Micro-nano dual-scale precipitate enhanced and toughened nb-si based alloy and preparation method thereof

Abstract

The application relates to a micro-nano dual-scale precipitation reinforced and toughened Nb-Si-based alloy and a preparation method thereof. The application aims to solve the problem of low room-temperature fracture toughness of existing Nb-Si-based ultrahigh-temperature alloy. The micro-nano dual-scale precipitation reinforced and toughened Nb-Si-based alloy is composed of 12-20% of Si, 15-25% of Ti, 0.1-10% of X, 2-10% of Y and the balance of Nb in terms of atomic percentage; wherein X is Hf, Zr or B, and Y is Al or Cr. The application provides a smelting and heat treatment process combination technology, simplifies an organization regulation path, provides a new means for regulating the organization and performance of the Nb-Si-based alloy, and directly obtains a directional growth organization through water-cooled copper crucible and solidification rate control. The application is applied to the Nb-Si-based alloy preparation field.

Description

Technical Field

[0001] This invention relates to a micro / nano dual-scale precipitation-reinforced and toughened Nb-Si-based alloy and its preparation method. Background Technology

[0002] With the development of the aviation industry, the turbine inlet temperature requirement for engines has reached over 1800℃. Even with improved cooling and coating technologies, Ni-based alloys are insufficient to meet the demands of next-generation aero-engines, necessitating the development of new high-temperature resistant structural materials. Nb alloys and other refractory metals can be used as structural materials for turbine blades; alloys such as Nb-33Ta-0.75Zr, Nb-10Ti-Mo, Nb-0.75Zr, and Nb-10Ti have already been tested on supersonic aircraft. However, the addition of alloying elements significantly reduces the ductility and toughness of Nb alloys, making them unsuitable for machining, as seen in Nb-Si alloys.

[0003] Thanks to the incorporation of bulk silicides (Nb5Si3 / Nb3Si) as reinforcing phases into the Nb matrix, Nb-Si alloys exhibit excellent high-temperature performance, but their insufficient room-temperature toughness limits their industrial application. Summary of the Invention

[0004] The purpose of this invention is to solve the problem of low room temperature fracture toughness of existing niobium-silicon-based superalloys, and to propose a micro / nano dual-scale precipitation-reinforced and toughened Nb-Si-based alloy and its preparation method.

[0005] This invention discloses a micro / nano dual-scale precipitation-reinforced and toughened Nb-Si-based alloy, which is composed of 12-20% Si, 15-25% Ti, 0.1-10% X, 2-10% Y and the balance Nb according to atomic percentage; where X is Hf, Zr or B and Y is Al or Cr.

[0006] The present invention discloses a method for preparing a micro / nano dual-scale precipitation-reinforced and toughened Nb-Si-based alloy, which is carried out according to the following steps:

[0007] 1. Weigh the raw materials according to the stated atomic ratio;

[0008] 2. Place the pretreated raw materials into the crucible of the melting furnace, and evacuate the furnace to a vacuum level of 1×10⁻⁶. -3 Pa ~ 5 × 10 -3 Pa, then argon gas is introduced for melting. During melting, the current is increased from 0A to 600A. After melting, the current is reduced and cooled. After melting is repeated 6 times, Nb-Si based alloy ingot is obtained; the current reduction rate at the end of the last melting is 10A / s to 30A / s.

[0009] 3. The Nb-Si based alloy ingot is placed in a heat treatment furnace for aging treatment at a temperature range of 400℃ to 1000℃ for a holding time of 0.5h to 24h, and the cooling condition is furnace cooling, to obtain a micro-nano dual-scale precipitation-reinforced and toughened Nb-Si based alloy.

[0010] The present invention has the following beneficial effects:

[0011] I. The compositional design concept of adding Nb5Si3 phase stabilizing elements (Hf, Zr, B, etc.) to Nb-Si alloys can yield a high-strength and high-toughness cast Nb-Si alloy. Zr promotes the precipitation of γ-Nb5Si3, and the hexagonal γ-Nb5Si3 bulk significantly improves the alloy's room-temperature toughness. Furthermore, the alloy's properties can be further enhanced through heat treatment or directional solidification, making it a highly promising high-temperature alloy system.

