TiB2 reinforced Al-Mg-Mn aluminum-based composite material for deep ocean and preparation method of TiB2 reinforced Al-Mg-Mn aluminum-based composite material

Abstract

The invention relates to the field of aluminum-based composite materials for deep ocean ships, in particular to a TiB2 reinforced Al-Mg-Mn aluminum-based composite material for deep ocean and a preparation method of the TiB2 reinforced Al-Mg-Mn aluminum-based composite material. The content of Fe is 0.20 to 0.30 percent; the content of Cu is 0.05 to 0.15 percent; the content of Mn is 0.6 to 0.8 percent; the content of Mg is 4.7 to 4.9 percent; the content of Cr is 0.05 to 0.25 percent; the content of Zn is 0.15 to 0.25 percent; the content of Zr is 0.08 to 0.12 percent; the content of TiB2 is 0.5 to 2.0 percent; the single content of other impurity elements is less than or equal to 0.05%; the total content of other impurity elements is less than or equal to 0.15%; according to the composite material, on the premise that corrosion resistance is kept, synergistic improvement of strength, fatigue resistance and corrosion resistance is achieved, and the requirements for light weight and long service life of deep ocean vessels are met.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of aluminum-based composite materials for deep ocean ships, and in particular to a TiB2 reinforced Al-Mg-Mn aluminum-based composite material for deep ocean ships and a preparation method thereof. BACKGROUND

[0002] With the development of deep ocean ship industry towards lightweight and high performance, Al-Mg-Mn aluminum alloy, as the main alloy for ships, is widely used in marine engineering due to its good corrosion resistance and strength. However, in the complex deep ocean environment, its strength-plasticity matching, corrosion resistance and service life are still difficult to meet the needs.

[0003] With the development of deep ocean ship industry towards lightweight and high performance, Al-Mg-Mn aluminum alloy, due to its excellent corrosion resistance and medium strength, has become a key material for ship structures. However, in the complex deep ocean environment, the traditional Al-Mg-Mn aluminum alloy faces the following challenges: the contradiction between strength and plasticity, Al-Mg-Mn aluminum alloy belongs to non-heat treated strengthening alloy, mainly relying on Mg solid solution strengthening and work hardening, its tensile strength is difficult to meet the needs of high load ship parts. The strength can be improved by cold deformation, but the plasticity will be sacrificed, leading to brittle fracture of the material under impact or cyclic load. The fatigue resistance is insufficient, and under long-term wave load and vibration environment, the fatigue cracks of Al-Mg-Mn aluminum alloy are prone to occur at grain boundaries or inclusions, and the high cycle fatigue limit is difficult to meet the long life requirement of deep ocean ships. Traditional strengthening methods, such as grain refinement or alloying, have limited effect on fatigue performance, and may introduce new stress concentration sources. The corrosion resistance is severely tested, and high salt mist, strong ocean current and microbial attachment in deep ocean environment will accelerate local corrosion such as intergranular corrosion and exfoliation corrosion, and the passivation film (Al2O3 / MgO) of Al-Mg-Mn aluminum alloy may fail due to Cl⁻ corrosion in long-term service.

[0004] Existing methods for improving corrosion resistance, such as micro-alloying or surface coating, are high in cost, complex in process, and may affect the weldability and mechanical properties.

[0005] In summary, there is an urgent need for an Al-Mg-Mn aluminum-based composite material and a preparation method thereof, which can achieve the synergistic improvement of strength, fatigue resistance and corrosion resistance without compromising the inherent corrosion resistance of Al-Mg-Mn aluminum alloy, and meet the lightweight and long life requirements of deep ocean ships. SUMMARY

[0006] The application aims to solve the technical problem of how to provide an Al-Mg-Mn aluminum-based composite material and a preparation method thereof, and realizes the synergistic improvement of strength, fatigue resistance and corrosion resistance without damaging the inherent corrosion resistance of the Al-Mg-Mn aluminum alloy, and meets the lightweight and long-life requirements of deep-ocean ships.

[0007] To achieve the above-mentioned purpose, the first aspect of the application provides a TiB2 reinforced Al-Mg-Mn aluminum-based composite material for deep-ocean use, wherein the components and their weight percentages in the composite material are as follows:

[0008] The content of Si is 0.15-0.20%;

[0009] The content of Fe is 0.20-0.30%;

[0010] The content of Cu is 0.05-0.15%;

[0011] The content of Mn is 0.6-0.8%;

[0012] The content of Mg is 4.7-4.9%;

[0013] The content of Cr is 0.05-0.25%;

[0014] The content of Zn is 0.15-0.25%;

[0015] The content of Zr is 0.08-0.12%;

[0016] The content of TiB2 is 0.5-2.0%;

[0017] The content of other impurity elements is ≤0.05% individually;

[0018] The total content of other impurity elements is ≤0.15%;

[0019] The balance is Al.

