Title：Probing the Mechanistic Roles of Deformation Twins on the Cyclic Plastic Deformation of Hcp Magnesium
Time：14:30 to 16:30, Nov.20, 2019
Place：A701, School of Mechanical Engineering
Host：WANG Huamiao, Associate Professor (Institute of Mechatronics Design and Knowledge-based Engineering)
Speaker：Dr. Qin Yu (Lawrence Berkeley National Lab)

Biography
Qin Yu is currently a postdoctoral fellow working with Professor Robert O. Ritchie at Lawrence Berkeley National Lab (LBNL). He received his B.E. and M.E. from Shanghai Jiao Tong University. He received his Ph.D. from University of Nevada, Reno, where he dedicated to the study of cyclic deformation, fatigue, and the associated mechanisms in magnesium. His researches focus on the understanding of mechanical properties/performance of novel structural materials, aiming to delineate the mechanistic understanding of the physical basis that governs the process-structure-property relations. His current research interests include cyclic deformation and fatigue of novel lightweight Mg alloys, fracture and fatigue of high/medium entropy alloys, damage tolerance and toughening mechanisms of gradient/heterogeneous materials, and bio-inspired structural materials. 

Abstract
Hexagonal close packed (hcp) magnesium (Mg) has been taken as a promising potential structural material to achieve the lightweightening goals in automobile and aerospace industries. However, the mechanical design of Mg structural components subjected to complex cyclic loading conditions is still challenging. Most of the current approaches for inelastic stress-strain analysis and failure predictions are highly empirical in nature and lack the proper mechanistic structure to account for the essential microstructural roles on the macroscopic deformation. Although bridging the gap between the macroscopic deformation and the microstructure evolution in magnesium is a long standing task, we have taken some preliminary efforts to probe the mechanistic roles of deformation twins on the cyclic plastic deformation of magnesium. Through utilizing the combination of macroscopic cyclic deformation experiments and advanced material characterization, we have successfully correlate the macroscopic cyclic plastic deformation to the microscopic twinning-detwinning and twin-twin interaction behaviors in magnesium single crystal. The disclosure of the twinning roles on the cyclic deformation of Mg single crystal not only enhances our understanding of the fatigue process in  magnesium materials, but also lays a physical foundation to develop sophisticated twinning-induced plasticity (TWIP) deformation model and life prediction model to advance the mechanical design of Mg structural components under cyclic loading conditions.