Method for controlling solidification structure form of molybdenum-niobium-tungsten single-phase alloy

Abstract

The invention discloses a method for controlling the solidification structure form of a molybdenum-niobium-tungsten single-phase alloy, which comprises the following steps of: 1, mixing metal molybdenum, metal niobium and metal tungsten to prepare a metal mixture with an approximately equal atomic ratio; secondly, the metal mixture with the near-equal atomic ratio is subjected to multiple times of vacuum electromagnetic suspension smelting in the argon atmosphere, and high-temperature liquid alloy is obtained; and thirdly, the high-temperature liquid alloy is poured into a water-cooled copper crucible or a graphite clay crucible with auxiliary heating to be naturally cooled, and the molybdenum-niobium-tungsten single-phase alloy of the columnar crystal structure or the dendritic crystal structure is obtained. According to the method disclosed by the invention, the high-temperature liquid alloy is prepared by adopting a vacuum electromagnetic suspension smelting method, and water-cooled copper crucibles or graphite clay crucibles with different temperatures are used as casting containers, so that the cooling rate in the natural cooling process of the high-temperature liquid alloy can be controlled; and the structure form after solidification is controlled to be a dendritic crystal structure or a columnar crystal structure, and the method is suitable for the technical field of casting of multi-principal-element refractory alloy materials.

Description

Technical Field

[0001] The invention belongs to the technical field of multi-principal-element refractory alloy material casting, and in particular relates to a method for controlling the solidification structure morphology of a molybdenum-niobium-tungsten single-phase alloy. Background Art

[0002] Multi-principal component refractory alloys have become one of the research hotspots in the field of metal materials in recent years due to their high strength, corrosion resistance and radiation resistance. In the past, research on multi-principal component refractory alloys mainly focused on the regulation of alloy composition in order to optimize the organizational morphology and application performance. Studies have shown that single-phase, two-phase and multi-phase multi-principal component refractory alloys have different solidification organizational morphologies, and the same type of alloys with different element proportions will also form a variety of organizational morphologies. For single-phase multi-principal component refractory alloys, the current solidification organizational morphologies are dendritic and columnar. However, there is no determined solidification process for how to control the solidification process and produce a specific morphology of solidification organization.

[0003] The morphology of alloy solidification structure will affect the subsequent processing and determine the application performance of the material. Obtaining a specific morphology of solidification structure is crucial for the preparation of advanced materials. Among them, dendrite structure usually has serious microsegregation. Segregation of plastic elements at the dendrite boundary is beneficial to improving the plasticity of the alloy and subsequent plastic processing and forming. The columnar crystal structure itself has weak microsegregation and a more uniform structure, but the grains are usually coarse and the mechanical properties are poor.

[0004] Based on this, how to control the solidification process of multi-principal refractory alloys, produce dendritic and columnar structures under specific solidification process conditions, and provide organizational morphology selection space for subsequent alloy processing applications and performance optimization needs to be solved urgently. Summary of the invention

[0005] The purpose of the present invention is to overcome the deficiencies in the above-mentioned prior art and provide a method for controlling the solidification structure morphology of molybdenum, niobium and tungsten single-phase alloy. The method adopts vacuum electromagnetic levitation melting method to prepare high-temperature liquid alloy, and uses water-cooled copper crucibles or graphite clay crucibles with different initial temperatures as casting containers, which can control the cooling rate of high-temperature liquid alloy during natural cooling, and then control the structure morphology after solidification to be dendrite structure or columnar crystal structure, providing a space for the selection of structure morphology for subsequent molybdenum, niobium and tungsten alloy processing applications and performance optimization.

[0006] To achieve the above object, the technical solution adopted by the present invention is: a method for controlling the solidification structure morphology of molybdenum-niobium-tungsten single-phase alloy, characterized in that the method comprises the following steps:

[0007] Step 1: Mix metal molybdenum, metal niobium and metal tungsten to prepare a metal mixture with a nearly equal atomic ratio;

[0008] Step 2: subjecting the metal mixture with a nearly equal atomic ratio prepared in step 1 to multiple vacuum electromagnetic suspension melting in an argon atmosphere to obtain a high-temperature liquid alloy;

[0009] Step 3: Cast the high-temperature liquid alloy obtained in step 2 into a water-cooled copper crucible at 4°C to 15°C and cool it naturally to obtain a molybdenum-niobium-tungsten single-phase alloy with a columnar crystal structure, or cast the high-temperature liquid alloy obtained in step 2 into a graphite clay crucible at 25°C to 1000°C and cool it naturally to obtain a molybdenum-niobium-tungsten single-phase alloy with a dendrite structure.

