Nb微合金钢析出行为的热力学计算

Thermodynamic calculations of precipitation behavior in Nb microalloyed steels

以析出热力学为基础,对Fe-Nb-C-N系统中奥氏体/碳氮化物的热平衡过程,计算了不同温度下碳氮化物析出相的平衡摩尔分数、化学驱动力、各组元的原子分数及奥氏体组分等．结果表明,随着温度的降低,析出相的平衡摩尔分数增大,溶解在奥氏体中的各组元的摩尔分数降低,析出相的化学驱动力增大．在低温条件下,Nb和N元素已基本析出．碳化物在析出物中所占的比例主要取决于钢的成分和温度．对于同一成分的钢种,这一比值随着温度的降低而增大．

Based on precipitate thermodynamics, the austenite/carbonitride equilibrium in Fe-Nb-C-N system was analyzed. The equilibrium volume fraction, chemical driving force of carbonitride precip^ates, atom fraction of each element in austenite and carbonitride at different temperatures were calculated. The results show that the equilibrium mole fraction of carbonitride increases, mole fraction of each element dissolved in austenite decreases and chemical driving force increases with decreasing temperature. Nb and N atoms in austenite are basically precipitated fully at low temperatures. The ratio of carbide in precipitates mostly depends on steel composition and temperature, and increases with decreasing temperature for the same composition.