[0012] II. The present invention proposes a micro / nano dual-scale silicide structure design. Micron-scale silicides significantly improve the strength of the alloy, while nano-scale silicides not only play a precipitation strengthening role, but also have a toughening effect on the Nbss phase, thus achieving a simultaneous improvement in the strength and toughness of the alloy.

[0013] Third, the holding temperature range for aging treatment corresponds to the temperature range for nano-precipitation of silicides within the Nb matrix. During the final melting in the water-cooled copper crucible, the high current reduction rate at the bottom of the melt, under the cooling effect of the crucible, creates a longitudinal temperature gradient between the upper surface and the bottom of the melt, which is beneficial for the directional growth of the microstructure. Furthermore, the rapid solidification rate increases the degree of Si solution within the Nb phase and simultaneously increases casting stress, which is conducive to the precipitation of nano-sized silicides during the prolonged holding period.

[0014] IV. Solidification and solid-state phase transformation have a significant impact on microstructure and properties. The smelting and heat treatment process combined in this invention simplifies the microstructure control path and provides a new means for controlling the microstructure and properties of Nb-Si based alloys. Furthermore, compared to complex directional solidification techniques, this method can directly obtain directionally grown microstructures by controlling the water-cooled copper crucible and the solidification rate.

[0015] Fifth, the smelting and heat treatment equipment required by this invention is simple, easy to operate, and has low process cost, and can be applied to a variety of high-temperature alloys. Attached Figure Description

[0016] Figure 1 Microstructure of the Nb-16Si-24Ti-5Hf-4Cr alloy (current drop rate 30 A / s) prepared in Example 1; where a is the microstructure observed at low magnification and b is the nano-precipitated phase observed at high magnification.

[0017] Figure 2Microstructure of Nb-16Si-24Ti-5Hf-4Cr alloy (current drop rate 10A / s) prepared in Example 2; where a is the microstructure observed at low magnification and b is the nano-precipitated phase observed at high magnification;

[0018] Figure 3 The microstructure of the Nb-16Si-24Ti-5Hf-4Cr alloy prepared in Comparative Example 1;

[0019] Figure 4 Microstructure of Nb-16Si-24Ti-6Zr-2Al alloy (current drop rate 10A / s) prepared in Example 3; where a is the microstructure observed at low magnification, and b is the nano-precipitated phase observed at high magnification;

[0020] Figure 5 The microstructure of the Nb-16Si-24Ti-6Zr-2Al alloy prepared in Comparative Example 2;

[0021] Figure 6 The room temperature compressive strength and fracture toughness of the alloys prepared in Examples 1 to 3 and Comparative Examples 1 and 2. Detailed Implementation

[0022] The technical solution of the present invention is not limited to the specific embodiments listed below, but also includes any combination of the specific embodiments.

[0023] Specific Implementation Method 1: This implementation method is a micro / nano dual-scale precipitation-reinforced and toughened Nb-Si based alloy, which is composed of 12-20% Si, 15-25% Ti, 0.1-10% X, 2-10% Y and the balance Nb according to atomic percentage; where X is Hf, Zr or B and Y is Al or Cr.

[0024] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that the micro / nano dual-scale precipitation-reinforced and toughened Nb-Si based alloy is composed of 16% Si, 24% Ti, 5% Hf, 4% Cr, and the balance Nb by atomic percentage. Everything else is the same as in Specific Implementation Method One.

[0025] Specific Implementation Method Three: This implementation method differs from Specific Implementation Method One or Two in that the micro / nano dual-scale precipitation-reinforced and toughened Nb-Si based alloy is composed of 16% Si, 24% Ti, 6% Zr, 2% Al, and the balance Nb by atomic percentage. Everything else is the same as in Specific Implementation Method One or Two.

[0026] Specific Implementation Method Four: This implementation method describes a method for preparing a micro / nano dual-scale precipitation-reinforced and toughened Nb-Si based alloy, which is carried out according to the following steps:

[0027] 1. Weigh the raw materials according to the stated atomic ratio;

[0028] 2. Place the pretreated raw materials into the crucible of the melting furnace, and evacuate the furnace to a vacuum level of 1×10⁻⁶. -3 Pa ~ 5 × 10 -3 Pa, then argon gas is introduced for melting. During melting, the current is increased from 0A to 600A. After melting, the current is reduced and cooled. After melting is repeated 6 times, Nb-Si based alloy ingot is obtained; the current reduction rate at the end of the last melting is 10A / s to 30A / s.

