Thermodynamic insight into the growth of calcia inclusions at the nanoscale: the case of Fe–O–Ca melt

Abstract

Thermodynamics of the formation of nano-CaO in liquid iron is important to explore the relationship between deoxidation reaction and size of inclusions, and is very useful in the size controlling of inclusions.

Thermodynamic insight into the growth of nanoscale inclusion of Al-deoxidation in Fe–O–Al melt

“…In addition, Wang et al 32 – 34 suggested that the thermodynamic of Al-deoxidation in liquid iron is closely related with the size of alumina. Xiao et al 35 – 37 reported that the deoxidation thermodynamics of metal in liquid iron have depended on the structures and properties of reaction products. Hence, it can be concluded that there is a close relationship between the thermodynamics of Al-deoxidaiton reaction in liquid iron and metastable phase, such nano-Al 2 O 3 .…”

“…The initial structures of (Al 2 O 3 ) 2 cluster and α-Al 2 O 3 crystal were selected from the previous work 33 . The Gibbs free energy of (Al 2 O 3 ) 2 cluster and α-Al 2 O 3 crystal were calculated by the equations [33][34][35][36][37] where E is the total energy of alumina cluster or crystal at 0 K; H and S are the enthalpy and entropy of alumina cluster or crystal, respectively. The H and S were obtained by the analysis of atomic harmonic vibrational frequency of alumina cluster or crystal, which are the functions of temperature T. The calculation details of the relationship among the atomic harmonic vibrational frequency, the thermodynamic properties and temperature can be found in our previous study [33][34][35][36][37] .…”

“…The H and S were obtained by the analysis of atomic harmonic vibrational frequency of alumina cluster or crystal, which are the functions of temperature T . The calculation details of the relationship among the atomic harmonic vibrational frequency, the thermodynamic properties and temperature can be found in our previous study 33 – 37 .…”

“…However, most of the researchers are focused on the thermodynamic equilibrium between the bulk-alumina and iron melt, while less known about the thermodynamic properties of nano-alumina in liquid iron. Many previous work proved that the thermodynamic properties of the nano-alumina are different from that of the bulk-alumina, and the thermodynamic difference among the nanoscale inclusions is more obvious with the decreasing size of inclusions [31][32][33][34][35][36][37][38] . It was reported that the interfacial free energy between nano-alumina and liquid iron are decreased with the decreasing of the size of alumina, and the Gibbs free energy change of Al-deoxidation reaction has very close relation with the size change of alumina inclusion 31 .…”

Evolution behaviour and modification mechanism of inclusions in NM500 wear-resistant steel with calcium treatment

“…where a C3A and a C12A7 are treated as pure substances based on Raoult's law, the activities of them are assumed to be 1. f Ca and f Al are the activity coefficients of Ca and Al in molten steel, respectively, which are calculated by Equation (11). The interaction coefficient e j i of Ca and Al has been summarized in Table 7 [41,44,45]. R is the ideal gas constant, which is 8.314 J/(mol•K).…”