 13.04 μm; while the wear amount of the alloy of this invention at 120°C is only 0.0032 mg, which is about 23.8% lower than that of the Sc-containing alloy, and the wear mechanism is changed to mainly oxidation wear and mild abrasive wear, with the Sa value reduced to 7.29 μm, a smooth surface, and shallow and uniform furrows. The mechanism is as follows: the addition of Zr forms an Al3(Sc,Zr) core-shell composite phase with higher thermal stability. Zr atoms have a low diffusion rate, and this phase does not undergo significant coarsening in the mid-temperature range, which can effectively pin dislocations; at the same time, Zr participates in the formation of a dense mechanical mixed oxide layer containing ZrO2, which inhibits direct metal contact and adhesive transfer between friction pairs.

[0028] 2. The alloy of this invention exhibits excellent friction and wear resistance across a wide temperature range of 90℃ to 150℃. Under high-temperature wet friction conditions at 150℃, the wear amount of the alloy in Example 5 is 0.0042mg, which is about 26.3% lower than that of the 6061 matrix alloy, about 19.2% lower than that of the single Zr-containing alloy, and about 12.5% ​​lower than that of the single Sc-containing alloy. The friction coefficient curves at each temperature are stable without drastic fluctuations, and the plastic deformation layer on the worn surface is thin, indicating that the alloy can operate stably for a long time under high temperature, heavy load, and complex lubrication conditions. The introduction of cold rolling pre-deformation further enhances the above properties: compared with the T6 state alloy and the deformation-aged state alloy of the same composition, the high-density dislocations introduced by cold rolling provide more nucleation sites for aging precipitation and form stable dislocation loops and dislocation entanglements around the Al3(Sc,Zr) nanophase, enhancing the subsurface shear deformation resistance and further reducing the wear amount at each temperature point.

[0029] 3. The alloy composition of this invention is based on commercially available 6061 aluminum alloy, with only trace amounts of Sc and Zr added. The preparation process is based on existing aluminum alloy processing equipment, requiring no additional equipment investment, and the process cost is controllable, making it easy to achieve industrial production. The resulting alloy is suitable for manufacturing aluminum alloy moving parts under high temperature, heavy load, and lubrication conditions, and has broad application prospects in aerospace, automotive, and precision machinery fields. Attached Figure Description

[0030] Figure 1 The X-ray diffraction patterns are for Examples 2, 3 and 5.

[0031] Figure 2 The metallographic structures of Examples 1 and 5 are shown.

[0032] Figure 3 The following are the engineering stress-strain curves for Examples 1, 2, 3, and 5.

[0033] Figure 4 The aging-hardness curves are for Examples 1, 2, 3 and 5.

[0034] Figure 5 The friction coefficient curves for Example 1 under wet friction conditions at 90℃, 120℃, and 150℃ are shown.

[0035] Figure 6 The friction coefficient curves for Example 2 under wet friction conditions at 90℃, 120℃, and 150℃ are shown.

[0036] Figure 7 The friction coefficient curves for Example 4 under wet friction conditions at 90℃, 120℃, and 150℃ are shown.

[0037] Figure 8 The friction coefficient curves for Example 5 under wet friction conditions at 90℃, 120℃, and 150℃ are shown.

[0038] Figure 9 The image shows the three-dimensional morphology of the worn surface under wet friction conditions at 90°C, 120°C, and 150°C in Example 1.

[0039] Figure 10 The image shows the three-dimensional morphology of the worn surface under wet friction conditions at 90°C, 120°C, and 150°C in Example 2.

[0040] Figure 11 The image shows the three-dimensional morphology of the worn surface under wet friction conditions at 90°C, 120°C, and 150°C in Example 4.

[0041] Figure 12The image shows the three-dimensional morphology of the worn surface under wet friction conditions at 90°C, 120°C, and 150°C in Example 5. Detailed Implementation

[0042] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0043] In the following examples, the Fe content was controlled at ≤0.1%, and other individual impurities were ≤0.05%.

[0044] Example 1 (Comparative Example):

[0045] This comparative example is a standard 6061 aluminum alloy, with the following chemical composition by mass percentage: Mg 1.02%, Si 0.61%, Cu 0.28%, Fe 0.08%, with the balance being Al and unavoidable impurities (Fe ≤ 0.1%, other individual impurities ≤ 0.05%).

