A niobium-silicon-based ultrahigh-temperature alloy containing a lanthanum oxide and a preparation method thereof

Abstract

The application relates to a niobium-silicon-based super-high-temperature alloy containing lanthanum oxide and a preparation method thereof. The application aims to solve the problem that the niobium-silicon-based super-high-temperature alloy is difficult to simultaneously improve the low room-temperature toughness and high-temperature oxidation resistance. The niobium-silicon-based super-high-temperature alloy containing lanthanum oxide is made of Nb, Ti, Si, Cr, Al, Hf and La, is prepared by means of arc melting, and the lanthanum oxide phase in the obtained alloy organization induces the toughening mechanism such as crack bridging and secondary crack in the fracture process, significantly enhances the deformation capacity of the alloy, is preferentially oxidized at high temperature, reduces the internal oxidation degree of the alloy, and simultaneously improves the room-temperature fracture toughness and oxidation resistance of the niobium-silicon-based super-high-temperature alloy. The application is applied to the field of high-temperature alloys.

Description

TECHNICAL FIELD

[0001] The application relates to a niobium-silicon-based super-high-temperature alloy containing lanthanum oxide and a preparation method thereof. BACKGROUND

[0002] The core task of the development of an aero-engine is to improve the turbine inlet temperature to improve the aircraft thrust ratio, and the turbine inlet temperature depends on the temperature that can be borne by the turbine blade material. At present, the most advanced turbine blade material is a second-generation nickel-based single-crystal high-temperature alloy, but the turbine inlet temperature designed for the next-generation engine is close to the melting point of the second-generation nickel-based single-crystal high-temperature alloy, and a new generation of super-high-temperature structural material needs to be found. The niobium-silicon-based super-high-temperature alloy is highly expected due to its low density (7.3-8.6 g / cm 3 ) and high strength (270-320 MPa) at 1400 DEG C. However, in addition, the room-temperature fracture toughness and the oxidation resistance are also important indexes that need to be considered for the super-high-temperature structural material, and they are also two problems that are relatively weak and need to be solved in the application process of the niobium-silicon-based super-high-temperature alloy.

[0003] The key phases of the niobium-silicon-based super-high-temperature alloy are the Nbss phase and the silicide phase (including the Nb3Si, alpha-Nb5Si3, beta-Nb5Si3 and gamma-Nb5Si3 phases), wherein the Nbss phase provides the toughness and the environmental stability, and the silicide phase provides the strength and the basic oxidation resistance of the material. It has been proved that improving the size and the content of the silicide phase can significantly improve the high-temperature oxidation resistance of the niobium-silicon-based super-high-temperature alloy. However, the silicide phase has intrinsic brittleness, and increasing the size or the content of the silicide phase is very unfavorable to the room-temperature fracture toughness of the alloy. Therefore, it is necessary to develop a new type of niobium-silicon-based super-high-temperature alloy, which can improve the high-temperature oxidation resistance on the premise of ensuring or improving the room-temperature fracture toughness. SUMMARY

[0004] The application aims at solving the problem that the existing niobium-silicon-based super-high-temperature alloy is difficult to improve the room-temperature toughness and the high-temperature oxidation resistance simultaneously, and provides a niobium-silicon-based super-high-temperature alloy containing lanthanum oxide and a preparation method thereof.

[0005] The niobium-silicon-based super-high-temperature alloy containing lanthanum oxide is prepared by taking Nb, Ti, Si, Hf, Cr, Al and La as raw materials in an oxygen-containing environment, and the raw materials are weighed according to the atomic percentage of Ti 20-28%, Si 14-17%, Hf 1-3%, Cr 1-3%, Al 1-3%, La 0.05-0.8%, and the balance is Nb.