[0029] 3. The Nb-Si based alloy ingot is placed in a heat treatment furnace for aging treatment at a temperature range of 400℃ to 1000℃ for a holding time of 0.5h to 24h, and the cooling condition is furnace cooling, to obtain a micro-nano dual-scale precipitation-reinforced and toughened Nb-Si based alloy.

[0030] In this embodiment, when placing the raw materials into the crucible of the melting furnace, they are placed in order of decreasing melting point, with the lower melting point placed at the bottom and the higher melting point placed at the top. In step three, when the current is reduced for cooling after the final melting, the arc gun rotates clockwise at a uniform speed on the surface of the melt.

[0031] Specific Implementation Method Five: This implementation method differs from Specific Implementation Method Four in that the pretreatment steps for raw materials in step two include: descaling, ultrasonic cleaning, and drying. Everything else is the same as in Specific Implementation Method Four.

[0032] Specific Implementation Method Six: This implementation method differs from Specific Implementation Method Four or Five in that the ultrasonic cleaning time is 5-15 minutes, the power is 100W-150W, the frequency is 20KHz-35KHz, and the cleaning solution is anhydrous ethanol. Everything else is the same as in Specific Implementation Method Four or Five.

[0033] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Methods Four to Six in that: sponge titanium is added to another crucible in the smelting furnace. During smelting, the sponge titanium is smelted first to remove residual oxygen in the smelting furnace, and then the raw materials are smelted. Everything else is the same as in Specific Implementation Methods Four to Six.

[0034] Specific Implementation Method Eight: This implementation method differs from Specific Implementation Methods Four through Seven in that: in step two, the furnace is evacuated to a vacuum level of 3×10⁻⁶. -3 Pa. The rest is the same as in any of the specific embodiments four to seven.

[0035] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Methods Four to Eight in that the temperature range in step three is 1000℃, and the heat preservation time is 4 hours. Everything else is the same as in Specific Implementation Methods Four to Eight.

[0036] Specific Implementation Method Ten: This implementation method differs from Specific Implementation Methods Four to Nine in that the temperature range in step three is 1000℃ and the heat preservation time is 12 hours. Everything else is the same as in Specific Implementation Methods Four to Nine.

[0037] The beneficial effects of the present invention are verified using the following embodiments:

[0038] Example 1: This example describes a micro / nano dual-scale precipitation-reinforced and toughened Nb-Si-Ti-Hf-Cr based alloy, which is composed of the following components: 51 at.% Nb, 16 at.% Si, 24 at.% Ti, 5 at.% Hf, and 4 at.% Cr.

[0039] Its preparation method is as follows:

[0040] (1) Weigh the raw materials Nb, Si, Ti, Zr and Al according to the above atomic ratio, wherein Nb is 1-10mm irregular flakes with a purity of 99.95%, Si is 1-3mm particles with a purity of 99.95%, Ti is sponge titanium with a purity of 99.5%, and the purity of raw materials Zr and Al is above 99.9%.

[0041] (2) Surface pretreatment of raw materials and sponge titanium to remove surface oxide scale and impurities: use 400# SiC sandpaper to polish the surface, and then place it in anhydrous ethanol for ultrasonic cleaning for 10 minutes with a power of 100W and a frequency of 30KHz.

[0042] (3) Place the raw materials into the crucible in the order of Al, Si, Ti, Zr, Nb, and simultaneously place 100g of sponge titanium in an adjacent crucible. Water-cooled copper crucible arc melting is used: 1) Turn on the circulating cooling water at a flow rate of 2m / s; 2) Evacuate to a vacuum of 3×10⁻⁶ m / s. - 3 After Pa, high-purity argon gas is introduced to -0.05MPa; 3) Arc ignition melting: First, sponge titanium is melted to remove residual oxygen in the melting furnace, and then the raw materials are melted. During melting, the current is gradually increased from 0A to 600A. In the molten state, the current is maintained at 600A for 30s and then gradually reduced to cool, resulting in a button ingot; 4) To ensure compositional uniformity, the ingot is flipped 180° and melted again, repeating this melting process 6 times. During each alloy remelting, sponge titanium is melted first to absorb residual oxygen and prevent contamination of the alloy melt, and then the raw materials are melted. During the cooling process of the last melting, the current decrease rate is 30A / s, and when it decreases to 150A, it immediately drops to 0A.

