Titanium diboride reinforced aluminum-based composite material for die casting and preparation method of titanium diboride reinforced aluminum-based composite material

Abstract

The invention discloses a titanium diboride reinforced aluminum-based composite material for die casting and a preparation method of the titanium diboride reinforced aluminum-based composite material. The titanium diboride reinforced aluminum-based composite material comprises the following components in percentage by mass: 0.1-10.0% of Mg; 0.1% to 10.0% of Si; mn: 0.5%-0.7%; 0.1% to 3.0% of TiB2; filt; 0.15% by weight; 0.02% to 0.2% of Ti; 0.01% to 0.1% of V; the preparation method comprises the steps of pretreatment, smelting, slag and gas removal and pressure casting. By adding V and Ti elements, a coated D022-Al3 (Ti, V) phase is formed on the surfaces of titanium diboride particles, the wettability of the particle surfaces to an aluminum melt is optimized, interface formation dynamics is effectively controlled in combination with the die-casting cooling rate, and it is ensured that the titanium diboride particles are evenly dispersed in an aluminum alloy matrix, so that the strength and ductility of the material are greatly improved, and the mechanical property requirements of die castings are met.

Description

Technical Field

[0001] The invention belongs to the technical field of metal materials, and in particular relates to a titanium diboride reinforced aluminum-based composite material for die casting and a preparation method thereof. Background Art

[0002] With the rapid development of the new energy vehicle industry, lightweighting of the vehicle body has become one of the key strategies to improve endurance and reduce energy consumption. In this context, aluminum alloy materials are widely used in the manufacture of automotive structural parts due to their low density, high specific strength, high specific stiffness and excellent corrosion resistance, especially in the weight reduction effect of components such as beams and inner door panels. At the same time, with the development of large-scale integrated die-casting technology, the manufacturing of large thin-walled aluminum alloy parts has gradually developed in the direction of efficiency, complexity and integration. However, since the die-casting process usually requires subsequent heat treatment to improve the mechanical properties of the material, it often causes defects such as deformation and surface blistering of large and complex thin-walled parts, thereby affecting production efficiency and increasing manufacturing costs. Therefore, how to improve the comprehensive performance of cast aluminum alloys without the need for heat treatment has become a topic of widespread concern in the industry.

[0003] In order to achieve high strength and high toughness of the material in the cast state, titanium diboride (TiB2) particles are introduced as a reinforcing phase in the design of composite materials. TiB2 not only has high hardness and wear resistance, but its good compatibility with the aluminum matrix also makes it an ideal reinforcing material. However, the dispersion of TiB2 particles in the aluminum alloy melt directly determines its strengthening effect. If the dispersion is uneven, it is easy to cause local stress concentration and weaken its comprehensive mechanical properties. Especially in complex die-casting processes, TiB2 particles often agglomerate due to unfavorable factors such as high density and high specific surface energy, making it difficult to achieve ideal uniform distribution.

[0004] Therefore, developing an effective TiB2 particle dispersion method to ensure its uniform distribution in the aluminum matrix has become an important technical means to improve the mechanical properties of die-cast aluminum-based composite materials. By introducing a low mismatch interface phase between the aluminum matrix and TiB2, it helps to reduce the interface mismatch and enhance the wettability of TiB2 to the melt. This technology not only helps to improve the tensile strength, yield strength and toughness of the material, but also provides superior material support for lightweight automotive design, greatly meeting the performance requirements of complex thin-walled die castings in practical applications. Summary of the invention

[0005] In view of the problem in the prior art that the uneven dispersion of TiB2 particles in aluminum-based composite materials leads to poor mechanical properties, the main purpose of the present invention is to provide a titanium diboride reinforced aluminum-based composite material for die casting, in which the TiB2 particles are evenly and stably distributed in the aluminum alloy matrix, thereby greatly improving the comprehensive mechanical properties of the composite material and meeting the requirements of complex die-casting parts for strength and toughness.

[0006] Another object of the present invention is to provide a method for preparing the titanium diboride reinforced aluminum-based composite material for die casting, thereby improving its reinforcement effect in die-casting aluminum alloy by optimizing the dispersion effect of TiB2 particles.

[0007] To achieve the above object, the present invention adopts the following technical solution:

[0008] The present invention provides a titanium diboride reinforced aluminum-based composite material for die casting, and its components are as follows in terms of mass percentage:

[0009] Mg: 0.1%-10.0%; Si: 0.1%-10.0%; Mn: 0.5%-0.7%; TiB2: 0.1%-3.0%; Fe<0.15%; Ti: 0.02%-0.2%; V: 0.01%-0.1%; the total amount of other impurities ≤0.4%, the balance is Al.

