A high-toughness rare earth aluminum alloy and a room temperature-deep cold two-stage deformation heat treatment preparation method thereof

Abstract

The application relates to a high-toughness rare earth aluminum alloy and a room temperature-low temperature two-stage deformation heat treatment preparation method thereof, and relates to the technical field of metal material processing. The aluminum alloy belongs to an Al-Cu-Mg system aluminum alloy and contains a proper amount of a rare earth element yttrium. The preparation method comprises the following steps: after ingredient allocation and smelting, the aluminum alloy is cast into a cast blank; room temperature rolling deformation is carried out; then solid solution treatment and quenching are carried out; deep cold rolling deformation is carried out; and finally, aging treatment is carried out, so that the high-toughness rare earth aluminum alloy is obtained. Through the synergistic effect of the thermal mechanical processing technology composed of rare earth yttrium micro-alloying, room temperature rolling, solid solution treatment, deep cold rolling and aging treatment, the fine-grain strengthening, deformation strengthening and precipitation strengthening mechanisms are fully utilized, so that the rare earth aluminum alloy simultaneously has high strength and good plasticity, and is suitable for the fields of aerospace, rail transportation and automobile lightening.

Description

Technical Field

[0001] This invention belongs to the field of metal material processing technology, specifically relating to a high-strength and high-toughness rare earth aluminum alloy and its preparation method. Background Technology

[0002] High-strength and high-toughness aluminum alloys hold an irreplaceable position in high-end manufacturing fields such as aerospace, rail transportation, and automotive lightweighting due to their excellent specific strength, good machinability, and corrosion resistance. With the continuous improvement of the comprehensive performance requirements of structural materials in modern industry, developing aluminum alloy materials that combine high strength and high ductility is a core technical challenge that urgently needs to be solved in this field. Al-Cu-Mg alloys are typical heat-treatable strengthening alloys, and their strengthening mechanism mainly relies on the effective obstruction of dislocation movement caused by nanoscale coherent or semi-coherent precipitates formed during aging. However, under traditional processes, these alloys generally suffer from a contradiction between strength and ductility. Aging treatment often induces coarsening of precipitates or their transformation into incoherent equilibrium phases. This evolution weakens the strengthening effect while severely damaging ductility. Traditional casting and hot working cannot achieve sufficient grain refinement and homogenization, and coarse as-cast structures and brittle second phases distributed along grain boundaries constitute another important source of ductile damage. Optimizing the microstructure while controlling precipitation behavior is key to achieving a synergistic improvement in the strength and ductility of these alloys.

[0003] Rare earth microalloying is an effective way to improve the overall performance of aluminum alloys. Trace amounts of rare earth elements can purify the matrix, refine grains, regulate the morphology and distribution of precipitated phases, and form dispersed phases with high thermal stability, thereby improving the mechanical properties and thermal stability of the alloy. Among them, yttrium (Y) can significantly refine the as-cast structure, inhibit recrystallization, and optimize the precipitation sequence, but its application in aluminum alloys is still insufficient. In particular, there are few reports on technical solutions that combine Y microalloying with specific large deformation processes to achieve synergistic optimization of strength and plasticity. In terms of plastic processing, traditional room temperature rolling can introduce high-density dislocations to achieve deformation strengthening, but excessive deformation can easily lead to cracking of the sheet, and the deformed structure is prone to recovery and recrystallization in subsequent solution treatment, partially offsetting the strengthening effect. Cryogenic rolling can promote the accumulation of dislocations, form finer deformation substructures, and promote the fragmentation and dispersion of the second phase by inhibiting dynamic recovery. However, cryogenic rolling alone is difficult to achieve both plasticity and plasticity, and its matching with subsequent heat treatment regimes needs further investigation.

[0004] Current technologies for preparing high-strength Al-Cu-Mg aluminum alloys generally face the bottleneck of a strength-plasticity inversion. The potential of rare-earth Y microalloying has not been fully explored, and research on the composite deformation process of room temperature pre-deformation and deep cryogenic rolling, and its systematic matching with the solution aging regime, still needs to be deepened. Developing a technical solution that can synergistically utilize multiple mechanisms of grain refinement strengthening, deformation strengthening, and precipitation strengthening is of significant scientific importance and engineering application value for obtaining aluminum alloy materials with both high strength and high plasticity. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing Al-Cu-Mg aluminum alloys, which are difficult to balance strength and plasticity and have insufficient comprehensive mechanical properties due to the single preparation process, and to provide a high-strength and high-toughness rare earth aluminum alloy and its preparation method of room temperature-cryogenic two-stage deformation heat treatment.

[0006] The present invention discloses a high-strength and high-toughness rare-earth aluminum alloy, wherein the high-strength and high-toughness rare-earth aluminum alloy is composed of Cu 3.5% to 4.5%, Mg 0.5% to 1.5%, Ti 0.1% to 0.2%, Y 0.1% to 0.3%, and the balance being Al and unavoidable impurities by mass fraction.

