Y2O3 particle reinforced Ti2AlNb-based composite material and preparation method thereof

Abstract

The invention discloses a Y2O3 particle reinforced Ti2AlNb-based composite material and a preparation method thereof.The composite material comprises, by mole, 20%-23% of Al, 23%-27% of Nb, 0.05%-0.5% of Y2O3 and the balance Ti, and Y2O3 particles in the composite material exist in a micron-scale mode and a nano-scale mode. The Ti2AlNb-based composite material with excellent high-temperature strength is obtained in a micron-scale and nano-scale Y2O3 particle composite reinforcement mode, and the urgent demand of current aerospace on a light heat-resistant structural material can be met.

Description

Technical Field

[0001] The invention relates to a Ti2AlNb-based composite material, in particular to a Y2O3 particle-reinforced Ti2AlNb-based composite material. Background Art

[0002] Ti2AlNb-based alloys show a good balance between strength and room temperature ductility, with higher strength and better room temperature ductility than TiAl-based alloys and Ti3Al-based alloys, and higher specific strength than nickel-based high-temperature alloy IN718. However, when the temperature exceeds 650°C, the tensile strength of Ti2AlNb-based alloys drops sharply, which limits its application at higher temperatures.

[0003] A feasible technical concept to solve the above technical problems is to add a certain amount of thermodynamically stable oxides into the alloy to form an oxide dispersion phase that is insoluble in the matrix, so as to greatly increase the operating temperature of the alloy. However, it is found in applications that such oxides often segregate and grow after being directly added to Ti2AlNb-based alloys, and it is impossible to form a uniform dispersion phase, and it is also difficult to obtain a composite material with excellent mechanical properties at high temperatures. Summary of the invention

[0004] In order to solve the problems of the prior art, the present invention proposes a Y2O3 particle-reinforced Ti2AlNb-based composite material and a preparation method thereof. In the composite material, Y2O3 particles with good thermal stability and chemical stability form a uniform dispersed phase in the Ti2AlNb-based alloy, solving the high-temperature softening problem of the existing Ti2AlNb alloy.

[0005] The technical solution of the present invention is as follows:

[0006] A Y2O3 particle-reinforced Ti2AlNb-based composite material comprises 20-23% Al, 23-27% Nb, 0.05-0.5% Y2O3 and the remainder Ti in molar percentage, wherein the Y2O3 particles in the composite material exist in micron-scale and nanometer-scale forms.

[0007] In the above technical solution of the present invention, the Y2O3 particles have good thermal stability and chemical stability, and the Ti2AlNb-based alloy is dispersion strengthened. The strengthening effect can be maintained to a temperature close to the melting point of the alloy, which is particularly suitable for the extremely harsh working environment of aerospace.

[0008] In the above technical solution of the present invention, the micron-sized Y2O3 particles serve as particles for heterogeneous nucleation, which increases the nucleation rate of the B2 phase and hinders the growth of B2 grains, thereby significantly refining the B2 grain size. In addition, the micron-sized Y2O3 particles are precipitated at the grain boundaries and phase boundaries, and the nano-sized Y2O3 particles are precipitated inside the O phase. The two sizes of Y2O3 particles can effectively pin dislocations and hinder dislocation movement, thereby significantly improving the strength of the material.

[0009] According to some preferred embodiments of the present invention, the Ti2AlNb-based composite material includes 22% Al, 25% Nb, 0.1% Y2O3 and the balance Ti in molar percentage.

[0010] According to some preferred embodiments of the present invention, the Y2O3 particles exist in two forms: micrometer-scale and nanometer-scale.

[0011] The present invention further provides a method for preparing the Ti2AlNb-based composite material, which comprises the following steps:

[0012] (1) weighing raw materials to include 20-23% Al, 23-27% Nb, 0.05-0.5% Y2O3 and the balance Ti in molar percentage;

[0013] (2) mixing the raw materials uniformly to obtain a uniformly mixed raw material;

[0014] (3) pressing the uniformly mixed raw materials into electrodes, and then performing arc melting to obtain alloy ingots;

[0015] (4) forging the alloy ingot, and then air-cooling it to room temperature to obtain a forged rod;

[0016] (5) The forged rod is subjected to solid solution and aging heat treatment to obtain a Y2O3 particle reinforced Ti2AlNb-based composite material.

[0017] According to some preferred embodiments of the present invention, the preparation method further includes: subjecting the alloy ingot to a heat preservation treatment and then subjecting it to the forging, wherein the heat preservation treatment includes: subjecting the alloy ingot to a heat preservation treatment at 1100-1250°C for 1-3 hours; or, subjecting the alloy ingot to surface defects removal and then subjecting it to the heat preservation treatment and / or the forging.

[0018] According to some preferred embodiments of the present invention, the raw materials include nano Y2O3 powder, high purity aluminum, sponge titanium and Nb-Ti master alloy or Al-Nb master alloy, wherein the average particle size of the nano Y2O3 powder is less than 50 nm.

