A Hf-Nb-Zr-V refractory high-entropy alloy and preparation method thereof

Abstract

The application discloses an Hf-Nb-Zr-V refractory high-entropy alloy and a preparation method thereof, and belongs to the technical field of metal materials. The application comprises the following steps: (1) weighing Hf, Nb, Zr and V raw materials according to a designed proportion; (2) placing Hf and Nb into a copper crucible in a sequence of low melting point first and high melting point last to perform smelting, and obtaining Hf-Nb pre-alloy ingots; (3) placing Zr and V into the copper crucible in a sequence of low melting point first and high melting point last to perform smelting, and obtaining Zr-V pre-alloy ingots; and (4) placing the Hf-Nb pre-alloy ingots in the step (2) and the Zr-V pre-alloy ingots in the step (3) into the copper crucible to perform smelting under an argon environment, and obtaining the Hf-Nb-Zr-V refractory high-entropy alloy. The alloy prepared by the application breaks through the limitation of the traditional high-entropy alloy composition element type requirement, reduces the alloy preparation cost by reducing the alloy composition element type, and still ensures excellent room temperature performance of the alloy on the basis of reducing the alloy composition element type, and expands the application range of the alloy.

Description

Technical Field

[0001] The present invention belongs to the technical field of metal materials and relates to a Hf-Nb-Zr-V refractory high entropy alloy and a preparation method thereof. Background Art

[0002] High-entropy alloys are different from traditional engineering alloys. They are a series of complex alloys with a simple solid solution structure as the matrix, formed by mixing multiple elements in equimolar or near-equimolar proportions. These alloys contain at least five main elements.

[0003] The systems that have been developed so far can be roughly divided into two categories: one is high entropy alloys composed of period IV elements such as Fe, Co, and Ni. These elements have a high valence electron concentration, and the high entropy alloys formed by combination are mostly FCC structures; the other is refractory high entropy alloys (RHEAs) composed of high melting point elements such as W, Hf, Ta, and Nb. Because these high melting point elements have a low valence electron concentration, they are more likely to form BCC structures and high entropy alloys with higher melting points, often showing relatively excellent high temperature performance. However, their comprehensive performance at room temperature is relatively poor, such as NbCrMo 0.5 Ta 0.5 Although the compressive yield strength of TiZr alloy can reach 1595 MPa at room temperature, its elongation is only 5%.

[0004] Therefore, it is necessary to provide a Hf-Nb-Zr-V refractory high-entropy alloy and a preparation method thereof, breaking through the limitation on the number of types of main elements of the alloy, and still obtaining an alloy with good comprehensive performance at room temperature on the basis of fewer constituent elements. On the one hand, it reduces the alloy manufacturing cost, and on the other hand, it broadens the application range of the alloy, making it also have good applicability at room temperature. Summary of the Invention

[0005] In order to overcome the problems in the background technology, the present invention proposes a Hf-Nb-Zr-V refractory high-entropy alloy and a preparation method thereof. The alloy only requires four constituent elements. Compared with traditional high-entropy alloys, the number of constituent elements is reduced, and its manufacturing cost is also reduced. At the same time, on the basis of reducing the constituent elements, the comprehensive performance of the alloy at room temperature is improved.

[0006] In order to achieve the above object, the present invention is implemented through the following technical solutions:

[0007] In one aspect, the present invention provides a method for preparing a Hf-Nb-Zr-V refractory high entropy alloy, the preparation method comprising the following steps:

[0008] (1) Weigh Hf, Nb, Zr, and V raw materials according to the designed ratio.

[0009] (2) Hf and Nb are placed in a copper crucible in the order of low melting point at the bottom and high melting point at the top for smelting to obtain an Hf-Nb pre-alloyed ingot.

[0010] (3) Zr and V are placed in a copper crucible in the order of low melting point at the bottom and high melting point at the top for smelting to obtain a Zr-V pre-alloyed ingot.

[0011] (4) The Hf-Nb pre-alloyed ingot in step (2) and the Zr-V pre-alloyed ingot in step (3) are placed in the same crucible and smelted in an argon environment to obtain a Hf-Nb-Zr-V refractory high entropy alloy.

[0012] Preferably, the purity of Hf, Nb, Zr and V in the raw materials is above 99.5 wt%.