[0046] The preparation method is as follows:

[0047] (1) Melting and casting: Using industrial pure aluminum ingots as raw materials, after melting at 760℃, Al-20Mg, Al-30Si and Al-50Cu intermediate alloys are added in sequence. After melting evenly, high-purity argon gas is introduced for refining for 10 minutes, slag is removed, and the mixture is left to stand for 15 minutes. The mixture is then poured into a metal mold preheated to 200℃ at 720℃ to obtain a cylindrical ingot with a diameter of 80mm and a diameter of 150mm.

[0048] (2) Homogenization treatment: Place the ingot in a box-type resistance furnace and keep it at 560℃ for 10 hours, then cool it to room temperature with the furnace.

[0049] (3) Solution treatment: After homogenization, the ingot is kept at 535℃ for 1.5 hours, and then immediately immersed in 25℃ water for quenching for 3 seconds.

[0050] (4) Cold rolling: The quenched billet is cold rolled at room temperature, with a total deformation of 6%.

[0051] (5) Aging treatment: The cold-rolled sheet is kept at 175℃ for 12 hours and then air-cooled to room temperature.

[0052] Example 2 (Comparative Example):

[0053] This comparative example is a 6061 aluminum alloy with only Sc added. Its chemical composition is the same as that of Example 1, with 0.18% Sc added (in the form of Al-2Sc master alloy).

[0054] The preparation method follows the same steps as in Example 1. However, in the melting and casting step, the Al-2Sc master alloy is added last after the other master alloys have been added and completely melted.

[0055] Example 3 (Comparative Example):

[0056] This comparative example is a 6061 aluminum alloy with only Zr added. Its chemical composition is the same as that of Example 1, with 0.25% Zr added (in the form of Al-4Zr master alloy).

[0057] The preparation method follows the same steps as in Example 1. However, in the melting and casting step, the Al-4Zr master alloy is added last after the other master alloys have been added and completely melted.

[0058] Example 4 (Comparative Example):

[0059] This comparative example is a 6061 aluminum alloy microalloyed with Sc and Zr but not cold-rolled. Its chemical composition is the same as in Example 1, with the addition of 0.18% Sc (added as an Al-2Sc master alloy) and 0.25% Zr (added as an Al-4Zr master alloy), and the remaining components are the same as in Example 1.

[0060] The preparation method steps are as follows:

[0061] (1) Melting and casting: Same as in Example 1, except that the Al-2Sc and Al-4Zr master alloys are added last.

[0062] (2) Homogenization treatment: Same as in Example 1.

[0063] (3) Solution treatment: Same as in Example 1.

[0064] (4) Aging treatment: Same as in Example 1, but without the cold rolling step. The billet after solution quenching is directly subjected to aging treatment at 175℃ for 12 hours, followed by air cooling.

[0065] Example 5 (Example of the present invention):

[0066] This embodiment describes a Sc / Zr composite microalloyed 6061 aluminum alloy prepared using a solution-cold rolling-aging process. Its chemical composition is identical to that of Example 4: based on Example 1, 0.18% Sc and 0.25% Zr are added.

[0067] The preparation method is as follows:

[0068] (1) Melting and casting: Using industrial pure aluminum ingots as raw materials, after melting at 760℃, Al-20Mg, Al-30Si and Al-50Cu intermediate alloys are added in sequence. After all the alloys are melted, Al-2Sc and Al-4Zr intermediate alloys are added. After stirring evenly, high-purity argon gas is introduced for refining for 10 minutes. The slag is removed, and the mixture is left to stand for 15 minutes. The mixture is then cast at 720℃ into a metal mold preheated to 200℃ to obtain a cylindrical ingot with a diameter of 80mm and a diameter of 150mm.

[0069] (2) Homogenization treatment: The ingot is placed in a box-type resistance furnace and held at 560℃ for 10 hours, then cooled to room temperature with the furnace. This step aims to eliminate dendrite segregation and make solute atoms such as Sc and Zr uniformly distributed in the α-Al matrix.

[0070] (3) Solution treatment: After homogenization, the ingot is kept at 535℃ for 1.5 hours, and then immediately immersed in 25℃ water for quenching for 3 seconds.

[0071] (4) Cold rolling: The billet after solution quenching is cold rolled at room temperature, with a total deformation of 6%.

[0072] (5) Aging treatment: The cold-rolled sheet is kept at 175°C for 12 hours and then air-cooled to room temperature to obtain the high-temperature wear-resistant aluminum alloy.

[0073] Performance testing and results analysis:

[0074] The following is a systematic performance test of the alloy samples prepared in Examples 1 to 5 above.

