Method for preparing high-performance beryllium-aluminum alloy through in-situ growth method

Abstract

The invention provides a method for preparing a high-performance beryllium-aluminum alloy through an in-situ growth method, and relates to the technical field of beryllium-aluminum alloys. The method comprises the following steps: vacuumizing to a target vacuum degree; heating the crucible at a first heating rate until the beryllium raw material begins to melt, then stopping vacuumizing, continuously heating to a first target temperature, stirring and melting down for a preset time after all the raw materials are completely melted, then introducing air until the pressure in the furnace is increased by 10Pa, then stopping stirring and reacting for 15-20 minutes, so as to obtain a melt; a casting mold is arranged to be heated to a second target temperature at a second heating rate, then the melt is poured into the casting mold, and a cast ingot is obtained through air cooling; and turning the cast ingot to remove an oxide layer on the surface of the cast ingot to obtain the target beryllium-aluminum alloy. According to the method, a certain amount of air is introduced in the vacuum melting process to increase the oxygen content in a furnace, so that beryllium in molten liquid generates a certain amount of beryllium oxide, and the beryllium oxide serves as a strengthening phase of beryllium to enhance the strength and elastic modulus of the beryllium aluminum alloy.

Description

Technical Field

[0001] The invention belongs to the technical field of beryllium aluminum alloys, and in particular relates to a method for preparing high-performance beryllium aluminum alloys by an in-situ growth method. Background Art

[0002] Beryllium aluminum alloy is a dual-phase composite material with a high melting point difference. It combines the advantages of beryllium and aluminum and has many excellent properties such as low density, high specific strength, high specific stiffness, and good thermal stability. It has important applications in the nuclear industry, aviation, aerospace, computers, automobiles and other fields.

[0003] At present, there are three main production processes for beryllium aluminum alloy: precision casting, powder metallurgy and forging. The microstructures of beryllium aluminum alloys prepared by different preparation processes are significantly different, resulting in different properties of the alloys. Traditional casting processes often lead to coarse grains, which reduce the strength and ductility of the alloy. The melting point of beryllium (1289℃) and the melting point of aluminum (660℃) are quite different. During the casting process, the solidification temperature range of beryllium aluminum alloy is relatively wide (about 550℃), and it is difficult to compensate for the shrinkage of the molten metal, resulting in a large number of shrinkage holes and pores in the final product; the mutual solubility between beryllium and aluminum is very limited, and beryllium and aluminum exist independently. With the increase of aluminum content, aluminum is enriched at the interface of beryllium aluminum alloy, weakening the bonding force of the interface. Beryllium aluminum alloy has severe segregation, coarse grains and uneven microstructure, showing a high degree of orientation, which makes the beryllium aluminum alloy material low in strength and poor in toughness. Forged beryllium aluminum alloy can have better mechanical properties than cast alloys. It can be seen from the microstructure that the beryllium phase particles in the forged alloy are arranged linearly along the rolling direction, and the particles are obviously finer and more evenly distributed than those in the cast state. In the tensile test results, the modulus, tensile strength, yield strength, elongation and fracture toughness of the forged beryllium aluminum alloy are better than those of the cast beryllium aluminum alloy, but the forging process is prone to oxidation, and the toxicity of beryllium oxide is very high, making the production of beryllium aluminum alloy difficult. The powder metallurgy preparation method of beryllium aluminum alloy is to mix pure beryllium powder and pure aluminum powder in a certain proportion, first cold isostatic pressing, and then hot isostatic pressing. Since the uniformity of the two powders is difficult to ensure after mixing, it is easy to produce component segregation, resulting in unstable performance. Studies have shown that when sintering beryllium aluminum mixed powder to prepare beryllium aluminum alloy, beryllium oxide will inevitably be produced on the surface of the beryllium powder, which will inhibit the diffusion during the sintering process, making it difficult to densify the beryllium aluminum alloy and reducing its material properties.

