Rare Earth Titanium Materials are moving towards industrialization

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A few days ago, Baotou Jiatai Metal Technology Co., Ltd. (hereinafter referred to as Jiatai Metal) located in Baotou New Materials Industry Park of Shanghai Jiaotou University has successfully developed the only diameter 0.05mm titanium alloy ultra-fine wire in China through independent development equipment.

"relying on the in-situ in-situ rare earth oxide particle strengthening titanium alloy technology and isothermal forging and precision casting technology of the State key Laboratory of Metal Matrix Composites of Shanghai Jiaotong University, we have prepared the international largest titanium matrix composite ingots with a diameter of 580 tons and a weight of 1.5 tons." Tong Botao, head of Jiatai metal technology, said. At present, Jiatai Metal develops industrialization for the urgent needs of high-performance rare metals, special steel, metal matrix composites and other fields in aerospace, aviation, nuclear power, medical devices, ships and other fields. The company now has a design capacity of 500 tons and has 4 production lines or outsourcing production lines for special melting, isothermal forging, precision casting and ultra-fine wire processing.

Metal Titanium-- A New Battlefield of wrestling between countries

As we all know, titanium and titanium alloys have many excellent properties, such as low density, high strength, corrosion resistance, good high and low temperature properties, and have unique functions such as shape memory, superconductivity, hydrogen storage, biocompatibility and so on, ranging from glasses frames and vascular stents to aero-engine blades.

According to Lu Weijie, professor and doctoral supervisor of the School of Materials Science and Engineering of Shanghai Jiaotong University, titanium is known as "cosmic metal", "aviation metal" and "space metal", as well as the "third metal" after iron and aluminum. it is a key supporting material in the field of engineering technology and high technology and an extremely important strategic metal material for national defense. At present, the consumption of titanium and the development level of titanium industry have become an important symbol to measure a country's comprehensive national strength and degree of development.

"globally, about 80 per cent of US titanium products are used in aviation; Europe is planning to invest in the development of new power stations around the world, with Asia and the Pacific accounting for a major share; in the UK, titanium is used in civil industry accounting for about 40 per cent, 45 per cent; Japan is also looking for titanium applications in marine thermoelectric power generation, tidal power generation and other equipment; seawater desalination technology has also been fully developed in Japan and the Arab region." Tong Botao said.

Tong Botao said frankly that the global titanium production enterprises are working hard to tap the new application fields of metal titanium. The amount of titanium used in these new fields has accounted for 10% of the world's total titanium materials. However, the application field and consumption structure of China's titanium products are different from those of the United States, Europe, Japan, Russia and other titanium industry powers. China uses very little in important strategic fields such as aerospace, marine engineering, nuclear power, medical treatment, and so on. it is far from the developed countries, and there is a big gap.

In recent years, with the sharp increase in the consumption of titanium in the fields of chemical industry and desalination in China, as well as China's large aircraft program, Chang'e lunar landing plan, aero-engine research and development plan, nuclear power construction plan, ocean engineering and other major projects have a huge demand for high-quality titanium materials. These projects are in urgent need of large titanium and titanium alloy profiles, pipes (pieces), forgings, plates and strips. And titanium alloy near-net forming parts, new titanium alloy and other products.

"China's titanium industry is still unable to meet the above demand, and many products cannot be mass-produced, or even blank, and still need to be imported in large quantities from abroad." Lu Weijie said: in the face of the needs of the country's implementation of major projects and the upgrading of product demand for the development of related industries, strengthen the research, development and industrialization of domestic titanium and titanium alloy materials, improve the quality of titanium industry products and improve the deep processing level of titanium products, promote the upgrading and transformation of China's titanium industry is the top priority of the industry, has become a major issue of national economic development and national defense construction, has a major strategic position and role.

Break the bottleneck-- compound strengthening becomes a new direction

"strengthening independent innovation, vigorously developing high-end products, controlling core technologies, and striding forward in military and aerospace applications; through the integration of downstream terminal industrial chain clusters, the development of follow-up use of civilian products is the main direction of titanium manufacturing development." Tong Botao said.

According to Lu Weijie, traditional titanium alloys have developed to the extreme to improve their properties through alloying and microstructure optimization. only through compound strengthening can we break the technical barriers of traditional titanium alloys and make titanium alloys "play an important role" in more fields.

