Layered heterostructure aluminum-silicon alloy workpiece and preparation method thereof

Abstract

The invention discloses a layered heterostructure aluminum-silicon alloy part and a preparation method thereof, and relates to the technical field of high-quality aluminum alloy plates, the aluminum-silicon alloy part comprises a layered heterostructure with alternate soft areas and hard areas, each hard area comprises an aluminum-silicon alloy matrix layer, each soft area comprises a pure aluminum reinforcing layer, and each pure aluminum reinforcing layer comprises an aluminum-silicon alloy matrix layer. And a metallurgical bonding interface is formed between the aluminum-silicon alloy matrix layer and the pure aluminum enhancement layer. The high-strength and high-plasticity aluminum-silicon alloy workpiece with the soft and hard area alternate layered heterostructure is obtained by rheoforming the aluminum-silicon alloy semi-solid slurry and alternately rolling and compounding the aluminum-silicon alloy semi-solid slurry and the pure aluminum layer.

Description

Technical Field

[0001] This invention relates to the field of high-quality aluminum alloy sheet technology, specifically to a layered heterostructure aluminum-silicon alloy part and its preparation method. Background Technology

[0002] Aluminum alloys are widely used in sheet metal production due to their high strength-to-weight ratio, achieving lightweighting and improving energy efficiency while reducing emissions. Al-Si alloys are high-strength, lightweight die-cast aluminum alloys for structural components. As heat-treatable alloys, improvements in the strength and ductility of cast aluminum-Si alloys are primarily achieved through optimizing heat treatment processes. However, current research on heat treatment of Al-Si alloys mainly focuses on the traditional T6 process. Although prolonged high-temperature heat treatment can mitigate the adverse effects of the intergranular eutectic Si phase and the brittle acicular β-Al5FeSi phase to some extent, it lacks advantages in terms of effectiveness, energy consumption, and production efficiency. Moreover, it often requires a significant sacrifice in strength to achieve only a slight improvement in ductility.

[0003] Semi-solid machining, as a novel metal forming method, combines the advantages of traditional forging and casting. Compared to forging, semi-solid machining can produce complex parts with near-net-shapes; while compared to traditional casting, it can produce structural parts with excellent mechanical properties.

[0004] Furthermore, the current requirements for metallic materials have shifted to achieving high strength and high ductility without sacrificing other properties. Heterogeneous metallic materials, due to their superior mechanical and physical properties, have rapidly become a major research focus. Heterogeneous (HS) materials are characterized by non-uniform regions with differences in mechanical or physical properties. During large plastic deformation, the differences in microscale and mechanical properties between soft and hard regions lead to heterogeneous deformation-induced strengthening stress (HDI) between them. This, in turn, excites a higher density of geometrically necessary dislocations, generating continuous heterogeneous deformation-induced strengthening stress, thus achieving a synergistic improvement in strength and ductility. In terms of mechanical properties, they far surpass those of traditional homogeneous materials. However, the preparation of heterogeneous alloys using traditional processes typically requires long-flow thermomechanical processing. Such lengthy processes result in complex, inefficient, and costly composition optimization and microstructure control.

[0005] There is a lack of research on the preparation of heterostructured aluminum-silicon alloys by leveraging the advantages of rheocasting and combining multi-stage rolling with short-time heat treatment. Therefore, there is an urgent need for heterostructure preparation technology with simple equipment structure, efficient preparation process, low cost, and significant prospects for industrial application. Summary of the Invention

[0006] This invention provides a layered heterostructure aluminum-silicon alloy part and its preparation method. The layered heterostructure with a metallurgical bonding interface is formed by alternately stacking aluminum-silicon alloy layers and pure aluminum layers. The aluminum-silicon alloy layer, as a hard region, works synergistically with the soft region of pure aluminum to generate a heterogeneous deformation-induced strengthening effect, thereby solving the technical problem that it is difficult to synergistically improve the strength and plasticity of cast aluminum-silicon alloys.

[0007] The present invention is achieved through the following technical solution: In a first aspect, the present invention provides a layered heterostructure aluminum-silicon alloy part, comprising a layered heterostructure with alternating soft and hard regions, wherein the hard region comprises an aluminum-silicon alloy matrix layer, the soft region comprises a pure aluminum reinforcement layer, and a metallurgical bonding interface is formed between the aluminum-silicon alloy matrix layer and the pure aluminum reinforcement layer.

[0008] As an optional implementation, the layered heterostructure comprises two aluminum-silicon alloy substrate layers sandwiching a pure aluminum reinforcing layer to form a "sandwich" structure, wherein the pure aluminum reinforcing layer is located between the two aluminum-silicon alloy substrate layers.

[0009] As an optional embodiment, the aluminum-silicon alloy substrate layer is composed of elements comprising the following mass percentages: Si: 5.50~7.50 wt.%; Mg: 0.25~0.55 wt.%; Fe: 0.05~0.10 wt.%; Total impurities ≤ 0.10 wt.%, balance is Al.

[0010] Secondly, embodiments of the present invention provide a method for preparing a layered heterostructure aluminum-silicon alloy part, comprising the following steps: S1: Melt aluminum-silicon alloy raw materials and prepare them into a semi-solid slurry; S2: The semi-solid slurry is rheoformed into an aluminum-silicon alloy substrate layer; S3: Alternately stack and assemble the pure aluminum reinforcement layer and the aluminum-silicon alloy substrate layer to form a layered composite billet; S4: The layered composite billet is rolled and annealed to form a metallurgical bonding interface between the aluminum-silicon alloy matrix layer and the pure aluminum reinforcement layer, thereby obtaining an aluminum-silicon alloy part with a layered heterostructure.