[0007] Furthermore, the high-strength and high-toughness rare-earth aluminum alloy is composed of Cu 3.8~4.2%, Mg 0.8~1.2%, Ti 0.13~0.18%, Y 0.15~0.25%, with the balance being Al and unavoidable impurities, by mass fraction.

[0008] Furthermore, the high-strength and high-toughness rare-earth aluminum alloy is composed of Cu 4.0%, Mg 1.0%, Ti 0.15%, Y 0.2% by mass fraction, with the balance being Al and unavoidable impurities.

[0009] Furthermore, the high-strength and high-toughness rare earth aluminum alloy has a hardness ≥160HV, tensile strength ≥600MPa, yield strength ≥410MPa, and elongation after fracture ≥10%.

[0010] The method for preparing the high-strength and high-toughness rare earth aluminum alloy of the present invention by room temperature-cryogenic dual-stage deformation heat treatment is as follows: (1) Smelting and casting: according to the composition of high-strength and high-toughness rare earth aluminum alloy, after smelting, it is cast into an ingot to obtain a cast aluminum alloy billet; (2) Room temperature rolling: the cast aluminum alloy billet obtained in step (1) is rolled and deformed under room temperature conditions to obtain a room temperature rolled plate; (3) Solution treatment: the room temperature rolled plate obtained in step (2) is heated to the solution temperature and held at that temperature, and then quenched; (4) Cryogenic rolling: the plate quenched in step (3) is rolled and deformed under cryogenic conditions to obtain a cryogenic rolled plate; (5) Aging treatment: the cryogenic rolled plate obtained in step (4) is artificially aged and then water quenched to complete the process.

[0011] Further, the process described in step (1) of preparing high-strength and tough rare earth aluminum alloy components, melting and casting them into ingots to obtain as-cast aluminum alloy billets refers to preparing components by mass fraction, namely Cu 3.5%~4.5%, Mg 0.5%~1.5%, Ti 0.1%~0.2%, Y 0.1%~0.3% and the balance Al, and sequentially adding Al-Cu, Al-Mg, Al-Ti and Al-Y master alloys, stirring, degassing, removing slag, and letting stand after complete melting, and then casting the alloy melt into a metal mold to obtain as-cast aluminum alloy billets.

[0012] Furthermore, in step (2), the deformation amount of room temperature rolling is 30% to 50%.

[0013] Furthermore, in step (3), the solution temperature is 495~505℃ and the heat preservation time is 1~3h.

[0014] Further, in step (4), the cryogenic condition is -196°C; the rolling temperature is -196°C to -150°C, and the deformation is 40% to 60%.

[0015] Furthermore, in step (5), the aging treatment temperature is 165~175℃ and the heat preservation time is 3~8h.

[0016] The method for preparing high-strength and high-toughness rare-earth aluminum alloys provided by this invention organically combines Y element microalloying, room temperature rolling, solution treatment, cryogenic rolling and aging treatment in a specific order and under specific conditions. Significant synergistic effects are generated between the various process steps. The microstructure evolution and performance improvement mechanism far exceed the simple superposition of the individual effects of each step, and achieves simultaneous improvement of strength and plasticity.

[0017] The beneficial effects of the preparation method of the high-strength and high-toughness rare-earth aluminum alloy of the present invention are specifically described below:

[0018] (1) The microalloying of Y element establishes an as-cast microstructure with equiaxed fine grains and low segregation, providing an ideal matrix for subsequent deformation heat treatment: The most significant technical effect of the improved as-cast microstructure in this invention is not simply grain refinement, but rather the formation of a fine α-Al equiaxed grain, high-density dispersed precursor, and low solute segregation as-cast microstructure through the multiple effects of Y element. This microstructure characteristic provides a key fit for the subsequent deformation heat treatment process chain. Fine equiaxed grains improve the processing plasticity of large deformations, dispersed precursors ensure nucleation of precipitation during aging after cryogenic rolling, and low segregation avoids microstructure distortion and performance fluctuations caused by local compositional inhomogeneity. This overall reconstruction of the as-cast microstructure cannot be achieved by process optimization alone without the intervention of Y element.

[0019] (2) Room temperature rolling and solution treatment work together to create a uniform equiaxed matrix and sufficient solid solution preparation: First, the as-cast alloy is rolled at room temperature, utilizing the higher deformation resistance at room temperature to introduce extremely high density of dislocations into the alloy and break up the coarse as-cast structure. This process not only eliminates casting defects, but more importantly, it creates densely distributed subgrain boundaries, deformation bands, and other defect structures within the alloy. These defects become recrystallization nucleation sites during the subsequent solution treatment heating process. While the solution treatment allows the strengthening phases such as Al2Cu and Al2CuMg to fully dissolve to obtain a highly supersaturated solid solution, it also drives the alloy to undergo sufficient recrystallization, generating a uniform equiaxed grain structure. Compared with traditional homogenization annealing or recrystallization solely through solution treatment, this provides the material with excellent deformation coordination capabilities, which is the microstructure basis for all subsequent strengthening and toughening methods to achieve their maximum effect.