The scientific research team led by Lu Weijie creatively put forward the technical route of using multi-component and multi-scale reinforcement to improve the properties of titanium alloy, designed a new in-situ in-situ process, and prepared high-performance rare earth modified titanium matrix composites with simple and low cost. the composition and properties are further optimized, and the key forming technical problems of isothermal forging and precision casting of high performance rare earth modified titanium alloy components are solved.

"using the in-situ patent technology of independent intellectual property rights, the performance of titanium matrix composite precision castings has been improved by 15-20%. It has realized the large-scale application of rare earth modified titanium matrix composites in aerospace, aviation, nuclear power, ships, high-end equipment and other fields, meeting the needs of the national strategy." Lu Weijie said.

In addition, Lu Weijie's team also developed and designed a new in-situ processing process. In particular, the multiphase hydrodynamics theory is used to analyze the melt stop mechanism of different kinds of reinforcements on rare earth reinforced titanium alloy materials, according to the similar physical simulation theory and generalized Darcy's law. the conditions that need to be satisfied in the physical simulation of seepage and retraction flow of titanium alloy melt are given. combined with the solidification shrinkage theory, the formation conditions and volume criterion of shrinkage cavity in the solidification process of rare earth modified titanium alloy melt are given. " Lu Weijie said.

The related research results of titanium alloy preparation by Lu Weijie's team have been published in well-known journals at home and abroad, including more than 200 academic papers, more than 150 articles in SCI, more than 1000 articles cited by SCI, and more than 100 articles in EI. It also won the second prize of National Natural Science in 2015, the Innovation Award of China International Industrial Expo and the Outstanding Product Award of the 12th China International High-tech Achievement Fair.

Industrialization-- nationalization of Titanium Application

According to Lu Weijie, because the titanium smelting and processing technology is difficult and the process flow is complex, the production process design needs to overcome many technical difficulties, and many special smelting, processing technologies and special equipment are needed for the smelting of titanium and titanium alloys and the preparation of processing materials.

In view of the development of isothermal forging technology of rare earth modified alloy materials to ensure the realization of the industrialization goal of isothermal forging technology of rare earth modified titanium alloy materials, the project team adopted high temperature hot compression plastic deformation. closely around the hot deformation behavior of material matrix alloy and ceramic particle reinforcement in the process of plastic deformation, the high temperature deformation behavior of particle reinforced rare earth reinforced titanium alloy material was studied. The coordination mechanism of high temperature deformation process and microstructure of particle reinforced rare earth reinforced titanium alloy was explored, and the suitable isothermal forging window was determined.

In addition, aiming at the development of precision casting technology of rare earth modified titanium alloy material, the project team used graphite spiral to study the fluidity of composite melt in vacuum induction furnace, and analyzed the temperature. The influence of the type and content of reinforcements on the fluidity of rare earth modified titanium alloy materials, as well as the melt stagnation mechanism of rare earth modified titanium alloy materials, the mold filling ability of wedge-shaped samples of rare earth modified titanium alloy materials was physically simulated. The action mechanism of reinforcement in the mold filling process of rare earth modified titanium alloy was analyzed.

The new computer simulation technology such as finite element analysis is used to realize the simulation of isothermal forging process control, and the isothermal forging die and forging process parameters are designed effectively. high performance rare earth reinforced titanium alloy forgings are prepared efficiently and at low cost to meet the design requirements of high performance, high reliability and low cost aviation parts and provide components that can be produced industrially.

At present, the project team has provided 16 batches of particle reinforced titanium alloy forgings to aerospace units, and has obtained batch applications in national key models, and established enterprise standards for high-strength and high-die titanium matrix composites with user units.

"in the aspect of precision casting, precision castings such as particle reinforced titanium alloy impeller and DD shell have been prepared by cooperation with a domestic aerospace precision casting enterprise and using industrial casting equipment." Lu Weijie said that the components have been verified by users, especially the heat-resistant particle reinforced titanium alloy impeller has passed the test in a high-temperature and complex environment, which has significantly improved the performance of high-end equipment, and the complete set of equipment has saved 10 million kilowatt-hours of electricity a year, resulting in significant social benefits.

At present, the transformation of the technical achievements has achieved good economic benefits, with an output value of 4.37 million in 2020.

In the future, Lu Weijie is full of confidence. "the key structural components we have developed and produced have been verified on the relevant equipment models of the first Machinery Group and the sixth Aerospace Institute, and will be supplied in bulk after the company has obtained the relevant qualifications."