[0010] Preferably, the mass ratio of Mg to Si is 2-3:1, and the total content of Mg and Si is less than 15%.

[0011] Preferably, Mg is added in the form of commercially pure Mg (>99.9%).

[0012] Preferably, Si, Mn, Ti, V and TiB2 are added in the form of Al-Si master alloy, Al-Mn master alloy, Al-Ti master alloy, Al-V master alloy and Al-TiB2 masterbatch, respectively.

[0013] Preferably, the mass ratio of Ti to V is 2:1, and the mass ratio of Ti to TiB2 is 1:4-6.

[0014] According to the performance test and microstructure analysis of die-casting alloys, the principles and advantages of the above component content range are as follows:

[0015] (1) Since Ti and V have a certain solid solubility in aluminum, when the Ti and V contents are too low, Ti and V are all trapped in the matrix in the form of solid solution atoms; when the Ti and V contents are greater than 0.02% and 0.01%, respectively, Al3Ti and Al3V phases can be formed in the matrix, which can serve as the interface phases between the matrix aluminum and titanium diboride; when the Ti and V contents are greater than 0.2% and 0.1%, respectively, the dissolution temperature of Al3Ti and Al3V in the aluminum melt is higher than the melting temperature (760°C), resulting in the presence of incompletely dissolved Al3Ti and Al3V phases in the melt; in the subsequent solidification, Ti and V preferentially adsorb and grow on these phases, and thus cannot nucleate and grow on the interface between aluminum and titanium diboride.

[0016] (2) When the Ti and V contents are within the above range, the mass ratio of Ti and V is 2:1, and the mass ratio of Ti and TiB2 is 1:4-6. When the mass ratio of Ti and V is 2:1, Ti and V synergistically precipitate the Al3 (Ti, V) phase. At this time, at the same total content, the precipitation driving force of Al3 (Ti, V) is the largest, which is conducive to the formation of the Al3 (Ti, V) interface phase. In addition, when the ratio of Ti to TiB2 is too large, the size of the Al3 (Ti, V) interface phase coated on the TiB2 surface is too large, reducing the strengthening effect of the fine TiB2. When the ratio of Ti to TiB2 is too small, it is impossible to achieve complete coating of the TiB2 surface with Al3 (Ti, V), thereby limiting the improvement in dispersibility.

[0017] (3) The mass ratio of Ti and TiB2 is coordinated with the cooling rate. When the cooling rate is slow (~200℃ / s), the optimal mass ratio of Ti and TiB2 is 1:6. When the cooling rate is fast (~1000℃ / s), the solute interception effect of the aluminum matrix on Ti and V is enhanced, resulting in a decrease in the fraction of the Al3 (Ti, V) interface phase at the same addition amount, and the optimal mass ratio of Ti and TiB2 is 1:4.

[0018] The present invention also provides a method for preparing a titanium diboride reinforced aluminum-based composite material for die casting, comprising the following steps:

[0019] (1) preheating the die casting mold and coating the mold surface with a boron nitride protective coating, and placing the weighed raw materials in a resistance furnace for drying to remove moisture from the raw materials;

[0020] (2) pure aluminum and aluminum-silicon master alloy are added to the crucible in the resistance furnace in sequence, the temperature is raised to 760°C, and the temperature is maintained until all raw materials are completely melted; then TiB2 masterbatch is added and the temperature is continued to be kept; then the melt is cooled and pure magnesium is added; to ensure that the magnesium is completely dissolved and the composition is uniform, the melt is stirred with a stirrer;

[0021] (3) Use rotary jet refining equipment to blow high-purity argon gas from the bottom of the melt to fully remove impurities and gases in the melt;

[0022] (4) Die casting is performed and the casting is cooled to room temperature in air.

[0023] Preferably, in step (1), the mold preheating temperature is 180-220°C, the raw material drying temperature is 200°C, and the insulation time is 2h.

[0024] Preferably, in step (2), before adding pure magnesium, the melt temperature is cooled to 735-745° C., the stirring rate is not less than 250 rpm, and the stirring time is not less than 10 min; and the temperature is kept warm for 10 minutes.

[0025] Preferably, in step (3), the gas flow rate is 0.4-0.8m 3 / h.