[0020] The second aspect of the application provides a preparation method of the above-mentioned TiB2 reinforced Al-Mg-Mn aluminum-based composite material for deep-ocean use, wherein the method comprises:

[0021] Melting and casting, homogenization treatment, extrusion, annealing treatment;

[0022] The process of melting and casting comprises:

[0023] S1, stirring KBF4 and K2TiF6 at 20-30℃ for 2-4min, drying at 190-210℃ for 2.0-3.0h after mixing, to obtain uniformly mixed salt;

[0024] S2, after melting pure Al, adding the uniformly mixed salt obtained in S1 at 840-860 DEG C, carrying out reaction, removing slag, then adding Al2O3, holding for 5-15 min, carrying out first casting to obtain Al-TiB2 preformed ingot;

[0025] In the melting and casting process, the stoichiometric ratio of Ti / B is 1:1-1:2.

[0026] S3, heating the Al-TiB2 preformed ingot obtained in S2, Si, Al-20%Fe, Al-60%Cu, Al-20%Mn, Al-5%Cr, Al-3%B and Zn to melt at 740-760 DEG C, when the temperature is greater than or equal to 730 DEG C, adding Mg ingot, second stirring, refining, removing slag, and second casting.

[0027] The beneficial effects of the present application are:

[0028] 1. By precisely controlling the Ti / B ratio, the coarse TiAl3 (easy to become a source of corrosion and cracks) generated by excessive Ti and the AlB2 (damaging the seawater corrosion resistance) formed by excessive B are avoided from the source, and the uniform distribution of the TiB2 reinforcing phase does not destroy the continuity of the Al2O3 passivation film. Compared with the negative impact of traditional reinforcement technology on corrosion resistance, the aluminum matrix composite prepared by the present application can maintain high strength, long service life, and still maintain the excellent deep ocean environment corrosion resistance of Al-Mg-Mn aluminum alloy, perfectly adapting to the service requirements of lightweight ship equipment in harsh marine environments.

[0029] 2. The step-by-step process solves the problems of TiB2 volume fraction deviation and harmful phase (TiAl3, AlB2) generation caused by reaction parameter fluctuation in traditional in-situ technology through the synergistic mechanism of "double salt reaction laying foundation and dynamic compensation of intermediate alloy", the TiB2 core reaction is completed in the preformed ingot stage, and the reaction interference during secondary melting is reduced; the B element compensation mechanism avoids the damage of B burning loss to the stoichiometric ratio in the smelting process, ensures that the TiB2 content in each batch of products is stable at 0.5-2.0%, and avoids the defects of the melt caused by excessive elements, such as pores and inclusions, greatly improving the repeatability of the process and the feasibility of engineering production.

[0030] 3. By element ratio and process synergy, the aluminum alloy profile and the preparation method thereof according to the present application make the composite material have the characteristics of high strength, long service life and corrosion resistance, and can be directly applied to deep ocean ship equipment, meeting the engineering requirements of lightweight and high reliability. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 The grain size chart of the composite material prepared in Example 1;

[0032] Figure 2 Grain size map of the composite material prepared for Comparative Example 3;

[0033] Figure 3 Microstructure map of the composite material prepared for Example 1;

[0034] Figure 4 Microstructure map of the composite material prepared for Comparative Example 4;

[0035] Figure 5 Hardness fluctuation map of the composite material prepared for Example 1 and Comparative Example 6. DETAILED DESCRIPTION

[0036] The endpoints of the ranges and any values claimed herein are not to be understood as being limited to the exact values recited as implicitly included within the range. The ranges are understood to be shorthand for describing each and every value that falls within the range. Any value within the range, including the endpoints, is intended to be a possible value unless otherwise indicated. Ranges can be expressed as being inclusive or exclusive of the values that fall within the range.

[0037] In the prior art, the existing Al-Mg-Mn aluminum-based composite material has limited carrying capacity due to insufficient matching of strength and plasticity, and the fatigue resistance of the ship part is reduced, and the existing reinforcement technology has a negative impact on the corrosion resistance of the material, so that the aluminum alloy composite material is difficult to have strength, fatigue resistance and corrosion resistance.

[0038] In the present application, the inventors have found that, by controlling the alloy composition and adjusting the processing technology, the performance of the Al-Mg-Mn aluminum-based composite material can meet the requirements, and the composite material has excellent strength, fatigue resistance and corrosion resistance.

[0039] To achieve this goal, the inventors have tried to optimize the composition of each component of the aluminum-based composite material and the processing technology, and the inventors have found that by using a specific composition of each component and TiB2 reinforced particles in combination with a casting process, the above-mentioned purpose can be achieved. Further, a specific homogenization process makes the performance of the composite material more excellent.

[0040] The first aspect of the present application provides a TiB2 reinforced Al-Mg-Mn aluminum-based composite material for deep ocean use, wherein the weight percentage of each component in the composite material is as follows:

[0041] The content of Si is 0.15-0.20%;

[0042] The content of Fe is 0.20-0.30%;

[0043] The content of Cu is 0.05-0.15%;

[0044] The Mn content is 0.6-0.8%;

[0045] The Mg content is 4.7-4.9%;

[0046] The Cr content is 0.05-0.25%;

[0047] The Zn content is 0.15-0.25%;

[0048] The Zr content is 0.08-0.12%;

[0049] The TiB2 content is 0.5-2.0%;

[0050] The content of other impurity elements is ≤0.05%;

[0051] The total content of other impurity elements is ≤0.15%;

[0052] The balance is Al.