[0004] Therefore, a new method for manufacturing beryllium aluminum alloy is urgently needed. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a method for preparing high-performance beryllium aluminum alloy by in-situ growth method. By adopting the in-situ growth method, a certain amount of air is introduced into the vacuum melting process to increase the oxygen content in the furnace so that the beryllium in the melt generates a certain amount of beryllium oxide. Beryllium oxide, as a strengthening phase of beryllium, improves the bonding strength of beryllium and aluminum by increasing the transition surface, thereby enhancing the strength and elastic modulus of the beryllium aluminum alloy.

[0006] The first aspect of the present invention provides a method for preparing a high-performance beryllium aluminum alloy by an in-situ growth method, the method comprising the following steps:

[0007] Step S1, placing a crucible containing beryllium raw material, aluminum raw material and trace element raw material in a vacuum melting furnace, turning on a vacuum pump, and evacuating to a target vacuum degree;

[0008] Step S2, setting the crucible to heat up at a first heating rate until the beryllium raw material begins to melt, then turning off the vacuum pump, continuing to heat up to the first target temperature, stirring and melting the beryllium raw material, the aluminum raw material and the trace element raw material for a preset time after they are completely melted, then introducing air until the pressure in the furnace rises by 10 Pa and then stopping, stirring and reacting for 15-20 minutes to obtain a melt;

[0009] Step S3, setting the casting mold to heat up to a second target temperature at a second heating rate, then pouring the melt into the casting mold, and air cooling to obtain an ingot;

[0010] Wherein, the second target temperature is lower than the first target temperature, and the temperature difference between the first target temperature and the second target temperature is 350-600°C;

[0011] Step S4, turning the ingot to remove the oxide layer on the surface of the ingot to obtain the target beryllium aluminum alloy.

[0012] According to the method for preparing high-performance beryllium aluminum alloy by in-situ growth method described in the first aspect of the present invention, in the step S1, the target vacuum degree is not greater than 5×10 -3 Pa.

[0013] According to the method for preparing high-performance beryllium aluminum alloy by in-situ growth method described in the first aspect of the present invention, in the step S2, the first heating rate is 400-600°C / h, and the first target temperature is 1350-1400°C.

[0014] According to the method for preparing high-performance beryllium aluminum alloy by in-situ growth method described in the first aspect of the present invention, in the step S2, the preset time for stirring and melting is 10-30 minutes.

[0015] According to the method for preparing high-performance beryllium aluminum alloy by in-situ growth method described in the first aspect of the present invention, in the step S3, the second heating rate is 400-600°C / h, and the second target temperature is 800-1000°C.

[0016] According to the method for preparing high-performance beryllium aluminum alloy by in-situ growth method described in the first aspect of the present invention, in the step S3, during pouring, the temperature of the melt is 1150-1250°C.

[0017] According to the method for preparing high-performance beryllium aluminum alloy by in-situ growth method described in the first aspect of the present invention, in the step S4, the turning thickness is 0.5-1 mm.

[0018] The second aspect of the present invention provides a beryllium aluminum alloy, which is prepared by the above-mentioned method for preparing a high-performance beryllium aluminum alloy by the in-situ growth method;

[0019] The beryllium aluminum alloy has a tensile strength of 310-340 MPa, a yield strength of 250-280 MPa, an elastic modulus of 210-230 Gpa, and an elongation of ≥3.5%.

[0020] According to the beryllium aluminum alloy described in the second aspect of the present invention, the beryllium aluminum alloy comprises, by mass percentage, 61-68% beryllium, 0.1-5% trace elements, and the balance being aluminum.

[0021] According to the beryllium aluminum alloy described in the second aspect of the present invention, the trace elements are silicon and / or nickel.

[0022] The solution proposed by the present invention has the following technical effects:

[0023] The present invention adopts an in-situ growth method to introduce a certain amount of air during the vacuum melting process to increase the oxygen content in the furnace so that the beryllium in the melt generates a certain amount of beryllium oxide. The beryllium oxide, as a strengthening phase of beryllium, improves the bonding strength of beryllium and aluminum by increasing the transition surface, thereby enhancing the strength and elastic modulus of the beryllium aluminum alloy. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0025] Figure 1 The figure is a schematic flow chart of a method for preparing high-performance beryllium aluminum alloy by an in-situ growth method in one embodiment of the present invention. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0027] In the first aspect of this embodiment, a method for preparing a high-performance beryllium aluminum alloy by in-situ growth is proposed, such as Figure 1 As shown, the method includes the following steps.