[0026] Preferably, in step (4), the melt temperature before die-casting is controlled at 735-745°C, the mold temperature is controlled at 195-205°C, the injection speed is 0.8-1.2 m / s, and the casting pressure is 80-120 MPa.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] (1) In traditional aluminum-based titanium diboride composite materials, the mismatch between aluminum and TiB2 is about 5%, resulting in poor wettability of TiB2 to Al melt, which is then repelled to form clusters between dendrites. However, the present invention adds Ti and V to form an Al3 (Ti, V) interface phase on the TiB2 surface through a peritectic reaction before the primary aluminum phase is formed, which covers the TiB2 surface. Since the mismatch between Al3 (Ti, V) and the aluminum matrix is ​​about 1%, the energy barrier for aluminum nucleation on the TiB2 surface is significantly reduced, thereby enhancing the wettability of TiB2 to Al melt and promoting the dispersion of TiB2.

[0029] (2) The titanium diboride reinforced aluminum-based composite material for die casting prepared by the present invention has excellent properties in the cast state, such as a yield strength of 140-180 MPa, a tensile strength of 240-320 MPa, and an elongation of 8%-12%, which exceeds the traditional die-casting aluminum alloy. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is the cross-sectional metallographic structure diagram of the die-cast sample in Comparative Example 1.

[0031] Figure 2 This is the cross-sectional metallographic structure diagram of the die-cast sample in Comparative Example 2.

[0032] Figure 3 This is the cross-sectional metallographic structure diagram of the die-cast sample in Example 1.

[0033] Figure 4 This is the cross-sectional metallographic structure diagram of the die-cast sample in Example 2. DETAILED DESCRIPTION

[0034] In order to more fully understand and demonstrate the technical solutions, purposes and advantages of the present invention, the technical effects produced by the present invention are further described in detail and completely in conjunction with specific embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, not all. It should be pointed out that for those of ordinary skill in the art, other embodiments obtained without departing from the concept of the present invention all belong to the protection scope of the present invention.

[0035] Comparative Example 1

[0036] This comparative example proposes a titanium diboride reinforced aluminum-based composite material for die casting, the weight percentage of each component is: Si: 7.0%; Mn: 0.6%; Mg: 0.4%; TiB2: 1%; Fe: 0.1%; the total amount of other impurities is 0.2%, and the balance is Al.

[0037] The preparation method of the titanium diboride reinforced aluminum-based composite material for die casting is as follows:

[0038] (1) Pretreatment: Heat the die casting mold to 200°C, apply a boron nitride coating on the mold surface, place the weighed raw materials in a 200°C resistance furnace for 2 hours, and perform drying and dehumidification treatment.

[0039] (2) Melting: Add pure aluminum and aluminum-silicon master alloy to a resistance furnace crucible, raise the temperature to 760°C and keep warm until the raw materials are completely melted; add TiB2 masterbatch and keep warm for 10 minutes; lower the melt temperature to 740°C and add pure magnesium; use a stirrer to stir the melt at 300 rpm for 10 minutes to ensure that Mg is completely dissolved and the composition is uniform.

[0040] (3) Slag removal and degassing: Use a rotary jet refiner to blow high-purity argon gas from the bottom of the melt, with a gas flow rate of 0.6m 3 / h, manual slag removal is carried out every 10 minutes of blowing, and the total blowing time is 30 minutes.

[0041] (4) Die casting: The melt temperature is controlled at 740±5℃, the mold temperature is controlled at 200±5℃ for die casting, the injection speed is 1m / s, the casting pressure is 100MPa, and the die casting is cooled to room temperature in air. The mold used in the production process is a standard rod-shaped tensile specimen.

[0042] Comparative Example 2

[0043] This comparative example proposes a titanium diboride reinforced aluminum-based composite material for die casting, the weight percentage of each component is: Mg: 5.4%; Si: 2.1%; Mn: 0.6%; TiB2: 2%; Fe: 0.1%; the total amount of other impurities is 0.2%, and the balance is Al.

[0044] The preparation method of the titanium diboride reinforced aluminum-based composite material for die casting is as follows:

[0045] (1) Pretreatment: Heat the die casting mold to 200°C and apply a boron nitride coating on the mold surface. Place the weighed raw materials in a 200°C resistance furnace for 2 hours for drying and dehumidification.

[0046] (2) Melting: Add pure aluminum and aluminum-silicon master alloy to a resistance furnace crucible, raise the temperature to 760°C and keep warm until the raw materials are completely melted; add TiB2 masterbatch and keep warm for 10 minutes; lower the melt temperature to 740°C and add pure magnesium; use a stirrer to stir the melt at 300 rpm for 10 minutes to ensure that Mg is completely dissolved and the composition is uniform.

[0047] (3) Slag removal and degassing: Use a rotary jet refiner to blow high-purity argon gas from the bottom of the melt, with a gas flow rate of 0.6m 3 / h, manual slag removal is carried out every 10 minutes of blowing, and the total blowing time is 30 minutes.

