Molybdenum alloy, an alloy with high strength and toughness and high temperature resistance, is becoming more and more versatile. Recently, the official website of the Hefei Research Institute of the Chinese Academy of Sciences on the mainland said that the Research Department of Internal Consumption and Solid Defects of the Institute of Solids of the Institute of Solids and the China Nuclear Power Research and Design Institute have made new progress in the research of high-performance molybdenum alloys, and the new molybdenum alloys developed can be used to manufacture space nuclear reactors.
High purity molybdenum metal
Molybdenum (Mo) this number of pletons is 42, molybdenum element is silver-white metal, hard and tough, chemical properties are stable, pure metals and alloys have high melting point, high thermal conductivity, high conductivity, easy to be compatible with alkali metals and other advantages, has long been aerospace technology materials scientists believe that it is a key candidate material for space nuclear reactors. However, pure molybdenum also has problems such as low room temperature plasticity, insufficient high temperature strength, large recrystallization brittleness and irradiation embrittlement, so molybdenum and other metals made of molybdenum alloy to solve the above problems has become a research target in materials science.
Molybdenum rod
The researchers focused on improving the mechanics and irradiation resistance of molybdenum alloys, starting with the introduction of fine oxide particles in molybdenum metal, which can significantly improve the strength of molybdenum alloys and recrystallization temperatures, but the oxide particles will grow at high temperatures, resulting in reduced stress concentration and plasticity of molybdenum alloys, especially at high temperatures.
Therefore, the researchers changed their thinking, through computational simulation, found that the partial gathering of gap oxygen on the crystal/phase interface of molybdenum alloy significantly reduced its strength and ductility, and the gap carbon atoms and zirconium carbide particles can effectively improve the strength of the interface, so it is proposed to synergistically improve the comprehensive performance of molybdenum alloy through nanocarbonate dispersion, fine crystal strengthening and grain boundary purification. That is, the nano-zirconia carbide particles are used as the reinforcing phase, using it to absorb impurity oxygen, reduce its embrittlement effect on the grain boundary, improve the grain boundary binding and low temperature toughness, and achieve the strength and high temperature stability of the material from the grain level, so that the interface formed between the nanoparticles and the matrix of the alloy can also absorb the irradiation defects, which in turn improves the irradiation resistance of the molybdenum alloy material.
Through continuous experiments, the researchers used powder metallurgy and high temperature rotary swaging to prepare a nanostructured zirconium carbide molybdenum alloy with excellent mechanical properties at room temperature and high temperature, and the tensile strength of this alloy at room temperature can reach 928MPa, the elongation rate is 34.4%, which is 26% and 100% higher than the titanium zirconium molybdenum alloy widely used in industry.
The recrystallization temperature of this alloy is about 400 °C higher than that of pure molybdenum, with excellent high temperature stability. At a high temperature of 1000 °C, the tensile strength of zirconium carbide molybdenum alloy can reach 562MPa, which is more than 50% higher than pure molybdenum, nanostructured lanthanum oxide-molybdenum alloy, lanthanum oxide- titanium zirconium molybdenum alloy alloy, etc.; at 1200 °C, the strength is more excellent, and it can maintain excellent plasticity. It shows that this alloy has excellent strength and toughness at room temperature and high temperature, and has obvious advantages compared with similar materials that have been reported. The relevant research results have been published in the top journal of metal materials in the middle of this month in the Journal of Materials.
So why is this material a good material for space nuclear reactors? Because the space nuclear reactor envelope and core structure materials face high temperature, neutron irradiation and liquid alkali metal corrosion and other harsh service environments, the general materials are difficult to meet, zirconium carbide molybdenum alloy is believed to be able to solve this problem.
Conceptual structure diagram of a space nuclear reactor
With the advancement of space technology, human beings will inevitably enter the era of development and utilization of space, although most of the satellites in space at present use solar sail batteries, but when humans build lunar or Mars scientific research stations or bases, or when building interstellar probes or starships, it is bound to use space nuclear reactors, so this equipment belongs to a kind of forward-looking research, and there is also early news that the mainland is developing space nuclear reactors, such as the lunar research station built and operated by the mainland and Russia will be completed around 2028 According to the plan, the facility needs a space nuclear reactor, so the carbide zirconium molybdenum alloy material or the first use of lunar research stations, this invention has an important significance for the manufacture of continental space nuclear reactors.
Nasa-developed samples of a nuclear reactor in space
Resources:
"Observer Network" February 25 article "Chinese Academy of Sciences successfully developed a high-strength and tough molybdenum alloy, which can be used in outer space nuclear reactors"
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