Aluminum alloy profile for battery tray extrusion and preparation process

Abstract

The invention belongs to the field of aluminum alloy profiles for battery trays, and provides an aluminum alloy profile for extrusion of a battery tray and a processing technology of the aluminum alloy profile for extrusion of the battery tray. A double-network precipitation structure in which an intragranular fine first network nano precipitated phase and a grain boundary second network sub-micron precipitated phase cooperatively exist is constructed, so that the yield strength, the tensile strength, the bending energy absorption capacity and the tension-compression fatigue life are synchronously improved on the premise of ensuring good heat conductivity and extrusion forming precision of the profile; the problem that an existing 6xxx series aluminum alloy is difficult to consider essential contradictions among high strength, high bending energy absorption, long service life, crack resistance, straightness control under the high extrusion ratio and battery tray heat management requirements is solved, and the application value of improving the light weight, safety and long-term service reliability of the new energy automobile power battery tray is achieved.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of aluminum alloy profiles for battery trays, and provides an aluminum alloy profile for extrusion of battery trays and a processing technology thereof. BACKGROUND

[0002] With the rapid development of the new energy automobile industry, the energy density and the loading scale of the power battery system continue to improve, so that the power battery tray not only needs to provide geometric support and installation positioning for the battery cell module, but also must bear the main load and energy absorption function under the vehicle collision, jolt impact and long-term fatigue load. In the existing power battery tray structural material, the 6xxx series extruded aluminum alloy is widely used because of its good medium-high strength, corrosion resistance and extrudability, but the traditional alloy system mainly depends on a single nano precipitation strengthening network or a strengthening mechanism mainly based on coarse second phase, and there is often a clear contradiction between high yield strength and high bending energy absorption: on the one hand, improving the yield strength usually depends on fine and dispersed precipitates and fine grain structure, which easily leads to a decrease in plasticity and insufficient local deformation capacity, thereby limiting the bending displacement and total energy absorption under three-point bending conditions; on the other hand, if the degree of strengthening is reduced to maintain a high elongation, it is difficult to meet the lower limit requirements of yield strength and tensile strength of the power battery tray under the requirements of lightweight and structural reliability. In addition, the battery tray profile usually adopts a high extrusion ratio profile section structure to realize multi-chamber stiffeners and complex force transmission paths, and the existing 6xxx series alloy is prone to surface defects, difficult to accurately control the extrusion outlet temperature, and uneven quenching and cooling under high extrusion speed or high extrusion ratio conditions, thereby affecting the straightness, section size accuracy and subsequent assembly accuracy of the profile, which is not conducive to the integrated lightweight design of the power battery system.

[0003] In terms of fatigue and service reliability, the power battery tray is subjected to alternating loads under vehicle acceleration and deceleration conditions, vibration loads caused by road roughness, and impact loads under occasional collision conditions. The traditional 6xxx series aluminum alloy has a single nano precipitation network or a microstructure mainly based on coarse grain boundary second phase, and the tensile-compressive symmetric fatigue life and crack propagation resistance are difficult to further improve, especially at 10 5 ~ 10 6Early micro-crack initiation and accelerated propagation along grain boundaries or sub-grain boundaries are prone to occur in high-cycle fatigue cycle range. In addition, in order to consider the thermal management of the battery module, the battery tray material also needs to have high thermal conductivity, so as to quickly conduct and diffuse heat under normal working conditions, and to realize effective heat diffusion under thermal runaway or local overheating working conditions. However, if the strength of the traditional 6xxx series alloy is improved by greatly increasing the content of alloying elements and the degree of precipitation strengthening, more solid solution atoms and dispersed second phases will be inevitably introduced, which will cause the thermal conductivity to decrease significantly, and there is an inherent conflict with the thermal management requirements of the power battery tray. For example, the Chinese patent with publication number CN115558827B discloses an Al-Cu-Mg-Ag-Si-Sc-Mn-Zr high-strength high-heat-resistant aluminum alloy and a preparation method thereof. The strength and plasticity are balanced by Cu, Mn and other alloying elements, but the synergistic regulation of the multi-scale double-network precipitation structure constructed by Sc, Zr, Er, Ti, B and other micro-alloying elements is limited, and the comprehensive problems of fine-grained high-precipitation strengthening, long-life fatigue crack resistance, high bending energy absorption, good thermal conductivity, and profile straightness and dimensional stability of the profile under high extrusion ratio conditions have not been systematically solved. For example, the 6061-T6 profile disclosed in some documents still cannot meet the increasingly stringent safety and lightweight design requirements of the battery tray structure in terms of three-point bending and fatigue life. SUMMARY

[0004] The purpose of the present application is to provide an aluminum alloy profile for battery tray extrusion and a processing technology thereof, which solves the problem that the existing 6xxx series aluminum alloy cannot simultaneously consider high yield strength, high bending energy absorption, long-life fatigue crack resistance, and high extrusion ratio, profile straightness control, fine-grained high-precipitation strengthening, and thermal conductivity required for thermal management of the power battery tray. By constructing a Si-Mg-Cu-Mn-Fe-Sc-Zr-Er-Ti-B multi-element micro-alloying system, and synergizing with the aluminum-manganese-zirconium-titanium-boron micro-alloy master alloy B1, semi-continuous casting-two-stage homogenization-extrusion-online quenching-two-stage artificial aging integrated process, the controllable evolution of the Al-derived double-network precipitation intermediate ID to the extruded double-network precipitation structure is realized, and a multi-scale strengthening framework of the first network nanometer precipitates and the second network sub-micron to micron-sized precipitates is constructed in the intracrystalline / sub-grain boundary and the grain boundary / sub-structure region, so that the strength, plasticity, bending energy absorption, fatigue life, extrusion forming precision and service thermal stability are comprehensively balanced.

[0005] In order to achieve the above-mentioned purpose, the present application provides the following technical solutions: An aluminum alloy profile for extruding battery trays comprises, by mass percentage: Si 0.78–0.92 wt%, Mg 0.72–0.90 wt%, Mn 0.55–0.70 wt%, Fe 0.10–0.15 wt%, Cu 0.05–0.15 wt%, Sc 0.05–0.10 wt%, Zr 0.05–0.10 wt%, Er 0.02–0.06 wt%, Ti 0.015–0.04 wt%, B 0.001–0.02 wt%, with the balance being Al and unavoidable impurities. The content of any single unavoidable impurity is not greater than 0.03 wt%, and the total content of unavoidable impurities is not greater than 0.10 wt%. The aluminum alloy profile for extruding the battery tray, after extrusion and aging treatment, exhibits a double-network precipitate structure in its microstructure. The double-network precipitate structure includes: The recrystallization volume fraction is 60–95%, and the equivalent diameter of the recrystallized grains is 5–18 μm; A first network nanoprecipitate distributed within the grain and subgrain boundary regions, the first network nanoprecipitate being selected from one or more of β″ phase, Q′ phase, and nanoscale L12 structure precipitates, the first network nanoprecipitate having an equivalent diameter of 5–20 nm and a volume fraction of 2.5–5.0 vol%. The second network of submicron to micron-sized precipitates is distributed in grain boundaries, subgrain boundaries, and some intragranular substructure regions. The second network of submicron to micron-sized precipitates includes one or more of Al6Mn phase, Al(FeMn)Si phase, and submicron to micron-sized coarsened L12 structure precipitates. The average particle size of the second network of submicron to micron-sized precipitates is 0.2 to 1.0 μm, and the volume fraction is 0.5 to 2.0 vol.

[0006] Furthermore, the equivalent diameter of the first network nano-precipitated phase is 8–15 nm, the average particle size of the second network submicron to micron-scale precipitated phase is 0.3–0.8 μm, and the volume fraction of the second network submicron to micron-scale precipitated phase is 0.8–1.5 vol.

[0007] Furthermore, the aluminum alloy profile for extruding the battery tray is formed by two-stage homogenization heat treatment of aluminum alloy ingots to create Al-derived double-network precipitate intermediate ID, which is then obtained by extrusion forming and two-stage artificial aging. The Al-derived double-network precipitate intermediate ID has the following microstructure characteristics: After homogenization, the intragranular and subgrain boundary regions contain one or more of the following: solute atom clusters with an equivalent diameter of 5–15 nm and a volume fraction of 1–3 vol%. The solute atom clusters evolve into the β″ and Q′ phases in the first network nano-precipitates of claim 1 during subsequent extrusion and aging. The L12 fine precipitates partially grow and coarsen during subsequent extrusion and aging, forming the coarsened L12 structure precipitates in the second network submicron to micron-scale precipitates of claim 1. The grain boundaries and interdendritic regions contain Al6Mn and Al(FeMn)Si phases with an average grain size of 0.2–0.8 μm and a volume fraction of 0.5–2.0 vol%.

[0008] Furthermore, after extrusion and aging treatment, the aluminum alloy profile for extruding battery trays has a yield strength of 290–320 MPa, a tensile strength of 320–360 MPa, and an elongation after fracture of 13–16% at room temperature.

[0009] As a concept of this invention, the aluminum alloy profile designed with specific composition and controlled by a dual-network precipitate structure is mainly used to enhance the comprehensive mechanical properties and structural reliability of power battery trays during service. On the one hand, by controlling the contents of Si, Mg, and Cu within the moderate range defined in claim 1, a sufficient number and stability of β″ phase, Q′ phase, and nanoscale L12 structure precipitates are formed, while avoiding the severe decrease in thermal conductivity and the tendency for hot cracking during extrusion caused by excessive solid solution strengthening. On the other hand, by introducing Mn and co-controlling the Fe content, the size and volume fraction of Al6Mn phase and Al(FeMn)Si phase are promoted during ingot casting and subsequent homogenization, and these phases evolve into submicron to micron-scale precipitates in the second network during extrusion-aging, effectively hindering grain boundary migration, dislocation movement, and microcrack propagation at the grain boundary and substructural scale. Furthermore, by utilizing Sc, Zr, Er, Ti, and B multi-element microalloying elements to form stable L12 fine precipitate nuclei and metastable solute atomic clusters, an Al-derived dual network is achieved. The precipitated intermediate ID exhibits excellent microstructure uniformity and controllable recrystallization nucleation point distribution at both the secondary dendrite and grain scales, resulting in a fine-grained microstructure with a recrystallization volume fraction of 60–95% and an equivalent grain diameter of 5–18 μm after extrusion and two-stage artificial aging. By precisely controlling the volume fraction and equivalent diameter of the first network of nano-precipitates, and synergistically matching them with the average particle size, volume fraction, and aspect ratio of the second network of submicron to micron-sized precipitates, this design achieves 13–16% elongation after fracture, superior flexural energy absorption capacity, and fatigue life compared to the 6061-T6 comparative profile, while ensuring a yield strength of 290–320 MPa and a tensile strength of 320–360 MPa. This meets the comprehensive requirements of new energy vehicle power battery trays for strength, plasticity, flexural energy absorption, fatigue crack resistance, and thermal conductivity under high extrusion ratio and complex cross-sectional structures.

[0010] This invention also discloses a processing technology for aluminum alloy profiles used in battery tray extrusion, comprising the following steps: S1. Melting and Alloying: High-purity aluminum ingots are added to a melting furnace and heated to melt. Silicon metal, a magnesium-containing aluminum-based master alloy, a manganese-containing aluminum-based master alloy, and a copper-containing aluminum-based master alloy are added sequentially. Then, aluminum-manganese-zirconium-titanium-boron microalloying master alloy B1, a scandium-containing aluminum-based master alloy, an erbium-containing aluminum-based master alloy, and a zirconium-containing aluminum-based master alloy are added to the melt. The melt is stirred, and the sample composition is tested to ensure that the contents of Mn, Sc, Zr, and Er in the melt meet the following requirements: Mn 0.55–0.70 wt%, Sc 0.05–0.10 wt%, Zr 0.05–0.10 wt%, and Er 0.0 wt%. 2 to 0.06 wt%; and by selecting raw materials of appropriate purity grade to control the Fe content within the range of 0.10 to 0.15 wt%; and by adjusting the amount of silicon metal, magnesium-containing aluminum-based master alloy, copper-containing aluminum-based master alloy and aluminum-manganese-zirconium-titanium-boron microalloy master alloy B1, so that the contents of Si, Mg, Cu, Ti and B in the melt, together with Mn, Fe, Sc, Zr and Er, all meet the range defined in claim 1, wherein the Zr element is adjusted by the aluminum-manganese-zirconium-titanium-boron microalloy master alloy B1 and the zirconium-containing aluminum-based master alloy to meet the range of 0.05 to 0.10 wt%.

