Multi-directional forging method for stepped cooling particle reinforced aluminum matrix composite sheath

Abstract

The invention belongs to the field of aluminum-based composites, and particularly relates to a multi-directional forging method for a stepped cooling particle reinforced aluminum-based composite sheath, in particular to a multi-directional forging method for a stepped cooling particle reinforced aluminum-based composite sheath. The method aims at solving the problem that in the multi-directional forging process of an existing particle reinforced aluminum matrix composite, due to the fact that room-temperature plasticity is insufficient and a hot working window is narrow, collaborative improvement of strength and plasticity is difficult to achieve. Multi-directional forging is carried out in a wrapping state; the multi-directional forging process adopts a temperature decreasing strategy: the initial forging temperature is set to be 395-495 DEG C, when the temperature of the blank is lower than the initial forging temperature by 100 DEG C, the blank is subjected to remelting annealing treatment, and the initial temperature for restarting forging in each round is reduced by 5-20 DEG C compared with that in the previous round. The performance bottleneck of multi-directional forging of the particle reinforced aluminum matrix composite is broken through, and collaborative improvement of strength and plasticity is achieved.

Description

Technical Field

[0001] The invention belongs to the field of aluminum-based composite materials, and in particular relates to a multi-directional forging method for a particle-reinforced aluminum-based composite material sheath with step-cooling. Background Art

[0002] Driven by major strategic projects such as my country's deep space exploration, manned space flight, high-resolution earth observation, and large-scale nuclear power plants, equipment components have put forward stringent requirements on material performance, such as extreme, lightweight, and long life; as a key structural material supporting the development of such high-end equipment, particle-reinforced aluminum-based composite materials have become core candidate materials in the field of extreme service environments due to their high specific strength, high specific modulus, wear resistance and other excellent properties. However, in practical applications, such materials not only need to maintain the advantages of high strength and high modulus, but also need to achieve a synergistic improvement in plastic forming ability and strong-plastic matching level to meet the forming needs and service reliability of complex components. At present, existing particle-reinforced aluminum-based composite materials generally have the problems of insufficient room temperature plasticity and a narrow hot working window, which has become a key bottleneck restricting their adaptation to diverse and complex application scenarios.

[0003] Large plastic deformation technology is considered an important approach to breaking through the performance limits of particle-reinforced aluminum-based composites because it can achieve ultra-large cumulative strain, significantly refine grains, and increase material density. Multi-directional forging technology, by cyclically applying loads in three mutually perpendicular directions, effectively eliminates the "deformation dead zone" in traditional unidirectional deformation, promotes microstructural homogenization, and significantly improves the material's overall mechanical properties. Furthermore, this technology can be implemented on conventional hydraulic presses and presses, facilitating the engineering preparation of large-scale components. It has significant technical advantages and application potential in high-end equipment manufacturing.

[0004] In the multi-directional forging process, forging temperature is the core variable that determines the final microstructure and performance of forgings, but its parameter optimization faces multiple contradictions: although high forging temperature can significantly reduce the deformation resistance of the material and improve plastic formability, it will inhibit the dynamic recrystallization process and accelerate grain growth, which is not conducive to microstructure refinement and toughening, and may even cause overburning defects due to excessively high temperature; low forging temperature will greatly increase the cracking tendency of the material due to the sudden increase in deformation resistance, especially for composite materials with limited plasticity, which can easily cause forgings to be scrapped; even within the theoretically "suitable" temperature range, as the number of forging passes increases, the accumulated work hardening and microstructure refinement saturation effects inside the material will gradually become prominent, resulting in a significant decrease in the contribution rate of subsequent passes to performance improvement, making it difficult to fully utilize the technical advantages of large plastic deformation.

[0005] For particle-reinforced aluminum-based composites, the above contradiction is even more prominent: the introduction of reinforcement particles (such as silicon carbide, boron carbide, etc.) will significantly reduce the plastic deformation ability of the aluminum matrix, resulting in a higher sensitivity of the material to temperature changes; in order to compensate for the loss of plasticity and reduce deformation resistance, particle-reinforced aluminum-based composites usually require a higher forging temperature than the matrix aluminum alloy, but this further compresses the "safe processing window" and increases the risk of microstructure coarsening and overburning. At present, there is still a lack of systematic patented technical solutions and clear process guidance for the design of temperature parameters in the multi-directional forging process of particle-reinforced aluminum-based composites, especially how to balance the needs of "plasticity assurance-cracking suppression-microstructure refinement" through a dynamic temperature control strategy that evolves with the pass sequence to achieve the coordinated optimization of strength and plasticity.

