Hosted by: Host: Chang-Yong Nam

Center for Functional Nanomaterials Seminar Mechanical Properties of Micrometer-Scale Metals Seok-Woo Lee Department of Materials Science and Engineering & Institute of Materials Science University of Connecticut Monday, November 9, 2015 1:30 p.m. Bldg. 735 â€" 2st floor, Conference Room B Abstract: Nanomechanical devices are certain to play an important role in future technologies. Already sensors and actuators based on MEMS technologies are common and new devices based on NEMS are just around the corner. These developments are part of a decades-long trend to build useful engineering devices on a smaller and smaller scale. The creation of structures and devices always calls for an understanding of the mechanical properties of materials at these small length scales. In the macro-scale (bulk), the mechanical properties of materials are commonly described by single valued parameters (e.g. yield stress, hardness, etc.), which are largely independent of the size of the specimen. However, as specimens are reduced in size to the scale of the microstructure, their mechanical properties deviate very significantly from those of bulk materials. In this talk, we will present some of the interesting phenomena that arise when micrometer-scale metals are deformed. First, we will introduce the recent developments in nanomechanical testing methodologies and size effects on mechanical properties, so-called, 'Smaller is Stronger' behavior. Second, we will present a simple statistical model that can be used to interpret 'Smaller is Stronger' behavior. Then, we are going to use this idea to understand how the change in dislocation density alters 'Smaller is Stronger' behavior of gold micropillars. Furthermore, we will discuss the effect of temperature on the strength of body-centered cubic tungsten and niobium micropillars by considering the change in intrinsic la