Date: 17 May 2018 (Thursday)

Time: 10:00 am

Venue: B5-309, Yeung Kin Man Academic Building

Magnesium is the lightest structural metal. Pure magnesium exhibits low ductility and low fracture toughness, both detrimental to its room temperature formability, flaw tolerance and energy absorption in structural applications. Grain refinement and alloying, however, almost certainly increase ductility. The mechanical properties in pure magnesium and its alloys are connected to the hcp crystal structure, which is distinctly different from the well-established fcc/bcc family and not well-understood. By using a multiscale modeling approach from density functional theory and empirical interatomic potential, to molecular dynamics modelingsand continuum theory, we establish the basic dislocation, plasticity and fracture properties in magnesium and its alloys. This firm advance in fundamental science leads to the discovery of the mechanistic origin of low ductility in pure magnesium, and more importantly, the discovery of the mechanistic origin and prediction of enhanced ductility in its alloys. A mechanism-based, quantitative theory is then developed to establish the conditions for ductility as a function of alloy compositions. Predictions with first-principles inputs are shown to be in broad agreement with ductility trends in binary, ternary and higher order alloys. The mechanistic theory can now quickly screen for alloy compositions conditions for high ductility and may help in the development of high-formability magnesium alloys, while the search continues for magnesium alloys with improved fracture toughness.

About the Speaker:

Dr. Zhaoxuan Wu

Department of Engineering Mechanics, Institute of High Performance Computing, 1 Fusionopolis Way, #16-16Connexis, Singapore 138632

Dr. Zhaoxuan Wu is a scientist in the Institute of High Performance Computing, A*STAR, Singapore. He received his PhD in integrative science and engineering from National University of Singapore in 2010. Between 2014 and 2016, he did his postdoc and worked as a scientist in the Institute of Mechanical Engineering at EPFL, Switzerland. He works on problems in solid mechanics and materials from atomistic to continuum scales, focusing on dislocation, plasticity and fracture in engineering metals and alloys. He is currently studying plasticity, fracture behaviors and alloying effects in hcp metals. He received the Outstanding Reviewer Award 2016 for ActaMaterialia from Elsevier.

Enquiry:

Department of Materials Science and Engineering

Email: mse@cityu.edu.hk

Tel: 3442 2985