[0006] In summary, existing technologies are unable to effectively address the multi-directional forging challenges of particle-reinforced aluminum-based composites, which are caused by insufficient room-temperature plasticity and a narrow hot working window, making it difficult to achieve a synergistic improvement in the material's strength and plasticity. Therefore, the development of a stepped cooling-encased multi-directional forging method specifically for particle-reinforced aluminum-based composites, which, through precise temperature control and process synergy, can overcome existing performance bottlenecks, has important theoretical significance and engineering value for promoting the large-scale application of such materials in major strategic projects. Summary of the Invention

[0007] The present invention aims to address the problem of insufficient room-temperature plasticity and a narrow hot working window in conventional particle-reinforced aluminum-based composite materials during multi-directional forging, making it difficult to achieve a synergistic improvement in strength and plasticity. The invention provides a multi-directional forging method for particle-reinforced aluminum-based composite materials with stepped cooling.

[0008] A multi-directional forging method for particle-reinforced aluminum-based composite material sheath with step-down cooling is specifically carried out in the following steps:

[0009] 1. Using aluminum alloy to encase the particle reinforced aluminum matrix composite material blank to form an encased blank;

[0010] 2. placing the sheathed blank in a heating furnace for preheating and heat preservation treatment;

[0011] 3. Multi-directional forging is performed on the preheated and heat-insulated sheathed billet, with cyclic loading in three mutually perpendicular directions in sequence. During the multi-directional forging process, when the billet temperature drops to 100°C below the initial forging temperature, the billet is annealed in the furnace, and the temperature of each annealing is 5°C to 20°C lower than the initial forging temperature of the previous stage.

[0012] 4. After completing the preset forging passes, place the forging in the air to cool to room temperature;

[0013] 5. The aluminum alloy sheath on the outer layer of the forging is removed by turning; the composite material forging after the sheath is removed is heat treated to complete the process.

[0014] Preferably, the reinforcement in the particle-reinforced aluminum-based composite material blank in step one is a mixture of one or more of silicon carbide, aluminum oxide, tungsten, boron carbide, cerium dioxide, silicon nitride and titanium diboride; the reinforcement particle size is 2μm~50μm, and the volume fraction of the reinforcement is 0.5%~41%; the preparation method of the blank is powder metallurgy, stirring casting or hot isostatic pressing.

[0015] Preferably, the material of the aluminum alloy in step 1 and the aluminum matrix of the particle-reinforced aluminum-based composite material ingot are deformed aluminum alloys of the same series.

[0016] Preferably, in step one, the aluminum alloy as a sheath includes an outer shell and an upper cover, the inner diameter of the outer shell is 0.1 mm to 0.5 mm smaller than the diameter of the particle-reinforced aluminum-based composite material blank, the diameter of the upper cover is 0.1 mm to 0.5 mm larger than the diameter of the particle-reinforced aluminum-based composite material blank, and the thickness of the outer shell and the upper cover are both 10% to 30% of the diameter of the particle-reinforced aluminum-based composite material blank.

[0017] Preferably, the preheating temperature of the preheating and heat preservation treatment in step 2 is 395° C. to 495° C., and the heat preservation time is 0.8 to 3.5 times the outer diameter of the sheathed blank, wherein the unit of the heat preservation time is min, and the unit of the outer diameter of the sheathed blank is mm.

[0018] Preferably, the deformation range of a single pass in the multidirectional forging process in step three is 5% to 30%, and the cumulative deformation range is 120% to 450%.

[0019] Preferably, in step three, the cyclic loading process along three mutually perpendicular directions keeps the single-pass deformation in each direction the same.

[0020] Preferably, the equipment used for forging is a press, an air hammer or a hydraulic press; the forging speed is 1.5 mm / s to 9 mm / s; the surfaces of the upper and lower anvils are coated with a lubricant, which is graphite powder, graphite flakes or graphite + engine oil, and the temperature of the upper and lower anvils is 0 to 35°C lower than the preheating temperature of the sheathed particle-reinforced aluminum-based composite material.