[0020] (3) Synergistic effect of uniform equiaxed matrix and cryogenic rolling to achieve the ultimate accumulation of dislocation density and uniform storage of deformation energy: Cryogenic rolling is performed immediately after obtaining the supersaturated solid solution. The extremely low temperature effectively suppresses the thermal activation process required for dynamic recovery, making cross-slip and climb of dislocations extremely difficult, thereby avoiding the annihilation and rearrangement of dislocations during deformation. This allows dislocations to continuously multiply, entangle, and accumulate stably at extremely high density, forming a uniform dislocation cellular structure far exceeding that achievable by room temperature rolling. In addition, the uniform equiaxed matrix grains provide cryogenic rolling with the ability to accommodate higher density geometrically necessary dislocations, allowing deformation energy to be stored in large quantities throughout the material, while avoiding local stress concentration and cracking that are prone to occur during deep deformation, which cannot be achieved by conventional cryogenic rolling or direct rolling of the solid solution state.

[0021] (4) Cryogenic deformation and aging treatment synergistically achieve dispersion and multiple strengthening of precipitates: The high-density dislocations and accompanying vacancy defects accumulated by cryogenic rolling provide non-uniform nucleation sites for the S phase (Al2CuMg) and θ′ phase (Al2Cu). This allows the strengthening phase to nucleate and precipitate in a fine, dispersed form within the grains and along dislocation lines, forming nano-precipitates. At the same time, the high-density dislocation substructure formed by cryogenic rolling undergoes limited static recovery during aging heating, and some dislocations rearrange into stable low-energy dislocation walls and subgrain boundaries. These substructures are pinned by the simultaneously precipitated dispersed strengthening phase, avoiding softening due to recovery or recrystallization. Thus, the three mechanisms of fine grain strengthening, high-density dislocation substructure strengthening, and ultra-dispersed precipitation strengthening work synergistically in the final microstructure.

[0022] This synergistic process establishes a novel process chain encompassing Y-element microalloying, room temperature pre-deformation, solution treatment, cryogenic deformation, and aging. While individual mechanisms (such as deformation refinement, cryogenic recovery suppression, and aging precipitation) are known in existing reports in this field, the common practice is to directly cryogenically roll after solution treatment or roll at room temperature followed by aging. These conventional routes generally face a dilemma: if the initial grains are coarse, the energy storage introduced by cryogenic deformation is unevenly distributed, and localized high-energy regions during aging can easily trigger recrystallization and softening, leading to a strength-toughness inversion; if only room temperature rolling is used, the introduced defect density is insufficient to drive extreme dispersed precipitation, and the deformed microstructure is difficult to retain effectively. This invention overcomes the strength-toughness inversion in high-strength aluminum alloys by deeply coupling specific processes, simultaneously activating and positively synergistically strengthening and toughening mechanisms of grain refinement, substructure, and dispersed precipitation.

[0023] By introducing 0.1-0.3% Y by mass, the as-cast microstructure of the aluminum alloy was significantly improved. Simultaneously, a thermomechanical treatment process involving room temperature rolling, solution treatment, cryogenic rolling, and aging was employed. Room temperature rolling (30-50% deformation) introduced high dislocation density and broke up the as-cast microstructure, providing nucleation sites for subsequent recrystallization; solution treatment (500±5℃, 1-3h) ensured the full dissolution of the strengthening phase and promoted recrystallization refinement; cryogenic rolling (-196℃ to -150℃, 40-60% deformation) effectively suppressed dynamic recovery, accumulating high-density dislocations and deformation energy storage; finally, aging treatment (170±5℃, 3-8h) precipitated dispersed S and θ′ strengthening phases. These synergistic effects fully utilized grain refinement strengthening, deformation strengthening, precipitation strengthening, and dislocation-precipitate interaction, giving the alloy both high strength and good plasticity, breaking through the traditional high strength and high toughness of Al-Cu-Mg aluminum alloys. The prepared aluminum alloy has a uniform and fine grain structure, strong process compatibility, and controllable cost, and has broad application prospects in aerospace, rail transportation, automotive lightweighting and other fields. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below.

[0025] Figure 1 This is a process flow diagram for preparing the high-strength and high-toughness rare-earth aluminum alloy of the present invention.

[0026] Figure 2 The images show a comparison of the as-cast microstructures of the Y-microalloyed aluminum alloy prepared in Example 1 of this invention and the alloy without added Y; wherein, (a) is the microstructure of the aluminum alloy with 0.25wt% Y added, and (b) is the microstructure of the aluminum alloy without added Y.