[0053] In this invention, the efficiency, morphology and distribution of in-situ synthesized TiB2 reinforcing particles are controlled by optimizing the Ti / B stoichiometric ratio in the casting process, while avoiding process and performance problems caused by excessive Ti or B.

[0054] If Ti is excessive, the Ti / B ratio is too high, and unreacted Ti reacts with Al to form coarse TiAl3, which becomes a crack initiation point, reducing the material's toughness. Excess Ti may also consume Mg (a key element in Al-Mg-Mn), affecting the strengthening effect. By limiting the excess Ti, the damage to plasticity and workability caused by TiAl3 can be avoided, ensuring the dominant reinforcing role of TiB2. If B is excessive, the Ti / B ratio is too low, and free B reacts with Al to form AlB2, reducing the corrosion resistance of Al-Mg-Mn aluminum alloys, which is particularly crucial in aluminum-based composites used in marine environments. In addition, excessive B leads to an excessively rapid TiB2 formation rate, particle aggregation, and deterioration of material homogeneity. Excess B also increases melt viscosity, making it prone to porosity and inclusions during casting, thus reducing melt fluidity. By limiting the B content, the formation of AlB2 and the agglomeration of TiB2 can be prevented, ensuring the dispersed distribution of the reinforcing phase.

[0055] TiB2 is composited according to the weight fraction (0.5-2%) specified in this invention. If the TiB2 content is too low (<0.5%), the reinforcing effect is insufficient, and the improvement in mechanical properties is limited. The main function of TiB2 is dispersion strengthening and grain refinement strengthening. If the content is too low (<0.5%), the reinforcing effect is weak and cannot significantly improve strength and hardness. Al-Mg-Mn aluminum alloy itself is a non-heat-treatable strengthening alloy, relying on solid solution strengthening (Mg) and work hardening. When TiB2 is insufficient, the properties of the composite material are close to the matrix, losing its reinforcing significance. TiB2 can act as a heterogeneous nucleation core to inhibit grain growth. If the content is too low, the grain refinement effect is poor, and the as-cast structure may coarsen, affecting plasticity and fatigue strength. Mechanical properties: If the TiB2 content is too high (>2%), the particles will agglomerate, resulting in a decrease in mechanical properties. When the TiB2 content is too high, the particles are prone to agglomeration, forming local stress concentration points, which makes cracks easy to initiate and propagate at the agglomeration points, reducing toughness. Excessive TiB2 may destroy the continuity of the matrix, which will reduce the load-bearing capacity and reduce tensile strength. TiB2 increases the viscosity of the melt, reduces fluidity, and is prone to porosity and shrinkage, which increases casting defects. The seawater corrosion resistance of Al-Mg-Mn aluminum alloy is its core advantage, but excessive TiB2 will destroy the continuity of the passivation film (Al2O3), accelerate local corrosion, and the interface between agglomerated TiB2 and the matrix may become an active site for galvanic corrosion.

[0056] According to the present invention, the composite material has a yield strength of 229-270 MPa, a tensile strength of 391-435 MPa, an elongation after fracture of 14-16%, and a fatigue limit of 1×10⁻⁶ MPa at 201-227 MPa. 7 Weekly, the peeling corrosion level is EA grade.

[0057] The aluminum-based composite material provided by this invention is a high-strength, long-life, corrosion-resistant, lightweight aluminum-based composite material, suitable for the manufacture of deep-sea vessel equipment.

[0058] A second aspect of the present invention provides a method for preparing the above-mentioned TiB2-reinforced Al-Mg-Mn aluminum-based composite material for deep-sea applications, wherein the method comprises:

[0059] Melting and casting, homogenization treatment, extrusion, annealing treatment;

[0060] The casting process includes:

[0061] S1. Stir KBF4 and K2TiF6 at 20-30℃ for 2-4 min, and then dry them at 190-210℃ for 2.0-3.0 h to obtain a uniformly mixed salt.

[0062] S2. After melting pure Al, add the uniformly mixed salt obtained in S1 at 840℃-860℃ to react, remove slag, add Al2O3, keep warm for 5-15 minutes, and perform the first casting to obtain Al-TiB2 preform ingot.

[0063] During the casting process, the stoichiometric ratio of Ti / B is 1:1-1:2.

[0064] S3. The Al-TiB2 preform obtained in S2, Si, Al-20%Fe, Al-60%Cu, Al-20%Mn, Al-5%Cr, Al-3%B and Zn are heated to 740-760℃ until melted. When completely melted and the temperature is ≥730℃, Mg ingot is added. The mixture is stirred, refined, slag removed, and then cast.

[0065] In this invention, in step S2, pure Al and uniformly mixed salt are stirred using a graphite stirrer.

[0066] In this invention, Ti and B elements are introduced through a mixed salt of K2TiF6 and KBF4, with a Ti / B stoichiometric ratio of 1:1, 1:1.5, or 1:2 in the mixed salt, to prepare a 1% TiB2 preform; an aluminum-based composite material is prepared by mixing TiB2 with a weight fraction of 0.5-2.0%, while an Al-3%B master alloy is added according to a B / Ti stoichiometric ratio of 2.0-2.1.