[0021] Preferably, the re-melting and heat preservation treatment in step three is carried out when the current actual temperature of the sheathed blank forged in the previous pass is 100°C or higher lower than the preheating temperature of the sheathed blank. The temperature of each re-melting annealing is 5°C to 20°C lower than the forging starting temperature of the previous stage, and the heat preservation time is 0.2 to 2 times the initial outer diameter of the sheathed blank, where the unit of the heat preservation time is min and the unit of the outer diameter of the sheathed blank is mm.

[0022] Preferably, the heat treatment in step five includes solution treatment + aging treatment and annealing.

[0023] Beneficial effects of the present invention:

[0024] The cooling multi-directional forging process proposed in the present invention can achieve a synergistic improvement in the strength and plasticity of multi-directional forged particle-reinforced aluminum-based composite materials through a temperature gradient reduction design. The initial higher forging temperature can make full use of the good plasticity of the material in the initial stage of forging, significantly reduce the deformation resistance, ensure that the composite material does not crack under large deformation, and promote the crushing of the initial structure; as the number of forging passes increases, the initial temperature of the next round of multi-directional forging is gradually reduced, which effectively inhibits the dynamic recovery and recrystallization process, promotes the continuous accumulation of dislocation density, and avoids excessive growth and coarsening of grains during the insulation process. Compared with the multi-directional forging process with a constant initial forging temperature, the present invention can obtain better mechanical properties under the same cumulative deformation amount. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 1 is the room temperature tensile engineering stress-strain curve of Example 1 of the present invention and Comparative Example 1;

[0026] Figure 2 2 are the room temperature tensile engineering stress-strain curves of Example 2 of the present invention and Comparative Example 2. DETAILED DESCRIPTION

[0027] Specific embodiment 1: This embodiment is a multi-directional forging method for particle-reinforced aluminum-based composite material sheath with step-down cooling, which is specifically carried out in the following steps:

[0028] 1. Using aluminum alloy to encase the particle reinforced aluminum matrix composite material blank to form an encased blank;

[0029] 2. placing the sheathed blank in a heating furnace for preheating and heat preservation treatment;

[0030] 3. Multi-directional forging is performed on the preheated and heat-insulated sheathed billet, with cyclic loading in three mutually perpendicular directions in sequence. During the multi-directional forging process, when the billet temperature drops to 100°C below the initial forging temperature, the billet is annealed in the furnace, and the temperature of each annealing is 5°C to 20°C lower than the initial forging temperature of the previous stage.

[0031] 4. After completing the preset forging passes, place the forging in the air to cool to room temperature;

[0032] 5. The aluminum alloy sheath on the outer layer of the forging is removed by turning; the composite material forging after the sheath is removed is heat treated to complete the process.

[0033] Specific implementation method two: the difference between this embodiment and specific implementation method one is that: in step one, the reinforcing body in the particle reinforced aluminum matrix composite blank is one or a mixture of several of silicon carbide, aluminum oxide, tungsten, boron carbide, cerium dioxide, silicon nitride and titanium diboride; the reinforcing body particle size is 2 μm-50 μm, and the volume fraction of the reinforcing body is 0.5%-41%; the preparation method of the blank is powder metallurgy, stirring casting or hot isostatic pressing. The others are the same as specific implementation method one.

[0034] Specific implementation method three: the difference between this embodiment and specific implementation method one is that: in step one, the material of the aluminum alloy and the aluminum matrix of the particle reinforced aluminum matrix composite blank are the same series of deformed aluminum alloys. The others are the same as specific implementation method one.

[0035] This embodiment uses the same series of deformed aluminum alloys as the cladding, and uses the similar thermal expansion coefficients and plastic deformation characteristics of the two to realize the cooperative deformation in the forging process. This matching avoids the interface stress concentration caused by the performance difference of the heterogeneous material cladding (such as a steel cladding), forms uniform radial compressive stress restraint on the composite blank by the cladding, effectively suppresses the peeling and crack initiation of the particle-matrix interface, and provides additional plastic support for low plasticity materials.