[0027] Figure 3The images show the optical microstructure of the as-cast alloy prepared in Example 2 of this invention after only room temperature rolling / solution; wherein, (a) is the microstructure of the aluminum alloy with 0.2wt% Y added, and (b) is the microstructure of the aluminum alloy without Y added.

[0028] Figure 4 The figures are optical microstructures of the high-strength and high-toughness rare-earth aluminum alloys prepared in Examples 2 and 3 of the present invention; wherein, (a) is an optical microstructure of the high-strength and high-toughness rare-earth aluminum alloy prepared in Example 2; and (b) is an optical microstructure of the high-strength and high-toughness rare-earth aluminum alloy prepared in Example 3.

[0029] Figure 5 This is a scanning electron microscope image of the microstructure of the high-strength and high-toughness rare-earth aluminum alloy prepared in Example 3 of the present invention.

[0030] Figure 6 The images shown are scanning electron microscope (SEM) images of the microstructure of the high-strength and high-toughness rare-earth aluminum alloy prepared in Example 4 of this invention and their corresponding elemental surface distribution diagrams. Among them, (a) is a scanning electron microscope image of the microstructure of the high-strength and high-toughness rare-earth aluminum alloy, (b) is an Al elemental surface distribution diagram, (c) is a Cu elemental surface distribution diagram, (d) is a Mg elemental surface distribution diagram, (e) is a Ti elemental surface distribution diagram, and (f) is a Y elemental surface distribution diagram.

[0031] Figure 7 This is a transmission electron microscope (TEM) image of the aged precipitates in the high-strength and high-toughness rare-earth aluminum alloy prepared in Example 4 of the present invention.

[0032] Figure 8 The figures show a comparison of room temperature tensile stress-strain curves of aluminum alloys with the same composition as those in Example 4 of this invention, prepared using different methods. In the figures, the red curve corresponds to the room temperature tensile stress-strain curve of the aluminum alloy prepared by the method in Example 4, which underwent room temperature-cryogenic double-stage deformation heat treatment. The green curve corresponds to the room temperature tensile stress-strain curve of the aluminum alloy prepared only by the cold rolling-solution-aging method. The blue curve corresponds to the room temperature tensile stress-strain curve of the aluminum alloy prepared by the method in Example 1. The black curve corresponds to the room temperature tensile stress-strain curve of the aluminum alloy prepared only by the smelting method. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0034] This invention provides a high-strength and high-toughness rare-earth aluminum alloy and its preparation method using a room-temperature-cryogenic dual-stage deformation heat treatment. The preparation flow chart is shown below. Figure 1 As shown, the main alloying elements in this aluminum alloy, by mass fraction, are: Cu 3.5%–4.5%, Mg 0.5%–1.5%, Ti 0.1%–0.2%, Y 0.1%–0.3%, with the balance being Al and unavoidable impurities. Its preparation method includes the following steps:

[0035] S1. Smelting and Casting:

[0036] The alloy is prepared according to the Al-Cu-Mg-Ti composition (Cu 3.5%–4.5%, Mg 0.5%–1.5%, Ti 0.1%–0.2%), and Y (added as an Al-Y master alloy) is added at 0.1–0.3% of the total mass of the final alloy. Industrial pure aluminum ingots are heated to 720–760℃ and melted. Al-(30–50)Cu, Al-(30–50)Mg, Al-(5–10)Ti, and Al-(5–10)Y master alloys are added sequentially. After complete melting, the mixture is stirred, degassed, and slag is removed. It is then allowed to stand for 15–30 minutes. The molten alloy is poured into a metal mold to obtain a cast billet.

[0037] Using the above-mentioned rare earth Y content ratio (0.1-0.3wt%) can effectively refine the as-cast grains, purify grain boundaries, and produce a synergistic strengthening effect with subsequent thermomechanical treatment. If the Y content is less than 0.1wt%, the microalloying effect is not significant, and the grain refinement strengthening effect is weak; if the Y content is greater than 0.3wt%, coarse rare earth compounds are easily formed, which will impair the plasticity and processing performance of the alloy.

[0038] S2, Room temperature rolling:

[0039] The as-cast billet obtained in step S1 is rolled at room temperature, with the total deformation controlled at 30-50%. This stage aims to introduce a large number of dislocations and deformation energy through room temperature cold rolling, providing high-density recrystallization nucleation sites for subsequent solution treatment and providing heterogeneous nucleation sites for precipitates.

