Dislocation Engineering in Magnesium: Dislocation-Induced Pseudoelasticity and Deformation Twinning

Guest Speaker：Associate professor Guozhen Zhu ，University of Manitoba, Canada

Inviter: Prof. Yao Shen

Date&Time: Friday, 7.March, 10:00-11:30

Venue: Yiucheng Lecture Hall（500），Xu Zuyao Building

 Biography:

Dr. Guo-zhen Zhu, the Canada Research Chair in Mechanical and Functional Design of Nanostructured Materials, now is an associate  professor at University of Manitoba, Canada. Before she joined the University of Manitoba as an assistant professor, she worked as a research professor from 2014-2017 at Shanghai Jiao Tong University. She attended Tsinghua University for her undergraduate studies in Materials Science and Engineering (2007) department and followed her interest in Materials Science to McMaster University at Canada, where she completed her Master in 2009 and her Ph.D. in 2012. She won many local, national, and international awards such as the Falconer Emerging Researcher Rh Award in the area of Applied Science from the Winnipeg Rh Institute Foundation, the Canadian Foundation for the Development of Microscopy Award and the Gerard T. Simon Award from the Microscopical Society of Canada, in addition to young scientist awards from the International Electron Energy-loss Spectroscopy Meeting and European Microscopy Congress.

Abstract:

Arising from its hexagonal close-packed (HCP) crystal structure, magnesium (Mg) exhibits inherent asymmetry in its available slip systems. Basal slip, the easiest deformation mode, has a critical resolved shear stress as low as a few MPa and primarily accommodates deformation within the basal plane. To facilitate c-axis deformation, secondary modes such as <a+c> dislocations or twinning are often required. Structural modifications, such as the formation of long-period stacking-ordered (LPSO) phases, can alter the ease of these secondary deformation modes, providing new insights into Mg’s deformation physics. Using in-situ transmission electron microscopy, we demonstrate that c-axis deformation can be accommodated through the massive activation of parallel basal dislocation loops, exhibiting pseudo-elasticity (full recoverability) in LPSO grains, as well as twin formation assisted by basal dislocations in Mg grains. Additionally, the incipient plasticity, including the nucleation of various deformation modes, is discussed using standalone nanoindentation technique. A deeper understanding of these fundamental processes paves the way for tailoring the mechanical properties of Mg alloys for lightweight structural and functional applications.