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Purity: | >99.95% |
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he invention of this technology revealed the deformation and fracture mechanism and leading factors of multi-scale rare earth oxides doped molybdenum alloy, proposed a new idea of nano-doping for strengthening and toughening, and broke through the key technical bottlenecks such as the nanocrystallization and non-agglomeration uniform dispersion distribution of rare earth oxides in molybdenum alloy.
Because rare earth elements can effectively improve the strength and toughness of molybdenum, rare earth molybdenum alloy is the main alloy of molybdenum metal, and it is widely used in production. However, the product quality of domestic rare earth molybdenum alloy has a certain gap with that of western countries, which limits the production, application and development of domestic molybdenum alloy. The improvement of properties of rare earth molybdenum alloy depends on the coordination of dispersion strengthening and fine hardening. A large number of experiments, theories and numerical simulations have proved that the uniform and dispersed rare earth second phase particles can significantly reduce the grain size of molybdenum alloy and improve the material elongation and toughness. The project team led by Professor Sun Yuanjun worked out the basic performance improvement of raw materials from the source, combined with the optimal sheet processing technology, and finally determined the research idea of excellent performance and durable molybdenum alloy products.
How to evenly disperse rare earth elements into molybdenum matrix at molecular level is the first difficulty. In order to solve this problem, the chemical synthesis process of rare earth and molybdenum is not uniform, the segregation and aggregation of the crystallization process are not uniform, and the occurrence and distribution of rare earth elements in the crystal slurry are not uniform. Therefore, Luo Jianhai, a chemical expert in the team, boldly proposed the rare earth ammonium dimolybdate, a new concept in the field of molybdenum chemistry, and made the precursor of rare earth evenly dispersed ammonium dimolybdate.
Firstly, the rare earth molybdic acid complex was successfully synthesized, and then the complex was used as the crystal seed, and the number of nucleation was controlled by controlling the concentration of the complex. Finally, through countless tests day and night, the process parameters were determined and optimized to obtain crystal clear, non-agglomeration, strong liquidity, rare earth ammonium dimolybdate with uniform distribution of rare earth, and then prepared molybdenum metal with excellent processing performance and uniform dispersion of nanoscale rare earth oxides, whose strength and fracture toughness were significantly higher than similar products. The strength and elongation of molybdenum wire produced by this molybdenum metal are greatly improved, and the breaking rate is significantly reduced.
Due to the characteristics of poor plasticity, low plastic-brittle transition temperature and high thermal conductivity of molybdenum metal, only the thin molybdenum plate below 1mm can be deeply processed. The forming of large thick wall and large size molybdenum ware is always a blank in China.
The research group headed by Dr. Wang Lin formulated the research idea of optimizing the grain structure, improving the performance of raw materials and innovating the production process from the micro level. Nano-doped rare-earth molybdenum alloy with uniform dispersion was prepared by using rare-earth ammonium dimolybdate. The production process of conventional molybdenum plate was optimized, and the molybdenum alloy plate with uniform grain size, high recrystallization temperature, low plastic and crisp transition temperature, high elongation, high strength and toughness, isotropic and suitable for deep drawing was prepared. In the deep drawing process of large thick-walled molybdenum alloy vessels, the research team broke the traditional idea and adopted the hot forming theory and technology for the first time. A four-column hydraulic press with a heating chamber was used to synchronously heat the forming mold and molybdenum plate, which effectively overcame the defects of cold deep drawing and solved the technical problems of temperature drop and uneven temperature distribution of molybdenum plate during the forming process. The hot forming of molybdenum alloy boat with 1~8mm wall thickness can be achieved successfully by deep drawing of molybdenum plate at 400~1200ºC and low pressure.