Sc / Zr microalloying regulated TiB2 particle reinforced aluminum matrix composite and preparation method thereof

Abstract

The application discloses a kind of Sc / Zr microalloying regulation TiB2 Particulate Reinforced Aluminum Matrix Composites and preparation method thereof, the mass percentage of various elements in aluminum matrix composite is Zn:6%~7%, Mg:2%~3%, Cu:2%~3%, Ti:1.03%~3.78%, B:0.47%~1.72%, Sc:0.2%~0.5%, Zr:0.1%~0.2%, Fe:<0.10%, Si:<0.10%, K:<0.10%, the balance is Al and inevitable impurities.The beneficial effects of the application are: high proportion TiB2 can be realized by conventional casting process Uniform dispersion and improve heterogeneous nucleation rate by interface optimization;Compared with aluminum matrix composite without adding Sc / Zr, the average grain size is reduced by at least 40%, the tensile strength is increased by at least 55%, and the elongation is increased by at least 1 times.

Description

Technical Field

[0001] The present invention relates to the technical field of metal matrix composite materials, and in particular to a Sc / Zr microalloying-controlled TiB2 particle reinforced aluminum matrix composite material and a preparation method thereof. Background Art

[0002] Al-Zn-Mg-Cu (7xxx) alloys, due to their low density and ultrahigh strength, have become important structural materials in the aerospace and automotive industries. However, these alloys suffer from a wide solidification window, high hot cracking susceptibility, and poor melt fluidity, severely limiting their application in casting, welding, and even additive manufacturing. Grain refinement, through the formation of equiaxed grains, has become a key strategy to address these issues. Among them, TiB2 ceramic particles are the preferred heterogeneous nucleating agent due to their high melting point (3173 K), high elastic modulus (565 GPa), and high thermal stability. However, their industrial application faces two challenges: 1) TiB2 is prone to coarsening and agglomeration due to van der Waals forces and high surface energy, leading to grain boundary segregation and deterioration of plasticity; and 2) the lattice mismatch between TiB2 and α-Al is as high as 4.2%, resulting in a low heterogeneous nucleation rate.

[0003] Trace alloying elements (Ti, Zr, Sc, etc.) can improve the above problems to a certain extent, but they will also create new problems. For example, the formation of an Al3Ti transition layer by Ti can reduce the TiB2 / α-Al lattice mismatch from 4.2% to 0.09%. However, Si and Zr have a poisoning effect on TiB2, manifested as Si combining with Ti to form a Ti-Si covalent bond and Zr and Ti forming a Ti2Zr second phase, which destroys the above-mentioned interface coherence and weakens the grain refinement effect. For another example, Sc and Al form an Al3Sc phase, which can become an effective nucleation point, but Sc segregates on the TiB2 (0001) crystal plane and easily forms a (Ti,Sc)B2 phase with a larger lattice parameter than TiB2, that is, it has a poisoning effect on TiB2.

[0004] In addition, some researchers have improved the distribution of TiB2 by combining laser directed energy deposition or ultrasonic vibration, but the equipment cost is high and the process is complex, making it difficult to apply on a large scale.

[0005] In summary, the prior art has the following defects:

[0006] TiB2 coarsening and aggregation: High TiB2 content (≥ 2 wt.%) in traditional casting easily forms coarse spherical particles due to high surface energy and is prone to agglomeration, seriously deteriorating the performance of aluminum-based composites;

[0007] The lattice mismatch between TiB2 and α-Al is high (4.2%), resulting in a low heterogeneous nucleation rate and easy to induce stress concentration and crack initiation;

[0008] Single elements have toxic effects;

[0009] 4) Existing interface optimization methods rely on complex external fields and have high industrialization costs.

[0010] Therefore, it is urgent to develop a microalloying method that can achieve high-proportion uniform dispersion of TiB2 through conventional casting process and improve the heterogeneous nucleation rate through interface optimization. Summary of the Invention

[0011] The present invention provides a TiB2 particle reinforced aluminum-based composite material regulated by Sc / Zr microalloying and a preparation method thereof. The composite material can be realized in a conventional casting process through the coordinated design of Sc / Zr microalloying and process parameters, and has the advantages of simple operation and universal applicability.

[0012] A microalloying method can achieve uniform dispersion of high-proportion TiB2 through conventional casting processes and improve the heterogeneous nucleation rate through interface optimization; by adding Sc / Zr, the average grain size of aluminum-based composite materials is reduced by at least 40%, the tensile strength is increased by at least 55%, and the elongation is increased by at least 1 times compared with aluminum-based composite materials without Sc / Zr addition.