[0011] In this embodiment of the invention, the outer layer of the semi-solid rheo-die-cast Al-Si alloy is an Al-Si alloy casting with medium strength and medium plasticity. First, a high cooling rate is achieved through forced heat exchange of molten metal, preparing a semi-solid slurry consisting of spherical primary α-Al phase and a remaining high-solute liquid phase. This semi-solid slurry is then die-cast into an alloy. Because this type of casting has a uniform microstructure of equiaxed primary α-Al phase and rounded ellipsoidal fine Si phase, it can achieve high strength (ultimate tensile strength ≥260.0 MPa) and high plasticity (elongation ≥7.0%) without heat treatment. The preparation method is simple, the composition is stable, and it is easy to industrialize. In contrast, Al-Si alloy castings prepared by other methods are prone to internal defects such as large dendrites, pores, and inclusions, which easily lead to large-area cracking, delamination, or fracture during subsequent rolling. If we start by optimizing the heat treatment process, a long heat treatment process can slightly improve the strength and plasticity of the parts to a certain extent, but it is not advantageous in terms of effect, energy consumption and production efficiency; a slight improvement in plasticity can only be achieved by sacrificing strength significantly.

[0012] As an optional implementation, the rheological forming in S2 includes extrusion casting or rheological die casting to obtain an aluminum-silicon alloy matrix layer with a U-groove structure; S3 includes assembling the layered composite blank by placing a pure aluminum reinforcement layer in the U-shaped groove, wherein the pure aluminum reinforcement layer forms surface contact with the sidewall and bottom of the U-shaped groove.

[0013] Exemplarily, the extrusion casting includes pouring the semi-solid slurry into the cylinder of an extrusion casting press to complete the extrusion casting process, resulting in a semi-solid aluminum-silicon alloy extrusion casting with a microstructure in which an ellipsoidal eutectic silicon phase is uniformly distributed around a spherical or near-spherical α-Al phase, and exhibiting high strength and plasticity. The casting temperature is 700~710℃, and the extrusion casting process parameters are: a continuous clamping force ≥650 kN applied during the extrusion forming process, a forming specific pressure of 100~120 MPa, and a filling speed of 30~40 mm / s.

[0014] As an optional implementation, the rolling compound described in S4 includes sequential high-temperature rolling and cold rolling; The high-temperature rolling process includes performing a short-time isothermal pretreatment followed by multiple passes of high-temperature rolling on a twin-roll mill. The cold rolling process includes short-time solution treatment, followed by air cooling to room temperature and then multiple passes of cold rolling on a twin-roll mill.

[0015] As an optional implementation, the starting rolling temperature of the multi-pass high-temperature rolling is 350℃~400℃, the number of rolling passes is 3~5, the total reduction is 40%~50%, the hot rolling force is 500~650KN, and the roll speed during rolling is 10~25m / min. The short-time isothermal pretreatment is performed at a temperature of 300℃~400℃ for 15~45 minutes. The temperature of the short-time solution treatment is 300℃~450℃, and the holding time is 30~45 minutes; The multi-pass cold rolling process consists of 3 to 5 passes, with a total reduction of 60% to 75%, a rolling force of 500 to 650 kN, and a roll speed of 2.0 to 5.0 m / min. The annealing process is performed at a temperature of 300~375℃ for 60~75 minutes.

[0016] As an optional implementation, the preparation of the semi-solid slurry in S1 includes preparing an Al-Si alloy semi-solid slurry composed of a spherical primary α-Al solid phase and a Si- and Mg-rich residual liquid phase using a wave-type semi-solid slurry preparation device, with a cooling rate ≥350℃ / s.

[0017] Preferably, before preparing the semi-solid slurry, the alloy raw materials are melted in a medium-frequency induction heating furnace, and after being heated to 720°C~750°C, the molten metal is transferred to a casting crucible and purified using hexachloroethane, including degassing and slag removal.

[0018] As an optional implementation, the pure aluminum reinforcement layer has a length of 40-55 mm, a width of 10-20 mm, and a thickness of 2-6 mm.

[0019] As an optional implementation, the aluminum-silicon alloy substrate layer is a "U-shaped part", the length of the aluminum-silicon alloy substrate layer is 45~55mm, the width is 15~25mm, the thickness is 12~25mm, the single-side wall thickness of the U-shaped section is 3~10mm, and the gap between the two wall thicknesses of the U-shaped section is 2~5mm.

[0020] Compared with the prior art, the present invention has the following advantages and beneficial effects: 1. This invention provides a layered heterogeneous aluminum-silicon alloy component. By constructing a layered heterogeneous structure consisting of alternating layers of hard aluminum-silicon alloy and soft pure aluminum, a strong connection and load transfer between the hard and soft regions are achieved through a metallurgical interface. Under external force, the hard and soft regions undergo uncoordinated deformation due to the difference in elastic modulus and yield strength. This results in high-density accumulation of geometrically necessary dislocations in the interface region, forming long-range back stress. This back stress, as a heterogeneous deformation-induced strengthening stress, effectively hinders dislocation movement and thus enhances work hardening capability. Simultaneously, the soft region coordinates overall strain and inhibits crack initiation through preferential deformation, while the hard region maintains the structural load-bearing strength. This achieves a synergistic match between high strength and high plasticity, overcoming the problem of inverted strength and plasticity in traditional single homogeneous materials, and obtaining a layered composite component with both excellent mechanical properties and structural integrity.

[0021] 2. This invention provides a method for preparing lightweight, layered heterostructure aluminum-silicon alloy parts with high strength and high plasticity. Semi-solid rheological extrusion casting is used to refine the grains while preventing the eutectic Si from growing into a coarse dendritic structure, ensuring it is ellipsoidally dispersed around the spherical α-Al phase. In existing technologies, without heat treatment, it is difficult to significantly improve the plasticity of aluminum-silicon alloys. Excessive heat treatment time and temperature are not advantageous in terms of energy consumption and production costs; furthermore, heat treatment often sacrifices plasticity to achieve a slight increase in strength. However, in this invention, industrial pure aluminum has high plasticity and low strength. Combining it with semi-solid rheological aluminum-silicon alloy extrusion castings, which have higher strength and higher plasticity, and through multi-pass segmented rolling followed by short-time annealing, an aluminum-silicon alloy structural part with a layered heterostructure is prepared, overturning the established notion that aluminum-silicon alloys cannot simultaneously achieve high strength and high plasticity.