[0011] S2, Refining, Degassing and Filtration: The alloy melt obtained in step S1 is refined and degassed, and then filtered to obtain a purified alloy melt. S3. Casting and two-stage homogenization: The purified alloy melt obtained in step S2 is semi-continuously cast to obtain an aluminum alloy ingot; the aluminum alloy ingot is subjected to two-stage homogenization treatment at a first-stage temperature and a second-stage temperature higher than the first-stage temperature, and then cooled to room temperature to obtain Al-derived double-network precipitation intermediate ID. S4. Extrusion and online quenching: The Al-derived double network precipitate intermediate ID obtained in step S3 is sawn into extrusion billets. The extrusion billets are heated and then hot extruded through an extruder to form a hot extrusion, so that the extrusion outlet temperature is controlled at 530-550℃ to ensure that the alloying elements are basically dissolved. The hot-extruded profile is quenched online at the extrusion exit, and the profile is cooled from the extrusion exit temperature to below 60°C at a cooling rate of not less than 20°C / s to obtain a quenched profile. S5. Stretch straightening and two-stage artificial aging: The quenched profile obtained in step S4 is subjected to stretch straightening treatment, followed by two-stage artificial aging treatment at a first aging temperature and a second aging temperature higher than the first aging temperature, and then cooled to room temperature to form a double network precipitation structure, finally obtaining an aluminum alloy profile for battery tray extrusion.

[0012] Furthermore, the chemical composition of the aluminum-manganese-zirconium-titanium-boron microalloy master alloy B1 used to prepare the aluminum alloy profile for extruding the battery tray, by mass percentage, includes: Mn of 8-12 wt%, Zr of 3-6 wt%, Ti of 3-8 wt%, B of 0.5-2.0 wt%, with the balance being Al and unavoidable impurities.

[0013] Further, in step S1, the high-purity aluminum ingot is heated to 730-760°C to completely melt it. Silicon metal, magnesium-containing aluminum-based master alloy, manganese-containing aluminum-based master alloy, and copper-containing aluminum-based master alloy are added sequentially. The melt temperature is then adjusted to 730-760°C and held for 10-20 minutes. Then, aluminum-manganese-zirconium-titanium-boron microalloy master alloy B1, scandium-containing aluminum-based master alloy, erbium-containing aluminum-based master alloy, and zirconium-containing aluminum-based master alloy are added to the melt. The mixture is stirred for 10-20 minutes to ensure uniform composition. The contents of Si, Mg, Cu, Mn, Fe, Sc, Zr, Er, Ti, and B in the melt are controlled by online spectral analysis to meet the ranges defined in claim 1. Further, in step S2, high-purity argon or high-purity nitrogen is introduced into the alloy melt for online rotor degassing for 8-20 minutes, and a refining flux for aluminum alloy melt composed of sodium chloride and potassium chloride is added to the surface and interior of the melt. The mass ratio of sodium chloride to potassium chloride is 40:60 to 60:40, and the amount of the refining flux added is 0.1-0.5 wt% of the total alloy mass. After standing for 5-15 minutes, the purified alloy melt is obtained by filtration through a ceramic filter plate.

[0014] Furthermore, in step S3, the purified alloy melt is semi-continuously cast at a pouring temperature of 710-740℃ to obtain an aluminum alloy ingot with a diameter of 200-600mm. The two-stage homogenization process involves holding the aluminum alloy ingot at a temperature of 470–485°C for 6–12 hours in the first stage, then holding it at a temperature of 510–520°C for 3–6 hours in the second stage, followed by air cooling or furnace cooling to room temperature at a cooling rate of 20–40°C / h to obtain the Al-derived double-network precipitation intermediate ID.

[0015] Further, in step S4, the Al-derived double-network precipitated intermediate ID is sawn into an extrusion billet, the extrusion billet is heated to 480-495°C and held for 2-3 hours, the extrusion die is preheated to 460-480°C, and the extrusion profile is extruded through a horizontal extruder under the conditions of an extrusion ratio of 10-18 and an extrusion speed of 1.0-2.5 m / min, so that the extrusion outlet temperature is controlled at 530-550°C; The online quenching process involves sending the hot-extruded profile into a water spray cooling zone or a water mist cooling zone within 3 seconds after demolding, and cooling the profile from 530-550℃ to below 60℃ within 10-20 seconds at a cooling rate of not less than 20℃ / s. In step S5, the quenched profile is subjected to a tensile deformation of 1-3% for straightening; then, a two-stage artificial aging process is performed: first, it is held at a first aging temperature of 150-165℃ for 3-5 hours, then held at a second aging temperature of 180-190℃ for 3-6 hours, and then cooled to room temperature.

[0016] Furthermore, the aluminum alloy profile for extruding the battery tray has a better bending energy absorption capacity than the 6061-T6 comparative profile under three-point bending conditions, and the bending displacement is increased by no less than 10% under the same maximum load conditions.

[0017] Furthermore, the aluminum alloy profile for extruding the battery tray, under symmetrical tensile and compressive fatigue conditions, at 10... 5 ~10 6 The fatigue life within the cycle range is 20-30% higher than that of the 6061-T6 comparative profile, and 10-20% higher than that of the comparative 6xxx series aluminum alloys with only a single nano-precipitation network.

[0018] Furthermore, the aluminum alloy profile for extruding the battery tray is used to support the battery cell module in the power battery tray of new energy vehicles, and absorbs and dissipates the impact energy through the dual-network precipitation structure under vehicle collision conditions.

[0019] As another concept of this invention, this invention adopts a processing technology design with Al-derived dual-network precipitate intermediate ID as the core intermediate structure, mainly used to enhance the process window tolerance and service stability of aluminum alloy profiles under complex extrusion conditions and harsh service environments. On the one hand, by precisely controlling the content of elements such as Mn, Fe, Sc, Zr, Er, Ti, and B in the S1 melting and alloying stages, and utilizing the aluminum-manganese-zirconium-titanium-boron microalloy master alloy B1 to provide a stable source of Zr, Ti, and B, the ingot forms a dispersed solute atom cluster and L12 fine precipitate nuclei in the subsequent two-stage homogenization. On the other hand, in the S3 stage, through the combination of the first-stage homogenization at 470-485℃ and the second-stage homogenization at 510-520℃, as well as controlled cooling at 20-40℃ / h, the grain size and volume fraction of the second phase at the secondary dendrite grain boundaries are placed in a range conducive to recrystallization and precipitation evolution, thereby constructing the controllable microstructure platform of Al-derived dual-network precipitate intermediate ID. Building upon this, S4 extrusion and online quenching, by stably controlling the extrusion outlet temperature at 530–550℃ and achieving rapid cooling at a rate not less than 20℃ / s, ensures sufficient solid solution of alloying elements and inhibits excessive growth of coarse second phases. This provides a highly supersaturated matrix condition for the differentiated nucleation and growth of subsequent first-network nano-precipitates and second-network submicron to micron-scale precipitates. S5 two-stage artificial aging, through a combination of low-temperature aging at 150–165℃ and high-temperature aging at 180–190℃, first promotes the transformation of solute atomic clusters into β″ phase, Q′ phase, and nanoscale L12 structure precipitates, and then moderately... This approach promotes the growth and partial coarsening of fine L12 precipitates, thereby forming a two-scale precipitate framework with controllable volume fraction and particle size in the intragranular / subgrain boundary and grain boundary / substructure regions, respectively. This concept allows for full-process control of the evolution of the Al-derived dual-network precipitate intermediate ID through the process pathway. This ensures that the dual-network precipitate structure maintains high stability and repeatability under different extrusion ratios, extrusion speeds, and cross-sectional complexities, significantly improving profile straightness and dimensional accuracy, and guaranteeing excellent energy absorption capacity and fatigue life under actual vehicle collision conditions and high-cycle fatigue loads.

[0020] In this invention, there is a significant synergistic effect between alloying elements and the dual-network precipitate structure. Si and Mg constitute the main components of the β″ and Q′ phases in 6xxx series aluminum alloys. The introduction of Cu further enhances the formation tendency of the Q′ phase and the stable L12 structure precipitate, enabling the first network nano-precipitate to exist stably within a volume fraction of 2.5–5.0 vol% and an equivalent diameter of 5–20 nm, thereby improving yield strength and tensile strength from the perspectives of dislocation pinning and grain refinement. Mn and Fe form the Al6Mn and Al(FeMn)Si phases, constructing the framework of the second network submicron to micron-scale precipitate, with an average particle size controlled at 0.2–1.0 μm and a volume fraction controlled at 0.5–2.0 vol%. This method effectively passivates grain boundaries, inhibits grain boundary migration and rapid propagation of microcracks along grain boundaries, and avoids intergranular fracture caused by brittle phases in continuous networks. The synergistic formation of nanoscale L12 fine precipitates and metastable solute atomic clusters by Sc, Zr, Er, Ti, and B multi-element microalloying elements results in high-density dispersed particles of Al-derived dual-network precipitates (ID) at both the secondary dendrite and grain scales. During extrusion and two-stage artificial aging, some of these particles transform into β″, Q′, and nanoscale L12 structure precipitates, forming the first network; the other part grows and coarsens, forming the second network together with the Al6Mn and Al(FeMn)Si phases. By controlling the volume fraction and particle size matching of the two types of networks, this invention significantly improves elongation after fracture, bending displacement, and bending energy absorption while maintaining high yield strength and tensile strength, and increases the yield strength by 10%. 5 ~10 6 The fatigue life within the cycle range is improved, while the thermal conductivity is reduced due to excessive solid solution atomic content, thereby achieving comprehensive synergistic optimization between strength, plasticity, fatigue performance, thermal conductivity and forming accuracy.

[0021] Beneficial technical effects 1. This invention constructs a Si-Mg-Cu-Mn-Fe-Sc-Zr-Er-Ti-B multi-element microalloying system and forms a dual-network precipitate structure with specific recrystallization volume fraction and grain size under an extrusion-online quenching-two-stage artificial aging process. This allows the first network of nano-precipitates within the grains and subgrain boundaries to synergize with the second network of submicron to micron-sized precipitates in the grain boundaries and substructure regions in terms of volume fraction and grain size. As a result, a yield strength of 290–320 MPa, a tensile strength of 320–360 MPa, and an elongation at break of 13–16% can be obtained simultaneously at room temperature. Compared with traditional 6061-T6 profiles, this invention has significant advantages in terms of strength and plasticity, meeting the basic requirements of power battery trays in terms of lightweighting and structural safety.

[0022] 2. This invention obtains Al-derived dual-network precipitate intermediate ID during casting and two-stage homogenization processes, ensuring that the particle size and volume fraction of Al6Mn and Al(FeMn)Si phases in the ingot are within the optimized range. Combined with an extrusion outlet temperature of 530–550℃, an online quenching cooling rate of no less than 20℃ / s, and a two-stage artificial aging regime, it effectively suppresses abnormal grain growth and continuous networking of coarse grain boundary second phases during extrusion. This improves the stability and repeatability of the dual-network precipitate structure under different extrusion ratios and extrusion speeds, thereby significantly improving the straightness and dimensional accuracy of complex cross-section profiles, facilitating the integrated assembly and tolerance control of power battery trays.