[0013] TiB2 grain refinement: The surface activity of Sc / Zr is used to reduce the surface energy of the melt, thereby reducing the critical nucleation size of TiB2, and ultimately forming a needle-like morphology with a submicron scale (average lateral size 100~350nm) or even nanoscale (10~50nm).

[0014] Construction of three-phase coherent interface: Through Sc / Zr microalloying, Al3(Sc,Zr) phase with L12 structure is in situ generated on the TiB2 surface, forming the α-Al / Al3(Sc,Zr) / TiB2 three-phase coherent interface:

[0015] Al3(Sc,Zr) has the following coherent interface relationship with α-Al and TiB2:

[0016] .

[0017] Poisoning effect suppression: Sc is preferentially adsorbed on high-index surfaces, while Zr promotes the formation of an Al3(Sc,Zr) phase with a core-shell structure. Sc / Zr achieves multi-dimensional diffusion, preventing Sc from segregating on low-index surfaces and producing a poisoning effect.

[0018] To achieve the above object, the present invention is implemented through the following technical solutions:

[0019] A Sc / Zr microalloying-controlled TiB2 particle reinforced aluminum matrix composite.

[0020] The mass percentages of various elements in the aluminum-based composite material are Zn: 6%~7%, Mg: 2%~3%, Cu: 2%~3%, Ti: 1.03%~3.78%, B: 0.47%~1.72%, Sc: 0.2%~0.5%, Zr: 0.1%~0.2%, Fe: <0.10%, Si: <0.10%, K: <0.10%, and the balance is Al and unavoidable impurities.

[0021] As a further description of this scheme,

[0022] The microstructure of the aluminum-based composite material consists of α-Al, MgZn2, Al3Ti, TiB2, S-Al2CuMg, T-AlMgZn, Al3Zr and Al3(Sc,Zr) phases.

[0023] As a further description of this scheme,

[0024] The TiB2 is in the shape of needles or short rods and is evenly distributed in the α-Al matrix and grain boundaries;

[0025] TiB2 is submicron-scale, with an average lateral size of 100–350 nm or even nanoscale (10–50 nm);

[0026] The Al3(Sc,Zr) phase has an L12 structure and has a coherent interface relationship with both α-Al and TiB2.

[0027] As a further description of this solution, the Al3(Sc,Zr) phase has a core-shell structure, with the core being rich in Zr and the shell being rich in Sc.

[0028] As a further description of this scheme, Al3(Sc,Zr) has the following coherent interface relationship with α-Al and TiB2:

[0029] .

[0030] A method for preparing a TiB2 particle reinforced aluminum matrix composite material regulated by Sc / Zr microalloying, comprising the following steps:

[0031] S1: pure Al is melted at 800-820 °C, and Al-5wt.%TiB2 master alloy, pure Zn, Al-50wt.%Cu master alloy, Al-10wt.%Zr master alloy, and Al-2wt.%Sc master alloy are added in sequence, and the temperature is kept for 30-60 min;

[0032] S2 is cooled to 740-760 °C, Al-50wt.%Mg master alloy is added, mechanically stirred for 15-30 min, and then kept warm for 20-40 min;

[0033] S3 was degassed with an argon degassing rod for 10-15 min, and then cast after slag removal. The casting temperature was controlled at 740-760℃.

[0034] As a further description of this scheme, in S1, Al-5wt.%TiB2 master alloy is prepared by in situ mixed salt method (K2TiF6+KBF4) with a reaction temperature of 830~850℃.

[0035] As a further description of this scheme, in S3, after casting, the material is cooled to room temperature at a rate of 30-50°C / min.

[0036] The method for preparing the particle-reinforced aluminum-based composite material of the present invention has the following beneficial effects:

[0037] 1) Microstructure Refinement: Sc / Zr microalloying reduces the average TiB2 grain size from 1 μm to submicron (100-350 nm) and even nanoscale (10-50 nm), effectively refining the TiB2 grain size. Furthermore, the TiB2 grain size and the formation of a coherent α-Al / Al3(Sc,Zr) / TiB2 three-phase interface contribute to a reduction in the average α-Al grain size by at least 40%.

[0038] 2) Performance improvement: Sc / Zr microalloying regulates the tensile strength of Al-Zn-Mg-Cu alloys containing a high proportion of TiB2, increasing their tensile strength by at least 55% and their elongation by at least 100%.

