A high-Fe recycled aluminum alloy with Mo and Sr microalloying control and its preparation method

Abstract

This invention discloses a high-Fe recycled aluminum alloy with Mo and Sr microalloying control and its preparation method, belonging to the field of aluminum alloy material technology. The high-Fe recycled aluminum alloy, by mass percentage, comprises the following components: Mg 0.9%-1.2%, Si 0.4%-0.8%, Cu 0.2%-0.5%, Mo 0.05%-0.4%, Sr 0.01%-0.1%, Fe 0.3%-1.1%, with the balance being Al and unavoidable impurities. The preparation method uses a recycled 6xxx series aluminum alloy with an Fe content of 0.3wt.%-1.1wt.% as the matrix, adds Mo and Sr elements for composite microalloying, and combines homogenization treatment, hot extrusion deformation, and heat treatment to form a high-Fe recycled aluminum alloy with a fibrous structure. This invention effectively overcomes the technical bottleneck of the difficulty in synergistically improving the "strength-plasticity-corrosion resistance" of high-Fe recycled aluminum.

Description

Technical Field

[0001] This invention belongs to the field of aluminum alloy materials technology, specifically relating to a high-Fe recycled aluminum alloy with Mo and Sr microalloying control and its preparation method. Background Technology

[0002] 6xxx series (Al-Mg-Si-Cu) alloys are widely used in automotive lightweighting, aerospace, and building structures due to their excellent formability, weldability, and corrosion resistance. With the deepening of the "dual-carbon" strategy, aluminum alloy recycling has become an inevitable trend, consuming only about 5% of the energy of primary aluminum production, demonstrating significant energy-saving and environmental advantages. However, the recycling of waste aluminum inevitably leads to the enrichment and accumulation of Fe impurities, which has become a core bottleneck restricting the high performance of recycled aluminum alloys. Fe has extremely low solid solubility in α-Al (approximately 0.05 wt.%), and excess Fe will form coarse β-AlFeSi phases with Al, Si, and other elements. These highly faceted, needle-like or lamellar β-Fe phases disrupt the matrix, induce stress concentration, and severely impair the elongation and fatigue properties of the alloy, especially its plasticity and corrosion resistance. Therefore, how to maintain the strength and improve the elongation of 6xxx series aluminum alloys under continuously increasing Fe content has become a key technical problem urgently needing to be solved in the field of aluminum recycling.

[0003] To address the performance degradation caused by high Fe impurities in recycled aluminum alloys, the mainstream engineering solution currently involves adding transition elements such as Mn and Cr for single chemical modification treatment. This promotes the transformation of the acicular β-Fe phase into the Chinese character-shaped or polygonal α-type Fe-rich phase, thereby weakening the destructive effect of harmful Fe on the aluminum matrix. However, this strategy has significant limitations: the Fe phase transformation is incomplete at high Fe contents; the α-type Fe-rich phase itself has high hardness and weak interfacial bonding, and may still become a crack initiation point; Mn diffuses rapidly, and the resulting dispersed phase is prone to coarsening, failing to achieve a long-term stable microstructure strengthening effect, and its ability to regulate microstructure stability is severely insufficient; excessive addition can also lead to a contradiction between strength and plasticity. Therefore, traditional single alloying strategies are no longer sufficient to meet performance requirements at high Fe contents.

[0004] To address the problems of incomplete Fe phase transformation, easy coarsening of dispersed phases, and difficulty in achieving both strength and plasticity under high Fe content using traditional single alloying strategies, there is an urgent need to study composite microalloying control methods for high Fe recycled aluminum alloys. These methods should synergistically drive the transformation of "harmful β phase to α-type Fe-rich phase" and "uniform precipitation of high-density dispersed phases" to achieve a synergistic effect of strength and plasticity and improved corrosion resistance in high Fe recycled aluminum. Summary of the Invention

[0005] To address the problems existing in the prior art, the present invention aims to provide a high-Fe recycled aluminum alloy with Mo and Sr microalloying control and its preparation method. Utilizing the extremely low diffusion coefficient of Mo in the aluminum matrix, this invention promotes the transformation of the harmful acicular β-Fe phase into the stable α-type Fe-rich phase, and induces high-density coherent α-Al. 22 (Fe, Mo) 6-8 The precipitation of Si4 dispersed phase; simultaneously, the effect of Sr on the size and number density of dispersed phase is used to further refine the dispersed phase and optimize its distribution uniformity; by controlling the homogenization heating rate, the dispersed phase is fully nucleated within the temperature range of the optimal nucleation window and coarsening is suppressed; combined with the hot extrusion deformation and crushing of residual coarse Fe-rich phase, a fibrous structure is formed; the Zener pinning effect of the coherent dispersed phase is used to suppress dynamic recovery and recrystallization; the resulting high Fe recycled aluminum alloy with Mo and Sr microalloying control significantly improves elongation and corrosion resistance while maintaining high strength.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] In a first aspect, the present invention provides a high-Fe recycled aluminum alloy with Mo and Sr microalloying control, comprising the following components by mass percentage: Mg 0.9%-1.2%, Si 0.4%-0.8%, Cu 0.2%-0.5%, Mo 0.05%-0.4%, Sr 0.01%-0.1%, Fe 0.3%-1.1%, with the balance being Al and unavoidable impurities.

[0008] Furthermore, the Mo and Sr microalloying-controlled high-Fe recycled aluminum alloy is a 6xxx series aluminum alloy material with a fibrous, non-recrystallized structure, a tensile strength of 292MPa-313MPa, an elongation of 13.9%-20.1%, an intergranular corrosion depth of 15.46μm-73.65μm, and a stress corrosion sensitivity coefficient of 3.2%-5.2%.

[0009] Secondly, this invention provides a method for preparing a high-Fe recycled aluminum alloy with Mo and Sr microalloying control. The method uses a recycled 6xxx series aluminum alloy with an Fe content of 0.3wt.%-1.1wt.% as the matrix, adds Mo and Sr elements for composite microalloying, and combines homogenization treatment, hot extrusion deformation and heat treatment to form a high-Fe recycled aluminum alloy with a fibrous structure.