[0010] The above-mentioned method for controlling the solidification structure morphology of molybdenum-niobium-tungsten single-phase alloy is characterized in that the atomic ratio of molybdenum, niobium and tungsten in the nearly equal atomic ratio metal mixture in step one is 30% to 35%.

[0011] The above method for controlling the solidification structure morphology of molybdenum-niobium-tungsten single-phase alloy is characterized in that the vacuum electromagnetic suspension melting in step 2 is performed for no less than 4 times, and the process of the vacuum electromagnetic suspension melting is: vacuumizing to 2.5×10 - 1 Pa~5.5×10 -3 Pa, filled with argon to a pressure of 4.5×10 1 Pa~5.5×10 3 Pa, and smelting is carried out for 5min to 10min.

[0012] The above-mentioned method for controlling the solidification structure morphology of molybdenum-niobium-tungsten single-phase alloy is characterized in that the temperature of the high-temperature liquid alloy in step 2 is 3600°C to 4000°C.

[0013] The present invention can control the cooling rate after casting by controlling the temperature of the high-temperature liquid alloy, thereby controlling the organizational morphology of the molybdenum-niobium-tungsten single-phase alloy after solidification.

[0014] The above method for controlling the solidification structure morphology of molybdenum-niobium-tungsten single-phase alloy is characterized in that the cooling rate of the high-temperature liquid alloy in the water-cooled copper crucible in step 3 is 6.3×10 5 ℃ / s~6.5×10 7 ℃ / s.

[0015] The above-mentioned method for controlling the solidification structure morphology of molybdenum-niobium-tungsten single-phase alloy is characterized in that the graphite clay crucible in step 3 has an auxiliary heating function, and the cooling rate of the high-temperature liquid alloy in the graphite clay crucible is 3.5×10 2 ℃ / s~4.2×10 4 ℃ / s.

[0016] The present invention adopts a graphite clay crucible with an auxiliary heating function, so as to accurately control the initial temperature of the crucible, control the cooling rate after casting, and further control the microstructure of the molybdenum-niobium-tungsten single-phase alloy after solidification.

[0017] Compared with the prior art, the present invention has the following advantages:

[0018] 1. The present invention adopts a vacuum electromagnetic levitation melting method to prepare a high-temperature liquid alloy. Compared with the prior art in which the liquid high-temperature alloy is cooled in a melting crucible by an arc furnace melting method, the vacuum electromagnetic levitation melting method can automatically flip the melting crucible, and the high-temperature liquid alloy can be cast into other containers for cooling and solidification. Crucibles with different initial temperatures and different materials can be used as casting containers to control the cooling rate of the high-temperature liquid alloy during natural cooling, thereby controlling the microstructure after solidification to be a dendrite structure or a columnar crystal structure, providing a space for microstructure selection for subsequent molybdenum-niobium-tungsten alloy processing, application and performance optimization.

[0019] 2. The present invention adopts a water-cooled copper crucible as a casting container for forming a columnar crystal structure. When the water-cooled copper crucible is naturally cooled in a room temperature environment, the temperature of the water-cooled copper crucible itself is adjusted to a relatively low temperature. Since the water-cooled copper crucible has a low initial temperature and a strong thermal conductivity, the high-temperature liquid alloy is rapidly cooled to form a columnar crystal structure. A graphite clay crucible with a heating function is adopted as a casting container for forming a dendrite structure. When the water-cooled copper crucible is naturally cooled in a room temperature environment, the graphite clay crucible is heated. Since the graphite clay crucible has a high initial temperature and a poor thermal conductivity, the high-temperature liquid alloy is slowly cooled to form a dendrite structure.

[0020] 3. The present invention adopts a vacuum electromagnetic suspension melting furnace to prepare high-temperature liquid alloy, and can produce kilogram-level solidified alloy. Compared with the existing technology that uses an arc melting furnace to prepare solidified alloys with a mass of dozens of grams, the output is effectively improved.

[0021] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a microstructure diagram of the molybdenum-niobium-tungsten single-phase alloy obtained in Example 1 of the present invention.