[0028] Step S1, placing a crucible containing beryllium raw material, aluminum raw material and trace element raw material in a vacuum melting furnace, turning on a vacuum pump, and evacuating to a target vacuum degree.

[0029] Step S2, setting the crucible to heat up at a first heating rate until the beryllium raw material begins to melt, then turning off the vacuum pump, continuing to heat up to the first target temperature, stirring and melting the beryllium raw material, aluminum raw material and trace element raw material for a preset time after they are completely melted, then introducing air until the pressure in the furnace rises by 10 Pa and then stopping, stirring and reacting for 15-20 minutes to obtain a melt.

[0030] Step S3, setting the casting mold to heat up to a second target temperature at a second heating rate, then pouring the melt into the casting mold, and air-cooling to obtain an ingot.

[0031] Step S4, turning the ingot to remove the oxide layer on the surface of the ingot to obtain the target beryllium aluminum alloy.

[0032] In this embodiment, a certain amount of air is introduced into the vacuum melting process by adopting the in-situ growth method to increase the oxygen content in the furnace so that the beryllium in the melt generates a certain amount of beryllium oxide. Beryllium oxide, as a strengthening phase of beryllium, improves the bonding strength of beryllium and aluminum by increasing the transition surface, thereby enhancing the strength and elastic modulus of the beryllium aluminum alloy.

[0033] In this embodiment, before the beryllium raw material begins to melt, the vacuum pump is always in an on state, so that as much volatile impurities in the raw material as possible can be removed from the vacuum melting furnace during the heating process, thereby improving the purity of the alloy and further enhancing the strength and elastic modulus of the alloy.

[0034] In step S1, a crucible containing beryllium raw material, aluminum raw material and trace element raw material is placed in a vacuum melting furnace, and a vacuum pump is turned on to evacuate to a target vacuum degree.

[0035] In some embodiments, in step S1, the target vacuum degree is no greater than 5×10 -3 Pa.

[0036] In some embodiments, the purity of the beryllium raw material is higher than 99.5 wt.%, the purity of the aluminum raw material is higher than 99.5 wt.%, and the purity of the trace element raw material is higher than 99.0 wt.%.

[0037] Specifically, the beryllium raw material is placed at the bottom of the crucible.

[0038] In step S2, the crucible is set to heat up at a first heating rate until the beryllium raw material begins to melt, then the vacuum pump is turned off, and the temperature is continued to rise to the first target temperature. After the beryllium raw material, aluminum raw material and trace element raw material are completely melted, they are stirred and melted for a preset time, and then air is introduced until the pressure in the furnace rises to 10Pa and then stopped. The reaction is stirred for 15-20 minutes to obtain a melt.

[0039] In some embodiments, in step S2, the first heating rate is 400-600°C / h, preferably 450-550°C / h; the first target temperature is 1350-1400°C, preferably 1370-1380°C.

[0040] In some embodiments, the stirring and melting is preset for 10-30 minutes to reduce the impurity content in the melt, thereby improving the strength and elastic modulus of the alloy.

[0041] In this embodiment, after a small amount of air is introduced, the melted beryllium reacts with oxygen in the air at high temperature to generate beryllium oxide. A small amount of beryllium oxide, as a strengthening phase of beryllium, improves the bonding strength of beryllium aluminum by increasing the transition surface, thereby enhancing the strength and elastic modulus of the beryllium aluminum alloy. It should be noted that oxygen cannot be used to replace air in this embodiment to avoid a large amount of beryllium being oxidized to beryllium oxide, which causes the performance of the beryllium aluminum alloy to decrease. At the same time, the reaction time of the molten liquid and air is controlled at 15-20 minutes so that the amount of beryllium oxide is controlled within an appropriate range.