[0036] Specific implementation method four: the difference between this embodiment and specific implementation method one is that: in step one, the aluminum alloy as the cladding includes an outer shell and an upper cover, the inner diameter of the outer shell is 0.1 mm-0.5 mm smaller than the diameter of the particle reinforced aluminum matrix composite blank, the diameter of the upper cover is 0.1 mm-0.5 mm larger than the diameter of the particle reinforced aluminum matrix composite blank, and the thickness of the outer shell and the upper cover is 10%-30% of the diameter of the particle reinforced aluminum matrix composite blank. The others are the same as specific implementation method one.

[0037] The interference fit design of the inner diameter of the outer shell of the cladding in this embodiment is 0.1 mm-0.5 mm smaller than the diameter of the blank, which forms a tightly fitted closed space after hot charging, and significantly reduces the heat loss in the forging process. The thickness design of the outer shell and the upper cover is 10%-30% of the diameter of the blank, which not only reduces the temperature gradient as a heat shield (especially in multi-pass cycles), but also buffers the local stress peak through its own plastic flow, and widens the "effective hot working window" of the material.

[0038] Specific implementation method five: the difference between this embodiment and specific implementation method four is that: in step two, the preheating temperature of the preheating and holding treatment is 395°C-495°C, and the holding time is 0.8-3.5 times the outer diameter of the cladding blank, wherein the unit of the holding time is min, and the unit of the outer diameter of the cladding blank is mm. The others are the same as specific implementation method four.

[0039] In this embodiment, the can acts as a heat transfer medium, ensuring that heat is evenly distributed to the core of the billet during the preheating phase, preventing a sudden drop in plasticity due to localized low temperatures. During the multi-directional forging process, the can continuously maintains a stable billet temperature, reducing the risk of plastic fluctuations and cracking caused by temperature fluctuations.

[0040] Specific embodiment 6: This embodiment differs from specific embodiment 1 in that the deformation range of a single pass in the multi-directional forging process in step 3 is 5% to 30%, and the cumulative deformation range is 120% to 450%. Other aspects are the same as specific embodiment 1.

[0041] Specific embodiment 7: This embodiment differs from specific embodiment 6 in that the cyclic loading process in three mutually perpendicular directions in step 3 keeps the single-pass deformation in each direction the same. Other aspects are the same as specific embodiment 6.

[0042] This implementation method, by alternating loading directions, gradually closes defects such as pores and looseness within the blank under the action of compressive stress in different directions, thus avoiding the risk of defects expanding in a single direction during unidirectional deformation. Cyclic deformation also promotes the breakup and uniform distribution of particle agglomerates, reducing interfacial stress concentration. At the same time, multi-directional plastic flow achieves uniform grain refinement, laying the structural foundation for enhanced plasticity. Cyclic loading along three mutually perpendicular directions while maintaining the same deformation per pass avoids texture segregation and performance anisotropy caused by asymmetric deformation. Symmetrical deformation paths uniformly release internal stress in the material in three dimensions, reducing crack sources caused by local strain concentration.

[0043] Specific Embodiment 8: This embodiment differs from Specific Embodiment 6 in that the forging equipment used is a press, air hammer, or hydraulic press; the forging speed is 1.5 mm / s to 9 mm / s; the upper and lower anvils are coated with a lubricant consisting of graphite powder, graphite flakes, or graphite plus engine oil; and the upper and lower anvils are kept at a temperature 0 to 35°C lower than the preheating temperature of the encapsulated particle-reinforced aluminum-based composite material. Other aspects are the same as Specific Embodiment 6.

[0044] Specific Embodiment 9: This embodiment differs from Specific Embodiment 6 in that the annealing treatment in step 3 is performed when the current actual temperature of the previously forged canned blank is 100°C or higher below the canned blank's preheating temperature. The temperature of each annealing treatment is 5°C to 20°C lower than the previous forging starting temperature, and the holding time is 0.2 to 2 times the initial canned blank's outer diameter. The holding time is expressed in minutes, and the canned blank's outer diameter is expressed in mm. Other aspects are the same as Specific Embodiment 6.