[0023] Figure 2 This is a characteristic diagram of element distribution of the molybdenum-niobium-tungsten single-phase alloy obtained in Example 1 of the present invention.

[0024] Figure 3 This is a microstructure diagram of the molybdenum-niobium-tungsten single-phase alloy obtained in Example 2 of the present invention.

[0025] Figure 4This is a characteristic diagram of element distribution of the molybdenum-niobium-tungsten single-phase alloy obtained in Example 2 of the present invention. DETAILED DESCRIPTION

[0026] Example 1

[0027] The method of this embodiment includes the following steps:

[0028] Step 1: Mix metal molybdenum, metal niobium and metal tungsten to prepare a metal mixture with a nearly equal atomic ratio; the atomic ratio of molybdenum, niobium and tungsten in the metal mixture with a nearly equal atomic ratio is 33.3%;

[0029] Step 2: subjecting the metal mixture prepared in step 1 to 12 times of vacuum electromagnetic levitation melting in an argon atmosphere to obtain a 3800° C. high-temperature liquid alloy;

[0030] Step 3: Cast the high-temperature liquid alloy obtained in step 2 into a water-cooled copper crucible at 10°C and 6 The single-phase alloy of molybdenum, niobium and tungsten was obtained by natural cooling at a cooling rate of 1.5°C / s.

[0031] The microstructure of the molybdenum-niobium-tungsten single-phase alloy obtained in this embodiment is analyzed. Figure 1 As shown, the microstructure of the molybdenum-niobium-tungsten single-phase alloy is a columnar crystal structure. The element distribution analysis of the columnar crystal structure is as follows: Figure 2 As shown in the figure, there is no segregation of Mo, Nb and W elements in the columnar crystal structure, and their contents in the crystal and grain boundary regions are basically the same.

[0032] Example 2

[0033] The difference between this embodiment and embodiment 1 is that in step 3, the high-temperature liquid alloy is cast into a graphite clay crucible with auxiliary heating at 1000°C and heated at 3.5×10 2 The single-phase alloy of molybdenum, niobium and tungsten was obtained by natural cooling at a cooling rate of ℃ / s.

[0034] The microstructure of the molybdenum-niobium-tungsten single-phase alloy obtained in this embodiment is analyzed. Figure 3 As shown, the microstructure of the molybdenum-niobium-tungsten single-phase alloy is a dendrite structure; the element distribution analysis of the dendrite structure is performed, such as Figure 4 As shown, in the dendrite structure, the W element is concentrated in the grain and the content at the grain boundary is relatively low, while the Mo and Nb elements are concentrated in the grain boundary and the content in the grain is relatively low.

[0035] Example 3

[0036] The method of this embodiment includes the following steps:

[0037] Step 1: Mix metal molybdenum, metal niobium and metal tungsten to prepare a metal mixture with a nearly equal atomic ratio; the atomic ratios of the elements in the metal mixture with a nearly equal atomic ratio are: Mo 30%, Nb 35%, W 35%;

[0038] Step 2: subjecting the metal mixture prepared in step 1 to 12 times of vacuum electromagnetic levitation melting in an argon atmosphere to obtain a 4000° C. high-temperature liquid alloy;

[0039] Step 3: Cast the high-temperature liquid alloy obtained in step 2 into a water-cooled copper crucible at 4°C and 7 The single-phase alloy of molybdenum, niobium and tungsten was obtained by natural cooling at a cooling rate of 1.5°C / s.

[0040] After testing, it was found that the molybdenum-niobium-tungsten single-phase alloy obtained in this embodiment had a columnar crystal structure after solidification.

[0041] Example 4

[0042] The difference between this embodiment and embodiment 3 is that in step 3, the high-temperature liquid alloy is cast into a graphite clay crucible with auxiliary heating at 800°C and heated at 3.0×10 3 The single-phase alloy of molybdenum, niobium and tungsten was obtained by natural cooling at a cooling rate of ℃ / s.

[0043] It has been detected that the molybdenum-niobium-tungsten single-phase alloy obtained in this embodiment has a dendrite structure after solidification.