[0019] According to some preferred embodiments of the present invention, the uniformly mixed raw material is obtained by: using anhydrous ethanol to uniformly mix nano Y2O3 powder and sponge titanium to obtain sponge titanium encapsulating Y2O3; and uniformly mixing the sponge titanium encapsulating Y2O3 with high-purity aluminum, Nb-Ti master alloy or Al-Nb master alloy to obtain the uniformly mixed raw material.

[0020] According to some preferred embodiments of the present invention, the arc melting is carried out three times in a vacuum consumable arc furnace, with a voltage of 20 to 30 V, an arc starting current of 850 to 950 A, an arc stabilization current of 4 to 5 A, and a vacuum degree of 10 -1 ~10 -2 Pa.

[0021] According to some preferred embodiments of the present invention, the forging deformation rate is 0.3 to 0.7 s -1 , the cumulative deformation is 60 to 80%.

[0022] According to some preferred embodiments of the present invention, in the solution and aging heat treatment, the temperature of the solution heat treatment is 900-1000°C, the holding time is 0.5-2h, and water cooling is performed after holding; the temperature of the aging heat treatment is 750-850°C, the holding time is 3-12h, and air cooling is performed after holding.

[0023] The present invention has the following beneficial effects:

[0024] The present invention obtains a Ti2AlNb-based composite material with excellent high-temperature strength by means of composite strengthening of micron-scale and nano-scale Y2O3 particles, which can solve the current urgent demand for lightweight heat-resistant structural materials in aerospace;

[0025] The Y2O3 particle-reinforced Ti2AlNb-based composite material obtained by the present invention has good high-temperature performance. Under the test condition of 750°C, the tensile strength can reach 781MPa and the elongation is 7.2%, which are higher than the performance indicators of the current Ti-22Al-25Nb at 750°C. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 The microstructure of Y2O3 particles in the composite material obtained in Example 1; wherein (a) is a scanning electron microscope image, and (b) is a transmission electron microscope image;

[0027] Figure 2 This is a graph showing the tensile properties of the composite material obtained in Example 1 under the test condition of 750°C. DETAILED DESCRIPTION

[0028] The present invention is described in detail below in conjunction with the embodiments and drawings, but it should be understood that the embodiments and drawings are only used to exemplify the present invention and do not constitute any limitation on the protection scope of the present invention. All reasonable changes and combinations within the scope of the inventive concept of the present invention fall within the protection scope of the present invention.

[0029] Example 1

[0030] Y2O3 particle reinforced Ti2AlNb based composites were prepared by the following steps:

[0031] (1) Molar percentage Al: 22%; Nb: 25%; Y2O3: 0.1%; the rest is Ti. Weigh the raw materials, which include nano Y2O3 powder, high purity aluminum, sponge titanium and Nb-47Ti master alloy, wherein the average particle size of the nano Y2O3 powder is 30 nm;

[0032] (2) using anhydrous ethanol to uniformly mix the nano Y2O3 powder and sponge titanium, and then mixing the sponge titanium wrapped with the nano Y2O3 powder with high purity aluminum and Nb-47Ti master alloy to obtain a uniformly mixed raw material;

[0033] (3) The uniformly mixed raw materials are pressed into electrodes, and are melted three times in a vacuum consumable arc furnace to obtain an alloy ingot of Φ150 mm×240 mm, wherein the voltage of the vacuum consumable arc melting is 25 V; the arc starting current is 850-950 A; the arc stabilization current is 4.5 A; the vacuum degree is 10 -1 Pa;

[0034] (4) Remove the surface defects of the alloy ingot, take a cylindrical ingot of appropriate size, apply glass powder with special coating for high-temperature forging, keep it at 1250℃ for 2h to make the structure and temperature of the material fully uniform and eliminate casting defects, then forge it at 1200℃ with a deformation rate of 0.5s -1 , the cumulative deformation is 75%; after forging, the forged rod is air-cooled to room temperature;

[0035] (5) subjecting the forged rod obtained in step (4) to solid solution and aging heat treatment in a muffle furnace to obtain a Y2O3 particle-reinforced Ti2AlNb-based composite material; wherein the temperature of the solid solution heat treatment is 960°C, the holding time is 1 hour, and water cooling is performed after the holding; the temperature of the aging heat treatment is 760°C, the holding time is 6 hours, and air cooling is performed after the holding.

[0036] The microstructure of the composite material obtained in this embodiment is characterized as shown in the attached figure. Figure 1As shown, it can be seen that the Y2O3 particles in the composite material exist in two sizes, micrometer and nanometer. Among them, the micrometer-sized Y2O3 particles are mainly precipitated at the grain boundaries and phase boundaries, while the nanometer-sized Y2O3 particles are precipitated inside the O phase layer, forming a micro-nano dual-scale dispersed distribution phase, which significantly improves the high-temperature strength of the Y2O3 particle-reinforced Ti2AlNb-based composite material.

[0037] The tensile properties of the composite material were tested, and the results are shown in the attached Figure 2 As shown, it can be seen that the tensile strength of the material can reach 781MPa under 750°C and the elongation is 7.2%.