[0043] (4) The ingot was placed in a heat treatment furnace for aging treatment at a temperature of 1000℃ for 6 hours and furnace cooling was used to obtain a micro-nano dual-scale precipitation-enhanced and toughened Nb-16Si-24Ti-5Hf-4Cr alloy.

[0044] Example 2: A micro / nano dual-scale precipitation-reinforced and toughened Nb-Si-Ti-Hf-Cr based alloy, composed of the following components: 51 at.% Nb, 16 at.% Si, 24 at.% Ti, 5 at.% Hf, and 4 at.% Cr.

[0045] Its preparation method is as follows:

[0046] (1) Weigh the raw materials Nb, Si, Ti, Zr and Al according to the above atomic ratio, wherein Nb is 1-10mm irregular flakes with a purity of 99.95%, Si is 1-3mm particles with a purity of 99.95%, Ti is sponge titanium with a purity of 99.5%, and the purity of raw materials Zr and Al is above 99.9%.

[0047] (2) Surface pretreatment of raw materials and sponge titanium to remove surface oxide scale and impurities: use 400# SiC sandpaper to polish the surface, and then place it in anhydrous ethanol for ultrasonic cleaning for 10 minutes with a power of 100W and a frequency of 30KHz.

[0048] (3) Place the raw materials into the crucible in the order of Al, Si, Ti, Zr, Nb, and simultaneously place 100g of sponge titanium in an adjacent crucible. Water-cooled copper crucible arc melting is used: 1) Turn on the circulating cooling water at a flow rate of 2m / s; 2) Evacuate to a vacuum of 3×10⁻⁶ m / s. - 3 After Pa, high-purity argon gas is introduced to -0.05 MPa; 3) Arc ignition melting: First, sponge titanium is melted to remove residual oxygen in the melting furnace, and then the raw materials are melted. During melting, the current is gradually increased from 0A to 600A. In the molten state, the current is maintained at 600A for 30s and then gradually reduced to cool, resulting in a button ingot; 4) To ensure compositional uniformity, the ingot is flipped 180° and melted again. This melting process is repeated 6 times. During each alloy remelting, sponge titanium is melted first to absorb residual oxygen and prevent contamination of the alloy melt, and then the raw materials are melted. During the final melting and cooling process, the current decrease rate is 10A / s, and when it decreases to 150A, it immediately drops to 0A.

[0049] (4) The ingot was placed in a heat treatment furnace for aging treatment at a temperature of 1000℃ for 6 hours and furnace cooling was used to obtain a micro-nano dual-scale precipitation-enhanced and toughened Nb-16Si-24Ti-5Hf-4Cr alloy.

[0050] Example 3: A micro / nano dual-scale precipitation-reinforced and toughened Nb-Si-Ti-Zr-Al based alloy, composed of the following components: 52 at.% Nb, 16 at.% Si, 24 at.% Ti, 6 at.% Zr, and 2 at.% Al.

[0051] Its preparation method is as follows:

[0052] (1) Weigh the raw materials Nb, Si, Ti, Zr and Al according to the above atomic ratio, wherein Nb is 1-10mm irregular flakes with a purity of 99.95%, Si is 1-3mm particles with a purity of 99.95%, Ti is sponge titanium with a purity of 99.5%, and the purity of raw materials Zr and Al is above 99.9%.

[0053] (2) Surface pretreatment of raw materials and sponge titanium to remove surface oxide scale and impurities: use 400# SiC sandpaper to polish the surface, and then place it in anhydrous ethanol for ultrasonic cleaning for 10 minutes with a power of 100W and a frequency of 30KHz.

[0054] (3) Place the raw materials into the crucible in the order of Al, Si, Ti, Zr, Nb, and simultaneously place 100g of sponge titanium in an adjacent crucible. Water-cooled copper crucible arc melting is used: 1) Turn on the circulating cooling water at a flow rate of 2m / s; 2) Evacuate to a vacuum of 3×10⁻⁶ m / s. - 3 After Pa, high-purity argon gas is introduced to -0.05 MPa; 3) Arc ignition melting: First, sponge titanium is melted to remove residual oxygen in the melting furnace, and then the raw materials are melted. During melting, the current is gradually increased from 0A to 600A. In the molten state, the current is maintained at 600A for 30s and then gradually reduced to cool, resulting in a button ingot; 4) To ensure compositional uniformity, the ingot is flipped 180° and melted again. This melting process is repeated 6 times. During each alloy remelting, sponge titanium is melted first to absorb residual oxygen and prevent contamination of the alloy melt, and then the raw materials are melted. During the final melting and cooling process, the current decrease rate is 10A / s, and when it decreases to 150A, it immediately drops to 0A.