[0045] The preheating temperature of the embodiment is set to a higher range of 395℃-495℃, and the plasticity reserve advantage of the material at high temperature is fully utilized (at this time, the dislocation migration ability of the aluminum matrix is strong, and the deformation resistance is low). The initial high temperature can reduce the deformation resistance and ensure that the large deformation accumulation is completed at the best plasticity stage of the material, realize rapid densification and initial organization crushing, and avoid the risk of cracking at low temperature. When the billet temperature is lower than the initial forging temperature by 100℃, the billet is annealed, and the annealing temperature is reduced by 5℃-20℃ lower than the previous stage each time, forming a precise stepwise temperature reduction curve. This strategy solves the inherent contradiction at a single temperature: it avoids the inhibition of dynamic recrystallization and grain coarsening caused by continuous high temperature; by gradually reducing the temperature to adapt to the degree of work hardening of the material, as the deformation accumulates, the lower temperature can promote the continuous increase of dislocation density, while inhibiting the loss of strength caused by excessive softening. The holding time between passes ensures the thermal permeability of the billet, combined with the design that the upper and lower anvil temperatures are 0-35℃ lower than the preheating temperature, reducing surface heat loss and temperature gradient. The stepwise temperature reduction allows each pass to be performed within the "dynamic plasticity window" of the material, avoiding plasticity exhaustion and crack propagation due to excessively low temperature, or overburning defects due to excessively high temperature.

[0046] Specific embodiment ten: different from specific embodiment one, the heat treatment in step five includes solution + aging treatment, annealing. The rest is the same as specific embodiment one.

[0047] The effect of the application is verified by the following test:

[0048] Example 1: A multi-directional forging method for a particle reinforced aluminum matrix composite material with stepwise temperature reduction is carried out according to the following steps:

[0049] I. A particle reinforced aluminum matrix composite material billet is prepared by a vacuum hot pressing sintering method, and the composition is (10.5vol.%B4Cp+16.5vol.%W) / 6061Al, wherein the average particle size of B4C particles and W particles is 9μm and 6μm respectively, and the average particle size of 6061Al powder is 14μm. The composite material billet is sleeved with 6092Al alloy;

[0050] II. The sleeved particle reinforced aluminum matrix composite material is subjected to preheating and holding treatment; the preheating temperature is 490℃, and the holding time is 220min; the upper and lower anvil plates are heated to 485℃ and held;

[0051] 3. Use an 800-ton press for multi-directional forging. Before forging, evenly coat the upper and lower anvil surfaces with graphite powder as a lubricant. Perform multi-directional forging along the axial direction, the first radial direction, and the second radial direction perpendicular to the first radial direction. The forging speed is 2.5 mm / s, and the deformation of each pass is 15%. After 3 and 6 passes, the billet is returned to the furnace for annealing. The annealing temperature is 475°C and 460°C, respectively, and the holding time is 100 minutes. After 9 passes of forging, the billet is air-cooled to room temperature and the 6092Al sheath is removed by turning. The composite forgings are subjected to solution (525°C / 2h, water quenching) and aging (170°C / 5h) heat treatments. According to the national standard GB / T 32498-2016, the room temperature tensile properties test is carried out, and the obtained engineering stress-strain curve is as follows: Figure 1 shown.

[0052] Comparative Example 1: A particle-reinforced aluminum-based composite material blank was prepared by vacuum hot pressing and sintering. The composition was (10.5 vol.% B4Cp + 16.5 vol.% W) / 6061Al, where the average particle sizes of the B4C and W particles were 9 μm and 6 μm, respectively, and the average particle size of the 6061Al powder was 14 μm. The composite material blank was sheathed with 6092Al alloy. An 800-ton press was used for multi-directional forging. Before forging, graphite powder was evenly coated on the surfaces of the upper and lower anvils as a lubricant. Multi-directional forging was performed in the axial direction, the first radial direction, and the second radial direction perpendicular to the first radial direction of the blank at a forging speed of 2.5 mm / s, with a deformation of 15% per pass. The sheathed blank was heated to 490°C and maintained at this temperature for 220 minutes. Simultaneously, the upper and lower anvils were heated to 485°C and maintained at this temperature. After 3 and 6 passes, the blanks were annealed at 490°C for 100 minutes. After 9 passes, the blanks were air-cooled to room temperature and the 6092Al sheath was removed by turning. The composite forgings were subjected to solution heat treatment (525°C / 2h, water quenching) and aging heat treatment (170°C / 5h). Room temperature tensile properties were tested according to the national standard GB / T 32498-2016, and the engineering stress-strain curves were obtained as shown below. Figure 1 shown.