[0022] 3. This invention combines rheological extrusion casting and segmented rolling processes, avoiding the high energy consumption and high cost associated with prolonged high-temperature heat treatment. The method is not only applicable to the combination of aluminum-silicon alloys and industrial pure aluminum, but also to the joint preparation of plates with ultra-high mechanical properties using 7xxx alloys, 6xxx alloys, and aluminum-magnesium alloys with industrial pure aluminum. The method employed in this invention, combining rheological extrusion casting and rolling, shows promise for large-scale industrial application.

[0023] 4. In this embodiment of the invention, a rheological extrusion casting process is used to pre-refine the grains, ensuring that the eutectic silicon phase and primary silicon phase are distributed in a rounded ellipsoidal morphology around the spherical α-Al phase. This is then combined with multi-pass hot rolling of high-plasticity pure aluminum plates, refining the grain size of the fine-grained layer of the layered heterostructure to 5.0~35μm. The Si phase is broken and further refined to 500nm~2μm, dispersing as fine particles uniformly at the grain boundaries of the fine-grained hard layer, providing strong grain boundary pinning. Simultaneously, the grain size of the soft, tough, coarse-grained core layer remains at 450μm~1mm. Therefore, during large plastic deformation, the difference in microscale and mechanical properties between the soft and hard phases generates heterogeneous deformation-induced strengthening stress due to the interaction between the soft and hard regions, stimulating continuous heterogeneous deformation-induced strengthening and achieving a synergistic improvement in strength and plasticity. The mechanical properties far exceed those of traditional homogeneous materials. This establishes the high strength and ultra-high plasticity of this novel layered heterostructure.

[0024] 5. This invention employs a semi-solid rheological extrusion casting U-shaped aluminum-silicon alloy shell, directly assembling the industrial pure aluminum sheet and the U-shaped shell together with an interference fit. During high-temperature rolling, the pure aluminum core diffuses and fuses with the Al phase of the aluminum-silicon alloy sheet. No welding, mechanical connections, or other pre-treatment methods are required, effectively reducing production costs.

[0025] 6. The layered heterostructure aluminum-silicon alloy parts prepared in the embodiments of the present invention construct a gradient structure in which the aluminum-silicon alloy layer consists of a fine-grained outer shell and a coarse-grained Al phase in the core. By utilizing the Si phase in the fine-grained layer appearing in the Al matrix as dot-like particles and pinning the grain boundaries, the grain size is refined to below 2.0 μm, and the average size of the fine grains in the outer shell is controlled to below 32 μm. At the same time, the average size of the coarse-grained Al phase in the core is maintained above 800 μm. The fine-grained outer shell provides high-strength support and hinders dislocation movement through grain boundary strengthening and second-phase strengthening, while the coarse-grained core coordinates deformation and inhibits crack propagation through dislocation slip and grain boundary migration. Thus, a synergistic matching effect of strength and plasticity with an ultimate tensile strength of not less than 300 MPa and an elongation of not less than 20% is achieved, which fully meets the requirements of lightweight automotive production and aerospace for lightweight sheet materials with ultra-high mechanical properties. Attached Figure Description

[0026] To more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of the present invention and should not be considered as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort. In the drawings: Figure 1This is a process flow diagram provided for an embodiment of the present invention, wherein... Figure 1 'a' is a flowchart of the preparation process of flat solid slurry. Figure 1 b is a flow chart of the rheo-extrusion casting process. Figure 1 c is a flowchart of the sandwich structure pretreatment process. Figure 1 d is the rolling process flow chart; Figure 1 d-1 is a process diagram of the rolling process. Figure 1 d-2 is a diagram illustrating the formation mechanism of heterostructures; Figure 2 Dimensional drawing of a U-shaped part formed by semi-solid rheological extrusion casting. Figure 2 'a' corresponds to the front view. Figure 2 b corresponds to the side view; Figure 3 Here is a picture of the actual sample, in which Figure 3 a corresponds to Example 1. Figure 3 b corresponds to Example 4. Figure 3 c corresponds to a response ratio of 1; Figure 4 The image shows the microstructure of the layered heterostructure prepared in Example 1. Figure 4 b is Figure 4 Enlarged view of point b in section a. Figure 4 c is Figure 4 Enlarged view of point c in section a; Figure 5 This is a diagram showing the grain structure of the layered heterostructure prepared in Example 1, where... Figure 5 a is an EBSD micrograph. Figure 5 b is a summary diagram of the grain size; Figure 6 The image shows the microstructure of the layered heterostructure prepared in Example 2. Figure 6 b is Figure 6 Enlarged view of point b in section a. Figure 6 c is Figure 6 Enlarged view of point c in section a; Figure 7 The energy spectrum of the layered heterostructure prepared in Example 2, Figure 7 'a' corresponds to the Al element. Figure 7 b corresponds to the Si element. Figure 7 c corresponds to the element Fe. Figure 7 d corresponds to the element Mg; Figure 8 The image shows the microstructure of the layered heterostructure prepared in Example 3, wherein... Figure 8 b is Figure 8 Enlarged view of point b in section a. Figure 8 c is Figure 8 Enlarged view of point c in section a; Figure 9The image shows the microstructure of the layered heterostructure prepared in Example 4, wherein... Figure 9 b is Figure 9 Enlarged view of point b in section a. Figure 9 c is Figure 9 Enlarged view of point c in section a; Figure 10 The energy spectrum of the layered heterostructure prepared in Example 4 is shown. Figure 10 'a' corresponds to the Al element. Figure 10 b corresponds to the Si element. Figure 10 c corresponds to the element Fe. Figure 10 d corresponds to the element Mg; Figure 11 This is a diagram showing the grain structure of the layered heterostructure prepared in Example 4. Figure 11 a is an EBSD micrograph. Figure 11 b is a summary diagram of the grain size; Figure 12 Comparison of stress-strain curves of Al-Si alloys prepared in Examples 1-4 and Comparative Examples 2 and 3. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the embodiments. The illustrative embodiments and descriptions of this invention are only used to explain this invention and are not intended to limit this invention.