[0039] 3) Reduced process costs: Compared with improving TiB2 distribution by using laser directed energy deposition or ultrasonic vibration technology, the method of the present invention can be implemented using conventional casting processes, effectively reducing production costs and being suitable for mass production. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 In Example 1 of the present invention, scanning electron microscopy (SEM) and high-angle annular dark field-scanning transmission electron microscopy (HAADF-STEM) morphology of the AlZnMgCu-TiB2 aluminum-based composite material after adding Sc / Zr;

[0041] Figure 2 In Example 1 of the present invention, high resolution transmission electron microscopy (HRTEM) and Fourier transform (FFT) photographs of the AlZnMgCu-TiB2 aluminum-based composite material after adding Sc / Zr;

[0042] Figure 3 Engineering stress-strain curves of the AlZnMgCu-TiB2 aluminum-based composite material before and after Sc / Zr addition in Example 1 of the present invention and Comparative Example 1;

[0043] Figure 4 In the present application comparative example 1, SEM morphology of AlZnMgCu-TiB2 aluminum matrix composite without adding Sc / Zr. DETAILED DESCRIPTION

[0044] In order to make the purpose, technical scheme and advantages of the present application more clear, the following combines examples and the attached drawings to make a further explanation. Figures 1-4 Further explanation of the present application:

[0045] Example 1

[0046] Aluminum matrix composite composition: Al-6.5Zn-2.5Mg-2.5Zn-3.45Ti-1.56B-0.25Sc-0.20Zr (wt. %)

[0047] Preparation process:

[0048] Prepare Al-5wt.%TiB2 intermediate alloy by in-situ mixing salt method (K2TiF6+KBF4), the reaction temperature is 850℃; then prepare Al-50wt.%Cu intermediate alloy, Al-10wt.%Zr intermediate alloy, Al-2wt.%Sc intermediate alloy, Al-50wt.%Mg intermediate alloy in turn;

[0049] 2) melt pure Al at 800℃, add Al-5wt.%TiB2 intermediate alloy, pure Zn, Al-50wt.%Cu intermediate alloy, Al-10wt.%Zr intermediate alloy, Al-2wt.%Sc intermediate alloy in turn, and keep for 30 min;

[0050] Further, cool to 750℃, add Al-50wt.%Mg intermediate alloy, and keep for 20 min after mechanical stirring for 15 min;

[0051] Further, use argon degassing rod to degas for 10 min, and then pour and cast after slagging, with the pouring temperature controlled at 750℃, and then cooled to room temperature at a rate of 30℃ / min after pouring.

[0052] Microstructure and performance: AlZnMgCu-TiB2 aluminum matrix composite regulated by Sc / Zr micro-alloying does not appear coarse TiB2 particles, and TiB2 does not show obvious segregation phenomenon Figure 1 a) TiB2 morphology presents rod or needle shape, and the grain size presents sub-micron or even nanometer scale, such as Figure 1b. The average grain size of α-Al is about 24 μm. Through Sc / Zr microalloying, Al3(Sc,Zr) phase with L12 structure is in situ generated on the TiB2 surface, forming the α-Al / Al3(Sc,Zr) / TiB2 three-phase coherent interface ( Figure 2 After adding Sc / Zr, the tensile strength of AlZnMgCu-TiB2 aluminum matrix composite material is about 320MPa and the elongation is about 1.66% ( Figure 3 ).

[0053] Example 2

[0054] Adjustment: Based on Example 1, the Ti content was reduced to 1.4 wt.%, and the B content was reduced to 0.6 wt.%.

[0055] Results: TiB2 exhibited no segregation, exhibiting rod- or needle-like morphology. Its grain size was slightly larger than that of Example 1, but remained below the submicron scale. An Al3(Sc,Zr) phase with an L12 structure was formed, maintaining a coherent relationship with α-Al and TiB2. The average α-Al grain size was approximately 38 μm. The AlZnMgCu-TiB2 aluminum-based composite with the addition of Sc / Zr exhibited a tensile strength of approximately 298 MPa and an elongation of approximately 1.56%.

[0056] Example 3

[0057] Adjustment: Based on Example 1, the Sc content was reduced to 0.20 wt.%, and the Zr content was reduced to 0.15 wt.%.

[0058] Results: TiB2 exhibited no segregation, exhibiting rod- or needle-like morphology. Its grain size was slightly larger than that of Example 1, but remained below the submicron scale. An Al3(Sc,Zr) phase with an L12 structure was formed, maintaining a coherent relationship with α-Al and TiB2. The average grain size of the α-Al was approximately 32 μm. The tensile strength of the AlZnMgCu-TiB2 aluminum-based composite with the addition of Sc / Zr was approximately 305 MPa, and the elongation was approximately 1.60%.

