High-toughness boron carbide composite material and preparation method thereof

Abstract

The invention discloses a high-toughness boron carbide composite material and a preparation method thereof, and belongs to the field of inorganic materials. The composite material is prepared from the following components in parts by mass: 92.5 to 97.5 parts of boron carbide micro powder, 1 to 5 parts of five-element high-entropy alloy, MnCoCrFeNi with the molar ratio of 3: 1: 1: 5: 0.2, 0.5 to 2 parts of nano SiC fiber with the diameter of 45 to 50nm and 0.05 to 0.1 part of sintering aid yttrium powder. The preparation method comprises the following steps: refining boron carbide coarse powder to 5 + / -0.5 mu m through high-energy ball milling; high-entropy alloy powder is prepared through a gas atomization method; ultrasonically dispersing the nanofibers and the matrix powder; carrying out two-stage spark plasma sintering; and carrying out hot isostatic pressing post-treatment. The high-entropy alloy inhibits brittle phases, the nanofibers are used for toughening, and gradient sintering is used for optimizing interface bonding, so that the fracture toughness of the material reaches 8.3-8.7 MPa.m < 1 / 2 >, the bending strength is 620-650 MPa, the density is 2.75-2.85 g / cm < 3 >, and the porosity is smaller than 0.1%. The material is suitable for bulletproof armor, aerospace and other high-performance fields.

Description

Technical Field

[0001] The invention belongs to the field of inorganic materials, and in particular relates to a high-toughness boron carbide composite material and a preparation method thereof. Background Art

[0002] Boron carbide (B4C) ceramics are widely used in bulletproof armor, aerospace materials, and high-temperature structural materials due to their high hardness, low density, excellent radiation resistance, and high temperature resistance. However, boron carbide ceramics also have some disadvantages that limit their application, mainly manifested in their intrinsic brittleness and low fracture toughness (usually 2-4 MPa·m 1 / 2 ). This brittleness makes boron carbide ceramics prone to fracture when subjected to impact or high stress, limiting its application performance under high impact loads.

[0003] In order to overcome the brittleness of boron carbide ceramics, researchers have proposed a variety of toughening methods in recent years. Traditional toughening techniques mainly improve the toughness of boron carbide ceramics by introducing metal phases (such as zirconium, titanium, nickel and other metals) or generating tough phases in situ. Common practices include adding metal powders to the boron carbide matrix to improve the mechanical properties of the material through the interaction between the metal and the ceramic matrix. However, excessive metal addition may cause the density of boron carbide ceramics to increase, or even generate brittle boride phases, thereby reducing the overall performance of the material.

[0004] In addition, nanofiber toughening has gradually attracted the attention of academia and industry. In particular, in the study of boron carbide-based composite materials, nanofibers such as SiC and Al2O3 are added to improve the crack deflection and bridging capabilities of the material, thereby improving the toughness of the material. This method can effectively reduce the expansion of cracks and improve the impact resistance of the material. However, the method of adding nanofibers alone still has the problem of uneven fiber dispersion, which may lead to poor interface bonding and affect the performance of the material.

[0005] In addition, the existing boron carbide ceramic sintering process is mostly carried out at a single sintering temperature and pressure, but these traditional processes often fail to take into account the densification and interface bonding problems of the material, resulting in a high porosity of boron carbide ceramics, which in turn affects its mechanical properties. In order to solve this problem, the gradient sintering process has gradually gained the attention of researchers. By controlling parameters such as temperature, pressure and holding time during the sintering process, the density and mechanical properties of the material can be optimized.

[0006] Although there are many toughening and modification methods, there is no research on the synergistic application of quinary high entropy alloys and nano-SiC fibers in a boron carbide matrix and optimization through a gradient sintering process. Existing technologies cannot completely solve the problems of low toughness, low strength and low density of boron carbide ceramics, so a new method is needed to achieve the excellent performance of boron carbide ceramic materials in high impact and high temperature environments.