[0028] In the following description, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be apparent to those skilled in the art that these specific details are not necessary to practice the invention. In other embodiments, well-known materials or methods have not been specifically described in order to avoid obscuring the invention.

[0029] Throughout this specification, references to "an embodiment," "an example," or "an example" mean that a particular feature, structure, or characteristic described in connection with that embodiment or example is included in at least one embodiment of the invention. Therefore, the phrases "an embodiment," "an example," "an example," or "an example" appearing in various places throughout the specification do not necessarily refer to the same embodiment or example. Furthermore, specific features, structures, or characteristics can be combined in one or more embodiments or examples in any suitable combination and / or sub-combination. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described herein, as well as the features of those different embodiments or examples.

[0030] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60–120 and 80–110 are listed for a specific parameter, it is understood that ranges of 60–110 and 80–120 are also expected. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1–3, 1–4, 1–5, 2–3, 2–4, and 2–5. In this application, unless otherwise stated, the numerical range "a–b" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0~5" indicates that all real numbers between "0~5" have been listed in this article; "0~5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0031] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the method may also include step (c), indicating that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0032] Please refer to the reference. Figure 1 and Figure 2 As shown, this embodiment of the invention provides a method for preparing a layered heterostructure aluminum-silicon alloy part, comprising the following steps: S1: Preparation and Smelting of Aluminum-Silicon Alloy Raw Materials The aluminum-silicon alloy raw materials are prepared according to the following mass percentages: Si: 5.50~7.50 wt.%, Mg: 0.25~0.55 wt.%, Fe: 0.05~0.10 wt.%, total impurities ≤0.10 wt.%, balance Al. The prepared raw materials are melted in a medium-frequency induction heating furnace. After heating to 720℃~750℃, the molten metal is transferred to a casting crucible and purified using hexachloroethane, including degassing and slag removal.

[0033] S2: Semi-solid slurry preparation and rheological forming A semi-solid Al-Si alloy slurry, composed of a spherical primary α-Al solid phase and a Si- and Mg-rich residual liquid phase, was prepared using a wave-type semi-solid slurry preparation device, with a cooling rate controlled at ≥350℃ / s. The semi-solid slurry was then subjected to rheological forming, including extrusion casting or rheological die casting, to obtain an aluminum-silicon alloy matrix layer with a U-shaped groove structure. The extrusion casting involved pouring the semi-solid slurry into the cylinder of an extrusion casting press to complete the extrusion casting process. The casting temperature was 700~710℃, and the extrusion casting process parameters were: a continuous clamping force ≥650 kN, a forming specific pressure of 100~120 MPa, and a filling speed of 30~40 mm / s. The resulting semi-solid aluminum-silicon alloy extrusion casting had a microstructure in which an ellipsoidal eutectic silicon phase was uniformly distributed around spherical or near-spherical α-Al phases.

[0034] S3: Pretreatment and Assembly of Pure Aluminum Reinforcement Layer Industrial pure aluminum sheets with dimensions of 40-55 mm in length, 10-20 mm in width, and 2-6 mm in thickness are used as pure aluminum reinforcement layers. After being ground smooth, they are cleaned with anhydrous ethanol and dried. The pretreated pure aluminum reinforcement layer is placed inside the aluminum-silicon alloy substrate layer with a U-shaped groove structure obtained in S2. The two are assembled using an interference fit, with the pure aluminum reinforcement layer forming surface contact with the sidewalls and bottom of the U-shaped groove, resulting in a "sandwich" structure blank in which the pure aluminum reinforcement layer is wrapped by the aluminum-silicon alloy substrate layer. The aluminum-silicon alloy substrate layer has a length of 45-55 mm, a width of 15-25 mm, and a thickness of 12-25 mm. The single-side wall thickness of the U-shaped cross-section is 3-10 mm, and the gap between the two wall thicknesses of the U-shaped cross-section is 2-5 mm.

[0035] S4: Rolling compounding and annealing treatment The billet obtained from S3 is subjected to isothermal pretreatment at 300℃~400℃ for 15~45 minutes. Immediately afterward, it undergoes multi-pass high-temperature rolling on a twin-roll mill: initial rolling temperature 350℃~400℃, 3~5 passes, total reduction 40%~50%, hot rolling force 500~650 kN, and roll speed 10~25 m / min. This is followed by short-time solution treatment at 300℃~450℃ for 30~45 minutes. After air cooling to room temperature, it undergoes multi-pass cold rolling on a twin-roll mill: 3~5 passes, total reduction 60%~75%, rolling force 500~650 kN, and roll speed 2.0~5.0 m / min. Finally, annealing is performed at a temperature of 300~375℃ for 60~75 minutes to obtain an aluminum-silicon alloy part with a layered heterostructure.