[0067] Traditional reinforcement methods involve adding particles, where mechanically mixed TiB2 particles are physically bonded to the aluminum matrix. However, the interface is prone to debonding, becoming a preferred site for fatigue crack initiation, resulting in poor interfacial bonding. Uneven dispersion and particle agglomeration lead to localized stress concentration, reducing the material's strength and fatigue resistance. Furthermore, added particles may introduce oxides or impurities, impairing the matrix's corrosion resistance.

[0068] Existing in-situ generation techniques can lead to the formation of TiB2, which is prone to coarsening or agglomeration, affecting the reinforcing effect. The morphology and size of TiB2 are uncontrollable. An improper Ti / B ratio can generate TiAl3 (Ti excess) or AlB3 (B excess), reducing mechanical properties and corrosion resistance. Fluctuations in melting temperature and reaction time can cause inconsistent TiB2 weight fraction, resulting in poor process stability.

[0069] In this invention, a stepwise smelting process is used to react pure Al with salts to generate TiB2, avoiding interference from Mg and Mn elements in the Al-Mg-Mn alloy with the in-situ reaction. The Al-TiB2 pre-ingot is fused with the Al-Mg-Mn matrix and the Al-3B master alloy to dynamically compensate for the loss of B element, ensuring that the final Ti / B ratio is still within the range of 1:1-1:2, avoiding the formation of TiAl3 or AlB3, while avoiding the defects of traditional processes, resulting in a clean and uncontaminated interface, which is significantly better than the physical bonding of added particles.

[0070] In this invention, the reaction processes and products with different Ti / B stoichiometric ratios are as follows:

[0071] (1) When the stoichiometric ratio of Ti / B in the mixed salt is 1:1:

[0072] 6K2TiF6+6KBF4+11Al+3AlB2=2K3AlF6+12KAlF4+6TiB2

[0073] (2) When the stoichiometric ratio of Ti / B in the mixed salt is 1:1.5:

[0074] 12K2TiF6+18KBF4+31Al+3AlB2=4K3AlF6+30KAlF4+6TiB2

[0075] (3) When the stoichiometric ratio of Ti / B in the mixed salt is 1:2:

[0076] 3K2TiF6+6KBF4+10Al=K3AlF6+9KAlF4+3TiB2

[0077] According to the present invention, in S2, the reaction conditions include: performing a first stirring, the first stirring temperature being 740-760°C, and the first stirring time being 3-7 min.

[0078] According to the present invention, in S2, the conditions for the first casting include: the first casting melting temperature is 740-760°C, and the first casting pouring temperature is 730-740°C.

[0079] According to the present invention, in S3, the refining conditions include: a refining temperature of 730-750°C and a refining time of 5-15 min.

[0080] According to the present invention, in S3, the conditions for the second casting include: the second casting melting temperature is 740-760°C, and the second casting pouring temperature is 730-740°C.

[0081] In this invention, the second stirring step in S3 is not particularly limited; it is sufficient to mix the mixture evenly.

[0082] According to the present invention, the homogenization treatment conditions include: a first stage temperature of 315-325℃ and a first stage time of 4-6h; a second stage temperature of 415-425℃ and a second stage time of 2-3h; a third stage temperature of 483-487℃ and a third stage time of 8-10h; followed by stepped cooling.

[0083] TiB2 / Al-Mg-Mn aluminum matrix composites contain various segregated phases with significantly different properties (such as Mg2Si, Al6(Fe,Mn), and TiAl3), with vastly different dissolution temperatures and diffusion rates. Low-melting-point phases require pre-dissolution, high-melting-point phases require high-temperature refinement, and brittle phases require dispersion. Single-stage homogenization or other multi-stage homogenization methods are difficult to balance. The uniform distribution of Mg, Mn, and Cr elements in Al-Mg-Mn aluminum alloys directly affects strength and corrosion resistance. Single-stage homogenization is difficult to match their diffusion characteristics, resulting in low diffusion efficiency of alloying elements and uneven distribution of key elements. Single-stage homogenization cannot coordinate the interfacial state of the TiB2 reinforcing phase, which can easily lead to TiB2 agglomeration. If the temperature is not properly controlled (e.g., fluctuations exceeding 5°C), it may also trigger interfacial reactions between TiB2 and the matrix, such as generating brittle phases, weakening the interfacial bonding strength, and making the reinforcing phase a "harmful phase."

[0084] In this invention, the first stage promotes the pre-dissolution of Mg2Si and Al6(Fe,Mn) phases, solving the problem of insufficient pre-dissolution of low-melting-point phases. Mg2Si, the brittle phase of Mg and Si, has a melting point of about 450°C. If it and the fine Al6(Fe,Mn) phase are directly exposed to high temperatures, they will remain at the grain boundaries due to insufficient diffusion, forming a "brittle band". The specific low-temperature pre-dissolution in the first stage allows these low-melting-point phases to dissolve slowly and diffuse initially, avoiding coarsening or aggregation caused by excessive diffusion at high temperatures, thus laying the foundation for subsequent homogenization.