[0023] 3. This invention significantly improves the bending displacement and total energy absorption capacity of profiles under three-point bending conditions by rationally controlling the volume fraction and particle size of the first network nano-precipitated phase and the second network submicron to micron-sized precipitated phase. This results in a bending displacement increase of no less than 10% under the same maximum load conditions, and also improves performance under tensile-compressive symmetrical fatigue conditions. 5 ~10 6 The fatigue life within the cycle range is 20-30% higher than that of the 6061-T6 profile, and 10-20% higher than that of the 6xxx series aluminum alloys with only a single nano-precipitation network. This significantly improves the impact safety and service reliability of the power battery tray under vehicle collision conditions and long-term vibration loads.

[0024] 4. By controlling the content of microalloying elements such as Sc, Zr, Er, Ti, and B within the narrow range defined in claim 1, this invention ensures sufficient L12 fine precipitate nuclei and solute atom clusters for strengthening and grain refinement, while avoiding excessively high solid solution atom concentrations that would lead to a significant decrease in thermal conductivity. This allows the profile to maintain high strength and long fatigue life while still possessing high thermal conductivity beneficial to the thermal management of power battery modules. It helps to quickly conduct and diffuse heat under normal operating conditions and thermal runaway conditions, reducing the risk of localized overheating of the battery cell at the system level and improving the thermal safety of the power battery system for new energy vehicles. Attached Figure Description

[0025] Figure 1 The effect of Si content on yield strength and elongation after fracture in this invention.

[0026] Figure 2 The effect of the volume fraction of the first network nanoprecipitated phase on yield strength and elongation after fracture in this invention.

[0027] Figure 3 The effect of the submicron to micron-level precipitate volume fraction of the second network on yield strength and elongation after fracture in this invention.

[0028] Figure 4XPS survey spectrum of the first network nanoprecipitated phase region in Example 1 of the present invention.

[0029] Figure 5 XPS survey spectrum of the second network submicron–micron precipitated phase region in Embodiment 1 of the present invention.

[0030] Figure 6 The image shows the XRD pattern of the double-network precipitation structure of the aluminum alloy profile for battery tray extrusion in Embodiment 1 of the present invention.

[0031] Figure 7 This is a topographic image of the double-network precipitated structure of the aluminum alloy profile for battery tray extrusion in Embodiment 1 of the present invention. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0033] Example 1: This example provides an aluminum alloy profile for extruding battery trays. Its chemical composition, by mass percentage, includes: Si 0.85wt%, Mg 0.81wt%, Mn 0.62wt%, Fe 0.12wt%, Cu 0.10wt%, Sc 0.075wt%, Zr 0.075wt%, Er 0.04wt%, Ti 0.028wt%, B 0.010wt%, with the balance being Al and unavoidable impurities. In this example, the content of a single unavoidable impurity is no greater than 0.03wt%, and the total content of unavoidable impurities is no greater than 0.10wt%.

[0034] The aluminum alloy profile for extruding the battery tray in this embodiment exhibits a dual-network precipitate structure in its microstructure after extrusion and aging treatment. This dual-network precipitate structure includes: a recrystallization volume fraction of 78% and an equivalent diameter of 11 μm for the recrystallized grains; a first network nano-precipitate distributed within the grain boundaries and subgrain boundary regions (selected from β″ phase, Q′ phase, and nanoscale L12 structure precipitates, with an equivalent diameter of 12 nm and a volume fraction of 3.8 vol%); and a second network submicron to micron-sized precipitate distributed within grain boundaries, subgrain boundaries, and some intragranular substructure regions. The precipitated phases include Al6Mn phase, Al(FeMn)Si phase, and submicron to micron coarsened L12 structure precipitates. In this embodiment, the average particle size of the second network submicron to micron precipitates is 0.6 μm, and the volume fraction is 1.2 vol%. This embodiment also satisfies the further limiting requirements of claim 2. In this embodiment, the equivalent diameter of the first network nanoprecipitate (12 nm) is in the range of 8–15 nm, the average particle size of the second network submicron to micron precipitates (0.6 μm) is in the range of 0.3–0.8 μm, and the volume fraction of the second network submicron to micron precipitates (1.2 vol%) is in the range of 0.8–1.5 vol%.

[0035] The aluminum alloy profile for extruding battery trays in this embodiment is formed by two-stage homogenization heat treatment of aluminum alloy ingots to create Al-derived double-network precipitate intermediate ID. This Al-derived double-network precipitate intermediate ID is then obtained through extrusion forming and two-stage artificial aging. The Al-derived double-network precipitate intermediate ID in this embodiment has the following microstructural characteristics: After homogenization treatment, solute atom clusters with an equivalent diameter of 10 nm and a volume fraction of 2 vol% and L12 fine precipitate nuclei exist within the grain and subgrain boundary regions; the solute atom clusters in this embodiment evolve into the β″ and Q′ phases in the first network nano-precipitate phase of this embodiment during subsequent extrusion and aging; some of the L12 fine precipitate nuclei in this embodiment grow and coarsen during subsequent extrusion and aging, forming the coarsened L12 structure precipitate phase in the second network submicron to micron-scale precipitate phase of this embodiment; Al6Mn and Al(FeMn)Si phases with an average particle size of 0.5 μm and a volume fraction of 1.2 vol% exist in the grain boundary and interdendritic regions.

[0036] After extrusion and aging treatment, the aluminum alloy profile for extruding battery trays in this embodiment has a yield strength of 305 MPa, a tensile strength of 340 MPa, and an elongation after fracture of 14.5% at room temperature.

[0037] The processing steps for preparing aluminum alloy profiles for battery tray extrusion in this embodiment include the following steps. S1. Melting and Alloying: High-purity aluminum ingots are added to a melting furnace and heated to 745℃ until completely melted. Silicon metal, magnesium-containing aluminum-based master alloy, manganese-containing aluminum-based master alloy, and copper-containing aluminum-based master alloy are added sequentially. The melt temperature is then adjusted to 745℃ and held for 15 minutes. Then, aluminum-manganese-zirconium-titanium-boron microalloy master alloy B1, scandium-containing aluminum-based master alloy, erbium-containing aluminum-based master alloy, and zirconium-containing aluminum-based master alloy are added to the melt. The melt is stirred for 15 minutes to ensure homogeneity of composition. The sample composition is detected by online spectral analysis to ensure that the contents of Mn, Sc, Zr, and Er in the melt meet the following requirements: Mn is 0.62 wt%, Sc is 0. The Fe content is controlled at 0.12 wt% by selecting raw materials of appropriate purity grades. The content of Si in the melt is 0.85 wt%, Mg is 0.81 wt%, Cu is 0.10 wt%, Ti is 0.028 wt%, and B is 0.010 wt% by adjusting the amount of silicon metal, magnesium-containing aluminum-based master alloy, copper-containing aluminum-based master alloy, and aluminum-manganese-zirconium-titanium-boron microalloy master alloy B1. The chemical composition of the aluminum-manganese-zirconium-titanium-boron microalloy master alloy B1 used in the preparation of the aluminum alloy profile for extruding the battery tray in this embodiment, by mass percentage, includes: Mn 10wt%, Zr 4.5wt%, Ti 5.5wt%, B 1.25wt%, with the balance being Al and unavoidable impurities.

[0038] S2. Refining, Degassing, and Filtration: High-purity argon gas is introduced into the alloy melt obtained in step S1 for online degassing by a rotor for 14 minutes. A refining flux for aluminum alloy melt, composed of sodium chloride and potassium chloride, is added to the surface and interior of the melt. In this embodiment, the mass ratio of sodium chloride to potassium chloride is 50:50, and the amount of refining flux added is 0.3 wt% of the total alloy mass. After standing for 10 minutes, the melt is filtered through a ceramic filter plate to obtain purified alloy melt. S3. Casting and Two-Stage Homogenization: The purified alloy melt obtained in step S2 is semi-continuously cast at a pouring temperature of 725°C to obtain an aluminum alloy ingot with a diameter of 400 mm. The aluminum alloy ingot of this embodiment is held at a first-stage temperature of 478°C for 9 hours, and then held at a second-stage temperature of 515°C for 4.5 hours. After that, it is air-cooled to room temperature at a cooling rate of 30°C / h to obtain Al-derived double-network precipitation intermediate ID.

[0039] S4. Extrusion and Online Quenching: The Al-derived double-network precipitated intermediate ID obtained in step S3 is sawn into extrusion blanks. The extrusion blanks of this embodiment are heated to 488°C and held at that temperature for 2.5 hours. The extrusion die is preheated to 470°C. Under the conditions of an extrusion ratio of 14 and an extrusion speed of 1.8 m / min, the hot extrusion profile is formed by a horizontal extrusion press, and the extrusion outlet temperature is controlled at 540°C. The hot extruded profile is then online quenched at the extrusion outlet. The hot extruded profile is sent into the water spray cooling zone within 3 seconds after demolding and cooled from 540°C to below 60°C within 15 seconds at a cooling rate of 25°C / s to obtain the quenched profile.

[0040] S5. Stretch straightening and two-stage artificial aging: Apply 2% stretch deformation to the quenched profile obtained in step S4 for straightening treatment, and then perform two-stage artificial aging: first, hold at a first aging temperature of 158℃ for 4 hours, then hold at a second aging temperature of 185℃ for 4.5 hours, and then cool to room temperature to form a double network precipitation structure, finally obtaining an aluminum alloy profile for battery tray extrusion.

[0041] The aluminum alloy profile for battery tray extrusion in this embodiment exhibits superior bending energy absorption capacity under three-point bending conditions compared to the 6061-T6 comparative profile, with a bending displacement increase of at least 10% under the same maximum load. The aluminum alloy profile for battery tray extrusion in this embodiment also demonstrates superior bending energy absorption capacity under symmetrical tensile-compressive fatigue conditions at 10... 5 ~10 6 The fatigue life within the cycle range is 20-30% higher than that of the 6061-T6 comparative profile, and further 10-20% higher than that of the comparative 6xxx series aluminum alloys with only a single nano-precipitation network. The aluminum alloy profile for battery tray extrusion in this embodiment is used to support the battery cell module in the power battery tray of new energy vehicles, and absorbs and dissipates impact energy through the dual-network precipitation structure under vehicle collision conditions.

[0042] Features of Example 1: This example employs a moderate parameter configuration strategy, with chemical composition, microstructure parameters, and process parameters all selected within the middle range (40-60%) of their respective ranges, ensuring process stability and repeatability of product performance. The alloy contains moderate amounts of key strengthening elements such as Si, Mg, and Cu. The configuration of 3.8 vol% volume fraction of the first network nano-precipitates and 1.2 vol% volume fraction of the second network submicron to micron-sized precipitates achieves a good balance between strength and plasticity. The mechanical properties of 305 MPa yield strength, 340 MPa tensile strength, and 14.5% elongation after fracture demonstrate comprehensive performance advantages. This example also satisfies the further limitations of claim 2, with the equivalent diameter of the first network precipitate (12 nm), the average particle size of the second network submicron to micron-sized precipitates (0.6 μm), and the volume fraction of the second network submicron to micron-sized precipitates (1.2 vol%) all falling within a more stringent range, verifying the feasibility of this optimization range. This embodiment is applicable to standardized power battery tray applications where both strength and plasticity are required, and is particularly suitable for manufacturing structural components of new energy passenger vehicle battery packs under mass production conditions where process stability is critical.