[0036] This invention first refines the grain size of an aluminum-silicon alloy using semi-solid rheo-extrusion casting, avoiding the coarse dendritic structure commonly found in traditional aluminum-silicon alloys. Subsequently, the rheo-extrusion-cast aluminum-silicon alloy U-shaped part is assembled with an industrial pure aluminum sheet using an interference fit. A multi-pass hot and cold rolling process introduces intense plastic deformation, refining the fine-grained hardening layer to 31.1 μm and breaking down and refining the dispersed Si phase in the layer to 500 nm–2.0 μm, thus achieving grain boundary pinning. The core soft-tough coarse-grained layer maintains a grain size of 450 μm–1 mm, achieving microstructural control of the soft / hard regions, stimulating heterogeneous deformation-induced strengthening, and achieving a synergistic improvement in the alloy's strength and plasticity. Furthermore, this invention combines the advantages of rheo-extrusion casting and segmented rolling processes, reducing production costs and energy consumption, and possesses strong prospects for industrial application. Compared with the prior art, the method for preparing high-strength and ultra-high ductility aluminum-silicon alloy provided by the embodiments of the present invention meets the requirements of lightweight automotive production and aerospace for lightweight structural components with ultra-high mechanical properties.

[0037] To better demonstrate the effects of the embodiments of the present invention, specific embodiments will be set up for verification below.

[0038] Example 1: This embodiment of the invention provides a method for preparing a layered heterostructure aluminum-silicon alloy part, comprising the following steps: S1: Preparation and Smelting of Aluminum-Silicon Alloy Raw Materials The aluminum-silicon alloy raw materials were prepared according to the following mass percentages: S: 7.0 wt.%, Mg: 0.3 wt.%, Fe: 0.05 wt.%, Al: 92.65 wt.%. 2 kg of the prepared raw materials were melted in a medium-frequency induction heating furnace. After heating to 725℃±2℃, the molten metal was transferred to a casting crucible. 1.5 g of hexachloroethane was weighed and injected into the molten metal, followed by rapid stirring for purification treatment to achieve degassing and impurity removal.

[0039] S2: Semi-solid slurry preparation and rheological forming A semi-solid Al-Si alloy slurry, composed of spherical primary α-Al solid phase and Si- and Mg-rich residual liquid phase, was prepared using a wave-type semi-solid slurry preparation device, with a cooling rate controlled to 350°C / s. The semi-solid slurry was then subjected to rheological forming, including extrusion casting, to obtain an aluminum-silicon alloy matrix layer with a U-shaped groove structure. The extrusion casting involved directly pouring the semi-solid slurry into an extrusion casting cylinder to complete the extrusion casting process. The casting temperature was 700°C, and the extrusion casting process parameters were: continuous clamping force of 650 kN, forming specific pressure of 110 MPa, and filling speed of 35 mm / s. The resulting semi-solid aluminum-silicon alloy extrusion casting exhibited a microstructure in which ellipsoidal eutectic silicon phase was uniformly distributed around spherical or near-spherical α-Al phases.

[0040] S3: Pretreatment and Assembly of Pure Aluminum Reinforcement Layer The cutting dimensions are: length 48.0 ± 0.5 mm, width 16 ± 0.5 mm, and thickness 4.00 mm. +0.25 A 1 mm thick industrial pure aluminum sheet is used as the pure aluminum reinforcement layer. After being smoothed with metallographic sandpaper, it is repeatedly cleaned and dried with anhydrous ethanol to obtain a pretreated pure aluminum sheet. The pretreated pure aluminum reinforcement layer is placed inside the aluminum-silicon alloy substrate layer with a U-shaped groove structure obtained in S2. The two are assembled using an interference fit, with the pure aluminum reinforcement layer forming surface contact with the sidewalls and bottom of the U-shaped groove, resulting in a "sandwich" structure blank in which the pure aluminum reinforcement layer is enclosed by the aluminum-silicon alloy substrate layer. The aluminum-silicon alloy substrate layer has a length of 50.0±0.5 mm, a width of 17.0±0.5 mm, and a height of 20.0±0.5 mm. The single-side wall thickness of the U-shaped section is 6.5±0.5 mm, and the gap between the two wall thicknesses of the U-shaped section is 4.0 mm. 0 -0.25 mm.

[0041] S4 Rolling Composite and Annealing Treatment The billet obtained from S3 underwent isothermal pretreatment at 350℃ for 45 minutes. Immediately afterwards, it was subjected to multi-pass high-temperature rolling on a twin-roll mill: initial rolling temperature 350℃, 3 passes, total reduction 50%, hot rolling force 500 kN, and roll speed 10 m / min. This was followed by short-time solution treatment at 400℃ for 45 minutes, followed by air cooling to 20℃, and then multi-pass cold rolling on a twin-roll mill: 4 passes, total reduction 70%, rolling force 500 kN, and roll speed 2.0 m / min. Finally, annealing was performed at 370℃ for 60 minutes to obtain an aluminum-silicon alloy part with a layered heterogeneous structure.

[0042] Example 2: This embodiment of the invention provides a method for preparing a layered heterostructure aluminum-silicon alloy part. The difference from Example 1 is that the short-time solution treatment is not performed in S4, while the other steps remain unchanged.

[0043] Example 3: This embodiment of the invention provides a method for preparing a layered heterostructure aluminum-silicon alloy part. The difference from Example 1 is that in S3, the thickness of the industrial pure aluminum plate and the gap between the two wall thicknesses of the U-shaped section are the same, both being 4.0 mm. The pure aluminum reinforcing layer and the aluminum-silicon alloy substrate layer are assembled using an overfitting method, while the remaining steps remain unchanged.

[0044] Example 4: A method for preparing an aluminum-silicon alloy part, comprising the following: S1: Preparation and Smelting of Aluminum-Silicon Alloy Raw Materials The aluminum-silicon alloy raw materials were prepared according to the following mass percentages: Si: 7.0 wt.%, Mg: 0.3 wt.%, Fe: 0.05 wt.%, Al: 92.65 wt.%. 2 kg of the prepared raw materials were melted in a medium-frequency induction heating furnace. After heating to 725℃, the molten metal was transferred to a casting crucible. 1.5 g of hexachloroethane was weighed and injected into the molten metal, followed by rapid stirring for purification treatment to achieve degassing and impurity removal.

