A novel atomistic approach of estimating interfacial free energy and growth kinetics of primary Mg2Si during semi solid slurry formation of the novel Al-15Mg2Si-4.5Si composite

I Mukherjee and P Das, APPLIED PHYSICS A-MATERIALS SCIENCE & PROCESSING, 130, 338 (2024).

DOI: 10.1007/s00339-024-07499-3

A molecular dynamics-based model of semi-solid formation from liquid melt of the novel Al-15Mg(2)Si-4.5Si composite is reported in the present study. Growth kinetics of Mg2Si phase is studied here at the pre-nucleation stage i.e., prior to the emergence of a stable nucleus. Moreover, insight has been grabbed on semi-solid processing of the said composite at atomic level, wherein the dynamic evolution of the Mg-Si clusters has been studied during cooling/semi solid slurry generation as well as during isothermal holding stage. The effect of variation of cooling rate on the number of clusters, average size of clusters and density of clusters has been investigated. The average size of clusters decays exponentially with cooling rate, whereas the average atomic density of clusters decays following a power-law relation with cooling rate. The change of the thermodynamic parameters (enthalpy and potential energy) during the phase transformation from liquid to semi-solid state are determined here, which are then employed to determine the value of interfacial free energy of Mg2Si-melt interface in the Al-15Mg(2)Si-4.5Si composite, along with the parameters obtained from the dynamic evolution of Mg-Si clusters. The paper also reports the temporal evolution of solid content within the melt, corresponding to the Mg2Si phase, during slurry generation as well as during isothermal holding stage.

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