Regulation and control method for oxides in ODS molybdenum-rhenium alloy

Abstract

The invention discloses a method for regulating and controlling oxides in ODS molybdenum-rhenium alloy. The method comprises the steps that firstly, molybdenum powder, rhenium powder and nanometer yttrium oxide powder are mixed and then subjected to high-energy ball milling; 2, pressing in a mold to obtain an ODS molybdenum-rhenium alloy blank; and thirdly, SPS sintering is conducted in a gradient heating mode, and the ODS molybdenum-rhenium alloy is obtained. According to the method, high-energy ball milling is adopted for achieving introduction of defects such as solid solution, vacancy and dislocation of the oxide, sintering is conducted in a gradient heating mode, the introduced defects are utilized for promoting oxide particles to be highly dispersed and separated out during low-temperature sintering, the growth driving force of the oxide during high-temperature sintering is reduced, regulation and control over the oxide in the ODS molybdenum-rhenium alloy are achieved, and the service life of the oxide is prolonged. According to the method, oxide in the ODS molybdenum-rhenium alloy crystal is distributed in a dispersed mode, generation and segregation of large-size oxide particles with the size reaching the micron level at the grain boundary are eliminated, the mechanical property of the ODS molybdenum-rhenium alloy is improved, and the method is suitable for the field of molybdenum-rhenium alloys.

Description

Technical Field

[0001] The invention belongs to the technical field of molybdenum-rhenium alloy microstructure design, and particularly relates to a method for controlling oxides in an ODS molybdenum-rhenium alloy. Background Art

[0002] ODS molybdenum-rhenium alloy combines the advantages of molybdenum-rhenium alloys, such as good plasticity and toughness, with the high strength and excellent radiation resistance of ODS molybdenum. It is considered a promising candidate for nuclear reactor components such as space reactor heat pipes and fast reactor cladding. However, the strength and plasticity of ODS molybdenum-rhenium alloys are closely related to the size and distribution of oxides within the alloy. Current research suggests that stress concentration and crack initiation caused by the coarsening and agglomeration of oxide particles at alloy grain boundaries are major factors contributing to the reduced strength and plasticity of ODS molybdenum-rhenium alloys and shortened service life.

[0003] Therefore, how to effectively control the oxides in ODS molybdenum-rhenium alloy, especially the control of oxide size and distribution at grain boundaries, plays a vital role in improving its performance. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to address the shortcomings of the above-mentioned prior art and provide a method for controlling oxides in ODS molybdenum-rhenium alloys. This method uses high-energy ball milling to achieve solid solution of oxides and the introduction of defects such as vacancies and dislocations. Combined with sintering using a gradient temperature ramp, the method utilizes the introduced defects to promote the highly dispersed precipitation of oxide particles during low-temperature sintering and reduce the driving force for oxide growth during high-temperature sintering. This achieves the control of oxides in the ODS molybdenum-rhenium alloy, resulting in a dispersed distribution of oxides within the ODS molybdenum-rhenium alloy crystals and eliminating the formation and segregation of large oxide particles up to micrometers in size at grain boundaries. This method solves the problem of reduced strength and plasticity and shortened service life in existing ODS molybdenum-rhenium alloys caused by coarsening and agglomeration of oxide particles.

[0005] To solve the above technical problems, the technical solution adopted by the present invention is: a method for controlling oxides in an ODS molybdenum-rhenium alloy, characterized in that the ODS molybdenum-rhenium alloy powder is first prepared by a high-energy ball milling process, and then the ODS molybdenum-rhenium alloy powder is sintered by a gradient temperature increase method to achieve the control of oxides in the ODS molybdenum-rhenium alloy. The method specifically comprises the following steps: Step 1: Molybdenum powder, rhenium powder and nano yttrium oxide powder are mixed, and then ODS molybdenum-rhenium alloy solid solution powder is obtained through high-energy ball milling process; Step 2: The ODS molybdenum-rhenium alloy solid solution powder prepared in step 1 is placed in a mold, and an ODS molybdenum-rhenium alloy blank is obtained by pressing; Step 3: SPS sintering the ODS molybdenum-rhenium alloy blank obtained in step 2 by gradient temperature rise to obtain an ODS molybdenum-rhenium alloy; the grain boundary oxide size in the ODS molybdenum-rhenium alloy is only a few hundred nanometers, while the intracrystalline oxide is dispersed and has a size of only tens to hundreds of nanometers.

