材料期刊网

利用“固体与分子经验电子理论”的BLD方法建立了Fe-C马氏体的价电子结构。碳原子连同其第1、2、3近邻Fe原子构成的小块形成含碳价电子结构单元;相应的不含碳的小块构成不含碳价电子结构单元,两者混乱分布构成马氏体晶体。对1.7wt-％C马氏体得出:含碳结构单元内Fe_Ⅰ,Fe_Ⅱ,Fe_Ⅲ分别在甲种杂化第11,10,8各阶,碳在第6阶;不含碳结构单元内Fe在甲种杂化第8阶。含碳结构单元内n_A=0.9991,n_B=0.8479;不含碳结构单元内n_A,n_B日与α-Fe相同。不同含碳量马氏体中只是两类结构单元相对数量不同。比较两类结构单元的n_A和n_B,立即看出马氏体硬度随含碳量增加而提高,这与实验事实一致。

Based on the BLD method of the empirical electron theory of solids and molecules, the valence electron structure of Fe-C martensite was established. Each carbon atom making fractional covalent bonds with its 1st, 2nd and 3rd Fe neighbours forms a small cell to be called carbon involved unit. And the corresponding small cell of Fe atoms containing no carbon to be called no carbon unit. The martensite crystal structure is built upon by these two types of units. They distribute randomly in the martensite crystal. For the 1.7 wt-％ C martensite, the result shows: in the carbon involved units, there are three kinds of Fe atoms, Fe_Ⅰ, Fe_(Ⅱ) and Fe_(Ⅲ), on the 11th, 10th and 8th hybrid levels of A-type hybridization states of Fe respectively, and carbon atom is on its 6th hybrid level; in the no carbon units, the Fe is on the 8th level of A-type. In the carbon involved units, n_A=0.9991 and n_B=0.8479, and in the no carbon units, n_A and n_B have the same values as in α-Fe. The relative number of the two kinds of units changes with the content of carbon. Comparison of the values of n_A and n_B in the two kinds of units immediately shows that the hardness of martensite must increase with the content of carbon. This agrees with the experimental fact.