[0075] (a) Testing methods:

[0076] Hardness testing was performed using a Vickers hardness tester with a load of 200g and a holding time of 15 seconds. Five points were tested on each sample, and the average value was taken. Room temperature tensile properties were tested using a universal testing machine with a tensile rate of 1mm / min. The samples were plate-shaped tensile specimens with a gauge length of 25mm × 6mm × 2mm. Friction and wear properties were tested using a pin-disc friction and wear testing machine. The grinding pair consisted of GCr15 steel balls (6mm diameter, 60HRC hardness), with a load of 14N, a sliding speed of 7m / s, and a friction time of 30min. The ambient temperatures were set at 90℃, 120℃, and 150℃, controlled by a heating furnace. Under wet friction conditions, high-temperature lubricating oil was added to the friction interface at a rate of one drop every 30s. The wear amount was obtained by weighing the sample before and after wear using an analytical balance with an accuracy of 0.1mg. The three-dimensional morphology of the worn surface was measured using a white light interferometer to obtain the surface roughness Sa value. The microstructure was characterized using X-ray diffraction (XRD) and transmission electron microscopy (TEM).

[0077] (II) Microstructure Analysis:

[0078] Figure 1 The X-ray diffraction patterns are for Examples 2, 3, and 5. As can be seen from the figures, Example 2 (single addition of Sc) shows a diffraction peak of the Al3Sc phase at approximately 2θ 31°, and Example 3 (single addition of Zr) shows a diffraction peak of the Al3Zr phase at approximately 2θ 32°. Example 5 (Sc+Zr composite) shows only a single diffraction peak between Al3Sc and Al3Zr. The peak shift indicates the formation of an L12 type Al3(Sc,Zr) composite phase, and no individual Al3Sc, Al3Zr phases or brittle impurities were detected. This confirms that Sc and Zr synergistically form a core-shell structured Al3(Sc,Zr) composite precipitate, resulting in a pure alloy microstructure.

[0079] Figure 2 The figures show the metallographic structures of Examples 1 and 5. As can be seen from the figures, the grains in Example 1 (6061 matrix) are relatively coarse, with obvious dendritic segregation. In Example 5 (Sc+Zr composite alloy), after solution treatment, cold rolling, and aging, the grains are significantly refined, the microstructure is uniform and dense, and the equiaxed grain characteristics are obvious. This is because the Al3(Sc,Zr) nanoprecipitates act as effective heterogeneous nucleation sites during solidification and heat treatment, resulting in a strong grain refinement effect.

[0080] TEM observations revealed that the microstructure of the alloy in Example 5 contained high-density, diffusely distributed nanoprecipitates. These precipitates exhibited a typical core-shell structure: the core was enriched in Sc, and the outer shell in Zr, forming an L12 structure Al3(Sc,Zr) composite phase completely coherent with the α-Al matrix. The average particle size of these nanophases was 5–15 nm, with an interparticle spacing of 30–50 nm. Around the nanophases, high-density dislocation rings and dislocation entanglements introduced by cold rolling were observed. This dislocation configuration facilitates rapid diffusion of solute atoms during aging while effectively hindering dislocation movement, resulting in a significant dislocation strengthening effect.

[0081] (III) Mechanical properties:

[0082] Figure 3 The stress-strain curves for Examples 1, 2, 3, and 5 are shown. The mechanical property data of each alloy are summarized in Table 1.

[0083] Table 1. Room temperature mechanical properties of alloys in each example

[0084]

[0085] As shown in Table 1, the tensile strength of the alloy in Example 5 of this invention is increased by approximately 23%, the yield strength by approximately 21.6%, and the hardness by approximately 14.6% compared to the matrix alloy in Example 1. Compared to Example 2, which only added Sc, and Example 3, which only added Zr, Example 5 shows further improvements in both strength and hardness, demonstrating the composite strengthening effect of synergistic microalloying of Sc and Zr. Meanwhile, the elongation after fracture in Example 5 remains at 8.2%, meeting the basic requirements for plasticity in wear-resistant structural components.

[0086] Figure 4 The figures show the aging-hardness curves for Examples 1, 2, 3, and 5. As can be seen from the figures, Example 5 (Sc+Zr composite) reached its peak hardness after aging at 175℃ for 12 hours, and no significant decrease in hardness was observed over a longer aging period, demonstrating excellent thermal stability. In contrast, the matrix alloy of Example 1 had a lower peak hardness, which decreased significantly over time; the peak hardness of Examples 2 and 3 were intermediate, with thermal stability falling between the two. This indicates that the Al3(Sc,Zr) core-shell composite phase has stronger resistance to high-temperature coarsening than single Al3Sc or Al3Zr phases.

[0087] (iv) Friction and wear performance:

[0088] Table 2 summarizes the wear data of the alloys in each embodiment under different temperatures and wet friction conditions.

