Invited Speaker： Prof. G.J. Ackland

Introduction：

Prof. G.J. Ackland is an expert on computer simulations. He is the director of the Institute for Condensed Matter and Complex Systems at University of Edinburgh (UOE). He is also the Fellow of the Royal Society of Edinburgh (FRSE) and the Fellow of the Institute of Physics (FInst). Prof. Ackland is one of the earliest contributors of CASTEP and MOLDY software packages. Prof. G.J. Ackland got his Ph.D. at University of Oxford in 1987. Before joining UOE, he has held post-doctoral positions at  University of Pennsylvania. His current research interests are focused on High pressure physics, Radiation Damage, as well as Phase transitions. He has published over 150 papers in Science, Nature Materials, PNAS, Phys. Rev. Lett and other international journals that received 10,000+ citations (h-index 50).

【Lecture Title】The martensitic transformation from body-centred cubic to close packed: confusion, theory and applications

Time: 9:30-11:30 am, Aug. 28th, 2017

Location: New MSE Building, No. 01 Meeting Room

Abstract:

There are an infinite number of possible close-packed crystal structures.  Many materials transform on cooling from bcc to some close packed structure via a martensitic mechanism, which leads to a complicated microstructure of laths and twins.

In lithium it was believed for 50 years that the low-T ground state is a complicated stacking called 9R.  This year we disproved it, and showed that the actual state is fcc.  I will describe why we suspected a problem, how we attacked it via theory and experiment, and the amount of evidence we assembled to convince people we were correct.

In titanium the transformation goes from bcc to hcp, yet neither of these phases are easy to machine, so titanium parts are limited to tubes, wires, panels etc.  Much effort has gone into designing tools to cut titanium, we take the opposite approach, designing the alloy itself to be machinable and making the world's first titanium trombone.

The theme throughout the talk will be how to use appropriate experiments and calculations to solve a particular problem.  I will discuss simulations using quantum mechanical and classical molecular dynamics methods, and experiments including electron microscopes, cutting machines and synchrotrons.

Welcome to attend the lecture!