[0044] Example 5

[0045] The method of this embodiment includes the following steps:

[0046] Step 1: Mix metal molybdenum, metal niobium and metal tungsten to prepare a metal mixture with a nearly equal atomic ratio; the atomic ratios of the elements in the metal mixture with a nearly equal atomic ratio are: Mo 35%, Nb 30%, W 35%;

[0047] Step 2: subjecting the metal mixture prepared in step 1 to vacuum electromagnetic levitation melting for 10 times in an argon atmosphere to obtain a 3600° C. high-temperature liquid alloy;

[0048] Step 3: Cast the high-temperature liquid alloy obtained in step 2 into a water-cooled copper crucible at 15°C and 5 The single-phase alloy of molybdenum, niobium and tungsten was obtained by natural cooling at a cooling rate of 1.5°C / s.

[0049] After testing, it was found that the molybdenum-niobium-tungsten single-phase alloy obtained in this embodiment had a columnar crystal structure after solidification.

[0050] Example 6

[0051] The difference between this embodiment and embodiment 5 is that in step 3, the high-temperature liquid alloy is cast into a graphite clay crucible with auxiliary heating at 25°C and heated at 4.2×10 4 The single-phase alloy of molybdenum, niobium and tungsten was obtained by natural cooling at a cooling rate of ℃ / s.

[0052] It has been detected that the molybdenum-niobium-tungsten single-phase alloy obtained in this embodiment has a dendrite structure after solidification.

[0053] Example 7

[0054] The difference between this embodiment and embodiment 5 is that: the atomic ratios of the elements in the nearly equal atomic ratio metal mixture in step 1 are: Mo 35%, Nb 35%, W 30% respectively;

[0055] After testing, it was found that the molybdenum-niobium-tungsten single-phase alloy obtained in this embodiment had a columnar crystal structure after solidification.

[0056] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent structural transformation made to the above embodiment based on the technical essence of the present invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. A method for controlling the solidification structure morphology of a molybdenum-niobium-tungsten single-phase alloy, characterized in that: The method comprises the following steps: Step 1: Mix metal molybdenum, metal niobium and metal tungsten to prepare a metal mixture with a nearly equal atomic ratio; Step 2: subjecting the metal mixture with a nearly equal atomic ratio prepared in step 1 to multiple vacuum electromagnetic suspension melting in an argon atmosphere to obtain a high-temperature liquid alloy; Step 3: Cast the high-temperature liquid alloy obtained in step 2 into a water-cooled copper crucible at 4°C to 15°C and cool it naturally to obtain a molybdenum-niobium-tungsten single-phase alloy with a columnar crystal structure, or cast the high-temperature liquid alloy obtained in step 2 into a graphite clay crucible at 25°C to 1000°C and cool it naturally to obtain a molybdenum-niobium-tungsten single-phase alloy with a dendrite structure.

2. The method for controlling the solidification structure morphology of a molybdenum-niobium-tungsten single-phase alloy according to claim 1, characterized in that: In the nearly equal atomic ratio metal mixture in step 1, the atomic ratios of molybdenum, niobium and tungsten are all 30% to 35%.

3. The method for controlling the solidification structure morphology of a molybdenum-niobium-tungsten single-phase alloy according to claim 1, characterized in that: The vacuum electromagnetic suspension melting in step 2 is performed for no less than 4 times. The vacuum electromagnetic suspension melting adopts a vacuum electromagnetic suspension melting furnace. The process of the vacuum electromagnetic suspension melting is as follows: vacuumizing to 2.5×10 -1 Pa~5.5×10 -3 Pa, filled with argon to a pressure of 4.5×10 1 Pa~5.5×10 3 Pa, and smelting is carried out for 5min to 10min.

4. The method for controlling the solidification structure morphology of a molybdenum-niobium-tungsten single-phase alloy according to claim 1, characterized in that: The temperature of the high temperature liquid alloy in step 2 is 3600°C to 4000°C.

5. The method for controlling the solidification structure morphology of a molybdenum-niobium-tungsten single-phase alloy according to claim 1, characterized in that: The cooling rate of the high temperature liquid alloy in the water-cooled copper crucible in step 3 is 6.3×10 5 ℃ / s~6.5×10 7 ℃ / s.

6. The method for controlling the solidification structure morphology of a molybdenum-niobium-tungsten single-phase alloy according to claim 1, characterized in that: The graphite clay crucible in step 3 has an auxiliary heating function, and the cooling rate of the high-temperature liquid alloy in the graphite clay crucible is 3.5×10 2 ℃ / s~4.2×10 4 ℃ / s.

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