[0038] Example 2

[0039] Y2O3 particle reinforced Ti2AlNb based composites were prepared by the following steps:

[0040] (1) Molar percentage Al: 22%; Nb: 25%; Y2O3: 0.1%; the rest is Ti. Weigh the raw materials, which include nano Y2O3 powder, high purity aluminum, sponge titanium and Al-52.1Nb master alloy, wherein the average particle size of the nano Y2O3 powder is 30 nm;

[0041] (2) using anhydrous ethanol to uniformly mix the nano Y2O3 powder and sponge titanium, and then mixing the sponge titanium wrapped with the nano Y2O3 powder with high purity aluminum and Al-52.1Nb master alloy to obtain a uniformly mixed raw material;

[0042] (3) The uniformly mixed raw materials are pressed into electrodes, and are melted three times in a vacuum consumable arc furnace to obtain an alloy ingot of Φ150 mm×240 mm, wherein the voltage of the vacuum consumable arc melting is 25 V; the arc starting current is 850-950 A; the arc stabilization current is 4.5 A; the vacuum degree is 10 -1 Pa;

[0043] (4) Remove the surface defects of the alloy ingot, take a cylindrical ingot of appropriate size, apply glass powder with special coating for high-temperature forging, keep it at 1250℃ for 2h to make the structure and temperature of the material fully uniform and eliminate casting defects, then forge it at 1200℃ with a deformation rate of 0.5s -1 , the cumulative deformation is 60%; after forging, the forged rod is air-cooled to room temperature;

[0044] (5) subjecting the forged rod obtained in step (4) to solid solution and aging heat treatment in a muffle furnace to obtain a Y2O3 particle-reinforced Ti2AlNb-based composite material; wherein the temperature of the solid solution heat treatment is 960°C, the holding time is 1 hour, and water cooling is performed after the holding; the temperature of the aging heat treatment is 800°C, the holding time is 6 hours, and air cooling is performed after the holding.

[0045] The Y2O3 particle reinforced Ti2AlNb based composite material obtained in Example 2 was subjected to a 750°C tensile performance test, and its tensile strength was up to 740 MPa and the elongation was 13.1%.

[0046] The above embodiments are only preferred implementations of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, improvements and modifications without departing from the principle of the present invention should also be regarded as the protection scope of the present invention.

Claims

1. A Y2O3 particle-reinforced Ti2AlNb-based composite material, characterized in that: The composite material comprises 20-23% Al, 23-27% Nb, 0.05-0.5% Y2O3 and the balance Ti in molar percentage, wherein Y2O3 particles in the composite material exist in the form of micron level and nanometer level.

2. The Ti2AlNb-based composite material according to claim 1, characterized in that: It includes 22 mol% of Al, 25 mol% of Nb, 0.1 mol% of Y2O3 and the balance of Ti.

3. The method for preparing the Ti2AlNb-based composite material according to claim 1 or 2, characterized in that: It includes the following steps: (1) weighing raw materials to include 20-23% Al, 23-27% Nb, 0.05-0.5% Y2O3 and the balance Ti in molar percentage; (2) mixing the raw materials uniformly to obtain a uniformly mixed raw material; (3) pressing the uniformly mixed raw materials into electrodes, and then performing arc melting to obtain alloy ingots; (4) forging the alloy ingot, and then air-cooling it to room temperature to obtain a forged rod; (5) The forged rod is subjected to solid solution and aging heat treatment to obtain a Y2O3 particle reinforced Ti2AlNb-based composite material.

4. The preparation method according to claim 3, characterized in that: The method further comprises: subjecting the alloy ingot to heat preservation treatment and then performing the forging, wherein the heat preservation treatment comprises: preserving the alloy ingot at 1100-1250° C. for 1-3 hours.

5. The preparation method according to claim 4, characterized in that: The alloy ingot is first subjected to surface defect removal, and then subjected to the heat preservation treatment and / or the forging.

6. The preparation method according to claim 3, characterized in that: The raw materials include nano Y2O3 powder, high-purity aluminum, sponge titanium and Nb-Ti master alloy or Al-Nb master alloy, wherein the average particle size of the nano Y2O3 powder is less than 50nm.

7. The preparation method according to claim 6, characterized in that: The uniformly mixed raw material is obtained by: using anhydrous ethanol to uniformly mix nano Y2O3 powder and sponge titanium to obtain sponge titanium wrapped with Y2O3; and uniformly mixing the sponge titanium wrapped with Y2O3 with high-purity aluminum, Nb-Ti master alloy or Al-Nb master alloy to obtain the uniformly mixed raw material.

8. The preparation method according to claim 3, characterized in that: The arc melting is carried out three times in a vacuum consumable arc furnace, with a voltage of 20-30V, an arc starting current of 850-950A, an arc stabilization current of 4-5A, and a vacuum degree of 10 -1 ~10 -2 Pa.

9. The preparation method according to claim 3, characterized in that: The forging deformation rate is 0.3 to 0.7 s -1 , the cumulative deformation is 60 to 80%.

10. The preparation method according to claim 3, characterized in that: In the solution and aging heat treatment, the temperature of the solution heat treatment is 900-1000°C, the holding time is 0.5-2h, and water cooling is performed after holding. The temperature of the aging heat treatment is 750-850°C, the holding time is 3-12h, and air cooling is performed after holding.

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