[0040] This invention employs room temperature rolling instead of direct high-temperature rolling because room temperature deformation effectively accumulates deformation energy, avoiding the decrease in dislocation density caused by dynamic recovery. If the room temperature rolling deformation is less than 30%, the introduced dislocation density is insufficient, resulting in coarse recrystallized grains and weakened precipitation strengthening effect. If the deformation exceeds 50%, cracks are prone to occur at the billet edges, and excessive energy storage may lead to abnormal grain growth during solid solution treatment. A deformation range of 30-50% can achieve the optimal synergistic effect of fine grains and precipitation while ensuring the integrity of the billet.

[0041] S3. Solution treatment and quenching:

[0042] The billet rolled at room temperature in step S2 is placed in a heat treatment furnace, heated to 500±5℃ and held for 1-3 hours for solution treatment, and then quickly removed for water quenching (water temperature ≤30℃). This step aims to fully dissolve alloying elements such as Cu and Mg into the aluminum matrix to form a supersaturated solid solution, while recrystallization occurs using the energy stored in rolling, refining the grains.

[0043] It should be noted that the solution treatment temperature of 500±5℃ is based on the typical solution treatment temperature range of Al-Cu-Mg-Ti aluminum alloys. If the temperature is too low or the holding time is too short (<1 hour), the alloying elements will not dissolve sufficiently, resulting in insufficient volume fraction of precipitated phases during subsequent aging. If the temperature is too high or the holding time is too long (3 hours), it may cause grain coarsening or even overheating, severely deteriorating the mechanical properties. The optimal holding time window is 1-3 hours, which ensures complete solution treatment while maintaining a fine-grained structure.

[0044] S4, cryogenic rolling:

[0045] The billet quenched in step S3 is then rolled and deformed under cryogenic conditions (-196℃ to -150℃), with the total deformation controlled at 40-60%. The cryogenic environment can be achieved using a liquid nitrogen evaporation device. This step is one of the key features that distinguishes this invention from traditional processes. Deformation under cryogenic conditions can suppress dynamic recovery, significantly increase the dislocation multiplication rate, form a high-density uniform dislocation structure, and simultaneously avoid the localized shear bands common in room temperature deformation, providing more and more uniform nucleation sites for subsequent aging.

[0046] Using the aforementioned cryogenic rolling deformation amount (40-60%) achieves the optimal match between deformation strengthening and precipitation strengthening. If the deformation amount is less than 40%, the dislocation density is insufficient, limiting the aging strengthening effect, and the yield strength is difficult to reach above 410 MPa. If the deformation amount is greater than 60%, the material undergoes excessive work hardening, easily generating microcracks, and may excessively disrupt the homogeneity of the solid solution, leading to a decrease in plasticity. In this embodiment of the invention, -196℃ to -150℃ is preferably used as the cryogenic rolling temperature. At this temperature, the stacking fault energy of the aluminum alloy decreases, and the dislocation slip mode changes to planar slip, which is conducive to the formation of a uniform dislocation cell structure and provides an ideal precipitation substrate for subsequent aging.

[0047] S5. Time-sensitive processing:

[0048] The billet after deep cryogenic rolling in step S4 is placed in an aging furnace at 170±5℃ and held for 3-8 hours, then removed and water-quenched to obtain the high-strength and tough rare-earth aluminum alloy. In this step, the supersaturated solid solution decomposes into fine S phase (Al2CuMg) and θ′ phase. At the same time, the high-density dislocations introduced by deep cryogenic rolling act as rapid diffusion channels, promoting the uniform dispersion of the precipitated phases and achieving significant precipitation strengthening.

[0049] The embodiment of this invention uses an aging temperature of 170±5℃, which is the peak artificial aging temperature for Al-Cu-Mg-Ti aluminum alloys. It is important to emphasize that the control of the aging time is crucial. Two hours corresponds to an under-aged state, which retains high plasticity; eight hours corresponds to an over-aged state, where strength decreases but plasticity slightly increases. Controlling the aging time within 3-8 hours can meet the differentiated strength and plasticity requirements of various application scenarios. If the aging time is less than 2 hours, the volume fraction of precipitated phases is insufficient, resulting in a weak strengthening effect; if it is more than 8 hours, the precipitated phases coarsen, strength decreases, and there is no significant increase in plasticity.

[0050] More preferably, the cryogenic rolling temperature in step S4 can be controlled within the range of -196℃ to -150℃, and the deformation is achieved through 5-8 passes of stepped rolling, with a deformation of 5-10% per pass. Between passes, the billet is re-immersed in a cooling medium (liquid nitrogen) for 5-10 minutes to ensure uniform temperature in the core of the billet. This operation effectively avoids the risk of adiabatic temperature rise and cracking caused by large deformation in a single pass.

[0051] It should be noted that the smelting, casting, rolling, solution treatment, quenching, and aging operations described in the embodiments of the present invention can all be performed using conventional equipment and process parameters in the field of metal processing. For example, smelting is carried out in a pit-type resistance furnace, rolling is carried out on a two-roll experimental mill, solution treatment is carried out in a box-type heat treatment furnace, and aging is carried out in an air-circulating furnace.