[0013] Preferably, among the raw materials, Hf, Zr and V are cylindrical particles, and Nb is flaky particles.

[0014] Preferably, in step (2) and step (3), the melting is reversed for no less than 2 times.

[0015] Preferably, in step (4), the pre-alloyed ingot is smelted at least 15 times.

[0016] Preferably, in step (4), a vacuum arc furnace is used to carry out arc melting on the pre-alloyed ingot, and the vacuum degree is 1×10 -4 ~5×10 -4 Pa, filled with high-purity argon gas to 0.03 ~ 0.05MPa.

[0017] Another aspect of the present invention provides a Hf-Nb-Zr-V alloy prepared by the above preparation method, wherein the atomic ratio of the constituent elements in the alloy is Hf:Nb:Zr:V=1:1:1:1.

[0018] Preferably, in the alloy, each constituent element has the same crystal structure.

[0019] Beneficial effects of the present invention:

[0020] 1. The present invention reduces the number of elements in the alloy, breaking through the limitation of traditional high-entropy alloys that they must contain no less than five elements, and can significantly reduce the overall cost of alloy manufacturing.

[0021] 2. The present invention places the metal with a low melting point at the bottom and the metal with a high melting point at the top, and first melts them to obtain a pre-alloyed ingot, and then melts the pre-alloyed ingot to obtain the final alloy. The method is simple and easy, and the prepared alloy has good room temperature performance.

[0022] 3.The alloy of the present application has both BBC phase and Laves phase, and the yield strength at room temperature can reach 1428 MPa, the compressive strength can reach 1721 MPa, and the strain energy can reach 18.1%.

[0023] 4.The present application reduces the types of constituent elements in the alloy, so that the constituent elements in the alloy have the same crystal structure, which is beneficial to improve the room temperature performance of the alloy. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 The XRD pattern of the alloy of the present application, wherein the horizontal coordinate 2theta (degrees) represents the diffraction angle (degrees) and the vertical coordinate intensity represents the intensity (a.u.).

[0025] Figure 2 The scanning electron microscope image of the alloy of the present application.

[0026] Figure 3 The energy spectrum picture of the alloy of the present application.

[0027] Figure 4 The room temperature compressive stress-strain curve of the alloy of the present application. DETAILED DESCRIPTION

[0028] The present application will be further described in detail below in combination with specific examples.

[0029] In the examples and comparative examples of the present application, commercially available analytical pure chemicals are used for experiments.

[0030] Example 1

[0031] The Hf-Nb-Zr-V alloy is prepared by the following method in this example:

[0032] (1) Preparation of raw materials: when the alloy is prepared, four kinds of metal raw materials of Hf, Zr, V and Nb with a purity higher than 99.5wt.% are prepared. Among them, the raw materials Hf, Zr and V are cylindrical particles with a size of 3mm*3mm, and Nb is a flaky particle with a thickness of 1-6mm.

[0033] (2) First, the raw materials are pretreated: Hf, Nb, Zr and V are first cleaned with anhydrous ethanol for 15min, and then dried in a drying box (temperature 80℃, time 2 hours). After pretreatment, each raw material is accurately weighed according to the atomic ratio of Hf:Nb:Zr:V=1:1:1:1.

[0034] (3) Preparation of Hf-Nb pre-alloy ingot: the instrument used for the preparation of the pre-alloy ingot of the present application is a WCE300 type tungsten electrode magnetic control arc furnace, and the crucible used during melting is a water-cooled copper crucible.

[0035] Put the raw materials hafnium (Hf) and niobium (Nb) into the water-cooled copper crucible in the order of melting point from low to high, with the low melting point raw material at the bottom and the high melting point raw material at the top. Then, evacuate the arc furnace and wait until the vacuum reaches 5×10 -4 After reaching Pa, 0.05MPa of high-purity argon is filled in. There are multiple water-cooled copper crucibles in the arc furnace melting chamber. The arc gun of the arc furnace is aimed at the particles in the crucible to carry out arc melting. In addition to the crucible for molten metal of the present invention, the arc furnace melting chamber also contains a crucible containing titanium ingots. Before starting the alloy melting of the present invention, the arc gun is first aimed at the crucible containing the titanium ingot, and the titanium ingot is melted separately to absorb the residual oxygen in the furnace, further reduce the oxygen partial pressure, and prevent oxidation during the alloy melting process. The melting is carried out under argon protection, and the heating current is gradually increased from 20A to 150A. In order to ensure the uniformity of the chemical composition of the pre-alloyed ingot, the melting is turned at least twice.