[0089] Table 2 Wear amount (mg) of alloys in each embodiment under wet friction conditions at different temperatures

[0090]

[0091] The following key conclusions can be drawn from the data in Table 2:

[0092] (1) High-temperature wear resistance: Under high-temperature wet friction conditions at 150℃, the wear amount of Example 5 (0.0042mg) was reduced by approximately 26.3% compared to the base alloy of Example 1 (0.0057mg), by approximately 12.5% ​​compared to Example 2 with only Sc addition (0.0048mg), and by approximately 19.2% compared to Example 3 with only Zr addition (0.0052mg). This indicates that the combined addition of Sc and Zr, along with the solution-cold rolling-aging process, can effectively improve the wear resistance of the alloy under high-temperature conditions.

[0093] (2) Suppression of mid-temperature adhesive wear: In Example 2 (with Sc added alone), the wear amount at 120℃ (0.0042mg) increased by 68% compared to that at 90℃ (0.0025mg), showing a significant deterioration in mid-temperature wear performance, which is the "mid-temperature adhesive wear sensitive zone". In contrast, the wear amount in Example 5 of this invention at 120℃ (0.0032mg) increased by only 60% compared to that at 90℃ (0.0020mg), a significantly smaller increase, and the absolute wear amount was much lower than that in Example 2. This indicates that the Al3(Sc,Zr) core-shell composite phase formed by the synergistic addition of Sc and Zr can effectively suppress the severe adhesive wear deterioration problem that occurs in the mid-temperature region of 120℃ with single Sc microalloying.

[0094] (3) Deformation strengthening effect: Comparing the wear data of Example 4 (T6 state, no cold rolling) and Example 5 (solution-cold rolling-aging state), it can be seen that the wear amount of Example 5 at the three temperature points of 90℃, 120℃ and 150℃ is lower than that of Example 4, which reflects the promoting effect of pre-deformation introduced by cold rolling on dislocation strengthening and aging precipitation.

[0095] Figures 5-8 The friction coefficient curves for Examples 1, 2, 4, and 5 under wet friction conditions at 90°C, 120°C, and 150°C are shown respectively. Figure 5 As in Example 1, the friction coefficient fluctuated greatly at 120°C and 150°C, indicating that the friction interface was unstable and an adhesion-peeling process occurred. Figure 6 Example 2 shows that the friction coefficient fluctuates violently and has a significant peak at 120°C, which is consistent with the phenomenon of the temperature-sensitive adhesive wear zone. Figure 7 In Example 4, the friction coefficient curve tends to be stable after Sc and Zr are combined. Figure 8 Example 5 shows that the friction coefficient is the most stable at all temperatures, with no obvious fluctuations, indicating that the optimal microstructure obtained by the solution-cold rolling-aging process enables the friction interface to form a stable load-bearing and lubrication structure.

[0096] Figures 9-12 The images show the three-dimensional morphology of the worn surfaces under wet friction conditions at 90℃, 120℃, and 150℃ for Examples 1, 2, 4, and 5, respectively. Table 3 summarizes the roughness Sa value and surface characteristics of the worn surfaces at 150℃.

[0097] Table 3. Surface roughness and characteristics of alloys in each embodiment at 150°C after wear.

[0098]

[0099] From Table 3 and Figures 9-12It can be visually observed that the wear surface of alloy in Example 5 is the smoothest, with shallow and uniformly distributed furrows and the least area of ​​adhesive peeling. This indicates that its wear mechanism has changed from "adhesive wear as the main characteristic" of 6061 matrix and single-addition Sc alloy to a benign wear mode "mainly oxidative wear and mild abrasive wear".

[0100] (V) Comprehensive discussion of wear mechanisms:

[0101] Based on the above analysis, the wear mechanisms of various alloys in different temperature ranges can be summarized as follows:

[0102] In the range of 90℃ to 150℃, the 6061 matrix alloy (Example 1) always exhibits a combination of abrasive wear and adhesive wear as the main mechanisms. As the temperature increases, the matrix softens more, the adhesion tendency increases, and the amount of wear increases significantly.

[0103] At low temperatures (<100°C), the Al3Sc nanophase effectively pins dislocations in alloys with a single addition of Sc (Example 2), resulting in abrasive wear. However, in the mid-temperature range (100~130°C), the pinning ability of Al3Sc relative to dislocations decreases. In addition, the uneven surface oxide film and poor stability lead to severe adhesive wear and material transfer, which is the phenomenon of the "mid-temperature adhesive wear sensitive zone".