[0043] Example 2: This example provides an aluminum alloy profile for extruding battery trays. Its chemical composition, by mass percentage, includes: Si 0.90 wt%, Mg 0.87 wt%, Mn 0.65 wt%, Fe 0.13 wt%, Cu 0.13 wt%, Sc 0.09 wt%, Zr 0.09 wt%, Er 0.05 wt%, Ti 0.035 wt%, B 0.016 wt%, with the balance being Al and unavoidable impurities. In this example, the content of a single unavoidable impurity is no greater than 0.03 wt%, and the total content of unavoidable impurities is no greater than 0.10 wt%.

[0044] The aluminum alloy profile for extruding battery trays in this embodiment exhibits a dual-network precipitate structure in its microstructure after extrusion and aging treatment. This dual-network precipitate structure includes: a recrystallization volume fraction of 68% and an equivalent diameter of 8 μm for the recrystallized grains; a first network nano-precipitate distributed within the grain boundaries and subgrain boundary regions, wherein the first network nano-precipitate is selected from β″ phase, Q′ phase, and nanoscale L12 structure precipitates, with an equivalent diameter of 14 nm and a volume fraction of 4.5 vol%; and a second network submicron to micron-sized precipitates distributed within grain boundaries, subgrain boundaries, and some intragranular substructure regions, including Al6Mn phase, Al(FeMn)Si phase, and submicron to micron-sized coarsened L12 structure precipitates, with an average particle size of 0.7 μm and a volume fraction of 1.6 vol%.

[0045] The aluminum alloy profile for extruding battery trays in this embodiment is formed by two-stage homogenization heat treatment of aluminum alloy ingots to create Al-derived double-network precipitate intermediate ID. This Al-derived double-network precipitate intermediate ID is then obtained through extrusion forming and two-stage artificial aging. The Al-derived double-network precipitate intermediate ID in this embodiment has the following microstructural characteristics: After homogenization treatment, solute atom clusters with an equivalent diameter of 12 nm and a volume fraction of 2.5 vol% and L12 fine precipitate nuclei exist within the grains and subgrain boundaries; these solute atom clusters evolve into the β″ and Q′ phases in the first network nano-precipitate phase of this embodiment during subsequent extrusion and aging; the L12 fine precipitate nuclei partially grow and coarsen during subsequent extrusion and aging, forming the coarsened L12 structure precipitate phase in the second network submicron to micron-scale precipitate phase of this embodiment; and Al6Mn and Al(FeMn)Si phases with an average particle size of 0.6 μm and a volume fraction of 1.6 vol% exist in the grain boundaries and interdendritic regions.

[0046] After extrusion and aging treatment, the aluminum alloy profile for extruding battery trays in this embodiment has a yield strength of 315 MPa, a tensile strength of 355 MPa, and an elongation after fracture of 13.5% at room temperature.

[0047] The processing steps for preparing the aluminum alloy profile for battery tray extrusion in this embodiment include the following: S1. Melting and Alloying: High-purity aluminum ingots are added to a melting furnace and heated to 755℃ until completely melted. Silicon metal, magnesium-containing aluminum-based master alloy, manganese-containing aluminum-based master alloy, and copper-containing aluminum-based master alloy are added sequentially. The melt temperature is then adjusted to 755℃ and held for 18 minutes. Next, aluminum-manganese-zirconium-titanium-boron microalloy master alloy B1, scandium-containing aluminum-based master alloy, erbium-containing aluminum-based master alloy, and zirconium-containing aluminum-based master alloy are added to the melt. The melt is stirred for 18 minutes to ensure homogeneity. The sample composition is analyzed by online spectral analysis to ensure that the contents of Mn, Sc, Zr, and Er in the melt meet the following requirements: Mn 0.65 wt%, Sc 0.65 wt%, and Sc 0.65 wt%. The Fe content is controlled at 0.13wt% by selecting raw materials of appropriate purity grades. The melt composition is achieved by adjusting the addition amounts of silicon metal, magnesium-containing aluminum-based master alloy, copper-containing aluminum-based master alloy, and aluminum-manganese-zirconium-titanium-boron microalloy master alloy B1, resulting in Si 0.90wt%, Mg 0.87wt%, Cu 0.13wt%, Ti 0.035wt%, and B 0.016wt%. The Zr content is adjusted to 0.09wt% by combining aluminum-manganese-zirconium-titanium-boron microalloy master alloy B1 and the zirconium-containing aluminum-based master alloy. The chemical composition of the aluminum-manganese-zirconium-titanium-boron microalloy master alloy B1 used in the preparation of the aluminum alloy profile for battery tray extrusion in this embodiment, by mass percentage, includes: Mn 11wt%, Zr 5.5wt%, Ti 7wt%, B 1.8wt%, with the balance being Al and unavoidable impurities.

[0048] S2. Refining, degassing and filtration: High-purity argon gas is introduced into the alloy melt obtained in step S1 for online degassing by rotor for 18 minutes. A refining flux for aluminum alloy melt, composed of sodium chloride and potassium chloride, is added to the surface and interior of the melt. In this embodiment, the mass ratio of sodium chloride to potassium chloride is 45:55. The amount of refining flux added in this embodiment is 0.4 wt% of the total mass of the alloy. After standing for 12 minutes, the purified alloy melt is obtained by filtration through a ceramic filter plate.

[0049] S3. Casting and Two-Stage Homogenization: The purified alloy melt obtained in step S2 is semi-continuously cast at a pouring temperature of 735°C to obtain an aluminum alloy ingot with a diameter of 500 mm. The aluminum alloy ingot of this embodiment is held at a first-stage temperature of 482°C for 10 h, and then held at a second-stage temperature of 518°C for 5 h. After that, it is air-cooled to room temperature at a cooling rate of 25°C / h to obtain Al-derived double-network precipitation intermediate ID.

[0050] S4. Extrusion and Online Quenching: The Al-derived double-network precipitated intermediate ID obtained in step S3 is sawn into extrusion blanks. The extrusion blanks of this embodiment are heated to 492°C and held at that temperature for 2.8 hours. The extrusion die is preheated to 475°C. Under the conditions of an extrusion ratio of 16 and an extrusion speed of 2.2 m / min, the hot extrusion profile is formed by a horizontal extrusion press, and the extrusion outlet temperature is controlled at 545°C. The hot extruded profile is online quenched at the extrusion outlet. The hot extruded profile is sent into the water spray cooling zone within 3 seconds after demolding, and the profile is cooled from 545°C to below 60°C within 18 seconds at a cooling rate of 30°C / s to obtain the quenched profile.

[0051] S5. Stretch straightening and two-stage artificial aging: Apply 2.5% stretch deformation to the quenched profile obtained in step S4 for straightening treatment, and then perform two-stage artificial aging: first, hold at a first aging temperature of 162℃ for 4.5h, then hold at a second aging temperature of 188℃ for 5h, and then cool to room temperature to form a double network precipitation structure, finally obtaining an aluminum alloy profile for battery tray extrusion.

[0052] The aluminum alloy profile for battery tray extrusion in this embodiment exhibits superior bending energy absorption capacity under three-point bending conditions compared to the 6061-T6 comparative profile, with a bending displacement increase of at least 10% under the same maximum load. The aluminum alloy profile for battery tray extrusion in this embodiment also demonstrates superior bending energy absorption capacity under symmetrical tensile-compressive fatigue conditions at 10... 5 ~10 6 The fatigue life within the cycle range is 20-30% higher than that of the 6061-T6 comparative profile, and further 10-20% higher than that of the comparative 6xxx series aluminum alloys with only a single nano-precipitation network. The aluminum alloy profile for battery tray extrusion in this embodiment is used to support the battery cell module in the power battery tray of new energy vehicles, and absorbs and dissipates impact energy through the dual-network precipitation structure under vehicle collision conditions.

[0053] Features of Example 2: This example employs a parameter configuration strategy biased towards high-strength performance optimization. The contents of major strengthening elements such as Si, Mg, and Cu in the chemical composition are all selected in the higher ranges (67-90%) of their respective ranges. Simultaneously, the contents of rare earth and transition metal elements such as Sc, Zr, and Er are also at a high level (75-90%), enhancing the precipitation strengthening effect by increasing the degree of alloying. In terms of microstructure, the volume fraction of the first network nano-precipitates reaches 4.5 vol%, and the volume fraction of the second network submicron to micron-sized precipitates is 1.6 vol%, both close to the upper limit of their respective ranges. The relatively low recrystallization volume fraction of 68% is beneficial for maintaining a high dislocation density to enhance the processing strengthening effect, and refining the recrystallized grains to 8 μm contributes to grain boundary strengthening. Regarding process parameters, the higher melting temperature of 755℃, homogenization temperatures of 482℃ / 518℃, aging temperatures of 162℃ / 188℃, and longer holding times promote sufficient element solid solution and effective formation of precipitates. The final mechanical properties achieved a yield strength of 315 MPa and a tensile strength of 355 MPa, both close to the upper limit of the range, demonstrating a significant strength advantage. The elongation after fracture of 13.5% also remained within the acceptable range. This embodiment is suitable for applications with particularly high strength requirements, such as power battery trays for high-performance new energy commercial vehicles or heavy-duty electric trucks, providing higher safety margins and structural integrity guarantees under conditions of large collision loads.

[0054] Example 3: This example provides an aluminum alloy profile for extruding battery trays, the chemical composition of which, by mass percentage, includes: Si 0.80wt%, Mg 0.75wt%, Mn 0.58wt%, Fe 0.11wt%, Cu 0.07wt%, Sc 0.06wt%, Zr 0.06wt%, Er 0.025wt%, Ti 0.020wt%, B 0.004wt%, with the balance being Al and unavoidable impurities. In this example, the content of a single unavoidable impurity is no greater than 0.03wt%, and the total content of unavoidable impurities is no greater than 0.10wt%.

[0055] The aluminum alloy profile for extruding the battery tray in this embodiment exhibits a dual-network precipitate structure in its microstructure after extrusion and aging treatment. This dual-network precipitate structure includes: a recrystallization volume fraction of 88% and an equivalent diameter of 15 μm for the recrystallized grains; a first network nanoprecipitate distributed within the grain boundaries and subgrain boundary regions (selected from β″ phase, Q′ phase, and nanoscale L12 structure precipitates, with an equivalent diameter of 10 nm and a volume fraction of 3.0 vol%); and a second network submicron to micron-sized precipitate distributed within grain boundaries, subgrain boundaries, and some intragranular substructure regions. The precipitated phases include Al6Mn phase, Al(FeMn)Si phase, and submicron to micron-scale coarsened L12 structure precipitates. In this embodiment, the average particle size of the second network submicron to micron-scale precipitates is 0.4 μm, and the volume fraction is 0.9 vol%. This embodiment also satisfies the further limiting requirements of claim 2. In this embodiment, the equivalent diameter of the first network nanoprecipitate (10 nm) is in the range of 8–15 nm, the average particle size of the second network submicron to micron-scale precipitates (0.4 μm) is in the range of 0.3–0.8 μm, and the volume fraction of the second network submicron to micron-scale precipitates (0.9 vol%) is in the range of 0.8–1.5 vol%.

[0056] The aluminum alloy profile for extruding battery trays in this embodiment is formed by two-stage homogenization heat treatment of aluminum alloy ingots to create an Al-derived double-network precipitate intermediate ID. This intermediate ID is then obtained through extrusion forming and two-stage artificial aging. The Al-derived double-network precipitate intermediate ID in this embodiment has the following microstructure characteristics: After homogenization treatment, solute atom clusters with an equivalent diameter of 8 nm and a volume fraction of 1.5 vol% and L12 fine precipitate nuclei exist within the grain and subgrain boundary regions; the solute atom clusters evolve into the β″ and Q′ phases in the first network nano-precipitate phase of this embodiment during subsequent extrusion and aging; the L12 fine precipitate nuclei partially grow and coarsen during subsequent extrusion and aging, forming the coarsened L12 structure precipitate phase in the second network submicron to micron-scale precipitate phase of this embodiment; Al6Mn and Al(FeMn)Si phases with an average particle size of 0.4 μm, a volume fraction of 0.9 vol%, and an aspect ratio of 1.5 exist in the grain boundary and interdendritic regions.

