中、低碳钢中固溶稀土元素的价电子结构分析

根据固体与分子经验电子理论(EET理论)，采用键距差(BLD)方法，计算了稀土元素固溶于奥氏体，珠光体和马氏体的价电子结构。计算结果表明，碳高有利于提高钢中的稀土固溶量。稀土元素的溶入，改变了奥氏体中C，Fe原子的分布，引发空位等晶格缺陷及C-RE偏聚区的形成，从而缩短了先共析铁素体的孕育期，并使先共析铁素体数量增多，珠光体数量减少。C-RE偏聚使珠光体转变的开始温度降低，从而减小珠光体的片层厚度及层间距，并导致粒状珠光体的形成。RE更多地存在于对渗碳体中，其对渗碳体显微硬度的提高将大于对铁素体的作用。稀土元素固溶于马氏体，提高马氏体强度，增强马氏体的回火稳定性，提高马氏体再结晶温度。

Analysis of Valence Electron Structure of RE in Solid Solution in Medium and Low Carbon Steel

According to EET theory and BLD method, the valence electron structures of the RE in the solid solution of austenite, pearlite and martensite were calculated. The results show that high carbon content is favorable to increase the volume of the RE in the solid solution. The dissolved RE change the distribution of C, Fe in austenite to induce lattice defects, such as vacancy, and C-RE segregation. Then the incubation period of proeutectoid ferrite is shortened and its number is increased, and the number of pearlite is decreased. The C-RE segregation lowers the transformation temperature of pearlite, which lessens the thickness of lamellas and lamellar spacing of pearlite and induces the granular pearlite. Most of the RE dissolves in cementite, so the effect of the RE on micro-hardness of cementite is more than that of ferrite. The RE dissolved in martensite strengthenes martensite, enhances the tempering stability and recrystallization temperature of martensite.