[0048] (4) Die casting: The melt temperature is controlled at 740±5℃, the mold temperature is controlled at 200±5℃ for die casting, the injection speed is 1m / s, the casting pressure is 100MPa, and the die casting is cooled to room temperature in air. The mold used in the production process is a standard rod-shaped tensile specimen.

[0049] Example 1

[0050] This comparative example proposes a titanium diboride reinforced aluminum-based composite material for die casting, the weight percentage of each component is: Si: 7.0%; Mn: 0.6%; Mg: 0.4%; TiB2: 1%; Fe: 0.1%; the total amount of other impurities is 0.2%, and the balance is Al.

[0051] The preparation method of the titanium diboride reinforced aluminum-based composite material for die casting is as follows:

[0052] (1) Pretreatment: Heat the die casting mold to 200°C, apply a boron nitride coating on the mold surface, place the weighed raw materials in a 200°C resistance furnace for 2 hours, and perform drying and dehumidification treatment.

[0053] (2) Melting: Add pure aluminum and aluminum-silicon master alloy to the crucible of the resistance furnace, raise the temperature to 760°C and keep it warm until the raw materials are completely melted; add TiB2 masterbatch and keep it warm for 10 minutes. Lower the melt temperature to 740°C and add pure magnesium; use a stirrer to stir the melt at 300 rpm for 10 minutes to ensure that Mg is completely dissolved and the composition is uniform.

[0054] (3) Slag removal and degassing: Use a rotary jet refiner to blow high-purity argon gas from the bottom of the melt, with a gas flow rate of 0.6m 3 / h, manual slag removal is carried out every 10 minutes of blowing, and the total blowing time is 30 minutes.

[0055] (4) Die casting: The melt temperature is controlled at 740±5℃, the mold temperature is controlled at 200±5℃ for die casting, the injection speed is 1m / s, the casting pressure is 100MPa, and the die casting is cooled to room temperature in air. The mold used in the production process is a standard rod-shaped tensile specimen.

[0056] Example 2

[0057] This comparative example proposes a titanium diboride reinforced aluminum-based composite material for die casting, the weight percentage of each component is: Mg: 5.4%; Si: 2.1%; Mn: 0.6%; TiB2: 2%; Fe: 0.1%; the total amount of other impurities is 0.2%, and the balance is Al.

[0058] The preparation method of the titanium diboride reinforced aluminum-based composite material for die casting is as follows:

[0059] (1) Pretreatment: Heat the die casting mold to 200°C and apply a boron nitride coating on the mold surface. Place the weighed raw materials in a 200°C resistance furnace for 2 hours for drying and dehumidification.

[0060] (2) Melting: Add pure aluminum and aluminum-silicon master alloy to the crucible of the resistance furnace, raise the temperature to 760°C and keep it warm until the raw materials are completely melted; add TiB2 masterbatch and keep it warm for 10 minutes. Lower the melt temperature to 740°C and add pure magnesium; use a stirrer to stir the melt at 300 rpm for 10 minutes to ensure that Mg is completely dissolved and the composition is uniform.

[0061] (3) Slag removal and degassing: Use a rotary jet refiner to blow high-purity argon gas from the bottom of the melt, with a gas flow rate of 0.6m 3 / h, manual slag removal is carried out every 10 minutes of blowing, and the total blowing time is 30 minutes.

[0062] (4) Die casting: The melt temperature is controlled at 740±5℃, the mold temperature is controlled at 200±5℃ for die casting, the injection speed is 1m / s, the casting pressure is 100MPa, and the die casting is cooled to room temperature in air. The mold used in the production process is a standard rod-shaped tensile specimen.

[0063] Table 1 (mass percentage %)

[0064] Group Mg Si Ti V Mn Fe <![CDATA[TiB2]]> Al Comparative Example 1 0.4 7 0 0 0.6 0.1 1 margin Comparative Example 2 5.4 2.1 0 0 0.6 0.1 2 margin Example 1 0.4 7 0.2 0.1 0.6 0.1 1 margin Example 2 5.4 2.1 0.2 0.1 0.6 0.1 2 margin

[0065] Table 2: Tensile microstructure and mechanical properties of die castings

[0066] Group <![CDATA[TiB2 cluster size / μm]]> Yield strength / MPa Tensile strength / MPa Elongation / % Comparative Example 1 15.2 144 264 9.5 Comparative Example 2 10.6 156 305 10.2 Example 1 9.5 152 278 10.9 Example 2 6.1 178 323 12.3