[0007] Therefore, the present invention proposes a composite toughening scheme by introducing a five-element high entropy alloy and nano-SiC fibers, and combining it with a gradient sintering process, to significantly improve the toughness, strength and density of boron carbide-based composite materials, thereby overcoming the limitations of boron carbide ceramic materials in the prior art and promoting its application in a wider range of fields. Summary of the invention

[0008] In order to solve the technical problems existing in the above-mentioned background technology, the present invention relates to a high-toughness boron carbide-based composite material and a preparation method thereof, aiming to significantly improve the toughness, strength and density of boron carbide ceramics by adopting the synergistic toughening mechanism of five-element high entropy alloy and nano-SiC fiber in combination with a gradient sintering process, thereby overcoming the brittleness problem of boron carbide ceramic materials in the prior art and expanding its application in high-strength and high-temperature environments.

[0009] To achieve the above objectives, an object of the present invention is to provide a high-toughness boron carbide composite material, characterized in that it includes the following components, measured by mass: 1-5 parts of a quinary high entropy alloy, 0.5-2 parts of nano-SiC fibers, 92.5-97.5 parts of boron carbide powder, and 0.05-0.1 parts of a sintering aid.

[0010] Furthermore, the five-element high entropy alloy is a MnCoCrFeNi alloy with a molar ratio of Mn:Co:Cr:Fe:Ni=3:1:1:5:0.2); the high entropy alloy can effectively inhibit the formation of brittle phases in the boron carbide ceramic matrix and enhance the toughness of grain boundaries.

[0011] Furthermore, the nano-SiC fibers have an average diameter of 45-50 nm, which can improve the toughness of the material and prevent crack propagation through the mechanisms of crack bridging and pull-out toughening.

[0012] Furthermore, the sintering aid is yttrium powder, which can promote grain refinement during the sintering process and optimize the interface structure.

[0013] Another object of the present invention is to provide a method for preparing the high-toughness boron carbide composite material, which is characterized by comprising the following steps:

[0014] S1 ball milling: Boron carbide coarse powder (D50 = 50 μm) is subjected to high-energy ball milling for 48-72 hours to obtain boron carbide powder; high-energy ball milling breaks up coarse particles through mechanical force to reduce sintering activation energy.

[0015] Preparation of S2 alloy powder: Mn, Co, Cr, Fe and Ni are melted in the above molar ratio, atomized and powdered, and sieved through a 150-mesh sieve. Atomization and rapid cooling form a uniform solid solution to avoid component segregation.

[0016] S3 nanofiber dispersion: ultrasonically disperse SiC nanofiber, boron carbide powder, alloy powder and sintering aid in alcohol for 30-40 minutes.

[0017] S4 gradient sintering process: The first stage: 1580-1600℃, 25-30MPa, heat preservation for 5-10min. Low-temperature pre-sintering promotes the physical bonding between nanofibers and the matrix to avoid fiber damage at high temperature.

[0018] The second stage: 1890-1900℃, 45-50MPa, heat preservation for 15-20min. Under high temperature and high pressure, the alloy liquid phase (melting point ≈ 1450℃) wets the boron carbide grain boundary, fills the pores, and achieves densification (relative density ≥ 99.5%).

[0019] S5 hot isostatic pressing (HIP) post-treatment: 1780-1800℃, 198-200MPa argon environment, heat preservation for 2-3h. High-pressure argon eliminates residual closed pores (porosity <0.1%), homogenizes the grain boundary structure, and improves the interface bonding strength.

[0020] Furthermore, in step S1, the ball-to-material ratio of the high-energy ball milling is 12:1, the grinding balls are zirconia balls, the ball milling medium is alcohol, the rotation speed is 450 rpm, and the time is 72 h. After ball milling, the average particle size of the boron carbide is 5±0.5 μm.

[0021] Furthermore, in step S2, the molar ratio of Mn, Co, Cr, Fe and Ni is 3:1:1:5:0.2, the atomization pressure in the gas atomization powder making step is 5 MPa, and the protective gas is nitrogen.

[0022] Furthermore, in step S3, the surface of the silicon carbide fiber is treated with 3% silane coupling agent. The ultrasonic power is 200W.

[0023] Furthermore, in step S4, the heating rate of the first stage is 100° C. / min; and the heating rate of the second stage is 50° C. / min.

[0024] Furthermore, in step S5, the heating rate is 10° C. / min.