[0036] (4) Preparation of Zr-V pre-alloyed ingots: The raw materials zirconium (Zr) and vanadium (V) were placed into a water-cooled copper crucible in the order of melting point from low to high, with the low melting point raw material placed at the bottom and the high melting point raw material placed at the top. The electric arc furnace was then evacuated until the vacuum reached 5×10 -4 After reaching 0.05 MPa of high-purity argon, the ingot is filled with 0.05 MPa of high-purity argon. First, the titanium ingot is melted separately in the arc furnace melting chamber to absorb residual oxygen in the furnace, further reducing the oxygen partial pressure and preventing oxidation during the alloy melting process. Melting is carried out under argon protection, and the heating current is gradually increased from 20A to 150A. To ensure the uniformity of the chemical composition of the pre-alloyed ingot, the melting is turned at least twice.

[0037] (5) Place the Hf-Nb pre-alloyed ingot and the Zr-V pre-alloyed ingot into a water-cooled copper crucible, and then evacuate the arc furnace until the vacuum reaches 5×10 -4 After reaching 0.05 MPa of high-purity argon, the titanium ingot is first melted separately in the arc furnace melting chamber to absorb residual oxygen in the furnace, further reducing the oxygen partial pressure and preventing oxidation during the alloy melting process. Melting is carried out under argon protection, and the heating current is gradually increased from 20A to 150A. To ensure the uniformity of the chemical composition of the final alloy, the melting process is repeated at least 15 times.

[0038] After the alloy smelting is completed, the furnace body is cooled and then filled with air. The cavity is opened and the alloy ingot is taken out to obtain the cast alloy. The chemical composition of the alloy is shown in Table 1.

[0039] Table 1 Chemical composition of Hf-Nb-Zr-V alloy (at.%)

[0040] area Hf Nb Zr V Overall ingredients 24.7 25.2 25.6 24.5

[0041] The properties of the alloy prepared in this example were tested:

[0042] ①X-ray diffraction analysis of the alloy phase structure:

[0043] Blocks measuring 2 × 5 × 10 mm were cut from the alloy ingot using wire cutting and rapid sawing. The blocks were then polished using 400#, 800#, 1000#, and 2000# sandpaper, cleaned with alcohol, and dried with cold air. XRD analysis was performed using an XPert Pro diffractometer with a 2θ range of 20–80° and a scanning speed of 6° / min. The results are shown in Figure 2. Figure 1 shown.

[0044] pass Figure 1 It can be seen that according to the lattice diffraction extinction law, the three diffraction peaks in the spectrum correspond to the (110), (200), and (211) crystal planes of the BCC structural phase, indicating that the prepared refractory high entropy alloy is mainly composed of BCC phase; in addition, two diffraction peaks appear near the (110) peak (marked with diamonds in the figure) as diffraction peaks corresponding to Laves, indicating that Laves phase exists in the refractory high entropy alloy. The generation of Laves phase is due to the presence of a higher atomic ratio of Zr and V elements in the alloy, which increases the enthalpy value of the alloy, thereby causing the instability of the BCC phase and producing the typical C14 Laves phase compound ZrV 2， The phase structure in the alloy system changes to a BCC+Laves phase dominated by the BCC phase. Compared with the single BCC phase, the presence of the composite phase structure gives the alloy both higher strength and strain resistance, and better overall performance.

[0045] ② Scanning electron microscope (SEM) tissue observation:

[0046] A 2×5×10mm block was cut from the alloy ingot as a sample for SEM observation. The sample was polished with 400#, 800#, 1000#, 2000# and 3000# metallographic sandpaper in sequence, and then mechanically polished with 0.1μm and 0.05μm alumina polishing liquid. The sample was then ultrasonicated with alcohol for 30 minutes and dried for later use. The SEM model was FEIXL30. The SEM results are shown in Figure 2. Figure 2 shown.