[0010] Furthermore, the preparation method of the high-Fe recycled aluminum alloy with Mo and Sr micro-alloying control includes the following steps:

[0011] Smelting and casting:

[0012] Using recycled 6xxx series aluminum alloys as raw materials, and based on the design composition of high Fe recycled aluminum alloys controlled by Mo and Sr micro-alloying, Al-Mo master alloy and Al-Sr master alloy raw materials are added on the basis of the recycled 6xxx series aluminum alloy composition. Pure Cu, pure Mg, Al-Si master alloy and Al-Fe master alloy are selectively added as raw materials. After all raw materials are completely melted, they are stirred evenly, degassed and slag removed, and then cast into ingots.

[0013] Homogenization process:

[0014] Controlling the heating rate, the ingot is heated to the homogenization treatment temperature and then held at that temperature before being cooled in the furnace; the coarse needle-like β-AlFeSi phase in the alloy transforms into fishbone-like or spherical α-type Fe-rich phase, α-Al 22 (Fe, Mo) 6-8 High-density precipitation of Si4 coherent dispersed phase;

[0015] Hot extrusion deformation:

[0016] The homogenized ingot is hot-extruded and deformed, and the extrusion ratio is controlled to obtain the extruded profile.

[0017] Solution treatment:

[0018] The extruded profile is heated to the solution temperature and held at that temperature before being water quenched.

[0019] Timeliness processing:

[0020] The extruded profile after solution treatment is heated to the aging temperature and held at that temperature, then air-cooled to room temperature to obtain a high-Fe recycled aluminum alloy with Mo and Sr microalloying control.

[0021] Furthermore, in smelting and casting, the smelting temperature is 720℃-750℃.

[0022] Furthermore, in the homogenization process, the heating rate is controlled at 2℃ / min-6℃ / min, the homogenization temperature is 540℃-560℃, and the holding time is 12h-16h.

[0023] Furthermore, in the homogenization process, α-Al 22 (Fe, Mo) 6-8 The density of the Si4 coherent dispersed phase is ≥4.52 μm. -2 .

[0024] Furthermore, in hot extrusion deformation, the temperature of hot extrusion deformation is 470℃-510℃, and the extrusion ratio is 20-40.

[0025] Furthermore, in the solution treatment, the solution temperature is 540℃-560℃, and the holding time is 90min-120min.

[0026] Furthermore, during the aging process, the aging temperature is 170℃-190℃, and the holding time is 6h-9h.

[0027] Advantages and effects of the present invention:

[0028] 1. This invention overcomes the bottleneck of Fe impurity "poisoning" and provides a feasible microstructure control path for the high-performance utilization of high-Fe recycled aluminum. Through Mo and Sr composite microalloying, utilizing the extremely low diffusion coefficient of Mo in the aluminum matrix, it promotes the transformation of harmful needle-like β-Fe phase to stable α-type Fe-rich phase on the one hand, and induces high-density coherent α-Al on the other. 22 (Fe, Mo) 6- The precipitation of the 8Si4 dispersed phase; the control of the size and number density of the dispersed phase by Sr to further refine the dispersed phase and optimize its distribution uniformity; the control of the homogenization heating rate (2℃ / min-6℃ / min) to fully nucleate the dispersed phase in the temperature range of 350℃-450℃ and suppress coarsening; the formation of fibrous structure by combining the residual coarse Fe-rich phase after hot extrusion deformation and crushing; the Zener pinning effect of the coherent dispersed phase to suppress dynamic recovery and recrystallization, thereby significantly improving elongation and corrosion resistance while maintaining high strength.

[0029] 2. This invention systematically reveals for the first time the intrinsic mechanism by which Mo and Sr synergistically drive the transformation of "harmful β phase to α-type Fe-rich phase" and "uniform precipitation of high-density dispersed phase" in 6xxx wrought aluminum alloys with high Fe content. It effectively solves the technical problems of incomplete Fe phase transformation, easy coarsening of dispersed phase, and difficulty in balancing strength and plasticity under high Fe content in traditional single alloying strategies. It successfully breaks the dilemma of "high-speed rail is bound to be brittle" and realizes the synergistic effect of strength and plasticity and the improvement of corrosion resistance in high Fe recycled aluminum.

[0030] 3. Compared with 0Fe aluminum alloy, the high-Fe recycled aluminum alloy of the present invention, with Mo and Sr micro-alloying control, maintains a strength of over 292MPa without significant loss when the Fe content is as high as 0.7wt.%-1.0wt.%.

[0031] 4. Compared with existing 6xxx aluminum alloys with the same Fe content, the high Fe recycled aluminum alloy of the present invention, with Mo and Sr micro-alloying control, maintains equivalent or higher strength while increasing elongation by more than 40%.

[0032] 5. Compared with the existing 0.45Fe 6xxx aluminum alloy, the high Fe recycled aluminum alloy with Mo and Sr micro-alloying control of the present invention has an increased Fe content, but its corrosion resistance does not deteriorate with the increase of Fe content. On the contrary, it is significantly improved, breaking the dilemma that "the higher the iron content, the worse the corrosion performance".

[0033] 6. This invention effectively breaks through the technical bottleneck of the difficulty in synergistically improving the "strength-plasticity-corrosion resistance" of high-Fe recycled aluminum, and has significant industrial application value. Attached Figure Description

[0034] Figure 1 The stress-strain curves of alloys in Examples 1 to 4 and Comparative Examples 1 to 3 are shown.

[0035] Figure 2 This is a comparison chart of the mechanical properties of Examples 1, 2, and 4 with existing alloys of the same type;

[0036] Figure 3 Optical micrographs of intergranular corrosion of alloys from Examples 1 to 4 and Comparative Examples 1 to 3 are shown below, where (a) is an optical micrograph of Comparative Example 1; (b) is an optical micrograph of Comparative Example 2; (c) is an optical micrograph of Comparative Example 3; (d) is an optical micrograph of Example 1; (e) is an optical micrograph of Example 2; (f) is an optical micrograph of Example 3; and (g) is an optical micrograph of Example 4.

[0037] Figure 4 The images show the microstructures of alloys from Examples 1 to 4 and Comparative Examples 1 to 3, where (a) is the SEM and EDS image of Comparative Example 1; (b) is the SEM and EDS image of Comparative Example 2; (c) is the SEM and EDS image of Comparative Example 3; (d) is the SEM and EDS image of Example 1; (e) is the SEM image of Example 2; (f) is the SEM image of Example 3; and (g) is the SEM image of Example 4.

