A Molecular Dynamics Study of Nucleation and Grain Growth of Novel Al-15Mg₂Si-4.5Si Composite during Rapid Cooling Based Semi Solid Slurry Preparation

Abstract:

Owing to their several attractive features such as high hardness, high elastic modulus, light weight, high strength to weight ratio, high thermal conductivity, and high temperature strength, composites from Al-Mg₂Si family offers promise towards deployment in several industries such as automobile, aerospace, marine, defence and electronic. The present molecular dynamics (employing LAMMPS) based simulation study is one of the first attempt to investigate the nucleation and grain growth mechanisms of Mg₂Si phase at atomic level in case of novel Al-15Mg₂Si-4.5Si composite, during semi-solid processing. Modified embedded atom method (MEAM) potential has been used to study the atomic interactions in the composite. Reaching the melt state at 1000 K, the temperature of the system is first decreased from 1000 K to 853 K and then the system is held at 853 K for 100 ps. The simulations are performed with three different cooling rates. With lowering of temperature, randomly distributed Mg and Si atoms form atomic clusters at arbitrary locations within the system, which is the nucleation stage for Mg₂Si phase formation. Cluster size, radial distribution function has been used to investigate the structural evolution of Mg-Si clusters. Cooling rate significantly influences the grain size as well as the grain growth kinetics. The information about the thermodynamic state of the system has been revealed by extracting the values of internal energy, enthalpy, specific heat. during the slurry preparation and isothermal holding stages. The growth mechanism of Mg₂Si nucleus has been characterized from the temporal variation of (Mg + Si) atoms taking part in the cluster formation. Power-law variation is observed in the cooling stage whereas a linear variation is observed in the isothermal stage.

• Periodical: Solid State Phenomena (Volume 347)
• Pages: 197-203
• DOI: https://doi.org/10.4028/p-za0DwV
• Online since: August 2023
• Authors: Indrani Mukherjee, Prosenjit Das*
• Keywords: Cooling Rate, Grain Growth, Mg-Si Cluster, Molecular Dynamics, Nucleation, Semi-Solid

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