Additive manufacturing nano precipitated phase reinforced refractory TiNbVAlSix high-entropy alloy

Abstract

The invention relates to the field of additive manufacturing nano precipitated phase reinforced refractory high-entropy alloys, in particular to an additive manufacturing nano precipitated phase reinforced refractory TiNbVAlSix high-entropy alloy. The high-entropy alloy comprises the following chemical components by atomic percent: 45-55% of Ti; 15%-25% of Nb; v, 15%-25%; 8%-15% of Al; and 0-9% of Si. The alloy is prepared through a laser directional energy deposition additive manufacturing method, precipitation of a nano Ti5Si3 phase at the grain boundary and in grains is promoted through addition of the Si element, microstructure characteristics of a disordered BCC phase, an ordered B2 phase and the nano Ti5Si3 phase are formed, and the content of the nano Ti5Si3 phase is in direct proportion to the content of the Si element. The high-entropy alloy has the performance characteristics of light weight and high strength, can meet the requirements of part of aerospace parts, and has important value for development and application of TiNbVAl and related light refractory high-entropy alloy systems.

Description

Technical Field

[0001] The present invention relates to the field of additive manufacturing of nano-precipitated phase-reinforced refractory high entropy alloys, and in particular to an additive manufacturing nano-precipitated phase-reinforced refractory TiNbVAlSi x High entropy alloy. Background Art

[0002] With the rapid development of aerospace technology, the demand for high temperature / ultra-high temperature resistant structural materials for core components such as aero-engines and aircraft is becoming more and more urgent. Refractory high entropy alloys were first proposed by the Senkov team of the U.S. Air Force Laboratory in 2010. The single-phase BCC structure WTaNbMo and WTaNbMoV refractory high entropy alloys they developed can not only maintain structural stability at 1400°C, but also maintain a yield strength of 405MPa in a high-temperature compression test at 1600°C, and have extremely excellent resistance to high temperature softening. However, the high density (≥12g / cm 3 ) and poor plasticity limit its further application.

[0003] The emergence of lightweight refractory high entropy alloys (LRHEAs) provides an effective solution to the shortcomings of RHEAs such as poor room temperature plasticity and high density. At present, the main research on LRHEAs focuses on the system with low-density toughness component Ti as the matrix element and Al, Nb, and V as alloying elements. Among them, Nb and V are BCC forming elements, while Al has strong bonding ability with refractory elements and can promote the precipitation of B2 phase in the matrix. Due to the special organizational structure, LRHEAs usually exhibit excellent ductility and low density. However, the low strength of this system at room temperature makes it difficult to obtain practical applications. Therefore, how to improve the room temperature strength of the alloy and achieve a good balance between strength and plasticity has become a key issue in realizing the application of LRHEAs. Summary of the invention

[0004] In view of the above-mentioned shortcomings of the prior art, the main purpose of the present invention is to provide a nano-precipitated phase-reinforced refractory TiNbVAlSi x High entropy alloy, by introducing Si to regulate the content and distribution of nano-precipitated phase, thus obtaining a body-centered cubic Ti-Nb-V-Al-Si high entropy alloy with high specific strength.

[0005] In order to achieve the above object, the technical solution of the present invention is as follows:

[0006] An additive manufacturing nano-precipitation phase strengthened refractory TiNbVAlSi x The high entropy alloy has a chemical composition, in terms of atomic percentage, as follows:

[0007] Ti: 45-55%; Nb: 15-25%; V: 15-25%; Al: 8-15%; Si: 0-9%.

[0008] The additive manufacturing nano-precipitation phase strengthened refractory TiNbVAlSi x High entropy alloy, preferably, Si: 1-3%.

[0009] The additive manufacturing nano-precipitation phase strengthened refractory TiNbVAlSi x The high entropy alloy is first mixed and baked, and then the high entropy alloy is prepared by the laser directed energy deposition in-situ alloying method.

[0010] The additive manufacturing nano-precipitation phase strengthened refractory TiNbVAlSi x High entropy alloy, when mixing and baking powder, Ti 50 Nb 20 V 20 Al 10 The pre-alloyed powder and Si powder are mixed in a powder mixer for 3 to 5 hours, and the mixed powder is placed in a drying oven and dried at 70 to 100° C. for 1 to 5 hours.

[0011] The additive manufacturing nano-precipitation phase strengthened refractory TiNbVAlSi x For high entropy alloy, the process parameters of laser directed energy deposition are as follows: laser power is 500-1000W, and scanning speed is 300-600mm / min.