[0006] The preparation method of the niobium silicon-based super high-temperature alloy containing rare earth lanthanum oxide is carried out according to the following steps: one: raw material preparation: according to the atomic percentage Ti: 20-28%, Si: 14-17%, Hf: 1-3%, Cr: 1-3%, Al: 1-3%, La: 0.05-0.8%, and the rest is Nb, the metal elements are weighed according to the proportion to obtain the raw materials;

[0007] Two: smelting preparation work: the raw materials are pretreated, then the pretreated raw materials are added into the crucible of the smelting furnace, then the smelting furnace is vacuumized and filled with argon for protective smelting, and after cooling, the sample is obtained;

[0008] Three, the sample is repeatedly smelted for 4-8 times, and the niobium silicon-based super high-temperature alloy with in-situ self-grown rare earth lanthanum oxide is obtained.

[0009] The present application has the following beneficial effects:

[0010] One: the lanthanum oxide phase in the niobium silicon-based super high-temperature alloy has the characteristics of high melting point, strong stability and high hardness. The lanthanum oxide phase provides a nucleation substrate during solidification, effectively refining the alloy structure; interface separation is generated during fracture, significantly enhancing the deformation ability of the alloy. This improves the room temperature fracture toughness of the alloy.

[0011] Two: the present application achieves the purpose of enhancing high-temperature oxidation resistance without damaging or even improving the room temperature fracture toughness of the niobium silicon-based super high-temperature alloy. In a high-temperature environment, the formation of a proper amount of lanthanum oxide effectively improves the interface strength of the oxide film, improving the high-temperature oxidation resistance of the alloy.

[0012] Three: the lanthanum oxide phase in the niobium silicon-based super high-temperature alloy prepared by the present application is in-situ generated during smelting and does not need to be introduced by special means, the process is simple, the cost is low, and it has strong application value. BRIEF DESCRIPTION OF DRAWINGS

[0013] Figure 1 The X-ray diffraction patterns of the alloys prepared in Examples 1 to 4 and Comparative Example 1 of the present application are shown in the following table:

[0014] Figure 2 The microstructure results of the alloys prepared in Examples 1 to 3 and Comparative Example 1 of the present application are shown in the following table:

[0015] Figure 3 The element distribution map of the alloy prepared in Example 1 of the present application is shown in the following table:

[0016] Figure 4 The transmission electron microscope image of the alloy prepared in Example 3 of the present application is shown in the following table:

[0017] Figure 5These are crack propagation diagrams of the alloys prepared in Examples 1 and 2 of this invention during room temperature fracture.

[0018] Figure 6 The graph shows the KQ values ​​of the room temperature fracture toughness of the alloys prepared in Examples 1 to 4 and Comparative Example 1 of this invention.

[0019] Figure 7 The macroscopic morphology of the alloys prepared in Examples 1 to 4 and Comparative Example 1 after oxidation at 1250°C for 1 hour is shown.

[0020] Figure 8 The graph shows the weight gain per unit area after oxidation at 1250°C for 1 hour for the alloys prepared in Examples 1 to 4 and Comparative Example 1 of this invention. Detailed Implementation

[0021] 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.

[0022] Specific Implementation Method 1: This implementation method describes a niobium-silicon-based ultra-high temperature alloy containing rare earth lanthanum oxide, which is made from Nb, Ti, Si, Hf, Cr, Al, and La in an oxygen-containing environment. The raw materials are weighed according to the following atomic percentages: Ti 20-28%, Si 14-17%, Hf 1-3%, Cr 1-3%, Al 1-3%, La 0.05-0.8%, with the balance being Nb.

[0023] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that the niobium-silicon-based superalloy is prepared using Nb, Ti, Si, Cr, Al, Hf, and La as raw materials in an oxygen-containing environment. The raw materials are weighed according to the atomic percentages: Ti 24.7%, Si 16%, Hf 8.2%, Cr 2%, Al 1.9%, La 0.05%, with the balance being Nb. Everything else is the same as in Specific Implementation Method One.

[0024] Specific Implementation Method Three: This implementation method differs from Specific Implementation Method One or Two in that: the niobium-silicon-based superalloy is prepared using Nb, Ti, Si, Cr, Al, Hf, and La as raw materials in an oxygen-containing environment. The raw materials are weighed according to the atomic percentages: Ti 24.7%, Si 16%, Hf 8.2%, Cr 2%, Al 1.9%, La 0.1%, with the balance being Nb. Everything else is the same as in Specific Implementation Method One or Two.