[0038] Figure 5 Transmission electron microscopy (TEM) images of the dispersed phase morphology and distribution inside the alloys of Examples 1 to 4 and Comparative Examples 1 to 3, wherein (a) is a TEM image of Comparative Example 1; (b) is a magnified view of a portion of the TEM image of Comparative Example 1; (c) is a TEM image of Comparative Example 2; (d) is a TEM image of Comparative Example 3; (e) is a TEM image of Example 1; (f) is a TEM image of Example 2; (g) is a TEM image of Example 3; and (h) is a TEM image of Example 4.

[0039] Figure 6 Statistical graphs showing the average size and number density of the dispersed phases in alloys of Examples 1 to 4 and Comparative Examples 1 to 3;

[0040] Figure 7The images show electron backscatter diffraction (EBSD) patterns of the alloy deformation structures of Examples 1 to 4 and Comparative Examples 1 to 3, where (a) is the EBSD pattern of Comparative Example 1; (b) is the EBSD pattern of Comparative Example 2; (c) is the EBSD pattern of Comparative Example 3; (d) is the EBSD pattern of Example 1; (e) is the EBSD pattern of Example 2; (f) is the EBSD pattern of Example 3; (g) is the EBSD pattern of Example 4; and (h) is a schematic diagram of the inverse pole figure coloring direction.

[0041] Figure 8 Transmission electron microscope (TEM) images of the morphology and distribution of the dispersed phase inside alloy 4. Detailed Implementation

[0042] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples.

[0043] A Mo and Sr microalloying-controlled high-Fe recycled aluminum alloy comprises, by mass percentage: Mg 0.9%-1.2%, Si 0.4%-0.8%, Cu 0.2%-0.5%, Mo 0.05%-0.4%, Sr 0.01%-0.1%, Fe 0.3%-1.1%, with the balance being Al and unavoidable impurities. This Mo and Sr microalloying-controlled high-Fe recycled aluminum alloy is a 6xxx series aluminum alloy material, possessing a fibrous, non-recrystallized structure, a tensile strength of 292 MPa-313 MPa, an elongation of 13.9%-20.1%, an intergranular corrosion depth of 15.46 μm-73.65 μm, and a stress corrosion susceptibility coefficient of 3.2%-5.2%. The synergistic effect of Fe with Mo and Sr is significantly enhanced during the homogenization process, inducing the precipitation of high-density coherent dispersed phases. This synergistic effect is significantly weakened when the Fe content is below 0.45 wt.%. When the Fe content is 0.7 wt.%-1.0 wt.%, the tensile strength of the high Fe recycled aluminum alloy regulated by Mo and Sr microalloying is 292 MPa-308 MPa, and the elongation is 13.9%-17.0%.

[0044] A method for preparing a high-Fe recycled aluminum alloy with Mo and Sr microalloying control is disclosed. The method uses a recycled 6xxx series aluminum alloy with an Fe content of 0.3wt.%-1.1wt.% as the matrix, adds Mo and Sr elements for composite microalloying, and combines homogenization treatment, hot extrusion deformation and heat treatment to form a high-Fe recycled aluminum alloy with fibrous structure.

[0045] The specific steps are as follows:

[0046] Smelting and casting:

[0047] Using recycled 6xxx series aluminum alloys as raw materials, and based on the design composition of high Fe recycled aluminum alloys controlled by Mo and Sr micro-alloying, Al-Mo master alloys and Al-Sr master alloys are added to the recycled 6xxx series aluminum alloy composition. Pure Cu, pure Mg, Al-Si master alloys, and Al-Fe master alloys are selectively added as raw materials. The mixture is heated to 720℃-750℃ in a melting furnace for melting. After all raw materials are completely melted, the mixture is stirred evenly, degassed, and slag removed, and then cast into ingots.

[0048] Homogenization process:

[0049] The ingot is heated to 540℃-560℃ at a heating rate of 2℃ / min-6℃ / min, held for 12h-16h, and then cooled in the furnace. This process promotes the transformation of the coarse needle-like β-AlFeSi phase in the alloy into a fishbone-like or spherical α-type Fe-rich phase, reducing the cutting of harmful phases against the matrix; it also induces high-density α-Al 22 (Fe, Mo) 6-8 Si4 coherent dispersion phase precipitation, α-Al 22 (Fe,Mo) 6-8 The density of the Si4 coherent dispersed phase is ≥4.52 μm. -2 The heating rate is controlled within the range of 2℃ / min to 6℃ / min, which can balance sufficient nucleation of the dispersed phase in the temperature range of 350℃-450℃ with core size control: when the heating rate is lower than 2℃ / min, the nucleation core is prone to excessive growth, resulting in coarsening of the dispersed phase; when the heating rate is higher than 6℃ / min, the optimal nucleation window of 350℃-450℃ is easily missed, resulting in insufficient number density.

[0050] Hot extrusion deformation:

[0051] The homogenized ingot is hot-extruded at 470℃-510℃, with the extrusion ratio controlled at 20-40, to obtain extruded profiles. This process not only breaks down residual coarse Fe-rich phases but also causes the internal grains of the alloy to be strongly elongated along the extrusion direction, forming a typical fibrous, non-recrystallized structure. At the same time, it promotes the further uniform distribution of dispersed phases, improving the strength and plasticity of the alloy.

[0052] Solution treatment:

[0053] After heating the extruded profile to 540℃-560℃, hold it at that temperature for 90min-120min, and then perform water quenching treatment.

[0054] Timeliness processing:

[0055] After solution treatment, the extruded profile is heated to 170℃-190℃ and held for 6h-9h, then air-cooled to room temperature to obtain a high-Fe recycled aluminum alloy with Mo and Sr micro-alloying control.

[0056] After solution treatment and aging, β" (Mg5Si6) and Q′ (Al5Cu2Mg8Si6) phases are fully precipitated, ultimately strengthening the alloy.

[0057] This invention employs a synergistic "harm elimination-gain" strategy: the combined addition of Mo and Sr promotes the transformation of coarse needle-like β-AlFeSi phases into fishbone-like or spherical α-type Fe-rich phases, eliminating harmful phases; and enhancement is achieved through coherent dispersed phases: Mo induces the transformation of incoherent dispersed phases into coherent α-Al. 22 (Fe, Mo) 6-8 The Si4 phase has a maximum number density of 8.84 μm. -2 Orowan reinforcement contributes up to 29.35 MPa; recrystallization inhibition and fibrous structure retention are achieved: high-density coherent dispersed phases inhibit dynamic / static recrystallization through Zener pinning effect, and retain fibrous structure; corrosion performance is synergistically improved: the morphological transformation of Fe-rich phase cuts off the grain boundary cathode network, and the fibrous structure forces cracks to change from intergranular to transgranular propagation, significantly reducing intergranular corrosion and stress corrosion sensitivity.