[0085] The second stage eliminates microsegregation bands and increases the diffusion coefficient of Mn, solving the problems of Mn segregation and inefficient diffusion of medium-melting-point phases. Mn is a key element for the corrosion resistance and strength of Al-Mg-Mn alloys, but its diffusion coefficient is low, making it difficult to diffuse from the segregation zone to the matrix at single-stage temperatures, easily forming microsegregation bands that become corrosion and crack sources. The second stage, with a specific medium temperature, increases the diffusion coefficient of Mn, accelerating the diffusion of Mn from the segregation zone to the matrix, eliminating the microsegregation bands of Mn, and promoting uniform Cr distribution, thus avoiding passivation film defects caused by insufficient local Cr content.

[0086] The third stage addresses the issues of coarsening and residue of harmful high-melting-point phases. Excessive Ti may generate the high-melting-point brittle TiAl3 phase and coarse Al6 (Fe,Mn) phase, which, if not adequately treated, can become crack initiation sources. The specific high-temperature stage of this invention ensures that these high-melting-point phases are fully dissolved or transformed into fine, dispersed phases, while avoiding overheating of the matrix due to excessive temperature. The solidus of Al-Mg-Mn aluminum alloy is approximately 600°C. Strict temperature control is required at high temperatures to prevent grain boundary weakening, ultimately achieving a uniform microstructure with "no residue of coarse, harmful phases".

[0087] Meanwhile, TiB2 is prone to agglomeration at high temperatures due to interfacial energy, which reduces the reinforcement efficiency. It is also prone to forming brittle phases through interfacial reactions with the matrix. The specific high temperature in the third stage ensures that the temperature is sufficient to promote the uniformity of the matrix composition, while strictly limiting the upper temperature limit to avoid exceeding the interfacial stability threshold between TiB2 and the Al matrix, thus preventing TiB2 particles from coarsening or agglomerating. At the same time, the low-temperature pre-dissolution and medium-temperature diffusion in the early stage have provided TiB2 with a "uniformly distributed matrix environment", avoiding its local enrichment in the segregation zone.

[0088] According to the present invention, the conditions for the stepped cooling include: cooling to 390-410°C at a rate of 4-6°C / min, then cooling to 290-310°C at a rate of 8-12°C / min, and then cooling to 20-30°C at a rate of 14-16°C / min.

[0089] In this invention, the gradient rate of stepped cooling can control the uniform precipitation of the second phase. The slow cooling in the high-temperature section allows the elements to diffuse fully and precipitate uniformly in small size. The accelerated cooling in the low-temperature section inhibits further coarsening of the second phase, ultimately forming a structure of "fine and dispersed second phase + uniform matrix", achieving a match between high strength and good plasticity.

[0090] After single-stage homogenization, the cast rod is prone to internal stress due to temperature gradient, which can lead to cracking during subsequent processing and deformation during service due to stress release. Specific three-stage homogenization and stepped cooling can reduce thermal stress during the heating stage, gradually release thermal stress during the cooling stage, avoid interface debonding or matrix microcracks caused by stress concentration, and improve the material's processing yield.

[0091] According to the present invention, the extrusion conditions include: heating the homogenized casting rod to 420-460°C, heating the die to 450-480°C, extruding, extrusion speed of 0.5-1.5 m / min, and quenching by water mist.

[0092] According to the present invention, the annealing conditions include: annealing temperature of 340-360℃, holding time of 1-2h, and air cooling to 20-30℃.

[0093] In this invention, stress relief, partial recrystallization, and β(Al3Mg2) phase optimization enable Al-Mg-Mn aluminum matrix composite extruded profiles to achieve more stable dimensional accuracy, reduce subsequent processing deformation, and exhibit good strength and higher corrosion resistance.

[0094] Test methods

[0095] The room temperature tensile mechanical properties were tested in accordance with GB / T 228.1-2021 ≪Metallic materials, tensile testing - Part 1: Room temperature test method≫, and the testing equipment was AG-X 100kN electronic universal testing machine.

[0096] The exfoliation corrosion test was conducted in accordance with GB / T 22639-2008 "Test Method for Exfoliation Corrosion of Aluminum Alloy Processed Products".

[0097] Fatigue performance testing was conducted in accordance with GB / T 3075-2008 "Method for controlling axial force in fatigue testing of MOD metallic materials".

[0098] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Obviously, the embodiments described herein are only some embodiments of the present invention and are not intended to limit the present invention. All other embodiments implemented by those skilled in the art based on the embodiments of the present invention without creative improvements are within the protection scope of the present invention.

[0099] Example 1

[0100] A. Casting: Prepare Al-Mg-Mn aluminum matrix composite material raw materials according to the following weight ratios: Si: 0.18%, Fe: 0.25%, Cu: 0.1%, Mn: 0.7%, Mg: 4.8%, Cr: 0.15%, Zn: 0.2%, Zr: 0.10%, Ti / B stoichiometric ratio 1:1, TiB2 weight fraction: 2.0%, individual impurity element content ≤0.05%, total impurity element content ≤0.15%, balance Al,

[0101] S1. Stir KBF4 and K2TiF6 at 25°C for 3 min and then dry them at 200°C for 2.5 h to obtain a uniformly mixed salt.

[0102] S2. After melting pure Al, add the uniformly mixed salt obtained in S1 at 850℃, stir with a graphite stirrer at 750℃ for 5 minutes, remove slag, add Al2O3, keep warm for 10 minutes, melt at 750℃, cast at 735℃, and cast to obtain Al-TiB2 preforms.