[0006] The above-mentioned method for controlling oxides in an ODS molybdenum-rhenium alloy is characterized in that the mass fraction of rhenium in the ODS molybdenum-rhenium alloy solid solution powder in step one is 13% to 15%, the mass fraction of yttrium oxide is 0.9% to 1.1%, and the remainder is molybdenum, and the rhenium and yttrium oxide in the ODS molybdenum-rhenium alloy solid solution powder are already dissolved in molybdenum.

[0007] The above-mentioned method for controlling oxides in an ODS molybdenum-rhenium alloy is characterized in that the purity of the molybdenum powder and the rhenium powder in step 1 is not less than 99.97%, and the Fisher particle size is 2.5 ~5.0 The nano-yttrium oxide powder has a particle size of 40 nm to 100 nm, and the mixing speed is 80 r / min to 100 r / min for 4 to 6 hours. By controlling the speed and mixing time of the raw materials, the present invention ensures uniform mixing of the Y2O3 powder with the Mo and Re powders, promotes uniform distribution of the oxides, and eliminates obstacles to the dispersed distribution of the oxides and the segregation of large-sized oxides at grain boundaries.

[0008] The above-mentioned method for controlling oxides in an ODS molybdenum-rhenium alloy is characterized in that the high-energy ball milling process described in step 1 is carried out using a high-energy ball mill, with a ball-to-material ratio of 8 to 10:1, a rotation speed of 260 r / min to 300 r / min, a time of 40 hours to 50 hours, a rotation-stop cycle of 10 minutes for every 2 hours of ball milling, and the high-energy ball milling process is carried out under an Ar and H2 protective atmosphere with a volume ratio of 97:3, and the grinding balls and grinding jar are both made of tungsten carbide. The present invention ensures that sufficient dislocations can be introduced during the ball milling process by controlling the parameters of the high-energy ball milling, providing sufficient nucleation sites for the dispersion and precipitation of oxides during subsequent heat treatment, and providing a basis for controlling the size and distribution of the oxides.

[0009] The aforementioned method for controlling oxides in an ODS molybdenum-rhenium alloy is characterized in that the pressing in step 2 is performed using a hydraulic device, the mold used is made of graphite, and the pressing pressure is 30 MPa to 40 MPa. By controlling the pressing parameters, the present invention compresses the molybdenum-rhenium alloy powder into a molybdenum-rhenium alloy compact, facilitating subsequent sintering.

[0010] The aforementioned method for controlling oxides in an ODS molybdenum-rhenium alloy is characterized in that the SPS sintering in step 3 utilizes a spark plasma sintering furnace, and the SPS sintering is performed using a gradient heating method: the temperature is raised to 600°C to 800°C at a heating rate of 100°C / min and held for 5 minutes, followed by a heating rate of 100°C / min to 1500°C to 1550°C and held for 20 minutes. This invention utilizes a low-temperature-to-high-temperature gradient heating SPS sintering process to further control the size and distribution of oxides while ensuring material density.

[0011] Compared with the prior art, the present invention has the following advantages: 1. The present invention first adopts high-energy ball milling to prepare ODS molybdenum-rhenium alloy solid solution powder, introduces vacancies, dislocations and other defects while realizing the solid solution of oxide, i.e. yttrium oxide, in the matrix, and combines it with the SPS sintering by gradient temperature increase, so that the defects introduced during the low-temperature sintering process serve as nucleation sites for oxide precipitation, ensuring the highly dispersed precipitation of oxide particles, avoiding the coarsening of oxide particles, and consuming part of the strain energy introduced in the high-energy ball milling stage, thereby reducing the growth driving force of the oxide during high-temperature sintering, and realizing the regulation of oxides in the ODS molybdenum-rhenium alloy.