[0055] (4) The ingot was placed in a heat treatment furnace for aging treatment at a temperature of 1000℃ for 6 hours and furnace cooling was used to obtain a micro-nano dual-scale precipitation-enhanced and toughened Nb-16Si-24Ti-6Zr-2Al alloy.

[0056] Compared with Example 1, the Nb-Si-Ti-Hf-Cr based alloy of this example is composed of the following components: 51 at.% Nb, 16 at.% Si, 24 at.% Ti, 5 at.% Hf, and 4 at.% Cr.

[0057] Its preparation method is as follows:

[0058] (1) Weigh the raw materials Nb, Si, Ti, Zr and Al according to the above atomic ratio, wherein Nb is 1-10mm irregular flakes with a purity of 99.95%, Si is 1-3mm particles with a purity of 99.95%, Ti is sponge titanium with a purity of 99.5%, and the purity of raw materials Zr and Al is above 99.9%.

[0059] (2) Surface pretreatment of raw materials and sponge titanium to remove surface oxide scale and impurities: use 400# SiC sandpaper to polish the surface, and then place it in anhydrous ethanol for ultrasonic cleaning for 10 minutes with a power of 100W and a frequency of 30KHz.

[0060] (3) Place the raw materials into the crucible in the order of Al, Si, Ti, Zr, Nb, and simultaneously place 100g of sponge titanium in an adjacent crucible. Water-cooled copper crucible arc melting is used: 1) Turn on the circulating cooling water at a flow rate of 2m / s; 2) Evacuate to a vacuum of 3×10⁻⁶ m / s. - 3 After Pa, high-purity argon gas is introduced to -0.05MPa; 3) Arc ignition melting: First, sponge titanium is melted to remove residual oxygen in the melting furnace, and then the raw materials are melted. During melting, the current is gradually increased from 0A to 600A. In the molten state, the current is maintained at 600A for 30s and then gradually reduced to cool, resulting in a button ingot; 4) To ensure compositional uniformity, the ingot is flipped 180° and melted again, and this melting process is repeated 6 times. During each alloy remelting, sponge titanium is melted first to absorb residual oxygen and avoid contamination of the alloy melt, and then the raw materials are melted. During the cooling process of the last melting, the current decrease rate is 10A / s, and when it decreases to 150A, it is immediately reduced to 0A, resulting in an Nb-16Si-24Ti-5Hf-4Cr alloy ingot.

[0061] Comparative Example 2: A Nb-Si-Ti-Zr-Al based alloy, composed of the following components: 52 at.% Nb, 16 at.% Si, 24 at.% Ti, 6 at.% Zr, and 2 at.% Al.

[0062] Its preparation method is as follows:

[0063] (1) Weigh the raw materials Nb, Si, Ti, Zr and Al according to the above atomic ratio, wherein Nb is 1-10mm irregular flakes with a purity of 99.95%, Si is 1-3mm particles with a purity of 99.95%, Ti is sponge titanium with a purity of 99.5%, and the purity of raw materials Zr and Al is above 99.9%.

[0064] (2) Surface pretreatment of raw materials and sponge titanium to remove surface oxide scale and impurities: use 400# SiC sandpaper to polish the surface, and then place it in anhydrous ethanol for ultrasonic cleaning for 10 minutes with a power of 100W and a frequency of 30KHz.