[0058] Example 1

[0059] A Mo and Sr microalloying-controlled high-Fe recycled aluminum alloy comprises, by mass percentage: Mg 1.07%, Si 0.58%, Cu 0.29%, Mo 0.14%, Sr 0.02%, Fe 0.49%, with the balance being Al and unavoidable impurities. This Mo and Sr microalloying-controlled high-Fe recycled aluminum alloy is a 6xxx series aluminum alloy material, possessing a fibrous, non-recrystallized structure, a tensile strength of 313 MPa, an elongation of 20.1%, an intergranular corrosion depth of 38.2 μm, and a stress corrosion susceptibility coefficient of 3.2%.

[0060] A method for preparing a high-Fe recycled aluminum alloy with Mo and Sr microalloying control includes the following steps:

[0061] Smelting and casting:

[0062] Using recycled 6xxx series aluminum alloys as raw materials, and based on the design composition of high Fe recycled aluminum alloys controlled by the above-mentioned Mo and Sr micro-alloying, Al-Mo master alloys and Al-Sr master alloys are added to the recycled 6xxx series aluminum alloy composition. Pure Cu, pure Mg, Al-Si master alloys, and Al-Fe master alloys are selectively added as raw materials. The mixture is heated to 740°C in a melting furnace for melting. After all raw materials are completely melted, the mixture is stirred evenly, degassed, and slag removed, and then cast into ingots.

[0063] Homogenization process:

[0064] The ingot was heated to 560℃ at a heating rate of 4℃ / min, held for 12 hours, and then cooled in the furnace. This process promoted the transformation of the coarse needle-like β-AlFeSi phase in the alloy into a fishbone-like or spherical α-type Fe-rich phase, and also induced a high-density α-Al phase. 22 (Fe,Mo) 6-8 Si4 coherent dispersion phase precipitation, α-Al 22 (Fe, Mo) 6-8 The density of the Si4 coherent dispersed phase is 4.52 μm. -2 .

[0065] Hot extrusion deformation:

[0066] The homogenized ingot was hot-extruded at 490℃, with the extrusion ratio controlled at 24, and extruded into a round bar with a diameter of 10mm.

[0067] Solution treatment:

[0068] The round bar is heated to 540℃ and held for 90 minutes, then quenched in water to room temperature.

[0069] Timeliness processing:

[0070] The solution-treated round bar was heated to 170℃ and held for 9 hours, then air-cooled to room temperature to obtain a high-Fe recycled aluminum alloy with Mo and Sr micro-alloying control.

[0071] Example 2

[0072] A Mo and Sr microalloying-controlled high-Fe recycled aluminum alloy comprises, by mass percentage: Mg 1.11%, Si 0.57%, Cu 0.28%, Mo 0.16%, Sr 0.02%, Fe 0.74%, with the balance being Al and unavoidable impurities. This Mo and Sr microalloying-controlled high-Fe recycled aluminum alloy is a 6xxx series aluminum alloy material, possessing a fibrous, non-recrystallized structure, a tensile strength of 308 MPa, an elongation of 16.99%, an intergranular corrosion depth of 73.19 μm, and a stress corrosion susceptibility coefficient of 3.6%.

[0073] A method for preparing a high-Fe recycled aluminum alloy with Mo and Sr microalloying control includes the following steps:

[0074] Smelting and casting:

[0075] Using recycled 6xxx series aluminum alloys as raw materials, and based on the design composition of high Fe recycled aluminum alloys controlled by the above-mentioned Mo and Sr micro-alloying, Al-Mo master alloys and Al-Sr master alloys are added to the recycled 6xxx series aluminum alloy composition. Pure Cu, pure Mg, Al-Si master alloys, and Al-Fe master alloys are selectively added as raw materials. The mixture is heated to 740°C in a melting furnace for melting. After all raw materials are completely melted, the mixture is stirred evenly, degassed, and slag removed, and then cast into ingots.

[0076] Homogenization process:

[0077] The ingot was heated to 560℃ at a heating rate of 4℃ / min, held at that temperature for 12 hours, and then cooled in the furnace. This process promoted the transformation of the coarse needle-like β-AlFeSi phase in the alloy into a fishbone-like or spherical α-type Fe-rich phase, and also induced a high-density α-Al phase. 22 (Fe,Mo) 6-8 Si4 coherent dispersion phase precipitation, α-Al 22 (Fe, Mo) 6-8 The density of the Si4 coherent dispersed phase is 5.39 μm. -2 .

[0078] Hot extrusion deformation:

[0079] The homogenized ingot was hot-extruded at 490℃, with the extrusion ratio controlled at 24, and extruded into a round bar with a diameter of 10mm.

[0080] Solution treatment:

[0081] The round bar is heated to 540℃ and held for 90 minutes, then quenched in water to room temperature.

[0082] Timeliness processing:

[0083] The solution-treated round bar was heated to 170℃ and held for 9 hours, then air-cooled to room temperature to obtain a high-Fe recycled aluminum alloy with Mo and Sr micro-alloying control.

[0084] Example 3

[0085] A Mo and Sr microalloying-controlled high-Fe recycled aluminum alloy comprises, by mass percentage: Mg 1.12%, Si 0.57%, Cu 0.28%, Mo 0.31%, Sr 0.02%, Fe 0.73%, with the balance being Al and unavoidable impurities. This Mo and Sr microalloying-controlled high-Fe recycled aluminum alloy is a 6xxx series aluminum alloy material, possessing a fibrous, non-recrystallized structure, a tensile strength of 301 MPa, an elongation of 13.9%, and an intergranular corrosion depth of 52.73 μm.