[0025] Specific embodiment four: the difference between this embodiment and one of the specific embodiments one to three is that: the Nb-Si-based ultrahigh-temperature alloy is made of Nb, Ti, Si, Cr, Al, Hf and La as raw materials in an oxygen-containing environment, and the raw materials are weighed according to the atomic percentage of Ti 24.7%, Si 16%, Hf 8.2%, Cr 2%, Al 1.9%, La 0.2%, and the balance is Nb. The others are the same as one of the specific embodiments one to three.

[0026] Specific embodiment five: the difference between this embodiment and one of the specific embodiments one to four is that: the Nb-Si-based ultrahigh-temperature alloy is made of Nb, Ti, Si, Cr, Al, Hf and La as raw materials in an oxygen-containing environment, and the raw materials are weighed according to the atomic percentage of Ti 24.7%, Si 16%, Hf 6.2%, Cr 2%, Al 1.9%, La 0.4%, and the balance is Nb. The others are the same as one of the specific embodiments one to four.

[0027] Specific embodiment six: the difference between this embodiment and one of the specific embodiments one to five is that: the Nb-Si-based ultrahigh-temperature alloy is made of Nb, Ti, Si, Cr, Al, Hf and La as raw materials in an oxygen-containing environment, and the raw materials are weighed according to the atomic percentage of Ti 24.7%, Si 16%, Hf 8.2%, Cr 2%, Al 1.9%, La 0.8%, and the balance is Nb. The others are the same as one of the specific embodiments one to five.

[0028] Specific embodiment seven: the difference between this embodiment and one of the specific embodiments one to six is that: the Nb-Si-based ultrahigh-temperature alloy is made of Nb, Ti, Si, Cr, Al, Hf and La as raw materials in an oxygen-containing environment, and the raw materials are weighed according to the atomic percentage of Ti 22.7%, Si 18%, Hf 8.2%, Cr 2%, Al 1.9%, La 0.8%, and the balance is Nb. The others are the same as one of the specific embodiments one to six.

[0029] Specific embodiment eight: the difference between this embodiment and one of the specific embodiments one to seven is that: the Nb-Si-based ultrahigh-temperature alloy is made of Nb, Ti, Si, Cr, Al, Hf and La as raw materials in an oxygen-containing environment, and the raw materials are weighed according to the atomic percentage of Ti 22.7%, Si 16%, Hf 8.2%, Cr 2%, Al 1.9%, La 0.1%, and the balance is Nb. The others are the same as one of the specific embodiments one to seven.

[0030] Specific implementation nine: the difference between this embodiment and one of the specific implementations one to eight is that the niobium silicon-based super high temperature alloy is made of Nb, Ti, Si, Cr, Al, Hf and La as raw materials in an oxygen-containing environment, and the raw materials are weighed according to the atomic percentage of Ti 24.7%, Si 14%, Hf 8.2%, Cr 2%, Al 1.9%, La 0.2%, and the balance of Nb. The others are the same as one of the specific implementations one to eight.

[0031] Specific implementation ten: the difference between this embodiment and one of the specific implementations one to nine is that the niobium silicon-based super high temperature alloy is made of Nb, Ti, Si, Cr, Al, Hf and La as raw materials in an oxygen-containing environment, and the raw materials are weighed according to the atomic percentage of Ti 22.7%, Si 16%, Hf 8.2%, Cr 2%, Al 1.9%, La 0.4%, and the balance of Nb. The others are the same as one of the specific implementations one to nine.

[0032] Specific implementation eleven: the difference between this embodiment and one of the specific implementations one to ten is that the niobium silicon-based super high temperature alloy is made of Nb, Ti, Si, Cr, Al, Hf and La as raw materials in an oxygen-containing environment, and the raw materials are weighed according to the atomic percentage of Ti 24.7%, Si 16%, Hf 8.2%, Cr 2%, Al 1.9%, La 0.4%, and the balance of Nb. The others are the same as one of the specific implementations one to ten.