[0012] The additive manufacturing nano-precipitation phase strengthened refractory TiNbVAlSi x High entropy alloy, when no Si element is added, the high entropy alloy is composed of a disordered BCC phase and a dispersed ordered B2 phase.

[0013] The additive manufacturing nano-precipitation phase strengthened refractory TiNbVAlSi x The high entropy alloy, when no Si element is added, has a yield strength of 700-760 MPa, a tensile strength of 800-836 MPa, and an elongation of 30-35% at room temperature.

[0014] The additive manufacturing nano-precipitation phase strengthened refractory TiNbVAlSi x High entropy alloy, the addition of Si element promotes the precipitation of nano-precipitate phase in high entropy alloy composed of disordered BCC + ordered B2 phase, and the content of precipitate phase is proportional to the content of Si element.

[0015] The additive manufacturing nano-precipitation phase strengthened refractory TiNbVAlSi x High entropy alloy, nano-precipitated phase is Ti 5 Si 3Phase, the average size is 100 to 250 nm, and the volume fraction is greater than 0 to 1.5%.

[0016] The additive manufacturing nano-precipitation phase strengthened refractory TiNbVAlSi x High entropy alloy, after adding Si element, the yield strength of high entropy alloy at room temperature is increased to 924-1100MPa, the tensile strength is 928-1203MPa, and the elongation is 10-22%.

[0017] The design idea of ​​the present invention is:

[0018] The present invention considers the role of each element in LRHEAs and optimizes the atomic ratio, and selects Ti 50 Nb 20 V 20 Al 10 As a matrix alloy, Si element can form nano-scale silicide for precipitation strengthening. At the same time, silicide has the characteristics of high melting point and high hardness. Therefore, adding an appropriate amount of Si element can further improve the strength of the alloy and achieve a good balance between strength and plasticity.

[0019] The present invention TiNbVAlSi x High entropy alloys are prepared by laser directed energy deposition additive manufacturing. When Si is not added, the alloy consists of disordered BCC phase and ordered B2 phase, showing lower yield strength and specific strength. The addition of Si promotes the 5 Si 3 phase precipitates at the grain boundary and in the grain, forming disordered BCC phase, ordered B2 phase and nano-Ti 5 Si 3 The microstructure characteristics of the phase and nano-Ti 5 Si 3 The phase content is proportional to the Si content. The yield strength and specific strength of the alloy increase from 660MPa and 120MPa·cm 3 / g increased to 936MPa and 171MPa·cm 3 / g. This lightweight and high-strength performance feature can meet the requirements of some aerospace devices, which is of great value to the development and application of TiNbVAl and related lightweight refractory high-entropy alloy systems.

[0020] Compared with the prior art, the advantages and beneficial effects of the present invention are as follows:

[0021] 1. The present invention utilizes the laser directed energy deposition (L-DED) in-situ alloying method for sample preparation, which can quickly and simultaneously prepare samples with different Si contents, reflecting the advantages of L-DED high-throughput sample preparation and saving time and cost.

[0022] 2. The present invention designs a series of Si-doped TiNbVAl high entropy alloys to form nano-scale Ti 5 Si 3 The precipitated phase effectively improves the specific strength of the refractory high entropy alloy, while the alloy maintains good plastic deformation ability. This idea has important reference value for the development and application of nano-precipitated phase strengthened Ti-Nb-V-Al lightweight refractory high entropy alloy system.

[0023] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention and implement it according to the contents of the specification, the following is a detailed description of the preferred embodiments of the present invention in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The X-ray diffraction (XRD) diagrams of Examples 1 to 5 of the present invention are shown in FIG. 2. In the diagram, the horizontal axis 2θ is the diffraction angle (degree), and the vertical axis intensity is the relative intensity (au).

[0025] Figure 2 The room temperature engineering stress-strain curves of Examples 1 to 5 of the present invention are shown in FIG.

[0026] Figure 3 The scanning electron micrographs of the XY plane in Examples 2 to 5 of the present invention are shown in FIG. 1 , wherein (a) is Example 2, (b) is Example 3, (c) is Example 4, and (d) is Example 5.

[0027] Figure 4 The transmission characterization diagram of the nano-precipitate phase of Example 5 of the present invention, wherein (a) is the high angle annular dark field (HAADF) phase of the nano-precipitate phase, and (b) is the line scan along the arrow direction in (a).

