(9月7日9:30)Mechanical properties Characterization of Materials at Multiple Scale
Mechanical properties Characterization of Materials
at Multiple Scale
Reportor:Prof. Qian Yu
Time:2016年9月7日(周三)9: 30-11: 00
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 nanomechanicalcharacterization, we report that the intense hardening effect of dilute oxygen solutes inpure a-Ti is due to the interaction between oxygen and the core of screw dislocations thatmainly 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-scalemechanisms underlying the origin of these properties. We identify a synergy of multipledeformation mechanisms, rarely achieved in metallic alloys, which generates high strength,work hardening and ductility, including the easy motion of Shockley partials, their interactionsto form stacking-fault parallelepipeds, and arrest at planar slip bands of undissociateddislocations, in FeCoNiCrMn. We further show that crack propagation is impeded by twinned, nanoscalebridges that form between the near-tip crack faces anddelay fracture by shielding thecrack tip.
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.
Solid materials are very important market consumes in real industry and are holding the leading roles as structural materials and functional materials. Regardless of the application, the development of solid materials is associated with solid mechanics and microstructure characterization.