[0033] Specific implementation twelve: the difference between this embodiment and one of the specific implementations one to eleven is that the niobium silicon-based super high temperature alloy is made of Nb, Ti, Si, Cr, Al, Hf and La as raw materials in an oxygen-containing environment, and the raw materials are weighed according to the atomic percentage of Ti 24.7%, Si 16%, Hf 6.2%, Cr 2%, Al 1.9%, La 0.4%, and the balance of Nb. The others are the same as one of the specific implementations one to eleven.

[0034] Specific implementation thirteen: a preparation method of a niobium silicon-based super high temperature alloy containing lanthanum oxide, according to the following steps: one: raw material preparation: the metal elements are weighed according to the atomic percentage of Ti: 20-28%, Si: 14-17%, Hf: 1-3%, Cr: 1-3%, Al: 1-3%, La: 0.05-0.8%, and the balance of Nb, to obtain the raw materials;

[0035] Two: preparation of smelting: the raw materials are pretreated, then the pretreated raw materials are added to the crucible of the smelting furnace, then the smelting furnace is vacuumized and filled with argon for protection smelting, and after cooling, the sample is obtained;

[0036] III. The sample is repeatedly melted for 4-8 times, and cooled to obtain a niobium-silicon-based ultrahigh-temperature alloy with in-situ self-grown rare earth lanthanum oxide.

[0037] When the alloy is prepared by the vacuum melting method, another titanium block (not the titanium in the raw material) is usually added in another crucible. After vacuumizing and filling with argon, the titanium block is first melted to consume oxygen, so as to remove as much oxygen as possible in the melting furnace. However, the specific embodiment eliminates this step, so that a small amount of oxygen is contained in the melting furnace.

[0038] Specific embodiment fourteen: different from the specific embodiment thirteen, the raw material pretreatment method in step two is: using an angle grinder to polish and ultrasonic cleaning; wherein the ultrasonic cleaning liquid is anhydrous ethanol, the cleaning time is 20-30 min, the cleaning temperature is room temperature, and the frequency is 20-30 KHz. The others are the same as the specific embodiment thirteen.

[0039] Specific embodiment fifteen: different from the specific embodiment thirteen or fourteen, in step two, the melting furnace is washed with high-purity argon for 2-3 times, and then the melting furnace is vacuumized to 3×10 -3 -5×10 -3 Pa, and then filled with 0.3-0.7 MPa of high-purity argon for protection melting. The others are the same as the specific embodiment thirteen or fourteen.

[0040] Specific embodiment sixteen: different from one of the specific embodiments thirteen to fifteen, the equipment used for melting in step three is a vacuum non-consumable melting furnace, the melting temperature is controlled by the current intensity, the current intensity is 50-600 A, after melting, the current is decreased at a speed of 50 A / 5 s, and finally the alloy is cooled and solidified with the furnace. The others are the same as one of the specific embodiments thirteen to fifteen.

[0041] The beneficial effects of the present application are verified by the following examples:

[0042] Example one: a preparation method of a niobium-silicon-based ultrahigh-temperature alloy containing rare earth lanthanum oxide:

[0043] I: raw material preparation: according to the atomic percentage of Nb 47.15%, Ti 24.7%, Si 16%, Hf 8.2%, Cr 2%, Al 1.9%, and La 0.05%, the mass of the required Nb, Ti, Si, Cr, Al, and Hf elements is calculated and accurately weighed, wherein the La element is an irregular block with a purity of 99.50wt.%, and the Nb, Si, Cr, Al, and Hf elements are particles with a purity of 99.98wt.% and a size of 0.5-1 mm. The Ti element is sponge titanium with a purity of 99.95wt.%.