[0104] The Sc+Zr composite microalloying of this invention, prepared by solution-cold rolling-aging process (Example 5), avoids severe adhesive wear in all temperature ranges. Its main mechanism is as follows: (1) The addition of Zr forms a core-shell structure Al3(Sc,Zr) composite phase. Since the diffusion rate of Zr atoms is much lower than that of Sc, this composite phase has excellent thermal stability and anti-roughening ability in the high temperature range of 120~150℃, and can continuously pin dislocations to maintain the high strength of the subsurface layer; (2) During the wear process, Zr participates in the formation of a dense mechanical mixed layer (third body layer) containing ZrO2 on the surface, which together with Al2O3 and MgO constitutes a stable isolation layer, effectively inhibiting direct metal contact and adhesive transfer between the wear pairs; (3) The high density dislocations introduced by cold rolling further enhance the shear deformation resistance of the subsurface layer, reduce the thickness of the plastic deformation layer, and make the surface oxide layer more uniform and have stronger adhesion.

[0105] In summary, this invention successfully constructed a high-density, high-stability Al3(Sc,Zr) nanoprecipitate phase by coupling the Sc and Zr synergistic microalloying composition design with a solution-cold rolling-aging process. With the addition of dislocation strengthening, it overcomes the defect of abnormal wear resistance degradation in the mid-temperature range caused by single Sc microalloying and achieves excellent high-temperature friction and wear resistance over a wide temperature range.

[0106] The above embodiments only illustrate several implementation methods of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the present invention.

Claims

1. A Sc / Zr composite microalloyed high-temperature and wear-resistant 6061 aluminum alloy, characterized in that, It consists of the following components by mass percentage: Sc 0.10~0.25%, Zr 0.15~0.35%, Mg 0.8~1.2%, Si 0.4~0.8%, Cu 0.15~0.40%, with the balance being Al and unavoidable impurities.

2. The aluminum alloy according to claim 1, characterized in that, The Sc content is 0.15~0.20%, the Zr content is 0.20~0.30%, and the mass ratio of Sc to Zr is 1:1.2~1:1.

5.

3. The aluminum alloy according to claim 2, characterized in that, The Sc content is 0.18%, and the Zr content is 0.25%.

4. A method for preparing the aluminum alloy according to any one of claims 1 to 3, characterized in that, Includes the following steps: (1) Prepare the ingredients according to the above-mentioned composition, melt at 750~780℃, refine and degas, and then cast into ingots at 710~730℃; (2) Homogenization treatment: The ingot is kept at 560℃ for 10 hours and then cooled with the furnace; (3) Solution treatment: Hold at 530~560℃ for 1~2 hours, then water quench; (4) Cold rolling: The billet after solution treatment is cold rolled, with a total deformation of 3% to 10%; (5) Aging treatment: Keep warm at 160~180℃ for 8~18 hours, then air cool.

5. The preparation method according to claim 4, characterized in that, The solution temperature in step (3) is 535±5℃ and the holding time is 1.5 hours; the cold rolling deformation in step (4) is 6±1%; the aging temperature in step (5) is 175±5℃ and the holding time is 12 hours.

6. The aluminum alloy according to any one of claims 1 to 3, characterized in that, Its microstructure contains an L12 structure Al3(Sc,Zr) nanoprecipitate phase that is completely coherent with the α-Al matrix. This precipitate phase has Sc enriched cores and Zr enriched shells, with an average particle size of 5~15 nm and a particle spacing of 30~50 nm.

7. The preparation method according to claim 4, characterized in that, After cold rolling in step (4) and aging treatment in step (5), the Al3(Sc,Zr) nanophase in the obtained alloy is surrounded by high-density dislocation rings and dislocation entanglements.

8. The aluminum alloy according to any one of claims 1 to 3, characterized in that, Its room temperature Vickers hardness is ≥85 HV, tensile strength is ≥360 MPa, and elongation after fracture is ≥8%.

9. The aluminum alloy according to any one of claims 1 to 3, characterized in that, Under wet friction conditions, when the grinding pair consists of GCr15 steel balls and the ambient temperature is 150°C, the wear is reduced by at least 25% compared to 6061 aluminum alloy without added Sc and Zr.

10. The aluminum alloy according to any one of claims 1 to 3, characterized in that, Under wet friction conditions, when the grinding pair consists of GCr15 steel balls and the ambient temperature is 120℃, the wear amount is reduced by at least 20% compared to 6061 aluminum alloy with only Sc added under the same conditions, and the wear mechanism is a combination of abrasive wear and oxidative wear.

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