Relations Between Macroscopic Mechanical Properties And Microscopic Valence Electronic Structures Of Microalloy Steel

In recent years, as the environmental and resource problems attract more and moreattention, the study of microalloy steel gradually turns towards the third generationAdvanced High Strength Steel (AHSS) that has a low cost and high strength and ductilityin order to protect the environment and reduce energy conservation and emissions.However, with the increase of the strength of steel material, the plasticity of which willreduce as usual, the two are mutually restricted. Therefore, it is particularly important tohave a better understanding of the correlation between the material strength, plasticity andtoughness and the microstructure before the design of the component and structure ofsteel.With microalloy steels treated by the quenching-partitioning-tempering (Q-P-T)process as the research object, the valence electron structures of Phases were calculatedbased on the empirical electron theory of solids and molecules and bond length differencemethod, which made the study of macroscopic mechanical properties of microalloy steelgo deep into the electron theoretical level of atomic bonding. On this basis, the internalrelations between macroscopic mechanical properties and microscopic valence electronicstructures were discussed combined modern detector method and statistical principle.The calculating model of electron structure of all the component cells wereestablished, the concept of covalent electron density of unit cells was put forward based onthe theory of C-M segregation in Solid alloys through the calculation and analysis ofvalence electron structure parameters of the carbon-containing crystal cells. Covalentelectron density and strength of unit cells was discussed through the analysis andcomparison between the covalent electron density of the cells containing all correspondingalloy elements in martensites and that in austenites; the concept of total bond energy ofunit cells was put forward through the calculation and analysis of bond energy parametersof all the component cells. The total bond energy of crystal cells composed of allcorresponding alloy elements between in martensitic constituent and austeniticconstituent were analyzed and compared, and the relevance between the statistics of total bond energy and toughness in microalloy steel was discussedBased on the discussion of the internal correlation between the covalent electrondensity and the bond energy of microalloy steel and its macroscopic mechanical properties,the equivalent covalent electron density and the statistics of bond energy were proposed asthe representation of macroscopic mechanical properties, and their accurate definitionshave been given. Research shows that the equivalent covalent electron density ofmicroalloy steel is the character of its strength. The bigger the equivalent covalent electrondensity is, the higher the strength of microalloy steel will be. While the statistics of thebond energy of microalloy steel is the character of its toughness, the higher the statistics ofbond energy is, the higher the toughness of microalloy steel will be. These parameters canbe extended to other alloy steels of which the alloy phase structures are known.