[0044] ​II. Melting Preparation: The prepared raw materials were pretreated, first polished using an angle grinder, and then ultrasonically cleaned. The ultrasonic cleaning solution was anhydrous ethanol, the cleaning time was 30 min, the cleaning temperature was room temperature, and the frequency was 30 KHz. Subsequently, La, Al, Cr, Hf, Si, Ti, and Nb were placed in the crucible of the melting furnace in order. Among them, the rare earth La element was tightly wrapped with aluminum foil and placed in the lowermost layer of the crucible. High-purity argon was used to wash the furnace twice, and then the melting furnace was vacuumed to 3 x 10 -3 Pa. Then, 0.5 MPa of high-purity argon was filled as a pollution prevention protective atmosphere.

[0045] III. Melting: Melting was carried out in a vacuum non-consumable arc melting furnace. The current was controlled between 100-550 A during melting. When the alloy was completely melted, the current was maintained at 550 A for 60 s, and then the current was gradually reduced to zero at a rate of 50 A / 5 s. After cooling, the alloy ingot was obtained. In order to ensure the uniformity of the composition, the alloy ingot was rotated and repeatedly melted 7 times, and then the Nb-Si-based superalloy with in-situ lanthanum oxide was obtained.

[0046] Example II: A method for preparing a Nb-Si-based superalloy containing lanthanum oxide is as follows:

[0047] I. Raw material preparation: According to the atomic percentage of Nb 47.1%, Ti 24.7%, Si 16%, Hf 8.2%, Cr 2%, Al 1.9%, and La 0.1%, the mass of the required Nb, Ti, Si, Cr, Al, and Hf elements was calculated and accurately weighed. The La element was an irregular block with a purity of 99.50 wt.%, and the Nb, Si, Cr, Al, and Hf elements were particles with a purity of 99.98 wt.% and a size of 0.5-1 mm. The Ti element was a sponge titanium with a purity of 99.95 wt.%.

[0048] II. Melting Preparation: The prepared raw materials were pretreated, first polished using an angle grinder, and then ultrasonically cleaned. The ultrasonic cleaning solution was anhydrous ethanol, the cleaning time was 30 min, the cleaning temperature was room temperature, and the frequency was 30 KHz. Subsequently, La, Al, Cr, Hf, Si, Ti, and Nb were placed in the crucible of the melting furnace in order. Among them, the rare earth La element was tightly wrapped with aluminum foil and placed in the lowermost layer of the crucible. High-purity argon was used to wash the furnace twice, and then the melting furnace was vacuumed to 3 x 10 -3 Pa. Then, 0.5 MPa of high-purity argon was filled as a pollution prevention protective atmosphere.

[0049] Three: Smelting: Smelting is carried out in a vacuum non-consumable arc smelting furnace. The current is controlled between 100-600 A during smelting. When the alloy is completely molten, the current is kept at 600 A for 60 s. Then the current is gradually reduced to off at a speed of 50 A / 5 s. After cooling, the alloy ingot is obtained. In order to ensure the uniformity of the composition, the alloy ingot is rotated and repeatedly smelted for 8 times. Then the Nb-Si-based ultrahigh-temperature alloy with in-situ synthesized rare earth lanthanum oxide is obtained.

[0050] Example Three: A method for preparing a Nb-Si-based ultrahigh-temperature alloy containing rare earth lanthanum oxide is as follows:

[0051] One: Preparation of raw materials: According to the atomic percentage of Nb 47.0%, Ti 24.7%, Si 16%, Hf 8.2%, Cr 2%, Al 1.9%, and La 0.2%, the mass of the required Nb, Ti, Si, Cr, Al, and Hf elements is calculated and accurately weighed. The La element is irregular block with a purity of 99.50wt.%, and the Nb, Si, Cr, Al, and Hf elements are particles with a purity of 99.98wt.% and a size of 0.2-0.3mm. The Ti element is sponge titanium with a purity of 99.95wt.%.