[0065] (3) Place the raw materials into the crucible in the order of Al, Si, Ti, Zr, Nb, and simultaneously place 100g of sponge titanium in an adjacent crucible. Water-cooled copper crucible arc melting is used: 1) Turn on the circulating cooling water at a flow rate of 2m / s; 2) Evacuate to a vacuum of 3×10⁻⁶ m / s. - 3 After Pa, high-purity argon gas is introduced to -0.05MPa; 3) Arc ignition melting: First, sponge titanium is melted to remove residual oxygen in the melting furnace, and then the raw materials are melted. During melting, the current is gradually increased from 0A to 600A. In the molten state, the current is maintained at 600A for 30s and then gradually reduced to cool, resulting in a button ingot; 4) To ensure compositional uniformity, the ingot is flipped 180° and melted again, and this melting process is repeated 6 times. During each alloy remelting, sponge titanium is melted first to absorb residual oxygen and avoid contamination of the alloy melt, and then the raw materials are melted. During the cooling process of the last melting, the current decrease rate is 10A / s, and when it decreases to 150A, it is immediately reduced to 0A, resulting in an Nb-16Si-24Ti-6Zr-2Al alloy ingot.

[0066] The microstructure of the Nb-16Si-24Ti-5Hf-4Cr alloy (current drop rate 30 A / s) prepared in Example 1 is as follows: Figure 1 As shown, under rapid cooling rates, the alloy microstructure resembles that of directional solidification, exhibiting relatively straight, directionally grown primary dendrite axes of the α-Nb5Si3 phase, along with large-sized fishbone-like Nbss / α-Nb5Si3 eutectic structures. This is because the large current reduction rate in the water-cooled copper crucible creates a large longitudinal temperature gradient in the alloy melt during solidification, causing the microstructure to grow in the opposite direction of heat dissipation. This near-directional growth significantly improves the alloy's room-temperature toughness. Furthermore, in high-magnification scanning image (b), high-density, dispersed nano-silicide particles appear within the Nbss matrix. The precipitation of nano-silicides contributes to improving the overall mechanical properties of the alloy.

[0067] The microstructure of the Nb-16Si-24Ti-5Hf-4Cr alloy (current drop rate 10 A / s) prepared in Example 2 is as follows: Figure 2 As shown. Compared to the alloy prepared in Example 1, the cooling rate in Example 2 is lower. The slower solidification rate of the alloy melt weakens the directional growth characteristics, and the elongated α-Nb5Si3 phase disappears and transforms into a blocky α-Nb5Si3 phase, as shown. Figure 2 As shown in (a). Furthermore, in high-magnification scanning... Figure 2 A large number of nano-precipitated silicide particles were also observed in (b). Comparative Example 1 is as follows: Figure 3 The microstructure of the Nb-16Si-24Ti-5Hf-4Cr alloy prepared by conventional solidification is shown. Compared with Example 1, the directional growth microstructure characteristics disappear, as do the primary dendrite axes and secondary herringbone eutectic structure, exhibiting a conventional arc-melted as-cast microstructure. Furthermore, no nano-precipitates are present within the Nb-16Si-24Ti-5Hf-4Cr alloy in the conventional as-cast microstructure.

[0068] The microstructure of the Nb-16Si-24Ti-6Zr-2Al alloy (current drop rate 10 A / s) prepared in Example 3 is as follows: Figure 4 As shown. Compared to the alloys prepared in Examples 1 and 2, the alloy in Example 3 exhibits hexagonal γ-Nb5Si3 bulk structures. This is due to the structural change of Nb5Si3 caused by the addition of Zr. Furthermore, the fishbone-like eutectic structure disappears, replaced by numerous petal-like eutectic structures and divergent eutectic structures distributed along the hexagonal γ-Nb5Si3. High-magnification scanning images reveal uniform precipitation of nano-silicide particles, but in fewer quantity than in the alloy of Example 2. The microstructure of Example 2 is shown below. Figure 5 As shown, no nanoparticles are precipitated in the tissue obtained by conventional coagulation.

[0069] The Nbss phase composition analysis of the alloy microstructures prepared in Examples 1 to 3 is listed in Table 1. It can be seen that the Si content dissolved in the Nbss phase in the alloys prepared in Examples 1 to 3 is lower than that in the comparative example. In the alloy microstructure prepared in Example 1, the Si content in the Nbss phase is only 0.84 at.%, far lower than the 2.35 at.% in the comparative example. As the main ductile phase in Nb-Si alloys, the reduction in the dissolved Si content is beneficial to improving the toughness of the Nbss phase.

