Temperature and electric-field-induced structural evolution and transport in Li2O-bearing tundish flux: A molecular dynamics study

During plasma heating, the viscosity of molten slag is difficult to measure in situ, and the mechanisms governing its structural evolution and viscosity response remain unclear. Molecular dynamics simulations were performed to investigate the effects of temperature and an external electric field on the structure and transport properties of CaO-Al 2 O 3 -SiO 2 −MgO-Fe 2 O 3 -Li 2 O slag. The simulated viscosities showed a mean error of 7.9 %. The results showed that increasing temperature had little effect on the short-range structure of the slag but weakened its local order. It also promoted Si/Al-O network depolymerization, the conversion of BO to NBO, and the breakdown of medium-range network connectivity. These structural changes reduced the viscosity from 0.107 to 0.020 Pa·s. The external electric field enhanced local network polymerization and induced topological differentiation within the medium-range Si/Al-O network by driving the migration of charged structural units and the directional rearrangement of charge-compensating ions. The structural response gradually approached saturation with increasing field strength, while the slag viscosity stabilized at approximately 0.036 Pa·s. Moreover, considering the combined effects of temperature and the external electric field, a strong linear correlation was found between the structural parameters and the natural logarithm of viscosity. These findings provide a theoretical basis for the rational design and optimization of covering fluxes used in plasma-heated tundishes.