[0047] pass Figure 2 It can be seen that the alloy is composed of BCC and Laves phases, and the microstructure is a typical cast dendritic structure.

[0048] ③ Alloy energy spectrum analysis:

[0049] The alloy was subjected to 3EDS energy spectrum analysis, and the results were as follows: Figure 3 shown.

[0050] pass Figure 3It can be seen that Hf, Nb, Zr, and V are distributed relatively evenly in the alloy, with no obvious segregation. The dendrite phase is mainly Nb, with a slight enrichment of Hf. The interdendritic phase is mainly rich in Zr and V.

[0051] ④Analysis of alloy mechanical properties

[0052] The sample size for room temperature mechanical properties analysis was Φ3mm×6mm, and the cylindrical end surface was polished flat with metallographic sandpaper. The room temperature compression test was performed using an Instron 5582 electronic universal testing machine with a strain rate of 1×10 -3 / s, the test was carried out using 3 parallel samples. Figure 4 shown.

[0053] pass Figure 4 It can be seen that the yield strength of the alloy is 1428 MPa, the compressive strength is 1721 MPa, and the strain is 18.1%. The Hf-Nb-Zr-V alloy prepared by the present invention has excellent comprehensive properties.

[0054] Example 2

[0055] In this embodiment, the Hf-Nb-Zr-V alloy is prepared by the following method:

[0056] (1) Raw material preparation: When preparing the alloy, prepare four metal raw materials: Hf, Zr, V, and Nb with a purity greater than 99.5 wt.%. The raw materials Hf, Zr, and V are in the form of 3 mm x 3 mm cylindrical particles, and Nb is in the form of flake particles with a thickness of 1 to 6 mm.

[0057] (2) First, the raw materials were pretreated: Hf, Nb, Zr, and V were ultrasonically cleaned with anhydrous ethanol for 15 min and then dried in a drying oven (temperature 80°C, time 2 h). After pretreatment, each raw material was accurately weighed according to the atomic ratio of Hf:Nb:Zr:V = 1:1:1:1.

[0058] (3) Preparation of Hf-Nb pre-alloyed ingots: The apparatus used for preparing the pre-alloyed ingots of the present invention is a WCE300 tungsten pole magnetron arc furnace, and the crucible used for smelting is a water-cooled copper crucible.

[0059] The raw materials hafnium (Hf) and niobium (Nb) are placed into a water-cooled copper crucible in the order of melting point from low to high, with the low melting point raw material at the bottom and the high melting point raw material at the top. Then the arc furnace is evacuated until the vacuum reaches 1×10 -4After reaching 0.03 MPa of high-purity argon, the ingot is filled with 0.03 MPa of high-purity argon. First, the titanium ingot is melted separately in the arc furnace melting chamber to absorb residual oxygen in the furnace, further reducing the oxygen partial pressure and preventing oxidation during the alloy melting process. Melting is carried out under argon protection, and the heating current is gradually increased from 20A to 150A. To ensure the uniformity of the chemical composition of the pre-alloyed ingot, the melting is turned at least twice.

[0060] (4) Preparation of Zr-V pre-alloyed ingots: The raw materials zirconium (Zr) and vanadium (V) were placed into a water-cooled copper crucible in the order of melting point from low to high, with the low melting point raw material placed at the bottom and the high melting point raw material placed at the top. The electric arc furnace was then evacuated until the vacuum reached 1×10 -4 After reaching 0.03 MPa of high-purity argon, the ingot is filled with 0.03 MPa of high-purity argon. First, the titanium ingot is melted separately in the arc furnace melting chamber to absorb residual oxygen in the furnace, further reducing the oxygen partial pressure and preventing oxidation during the alloy melting process. Melting is carried out under argon protection, and the heating current is gradually increased from 20A to 150A. To ensure the uniformity of the chemical composition of the pre-alloyed ingot, the melting is turned at least twice.

[0061] (5) Place the Hf-Nb pre-alloyed ingot and the Zr-V pre-alloyed ingot into a water-cooled copper crucible, and then evacuate the arc furnace until the vacuum reaches 1×10 -4 After reaching 0.03 MPa of high-purity argon, the titanium ingot is first melted separately in the arc furnace melting chamber to absorb residual oxygen in the furnace, further reducing the oxygen partial pressure and preventing oxidation during the alloy melting process. Melting is carried out under argon protection, and the heating current is gradually increased from 20A to 150A. To ensure the uniformity of the chemical composition of the final alloy, the melting process is repeated at least 15 times.