[0070] Table 1

[0071]

[0072]

[0073] The room temperature compressive strength and fracture toughness of the alloys prepared in Examples 1 to 3 are as follows: Figure 6 As shown, the mechanical properties of the alloys prepared in Examples 1 to 3 are significantly improved compared to conventional cast alloys. The Nb-16Si-24Ti-5Hf-4Cr alloy prepared in Comparative Example 1 has a compressive strength of 2078 MPa and a toughness of 10.21 MPa·m. 1 / 2 The alloy prepared in Example 1 achieved a compressive strength of 2235 MPa and a toughness of 15.65 MPa·m. 1 / 2The alloy prepared in Example 2 achieved a compressive strength of 2184 MPa and a toughness of 13.52 MPa·m. 1 / 2 The alloy prepared in Example 3 achieved a compressive strength of 2156 MPa and a toughness of 14.46 MPa·m. 1 / 2 The results were all higher than those of the Nb-16Si-24Ti-6Zr-2Al alloy prepared in Comparative Example 2. The increased solidification rate resulted in directional growth characteristics in the microstructure, similar to a directional solidification process, which is beneficial to the improvement of alloy performance. In addition, the precipitation of nano-sized silicides significantly enhanced the room temperature mechanical properties of the alloy, resulting in a good balance between strength and toughness.

Claims

1. A micro / nano dual-scale precipitation-reinforced and toughened Nb-Si-based alloy, characterized in that, The micro / nano dual-scale precipitation-reinforced and toughened Nb-Si based alloy is composed of 12-20% Si, 15-25% Ti, 0.1-10% X, 2-10% Y, and the balance Nb in atomic percentage; where X is Hf, Zr, or B, and Y is Al or Cr. The preparation method of the Nb-Si based alloy is carried out according to the following steps:

1. Weigh the raw materials according to the stated atomic ratio; 2. Place the pretreated raw materials into the crucible of the melting furnace, and evacuate the furnace to a vacuum level of 1×10⁻⁶. -3 Pa~5×10 - 3 Pa, then argon gas is introduced for melting. During melting, the current is increased from 0A to 600A. After melting, the current is reduced and cooled. After melting is repeated 6 times, Nb-Si based alloy ingot is obtained; the current reduction rate at the end of the last melting is 10A / s~30A / s.

3. The Nb-Si based alloy ingot is placed in a heat treatment furnace for aging treatment at a temperature range of 400℃ to 1000℃ for a holding time of 0.5h to 24h, and the cooling condition is furnace cooling, to obtain a micro-nano dual-scale precipitation-reinforced and toughened Nb-Si based alloy.

2. The micro / nano dual-scale precipitation-reinforced and toughened Nb-Si based alloy according to claim 1, characterized in that, The micro / nano dual-scale precipitation-reinforced and toughened Nb-Si based alloy is composed of 16% Si, 24% Ti, 5% Hf, 4% Cr and the balance Nb in atomic percentage.

3. The micro / nano dual-scale precipitation-reinforced and toughened Nb-Si based alloy according to claim 1, characterized in that, The micro / nano dual-scale precipitation-reinforced and toughened Nb-Si based alloy is composed of 16% Si, 24% Ti, 6% Zr, 2% Al and the balance Nb in atomic percentage.

4. The micro / nano dual-scale precipitation-reinforced and toughened Nb-Si based alloy according to claim 1, characterized in that... Step 2 pretreatment steps: descaling, ultrasonic cleaning and drying.

5. The micro / nano dual-scale precipitation-reinforced and toughened Nb-Si-based alloy according to claim 4, characterized in that... The ultrasonic cleaning time is 5-15 minutes, the power is 100W-150W, the frequency is 20KHz-35KHz, and the cleaning solution is anhydrous ethanol.

6. The micro / nano dual-scale precipitation-reinforced and toughened Nb-Si based alloy according to claim 1, characterized in that... Sponge titanium is added to another crucible in the smelting furnace. During smelting, the sponge titanium is smelted first to remove residual oxygen in the smelting furnace before the raw materials are smelted.

7. The micro / nano dual-scale precipitation-reinforced and toughened Nb-Si based alloy according to claim 1, characterized in that... In step two, the furnace is evacuated to a vacuum level of 3×10. -3 Pa.

8. The micro / nano dual-scale precipitation-reinforced and toughened Nb-Si based alloy according to claim 1, characterized in that... In step three, the temperature is 1000℃ and the holding time is 4 hours.

9. The micro / nano dual-scale precipitation-reinforced and toughened Nb-Si based alloy according to claim 1, characterized in that... In step three, the temperature is 1000℃ and the holding time is 12 hours.

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