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

Abstract

Products of Al-deoxidation reaction in iron melt are the most common inclusions and play an important effect on steel performance. Understanding the thermodynamics on nano-alumina (or nano-hercynite) is very critical to explore the relationship between Al-deoxidation reaction and products growth in iron melt. In present study, a thermodynamic modeling of nano-alumina inclusions in Fe–O–Al melt has been developed. The thermodynamic results show that the Gibbs free energy changes for the formation of nano-Al2O3 and nano-FeAl2O4 decrease with the increasing size and increase with the increasing temperature. The Gibbs free energy changes for transformation of nano-Al2O3 into bulk-Al2O3 increase with the increasing size and temperature. The thermodynamic curve of nano-alumina (or nano-hercynite) and the equilibrium curve of bulk-alumina (or bulk-hercynite) obtained in this work are agree with the published experimental data of Al-deoxidation equilibria in liquid iron. In addition, the thermodynamic coexisting points about Al2O3 and FeAl2O4 in liquid iron are in a straight line and coincide with the various previous data. It suggested that these scattered experimental data maybe in the different thermodynamic state of Al-deoxidized liquid iron and the reaction products for most of the previous Al-deoxidation experiments are nano-alumina (or nano-hercynite).

New Insights into the Mechanism of Nucleation of ZrO2 Inclusions at High Temperature

“…To study the evolution of alumina inclusions at the atom scale, Wang et al [19][20][21] investigated the cluster structure from experimental and theoretical aspects, and they proposed a two-step nucleation mechanism. Using quenching and three-dimensional atomic-probe detection technology, Zhao et al [22] captured the intermediate structure of titanium oxide, and they proposed the cluster-assisted nucleation mechanism.…”

Critical behavior in the ferromagnet

“…Calculated from Widon scaling relation δ = 1 + γ/β. (β = 0.325, γ = 1.24), 3D-XY model (β = 0.345, γ = 1.316), and tricritical mean-field model (β = 0.25, γ = 1.0)[12,26]. Obviously, the unparallel straight lines in fig.4(f) mean that the tricritical mean-field model does not apply either.…”

“…In itinerant-electron systems, the second-order (critical) QPT is considered to be responsible for novel quantum phases like non-Fermiliquid behavior and magnetically mediated superconductivity in materials such as URhAl [8], MnSi [7,9], and UGe 2 [10]. Here we focus on the classical critical behavior of magnetization near FM transition temperature from which the nature of spin-spin interactions and the type of magnetic phase transition can be investigated [11,12].…”

“…The universality class of the magnetic phase transition is dictated by the exchange distance J(r) in the homogeneous magnet. Based on a renormalization group theory analysis, the exchange distance J(r) decays with distance r as [27] J(r) ≈ r −(d+σ) , (12) where d stands for the spatial dimensionality and σ is a positive constant. And the susceptibility exponent γ is defined as…”