[0028] Figure 5 The following are the room temperature tensile fracture morphology images of Examples 2 to 5 of the present invention, wherein (a) is Example 2, (b) is Example 3, (c) is Example 4, and (d) is Example 5. DETAILED DESCRIPTION

[0029] The following is a more detailed description of the specific implementation of the present invention in conjunction with the accompanying drawings and examples, so that the scheme of the present invention and its advantages in various aspects can be better understood. However, the specific implementation and examples described below are only for the purpose of illustration, rather than for limiting the present invention.

[0030] In a specific implementation process, the present invention provides an additive manufacturing nano-precipitation phase strengthened refractory TiNbVAlSi x High entropy alloy, the chemical composition, microstructure and specific preparation technology of the alloy are as follows:

[0031] 1. The chemical composition of the high entropy alloy is as follows, in terms of atomic percentage:

[0032] Ti: 45-55%; Nb: 15-25%; V: 15-25%; Al: 8-15%; Si: 0-9%.

[0033] 2. The microstructural characteristics of the high entropy alloy are described as follows:

[0034] (1) When Si is not added, the alloy consists of a disordered BCC phase and a dispersed ordered B2 phase;

[0035] (2) When Si is added, the alloy consists of disordered BCC phase, ordered B2 phase, and Ti dispersed in the crystal. 5 Si 3 phase, and Ti precipitated at grain boundaries 5 Si 3 Phase composition.

[0036] 3. The preparation process of the high entropy alloy includes the following steps:

[0037] (1) Ti 50 Nb 20 V 20 Al 10 The pre-alloyed powder and irregular Si powder were mixed with a powder mixer for 3 hours to make them uniformly mixed; in the obtained mixed powder, the atomic ratio of Si powder was 7% and the mass ratio was 3.66%.

[0038] (2) The mixed powder and a certain amount of pre-alloyed powder are placed in a drying oven and dried at 80° C. for 3 h to remove moisture and ensure fluidity.

[0039] (3) The dried mixed powder and pre-alloyed powder were placed in two powder barrels (powder barrels 1# and 2#), and samples with different Si contents were prepared by laser directed energy deposition in-situ alloying method. The laser power used was 700 W and the scanning speed was 300 mm / min.

[0040] Table 1 Alloy chemical composition (at.%)

[0041] Ti Nb V Al Si Example 1 51.51 19.09 19.11 10.29 0 Example 2 49.24 19.68 20.03 9.68 1.37 Example 3 48.65 19.52 19.48 10.26 2.09 Example 4 49.02 19.08 19.29 9.59 3.02 Example 5 47.49 18.91 19.19 9.31 5.10

[0042] Table 2 Room temperature mechanical properties of high entropy alloys according to the present invention

[0043] Yield strength (MPa) Tensile strength(MPa) Elongation(%) Example 1 720 733 36.6 Example 2 936 937 15.1 Example 3 942 943 11.3 Example 4 1098 1105 2.08 Example 5 - 1209 1.02

[0044] like Figure 1 As shown, Examples 1 to 3 are all BCC single-phase structures, and Examples 4 and 5 both have Ti 5 Si 3 Diffraction peaks. Figure 3 As shown, the matrix of Examples 2 to 5 is all BCC phase, and nanophases are precipitated in the grains and grain boundaries, with a size of about 200nm. As the Si content increases, the nanophase gradually changes from discontinuous distribution to continuous distribution at the grain boundaries, and also exhibits a partial layered structure. Figure 4 As shown, the nanophase is rich in Ti and Si elements and poor in V element. Combining XRD pattern and diffraction analysis, it can be judged that the nanophase precipitated is Ti 5 Si 3 Phase, intracrystalline Ti 5 Si 3 The average size of the phase is 220 nm.

[0045] The sample was subjected to room temperature tensile test along the deposition direction, and the engineering stress-strain curve was as follows: Figure 2 As shown in Table 2, the room temperature mechanical properties are listed in Table 2. With the increase of Si element content, the yield strength of the embodiment of the present invention increases from 720MPa to 1098MPa, and the tensile strength increases from 733MPa to 1209MPa. By reasonably adding Si elements, the specific strength of the alloy can be effectively improved while ensuring a certain plasticity (Example 3).

[0046] like Figure 5 As shown, Example 2 is mainly a mixed fracture consisting of dimple plastic fracture and cleavage fracture, Example 3 has a reduced dimple ratio, Example 4 is mainly a cleavage brittle fracture, and Example 5 has a brittle fracture with loss of plasticity, which is consistent with the mechanical property results.