[0042] In this embodiment, stirring is continued after the raw materials are melted, which can prevent local over-oxidation of the beryllium aluminum melt and fully mix the different raw materials.

[0043] In step S3, the casting mold is set to heat up to a second target temperature at a second heating rate, and then the melt is poured into the casting mold and air-cooled to obtain an ingot.

[0044] In some embodiments, in step S3, the second target temperature is lower than the first target temperature, and the temperature difference between the first target temperature and the second target temperature is 350-600°C.

[0045] In this embodiment, the mold is preheated and the temperature difference between the first target temperature and the second target temperature is limited to 350-600° C., so as to avoid the segregation of the components of the beryllium aluminum alloy and the occurrence of pores due to a large temperature difference between the melt and the mold during the pouring process.

[0046] In some embodiments, in step S3, the second heating rate is 400-600°C / h, preferably 450-550°C / h; the second target temperature is 800-1000°C, preferably 880-920°C.

[0047] In some embodiments, in step S3, during pouring, the temperature of the melt is 1150-1250°C, preferably 1170-1220°C.

[0048] In some embodiments, dry ice is added during the air cooling process to further accelerate the cooling rate of the melt to obtain an ingot.

[0049] In this embodiment, the beryllium aluminum alloy melt is cooled by air cooling. Compared with natural cooling, air cooling is a rapid cooling. On the one hand, rapid cooling can greatly limit the growth time of crystals, so that the grains have no time to grow and become smaller. The fine grains can improve the strength, hardness and toughness of the material. The increase in strength makes the material more reliable when bearing loads, and the improvement in toughness enables the beryllium aluminum alloy to better absorb energy when impacted or vibrated, avoiding sudden fracture, thereby improving the reliability and safety of the material. On the other hand, during the casting process, due to the difference in solubility of solute elements in liquid and solid, component segregation is prone to occur. Rapid cooling can reduce the diffusion time of solute elements and reduce the degree of segregation. The performance of materials with uniform composition is more stable, avoiding the problem of uneven performance caused by local composition differences.

[0050] In step S4, the ingot is turned to remove the oxide layer on the surface of the ingot to obtain the target beryllium aluminum alloy.

[0051] In some embodiments, in step S4, the turning thickness is 0.5-1 mm, preferably 0.6-0.8 mm.

[0052] In some embodiments, the beryllium aluminum alloy has a tensile strength of 310-340 MPa, a yield strength of 250-280 MPa, an elastic modulus of 210-230 Gpa, and an elongation of ≥3.5%.

[0053] In some embodiments, the beryllium aluminum alloy includes, by mass percentage, 61-68% beryllium, 0.1-5% trace elements, and the balance aluminum.

[0054] In some embodiments, the trace element is silicon and / or nickel.

[0055] A second aspect of this embodiment provides a beryllium aluminum alloy, wherein the beryllium aluminum alloy is prepared by the aforementioned method for preparing a high-performance beryllium aluminum alloy by the in-situ growth method;

[0056] The beryllium aluminum alloy has a tensile strength of 310-340 MPa, a yield strength of 250-280 MPa, an elastic modulus of 210-230 Gpa, and an elongation of ≥3.5%.

[0057] In some embodiments, the beryllium aluminum alloy includes, by mass percentage, 61-68% beryllium, 0.1-5% trace elements, and the balance is aluminum.

[0058] In some embodiments, the trace element is silicon and / or nickel.

[0059] Example 1

[0060] In the first step, a crucible containing beryllium raw material, aluminum raw material, and silicon and / or nickel raw material is placed in a vacuum melting furnace, and a vacuum pump is turned on to evacuate the furnace to a vacuum degree of no more than 5×10 -3 Pa. Among them, the purity of the beryllium raw material is higher than 99.5wt.%, the purity of the aluminum raw material is higher than 99.5wt.%, and the purity of the silicon and / or nickel raw material is higher than 99.0wt.%.

