Activities of the constituents in spinel solid solution and free energies of formation of MgO, MgO.Al2O3
Activities of the constituents in spinel solid solution and free energies of formation of MgO, MgO.Al2O3
复制标题
DOI：
10.2355/isijinternational.40.1059
复制
发表时间：
2000-11
影响因子：
1.8
通讯作者：
K. Fujii;T. Nagasaka;M. Hino
中科院分区：
文献类型：
--
作者：
K. Fujii;T. Nagasaka;M. Hino
尖晶石(镁铝尖晶石)是钢中危害最大的非金属夹杂物之一。然而，由于缺乏关于尖晶石本身的热力学信息，避免尖晶石形成的技术尚未建立。本文用化学平衡技术直接测定了尖晶石固溶体中氧化镁和氧化镁的生成自由能及各组分的活度。本文测定的氧化镁和氧化镁的生成自由能表示为：镁(L)+1/2O2(G)=镁(S)ΔG°f，氧化镁=-669350+135.0T(J/摩尔)氧化铝(S)+氧化镁(S)=氧化镁铝(S)ΔG°f，氧化镁=-20790-15.7T(J/摩尔)。研究了1873K下钢水中尖晶石形成的相稳定性与铁中铝、镁和氧含量的关系，所预测的Al_2O_3、Al_2O_3、Al_2O_3和Al_2O_3相界与作者以前的观察结果符合得很好。
Spinel (MgO.Al 2 O 3 ) is known as one of the most harmful non-metallic inclusions in steel. However, the technology to avoid spinel formation has not yet been established due to lack of thermodynamic information on the spinel itself. In the present work, the free energies of formation of MgO and MgO.Al 2 O 3 , and the activities of the constituents in spinel solid solution have been directly measured by the chemical equilibrium technique. The free energies of formation of MgO and MgO.Al 2 O 3 determined in the present work are expressed by the following equation: Mg(l)+1/2 O 2 (g)=MgO(s) ΔG°f,MgO=-669 350+135.0T (J/mol) Al 2 O 3 (s)+MgO(s)=MgO.Al 2 O 3 (s) ΔG°f,MgO.Al2O 3 =-20 790-15.7T (J/mol) The activity of stoichiometric MgO.Al 2 O 3 exhibits negative deviation from ideality in the spinel solid solution. Phase stability diagram of spinel formation in liquid steel was assessed as a function of aluminum, magnesium and oxygen contents in iron at 1 873 K. The predicted phase boundaries of MgO.Al 2 O 3 , MgO and Al 2 O 3 agreed well with previous observations by one of the present authors.