[0012] 2. The method of the present invention effectively optimizes the size and distribution characteristics of oxides in ODS molybdenum-rhenium alloy, realizes the dispersed distribution of oxides within the crystals of ODS molybdenum-rhenium alloy and eliminates large-sized oxides of micron size at the grain boundaries, which is beneficial to improving the mechanical properties of ODS molybdenum-rhenium alloy.

[0013] 3. The control method of the present invention is simple and easy to operate. It can achieve the size and distribution control of oxides in ODS molybdenum-rhenium alloy, especially oxides at grain boundaries, by using traditional processes without complicated processes such as liquid-liquid doping and solid-liquid doping, which is beneficial to the subsequent industrial production and cost control of ODS molybdenum-rhenium alloy.

[0014] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is the X-ray diffraction pattern of the ODS molybdenum-rhenium alloy solid solution powder prepared in Example 1 of the present invention.

[0016] Figure 2 This is a TEM bright field morphology image of the oxide distribution in the ODS molybdenum-rhenium alloy prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0017] Example 1 The preparation method of this embodiment first uses a high-energy ball milling process to prepare an ODS molybdenum-rhenium alloy powder, and then sintering the ODS molybdenum-rhenium alloy powder in a gradient temperature increase manner to achieve regulation of oxides in the ODS molybdenum-rhenium alloy. The method specifically includes the following steps: Step 1: The purity of the product is not less than 99.97% and the particle size is 2.5 ~5.0 Molybdenum powder and rhenium powder are mixed with nano yttrium oxide powder with a particle size of 40nm~100nm, and the mixing is carried out under an Ar and H2 protective atmosphere with a volume ratio of 97:3. The speed is 100r / min and the time is 6h. Then, the mixture is placed in a high-energy ball mill for high-energy ball milling with a ball-to-material ratio of 10:1, a speed of 300r / mi, and a time of 50h. The run-stop cycle is 10min for every 2h of ball milling. The high-energy ball milling process is carried out under an Ar and H2 protective atmosphere with a volume ratio of 97:3. The grinding balls and the grinding jar are both made of tungsten carbide to obtain ODS molybdenum-rhenium alloy solid solution powder. The mass fraction of rhenium in the ODS molybdenum-rhenium alloy solid solution powder is 13%, the mass fraction of yttrium oxide is 0.9%, and the balance is molybdenum. In the ODS molybdenum-rhenium alloy solid solution powder, rhenium and yttrium oxide are solid-dissolved in molybdenum.

[0018] Step 2: The ODS molybdenum-rhenium alloy solid solution powder in step 1 is placed in a graphite mold and pressed by a hydraulic device at a pressure of 30 MPa to obtain an ODS molybdenum-rhenium alloy blank; Step 3: Place the ODS molybdenum-rhenium alloy blank obtained in step 2 into a spark plasma sintering furnace and perform SPS sintering using a gradient heating method: increase the temperature to 600°C at a heating rate of 100°C / min and keep it for 5 minutes, then increase the temperature to 1550°C at a heating rate of 100°C / min and keep it for 20 minutes to obtain an ODS molybdenum-rhenium alloy.

[0019] Figure 1 The X-ray diffraction pattern of the ODS molybdenum-rhenium alloy solid solution powder prepared in this embodiment is as follows: Figure 1 It can be seen that the diffraction peaks represent the (110), (002), (112) and (220) diffraction peaks of the molybdenum-rhenium alloy solid solution from left to right, indicating the successful preparation of the ODS molybdenum-rhenium alloy solid solution powder.

[0020] Figure 2 This is a TEM bright field image of the oxide distribution in the ODS molybdenum-rhenium alloy prepared in this example. Figure 2 It can be seen that the size of the grain boundary oxides in the ODS molybdenum-rhenium alloy is only a few hundred nanometers, while the size of the intracrystalline oxides is only tens to hundreds of nanometers and is dispersed.

[0021] Example 2 The difference between this embodiment and Example 1 is that in step 1, the rotation speed of the high-energy ball milling process is 260 r / min, the time is 50 h, the mass fraction of rhenium in the ODS molybdenum-rhenium alloy solid solution powder is 15%, the mass fraction of yttrium oxide is 1.1%, and the balance is molybdenum; in step 3, the temperature is increased to 800°C at a heating rate of 100°C / min and kept warm for 5 minutes, and then the temperature is increased to 1500°C at a heating rate of 100°C / min and kept warm for 20 minutes.