[0047] The implementation results show that the present invention introduces Si element on the basis of single-phase BCC TiNbVAl alloy and prepares TiNbVAlSi high entropy alloy by laser directional energy deposition technology. According to the records of the embodiment, within the range of Ti 48.65-49.24at.%, Nb19.52-19.68at.%, V 19.48-20.03at.%, Al 9.68-10.26at.%, Si1.37-2.09at.%, the yield strength reaches 936-942MPa, the tensile strength reaches 937-943MPa, and the elongation reaches 11.3-15.1%. The structure of the high entropy alloy is BCC matrix and Ti 5 Si 3 Nano-precipitated phase composition achieves a good balance of strength and plasticity. In particular, when the Si content is around 1.37%, the yield strength is 936MPa and the specific strength is 171.6MPa·cm3 / g, the tensile strain can be maintained above 15%. Under the premise of maintaining a certain plasticity, the specific strength of TiNbVAl alloys is greatly improved, which has important reference and value for the development and application of high entropy alloys and light alloys in TiNbVAl and related alloy systems.

[0048] The embodiments are preferred implementations of the present invention, but the present invention is not limited to the above-mentioned implementations. Any obvious improvements, substitutions or modifications that can be made by those skilled in the art without departing from the essential content of the present invention belong to the protection scope of the present invention.

Claims

1. An additive manufacturing nano-precipitation phase strengthened refractory TiNbVAlSi x A high entropy alloy, characterized in that The chemical composition of the high entropy alloy is as follows in terms of atomic percentage: Ti: 45-55%; Nb: 15-25%; V: 15-25%; Al: 8-15%; Si: 0-9%.

2. The additive manufacturing nano-precipitation phase strengthened refractory TiNbVAlSi according to claim 1 x A high entropy alloy, characterized in that Preferably, Si: 1 to 3%.

3. The additive manufacturing nano-precipitation phase strengthened refractory TiNbVAlSi according to claim 1 x A high entropy alloy, characterized in that The powders are first mixed and baked, and then the high entropy alloy is prepared by using a laser directed energy deposition in-situ alloying method.

4. The additive manufacturing nano-precipitation phase strengthened refractory TiNbVAlSi according to claim 3 x A high entropy alloy, characterized in that When mixing and baking powder, 50 Nb 20 V 20 Al 10 The pre-alloyed powder and Si powder are mixed in a powder mixer for 3 to 5 hours, and the mixed powder is placed in a drying oven and dried at 70 to 100° C. for 1 to 5 hours.

5. The additive manufacturing nano-precipitation phase strengthened refractory TiNbVAlSi according to claim 3 x A high entropy alloy, characterized in that The process parameters of laser directed energy deposition are as follows: laser power is 500-1000W, and scanning speed is 300-600mm / min.

6. An additively manufactured nano-precipitated phase-reinforced refractory TiNbVAlSi according to any one of claims 1 to 5 x A high entropy alloy, characterized in that When Si element is not added, the high entropy alloy is composed of a disordered BCC phase and a dispersed ordered B2 phase.

7. The additive manufacturing nano-precipitation phase strengthened refractory TiNbVAlSi according to claim 6 x A high entropy alloy, characterized in that When Si element is not added, the yield strength of the high entropy alloy at room temperature is 700-760 MPa, the tensile strength is 800-836 MPa, and the elongation is 30-35%.

8. The additive manufacturing nano-precipitation phase strengthened refractory TiNbVAlSi according to any one of claims 1 to 5 x A high entropy alloy, characterized in that The addition of Si element promotes the precipitation of nano-precipitates in the high entropy alloy composed of disordered BCC + ordered B2 phase, and the content of precipitates is proportional to the content of Si element.

9. The additive manufacturing nano-precipitation phase strengthened refractory TiNbVAlSi according to claim 8 x A high entropy alloy, characterized in that The nano-precipitated phase is a Ti5Si3 phase, with an average size of 100-250 nm and a volume fraction of greater than 0 to 1.5%.

10. The additive manufacturing nano-precipitation phase strengthened refractory TiNbVAlSi according to claim 8 x A high entropy alloy, characterized in that After adding Si element, the yield strength of high entropy alloy at room temperature is increased to 924~1100MPa, the tensile strength is 928~1203MPa, and the elongation is 10~22%.

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