[0057] After extrusion and aging treatment, the aluminum alloy profile for extruding battery trays in this embodiment has a yield strength of 295 MPa, a tensile strength of 325 MPa, and an elongation after fracture of 15.5% at room temperature.

[0058] The processing steps for preparing the aluminum alloy profile for battery tray extrusion in this embodiment include the following: S1. Melting and Alloying: High-purity aluminum ingots are added to a melting furnace and heated to 735℃ until completely melted. Silicon metal, magnesium-containing aluminum-based master alloy, manganese-containing aluminum-based master alloy, and copper-containing aluminum-based master alloy are added sequentially. The melt temperature is then adjusted to 735℃ and held for 12 minutes. Next, aluminum-manganese-zirconium-titanium-boron microalloy master alloy B1, scandium-containing aluminum-based master alloy, erbium-containing aluminum-based master alloy, and zirconium-containing aluminum-based master alloy are added to the melt. The melt is stirred for 12 minutes to ensure homogeneity. The sample composition is analyzed by online spectral analysis to ensure that the contents of Mn, Sc, Zr, and Er in the melt meet the following requirements: Mn 0.58 wt%, Sc 0 wt%, and Sc 0 wt%. The composition of the aluminum alloy profile for battery tray extrusion in this embodiment is as follows: Mn 0.06 wt%, Zr 0.06 wt%, Er 0.025 wt%; and Fe content is controlled at 0.11 wt% by selecting raw materials of appropriate purity grade; and the content of Si in the melt is 0.80 wt%, Mg 0.75 wt%, Cu 0.07 wt%, Ti 0.020 wt%, and B 0.004 wt% by adjusting the amount of silicon metal, magnesium-containing aluminum-based master alloy, copper-containing aluminum-based master alloy, and aluminum-manganese-zirconium-titanium-boron microalloy master alloy B1, wherein Zr content is adjusted to meet 0.06 wt% by the combined use of aluminum-manganese-zirconium-titanium-boron microalloy master alloy B1 and zirconium-containing aluminum-based master alloy. The chemical composition of aluminum-manganese-zirconium-titanium-boron microalloy master alloy B1 used in the preparation of the aluminum alloy profile for battery tray extrusion in this embodiment, by mass percentage, includes: Mn 9 wt%, Zr 3.5 wt%, Ti 4 wt%, B 0.7 wt%, with the balance being Al and unavoidable impurities.

[0059] S2. Refining, degassing and filtration: High-purity nitrogen gas is introduced into the alloy melt obtained in step S1 for online degassing by rotor for 10 minutes. A refining flux for aluminum alloy melt, composed of sodium chloride and potassium chloride, is added to the surface and interior of the melt. In this embodiment, the mass ratio of sodium chloride to potassium chloride is 55:45. The amount of refining flux added in this embodiment is 0.2 wt% of the total mass of the alloy. After standing for 8 minutes, the purified alloy melt is obtained by filtration through a ceramic filter plate.

[0060] S3. Casting and Two-Stage Homogenization: The purified alloy melt obtained in step S2 is semi-continuously cast at a pouring temperature of 715°C to obtain an aluminum alloy ingot with a diameter of 300 mm. The aluminum alloy ingot of this embodiment is held at a first-stage temperature of 473°C for 7 hours, and then held at a second-stage temperature of 512°C for 3.5 hours. After that, it is furnace cooled to room temperature at a cooling rate of 35°C / h to obtain Al-derived double-network precipitation intermediate ID.

[0061] S4. Extrusion and Online Quenching: The Al-derived double-network precipitated intermediate ID obtained in step S3 is sawn into extrusion blanks. The extrusion blanks of this embodiment are heated to 483°C and held at that temperature for 2.2 hours. The extrusion die is preheated to 465°C. Under the conditions of an extrusion ratio of 12 and an extrusion speed of 1.3 m / min, the hot extrusion profile is formed by a horizontal extrusion press, and the extrusion outlet temperature is controlled at 535°C. The hot extruded profile is online quenched at the extrusion outlet. The hot extruded profile is sent into the water mist cooling zone within 3 seconds after demolding and cooled from 535°C to below 60°C within 12 seconds at a cooling rate of 22°C / s to obtain the quenched profile.

[0062] S5. Stretch straightening and two-stage artificial aging: Apply 1.5% stretch deformation to the quenched profile obtained in step S4 for straightening treatment, and then perform two-stage artificial aging: first, hold at a first aging temperature of 153℃ for 3.5h, then hold at a second aging temperature of 182℃ for 3.5h, and then cool to room temperature to form a double network precipitation structure, finally obtaining an aluminum alloy profile for battery tray extrusion.

[0063] The aluminum alloy profile for battery tray extrusion in this embodiment exhibits superior bending energy absorption capacity under three-point bending conditions compared to the 6061-T6 comparative profile, with a bending displacement increase of at least 10% under the same maximum load. The aluminum alloy profile for battery tray extrusion in this embodiment also demonstrates superior bending energy absorption capacity under symmetrical tensile-compressive fatigue conditions at 10... 5 ~10 6 The fatigue life within the cycle range is 20-30% higher than that of the 6061-T6 comparative profile, and further 10-20% higher than that of the comparative 6xxx series aluminum alloys with only a single nano-precipitation network. The aluminum alloy profile for battery tray extrusion in this embodiment is used to support the battery cell module in the power battery tray of new energy vehicles, and absorbs and dissipates impact energy through the dual-network precipitation structure under vehicle collision conditions.

[0064] Features of Example 3: This example employs a parameter configuration strategy that prioritizes high plasticity and high toughness. The contents of major strengthening elements such as Si, Mg, and Cu in the chemical composition are all selected in the lower ranges (13-20%) of their respective ranges. Simultaneously, the contents of rare earth and transition metal elements such as Sc, Zr, and Er are also at a low level (13-20%). This moderate reduction in alloying degree improves the material's plasticity and formability. Regarding the microstructure, the recrystallization volume fraction is as high as 88%, significantly higher than in Examples 1 and 2. Sufficient recrystallization helps reduce internal stress, improve the material's uniform deformation capacity and crack propagation resistance. The relatively large equivalent diameter of the recrystallized grains (15 μm) contributes to improved plasticity. The volume fractions of the first network nano-precipitates (3.0 vol%) and the second network submicron to micron-sized precipitates (0.9 vol%) are both at low levels. The moderate number of precipitates avoids excessive precipitation strengthening that could lead to a decrease in plasticity. Regarding process parameters, the relatively low melting temperature of 735℃, homogenization temperature of 473℃ / 512℃, aging temperature of 153℃ / 182℃, and short holding time, combined with a relatively fast homogenization cooling rate of 35℃ / h and a relatively low extrusion ratio of 12 and extrusion speed of 1.3m / min, are conducive to the formation of a fully recrystallized structure and moderate precipitation strengthening. The final mechanical properties achieve a yield strength of 295MPa and a tensile strength of 325MPa, near the lower limit of the range, while the elongation after fracture of 15.5% is close to the upper limit of the range, demonstrating excellent plasticity and toughness. This embodiment also satisfies the further limitations of claim 2. This embodiment is suitable for applications with high requirements for formability and impact energy absorption capacity, such as power battery tray profiles with complex cross-sectional shapes, battery pack structural components requiring subsequent bending or stamping, and new energy passenger vehicle battery systems with special requirements for energy absorption and occupant protection under conditions such as side collisions and pole impacts.

[0065] Example 4: This example provides an aluminum alloy profile for extruding battery trays. Its chemical composition, by mass percentage, includes: Si 0.91wt%, Mg 0.88wt%, Mn 0.69wt%, Fe 0.14wt%, Cu 0.14wt%, Sc 0.095wt%, Zr 0.095wt%, Er 0.055wt%, Ti 0.038wt%, B 0.018wt%, with the balance being Al and unavoidable impurities. In this example, the content of a single unavoidable impurity is no greater than 0.03wt%, and the total content of unavoidable impurities is no greater than 0.10wt%.

[0066] The aluminum alloy profile for extruding battery trays in this embodiment exhibits a dual-network precipitate structure in its microstructure after extrusion and aging treatment. This dual-network precipitate structure includes: a recrystallization volume fraction of 63% and an equivalent diameter of 6 μm for the recrystallized grains; a first network nano-precipitate distributed within the grain boundaries and subgrain boundary regions, wherein the first network nano-precipitate is selected from β″ phase, Q′ phase, and nanoscale L12 structure precipitates, with an equivalent diameter of 18 nm and a volume fraction of 4.7 vol%; and a second network submicron to micron-sized precipitates distributed within grain boundaries, subgrain boundaries, and some intragranular substructure regions, including Al6Mn phase, Al(FeMn)Si phase, and submicron to micron-sized coarsened L12 structure precipitates, with an average particle size of 0.9 μm and a volume fraction of 1.8 vol%.

[0067] The aluminum alloy profile for extruding battery trays in this embodiment is formed by two-stage homogenization heat treatment of aluminum alloy ingots to create Al-derived double-network precipitate intermediate ID. This Al-derived double-network precipitate intermediate ID is then obtained through extrusion forming and two-stage artificial aging. The Al-derived double-network precipitate intermediate ID in this embodiment has the following microstructural characteristics: After homogenization treatment, solute atom clusters with an equivalent diameter of 14 nm and a volume fraction of 2.8 vol% and L12 fine precipitate nuclei exist within the grains and subgrain boundaries; these solute atom clusters evolve into the β″ and Q′ phases in the first network nano-precipitate phase of this embodiment during subsequent extrusion and aging; the L12 fine precipitate nuclei partially grow and coarsen during subsequent extrusion and aging, forming the coarsened L12 structure precipitate phase in the second network submicron to micron-scale precipitate phase of this embodiment; and Al6Mn and Al(FeMn)Si phases with an average particle size of 0.75 μm and a volume fraction of 1.8 vol% exist in the grain boundaries and interdendritic regions.

[0068] After extrusion and aging treatment, the aluminum alloy profile for extruding battery trays in this embodiment has a yield strength of 318 MPa, a tensile strength of 358 MPa, and an elongation after fracture of 13.2% at room temperature.

[0069] The processing steps for preparing the aluminum alloy profile for battery tray extrusion in this embodiment include the following: S1. Melting and Alloying: High-purity aluminum ingots are added to a melting furnace and heated to 758℃ until completely melted. Silicon metal, magnesium-containing aluminum-based master alloy, manganese-containing aluminum-based master alloy, and copper-containing aluminum-based master alloy are added sequentially. The melt temperature is then adjusted to 758℃ and held for 19 minutes. Then, aluminum-manganese-zirconium-titanium-boron microalloy master alloy B1, scandium-containing aluminum-based master alloy, erbium-containing aluminum-based master alloy, and zirconium-containing aluminum-based master alloy are added to the melt. The melt is stirred for 19 minutes to ensure homogeneity of composition. The sample composition is detected by online spectral analysis to ensure that the contents of Mn, Sc, Zr, and Er in the melt meet the following requirements: Mn is 0.69 wt%, Sc is 0. The Fe content is controlled at 0.14 wt% by selecting raw materials of appropriate purity grades. The content of Si in the melt is 0.91 wt%, Mg is 0.88 wt%, Cu is 0.14 wt%, Ti is 0.038 wt%, and B is 0.018 wt% by adjusting the amount of silicon metal, magnesium-containing aluminum-based master alloy, copper-containing aluminum-based master alloy, and aluminum-manganese-zirconium-titanium-boron microalloy master alloy B1. The chemical composition of the aluminum-manganese-zirconium-titanium-boron microalloy master alloy B1 used in the preparation of the aluminum alloy profile for extruding the battery tray in this embodiment, by mass percentage, includes: Mn 11.5wt%, Zr 5.8wt%, Ti 7.5wt%, B 1.9wt%, with the balance being Al and unavoidable impurities.