[0052] The present invention will be further described in detail below through specific embodiments, but the implementation of the present invention is not limited thereto.

[0053] Example 1:

[0054] This embodiment provides a high-strength and high-toughness rare-earth aluminum alloy with the following alloy composition (mass fraction): Cu 4.2%, Mg 1.0%, Ti 0.1%, Y 0.25%, with the balance being Al and unavoidable impurities.

[0055] This embodiment also provides a method for preparing the high-strength and high-toughness rare-earth aluminum alloy: The alloy is prepared according to the above-mentioned alloy composition. Pure aluminum, Al-50Cu, Al-50Mg, Al-10Ti, and Al-10Y master alloys are added to a melting furnace and melted at 750°C. After the alloy is completely melted, it is refined, degassed, and slag-removed. Then, it is cast into a cast aluminum alloy billet at 720°C. The cast billet is rolled at room temperature with a deformation of 50%, obtaining a room temperature rolled sheet. The room temperature rolled sheet is heated to 500±5°C, held for 2 hours, and then water-quenched. The quenched sheet is rolled at -196°C (liquid nitrogen temperature) with a deformation of 40%, obtaining a cryogenic rolled sheet. The cryogenic rolled sheet is aged at 170±5°C for 3 hours, followed by water quenching, to obtain the high-strength and high-toughness rare-earth aluminum alloy.

[0056] Figure 2 The as-cast microstructures of the Y-microalloyed aluminum alloy prepared in this embodiment were compared with those of the alloy without Y addition. The results show that the addition of rare earth Y significantly refined the grain size. Figure 2 (a)), while the alloy without rare earth elements exhibits a coarse as-cast structure. Figure 2 (b) The high-strength and high-toughness rare-earth aluminum alloy obtained in this embodiment was tested for mechanical properties at room temperature. Its hardness was 169 HV, tensile strength was 638 MPa, yield strength was 427 MPa, and elongation after fracture was 10.9%.

[0057] Example 2:

[0058] This embodiment provides a high-strength and high-toughness rare-earth aluminum alloy with the following alloy composition (mass fraction): Cu 3.5%, Mg 0.8%, Ti 0.2%, Y 0.2%, and the balance being Al and unavoidable impurities.

[0059] The preparation method provided in this embodiment differs from that in Example 1 in the changes in process parameters. The room temperature rolling deformation is 40%; the solution treatment holding time is 3 hours; the cryogenic rolling deformation is 45%; and the aging treatment holding time is 6 hours. The remaining steps are the same as in Example 1.

[0060] Figure 3 (a) is an optical microstructure image of the as-cast alloy of this embodiment after room temperature rolling and solution treatment. The image shows that its microstructure consists of a small amount of residual deformation structure and recrystallized equiaxed grains. In contrast, the as-cast alloy of the control sample without rare earth Y exhibits a single equiaxed grain structure. Figure 3 (b) After room temperature-cryogenic double-stage deformation heat treatment, the microstructure of the aluminum alloy is as follows: Figure 4 As shown in (a), the grains are significantly elongated along the deformation direction. The high-strength and high-toughness rare-earth aluminum alloy obtained in this embodiment was tested for mechanical properties at room temperature. Its hardness was 163 HV, tensile strength was 602 MPa, yield strength was 418 MPa, and elongation after fracture was 12.2%.

[0061] Example 3:

[0062] This embodiment provides a high-strength and high-toughness rare-earth aluminum alloy with the following alloy composition (mass fraction): Cu 4.5%, Mg 1.5%, Ti 0.1%, Y 0.15%, with the balance being Al and unavoidable impurities.

[0063] The preparation method provided in this embodiment differs from that in Example 1 in that: the room temperature rolling deformation is 45%; the solution treatment holding time is 1.5 hours; the cryogenic rolling deformation is 50%; and the aging treatment holding time is 8 hours. The remaining steps are the same as in Example 1.

[0064] Optical micrograph of the microstructure of the aluminum alloy as follows Figure 4 As shown in (b), after room temperature rolling and cryogenic rolling, the alloy grains are significantly elongated along the rolling direction, forming a fibrous deformed structure. Scanning electron microscopy microstructure ( Figure 5 This further indicates that a large number of fine second-phase particles are dispersed in the aluminum matrix. The high-strength, high-toughness rare-earth aluminum alloy obtained in this embodiment was tested for its mechanical properties at room temperature. The results showed a hardness of 165 HV, a tensile strength of 633 MPa, a yield strength of 425 MPa, and an elongation after fracture of 11.3%.

[0065] Example 4:

[0066] This embodiment provides a high-strength and high-toughness rare-earth aluminum alloy with the following alloy composition (mass fraction): Cu 4.0%, Mg 1.0%, Ti 0.15%, Y 0.2%, with the balance being Al and unavoidable impurities.