[0045] S2 Semi-solid slurry preparation and rheological forming A semi-solid Al-Si alloy slurry was prepared using a cooling ramp method, with the cooling rate controlled to reach 350°C / s. The semi-solid slurry was then subjected to rheological forming, including extrusion casting, to obtain an aluminum-silicon alloy matrix layer. The extrusion casting involved directly pouring the semi-solid slurry into an extrusion casting cylinder to complete the extrusion casting process. The casting temperature was 700°C, and the extrusion casting process parameters were: continuous clamping force of 650 kN, forming specific pressure of 110 MPa, and filling speed of 35 mm / s, resulting in a semi-solid aluminum-silicon alloy extrusion casting.

[0046] S3 Pure Aluminum Reinforcement Layer Pretreatment and Assembly Industrial pure aluminum sheets with dimensions of 48 mm in length, 20 mm in width, and 4 mm in thickness were used as pure aluminum reinforcement layers. After being smoothed with metallographic sandpaper, they were cleaned with anhydrous ethanol and dried to obtain pretreated pure aluminum sheets. The semi-solid aluminum-silicon alloy extrusion castings obtained from S2 were cut into aluminum-silicon alloy sheets with dimensions of 48 mm in length, 20.0 mm in width, and 10 mm in thickness. These sheets were then stacked together with the pretreated pure aluminum reinforcement layers and sealed around the edges to obtain a double-layer structure blank consisting of an aluminum-silicon alloy matrix layer and a pure aluminum reinforcement layer.

[0047] S4 Rolling Composite and Annealing Treatment The double-layered billet obtained from S3 underwent isothermal pretreatment at 400℃ for 45 minutes. It was then subjected to multi-pass high-temperature rolling on a twin-roll mill: an initial rolling temperature of 350℃, three rolling passes, a total reduction of 50%, a hot rolling force of 500 kN, and a roll speed of 10 m / min. This was followed by short-time solution treatment at 400℃ for 45 minutes, followed by air cooling to 20℃. Finally, it underwent multi-pass cold rolling on a twin-roll mill: three rolling passes, a total reduction of 50%, a rolling force of 500 kN, and a roll speed of 2.0 m / min. Annealing was then performed at 370℃ for 60 minutes to obtain a double-layered heterostructure aluminum-silicon alloy.

[0048] Comparative Example 1: A method for preparing aluminum-silicon alloy parts is provided. The difference from Example 1 is that in S4, isothermal pretreatment, high-temperature rolling and solution treatment are not performed. Instead, cold rolling is performed directly. The cold rolling passes are 4, the rolling force is 500 KN, the roll speed during rolling is 2.0 m / min, and the total cold rolling reduction is 60%. The remaining steps remain unchanged.

[0049] Comparative Example 2: A method for preparing an aluminum-silicon alloy part is provided, comprising the following steps: S1: Preparation and Smelting of Aluminum-Silicon Alloy Raw Materials The aluminum-silicon alloy raw materials were prepared according to the following mass percentages: Si: 7.0 wt.%, Mg: 0.3 wt.%, Fe: 0.05 wt.%, Al: 92.65 wt.%. 2 kg of the prepared raw materials were melted in a medium-frequency induction heating furnace. After heating to 725℃±2℃, the molten metal was transferred to a casting crucible. 1.5 g of hexachloroethane was weighed and injected into the molten metal, followed by rapid stirring for purification treatment to achieve degassing and impurity removal.

[0050] S2 Semi-solid slurry preparation and rheological forming A semi-solid Al-Si alloy slurry was prepared using a cooling ramp method, with the cooling rate controlled to reach 350°C / s. The semi-solid slurry was then subjected to rheological forming, including extrusion casting, to obtain an aluminum-silicon alloy matrix layer. The extrusion casting involved directly pouring the semi-solid slurry into an extrusion casting cylinder to complete the extrusion casting process. The casting temperature was 700°C, and the extrusion casting process parameters were: continuous clamping force of 650 kN, forming specific pressure of 110 MPa, and filling speed of 35 mm / s, resulting in a semi-solid aluminum-silicon alloy extrusion casting.

[0051] Preparation of S3 rheo-extruded aluminum-silicon alloy billets The semi-solid aluminum-silicon alloy extrusion casting obtained from S2 was cut into blanks with a length of 48 mm, a width of 20.0 mm, and a thickness of 10 mm to obtain rheological extrusion casting aluminum-silicon alloy blanks.

[0052] S4 Segmented Rolling and Heat Treatment The billet obtained from S3 underwent isothermal pretreatment at 350℃ for 45 minutes. Immediately afterwards, it was subjected to multi-pass high-temperature rolling on a twin-roll mill: initial rolling temperature 350℃, 3 passes, total reduction 50%, hot rolling force 500 kN, and roll speed 10 m / min. This was followed by short-time solution treatment at 400℃ for 45 minutes, followed by air cooling to 20℃, and then multi-pass cold rolling on a twin-roll mill: 3 passes, total reduction 60%, rolling force 500 kN, and roll speed 2.0 m / min. Finally, annealing was performed at 370℃ for 60 minutes to obtain a rheological extrusion cast aluminum-silicon alloy segmented rolled plate.

[0053] Comparative Example 3: A method for preparing aluminum-silicon alloy parts is provided. The difference from Example 1 is that in S4, only the aluminum-silicon alloy matrix layer is subjected to short-time solution treatment and annealing treatment, and isothermal pretreatment, high-temperature rolling and cold rolling are not performed. The remaining steps remain unchanged, and the assembly step in S3 is deleted to prepare a semi-solid aluminum-silicon alloy extrusion casting.

