高洁净钢的液态结构研究

The structures of liquid pure iron and Fe-C alloy with 0.4wt% carbon were studied by X-ray diffraction in this paper. In addition, high temperature structure of pure iron was studied by Extended X-ray Absorption Fine Structure(EXAFS).The experiments of X-ray diffraction show that near the melting point there is a medium-order structure in both pure iron and Fe-C alloy melts which fades away with increasing temperature. The degree of superheat contributes to the disappearing of the medium-order. The structure information as the average nearest distance of atoms, the average coordination number, the atom cluster size and the atom number in the clusters were obtained by analyzing the original X-ray diffraction intensity curves. It is found that the average nearest distance of atoms is almost independent to the temperature of melts, but the other parameters all decrease with increasing temperature of the melts. Based on above, the result was given as following: Near the melting point there are a lot of atom clusters in both pure iron and Fe-C alloy melts. The atom cluster of pure iron has the body-centered cubic lattices which connect into network by occupying the same edge. There are both Fe-C and Fe-Fe atom clusters in liquid Fe-C alloy. It has the body-centered cubic lattices in Fe-Fe atom clusters too, but they connect into network by occupying the same apex..The high temperature insitu-EXAFS study shows that the liquid structure has close relationship with the solid structure. The liquid metal keeps the same structure of solid state in short-order. At the same time, the structure information decays and the liquid metal becomes more disordered with increasing temperature. The liquid metal presents the character of amorphous state, which indicates that the liquid structure is disordered at long distance..The relationship between the atom cluster size, distribution and numbers of liquid pure iron and Fe-C alloy and degree of superheat was given in this paper, which provides the basic theory to control the solidification structure of steel. With increasing thermal cycle times, the coordination number increases, while the atomic number in atomic cluster and the atomic cluster size decrease.The relationship between the atom cluster size, distribution and numbers of liquid pure iron and Fe-C alloy and degree of superheat was given in the oresent research, which provides the basic theory to control the solidification structure of steel..

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