1. Department of Applied Mechanics, Saarland University, Campus A4 2, 66123 Saarbruecken, Germany
2. Institute of Metallurgy (IMET), Clausthal University of Technology, Robert-Koch-Strasse 42, 38678 Clausthal-Zellerfeld, Germany
3. CNRS UMR 7504, Institut de Physique et Chimie des Matériaux de Strasbourg (IPCMS), Université de Strasbourg, 23 Rue du Lœss BP 43, 67034 Strasbourg, France