[0067] The preparation method provided in this embodiment differs from that in Example 1 in that the Y content in the alloy composition is 0.2% and the cryogenic rolling deformation is 60%. The remaining steps (room temperature rolling deformation of 50%, solution treatment at 500℃ for 2 hours, and aging at 170℃ for 3 hours) are the same as in Example 1.

[0068] Figure 6 The microstructure of the high-strength and tough rare-earth aluminum alloy prepared in this embodiment shows the elemental distribution. Al, as the matrix element, is distributed continuously and uniformly over a large area. Cu and Mg exhibit significant co-segregation characteristics, mainly enriched in the grain boundary region with highly overlapping enrichment positions, indicating the formation of Al2CuMg or Al2Cu strengthening phases, with relatively low content inside the grains. Ti is relatively dispersed, and Y element enrichment positions are accompanied by Cu element, forming Al-Cu-Y intermetallic compounds. Figure 7 The image shows a transmission electron microscope (TEM) image of the aged precipitates, revealing a certain density of dislocation lines in the matrix, with some dislocations pinned by the precipitates. Room temperature mechanical property tests were performed on the aluminum alloy of the composition described in Example 4, which underwent room temperature-cryogenic double-stage rolling. The alloy exhibited a hardness of 176 HV, a tensile strength of 658 MPa, a yield strength of 445 MPa, and an elongation after fracture of 10.7%. Figure 8 The room temperature tensile stress-strain curves of the same aluminum alloy with different treatment methods are shown in this embodiment. Among them, the room temperature-cryogenic double-rolled state exhibits the best mechanical properties, with its tensile strength and yield strength being significantly higher than those of other treatment states, while maintaining good plasticity.

[0069] This invention utilizes the synergistic effect of rare earth element Y and room temperature-cryogenic dual-stage deformation heat treatment to fully leverage grain refinement strengthening, deformation strengthening, and precipitation strengthening mechanisms, resulting in Al-Cu-Mg-Ti aluminum alloys that possess both high strength and good plasticity. The resulting aluminum alloys have a hardness ≥160HV, tensile strength ≥600MPa, yield strength ≥410MPa, and elongation after fracture ≥10%, making them suitable for aerospace, rail transportation, and automotive lightweighting applications.

[0070] Scale settings instructions:

[0071] To better verify the beneficial effects of the present invention, the following comparative examples are provided:

[0072] Comparative Example 1:

[0073] This comparative example provides a rare earth aluminum alloy with the same alloy composition (mass fraction) as in Example 4 (Cu 4.0%, Mg 1.0%, Ti 0.15%, Y 0.2%).

[0074] The difference between this comparative example and Example 4 is that after melting and casting according to the composition of Example 4, it is directly dissolved at 500°C for 2 hours and water quenched, and finally aged at 170°C for 3 hours.

[0075] The aluminum alloy was tested for mechanical properties at room temperature. Its hardness reached 125HV, tensile strength was 315MPa, yield strength was 220MPa, and elongation after fracture was 14.6%.

[0076] Comparative Example 2:

[0077] This comparative example provides a rare earth aluminum alloy with the following alloy composition (mass fraction): Cu 3.5%, Mg 0.8%, Ti 0.2%, with the balance being Al and unavoidable impurities. The difference between this comparative example and Example 2 is that rare earth Y is not added and deep cryogenic rolling and subsequent aging treatment are not performed; that is, only room temperature rolling and solution treatment are performed. The specific steps are as follows: after melting and casting according to the composition of Example 4, room temperature rolling deformation of 40% is performed, followed by solution treatment at 500°C for 3 hours and water quenching.

[0078] The optical microstructure of this comparison ( Figure 2 (b) shows that the alloy obtained a uniform equiaxed recrystallized structure after room temperature rolling and 500°C solution treatment.

[0079] Comparative Example 3:

[0080] This comparative example provides a rare earth aluminum alloy with the same alloy composition (mass fraction) as in Example 3 (Cu 4.5%, Mg 1.5%, Ti 0.1%, Y 0.15%).

[0081] The difference between this comparative example and Example 3 is that deep cryogenic rolling is not performed; that is, only room temperature rolling, solution treatment, and aging treatment are performed. The specific steps are as follows: after melting and casting according to the composition of Example 3, room temperature rolling deformation is 45%, solution treatment is performed at 500°C for 2 hours, followed by water quenching, and aging at 170°C for 3 hours, followed by water quenching.

[0082] The aluminum alloy obtained in this comparative example was tested for mechanical properties at room temperature. Its hardness reached 123 HV, tensile strength was 385 MPa, yield strength was 238 MPa, and elongation after fracture was 20.7%.

[0083] Comparative Example 4:

[0084] This comparative example provides a rare earth aluminum alloy with the following alloy composition (mass fraction): Cu 4.2%, Mg 1.0%, Ti 0.1%, Y 0%, with the balance being Al and unavoidable impurities.