[0086] A method for preparing a high-Fe recycled aluminum alloy with Mo and Sr microalloying control includes the following steps:

[0087] Smelting and casting:

[0088] Using recycled 6xxx series aluminum alloys as raw materials, and based on the design composition of high Fe recycled aluminum alloys controlled by the above-mentioned Mo and Sr micro-alloying, Al-Mo master alloys and Al-Sr master alloys are added to the recycled 6xxx series aluminum alloy composition. Pure Cu, pure Mg, Al-Si master alloys, and Al-Fe master alloys are selectively added as raw materials. The mixture is heated to 740°C in a melting furnace for melting. After all raw materials are completely melted, the mixture is stirred evenly, degassed, and slag removed, and then cast into ingots.

[0089] Homogenization process:

[0090] The ingot was heated to 560℃ at a heating rate of 4℃ / min, held at that temperature for 12 hours, and then cooled in the furnace. This process promoted the transformation of the coarse needle-like β-AlFeSi phase in the alloy into a fishbone-like or spherical α-type Fe-rich phase, and also induced a high-density α-Al phase. 22 (Fe,Mo) 6-8 Si4 coherent dispersion phase precipitation, α-Al 22 (Fe, Mo) 6-8 The density of the Si4 coherent dispersed phase is 8.67 μm. -2 .

[0091] Hot extrusion deformation:

[0092] The homogenized ingot was hot-extruded at 490℃, with the extrusion ratio controlled at 24, and extruded into a round bar with a diameter of 10mm.

[0093] Solution treatment:

[0094] The round bar is heated to 540℃ and held for 90 minutes, then quenched in water to room temperature.

[0095] Timeliness processing:

[0096] The solution-treated round bar was heated to 170℃ and held for 9 hours, then air-cooled to room temperature to obtain a high-Fe recycled aluminum alloy with Mo and Sr micro-alloying control.

[0097] Example 4

[0098] A Mo and Sr microalloying-controlled high-Fe recycled aluminum alloy comprises, by mass percentage: Mg 1.13%, Si 0.62%, Cu 0.29%, Mo 0.28%, Sr 0.02%, Fe 1.08%, with the balance being Al and unavoidable impurities. This Mo and Sr microalloying-controlled high-Fe recycled aluminum alloy is a 6xxx series aluminum alloy material, possessing a fibrous, non-recrystallized structure, a tensile strength of 292 MPa, an elongation of 14.3%, an intergranular corrosion depth of 73.65 μm, and a stress corrosion susceptibility coefficient of 5.2%.

[0099] A method for preparing a high-Fe recycled aluminum alloy with Mo and Sr microalloying control includes the following steps:

[0100] Smelting and casting:

[0101] Using recycled 6xxx series aluminum alloys as raw materials, and based on the design composition of high Fe recycled aluminum alloys controlled by the above-mentioned Mo and Sr micro-alloying, Al-Mo master alloys and Al-Sr master alloys are added to the recycled 6xxx series aluminum alloy composition. Pure Cu, pure Mg, Al-Si master alloys, and Al-Fe master alloys are selectively added as raw materials. The mixture is heated to 740°C in a melting furnace for melting. After all raw materials are completely melted, the mixture is stirred evenly, degassed, and slag removed, and then cast into ingots.

[0102] Homogenization process:

[0103] The ingot was heated to 560℃ at a heating rate of 4℃ / min, held at that temperature for 12 hours, and then cooled in the furnace. This process promoted the transformation of the coarse needle-like β-AlFeSi phase in the alloy into a fishbone-like or spherical α-type Fe-rich phase, and also induced a high-density α-Al phase. 22 (Fe,Mo) 6-8 Si4 coherent dispersion phase precipitation, α-Al 22 (Fe, Mo) 6-8 The density of the Si4 coherent dispersed phase is 8.84 μm. -2 .

[0104] Hot extrusion deformation:

[0105] The homogenized ingot was hot-extruded at 490℃, with the extrusion ratio controlled at 24, and extruded into a round bar with a diameter of 10mm.

[0106] Solution treatment:

[0107] The round bar is heated to 540℃ and held for 90 minutes, then quenched in water to room temperature.

[0108] Timeliness processing:

[0109] The solution-treated round bar was heated to 170℃ and held for 9 hours, then air-cooled to room temperature to obtain a high-Fe recycled aluminum alloy with Mo and Sr micro-alloying control.

[0110] Example 5

[0111] A Mo and Sr microalloying-controlled high-Fe recycled aluminum alloy comprises, by mass percentage: Mg 0.91%, Si 0.39%, Cu 0.5%, Mo 0.05%, Sr 0.1%, Fe 0.43%, with the balance being Al and unavoidable impurities. This Mo and Sr microalloying-controlled high-Fe recycled aluminum alloy is a 6xxx series aluminum alloy material, possessing a fibrous, non-recrystallized structure, a tensile strength of 317 MPa, and an elongation of 16.1%.

[0112] A method for preparing a high-Fe recycled aluminum alloy with Mo and Sr microalloying control includes the following steps:

[0113] Smelting and casting:

[0114] Using recycled 6xxx series aluminum alloys as raw materials, and based on the design composition of high Fe recycled aluminum alloys controlled by the above-mentioned Mo and Sr micro-alloying, Al-Mo master alloys and Al-Sr master alloys are added to the recycled 6xxx series aluminum alloy composition. Pure Cu, pure Mg, Al-Si master alloys, and Al-Fe master alloys are selectively added as raw materials. The mixture is heated to 740°C in a melting furnace for melting. After all raw materials are completely melted, the mixture is stirred evenly, degassed, and slag removed, and then cast into ingots.

[0115] Homogenization process:

[0116] The ingot was heated to 540°C at a heating rate of 6°C / min, held at that temperature for 16 hours, and then cooled in the furnace.

[0117] Hot extrusion deformation:

[0118] The homogenized ingot is hot-extruded at 470℃, and the extrusion ratio is controlled at 40 to extrude it into a round bar with a diameter of 10mm.

[0119] Solution treatment:

[0120] The round bar is heated to 540℃ and held for 90 minutes, then quenched in water to room temperature.

[0121] Timeliness processing:

[0122] The solution-treated round bar was heated to 170℃ and held for 9 hours, then air-cooled to room temperature to obtain a high-Fe recycled aluminum alloy with Mo and Sr micro-alloying control.