[0052] Two: Preparation for smelting: The prepared raw materials are pretreated. First, they are ground using an angle grinder, and then they are ultrasonically cleaned. The ultrasonic cleaning solution is anhydrous ethanol, the cleaning time is 20 min, the cleaning temperature is room temperature, and the frequency is 25 KHz. Then, the La, Al, Cr, Hf, Si, Ti, and Nb elements are placed in the crucible of the smelting furnace in order. The rare earth La element is tightly wrapped with aluminum foil and placed in the lowermost layer of the crucible. The smelting furnace is washed twice with high-purity argon, and then the smelting furnace is evacuated to 3x10 -3 Pa. Then, 0.5 MPa of high-purity argon is filled as a pollution prevention protective atmosphere.

[0053] Three: Smelting: Smelting is carried out in a vacuum non-consumable arc smelting furnace. The current is controlled between 100-550 A during smelting. When the alloy is completely molten, the current is kept at 550 A for 60 s. Then the current is gradually reduced to off at a speed of 50 A / 5 s. After cooling, the alloy ingot is obtained. In order to ensure the uniformity of the composition, the alloy ingot is rotated and repeatedly smelted for 8 times. Then the Nb-Si-based ultrahigh-temperature alloy with in-situ synthesized rare earth lanthanum oxide is obtained.

[0054] Example Four: A method for preparing a Nb-Si-based ultrahigh-temperature alloy containing rare earth lanthanum oxide is as follows:

[0055] ​One: raw material preparation: according to atomic percentage Nb is 46.4%, Ti is 24.7%, Si is 16%, Hf is 8.2%, Cr is 2%, Al is 1.9%, La is 0.8%, calculate the mass of required Nb, Ti, Si, Cr, Al, Hf elements and accurately weigh, wherein La element is irregular block with purity of 99.50wt.%, Nb, Si, Cr, Al, Hf elements are particles with purity of 99.98wt.% and size of 1-2mm, Ti element is sponge titanium with purity of 99.95wt.%.

[0056] Two: preparation work of smelting: the prepared raw materials are pretreated, first polished using an angle grinder, and then ultrasonic cleaned. The ultrasonic cleaning solution is anhydrous ethanol, the cleaning time is 20min, the cleaning temperature is room temperature, and the frequency is 25KHz. Then place La, Al, Cr, Hf, Si, Ti, Nb in the crucible of the smelting furnace in order. Among them, the rare earth La element is tightly wrapped with aluminum foil and placed in the lowermost layer of the crucible. Use high-purity argon to wash the furnace 3 times, then vacuum the smelting furnace to 3x10 -3 Pa. Then fill in 0.5MPa of high-purity argon as a pollution prevention protective atmosphere.

[0057] Three: smelting: smelting is carried out in a vacuum non-consumable arc smelting furnace, the current is controlled between 100-550A during smelting, the current is kept at 550A for 60s when the alloy is completely melted, then the current is gradually reduced to off at a speed of 50A / 5s, and the alloy ingot is obtained after cooling. In order to ensure the uniformity of the composition, the alloy ingot is rotated and repeatedly smelted 7 times, and then the Nb-Si-based superhigh-temperature alloy with in-situ self-grown rare earth lanthanum oxide is obtained.

[0058] Comparative Example One: a Nb-Si-based superhigh-temperature alloy without rare earth oxide, composed of 47.2% of Nb, 24.7% of Ti, 16% of Si, 8.2% of Hf, 2% of Cr, and 1.9% of Al according to atomic percentage. The preparation method is as follows:

[0059] One: raw material preparation: calculate the mass of required Nb, Ti, Si, Cr, Al, Hf elements according to atomic percentage and accurately weigh, wherein Nb, Si, Cr, Al, Hf elements are particles with purity of 99.98wt.% and size of 1-2mm, Ti element is sponge titanium with purity of 99.95wt.%.

[0060] II. Melting Preparation: The prepared raw materials were pretreated, first polished using an angle grinder, and then ultrasonically cleaned. The ultrasonic cleaning solution was anhydrous ethanol, the cleaning time was 30 min, the cleaning temperature was room temperature, and the frequency was 30 KHz. Subsequently, Al, Cr, Hf, Si, Ti, and Nb were placed in the crucible of the melting furnace in order. The furnace was washed with high-purity argon gas 3 times, and then the melting furnace was vacuumed to 3 x 10 -3 Pa. Then, high-purity argon gas at 0.3 MPa was filled as a pollution protection atmosphere.