[0022] Example 3 The difference between this embodiment and embodiment 1 is that the rotation speed of the mixing in step 1 is 80 r / min, the time is 4 hours, the ball-to-material ratio of the high-energy ball milling is 8:1, and the time is 40 hours.

[0023] Example 4 The difference between this embodiment and embodiment 1 is that the pressing pressure in step 2 is 40 MPa; in step 3, the temperature is increased to 700°C at a heating rate of 100°C / min and kept warm for 5 minutes, and then the temperature is increased to 1500°C at a heating rate of 100°C / min and kept warm for 20 minutes.

[0024] 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 variation made to the above embodiment based on the essence of the invention technology shall still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A method for controlling oxides in an ODS molybdenum-rhenium alloy, characterized in that: First, an ODS molybdenum-rhenium alloy powder is prepared by a high-energy ball milling process, and then the ODS molybdenum-rhenium alloy powder is sintered by a gradient temperature increase method to achieve the regulation of oxides in the ODS molybdenum-rhenium alloy. The method specifically includes the following steps: Step 1: Molybdenum powder, rhenium powder and nano yttrium oxide powder are mixed, and then ODS molybdenum-rhenium alloy solid solution powder is obtained through high-energy ball milling process; Step 2: The ODS molybdenum-rhenium alloy solid solution powder prepared in step 1 is placed in a mold, and an ODS molybdenum-rhenium alloy blank is obtained by pressing; Step 3: SPS sintering the ODS molybdenum-rhenium alloy blank obtained in step 2 by gradient temperature rise to obtain an ODS molybdenum-rhenium alloy; the grain boundary oxide size in the ODS molybdenum-rhenium alloy is only a few hundred nanometers, while the intracrystalline oxide is dispersed and has a size of only tens to hundreds of nanometers.

2. The method for controlling oxides in an ODS molybdenum-rhenium alloy according to claim 1, wherein: The mass fraction of rhenium in the ODS molybdenum-rhenium alloy solid solution powder in step 1 is 13% to 15%, the mass fraction of yttrium oxide is 0.9% to 1.1%, and the remainder is molybdenum, and the rhenium and yttrium oxide in the ODS molybdenum-rhenium alloy solid solution powder are already dissolved in molybdenum.

3. The method for controlling oxides in an ODS molybdenum-rhenium alloy according to claim 1, wherein: The purity of the molybdenum powder and rhenium powder in step 1 is not less than 99.97%, and the Fisher particle size is 2.5 ~5.0 The particle size of the nano yttrium oxide powder is 40 nm to 100 nm, the rotation speed of the mixing is 80 r / min to 100 r / min, and the time is 4 h to 6 h.

4. The method for controlling oxides in an ODS molybdenum-rhenium alloy according to claim 1, wherein: The high-energy ball milling process described in step 1 is completed using a high-energy ball mill with a ball-to-material ratio of 8~10:1, a rotation speed of 260r / min~300r / min, a time of 40h~50h, a rotation-stop cycle of 10min for every 2h of ball milling, and the high-energy ball milling process is carried out under an Ar and H2 protective atmosphere with a volume ratio of 97:

3. The grinding balls and grinding jars are both made of tungsten carbide.

5. The method for controlling oxides in an ODS molybdenum-rhenium alloy according to claim 1, wherein: The pressing in step 2 is performed using a hydraulic device, the mold used is made of graphite, and the pressing pressure is 30MPa~40MPa.

6. The method for controlling oxides in an ODS molybdenum-rhenium alloy according to claim 1, wherein: The SPS sintering in step 3 adopts a spark plasma sintering furnace, and the process of SPS sintering by the gradient heating method is as follows: raising the temperature to 600°C~800°C at a heating rate of 100°C / min and keeping it warm for 5 minutes, and then raising the temperature to 1500°C~1550°C at a heating rate of 100°C / min and keeping it warm for 20 minutes.

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