[0123] Example 6

[0124] A Mo and Sr microalloying-controlled high-Fe recycled aluminum alloy comprises, by mass percentage: Mg 1.21%, Si 0.80%, Cu 0.20%, Mo 0.40%, Sr 0.05%, Fe 0.44%, with the balance being Al and unavoidable impurities. This Mo and Sr microalloying-controlled high-Fe recycled aluminum alloy is a 6xxx series aluminum alloy material, possessing a fibrous, non-recrystallized structure, a tensile strength of 311 MPa, and an elongation of 18.3%.

[0125] A method for preparing a high-Fe recycled aluminum alloy with Mo and Sr microalloying control, comprising the following steps:

[0126] Smelting and casting:

[0127] Using recycled 6xxx series aluminum alloys as raw materials, and based on the design composition of high Fe recycled aluminum alloys controlled by the above-mentioned Mo and Sr micro-alloying, Al-Mo master alloys and Al-Sr master alloys are added to the recycled 6xxx series aluminum alloy composition. Pure Cu, pure Mg, Al-Si master alloys, and Al-Fe master alloys are selectively added as raw materials. The mixture is heated to 740°C in a melting furnace for melting. After all raw materials are completely melted, the mixture is stirred evenly, degassed, and slag removed, and then cast into ingots.

[0128] Homogenization process:

[0129] The ingot was heated to 550°C at a heating rate of 5°C / min, held at that temperature for 14 hours, and then cooled with the furnace.

[0130] Hot extrusion deformation:

[0131] The homogenized ingot was hot-extruded at 510℃, and the extrusion ratio was controlled at 30 to extrude it into a round bar with a diameter of 10mm.

[0132] Solution treatment:

[0133] The round bar is heated to 540℃ and held for 90 minutes, then quenched in water to room temperature.

[0134] Timeliness processing:

[0135] The solution-treated round bar was heated to 170℃ and held for 9 hours, then air-cooled to room temperature to obtain a high-Fe recycled aluminum alloy with Mo and Sr micro-alloying control.

[0136] Comparative Example 1

[0137] A low-Fe content Al-Mg-Si-Cu alloy differs from Example 1 in that it does not contain Mo or Sr and has a lower Fe content. By mass percentage, it comprises the following components: Mg 1.10%, Si 0.58%, Cu 0.29%, Fe 0.11%, with the balance being Al and unavoidable impurities.

[0138] Comparative Example 2

[0139] A high Fe content Al-Mg-Si-Cu alloy, which differs from Example 1 in that it does not contain Mo or Sr, and comprises the following components by mass percentage: Mg 1.07%, Si 0.58%, Cu 0.29%, Fe 0.49%, with the balance being Al and unavoidable impurities.

[0140] Comparative Example 3

[0141] A high Fe content Al-Mg-Si-Cu alloy controlled by Mo microalloying differs from Example 1 in that it uses only Mo for single alloying and comprises the following components by mass percentage: Mg 1.10%, Si 0.56%, Cu 0.29%, Fe 0.50%, Mo 0.14%, with the balance being Al and unavoidable impurities.

[0142] Comparative Example 4

[0143] A low-Fe content Al-Mg-Si-Cu alloy with Mo,Sr microalloying control, differs from Example 1 in that the Fe content is 0.20% (lower), and by mass percentage comprises the following components: Mg 1.07%, Si 0.51%, Cu 0.3%, Fe 0.20%, Mo 0.17%, Sr 0.02%, with the balance being Al and unavoidable impurities.

[0144] Performance Analysis:

[0145] The alloys of Examples 1 to 4 and Comparative Examples 1 to 3 were subjected to slow strain rate tensile properties and corrosion susceptibility tests under the same test environment. The test results are shown in Table 1.

[0146] Table 1. Slow strain rate tensile properties and stress corrosion susceptibility index of alloys in Examples 1 to 4 and Comparative Examples 1 to 3

[0147]

[0148] Under air testing conditions, the stress-strain curves of the alloys in Examples 1 to 4 and Comparative Examples 1 to 3 are as follows: Figure 1As shown in Table 1, it can be seen that although the high Fe content of the Mo and Sr microalloying controlled high Fe recycled aluminum alloy of the present invention is high, its mechanical properties are not significantly lost, and its corrosion performance is better than that of Comparative Example 2 (high Fe content Al-Mg-Si-Cu alloy) and Comparative Example 3 (Mo microalloying controlled high Fe content Al-Mg-Si-Cu alloy). In particular, under the same iron content (0.45Fe), the elongation of the high-Fe recycled aluminum alloy with Mo and Sr microalloying control in Example 1 was significantly improved (approximately 22%) compared to Comparative Example 2 (high-Fe content Al-Mg-Si-Cu alloy), and also improved compared to Comparative Example 3 (high-Fe content Al-Mg-Si-Cu alloy with Mo microalloying control). At the same time, the stress corrosion sensitivity coefficient (3.2%) of the high-Fe recycled aluminum alloy with Mo and Sr microalloying control in Example 1 was significantly lower than that of Comparative Example 2 (high-Fe content Al-Mg-Si-Cu alloy) (7.3%) and Comparative Example 3 (high-Fe content Al-Mg-Si-Cu alloy with Mo microalloying control) (5.5%), and even lower than that of Comparative Example 1 (low-Fe content Al-Mg-Si-Cu alloy). This fully demonstrates that the corrosion performance of the high-Fe recycled aluminum alloy with Mo and Sr microalloying control in this invention did not deteriorate due to the increase in Fe content. Furthermore, the stress corrosion sensitivity coefficient (3.6%) of the high-Fe recycled aluminum alloy with 0.7Fe Mo and Sr microalloying in Example 2 was significantly lower than that of the 0.45Fe Al-Mg-Si-Cu alloy in Comparative Example 2, reaching a level comparable to the 0Fe alloy given in Comparative Example 1. In particular, the stress corrosion sensitivity coefficient (5.2%) of the high-Fe recycled aluminum alloy with 1.0Fe Mo and Sr microalloying in Example 4 was lower than that of the 0.45Fe Al-Mg-Si-Cu alloy in Comparative Example 2 and the 0.45Fe Mo microalloying Al-Mg-Si-Cu alloy in Comparative Example 3. Although the Fe content of Comparative Examples 2 and 3 was lower, the high-Fe recycled aluminum alloy controlled by Mo and Sr microalloying in this invention exhibited superior corrosion performance.

[0149] The mechanical properties of the high-Fe recycled aluminum alloy with Mo and Sr micro-alloying control of this invention are further compared with those of existing alloys of the same type, such as... Figure 2 As shown, when the Fe content is the same or similar, Examples 1 and 2 of the present invention exhibit better tensile strength, while the elongation is significantly increased, with an increase of more than 40%.