[0059] Example 4

[0060] Adjustment: Based on Example 1, the casting temperature was lowered to 740°C and the cooling rate was increased to 40°C / min.

[0061] Results: The TiB2 morphology and size remained unchanged, and no segregation occurred. The average α-Al grain size was refined to 20 μm. An Al3(Sc,Zr) phase with an L12 structure was still formed, maintaining a coherent relationship with the α-Al and TiB2. The AlZnMgCu-TiB2 aluminum-based composite with the addition of Sc / Zr exhibited a tensile strength of approximately 340 MPa and an elongation of approximately 1.9%.

[0062] Comparative Example 1

[0063] Aluminum matrix composite composition: Al-6.5Zn-2.5Mg-2.5Zn-3.45Ti-1.56B (wt.%) (no Sc / Zr added)

[0064] Results: TiB2 showed coarse particles with an average size of about 1.5 μm and serious agglomeration. The average grain size of α-Al was about 48 μm ( Figure 4 The tensile strength of the AlZnMgCu-TiB2 aluminum matrix composite material without Sc / Zr addition is only about 205 MPa and the elongation is about 0.82% ( Figure 3 This strongly confirms the role of Sc / Zr microalloying in the continuous refinement and toughening of AlZnMgCu-TiB2 aluminum-based composites containing a high proportion of TiB2, solving the problem of dispersing high volume fraction ceramic reinforcement phases in aluminum alloys and providing an innovative solution for the low-cost manufacturing of large and complex aerospace components.

[0065] The above description is only a preferred embodiment of the present invention and does not limit the patent scope of the present invention. All equivalent transformations made using the present invention are within the scope of patent protection of the present invention.

Claims

1. A Sc / Zr microalloying regulated TiB2 particle reinforced aluminum matrix composite material, characterized in that: The mass percentages of various elements in the aluminum-based composite material are Zn: 6% to 7%, Mg: 2% to 3%, Cu: 2% to 3%, Ti: 1.03% to 3.78%, B: 0.47% to 1.72%, Sc: 0.2% to 0.5%, Zr: 0.1% to 0.2%, Fe: <0.10%, Si: <0.10%, K: <0.10%, and the balance is Al and unavoidable impurities; The microstructure of the aluminum-based composite material consists of α-Al, MgZn2, Al3Ti, TiB2, S-Al2CuMg, T-AlMgZn, Al3Zr and Al3(Sc,Zr) phases; The TiB2 is in the shape of needles or short rods and is evenly distributed in the α-Al matrix and grain boundaries; TiB2 is submicron-scale, with an average lateral size of 100 to 350 nm, or nanoscale of 10 to 50 nm; The Al3(Sc,Zr) phase has an L12 type structure and has a coherent interface relationship with both α-Al and TiB2.

2. The Sc / Zr microalloying controlled TiB2 particle reinforced aluminum matrix composite material according to claim 1, characterized in that: The Al3(Sc,Zr) phase has a core-shell structure, wherein the core is rich in Zr and the shell is rich in Sc.

3. The Sc / Zr microalloying controlled TiB2 particle reinforced aluminum matrix composite material according to claim 1, characterized in that: Al3(Sc,Zr) has the following coherent interface relationship with α-Al and TiB2:

4. A method for preparing a TiB2 particle reinforced aluminum matrix composite material regulated by Sc / Zr microalloying as claimed in claim 1, characterized in that: The method comprises the following preparation steps: S1: pure Al is melted at 800-820°C, and Al-5wt.% TiB2 master alloy, pure Zn, Al-50wt.% Cu master alloy, Al-10wt.% Zr master alloy, and Al-2wt.% Sc master alloy are added in sequence, and the temperature is kept for 30-60 minutes; S2 is cooled to 740-760°C, Al-50wt.% Mg master alloy is added, mechanically stirred for 15-30 minutes and then kept warm for 20-40 minutes; S3 uses an argon degassing rod to degas for 10 to 15 minutes, and is cast after slag removal. The casting temperature is controlled at 740 to 760°C.

5. The method for preparing the Sc / Zr microalloying-controlled TiB2 particle reinforced aluminum matrix composite material according to claim 4, characterized in that: In S1, Al-5wt.%TiB2 master alloy is prepared by in-situ mixed salt method (K2TiF6+KBF4) at a reaction temperature of 830-850°C.

6. The method for preparing the Sc / Zr microalloying-controlled TiB2 particle reinforced aluminum matrix composite material according to claim 4, characterized in that: In S3, after casting, the material is cooled to room temperature at a rate of 30 to 50°C / min.

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