[0061] In the second step, the crucible is heated at a rate of 500°C / h until the beryllium raw material begins to melt, then the vacuum pump is turned off and the temperature is continued to rise to 1370°C. After the beryllium raw material, aluminum raw material, and silicon and / or nickel raw materials are completely melted, they are stirred and melted for 20 minutes. Air is then introduced until the pressure in the furnace rises by 10 Pa, then the pressure is stopped, and the reaction is stirred for 18 minutes to obtain a melt.

[0062] The third step is to set the casting mold to heat up to 900°C at a rate of 500°C / h, then pour the melt into the casting mold, and air-cool to obtain an ingot. During pouring, the temperature of the melt is 1200°C.

[0063] The fourth step is to turn the ingot to a thickness of 0.5-1 mm to remove the oxide layer on the surface of the ingot to obtain the target beryllium aluminum alloy.

[0064] Example 2

[0065] In the first step, a crucible containing beryllium raw material, aluminum raw material, and silicon and / or nickel raw material is placed in a vacuum melting furnace, and a vacuum pump is turned on to evacuate the furnace to a vacuum degree of no more than 5×10 -3 Pa. Among them, the purity of the beryllium raw material is higher than 99.5wt.%, the purity of the aluminum raw material is higher than 99.5wt.%, and the purity of the silicon and / or nickel raw material is higher than 99.0wt.%.

[0066] In the second step, the crucible is heated at a rate of 400°C / h until the beryllium raw material begins to melt, then the vacuum pump is turned off and the temperature is continued to rise to 1350°C. After the beryllium raw material, aluminum raw material, and silicon and / or nickel raw materials are completely melted, they are stirred for 10 minutes. Air is then introduced until the pressure in the furnace rises by 10 Pa, then the pressure is stopped, and the reaction is stirred for 20 minutes to obtain a melt.

[0067] The third step is to set the casting mold to heat up to 800°C at a rate of 400°C / h, then pour the melt into the casting mold, and air-cool to obtain an ingot. During pouring, the temperature of the melt is 1150°C.

[0068] The fourth step is to turn the ingot to a thickness of 0.5-0.7 mm to remove the oxide layer on the surface of the ingot to obtain the target beryllium aluminum alloy. The beryllium aluminum alloy includes 61-68% beryllium, 0.1-5% silicon and / or nickel, and the balance is aluminum, by mass percentage.

[0069] Example 3

[0070] In the first step, a crucible containing beryllium raw material, aluminum raw material, and silicon and / or nickel raw material is placed in a vacuum melting furnace, and a vacuum pump is turned on to evacuate the furnace to a vacuum degree of no more than 5×10 -3 Pa. Among them, the purity of the beryllium raw material is higher than 99.5wt.%, the purity of the aluminum raw material is higher than 99.5wt.%, and the purity of the silicon and / or nickel raw material is higher than 99.0wt.%.

[0071] In the second step, the crucible is heated at a rate of 600°C / h until the beryllium raw material begins to melt, then the vacuum pump is turned off and the temperature is continued to rise to 1400°C. After the beryllium raw material, aluminum raw material, and silicon and / or nickel raw materials are completely melted, the mixture is stirred for 30 minutes, and then air is introduced until the pressure in the furnace rises by 10 Pa, then the mixture is stopped and stirred for 15 minutes to obtain a melt.

[0072] The third step is to set the casting mold to heat up to 1000°C at a rate of 600°C / h, then pour the melt into the casting mold, and air-cool to obtain an ingot. During pouring, the temperature of the melt is 1250°C.

[0073] The fourth step is to turn the ingot to a thickness of 0.7-1 mm to remove the oxide layer on the surface of the ingot to obtain the target beryllium aluminum alloy. The beryllium aluminum alloy includes 61-68% beryllium, 0.1-5% silicon and / or nickel, and the balance is aluminum, by mass percentage.

[0074] After testing, the properties of the target beryllium aluminum alloy manufactured by the methods of Examples 1-3 are shown in Table 1.

