An atomistic study of solute atom segregation on the structure, energy, and mobility of twin boundaries in Mg alloys

Magnesium (Mg) alloys represent one of the most promising material systems for weight-saving structural applications where their low density is critical to save energy and protect the environment by reducing CO2 emissions.

The formability, yield strength and tension compression yield strength asymmetry of wrought hexagonal metallic products, such as Mg, are all related to deformation twinning. Twinning is a form of symmetrical intergrowth between two or more adjacent crystals. The two crystals across the boundary (termed as twin boundary) are mirror symmetry to each other. A shear stress can generate a deformation twinning and drive the glide of the twin boundary.

It is therefore essential to obtain a fundamental understanding of the nucleation and growth mechanisms of deformation twin crystals. We will specifically focus on the nucleation, growth and propagation of deformation twinning in Mg alloys.

This project aims to employ the density functional theory, machine learning interatomic potential, molecular dynamic simulations, and Monte Carlo simulations for the much-needed knowledge of how some typical solute atoms, such as Zn and Gd, affect the twin boundary structures and dynamics.

Both joint PhD projects will provide new insight into the deformation twinning mechanism and lay the ground for a new alloy design approach for Mg alloys.

Project goals

The objectives of this project are:

• Density functional theory calculations for twin boundary energy of MgZn and MgGd alloys and solute atom. segregation to twin boundary and twin boundary steps.
• Machine learning interatomic potential for the two alloys.
• Monte Carlo simulations for solute atom segregation.
• Molecular dynamics simulations for the mobility of twin boundary steps and dislocations with solute atom segregation.

Supervision team

Shanghai Jiao Tong University: Dr Hong Liu, Dr Liming Peng

The University of Melbourne: Associate Professor Zhe Liu, Dr Christian Brandl

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Who we are looking for

We are seeking a PhD candidate with the following skills:

• Demonstrated research experience in the field of either Mechanical Engineering or Materials Science and Engineering.
• Demonstrated ability to work independently and as part of the team.
• Demonstrated time and project management skills.
• Demonstrated ability to write research reports or other publications to a publishable standard (even if not published to date).

Further details

UoM has the first and only integrated computational materials engineering (ICME) group in Australia, with team members having the world-leading expertise in atomistic simulations for metallic alloys. Dr Zhe Liu is an expert on density functional theory (DFT) calculations for alloy thermodynamics. Dr Christian Brandl is an expert on atomistic simulation of defects in metallic alloys. They have published >100 papers in top journals in the field (e.g., Science).

SJTU has a world-leading Mg alloy group, including prominent experimental and theoretical scientists. Dr Hong Liu is an expert on mesoscale simulation techniques for microstructure evolution. He has published around 20 papers on top-level journals (e.g., Acta Materialia, Progress of Materials Science).

The two lead supervisors (Dr Zhe Liu and Dr Hong Liu) started their collaboration ten years ago. Their complementary expertise provides PhD students with an excellent opportunity for comprehensive training of various aspects of metallic alloy design.

The UoM PhD candidate will be enrolled in the PhD program at the Department of Mechanical Engineering of the University of Melbourne, and the SJTU PhD candidate will be enrolled in the PhD program at the Department of Materials Science and Engineering at Shanghai Jiao Tong University.

To apply for this joint PhD opportunity, and to view the entry requirements, visit How to apply. Please read the application guidelines and eligibility information for both UoM and SJTU before contacting the lead supervisors.