[0150] Intergranular corrosion in Examples 1 to 4 and Comparative Examples 1 to 3 was observed using an optical microscope. Figure 3As shown, under the same iron content (0.45Fe), the maximum intergranular corrosion depth of the high-Fe recycled aluminum alloy with Mo and Sr microalloying control in Example 1 is only about 24% and 40% of that of the high-Fe Al-Mg-Si-Cu alloy in Comparative Example 2 and the Mo microalloying control Al-Mg-Si-Cu alloy in Comparative Example 3, respectively. Moreover, compared with the low-iron-content (0.11Fe) Al-Mg-Si-Cu alloy in Comparative Example 1, the intergranular corrosion situation has not worsened. Although the maximum intergranular corrosion depth in Example 1 is 38.20 μm, the intergranular corrosion depth measured at other locations is even shallower than that in Comparative Example 1. Furthermore, the intergranular corrosion depth of the high-Fe recycled aluminum alloys regulated by Mo and Sr microalloying in Examples 2 to 4 ranged from 52.73 μm to 73.65 μm. Although the Fe content was further increased compared to Comparative Examples 2 and 3, the intergranular corrosion depth was significantly shallower than that of Comparative Examples 2 and 3. This indicates that the regulation effect of Mo and Sr was significant, and the intergranular corrosion did not deteriorate due to the increase in Fe content.

[0151] The above analysis shows that the high-Fe recycled aluminum alloy with Mo and Sr microalloying control of the present invention can achieve a synergistic improvement in strength, plasticity and corrosion resistance.

[0152] Microstructure analysis:

[0153] The microstructure of the alloys in Examples 1 to 4 and Comparative Examples 1 to 3 was observed using SEM, such as... Figure 4 As shown in (a) and 4(b), it can be seen that without the addition of Mo, the Fe-rich phase mainly exists in the form of needle-like β-AlFeSi phase; Figure 4 As shown in (c), after the addition of Mo, some of the needle-like β-AlFeSi phases underwent a morphological transformation, forming a skeletal α-AlFeSi phase. Figure 4 As shown in (d), after the introduction of Mo and Sr elements, trace amounts of Mo are dissolved in the iron phase, and Mo exhibits a highly overlapping distribution in the Fe-rich phase, confirming that Mo participates in the nucleation and growth of the α phase. Sr elements are almost not enriched in the iron phase and are uniformly distributed; further combined with Figure 4 (e) to Figure 4 (g) shows that Sr has a significant refining effect on the Fe-rich phase, making the α-AlFeSi phase smaller and more dispersed, while inhibiting the formation of coarse, continuous Fe-rich phases. This indicates that the added Mo and Sr elements promote the transformation of the β-AlFeSi phase to the α-AlFeSi phase during the homogenization process, changing its original sharp needle-like shape into a more rounded skeletal shape, effectively regulating the morphology of the Fe-rich phase towards a more beneficial direction.

[0154] The morphology and distribution characteristics of the dispersed phases inside the alloys of Examples 1 to 4 and Comparative Examples 1 to 3 were observed using a TEM microscope, such as... Figure 5 As shown, the dispersed phases of alloys with different compositions exhibit different characteristics, thus clarifying the differences in the roles and relative importance of the main elements. Figure 5 The average size and number density of the dispersed phases within the alloy were statistically analyzed, as shown in Table 2 and... Figure 6 As shown. In the 0Fe (Comparative Example 1) alloy, as Figure 5 As shown in (a) and 5(b), it can be seen that it exhibits elongated dispersed phases (β-Al9Fe2Si) and short rod-shaped dispersed phases (α-Al). 12 Fe3Si has an adverse effect on the mechanical properties of the alloy, and the visible dispersed phase has a large size (average 0.89 μm) and an extremely low number density (0.13 μm). -2 This is attributed to insufficient nucleation rate under low Fe content. For example... Figure 5 As shown in (c), after adding 0.45Fe (Comparative Example 2), the average size of the dispersed phase was significantly reduced to 0.37 μm, and the number density was increased to 0.43 μm. -2 This indicates that the addition of Fe effectively promoted the precipitation and refinement of the dispersed phase; further addition of 0.15 Mo (Comparative Example 3) further improved the precipitation and refinement of the dispersed phase. Figure 5 As shown in (d), the number of dispersed phases increased significantly, with the number density increasing dramatically to 4.40 μm. -2 The average size decreased to 0.07 μm, confirming that Mo has a significant promoting effect on the precipitation of dispersed phases and is more conducive to refining their size. Adding 0.15 Mo + 0.02 Sr (Example 1) resulted in... Figure 5 As shown in (e), the coherent diffuse phase (α-Al) is visible. 22 (Fe, Mo) 6-8 The size distribution of Si4 is more uniform than that of Comparative Example 3, with the maximum size decreasing from 0.33 μm to 0.27 μm, and the dispersed phase number density also slightly increasing to 4.52 μm. -2 This demonstrates the homogenizing and refining effect of Sr, but its direct promoting effect on number density is limited. Under the same Mo and Sr contents, when the Fe content increases from 0.45% to 0.7% (Example 2), as... Figure 5 As shown in (f), the number of coherent dispersed phases further increases, and the number density of dispersed phases increases from 4.52 μm. -2 Slightly increased to 5.39 μm -2 The average size decreased from 0.06 μm to 0.05 μm; when the Fe content was further increased to 1% (Example 4), such as Figure 5 As shown in (h), the number of coherent dispersed phases continues to increase, with the number density increasing to 8.84 μm. -2However, the average size rebounded to 0.07 μm, indicating that the effect of excess Fe on promoting the precipitation of the dispersed phase was close to saturation and easily led to coarsening. In contrast, at a similar Fe content (0.7%), when the Mo content was increased from 0.15% to 0.3% (Example 3), such as Figure 5 As shown in (g), the number of coherent dispersed phases increased significantly compared to Example 2, with the number density increasing from 5.39 μm. -2 Increased to 8.67 μm -2 The average size decreased to 0.04 μm. As can be seen from the above, the number density of dispersed phases increases with increasing Fe and Mo content, and the effect of Mo is more pronounced than that of Fe, fully demonstrating Mo's promoting effect on dispersed phase precipitation and its key role in regulating dispersed phases.

