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High dislocation density–induced large ductility in deformed and partitioned steels

 

Strength and ductility are the key mechanical properties of metal materials used in the manufacture of energy-saving light components. Metal materials with ultra-high strength, good ductility and ductility can realize the precision molding of parts and components, and prevent the accidental failure of materials and components. However, in reality, there is often a situation that "you cannot have your cake and eat it" between the strength and ductility of materials, which has become one of the urgent problems to be solved in industrial applications. A study has been developed to improve the strength and ductility of steel materials by introducing a large number of movable dislocations. The results of this study were published on August 24, 2017 in Science, a famous American journal. The paper is titled "High dislocation density–induced large ductility in deformed and partitioned steels". Corresponding authors are mingxin huang of the university of Hong Kong and haiwen luo of the university of science and technology Beijing.

The super steel achieved a huge jump in mechanical properties to an unprecedented yield strength of 2.2GPa and a 16% uniform elongation. Compared with existing metal materials, the D&P steel developed this time has the combination of optimal strength and ductility. Among most metal materials with yield strength higher than 2.0GPa, the D&P steel developed this time has incomparable ductility. In addition, the steel has the following two advantages: first, the alloy cost is low. Super steel is composition of the present invention is simple in system of manganese steel composition, containing 10% of manganese, 0.47% carbon, 2% aluminum, 0.7% of vanadium (V) (mass percent), which is now widely used common alloy element in steel material, not through the extensive use of expensive alloying elements to increase the tenacity, the second is the steel is widely used by industry processing technology to the preparation, such as hot rolling, cold rolling, heat treatment and other general industrial preparation, did not use that are hard to special processing technology to the preparation of large-scale industrial production. It is worth mentioning that the super steel of the invention has great potential to directly carry out industrial production on the scale of 100 tons in steel enterprises.

The invention of super steel is a typical successful example of cooperation between scientists from Beijing, Hong Kong and Taiwan. One of corresponding author of the study, the metallurgical and ecological engineering college professor hai-wen luo team used for many years in the field of iron and steel material machining experience, since 2010 in the national basic research project started in 973 in the third generation of automotive steel manganese steel research and development work, and in the same year in metal materials authoritative journal "Acta Materialia, published research papers about the manganese steel; In 2014, with the support of the key projects of the joint iron and steel fund of the national natural science foundation of China, I continued to conduct in-depth and systematic research on China manganese steel and accumulated rich experience and knowledge in this field. These accumulations have greatly contributed to the design and processing of this new composition system, the successful introduction of a large number of movable dislocations in the steel, and the successful preparation of this super steel through the pilot mill of the institute of metallurgical engineering, university of science and technology Beijing. One of the corresponding authors, Dr Ming-hin wong's team from the department of mechanical engineering at the university of Hong Kong, has been working on new mechanisms for ultra-high strength metallic materials. Yan hongwei's team at Taiwan university used advanced characterization techniques to demonstrate the validity of this mechanism.

 

Comparison of raw material costs between D&P steel and other steel materials

 

D&P steel structure

 

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