[0070] S2. Refining, degassing and filtration: High-purity argon gas is introduced into the alloy melt obtained in step S1 for online degassing by rotor for 19 minutes. A refining flux for aluminum alloy melt, composed of sodium chloride and potassium chloride, is added to the surface and interior of the melt. In this embodiment, the mass ratio of sodium chloride to potassium chloride is 42:58. The amount of refining flux added in this embodiment is 0.45 wt% of the total mass of the alloy. After standing for 14 minutes, the purified alloy melt is obtained by filtration through a ceramic filter plate.

[0071] S3. Casting and Two-Stage Homogenization: The purified alloy melt obtained in step S2 is semi-continuously cast at a pouring temperature of 738°C to obtain an aluminum alloy ingot with a diameter of 550 mm. The aluminum alloy ingot of this embodiment is held at a first-stage temperature of 484°C for 11 h, and then held at a second-stage temperature of 519°C for 5.5 h. After that, it is furnace cooled to room temperature at a cooling rate of 22°C / h to obtain Al-derived double-network precipitation intermediate ID.

[0072] S4. Extrusion and Online Quenching: The Al-derived double-network precipitated intermediate ID obtained in step S3 is sawn into extrusion blanks. The extrusion blanks of this embodiment are heated to 494°C and held at that temperature for 2.9 hours. The extrusion die is preheated to 478°C. Under the conditions of an extrusion ratio of 17 and an extrusion speed of 2.4 m / min, the hot extrusion profile is formed by a horizontal extrusion press, and the extrusion outlet temperature is controlled at 548°C. The hot extruded profile is online quenched at the extrusion outlet. The hot extruded profile is sent into the water spray cooling zone within 3 seconds after demolding, and the profile is cooled from 548°C to below 60°C within 19 seconds at a cooling rate of 35°C / s to obtain the quenched profile.

[0073] S5. Stretch straightening and two-stage artificial aging: Apply 2.8% tensile deformation to the quenched profile obtained in step S4 for straightening treatment, and then perform two-stage artificial aging: first, hold at a first aging temperature of 164℃ for 4.8h, then hold at a second aging temperature of 189℃ for 5.8h, and then cool to room temperature to form a double network precipitation structure, finally obtaining an aluminum alloy profile for battery tray extrusion.

[0074] The aluminum alloy profile for battery tray extrusion in this embodiment exhibits superior bending energy absorption capacity under three-point bending conditions compared to the 6061-T6 comparative profile, with a bending displacement increase of at least 10% under the same maximum load. The aluminum alloy profile for battery tray extrusion in this embodiment also demonstrates superior bending energy absorption capacity under symmetrical tensile-compressive fatigue conditions at 10... 5 ~10 6 The fatigue life within the cycle range is 20-30% higher than that of the 6061-T6 comparative profile, and further 10-20% higher than that of the comparative 6xxx series aluminum alloys with only a single nano-precipitation network. The aluminum alloy profile for battery tray extrusion in this embodiment is used to support the battery cell module in the power battery tray of new energy vehicles, and absorbs and dissipates impact energy through the dual-network precipitation structure under vehicle collision conditions.

[0075] Features of Example 4: This example employs a boundary value verification parameter configuration strategy. Several key parameters are close to the upper limits of their respective ranges. In terms of chemical composition, Si (0.91 wt%), Mg (0.88 wt%), Mn (0.69 wt%), Sc (0.095 wt%), Zr (0.095 wt%), Er (0.055 wt%), Ti (0.038 wt%), and B (0.018 wt%) are all within the range of 88-93%, verifying the feasibility of the high-alloy design. Regarding the microstructure, the recrystallization volume fraction of 63% and grain diameter of 6 μm are close to the lower limit. The first network precipitate diameter is 18 nm and volume fraction is 4.7 vol%. The second network submicron to micron-sized precipitates have a particle size of 0.9 μm and a volume fraction of 1.8 vol%, both close to the upper limit, fully demonstrating the achievability of the boundary parameters. Process parameters such as melting temperature (758℃), homogenization temperature (484℃ / 519℃), extrusion ratio (17), and aging temperature (164℃ / 189℃) are all close to their upper limits, achieving sufficient elemental solution and precipitation strengthening. The final mechanical properties reach a yield strength of 318MPa and a tensile strength of 358MPa, close to the upper limit, while the elongation after fracture (13.2%) remains at a qualified level. This embodiment is suitable for applications with extremely high requirements for strength and collision safety performance, such as high-end new energy luxury vehicles and high-performance electric sports cars, providing sufficient support for maximizing the scope of protection of the claims.

[0076] Comparative Example 1: This example is essentially the same as Example 1, except that the Si content in the alloy is 0.74 wt%. The contents of other elements, melting temperature, homogenization, extrusion, and two-stage artificial aging process are all the same as in Example 1. This comparative example mainly examines the effect of low Si content on the volume fraction of the first network nano-precipitates and the strength-plasticity balance.

[0077] Comparative Example 2: Essentially the same as Example 1, except that the Si content in the alloy was 0.96 wt%, while all other elements and process parameters remained unchanged. This comparative example was used to verify the adverse effects of excessive Si leading to an increase in eutectic structure and coarse Q phase on bending energy absorption and fatigue life.

[0078] Comparative Example 3: Essentially the same as Example 1, except that the Mg content was 0.68 wt%, while all other elements and process conditions remained unchanged. This comparative example was used to investigate the weakening effect of insufficient Mg leading to a decrease in the volume fraction of the β″ phase on yield strength and tensile strength.

[0079] Comparative Example 4: This example is essentially the same as Example 1, except that the Mg content is 0.95 wt%, while the other components and processes remain unchanged. This comparative example is used to evaluate the effects of excessive Mg on over-precipitation strengthening, decreased plasticity and flexural energy absorption, and deterioration of fatigue performance.

[0080] Comparative Example 5: Essentially the same as Example 1, except that the Fe content was 0.20 wt%, while the remaining components and extrusion-aging regime were identical to Example 1. This comparative example was used to verify the negative impact of higher Fe content on fracture toughness and fatigue life due to increased Al(FeMn)Si brittle phase and increased aspect ratio.

[0081] Comparative Example 6: Basically the same as Example 1, except that the contents of Sc, Zr, and Er are 0.02wt%, 0.02wt%, and 0.01wt%, respectively. This comparative example is used to illustrate that when trace amounts of Sc-Zr-Er elements are insufficient, the dispersion precipitation of the L12 phase is weakened, and the double network structure is difficult to form.

[0082] Comparative Example 7: Essentially the same as Example 1, except that the boron component in the aluminum-manganese-zirconium-titanium-boron microalloy master alloy B1 was no longer added, reducing the B content in the alloy from 0.010 wt% to approximately 0 wt%. The contents of other elements and the process steps were consistent with Example 1. This comparative example was used to investigate the effect of excessively low B content on reduced grain refinement and recrystallized grain growth on performance.

[0083] Comparative Example 8: Essentially the same as Example 1, except that the extrusion exit temperature was reduced from 540°C to 520°C, while the remaining melting, homogenization, alloy composition, and online quenching conditions remained unchanged. This comparative example was used to verify the effect of insufficient solid solution of alloying elements due to a lower extrusion temperature, leading to a decrease in the volume fraction of the first network nano-precipitates.

[0084] Comparative Example 9: Essentially the same as Example 1, except that the cooling method during online quenching was changed from optimized water spray to weak water mist cooling, with a cooling rate of 10°C / s and other parameters remaining unchanged. This comparative example illustrates the consequence of insufficient cooling rate leading to premature precipitation during the extrusion outlet to room temperature process, thus weakening subsequent aging strengthening.

[0085] Comparative Example 10: Essentially the same as Example 1, except that the two-stage artificial aging process (158℃ / 4h + 185℃ / 4.5h) was changed to a single-stage artificial aging process (185℃ / 6h), and the first-stage low-temperature pre-aging was omitted. The remaining processes and compositions remained unchanged. This comparative example was used to verify the effect of the coarsening of the first network nanoprecipitate size on strength and fatigue performance when pre-aging is lacking.

[0086] Comparative Example 11: Essentially the same as Example 1, except that the first aging temperature in the two-stage artificial aging process was set to 145°C, the holding time remained 4 hours, and the second aging temperature and time were kept constant at 185°C / 4.5 hours, with other conditions remaining unchanged. This comparative example was used to investigate the effects of insufficient solute atom cluster formation and low volume fraction of the first network nano-precipitated phase when the pre-aging temperature was too low.

[0087] Comparative Example 12: Essentially the same as Example 1, except that the temperature of the second stage of the two-stage homogenization treatment was 505℃, and the holding time remained 4.5h. The temperature and time of the first stage remained unchanged at 478℃ / 9h, and the remaining process steps and composition were also unchanged. This comparative example was used to verify the effect of a lower second-stage homogenization temperature leading to insufficient refinement of the Al6Mn and Al(FeMn)Si dispersed phases and an increased submicron to micron-sized precipitates in the second network.

[0088] Performance testing: Experiment 1: Room temperature tensile property test. The test subjects were extruded profiles from Examples 1-4 and Comparative Examples 1-12. The purpose was to obtain yield strength, tensile strength, and elongation after fracture to verify the mechanical property range of claim 4. The principle is based on the static uniaxial tensile stress-strain relationship. The method was carried out according to GB / T 228.1-2010, using standard plate specimens, room temperature 20±2℃, and strain rate controlled at 2×10⁻³ s⁻¹. Key parameters included specimen cross-sectional dimensions, gauge length, loading rate, and centering control. Data processing involved averaging three parallel tests to calculate Rp0.2, Rm, and A%, and statistically analyzing the standard deviation for use in the performance summary table in Module 9 and the single-factor analysis in Module 10.

[0089] Experiment 2: Three-point bending energy absorption test. The test subjects were Examples 1-4 and some representative comparative examples. The purpose was to evaluate the bending energy absorption capacity and maximum bending displacement under simulated battery tray impact conditions. The principle was to obtain the energy absorption per unit volume by integrating the load-displacement curve of a simply supported beam at three points. The method followed GB / T 14452 and combined with the internal control specifications of automotive manufacturers. The span was 80mm, the diameter of the loading roller and support roller was 10mm, and the loading rate was 5mm / min. The maximum load, corresponding displacement, and the entire curve were recorded. Data processing was performed to obtain the energy absorption per unit volume (J·cm⁻³) through numerical integration. The average value and standard deviation were calculated and normalized to the 6061-T6 comparative profile to obtain the relative improvement percentage for the additional effect argument of the claims.

[0090] Experiment 3: Symmetrical high-cycle fatigue test under tension and compression. The test subjects were Examples 1-4 and key comparative examples (including samples with excessive composition and process deviations). The purpose was to verify the 10 5 ~10 6 The study measures the improvement in fatigue life within a given cycle range and differentiates between dual-network, single-network, and no-network conditions. The principle utilizes high-cycle fatigue SN curves under stress control, with a load ratio R=-1. The method follows GB / T 3075 or ASTM E466, using circular or flat fatigue specimens at a frequency of 60–80 Hz, tested at room temperature in air. Parameters include nominal stress amplitude and an upper limit of 10 cycles. 7The failure criterion is specimen fracture or stiffness reduction >25%. Data processing involves fitting the SN curve to logarithmic coordinates, extracting the lifetime Nf at a specific stress level, and calculating the improvement ratio relative to 6061-T6 and compared to 6xxx series alloys.