[0085] The difference between this comparative example and Example 1 is that rare earth Y is not added and the mixture is prepared according to the above composition, melted and cast, then rolled at room temperature with a deformation of 30%, solution-quenched at 500°C for 2 hours, water-quenched, cryogenically rolled with a deformation of 30%, and aged at 170°C for 3 hours.

[0086] The aluminum alloy was tested for mechanical properties at room temperature, and its hardness reached 144 HV, tensile strength was 460 MPa, yield strength was 327 MPa, and elongation after fracture was 8.1%. Compared with Example 1, the aluminum alloy without added Y and with smaller deformation during room temperature cold rolling and deep cold rolling had lower strength and elongation after fracture, and could not meet the high strength and toughness requirements of the present invention.

Claims

1. A high-strength and high-toughness rare-earth aluminum alloy, characterized in that, The high-strength and high-toughness rare-earth aluminum alloy, by mass fraction, consists of Cu 3.5%–4.5%, Mg 0.5%–1.5%, Ti 0.1%–0.2%, Y 0.1%–0.3%, with the balance being Al and unavoidable impurities; the preparation method of the high-strength and high-toughness rare-earth aluminum alloy is as follows: (1) Smelting and casting: According to the composition of high strength and toughness rare earth aluminum alloy, the raw materials are smelted and then cast into ingots to obtain as-cast aluminum alloy billets; (2) Room temperature rolling: The as-cast aluminum alloy billets obtained in step (1) are rolled and deformed at room temperature to obtain room temperature rolled plates; (3) Solution treatment: The room temperature rolled plates obtained in step (2) are heated to the solution temperature and held at that temperature, and then quenched; (4) Cryogenic rolling: The plates quenched in step (3) are rolled and deformed under cryogenic conditions to obtain cryogenic rolled plates; (5) Aging treatment: The cryogenic rolled plates obtained in step (4) are artificially aged and then water quenched to obtain the high strength and toughness aluminum alloy.

2. The high-strength and high-toughness rare-earth aluminum alloy according to claim 1, characterized in that, The high-strength and high-toughness rare earth aluminum alloy is composed of Cu 3.8~4.2%, Mg 0.8~1.2%, Ti 0.13~0.18%, Y 0.15~0.25%, with the balance being Al and unavoidable impurities, by mass fraction.

3. The high-strength and high-toughness rare-earth aluminum alloy according to claim 2, characterized in that, The high-strength and high-toughness rare earth aluminum alloy is composed of Cu 4.0%, Mg 1.0%, Ti 0.15%, Y 0.2% by mass, with the balance being Al and unavoidable impurities.

4. A high-strength and high-toughness rare-earth aluminum alloy according to any one of claims 1 to 3, characterized in that, The high-strength and high-toughness rare earth aluminum alloy has a hardness ≥160HV, tensile strength ≥600MPa, yield strength ≥410MPa, and elongation after fracture ≥10%.

5. The method for preparing high-strength and high-toughness rare-earth aluminum alloys using a room temperature-cryogenic dual-stage deformation heat treatment according to claim 1, characterized in that, The process described in step (1) of preparing high-strength and tough rare earth aluminum alloy components, melting and casting them into ingots to obtain as-cast aluminum alloy billets refers to preparing components by mass fraction of Cu 3.5%–4.5%, Mg 0.5%–1.5%, Ti 0.1%–0.2%, Y 0.1%–0.3%, and the balance Al, and sequentially adding Al-Cu, Al-Mg, Al-Ti, and Al-Y master alloys. After complete melting, the mixture is stirred, degassed, and slag is removed. After standing, the alloy melt is then poured into a metal mold to obtain as-cast aluminum alloy billets.

6. The method for preparing high-strength and high-toughness rare-earth aluminum alloys using a room temperature-cryogenic dual-stage deformation heat treatment according to claim 1, characterized in that, In step (2), the deformation amount of room temperature rolling is 30% to 50%.

7. The method for preparing high-strength and high-toughness rare-earth aluminum alloys using a room temperature-cryogenic dual-stage deformation heat treatment according to claim 1, characterized in that, In step (3), the solution temperature is 495~505℃ and the heat preservation time is 1~3h.

8. The method for preparing high-strength and high-toughness rare-earth aluminum alloys using a room temperature-cryogenic dual-stage deformation heat treatment according to claim 1, characterized in that, In step (4), the cryogenic condition is -196°C; the rolling temperature is -196°C to -150°C, and the deformation is 40% to 60%.

9. The method for preparing high-strength and high-toughness rare-earth aluminum alloys using a room temperature-cryogenic dual-stage deformation heat treatment according to claim 1, characterized in that, In step (5), the aging treatment temperature is 165~175℃ and the heat preservation time is 3~8h.

Images