[0103] S3. The Al-TiB2 preform obtained in S2, Si, Al-20%Fe, Al-60%Cu, Al-20%Mn, Al-5%Cr, Al-3%B and Zn are heated to 750℃ until melted. When completely melted and the temperature is ≥730℃, Mg ingot is added, stirred, refined at 740℃ for 10min, slag is removed, the melting temperature is 750℃, the casting temperature is 735℃, and casting is performed.

[0104] B. Homogenization treatment: The casting rod is homogenized using a process of 320℃×5h+420℃×3h+485℃×9h. The rod is cooled from 485℃ to 400℃ at a cooling rate of 5℃ / min, then from 400℃ to 300℃ at a cooling rate of 10℃ / min, and finally from 300℃ to 25℃ at a cooling rate of 15℃ / min.

[0105] C. Extrusion: The mold heating temperature is 470℃, the homogenized casting rod is heated to 450℃, and then extruded. The extrusion speed is 1.1m / min, and the quenching method is water mist.

[0106] D. Annealing treatment: The profile is annealed at a temperature of 340℃ for 1.5 hours and then air-cooled to 25℃.

[0107] Aluminum-based composite material A1 was prepared.

[0108] Example 2

[0109] Aluminum-based composite materials were prepared according to the processing method of Example 1, except that the Ti / B stoichiometric ratio was 1:1.5.

[0110] Aluminum-based composite material A2 was prepared.

[0111] Example 3

[0112] Aluminum-based composite materials were prepared according to the processing method of Example 1, except that the Ti / B stoichiometric ratio was 1:2.

[0113] Aluminum-based composite material A3 was prepared.

[0114] Example 4

[0115] Aluminum-based composite materials were prepared according to the processing method of Example 1, except that the weight fraction of TiB2 was 0.5%.

[0116] Aluminum-based composite material A4 was prepared.

[0117] Example 5

[0118] Aluminum-based composite materials were prepared according to the processing method of Example 1, with a TiB2 weight fraction of 1.0%.

[0119] Aluminum-based composite material A5 was prepared.

[0120] Example 6

[0121] Aluminum-based composite materials were prepared according to the processing method of Example 1, except that the cast rods were homogenized using a process of 315℃×4h+415℃×2h+483℃×8h.

[0122] Aluminum-based composite material A6 was prepared.

[0123] Example 7

[0124] Aluminum-based composite materials were prepared according to the processing method of Example 1, except that the cast rods were homogenized using a process of 325℃×6h+425℃×3h+487℃×10h.

[0125] Aluminum-based composite material A7 was prepared.

[0126] Example 8

[0127] The aluminum-based composite material was prepared according to the processing method of Example 1, except that it was cooled from 485°C to 400°C at a cooling rate of 4°C / min, then from 400°C to 300°C at a cooling rate of 8°C / min, and finally from 300°C to 20°C at a cooling rate of 14°C / min.

[0128] Aluminum-based composite material A8 was prepared.

[0129] Example 9

[0130] The aluminum-based composite material was prepared according to the processing method of Example 1, except that it was cooled from 485°C to 400°C at a cooling rate of 6°C / min, then from 400°C to 300°C at a cooling rate of 12°C / min, and finally from 300°C to 30°C at a cooling rate of 16°C / min.

[0131] Aluminum-based composite material A9 was prepared.

[0132] Comparative Example 1

[0133] Aluminum-based composite materials were prepared according to the processing method of Example 1, except that the Ti / B stoichiometric ratio was 1:0.8.

[0134] Aluminum-based composite material DA1 was prepared.

[0135] Comparative Example 2

[0136] Aluminum-based composite materials were prepared according to the processing method of Example 1, except that the Ti / B stoichiometric ratio was 1:2.2.

[0137] Aluminum-based composite material DA2 was prepared.

[0138] Comparative Example 3

[0139] Aluminum-based composite materials were prepared according to the processing method of Example 1, except that the weight fraction of TiB2 was 0.2%.

[0140] Aluminum-based composite material DA3 was prepared.

[0141] Comparative Example 4

[0142] Aluminum-based composite materials were prepared according to the processing method of Example 1, except that the weight fraction of TiB2 was 3%.

[0143] Aluminum-based composite material DA4 was prepared.

[0144] Comparative Example 5

[0145] Aluminum-based composite materials were prepared according to the processing method of Example 1, except that a conventional semi-continuous casting method was used to directly add mixed salts and intermediate alloys for melting and casting.

[0146] Aluminum-based composite material DA5 was prepared.

[0147] Comparative Example 6

[0148] Aluminum-based composite materials were prepared according to the processing method of Example 1, except that the cast rods were homogenized by a 500°C × 24h process and cooled by water mist.

[0149] Aluminum-based composite material DA6 was prepared.

[0150] Comparative Example 7

[0151] Aluminum-based composite materials were prepared according to the processing method of Example 1, except that the cast rods were homogenized using a process of 310℃×3h+410℃×1.5h+475℃×7h.

[0152] Aluminum-based composite material DA7 was prepared.

[0153] Comparative Example 8

[0154] Aluminum-based composite materials were prepared according to the processing method of Example 1, except that the cast rods were homogenized by a process of 330℃×7h+430℃×3.5h+490℃×11h.