[0075] Table 1

[0076]

[0077] It can be seen from Table 1 that the beryllium aluminum alloy obtained by the method of the present invention has good strength and elastic modulus.

[0078] In summary, the solution proposed by the present invention has the following technical effects:

[0079] The present invention adopts an in-situ growth method to introduce a certain amount of air during the vacuum melting process to increase the oxygen content in the furnace so that the beryllium in the melt generates a certain amount of beryllium oxide. The beryllium oxide, as a strengthening phase of beryllium, improves the bonding strength of beryllium and aluminum by increasing the transition surface, thereby enhancing the strength and elastic modulus of the beryllium aluminum alloy.

[0080] Please note that the technical features of the above embodiments can be combined arbitrarily. In order to make the description concise, all possible combinations of the technical features in the above embodiments are not described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification. The above embodiments only express several implementation methods of the present application, and their descriptions are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that for ordinary technicians in this field, without departing from the concept of the present application, several variations and improvements can be made, which all belong to the scope of protection of the present application. Therefore, the scope of protection of the patent in this application shall be based on the attached claims.

Claims

1. A method for preparing high-performance beryllium aluminum alloy by in-situ growth method, characterized in that: The method comprises the following steps: Step S1, placing a crucible containing beryllium raw material, aluminum raw material and trace element raw material in a vacuum melting furnace, turning on a vacuum pump, and evacuating to a target vacuum degree; Step S2, setting the crucible to heat up at a first heating rate until the beryllium raw material begins to melt, then turning off the vacuum pump, continuing to heat up to the first target temperature, stirring and melting the beryllium raw material, the aluminum raw material and the trace element raw material for a preset time after they are completely melted, then introducing air until the pressure in the furnace rises by 10 Pa and then stopping, stirring and reacting for 15-20 minutes to obtain a melt; Step S3, setting the casting mold to heat up to a second target temperature at a second heating rate, then pouring the melt into the casting mold, and air cooling to obtain an ingot; Wherein, the second target temperature is lower than the first target temperature, and the temperature difference between the first target temperature and the second target temperature is 350-600°C; Step S4, turning the ingot to remove the oxide layer on the surface of the ingot to obtain the target beryllium aluminum alloy.

2. The method for preparing high-performance beryllium aluminum alloy by in-situ growth method according to claim 1, characterized in that: In step S1, the target vacuum degree is not greater than 5×10 -3 Pa.

3. The method for preparing high performance beryllium aluminum alloy by in-situ growth method according to claim 1, characterized in that: In the step S2, the first heating rate is 400-600°C / h, and the first target temperature is 1350-1400°C.

4. The method for preparing high performance beryllium aluminum alloy by in-situ growth method according to claim 1, characterized in that: In the step S2, the stirring and melting is preset for 10-30 minutes.

5. The method for preparing high performance beryllium aluminum alloy by in-situ growth method according to claim 1, characterized in that: In the step S3, the second heating rate is 400-600°C / h, and the second target temperature is 800-1000°C.

6. The method for preparing high performance beryllium aluminum alloy by in-situ growth method according to claim 1, characterized in that: In the step S3, during pouring, the temperature of the melt is 1150-1250°C.

7. The method for preparing high performance beryllium aluminum alloy by in-situ growth method according to claim 1, characterized in that: In the step S4, the turning thickness is 0.5-1 mm.

8. A beryllium aluminum alloy, characterized in that: The beryllium aluminum alloy is prepared by the method for preparing high-performance beryllium aluminum alloy by the in-situ growth method described in any one of claims 1 to 7; The beryllium aluminum alloy has a tensile strength of 310-340 MPa, a yield strength of 250-280 MPa, an elastic modulus of 210-230 Gpa, and an elongation of ≥3.5%.

9. The beryllium aluminum alloy according to claim 8, characterized in that: The beryllium aluminum alloy comprises, by mass percentage, 61-68% beryllium, 0.1-5% trace elements, and the balance aluminum.

10. The beryllium aluminum alloy according to claim 9, characterized in that: The trace elements are silicon and / or nickel.

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