[0062] The properties of the alloy prepared in this example are similar to those in Example 1.

[0063] Example 3

[0064] (1) Raw material preparation: When preparing the alloy, prepare four metal raw materials: Hf, Zr, V, and Nb with a purity greater than 99.5 wt.%. The raw materials Hf, Zr, and V are in the form of 3 mm x 3 mm cylindrical particles, and Nb is in the form of flake particles with a thickness of 1 to 6 mm.

[0065] (2) First, the raw materials were pretreated: Hf, Nb, Zr, and V were ultrasonically cleaned with anhydrous ethanol for 15 min and then dried in a drying oven (temperature 80°C, time 2 h). After pretreatment, each raw material was accurately weighed according to the atomic ratio of Hf:Nb:Zr:V = 1:1:1:1.

[0066] (3) Preparation of Hf-Nb pre-alloyed ingots: The apparatus used for preparing the pre-alloyed ingots of the present invention is a WCE300 tungsten pole magnetron arc furnace, and the crucible used for smelting is a water-cooled copper crucible.

[0067] Put the raw materials hafnium (Hf) and niobium (Nb) into the water-cooled copper crucible in the order of melting point from low to high, with the low melting point raw material at the bottom and the high melting point raw material at the top. Then evacuate the arc furnace and wait until the vacuum reaches 3×10 -4 After reaching 0.04 MPa of high-purity argon, the ingot is filled with 0.04 MPa of high-purity argon. First, the titanium ingot is melted separately in the arc furnace melting chamber to absorb residual oxygen in the furnace, further reducing the oxygen partial pressure and preventing oxidation during the alloy melting process. Melting is carried out under argon protection, and the heating current is gradually increased from 20A to 150A. To ensure the uniformity of the chemical composition of the pre-alloyed ingot, the melting is turned at least twice.

[0068] (4) Preparation of Zr-V pre-alloyed ingots: The raw materials zirconium (Zr) and vanadium (V) were placed into a water-cooled copper crucible in the order of melting point from low to high, with the low melting point raw material placed at the bottom and the high melting point raw material placed at the top. The electric arc furnace was then evacuated until the vacuum reached 3×10 -4 After reaching 0.04 MPa of high-purity argon, the ingot is filled with 0.04 MPa of high-purity argon. First, the titanium ingot is melted separately in the arc furnace melting chamber to absorb residual oxygen in the furnace, further reducing the oxygen partial pressure and preventing oxidation during the alloy melting process. Melting is carried out under argon protection, and the heating current is gradually increased from 20A to 150A. To ensure the uniformity of the chemical composition of the pre-alloyed ingot, the melting is turned at least twice.

[0069] (5) Place the Hf-Nb pre-alloyed ingot and the Zr-V pre-alloyed ingot into a water-cooled copper crucible, and then evacuate the arc furnace until the vacuum reaches 3×10 -4 After reaching 0.04 MPa of high-purity argon, the titanium ingot is first melted separately in the arc furnace melting chamber to absorb residual oxygen in the furnace, further reducing the oxygen partial pressure and preventing oxidation during the alloy melting process. Melting is carried out under argon protection, and the heating current is gradually increased from 20A to 150A. To ensure the uniformity of the chemical composition of the final alloy, the melting process is repeated at least 15 times.

[0070] The properties of the alloy prepared in this example are similar to those in Example 1.

[0071] Comparative Example 1

[0072] This comparative example uses the same method as Example 1 to prepare the alloy, except that: during the preparation of the alloy in this comparative example, no pre-alloy ingot melting is performed, and the metal with the lower melting point among the four metals is directly placed at the bottom, and the metal with the higher melting point is placed at the top.

[0073] Compared with the alloy in Example 1, the alloy prepared in this comparative example has a large performance difference between the melting points of the four elements and the large difference in the atomic radius of some elements, so they cannot be infinitely soluble in each other. If the melting point of the alloy is not indirectly lowered, the alloy cannot be melted uniformly.