[0025] The present invention has the following technical effects

[0026] The present invention proposes to use five-element high entropy alloy and nano-SiC fiber in a boron carbide matrix in a coordinated manner. Through the synergistic toughening effect of the two, not only the formation of brittle phase is suppressed, but also the fracture toughness and strength of the material are significantly improved. A gradient sintering process is adopted to optimize the temperature, pressure and holding time during the sintering process, ensuring the densification and grain boundary strengthening of the material. The composite ceramic material of the present invention has significantly improved toughness and flexural strength while maintaining high hardness, providing a new technical route for the high-strength application of boron carbide-based materials. The high-toughness boron carbide-based composite material proposed in the present invention and its preparation method not only effectively overcome the brittleness problem of traditional boron carbide ceramics, but also have good industrial application prospects, especially in the fields of bulletproof armor, aerospace, nuclear energy protection and high-temperature structural materials. It has important application value. DETAILED DESCRIPTION

[0027] In order to better illustrate the purpose, technical solutions and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments. The present invention can be implemented in many different forms and should not be construed as being limited to the embodiments set forth herein. On the contrary, these embodiments are provided so that this disclosure will be thorough and complete, and the concept of the present invention will be fully conveyed to those skilled in the art, and the present invention will only be limited by the claims.

[0028] Example 1

[0029] Take 200g of coarse boron carbide powder (D50 = 50μm), and high-energy ball milling, the ball-to-material ratio of high-energy ball milling is 12:1, the grinding ball is a zirconium oxide ball, the ball milling medium is alcohol, the speed is 450rpm, the time is 72h, and the average particle size of boron carbide is 5±0.5μm. Boil it at 80℃ for 1h with concentrated hydrochloric acid, then wash it with water to pH=7, and dry it at 80℃. According to Mn:Co:Cr:Fe:Ni=3:1:1:5:0.2, high-frequency induction melting, melting temperature 1600℃, nitrogen atomization powder, sieve 150 mesh. According to the weight ratio of 1 part of five-element high entropy alloy, 0.5 part of nano-SiC fiber, 92.5 parts of boron carbide powder, 0.05 parts of sintering aid, alcohol medium, ball-to-material ratio 8:1, speed 300rpm, ball milling time 3h, 60℃ vacuum drying. The first stage of SPS: 1600°C, 30MPa, 5min, heating rate 100°C / min; the second stage of SPS: 1900°C, 50MPa, 15min, heating rate 50°C / min; HIP treatment: 1800°C, 200MPa, argon for 2h.

[0030] Example 2

[0031] Take 200g of coarse boron carbide powder (D50 = 50μm), and high-energy ball milling, the ball-to-material ratio of high-energy ball milling is 12:1, the grinding ball is a zirconium oxide ball, the ball milling medium is alcohol, the speed is 450rpm, the time is 72h, and the average particle size of boron carbide is 5±0.5μm. Boil it at 80℃ for 1h with concentrated hydrochloric acid, then wash it with water to pH=7, and dry it at 80℃. According to Mn:Co:Cr:Fe:Ni=3:1:1:5:0.2, high-frequency induction melting, melting temperature 1600℃, nitrogen atomization powder, sieve 150 mesh. According to the weight ratio of 5 parts of five-element high entropy alloy, 2 parts of nano-SiC fiber, 97.5 parts of boron carbide powder, 0.1 parts of sintering aid, alcohol medium, ball-to-material ratio 8:1, speed 300rpm, ball milling time 3h, 60℃ vacuum drying. The first stage of SPS: 1600°C, 30MPa, 5min, heating rate 100°C / min; the second stage of SPS: 1900°C, 50MPa, 15min, heating rate 50°C / min; HIP treatment: 1800°C, 200MPa, argon for 2h.

[0032] Example 3

[0033] Take 200g of coarse boron carbide powder (D50 = 50μm), and high-energy ball milling, the ball-to-material ratio of high-energy ball milling is 12:1, the grinding ball is a zirconium oxide ball, the ball milling medium is alcohol, the speed is 450rpm, the time is 72h, and the average particle size of boron carbide is 5±0.5μm. Boil it at 80℃ for 1h with concentrated hydrochloric acid, then wash it with water to pH=7, and dry it at 80℃. According to Mn:Co:Cr:Fe:Ni=3:1:1:5:0.2, high-frequency induction melting, melting temperature 1600℃, nitrogen atomization powder, sieve 150 mesh. According to the weight ratio of 3 parts of five-element high entropy alloy, 1 part of nano-SiC fiber, 95.6 parts of boron carbide powder, 0.08 parts of sintering aid, alcohol medium, ball-to-material ratio 8:1, speed 300rpm, ball milling time 3h, 60℃ vacuum drying. The first stage of SPS: 1600°C, 30MPa, 5min, heating rate 100°C / min; the second stage of SPS: 1900°C, 50MPa, 15min, heating rate 50°C / min; HIP treatment: 1800°C, 200MPa, argon for 2h.

