Traditional mechanical/electrical/thermal testing experiments and material characterization techniques are frequently separate, so they lack the in-situ information resolution required to directly relate the measured properties with individual microstructure evolution events. The broad field of electron microscopy instrumentation development holds great promise for addressing these problems due to its inherently high spatial resolution and the strong interactions between electrons and solids. It is believed to be the ideal tool to exploit materials properties, especially at small scale.

Here, I will present recent results investigating materials properties at multiple scales by coupling the in situ TEM/SEM techniques with other characterization techniques such as HRTEM and EBSD. For instance, by using transmission electron microscopy and nanomechanical characterization, we report that the intense hardening effect of dilute oxygen solutes in pure a-Ti is due to the interaction between oxygen and the core of screw dislocations that mainly glide on prismatic planes, which was thought unlikely based on traditional understanding of solid solution strengthening mechanisms. Also we studied the deformation mechanisms that are responsible for the ultra-high toughness of high entropy alloys. We report on the salient atomistic to micro-scale mechanisms underlying the origin of these properties. We identify a synergy of multiple deformation mechanisms, rarely achieved in metallic alloys, which generates high strength, work hardening and ductility, including the easy motion of Shockley partials, their interactions to form stacking-fault parallelepipeds, and arrest at planar slip bands of undissociated dislocations, in FeCoNiCrMn. We further show that crack propagation is impeded by twinned, nanoscale bridges that form between the near-tip crack faces and delay fracture by shielding the crack tip.

Biography：

Dr. Qian Yu received her B.S. degree and M.S. degree in Materials Science and Engineering from Xi’an Jiaotong University of China in 2006 and 2009, respectively. Then she received her Ph. D degree from UC Berkeley in 2012. From 2012 to 2014, she was a postdoctoral fellow at Lawrence Berkeley National Laboratory before she joined Zhejiang University, where she is currently a Professor in Department of Materials Science and Engineering. Yu’s group conducts research at the mechanical properties of materials at multiple scale, particularly in the advancing materials performance at the nanoscale.