[0155] Table 2. Statistical table of average size and number density of dispersed phases inside alloys in Examples 1 to 4 and Comparative Examples 1 to 3.

[0156]

[0157] The microstructure characteristics of the alloys in Examples 1 to 4 and Comparative Examples 1 to 3 were observed using EBSD, such as... Figure 7 As shown, the 0Fe alloy (Comparative Example 1) underwent severe dynamic recovery and recrystallization during hot deformation, resulting in significant grain coarsening and exhibiting a typical equiaxed grain structure. After adding 0.45Fe (Comparative Example 2), the dynamic recovery and recrystallization process was slightly suppressed, and the proportion of recovered and recrystallized grains decreased, but the effect was not significant. When Mo was further added (Comparative Example 3), the alloy exhibited a fibrous grain structure along the extrusion direction. After the combined addition of Mo and Sr (Examples 1 to 4), the alloy exhibited a nearly completely fibrous grain structure along the extrusion direction. This indicates that the dynamic recovery and recrystallization process of the high-Fe recycled aluminum alloy regulated by Mo and Sr microalloying of this invention was effectively suppressed during hot deformation; moreover, this suppression effect became more significant with increasing Fe content.

[0158] To further verify the synergistic effect of Fe, Mo, and Sr during homogenization treatment on the influence of iron content, the dispersed phase situation inside the alloy of Comparative Example 4 (a low-Fe content Al-Mg-Si-Cu alloy with Mo and Sr microalloying control) was observed by TEM. Figure 8 As shown, the number of its main dispersed phases is relatively small, significantly less than the number of dispersed phases in the high Fe content Al-Mg-Si-Cu alloys regulated by Mo and Sr microalloying in Examples 1 to 4 of this invention. This is because when the Fe content increases, its synergistic effect with Mo and Sr during the homogenization process is significantly enhanced, inducing the precipitation of high-density coherent dispersed phases. This verifies that the synergistic effect is significantly weakened when the Fe content is below 0.45 wt.%.

Claims

1. A high-Fe recycled aluminum alloy with Mo and Sr microalloying control, characterized in that, The composition, by mass percentage, includes the following components: Mg 0.9%-1.2%, Si 0.4%-0.8%, Cu 0.2%-0.5%, Mo 0.05%-0.4%, Sr 0.01%-0.1%, Fe 0.3%-1.1%, with the balance being Al and unavoidable impurities.

2. The high-Fe recycled aluminum alloy with Mo and Sr microalloying control as described in claim 1, characterized in that, The Mo and Sr microalloying-controlled high-Fe recycled aluminum alloy is a 6xxx series aluminum alloy material with a fibrous, non-recrystallized structure, a tensile strength of 292MPa-313MPa, an elongation of 13.9%-20.1%, an intergranular corrosion depth of 15.46μm-73.65μm, and a stress corrosion sensitivity coefficient of 3.2%-5.2%.

3. A method for preparing a high-Fe recycled aluminum alloy with Mo and Sr microalloying control as described in claim 1, characterized in that, Using recycled 6xxx series aluminum alloys with an Fe content of 0.3wt.%-1.1wt.% as the matrix, Mo and Sr elements are added for composite microalloying, combined with homogenization treatment, hot extrusion deformation and heat treatment, to form a high Fe recycled aluminum alloy with a fibrous structure.

4. The method for preparing high-Fe recycled aluminum alloy with Mo and Sr microalloying control as described in claim 3, characterized in that, The method for preparing the Mo and Sr microalloying-controlled high-Fe recycled aluminum alloy includes the following steps: Smelting and casting: Using recycled 6xxx series aluminum alloys as raw materials, and based on the design composition of high Fe recycled aluminum alloys controlled by Mo and Sr micro-alloying, Al-Mo master alloy and Al-Sr master alloy raw materials are added on the basis of the recycled 6xxx series aluminum alloy composition. Pure Cu, pure Mg, Al-Si master alloy and Al-Fe master alloy are selectively added as raw materials. After all raw materials are completely melted, they are stirred evenly, degassed and slag removed, and then cast into ingots. Homogenization process: Controlling the heating rate, the ingot is heated to the homogenization treatment temperature and then held at that temperature before being cooled in the furnace; the coarse needle-like β-AlFeSi phase in the alloy transforms into fishbone-like or spherical α-type Fe-rich phase, α-Al 22 (Fe, Mo) 6-8 High-density precipitation of Si4 coherent dispersed phase; Hot extrusion deformation: The homogenized ingot is hot-extruded and deformed, and the extrusion ratio is controlled to obtain the extruded profile. Solution treatment: The extruded profile is heated to the solution temperature and held at that temperature before being water quenched. Timeliness processing: The extruded profile after solution treatment is heated to the aging temperature and held at that temperature, then air-cooled to room temperature to obtain a high-Fe recycled aluminum alloy with Mo and Sr microalloying control.

5. The method for preparing high-Fe recycled aluminum alloy with Mo and Sr microalloying control as described in claim 4, characterized in that, In smelting and casting, the smelting temperature is 720℃-750℃.

6. The method for preparing high-Fe recycled aluminum alloy with Mo and Sr microalloying control as described in claim 4, characterized in that, During the homogenization process, the heating rate was controlled at 2℃ / min-6℃ / min, the homogenization temperature was 540℃-560℃, and the holding time was 12h-16h.

7. The method for preparing high-Fe recycled aluminum alloy with Mo and Sr microalloying control as described in claim 4, characterized in that, In the homogenization process, α-Al 22 (Fe, Mo) 6-8 The density of the Si4 coherent dispersed phase is ≥4.52 μm. -2 .

8. The method for preparing high-Fe recycled aluminum alloy with Mo and Sr microalloying control as described in claim 4, characterized in that, In hot extrusion deformation, the temperature is 470℃-510℃ and the extrusion ratio is 20-40.

9. The method for preparing high-Fe recycled aluminum alloy with Mo and Sr microalloying control as described in claim 4, characterized in that, During the solution treatment, the solution temperature is 540℃-560℃, and the holding time is 90min-120min.

10. The method for preparing high-Fe recycled aluminum alloy with Mo and Sr microalloying control as described in claim 4, characterized in that, During the aging process, the aging temperature is 170℃-190℃, and the holding time is 6h-9h.

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