[0034] Performance characterization of the composite materials prepared in the examples

[0035] project density Fracture toughness Bending strength Example 1 <![CDATA[2.75g / cm 3 ]]> <![CDATA[8.3MPa·m 1 / 2 ]]> 638MPa Example 2 <![CDATA[2.85g / cm 3 ]]> <![CDATA[8.5MPa·m 1 / 2 ]]> 647MPa Example 3 <![CDATA[2.76g / cm 3 ]]> <![CDATA[8.7MPa·m 1 / 2 ]]> 627MPa

[0036] It should be noted that the embodiments described above are only used to explain the present invention and do not constitute any limitation to the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory words, rather than restrictive words. The present invention may be modified as specified within the scope of the claims of the present invention, and the present invention may be revised without departing from the scope and spirit of the present invention. Although the present invention described therein relates to specific methods, materials and embodiments, it does not mean that the present invention is limited to the specific examples disclosed therein, on the contrary, the present invention can be extended to all other methods and applications with the same functions.

Claims

1. A high-toughness boron carbide composite material, characterized in that: The composition includes the following components by weight: 1-5 parts of quinary high entropy alloy, 0.5-2 parts of nano-SiC fiber, 92.5-97.5 parts of boron carbide powder and 0.05-0.1 parts of sintering aid.

2. A high-toughness boron carbide composite material as claimed in claim 1, characterized in that: The five-element high entropy alloy is a MnCoCrFeNi alloy, and the molar ratio of the alloy is Mn:Co:Cr:Fe:Ni=3:1:1:5:0.

2.

3. A high-toughness boron carbide composite material as claimed in claim 1, characterized in that: The average diameter of the nano-SiC fibers is 45-50 nm.

4. A high-toughness boron carbide composite material as claimed in claim 1, characterized in that: The sintering aid is yttrium powder.

5. A method for preparing a high-toughness boron carbide composite material as claimed in claim 1, characterized in that: The steps include: S1 ball milling: The coarse boron carbide powder is subjected to high-energy ball milling for 48-72 hours to obtain boron carbide powder; Preparation of S2 alloy powder: Mn, Co, Cr, Fe and Ni are smelted according to the above molar ratio, atomized and powdered, and passed through a 150-mesh sieve; S3 nanofiber dispersion: ultrasonically disperse SiC nanofibers, boron carbide powder, alloy powder, and sintering aid in alcohol for 30-40 minutes; S4 gradient sintering process: first stage: 1580-1600℃, 25-30MPa, heat preservation for 5-10min; The second stage: 1890-1900℃, 45-50MPa, insulation for 15-20min; S5 hot isostatic pressing post-treatment: 1780-1800℃, 198-200MPa argon environment, keep warm for 2-3h.

6. The method according to claim 5, characterized in that In step S1, the ball-to-material ratio of high-energy ball milling is 12:1, the grinding balls are zirconia balls, the ball milling medium is alcohol, the rotation speed is 450 rpm, the time is 72 h, and the average particle size of boron carbide after ball milling is 5±0.5 μm.

7. The method according to claim 5, characterized in that The molar ratio of Mn, Co, Cr, Fe and Ni in step S2 is 3:1:1:5:0.2, the atomization pressure in the gas atomization powder making step is 5 MPa, and the protective gas is nitrogen.

8. The method according to claim 5, characterized in that In step S3, the surface of the silicon carbide fiber is treated with 3% silane coupling agent, and the ultrasonic power is 200W.

9. The method according to claim 5, characterized in that In step S4, the heating rate of the first stage is 100° C. / min; the heating rate of the second stage is 50° C. / min.

10. The method according to claim 5, characterized in that The heating rate in step S5 is 10°C / min.