[0067] Table 2 shows the TiB2 cluster size and mechanical properties of the comparative example and the example. Compared with the comparative example 1, after adding Ti and V in the example 1, the TiB2 cluster size is reduced from 15.2 μm to 9.5 μm. Figure 1 and 2 As shown. In terms of mechanical properties, the yield strength is increased from 144MPa to 152MPa, the tensile strength is increased from 264MPa to 278MPa, and the elongation is increased from 9.5% to 10.9%. Compared with Comparative Example 2, after adding Ti and V, the size of the TiB2 clusters in Example 2 is reduced from 10.6μm to 6.1μm, as shown in FIG. Figure 3 and Figure 4 As shown. In terms of mechanical properties, the yield strength of Example 2 increased from 156MPa to 178MPa, the tensile strength increased from 305MPa to 323MPa, and the elongation increased from 10.2% to 12.3%. In summary, the addition of TiB2 can effectively improve the yield strength and tensile strength of the die casting, and can also improve the ductility of the material.

[0068] In summary, the present invention innovatively adds Ti and V elements to form a coated D0 22 -Al3 (Ti, V) phase, thereby enhancing the wettability of TiB2 to aluminum melt, successfully solving the problem of particle agglomeration in aluminum-based titanium diboride composite materials. The particle dispersion method and preparation method of the present invention provide a new path for improving the performance of die-cast aluminum alloys, especially meeting the strict requirements of large and complex die-castings on strength and plasticity.

[0069] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A titanium diboride reinforced aluminum-based composite material for die casting, characterized in that: The components are as follows by mass percentage: Mg: 0.1%-10.0%; Si: 0.1%-10.0%; Mn: 0.5%-0.7%; TiB2: 0.1%-3.0%; Fe<0.15%; Ti: 0.02%-0.2%; V: 0.01%-0.1%; the total amount of other impurities ≤0.4%, the balance is Al.

2. The titanium diboride reinforced aluminum-based composite material for die casting according to claim 1, characterized in that: The mass ratio of Mg to Si is 2-3:1, and the total content of Mg and Si is less than 15%.

3. The titanium diboride reinforced aluminum-based composite material for die casting according to claim 1, characterized in that: Mg was added in the form of commercially pure Mg (>99.9%).

4. The titanium diboride reinforced aluminum-based composite material for die casting according to claim 1, characterized in that: Si, Mn, Ti, V, and TiB2 are added in the form of Al-Si master alloy, Al-Mn master alloy, Al-Ti master alloy, Al-V master alloy, and Al-TiB2 masterbatch, respectively.

5. The titanium diboride reinforced aluminum-based composite material for die casting according to claim 1, characterized in that: The mass ratio of Ti to V is 2:1, and the mass ratio of Ti to TiB2 is 1:4-6.

6. A method for preparing a titanium diboride reinforced aluminum-based composite material for die casting, characterized in that: The following steps are involved: (1) preheating the die casting mold and coating the mold surface with a boron nitride protective coating, and placing the weighed raw materials in a resistance furnace for drying to remove moisture from the raw materials; (2) pure aluminum and aluminum-silicon master alloy are added to the crucible in the resistance furnace in sequence, the temperature is raised to 760°C, and the temperature is maintained until all raw materials are completely melted; then TiB2 masterbatch is added and the temperature is continued to be kept; then the melt is cooled and pure magnesium is added; to ensure that the magnesium is completely dissolved and the composition is uniform, the melt is stirred with a stirrer; (3) Use rotary jet refining equipment to blow high-purity argon gas from the bottom of the melt to fully remove impurities and gases in the melt; (4) Die casting is performed and the casting is cooled to room temperature in air.

7. The method for preparing the titanium diboride reinforced aluminum-based composite material for die casting according to claim 6, characterized in that: In step (1), the mold preheating temperature is 180-220°C, the raw material drying temperature is 200°C, and the insulation time is 2h.

8. The method for preparing the titanium diboride reinforced aluminum-based composite material for die casting according to claim 6, characterized in that: In step (2), before adding pure magnesium, the melt temperature is cooled to 735-745° C., the stirring rate is not less than 250 rpm, and the stirring time is not less than 10 min; and the temperature is kept warm for 10 minutes.

9. The method for preparing the titanium diboride reinforced aluminum-based composite material for die casting according to claim 6, characterized in that: In step (3), the gas flow rate is 0.4-0.8m 3 / h.

10. The method for preparing the titanium diboride reinforced aluminum-based composite material for die casting according to claim 6, characterized in that: In step (4), the melt temperature is controlled at 735-745°C before die casting, the mold temperature is controlled at 195-205°C, the injection speed is 0.8-1.2 m / s, and the casting pressure is 80-120 MPa.

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