[0061] III. Melting: Melting was performed in a vacuum non-consumable arc melting furnace. The current was controlled between 100-600 A during melting. When the alloy was completely molten, the current was maintained at 600 A for 60 s. Then, the current was gradually reduced to zero at a rate of 50 A / 5 s. After cooling, the alloy ingot was obtained. In order to achieve uniformity of the composition, the alloy ingot was rotated and repeatedly melted 8 times. Then, the niobium silicon-based superhigh-temperature alloy without rare earth oxides was obtained.

[0062] The X-ray diffraction patterns of the alloys of Comparative Example 1 and Examples 1-4 are shown in Figure 1 . Wherein "◆" represents the Nbss phase, "·" represents the Nb3Si phase, and "□" represents the γ-Nb5Si3 phase. The phase types of the alloys do not change, but compared with Comparative Example 1, the diffraction peaks of the metastable phase Nb3Si in Examples 1-4 increase, and the diffraction peaks of the γ-Nb5Si3 phase with good high-temperature performance increase. This is because the lanthanum oxide exists in the front of the solidification interface, causing composition undercooling, and changing the solidification path of the alloy. The decrease of the content of the Nb3Si phase and the increase of the γ-Nb5Si3 phase are beneficial to the high-temperature oxidation resistance of the alloy.

[0063] The microstructure results of the alloys of Comparative Example 1 and Examples 1-3 are shown in Figure 2 . The white phase in the alloy microstructure is the lanthanum oxide phase, and the element distribution results show that the white phase is rich in La and O elements, and poor in other elements. Since the melting point of lanthanum oxide is the highest among all phases, it is first precipitated during solidification, acts as a nucleation substrate, refines the alloy microstructure, increases the plastic work to be overcome during fracture, and is beneficial to the room temperature fracture toughness. The element distribution map of the alloy of Example 1 shows that the white phase is rich in La and O elements, which is the lanthanum oxide phase.

[0064] The crystal structure of lanthanum oxide was studied by transmission electron microscopy, and the transmission electron microscopy image of the alloy of Example 3 is shown in Figure 4 . Wherein a is a bright field image, and b is a selected area electron diffraction pattern; by comparison with standard cards, it is determined to be a trivalent lanthanum oxide, belonging to the hexagonal system P-3m1(164) space group, with lattice parameters of a = 3.937, b = 3.937, c = 6.130, and c / a = 1.557.

[0065] Figure 5 The images show crack propagation diagrams of the alloys in Examples 1 and 2. During fracture, the hard lanthanum oxide phase underwent interfacial separation, inducing toughening mechanisms such as crack bridging and secondary cracking, significantly enhancing the alloy's deformability and improving its room-temperature fracture toughness. The room-temperature fracture toughness K of Comparative Example 1 and Examples 1 to 4 is also shown. Q The value results are shown in the figure. Figure 6 As shown. The room temperature fracture toughness K of the comparative example alloy. Q The value is 11.25 MPa·m 1 / 2 K in Example 1 Q The value is 11.27 MPa·m 1 / 2 K in Example 2 Q The value is 11.41 MPa·m 1 / 2 K in Example 4 Q The value is 11.49 MPa·m 1 / 2 In Example 3, K Q The value is 13.27 MPa·m 1 / 2 This represents an increase of 17.8% compared to the control group.

