MRS Bulletin

Technical Feature

Technical Feature

In Situ Elastic Strain Measurements—Diffraction and Spectroscopy

R. Spolenak, W. Ludwig, J.Y. Buffiere and J. Michler

Abstract

Understanding the mechanical properties of materials is crucial for their reliable application as bulk materials as well as in a miniaturized form. The deformation of materials is usually non-uniform and, hence, needs to be characterized on a local level. The following article focuses on the in-Situ determination of mechanical stresses in crystalline materials during deformation. This can be achieved by both diffraction as well as spectroscopical methods, where the elastic strain is the parameter measured, which is subsequently converted into stresses by the application of Hooke's law. As in Situ measurements require rapid data acquisition in conjunction with reasonable penetration depths, we will focus on x-rays. However, the different techniques described can be applied to any other diffraction probe as well. The description of diffraction techniques, which span the range from averaging techniques to 2D and 3D strain mapping, is complemented by a section on Raman spectroscopy as an alternative method for stress determination for non-metallic materials. Local stresses also can be correlated to local defect densities.

Ralph Spolenak can be reached at ETH Zürich, Zürich, Switzerland; tel. 41–44–632–2590; and e-mail ralph.spolenak@mat.ethz.ch.

Spolenak has been an assistant professor of nanometallurgy at Eidgenössische Technische Hochschule Zürich, Switzerland, since 2004. He received his MSc degree in technical physics from the Technical University of Vienna in 1995 and his PhD degree in chemistry from the University of Stuttgart in 1999. Spolenak also worked at the Max-Planck-Institute for Metals Research in Stuttgart, to which he returned in 2002 as a group leader after spending time as a postdoctoral member of the technical staff at Bell Laboratories and as a visiting scientist at Lehigh University. His research interests include scaling in the mechanical properties of materials down to the nanometer length scale and ways that these properties can be influenced by metallurgical approaches.

Wolfgang Ludwig can be reached at the European Synchrotron Radiation Facility (ESRF) BP 220, F-38043 Grenoble, France; tel. 33-(0)47688–2973; and email wolfgang.ludwig@insa-lyon.fr.

Ludwig is employed by the French national science foundation (CNRS) and currently works as a collaborating scientist in the x-ray imaging group at the European Synchrotron Radiation Facility (ESRF) in Grenoble. His main scientific interest lies in the development of 3D monochromatic beam diffraction methods and their combination with x-ray imaging and tomographic reconstruction techniques. In the past, Ludwig has led a small team, working on the development of a nondestructive 3D orientation imaging technique (x-ray diffraction contrast tomography) and its application to the characterization of damage and deformation mechanisms in polycrystalline structural materials. Ludwig received his PhD degree in physics from the Ludwig Maximilians University in Munich and joined CNRS after a one-year postdoctoral fellowship at the x-ray microscopy beamline ID21 at the ESRF.

Jean-Yves Buffière can be reached by e-mail at jean-yves.buffiere@insa-lyon.fr.

Buffière was appointed as a lecturer at the Institut National des Sciences Appliquées de Lyon (INSA Lyon) in September 1994. Since then, he has been working on the characterization of damage in advanced materials under load. Through a collaboration with the European Synchrotron Radiation Facility, Buffière developed the use of high-resolution x-ray tomography for the nondestructive 3D characterization of materials. He co-organized the first European workshop on that topic in 1999. Buffière also supervised or co-supervised several PhD degree projects and postdoctoral research programs in this field of research. In September 2003, he was appointed as a professor at INSA Lyon.

Johann Michler can be reached at the Swiss Federal Laboratories for Materials Testing and Research (EMPA), Thun, Switzerland; tel. 41–33–228–4605; and e-mail johann.michler@empa.ch.

Michler is head of the Laboratory of Mechanics of Materials and Nanostructures at the Swiss Federal Laboratories for Materials Testing and Research (EMPA), Switzerland. He received his diploma in materials science at the University of Erlangen-Nürnberg, Germany, in 1995, and his PhD degree in materials science at the Swiss Federal Institute of Technology Lausanne, Switzerland, in 2000. At EMPA, he started his activities as staff scientist in mechanical properties of thin films in 2000. His current research interests focus on scale-dependent mechanical properties of materials. Michler's research efforts include the development of in situ scanning electron microscopy, Raman, and atomic force microscopy mechanical testing methods. He is the author or co-author of more than 100 publications and has co-organized several international conferences.

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