[0053] Example 2: A particle-reinforced aluminum-based composite billet was prepared using a stir casting method. The billet had a composition of 15.5 vol.% SiCp / 7050Al, where the SiC particles had an average particle size of 8 μm. The composite billet was encapsulated with 7075Al alloy. The encapsulated particle-reinforced aluminum-based composite was preheated to 455°C for 180 minutes. The upper and lower anvils were heated to 455°C and maintained.

[0054] A 1000-ton press was used for multi-directional forging. Before forging, graphite powder was evenly coated on the upper and lower anvil surfaces as a lubricant. Multi-directional forging was performed in the axial direction, the first radial direction, and the second radial direction perpendicular to the first radial direction. The forging speed was 2.4 mm / s, and the deformation per pass was 18%. After 3, 6, and 9 passes, the billet was annealed at 445°C and 435°C, respectively, with a holding time of 140 minutes. After 12 passes of forging, the billet was air-cooled to room temperature and the 7075Al sheath was removed by turning. The composite forgings were subjected to solution treatment (470°C / 2h, water quenching) and aging (120°C / 20h). Room temperature tensile properties were tested according to the national standard GB / T 32498-2016, and the engineering stress-strain curves obtained were as follows: Figure 2 shown.

[0055] Comparative Example 2: A particle-reinforced aluminum-based composite billet was prepared using a stir casting method. The composition was 15.5 vol.% SiCp / 7050Al, where the SiC particles had an average particle size of 8 μm. The composite billet was sheathed with 7075Al alloy and multi-directionally forged using a 1000-ton press. Before forging, graphite powder was evenly coated on the upper and lower anvils as a lubricant. Multi-directional forging was performed in the billet's axial direction, along a first radial direction, and then along a second radial direction perpendicular to the first radial direction. The forging speed was 2.4 mm / s, and the deformation per pass was 18%. The sheathed billet was heated to 455°C and held at this temperature for 180 minutes. Simultaneously, the upper and lower anvils were heated to 455°C and held at this temperature. After 3, 6, and 9 passes, the billet was annealed at 455°C for 140 minutes. After 12 passes of forging, the billet was air-cooled to room temperature and the 7075Al sheath was removed by turning. The composite forgings were subjected to solution treatment (470°C / 2h, water quenching) and aging (120°C / 20h). Room temperature tensile properties were tested according to national standard GB / T 32498-2016, and the engineering stress-strain curves were as follows: Figure 2 shown.

[0056] from Figure 1 、 Figure 2 It can be seen from the tensile properties that Example 1 and Example 2 achieve a synergistic improvement in strength and plasticity by gradually reducing the forging temperature.

[0057] The solution treatment + aging or annealing treatment in step 5 forms a synergistic effect of "deformation-heat treatment" with multi-directional forging:

[0058] Solution treatment can eliminate residual stress in the forging process and dissolve supersaturated solute atoms; aging treatment promotes uniform distribution of precipitated phase, cooperates with the refined grain and uniform particle distribution of the forged structure, and finally realizes the matching improvement of strength and plasticity. Compared with constant temperature forging, step temperature control + heat treatment can improve the tensile strength and elongation (such as Figure 1 , Figure 2 The comparison of examples and comparative examples is shown).

[0059] The synergy of preheating temperature, holding time, forging speed and deformation ensures that the material is in the best state of "low resistance-high plasticity-fine structure" in each deformation. Graphite lubricant reduces friction coefficient and reduces additional stress consumption, further widening the effective processing window. Taking the actual temperature of the blank (100℃ lower than the initial forging temperature) as the trigger condition for re-melting instead of fixed interval, the dynamic regulation of the material thermal state is realized, avoiding the temperature control deviation caused by environmental fluctuations or blank size difference, and significantly improving the process stability.

