Phase field modelling of metal microstructure

• Main Author: Jiang, Yi
• Other Authors: Moon Seung Ki
• Format: Final Year Project
• Language: English
• Published: Nanyang Technological University 2021
• Subjects: Engineering::Mechanical engineering
• Online Access: https://hdl.handle.net/10356/150595
• Institution: Nanyang Technological University

The microstructure evolution process of metal material is of importance to their physical properties and mechanical properties, so it is significant to study them, such as grain growth, precipitation, and deformation. This project reviewed two important modelling methods, phase field modelling and phase field crystal modelling, and developed new models and simulations based on the past literature and research. Phase field modelling (PFM), or phase field method, has been proved to be a powerful simulation method for many microstructure evolutions. PFM regards the interface as a continuous region. In this project, by combining chemical energy, inhomogeneity, applied strain and defects, a unified PFM simulation was developed based on literature. The unified model can be used for complicated cases in spinodal decomposition and precipitation behavior. Case studies have been done for Fe-Cr binary alloy and Fe-Cu binary alloy, which show the effect of different factors in this novel unified model. In addition, as an improvement of PFM, the phase-field crystal (PFC) method is a powerful tool for microstructural evolution simulation across multiple scales. Two PFC simulations about deformation were conducted in this project. Firstly, I used the phenomenological parameters fitted for body-centered cubic structure iron obtained from molecular dynamics, to study the deformation behavior. The purpose of this simulation is to imitate the strain during the solidification of additive manufacturing process for body-centered cubic structure iron. Simulation results showed that strain will affect the form and length of grain boundaries, which could be explained in an energy perspective. Secondly, by applying two-mode PFC, the phase transformation between body-centered cubic structure and face-centered cubic structure can be simulated in a two-dimensional area with the effect of deformation. The results showed how the strain can change the grain structure during microscopic process in the strain condition similar to additive manufacture. In conclusion, this project includes the overview of phase field modelling and its application, develops novel models and case simulations, which could be linked to the manufacturing industry in the future.