Competitive substitution of CaO for MnO in CaO-Al₂O₃-SiO₂-MnO oxides: Atomic-scale insights into structural depolymerization and inclusion properties via molecular dynamics simulations

抄録

The proportion of CaO and MnO content within the CaO-Al₂O₃-SiO₂-MnO (CASM) inclusion system plays a pivotal role in determining its deformability during the rolling process. This influence manifested not only through properties such as liquidus temperature, viscosity, and crystallization characteristics but also in the evolution of its internal microstructure. The calculations of properties and structural analysis were based on molecular dynamics (MD) simulations and thermodynamic calculations. As CaO substituted MnO, Ca²⁺ ions preferentially consumed Si-BO-Si linkages over Al-BO-Al linkages. This resulted in the depolymerization of complex Si-containing structures (specifically, Q₃ and Q₄ units) and an increase in the number of [CaO₆]^4- cages. Subsequently, the decline in the network connectivity (NC) led to alterations in the crystallization characteristics of the system, including a weakening of its glass-forming ability (GFA) and a transition of precipitated crystals from Mn₃Al₂Si₃O₁₂ to CaSiO₃. Meanwhile, the diffusion ability of Si⁴⁺ emerged as a pivotal constraint for the crystallization process of the system. The Young's modulus of oxide glass, primarily influenced by density, increased from 59.82 GPa to 89.24 GPa as the CaO/(CaO+MnO) ratio escalated from 0 to 1. Mn₃Al₂Si₃O₁₂ crystals possessed a remarkable Young's modulus of 236.80 GPa, a property that could potentially lead to wire breakage in tire cord steel. Consequently, it was crucial to circumvent the temperature window conducive to its isothermal crystallization during industrial production.