Claims

1. A multi-directional forging method for particle reinforced aluminum matrix composite material with step cooling, characterized in that The forging method is specifically carried out in the following steps:

1. Using aluminum alloy to encase the particle reinforced aluminum matrix composite material blank to form an encased blank; 2. placing the sheathed blank in a heating furnace for preheating and heat preservation treatment; 3. Multi-directional forging is performed on the preheated and heat-insulated sheathed billet, with cyclic loading in three mutually perpendicular directions in sequence. During the multi-directional forging process, when the billet temperature drops to 100°C below the initial forging temperature, the billet is annealed in the furnace, and the temperature of each annealing is 5°C to 20°C lower than the initial forging temperature of the previous stage.

4. After completing the preset forging passes, place the forging in the air to cool to room temperature; 5. The aluminum alloy sheath on the outer layer of the forging is removed by turning; the composite material forging after the sheath is removed is heat treated to complete the process.

2. The multi-directional forging method for particle-reinforced aluminum-based composite materials with step-cooling according to claim 1, characterized in that The reinforcement in the particle-reinforced aluminum-based composite material blank described in step one is a mixture of one or more of silicon carbide, aluminum oxide, tungsten, boron carbide, cerium dioxide, silicon nitride and titanium diboride; the reinforcement particle size is 2μm~50μm, and the volume fraction of the reinforcement is 0.5%~41%; the preparation method of the blank is powder metallurgy, stirring casting or hot isostatic pressing.

3. The multi-directional forging method for particle-reinforced aluminum-based composite materials with step-down cooling according to claim 1 is characterized in that The material of the aluminum alloy in step 1 and the aluminum matrix of the particle-reinforced aluminum-based composite material ingot are deformed aluminum alloys of the same series.

4. The multi-directional forging method for particle-reinforced aluminum-based composite materials with step-down cooling according to claim 1 is characterized in that In step 1, the aluminum alloy serves as a sheath including an outer shell and an upper cover. The inner diameter of the outer shell is 0.1 mm to 0.5 mm smaller than the diameter of the particle-reinforced aluminum-based composite material blank, and the diameter of the upper cover is 0.1 mm to 0.5 mm larger than the diameter of the particle-reinforced aluminum-based composite material blank. The thickness of the outer shell and the upper cover are both 10% to 30% of the diameter of the particle-reinforced aluminum-based composite material blank.

5. The multi-directional forging method for particle-reinforced aluminum-based composite materials with step-down cooling according to claim 1 is characterized in that The preheating temperature of the preheating and heat preservation treatment in step 2 is 395° C. to 495° C., and the heat preservation time is 0.8 to 3.5 times the outer diameter of the sheathed blank, wherein the unit of the heat preservation time is min, and the unit of the outer diameter of the sheathed blank is mm.

6. The multi-directional forging method for particle reinforced aluminum matrix composite material with step-down cooling according to claim 1, characterized in that The deformation range of a single pass in the multidirectional forging process described in step 3 is 5% to 30%, and the cumulative deformation range is 120% to 450%.

7. The multi-directional forging method for particle reinforced aluminum matrix composite material with step-down cooling according to claim 6, characterized in that In step 3, the cyclic loading process along three mutually perpendicular directions keeps the single-pass deformation in each direction the same.

8. The multi-directional forging method for particle reinforced aluminum matrix composite material with step-down cooling according to claim 6, characterized in that The forging equipment is a press, an air hammer or a hydraulic press; the forging speed is 1.5 mm / s to 9 mm / s; the surfaces of the upper and lower anvils are coated with a lubricant, which is graphite powder, graphite flakes or graphite + engine oil; and the temperature of the upper and lower anvils is 0 to 35°C lower than the preheating temperature of the coated particle-reinforced aluminum-based composite material.

9. The multi-directional forging method for particle-reinforced aluminum-based composite materials with step-cooling according to claim 6, characterized in that In step 3, the re-melting and heat preservation treatment is carried out when the current actual temperature of the sheathed blank after the previous forging is 100°C or more lower than the preheating temperature of the sheathed blank. The temperature of each re-melting annealing is 5°C to 20°C lower than the forging starting temperature of the previous stage, and the heat preservation time is 0.2 to 2 times the initial outer diameter of the sheathed blank. The unit of heat preservation time is min, and the unit of outer diameter of the sheathed blank is mm.

10. The multi-directional forging method for particle reinforced aluminum matrix composite material with step-down cooling according to claim 1, characterized in that The heat treatment in step five includes solution treatment + aging treatment and annealing.

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