[0091] Experiment 4: Microscopic characterization of the dual-network precipitated structure. The test subjects were representative samples from Examples 1-4, typical comparative examples, and single-factor experiments. The aim was to directly observe and quantify the size, volume fraction, and aspect ratio of the first-network nano-precipitated phase and the second-network submicron precipitated phase, verifying the microstructure definition of claims 1-3. The principle utilized a combination of TEM, HAADF-STEM, EBSD, and image analysis statistics. Method: Thin foil samples were prepared by electrolytic double-spraying and observed under a 200kV TEM. The sizes of >500 particles were statistically analyzed. EBSD was used to determine the recrystallization volume fraction and grain size. Data were output as CSV, including particle size distribution and volume fraction, and correlation analysis with mechanical properties was performed.

[0092] Experiment 5: Straightness and Residual Stress Testing of Extruded Profiles. The test subjects were Examples 1-4 and comparative examples with process deviations (such as samples with altered extrusion temperature and cooling rate). The aim was to evaluate the profile straightness control capability and residual stress level under high extrusion ratio conditions, linking them to battery tray assembly accuracy and service stability. The principle involved using a coordinate measuring machine (CMM) to measure the profile axial deviation and X-ray diffraction to measure surface residual stress. Method: For profiles with an extrusion ratio of 10-18 and a length ≥2m, maximum bending deflection and straightness were measured at various points at room temperature; XRD was used to measure axial residual stress at multiple locations. Data processing included calculating bending deflection per unit length, uniformity of residual stress distribution, and peak value, and comparing the differences between the examples and comparative examples.

[0093] Experiment 6: Thermal conductivity and thermal uniformity testing. The test subjects were Examples 1-4 and a selected comparative example. The aim was to verify the thermal conductivity performance while still meeting the thermal management requirements of the battery tray under multi-element microalloying conditions. The principle involved measuring the thermal diffusivity using laser scintillation, and then calculating the thermal conductivity based on density and specific heat. Simultaneously, thermal imaging was used to assess the temperature rise uniformity. Method: Φ10×2mm circular samples were prepared according to ASTM E1461. The thermal diffusivity was measured at 25℃ and 80℃, and the steady-state temperature rise field was recorded. Data processing: The thermal conductivity λ and temperature field uniformity index (maximum temperature difference ΔT) were calculated and compared with 6061-T6 to determine the relative retention of the thermal conductivity performance of the invention under high-strength conditions.

[0094] Figure 1To investigate the effect of Si content on yield strength and elongation after fracture, the following parameters were fixed: Mg 0.81wt%, Mn 0.62wt%, Fe 0.12wt%, Cu 0.10wt%, Sc 0.075wt%, Zr 0.075wt%, Er 0.04wt%, Ti 0.028wt%, and B 0.010wt%. The casting and two-stage homogenization processes were performed at 478℃ for 9 h followed by 515℃ for 4.5 h. The extrusion exit temperature was 540℃, the online quenching cooling rate was 25℃·s⁻¹, and the two-stage artificial aging process was performed at 158℃ for 4 h followed by 185℃ for 4.5 h. The Si content was varied from 0.75wt% to 0.95wt%. When Si content is in the range of 0.78–0.90 wt%, the yield strength increases from 295 MPa to 312 MPa while the elongation remains in the range of 13.8–15.0%, showing a coordinated improvement in strength and plasticity. When Si content is below 0.78 wt%, the strength drops significantly to about 282 MPa, and although the elongation is relatively high, the overall load-bearing capacity is insufficient. When Si content is above 0.90 wt%, the strength no longer increases significantly and the elongation drops to about 12.0%, resulting in a loss of toughness. This indicates that an appropriate intermediate Si content can form a better balance between precipitation strengthening and matrix toughness.

[0095] Figure 2 To investigate the effect of the volume fraction of the first network nano-precipitates on yield strength and elongation after fracture, the alloy composition and extrusion-online quenching conditions were fixed as in Example 1, with Mg 0.81wt%, Mn 0.62wt%, Sc 0.075wt%, Zr 0.075wt%, and Er 0.04wt%. The extrusion exit temperature was 540℃ and the cooling rate was 25℃·s⁻¹. By adjusting the two-stage artificial aging regime, the volume fraction of the first network nano-precipitates was controlled between 2.0 and 5.5 vol% without changing the composition and extrusion conditions. When the volume fraction increased from 2.0 vol% to approximately 3.5–4.0 vol%, the yield strength steadily increased from 285 MPa to 305–312 MPa, while the elongation after fracture only gradually decreased from 15.2% to 13.6–14.5%, demonstrating a synergistic region where precipitation strengthening dominates and ductility is well maintained. When the volume fraction was further increased to 5.5 vol%, the yield strength only increased slightly to approximately 314 MPa, and the elongation decreased to 12.5%, showing a significant sacrifice in ductility. When the volume fraction was below 2.5 vol%, the strength was insufficient. This proves that there is a performance peak range of about 3.5–4.0 vol% for the first network nanoprecipitated phase. Within this range, both strength improvement and ductility maintenance can be taken into account, thereby supporting the synergistic optimization of the overall structural load-bearing and fatigue performance.

[0096] Figure 3To investigate the effect of the volume fraction of submicron to micron-sized precipitates in the second network on yield strength and elongation after fracture, the main control parameters for alloy composition control, extrusion, and two-stage artificial aging were kept consistent with those in Example 1. The recrystallization volume fraction was maintained at approximately 70–80%, and the volume fraction of nano-precipitates in the first network was stabilized at approximately 3.8 vol%. The variable parameter was the volume fraction of the second network, which ranged from 0.2 vol% to 2.5 vol%. When the volume fraction of the second network increases from 0.2 vol% to approximately 1.0–1.5 vol%, the yield strength increases from 292 MPa to approximately 305 MPa while the elongation remains around 14.5–15.0%, indicating that an appropriate amount of the second network phase helps to provide additional particle reinforcement and crack propagation passivation. When the volume fraction increases to 2.0 vol%, the strength gain tends to saturate while the elongation has significantly decreased to around 13.8%. When it continues to increase to 2.5 vol%, the plasticity further decreases to approximately 13.0%, and the potentially interconnected brittle network increases the cracking sensitivity. Conversely, when the volume fraction is below 0.5 vol%, the insufficient dispersed phase leads to a reduction in both strength and fatigue life. The above trends indicate that the submicron to micron-sized precipitates of the second network can achieve a relatively reasonable ratio between reinforcement, damping, and crack passivation in the range of approximately 1.0–1.5 vol%, thereby forming a complementary and synergistic dual-network structure with the nano-precipitates of the first network.

[0097] Figure 4 XPS investigation of the first network nano-precipitated phase region in Example 1 of this invention, with fixed parameters including an alloy matrix composition of Al-Mg-Si-Cu-Mn-Sc-Zr-Er system, a uniform aging regime of medium-temperature peak aging, sample surfaces subjected to the same mechanical polishing and argon ion light etching pretreatment, and a test vacuum better than 5×10⁻⁻⁻⁴. 7 The mbar, incident X-ray power, and analyzer power were kept constant. The parameters were varied by selecting the fine first network nano-precipitate enrichment region within the crystal as the analysis area. Spectra were constructed by superimposing the peak intensities of Al 2p, Mg 2p, Si 2p, Cu 2p, Sc 2p, Zr 3d, and Er 4d corresponding to precipitates such as β″ phase, Q′ phase, and L12-Al3(Sc,Zr,Er). The results showed that the Mg 2p and Si 2p peaks were significantly enhanced in the first network region, and the intensities of Sc, Zr, and Er related peaks were increased. Cu 2p remained at a moderate level, while the Fe and Mn related peaks were weak. This indicates that this region is the main enrichment area for Mg, Si, and rare elements, and is rich in nano-L12 and β″ / Q′ reinforcing phases. From an energy dispersive spectroscopy perspective, this supports the first network as the key structural unit providing the main precipitation reinforcement.

[0098] Figure 5 XPS survey spectrum of the second network submicron–micron precipitated phase region in Embodiment 1 of the present invention, with fixed parameters and Figure 4The analysis was identical in all aspects, including the overall alloy composition, aging process, surface pretreatment, and testing conditions. The only change was that the analytical region was shifted to the area where coarse precipitates of the second network, such as grain boundaries and subgrain boundaries, were concentrated. Spectra were constructed by overlaying peaks from Al6Mn, Al(FeMn)Si, and some coarsened L12 particles, contributing Al 2p, Si 2p, Mn 2p, Fe 2p, Zr 3d, and Er 4d. The results showed that, compared to the first network, the Mn 2p and Fe 2p peak intensities were significantly increased in the second network region, the Si 2p peak remained high, while the Mg 2p and Cu 2p signals were relatively weakened. The Zr and Er peaks changed from high to medium levels. This indicates that this region is dominated by stable eutectic or impurity phases such as Al6Mn and Al(FeMn)Si, accompanied by some coarsened L12 particles. Their main function is to stabilize grain boundaries and pin subgrains, rather than to undertake the main precipitation strengthening function. In terms of compositional distribution, this complements the first network, which is beneficial for obtaining a stable microstructure.

[0099] Figure 6 The XRD pattern of the double-network precipitated microstructure of aluminum alloy profiles for battery tray extrusion is shown. The fixed parameters are: alloy system composition Al–Si–Mg–Mn–Sc–Zr–Er–Ti–B; test conditions: Cu Kα radiation, wavelength λ≈1.5406 Å, scan range 20°–90°, step size approximately 0.1°, and θ–2θ symmetrical scanning mode. The matrix is ​​an α-Al solid solution obtained through extrusion and two-stage artificial aging, synergistically reinforced by the first and second network nano-precipitates. The varying parameters are the slight fluctuations in the volume fraction and morphology of the precipitates under the fine-tuning of the two-stage aging regime. These are reflected in the figure as subtle differences in the intensity and full width at half maximum (FWHM) of the main diffraction peaks (Al{111}, {200}, {220}, and {311}, as well as the β″ / Q′ phase, the dispersed Al6Mn / Al(FeMn)Si phase, and the L12 type Al3(Sc) phase. The intensity variations of weak peaks (Zr, Er) in the ranges of 27°–35° and 40°–70° were observed. The results showed that the main peak of the α-Al matrix remained narrow and sharp, with no new phase or abnormal peaks of brittle phases appearing. At the same time, the fine L12 nanophase of the second network moderately increased the overall diffuse peak background and the intensity of some secondary peaks without significantly introducing coarse peaks. This indicates that the microstructure under this aging regime is dominated by fine and diffuse shearable / non-shearable nanoprecipitates, without obvious aggregation of coarse equilibrium phases. This ensures both matrix continuity and enhances dislocation pinning ability, providing diffraction evidence for the synergistic effect of subsequent yield strength improvement and good plasticity.

[0100] like Figure 7The microstructure shown clearly demonstrates the dual-network precipitate structure formed in Example 1 of this invention. This structure is composed of two layers of precipitate phase networks working together: the first network consists of nanoscale precipitates distributed within the grain boundaries and subgrain boundary regions, mainly including β″ phase, Q′ phase, and nano-L12 phase. These ultrafine precipitates are uniformly dispersed to form a dense reinforcing network; the second network consists of submicron to micron-scale precipitates distributed within grain boundaries, subgrain boundaries, and some intragranular substructure regions, including Al6Mn phase, Al(FeMn)Si phase, and coarsened L12 phase. These coarser precipitates form a continuous or semi-continuous network distribution along specific regions such as grain boundaries. The two networks are spatially intertwined and micro / nano-composite in scale, jointly constructing... A unique dual-scale strengthening system. The nanoscale first network precipitate provides a high density of dislocation pinning points within the matrix, while the submicron to micron-scale second network precipitate effectively pins grain boundaries and hinders crack propagation. This dual-network synergistic mechanism enables the material to achieve a yield strength of 305 MPa while maintaining good ductility of 14.5%, verifying the effectiveness of the technical route of this invention, which successfully constructs a dual-network precipitate structure through precise composition design (Sc, Zr, Er microalloying combined with a Si-Mg-Cu basic strengthening system) and a two-stage homogenization-extrusion-double-stage aging process.