[0155] Aluminum-based composite material A8 was prepared.

[0156] Comparative Example 9

[0157] The aluminum-based composite material was prepared according to the processing method of Example 1, except that it was cooled from 485°C to 400°C at a cooling rate of 3°C / min, then from 400°C to 300°C at a cooling rate of 7°C / min, and finally from 300°C to 20°C at a cooling rate of 13°C / min.

[0158] Aluminum-based composite material DA9 was prepared.

[0159] Comparative Example 10

[0160] The aluminum-based composite material was prepared according to the processing method of Example 1, except that it was cooled from 485°C to 400°C at a cooling rate of 7°C / min, then from 400°C to 300°C at a cooling rate of 13°C / min, and finally from 300°C to 20°C at a cooling rate of 17°C / min.

[0161] Aluminum-based composite material DA10 was prepared.

[0162] Performance tests were performed on A1-A9 and DA1-DA10, as shown in Table 1.

[0163] Table 1

[0164]

[0165] By comparing Examples 1-3 and Comparative Examples 1-2, it can be seen that when Ti / B = 1:0.8 < 1:1, unreacted Ti reacts with Al to form a coarse, brittle TiAl3 phase, which becomes a crack initiation source and reduces the toughness of the material. At the same time, excessive Ti consumes Mg, a key strengthening element in Al-Mg-Mn alloys, weakening the solid solution strengthening effect and leading to a decrease in the balance between strength and plasticity. When Ti / B = 1:2.2 > 1:2, excessive B reacts with Al to form the AlB2 phase, which damages the corrosion resistance of Al-Mg-Mn aluminum alloys, especially important for use in marine environments. Furthermore, excessive B accelerates the TiB2 formation rate, leading to particle agglomeration, deteriorating the uniformity of the microstructure, increasing melt viscosity, and causing defects such as porosity and inclusions, thus reducing mechanical properties and corrosion resistance. By precisely controlling the Ti / B ratio within the range of 1:1 to 1:2, the formation of harmful TiAl3 and AlB2 phases is avoided, ensuring that the TiB2 reinforcing phase is evenly distributed. This not only exerts the effects of fine grain strengthening and dispersion strengthening, but also does not disrupt the continuity of the Al2O3 passivation film, resulting in superior strength, plasticity, and corrosion resistance.

[0166] Comparing Examples 1, 4, and 5 with Comparative Examples 3-4, it can be seen that when the TiB2 content is below 0.5%, the strengthening effect is insufficient. The dispersion strengthening and grain refinement strengthening effects of TiB2 are weak, resulting in limited improvement in tensile strength and hardness; moreover, it cannot effectively act as a heterogeneous nucleation core, leading to poor grain refinement, coarsening of the as-cast structure, and consequently, poor fatigue resistance and plasticity. When the content is above 2%, the particles are prone to agglomeration, forming local stress concentration points, which significantly reduces toughness and makes cracks prone to propagate at the agglomeration sites; excessive particles disrupt the continuity of the matrix, resulting in a decrease in tensile strength; at the same time, it increases the viscosity of the melt, causing casting defects such as porosity and shrinkage, and also disrupts the continuity of the Al2O3 passivation film, deteriorating corrosion resistance. When the TiB2 content is in the range of 0.5-2.0%, it can exert a strengthening effect through dispersion, improving strength and hardness, and can also act as a nucleation core to refine grains, improving plasticity and fatigue resistance, without causing agglomeration or casting defects, thus exhibiting excellent and balanced comprehensive performance.

[0167] A comparison of Example 1 and Comparative Example 5 shows that direct addition reduces performance. The in-situ reaction occurs instantaneously, resulting in extremely high Ti and B concentrations in the reaction zone. The generated TiB2 particles are highly prone to collision, agglomeration, and growth. In a melt rich in alloying elements, the higher melt viscosity further exacerbates particle agglomeration and floating / sinking, leading to uneven microstructure. Localized stress concentrations occur at the agglomeration sites of TiB2 particles, significantly reducing the material's strength and fatigue limit. Simultaneously, the agglomerates also disrupt the continuity of the matrix.

[0168] Instruction manual attached Figure 1 This is a grain size diagram of the aluminum-based composite material prepared in Example 1. Figure 3 The image shows the grain size of the composite material prepared in Comparative Example 3, indicating that the TiB2 content is too low, which weakens grain refinement and fails to achieve a strengthening effect.

[0169] Instruction manual attached Figure 2 This is a microstructure diagram of the aluminum-based composite material prepared in Example 1. Figure 4 The image shows the microstructure of the composite material prepared in Comparative Example 4, illustrating that excessive TiB2 leads to particle agglomeration, which reduces the alloy's properties.