[0074] Comparative Example 2

[0075] The alloy was prepared in this comparative example using the same method as in Example 1, with the difference that during the alloy preparation process in this comparative example, the metal with a lower melting point was placed on top, and the metal with a higher melting point was placed on the bottom.

[0076] The properties of the alloy prepared in this comparative example are compared with those in Example 1. Since the process of preparing the refractory high-entropy alloy according to the present invention requires rapid cooling, otherwise the cooling time is too long, which will have a certain negative impact on the final alloy properties. During the smelting process, there is a heat transfer and melting problem between the metals. The placement method in Comparative Example 2 will cause the low-melting-point component to completely melt and cover the high-melting-point components Nb and Hf that have not yet completely melted during the smelting process, resulting in the alloy being unable to be smelted uniformly.

[0077] Comparative Example 3

[0078] In this comparative example, the alloy was prepared by the same method as in Example 1, except that in this comparative example, the element V was replaced by the element Ti.

[0079] The alloy prepared in this comparative example exhibits comparable performance compared to Example 1. Ti, Zr, and Hf belong to the same main group IVB, and Zr and Nb are adjacent elements in the same period. These four elements have very similar atomic radii and are infinitely miscible with each other. Therefore, the resulting Hf-Nb-Zr-Ti refractory high-entropy alloy consists of a BCC phase. However, the substitution of Ti for V reduces the formation of the Laves phase, improving room-temperature plasticity. However, this significantly reduces the alloy's yield strength, preventing it from maintaining good overall room-temperature performance and negatively impacting its high-temperature performance.

[0080] In summary, the Hf-Nb-Zr-V alloy prepared by the preparation method of the present invention not only reduces the number of alloy components and reduces the alloy preparation cost, but also makes it easier for the components to have the same crystal structure. At the same time, on the basis of reducing the number of alloy components, the alloy still maintains relatively excellent room temperature performance.

[0081] Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made in form and details without departing from the scope defined by the claims of the present invention.

Claims

1. A method for preparing a Hf-Nb-Zr-V refractory high entropy alloy, characterized by: The preparation method comprises the following steps: (1) Weigh Hf, Nb, Zr, and V raw materials according to the designed ratio; (2) placing the raw materials Hf and Nb in a copper crucible in the order of lower melting point at the bottom and higher melting point at the top for smelting to obtain an Hf-Nb pre-alloyed ingot; (3) placing the raw materials Zr and V in a copper crucible in the order of lower melting point at the bottom and higher melting point at the top for smelting to obtain a Zr-V pre-alloyed ingot; (4) The Hf-Nb pre-alloyed ingot in step (2) and the Zr-V pre-alloyed ingot in step (3) are placed in the same crucible and smelted in an argon environment to obtain a Hf-Nb-Zr-V refractory high entropy alloy, wherein the Hf-Nb-Zr-V refractory high entropy alloy has both a BBC phase and a Laves phase.

2. The method for preparing a Hf-Nb-Zr-V refractory high entropy alloy according to claim 1, characterized in that: Among the raw materials, the purity of Hf, Nb, Zr and V is above 99.5wt%.

3. The method for preparing a Hf-Nb-Zr-V refractory high entropy alloy according to claim 1, wherein: Among the raw materials, Hf, Zr, and V are cylindrical particles, and Nb is flaky particles.

4. The method for preparing a Hf-Nb-Zr-V refractory high entropy alloy according to claim 1, wherein: In the steps (2) and (3), the smelting object is turned over at least twice during the smelting process.

5. The method for preparing a Hf-Nb-Zr-V refractory high entropy alloy according to claim 1, wherein: In the step (4), the pre-alloyed ingot is smelted at least 15 times.

6. The method for preparing a Hf-Nb-Zr-V refractory high entropy alloy according to claim 1, wherein: In the steps (2), (3) and (4), a vacuum arc furnace is used for arc melting, and the vacuum degree is 1×10 -4 ~5×10 -4 Pa, filled with high-purity argon gas to 0.03 ~ 0.05MPa.

7. The Hf-Nb-Zr-V refractory high entropy alloy prepared by the method for preparing a Hf-Nb-Zr-V refractory high entropy alloy according to any one of claims 1 to 6, characterized in that: In the alloy, the atomic ratio of each component element is Hf:Nb:Zr:V=1:1:1:1.

Images