[0066] The macroscopic morphology of the alloys prepared in Comparative Example 1 and Examples 1 to 4 after oxidation at 1250°C for 1 hour is as follows. Figure 7 As shown, by Figure 7 It can be seen that, compared with Comparative Example 1, the integrity of the oxide film of the alloys in Examples 1 to 4 first increased and then decreased. This indicates that the formation of an appropriate amount of lanthanum oxide can effectively improve the interfacial strength of the oxide film, thereby enhancing the oxidation resistance of the alloy. The weight gain per unit area after oxidation at 1250℃ for 1 hour for the alloys prepared in Comparative Example 1 and Examples 1 to 4 is shown in the figure. Figure 8 As shown. The oxidation weight gain per unit area of ​​the comparative example alloy is 16.69 mg / cm³. 2 In Example 1, the oxidation weight gain per unit area of ​​the alloy was reduced to 15.36 mg / cm². 2 In Example 2, the oxidation weight gain per unit area of ​​the alloy was reduced to 14.75 mg / cm². 2 In Example 3, the oxidation weight gain per unit area of ​​the alloy was reduced to 10.56 mg / cm². 2 In Example 4, the oxidation weight gain per unit area of ​​the alloy was reduced to 13.21 mg / cm². 2 .

Claims

1. A niobium-silicon based ultrahigh temperature alloy containing a lanthanide oxide, characterized in that, The Nb-Si-based ultrahigh-temperature alloy is made of Nb, Ti, Si, Hf, Cr, Al and La as raw materials in an oxygen-containing environment, and the raw materials are weighed according to the atomic percentage of Ti 24.7%, Si 16%, Hf 8.2%, Cr 2%, Al 1.9%, La 0.05%, and the balance is Nb. Or according to the atomic percentage of Ti 24.7%, Si 16%, Hf 8.2%, Cr 2%, Al 1.9%, La 0.1%, and the balance is Nb. Or according to the atomic percentage of Ti 24.7%, Si 16%, Hf 8.2%, Cr 2%, Al 1.9%, La 0.2%, and the balance is Nb. Or according to the atomic percentage of Ti 24.7%, Si 16%, Hf 6.2%, Cr 2%, Al 1.9%, La 0.4%, and the balance is Nb. Or according to the atomic percentage of Ti 24.7%, Si 16%, Hf 8.2%, Cr 2%, Al 1.9%, La 0.8%, and the balance is Nb.

2. A method of producing a niobium-silicon based ultrahigh-temperature alloy containing a lanthanide oxide according to claim 1, characterized in that The Nb-Si-based ultrahigh-temperature alloy containing rare earth lanthanum oxide contains Nbss phase, Nb3Si phase and γ-Nb5Si3 phase. The preparation method comprises the following steps:

1. Raw material preparation: weighing the metal elements according to the above proportions to obtain the raw materials; 2. Melting preparation: pretreating the raw materials, then adding the pretreated raw materials into the crucible of the melting furnace, then vacuumizing the melting furnace and filling argon for protective melting, and then cooling to obtain the sample; 3. The method of claim 2, wherein the method further comprises the step of adding a rare earth lanthanum oxide to the molten mixture. 5 3. Repeatedly melting the sample for 4-8 times to obtain the Nb-Si-based ultrahigh-temperature alloy with in-situ self-grown rare earth lanthanum oxide.

4. The method of claim 2, wherein the method further comprises the step of adding a rare earth lanthanum oxide to the molten mixture. In step two, the furnace is washed with high purity argon for 2-3 times, and then the smelting furnace is pumped to 3x10 -3 - 5x10 -3 Pa vacuum state, and then filled with 0.3-0.7 MPa of high purity argon for protection smelting.

5. The method of claim 2, wherein the lanthanum oxide-containing niobium-silicon based ultrahigh temperature alloy is prepared by the following steps of: The raw material pretreatment method in step 2 is grinding with an angle grinder and ultrasonic cleaning; wherein the ultrasonic cleaning liquid is anhydrous ethanol, the cleaning time is 20-30 min, the cleaning temperature is room temperature, and the frequency is 20-30 KHz. The melting equipment used in step 3 is a vacuum non-consumable melting furnace, the melting temperature is controlled by current intensity, the current intensity is 50-600 A, the temperature is lowered at a speed of 50 A / 5 s after melting, and finally the alloy is cooled and solidified with the furnace. ​

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