[0054] The products prepared in Examples 1-4 and Comparative Examples 1-3 were subjected to apparent and mechanical property tests. Mechanical property testing was conducted according to GB / T228.1-2002 standard. Plate-shaped specimens were selected, and the stress-strain curves of the materials were determined by axial loading to obtain tensile strength and elongation. The test results were compared with reference... Figures 1-12 And as shown in Table 1 below: Table 1. Mechanical property data of the parts prepared in the examples and comparative examples.

[0055] Reference Figure 3 As shown, the part prepared in Example 1 did not exhibit macroscopic defects such as delamination or cracking; the soft and tough pure aluminum core was tightly encased by a strong, semi-solid rheological extrusion casting on the outside. Figure 4 It can be seen that there are no microcracks or fine delaminations between the outer Al-Si fine-grained layer and the core coarse-grained layer, and the elemental distribution is uniform as shown in the magnified local image. Because the outer Al-Si fine-grained layer is produced by rheological extrusion casting, the Si phase is uniformly distributed, and after segmented rolling, its macroscopic hardness is significantly higher than that of the primary pure aluminum in the core. Figure 5The EBSD results show that the outer, hard Al-Si fine-grained layer has an equiaxed grain structure with an average grain size of 31.1 μm, while the core, soft and tough coarse-grained layer, has an average grain size of 835.6 μm, exhibiting a significant difference in grain size. Furthermore, the Si phase distributed in the outer, hard Al-Si fine-grained layer is clearly broken and refined, exhibiting a dense, granular dispersion with a size ranging from 500 nm to 2.5 μm. In this structure, the soft / hard phases are arranged in layers, and a significant strain gradient is generated at the interface between the coarse-grained soft and tough layer and the fine-grained hard layer, which can induce the accumulation of geometrically necessary dislocations, achieving heterogeneous deformation-induced strengthening. Figure 12 As shown in Table 1, with increasing applied stress, the coarse-grained soft and ductile layer undergoes plastic deformation first, while the fine-grained hard layer maintains elasticity. Tensile stress is generated in the coarse-grained soft and ductile layer, while compressive stress is generated in the fine-grained hard layer. When the hard layer begins to undergo plastic deformation, the entire part reaches the plastic deformation stage. The coarse-grained soft and ductile layer has a high strain hardening capacity to support the unstable fine-grained hard layer. This allows the entire part to deform stably to a high strain state, achieving ultra-high plasticity of the alloy while maintaining ideal tensile strength.

[0056] Combined with reference Figure 6 and Figure 7 It can be seen that the preparation method described in this embodiment yields high-strength and high-ductility Al-Si layered heterostructure alloy parts. (Comparison) Figure 4 and Figure 6 As can be seen, in Embodiment 2 of the present invention, due to the lack of short-time solution treatment on the part, the Al-Si alloy layered heterostructure part obtained by the preparation method has low microstructure uniformity. Mg element aggregation occurs at the interface between the coarse-grained soft and tough layer and the fine-grained hard layer, easily forming a magnesium-rich intermetallic brittle π-Al8FeMg3Si6 phase. (See Table 1 and...) Figure 12 It can be seen that its strength is lower than the mechanical properties of the part prepared in Example 1.

[0057] like Figure 8 As shown, the Al-Si layered heterostructure alloy part obtained by the preparation method described in Example 3. (Comparison) Figure 4 , Figure 6 and Figure 8 It can be seen that, due to the lack of an interference fit between the outer layer and the core, obvious gaps and delamination occur between them, and the soft, tough, coarse-grained layer cannot support the unstable fine-grained, strong layer under high stress. (From Table 1 and...) Figure 12 It can be seen that its strength and plasticity are lower than the mechanical properties of the parts prepared in Examples 1 and 2.

[0058] like Figure 9As shown, the Al-Si layered heterostructure alloy part obtained by the preparation method described in Example 4 has a similar microstructure morphology to that of Example 1, but a small number of microcracks appear between the coarse-grained soft and tough layer and the fine-grained hard layer. Figure 10 It can be seen that short-term solution treatment can effectively prevent the aggregation of Mg at the interface. Figure 11 It can be seen that the grain size distribution is more dispersed than in Example 1, and the grain size difference between the coarse-grained soft and tough layer and the fine-grained hard layer is smaller than in Example 1. This results in a weaker heterogeneous deformation-induced strengthening effect than in Example 1 when stress increases. (See Table 1 for details.) Figure 12 It can be seen that, since the volume fraction of the fine-grained hard layer is similar to that of the coarse-grained soft and tough layer, the ultra-high plasticity (elongation ≥30%) provided by the soft and tough layer is retained, but the tensile strength is much lower than that of Example 1.

[0059] like Figure 3 As shown, in Comparative Example 1, after direct cold rolling, the rolled plate exhibited large-area cracking. Furthermore, significant delamination occurred between the core of industrial pure aluminum and the outer layer of rheological extrusion casting.

[0060] Comparative Example 2 uses the same multi-pass segmented rolling process as Example 1 on rheological extrusion castings, resulting in a structural component with significantly reduced tensile strength and low elongation. Comparative Example 3 uses the same short-time heat treatment process as Example 1 on rheological extrusion castings, resulting in a structural component with significantly reduced tensile strength and low elongation.

[0061] As can be seen from the data in Table 1, the layered heterostructure aluminum-silicon alloy structural parts obtained by combining semi-solid rheological die casting, multi-pass segmented rolling, and short-time heat treatment processes in the embodiments of the present invention have a tensile strength greater than 310 MPa and an elongation greater than 21%. Meanwhile, it was found that without short-time solution treatment before cold rolling, the tensile strength of the obtained layered heterostructure aluminum-silicon alloy structural parts decreased slightly from 311.56 MPa to 308.86 MPa, but the elongation decreased from 22.47% to 18.13%. This indicates that the Mg element aggregation at the interface between the coarse-grained soft and tough layer and the fine-grained hard layer easily forms a magnesium-rich intermetallic brittle π-Al8FeMg3Si6 phase, which is not conducive to maintaining a significant balance between high strength and ultra-high plasticity.