[0170] Comparisons of Examples 1, 6, 7, 8, and 9, and Comparative Examples 7, 8, 9, and 10, show that insufficient homogenization temperature / time leads to inadequate dissolution and diffusion of the low-melting-point phase, incomplete elimination of elemental segregation, and incomplete dissolution of the high-melting-point phase, resulting in suboptimal performance, particularly poor fatigue and corrosion resistance. Excessively high homogenization temperature / time may cause overheating, resulting in coarse grains, severe TiB2 agglomeration, coarsening of the second phase, and a sharp deterioration in plasticity, toughness, and strength. An excessively slow cooling rate, equivalent to prolonged high-temperature annealing, causes excessive growth of the strengthening phase, transforming it from a dispersed strengthening point into a crack initiation point that severs the matrix, severely impairing mechanical properties and significantly reducing strength and plasticity. An excessively fast cooling rate, akin to quenching, creates enormous internal stress, acting as a catalyst for fatigue cracks and potentially inhibiting the precipitation of beneficial strengthening phases, leading to unstable performance and poor fatigue performance and stress corrosion resistance.

[0171] Instruction manual attached Figure 5The figures show the hardness fluctuations of Example 1 and Comparative Example 6. Comparative Example 6 uses a "500℃×24h single-stage homogenization + water mist cooling" process. The single-stage long-term treatment cannot match the dissolution characteristics of different segregated phases. The low-melting-point phase is excessively coarsened, and the high-melting-point phase is not fully dissolved, leaving behind coarse and brittle phases. This results in poor uniformity of the material structure, which in turn increases hardness fluctuations. The three-stage process in Example 1 precisely controls the temperature to avoid overheating, while ensuring that the high-melting-point phase is fully dissolved. The step-by-step treatment achieves uniform diffusion of elements, and the step-cooling gradually releases internal stress, avoids cracks, eliminates segregation bands, and prevents local structural distortion caused by stress. This further ensures the consistency of the material's performance in different regions, and the TiB2 distribution is stable, with a significant reinforcing effect. Therefore, the overall performance is better.

[0172] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A TiB2-reinforced Al-Mg-Mn aluminum-based composite material for deep-sea applications, characterized in that, The components and their weight percentages in the composite material are as follows: The Si content is 0.15-0.20%; The Fe content is 0.20-0.30%; The Cu content is 0.05-0.15%; The Mn content is 0.6-0.8%; The Mg content is 4.7-4.9%; The Cr content is 0.05-0.25%; The Zn content is 0.15-0.25%; The Zr content is 0.08-0.12%; The TiB2 content is 0.5-2.0%; The content of other impurity elements is ≤0.05%; The total content of other impurity elements is ≤0.15%; The balance is Al.

2. The composite material according to claim 1, characterized in that, The composite material has a yield strength of 229-270 MPa, a tensile strength of 391-435 MPa, an elongation after fracture of 14-16%, and a fatigue limit of 201-227 MPa at 1×10⁻⁶ MPa. 7 Weekly, the peeling corrosion level is EA grade.

3. A method for preparing the TiB2-reinforced Al-Mg-Mn aluminum-based composite material for deep-sea applications as described in claim 1 or 2, characterized in that, The method includes: Melting and casting, homogenization treatment, extrusion, annealing treatment; The casting process includes: S1. Stir KBF4 and K2TiF6 at 20-30℃ for 2-4 min, and then dry them at 190-210℃ for 2.0-3.0 h to obtain a uniformly mixed salt. S2. After melting pure Al, add the uniformly mixed salt obtained in S1 at 840℃-860℃ to react, remove slag, add Al2O3, keep warm for 5-15 minutes, and perform the first casting to obtain Al-TiB2 preform ingot. During the casting process, the stoichiometric ratio of Ti / B is 1:1-1:

2. S3. The Al-TiB2 preform obtained in S2, Si, Al-20%Fe, Al-60%Cu, Al-20%Mn, Al-5%Cr, Al-3%B and Zn are heated to 740-760℃ until melted. When completely melted and the temperature is ≥730℃, Mg ingot is added. The mixture is stirred, refined, slag removed, and then cast.

4. The method according to claim 3, characterized in that, In S2, the reaction conditions include: performing a first stirring, with a first stirring temperature of 740-760℃ and a first stirring time of 3-7 min; The conditions for the first casting include: the first casting melting temperature is 740-760℃, and the first casting pouring temperature is 730-740℃.

5. The method according to claim 3, characterized in that, In S3, the refining conditions include: a refining temperature of 730-750℃ and a refining time of 5-15 minutes. The conditions for the second casting include: the melting temperature of the second casting is 740-760℃, and the casting temperature of the second casting is 730-740℃.

6. The method according to claim 3, characterized in that, The homogenization treatment conditions include: a first stage temperature of 315-325℃ for 4-6 hours, a second stage temperature of 415-425℃ for 2-3 hours, a third stage temperature of 483-487℃ for 8-10 hours, followed by stepped cooling.

7. The method according to claim 6, characterized in that, The stepped cooling conditions include: cooling to 390-410℃ at a rate of 4-6℃ / min, then cooling to 290-310℃ at a rate of 8-12℃ / min, and then cooling to 20-30℃ at a rate of 14-16℃ / min.

8. The method according to claim 5, characterized in that, The extrusion conditions include: heating the homogenized casting rod to 420-460℃, heating the die to 450-480℃, extruding, extrusion speed of 0.5-1.5m / min, and quenching by water mist.

9. The method according to claim 5, characterized in that, The annealing conditions include: annealing temperature of 340-360℃, holding time of 1-2 hours, and air cooling to 20-30℃.

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