Materials Science and Engineering Seminar Series: George Pharr
From Pop-in to Pillars: The Utility of Nanoindentation in Studying the Mechanisms of Small-Scale Plasticity
McKamey Professor of Engineering
Department Head, Materials Science and Engineering
University of TennesseeKnoxville
Oak Ridge National Laboratory
Since its development in the mid-1980's, nanoindentation has proven to be a primary tool for discovering and characterizing a variety of unique deformation phenomena that have improved our understanding of the mechanisms of small-scale plasticity. Among these are the indentation size effect, in which hardness at small length scales increases due to plastic strain gradients; indentation pop-in, in which sudden displacement excursions are caused by homogenous nucleation of dislocations at stresses approaching the theoretical strength; and micro-pillar compression testing, in which the nanoindenter is used as a small-scale compression testing apparatus to explore deformation phenomena in samples small enough to probe single dislocation events. Many of these phenomena are interrelated in ways which are not at first obvious. In this presentation, experimental observations are presented that elucidate the relations between pop-in and pillar testing and help us to better understand the basic mechanisms controlling small-scale plasticity.