[0101] As shown in Table 1, Examples 1-4 all meet the requirements of claim 4 for yield strength of 290-320 MPa, tensile strength of 320-360 MPa, and elongation after fracture of 13-16%. Examples 2 and 4 are close to the upper limit of the strength range, while Example 3 shows the best performance in terms of elongation and three-point bending energy absorption, demonstrating the advantage of the dual-network precipitation structure in terms of adjustable strength and toughness. Comparative Examples 1-6 show that when Si or Mg deviates from the optimal range (insufficient / excessive Si, Mg, Fe, Sc / Zr / Er or B), both strength and fatigue life decrease significantly, or an imbalance occurs where the strength is too high but the plasticity and energy absorption deteriorate. High Fe content and insufficient Sc / Zr / Er content significantly reduce fatigue life. The process deviations in Comparative Examples 7-12 (low extrusion exit temperature, insufficient quenching cooling rate, cancellation of pre-aging, or aging / homogenization temperature deviating from the window) generally led to a simultaneous decrease in yield strength, flexural energy absorption, and fatigue life. Among these, insufficient online quenching rate and low second-stage homogenization temperature had a particularly significant impact on fatigue performance. A comprehensive weighted evaluation of the five performance indicators showed that Examples 1-4 were generally superior to all comparative examples in terms of strength, plasticity, flexural energy absorption, and fatigue life, demonstrating that the composition range, dual-network microstructure parameters, and extrusion-online quenching-double-stage aging process window defined in the claims have significant technical effects.

[0102] Table 1 Summary of Performance of Examples and Comparisons

[0103] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that any equivalent structural transformations made under the concept of the present invention and using the contents of the specification and drawings of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. An aluminum alloy profile for extruding battery trays, characterized in that, Its chemical composition, by mass percentage, includes: Si 0.78–0.92 wt%, Mg 0.72–0.90 wt%, Mn 0.55–0.70 wt%, Fe 0.10–0.15 wt%, Cu 0.05–0.15 wt%, Sc 0.05–0.10 wt%, Zr 0.05–0.10 wt%, Er 0.02–0.06 wt%, Ti 0.015–0.04 wt%, B 0.001–0.02 wt%, with the balance being Al and unavoidable impurities. The content of any single element in the unavoidable impurities is not greater than 0.03 wt%, and the total content of the unavoidable impurities is not greater than 0.10 wt%. The aluminum alloy profile for extruding the battery tray, after extrusion and aging treatment, exhibits a double-network precipitate structure in its microstructure. The double-network precipitate structure includes: The recrystallization volume fraction is 60–95%, and the equivalent diameter of the recrystallized grains is 5–18 μm; A first network nanoprecipitate distributed within the grain and subgrain boundary regions, the first network nanoprecipitate being selected from one or more of β″ phase, Q′ phase, and nanoscale L12 structure precipitates, the first network nanoprecipitate having an equivalent diameter of 5–20 nm and a volume fraction of 2.5–5.0 vol%. The second network of submicron to micron-sized precipitates is distributed in grain boundaries, subgrain boundaries, and some intragranular substructure regions. The second network of submicron to micron-sized precipitates includes one or more of Al6Mn phase, Al(FeMn)Si phase, and submicron to micron-sized coarsened L12 structure precipitates. The average particle size of the second network of submicron to micron-sized precipitates is 0.2 to 1.0 μm, and the volume fraction is 0.5 to 2.0 vol.

2. The aluminum alloy profile for extruding battery trays as described in claim 1, characterized in that, The equivalent diameter of the first network nano-precipitated phase is 8–15 nm, the average particle size of the second network submicron to micron-scale precipitated phase is 0.3–0.8 μm, and the volume fraction of the second network submicron to micron-scale precipitated phase is 0.8–1.5 vol.

3. The aluminum alloy profile for extruding battery trays as described in claim 1, characterized in that, The aluminum alloy profile for extruding the battery tray is formed by two-stage homogenization heat treatment of aluminum alloy ingots to create Al-derived double-network precipitate intermediate ID, which is then obtained by extrusion forming and two-stage artificial aging. The Al-derived double-network precipitate intermediate ID has the following microstructure characteristics: After homogenization, the intragranular and subgrain boundary regions contain one or more of the following: solute atom clusters with an equivalent diameter of 5–15 nm and a volume fraction of 1–3 vol%. The solute atom clusters evolve into the β″ and Q′ phases in the first network nano-precipitates of claim 1 during subsequent extrusion and aging. The L12 fine precipitates partially grow and coarsen during subsequent extrusion and aging, forming the coarsened L12 structure precipitates in the second network submicron to micron-scale precipitates of claim 1. The grain boundaries and interdendritic regions contain Al6Mn and Al(FeMn)Si phases with an average grain size of 0.2–0.8 μm and a volume fraction of 0.5–2.0 vol%.

4. The aluminum alloy profile for extruding battery trays as described in claim 1, characterized in that, After extrusion and aging treatment, the aluminum alloy profile for extruding battery trays has a yield strength of 290-320 MPa, a tensile strength of 320-360 MPa, and an elongation after fracture of 13-16% at room temperature.

5. A processing method for preparing the aluminum alloy profile for extruding battery trays as described in any one of claims 1-4, characterized in that, Includes the following steps: S1. Melting and Alloying: High-purity aluminum ingots are added to a melting furnace and heated to melt. Silicon metal, a magnesium-containing aluminum-based master alloy, a manganese-containing aluminum-based master alloy, and a copper-containing aluminum-based master alloy are added sequentially. Then, aluminum-manganese-zirconium-titanium-boron microalloying master alloy B1, a scandium-containing aluminum-based master alloy, an erbium-containing aluminum-based master alloy, and a zirconium-containing aluminum-based master alloy are added to the melt. The melt is stirred, and the sample composition is tested to ensure that the contents of Mn, Sc, Zr, and Er in the melt meet the following requirements: Mn 0.55–0.70 wt%, Sc 0.05–0.10 wt%, Zr 0.05–0.10 wt%, and Er 0.0 wt%. 2 to 0.06 wt%; and by selecting raw materials of appropriate purity grade to control the Fe content within the range of 0.10 to 0.15 wt%; and by adjusting the amount of silicon metal, magnesium-containing aluminum-based master alloy, copper-containing aluminum-based master alloy and aluminum-manganese-zirconium-titanium-boron microalloy master alloy B1, so that the contents of Si, Mg, Cu, Ti and B in the melt, together with Mn, Fe, Sc, Zr and Er, all meet the range defined in claim 1, wherein the Zr element is adjusted by aluminum-manganese-zirconium-titanium-boron microalloy master alloy B1 and zirconium-containing aluminum-based master alloy to meet the range of 0.05 to 0.10 wt%; S2, Refining, Degassing and Filtration: The alloy melt obtained in step S1 is refined and degassed, and then filtered to obtain a purified alloy melt. S3. Casting and two-stage homogenization: The purified alloy melt obtained in step S2 is semi-continuously cast to obtain an aluminum alloy ingot; the aluminum alloy ingot is subjected to two-stage homogenization treatment at a first-stage temperature and a second-stage temperature higher than the first-stage temperature, and then cooled to room temperature to obtain Al-derived double-network precipitation intermediate ID. S4. Extrusion and online quenching: The Al-derived double network precipitate intermediate ID obtained in step S3 is sawn into extrusion billets. The extrusion billets are heated and then hot extruded through an extruder to form a hot extrusion, so that the extrusion outlet temperature is controlled at 530-550℃ to ensure that the alloying elements are basically dissolved. The hot-extruded profile is quenched online at the extrusion exit, and the profile is cooled from the extrusion exit temperature to below 60°C at a cooling rate of not less than 20°C / s to obtain a quenched profile. S5. Stretch straightening and two-stage artificial aging: The quenched profile obtained in step S4 is subjected to stretch straightening treatment, followed by two-stage artificial aging treatment at a first aging temperature and a second aging temperature higher than the first aging temperature, and then cooled to room temperature to form a double network precipitation structure, finally obtaining an aluminum alloy profile for battery tray extrusion.

6. The processing technology for preparing aluminum alloy profiles for battery tray extrusion as described in claim 5, characterized in that, The chemical composition of the aluminum-manganese-zirconium-titanium-boron microalloy master alloy B1 used to prepare the aluminum alloy profile for extruding the battery tray, by mass percentage, includes: Mn 8-12wt%, Zr 3-6wt%, Ti 3-8wt%, B 0.5-2.0wt%, with the balance being Al and unavoidable impurities.

7. The processing technology for preparing aluminum alloy profiles for battery tray extrusion as described in claim 5, characterized in that, In step S1, the high-purity aluminum ingot is heated to 730–760°C to completely melt it. Silicon metal, magnesium-containing aluminum-based master alloy, manganese-containing aluminum-based master alloy, and copper-containing aluminum-based master alloy are added sequentially. The melt temperature is then adjusted to 730–760°C and held for 10–20 minutes. Then, aluminum-manganese-zirconium-titanium-boron microalloy master alloy B1, scandium-containing aluminum-based master alloy, erbium-containing aluminum-based master alloy, and zirconium-containing aluminum-based master alloy are added to the melt. The mixture is stirred for 10–20 minutes to ensure uniform composition. The contents of Si, Mg, Cu, Mn, Fe, Sc, Zr, Er, Ti, and B in the melt are controlled by online spectral analysis to meet the ranges defined in claim 1.

8. The processing technology for preparing aluminum alloy profiles for battery tray extrusion as described in claim 5, characterized in that, In step S2, high-purity argon or high-purity nitrogen is introduced into the alloy melt for online rotor degassing for 8-20 minutes. A refining flux for aluminum alloy melt, composed of sodium chloride and potassium chloride, is added to the surface and interior of the melt. The mass ratio of sodium chloride to potassium chloride is 40:60 to 60:

40. The amount of the refining flux added is 0.1-0.5 wt% of the total alloy mass. After standing for 5-15 minutes, the melt is filtered through a ceramic filter plate to obtain purified alloy melt.

9. The processing technology for preparing aluminum alloy profiles for battery tray extrusion as described in claim 5, characterized in that, In step S3, the purified alloy melt is semi-continuously cast at a pouring temperature of 710-740℃ to obtain an aluminum alloy ingot with a diameter of 200-600mm. The two-stage homogenization process involves holding the aluminum alloy ingot at a temperature of 470–485°C for 6–12 hours in the first stage, then holding it at a temperature of 510–520°C for 3–6 hours in the second stage, followed by air cooling or furnace cooling to room temperature at a cooling rate of 20–40°C / h to obtain the Al-derived double-network precipitation intermediate ID.

10. The processing technology for preparing aluminum alloy profiles for battery tray extrusion as described in claim 5, characterized in that, In step S4, the Al-derived double-network precipitated intermediate ID is sawn into an extrusion billet, the extrusion billet is heated to 480-495°C and held for 2-3 hours, the extrusion die is preheated to 460-480°C, and the extrusion is extruded into a profile through a horizontal extruder at an extrusion ratio of 10-18 and an extrusion speed of 1.0-2.5 m / min, with the extrusion outlet temperature controlled at 530-550°C. The online quenching process involves sending the hot-extruded profile into a water spray cooling zone or a water mist cooling zone within 3 seconds after demolding, and cooling the profile from 530-550℃ to below 60℃ within 10-20 seconds at a cooling rate of not less than 20℃ / s. In step S5, the quenched profile is subjected to a tensile deformation of 1-3% for straightening; then, a two-stage artificial aging process is performed: first, it is held at a first aging temperature of 150-165℃ for 3-5 hours, then held at a second aging temperature of 180-190℃ for 3-6 hours, and then cooled to room temperature.

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