[0062] In Example 3, the rheological extrusion casting U-shaped part and the core industrial pure aluminum sheet did not use an interference fit, resulting in micron-level delamination. Example 4 involved the composite rolling of a single-layer rheological extrusion casting U-shaped part and an industrial pure aluminum sheet. Although both examples yielded layered heterogeneous structures similar to Example 1, during the stretching process, compared to Example 1, the strain gradient at the interface between the fine-grained hard outer layer and the coarse-grained soft and tough layer was smaller, resulting in weaker heterogeneous deformation-induced strengthening. As the applied stress increased, the high strain hardening capacity of the coarse-grained soft and tough layer could not support the unstable fine-grained hard layer. This made it difficult for the entire part to deform to a high strain state, highlighting the ultra-high plasticity of the coarse-grained soft and tough layer, while the alloy tensile strength was not ideal.

[0063] Finally, it should be noted that the specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention. It is obvious to those skilled in the art that this application is not limited to the details of the above exemplary embodiments, and that the present application can be implemented in other specific forms without departing from the spirit or basic characteristics of the present application. Therefore, the embodiments should be considered exemplary and non-limiting in all respects. The scope of this application is defined by the appended claims rather than the foregoing description, and therefore all changes falling within the meaning and scope of the equivalents of the claims are intended to be included within this application.

Claims

1. A layered heterogeneous aluminum-silicon alloy component, characterized in that, The structure comprises a layered heterogeneous structure with alternating soft and hard regions. The hard regions include an aluminum-silicon alloy matrix layer, and the soft regions include a pure aluminum reinforcement layer. A metallurgical bonding interface is formed between the aluminum-silicon alloy matrix layer and the pure aluminum reinforcement layer.

2. A layered heterostructure aluminum-silicon alloy part according to claim 1, wherein the layered heterostructure comprises two layers of the aluminum-silicon alloy matrix sandwiching a layer of pure aluminum reinforcement to form a "sandwich" structure, and the pure aluminum reinforcement is located between the two layers of aluminum-silicon alloy matrix.

3. The layered heterostructure aluminum-silicon alloy part according to claim 1, characterized in that, The aluminum-silicon alloy substrate layer comprises elements in the following mass percentages. composition: Si: 5.50~7.50 wt.%; Mg: 0.25~0.55 wt.%; Fe: 0.05~0.10 wt.%; Total impurities ≤ 0.10 wt.%, balance is Al.

4. A method for preparing a layered heterostructure aluminum-silicon alloy part as described in any one of claims 1 to 3, characterized in that, Includes the following steps: S1: Melt aluminum-silicon alloy raw materials and prepare them into a semi-solid slurry; S2: The semi-solid slurry is rheoformed into an aluminum-silicon alloy substrate layer; S3: Alternately stack and assemble the pure aluminum reinforcement layer and the aluminum-silicon alloy substrate layer to form a layered composite billet; S4: The layered composite billet is rolled and annealed to form a metallurgical bonding interface between the aluminum-silicon alloy matrix layer and the pure aluminum reinforcement layer, thereby obtaining an aluminum-silicon alloy part with a layered heterostructure.

5. The method for preparing a layered heterostructure aluminum-silicon alloy part according to claim 4, characterized in that, The rheological forming described in S2 includes squeeze casting or rheological die casting to obtain an aluminum-silicon alloy matrix layer with a U-shaped groove structure; S3 includes assembling the layered composite blank by placing a pure aluminum reinforcement layer in the U-shaped groove, wherein the pure aluminum reinforcement layer forms surface contact with the sidewall and bottom of the U-shaped groove.

6. The method for preparing a layered heterostructure aluminum-silicon alloy part according to claim 4, characterized in that, The rolling composite process described in S4 includes sequential high-temperature rolling and cold rolling; The high-temperature rolling process includes performing a short-time isothermal pretreatment followed by multiple passes of high-temperature rolling on a twin-roll mill. The cold rolling process includes short-time solution treatment, followed by air cooling to room temperature and then multiple passes of cold rolling on a twin-roll mill.

7. The method for preparing a layered heterostructure aluminum-silicon alloy part according to claim 6, characterized in that, The starting temperature of the multi-pass high-temperature rolling is 350℃~400℃, the number of rolling passes is 3~5, the total reduction is 40%~50%, and the temperature of the short-time isothermal pretreatment is 300℃~400℃, and the time is 15~45 minutes. The temperature of the short-time solution treatment is 300℃~450℃, and the holding time is 30~45 minutes; The multi-pass cold rolling process consists of 3 to 5 passes, with a total reduction of 60% to 75%. The annealing process is performed at a temperature of 300~375℃ for 60~75 minutes.

8. The method for preparing a layered heterostructure aluminum-silicon alloy part according to claim 4, characterized in that, The preparation of the semi-solid slurry described in S1 includes preparing an Al-Si alloy semi-solid slurry composed of a spherical primary α-Al solid phase and a Si- and Mg-rich residual liquid phase using a wave-type semi-solid slurry preparation device.

9. The method for preparing a layered heterostructure aluminum-silicon alloy part according to claim 4, characterized in that, The pure aluminum reinforcement layer has a length of 40-55 mm, a width of 10-20 mm, and a thickness of 2-6 mm.

10. The method for preparing a layered heterostructure aluminum-silicon alloy part according to claim 9, characterized in that, The aluminum-silicon alloy substrate layer is a "U-shaped part". The length of the aluminum-silicon alloy substrate layer is 45~55mm, the width is 15~25mm, the thickness is 12~25mm, the single-side wall thickness of the U-shaped section is 3~10mm, and the gap between the two wall thicknesses of the U-shaped section is 2~5mm.

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