1. Department of Applied Mechanics; Saarland University; 66123 Saarbrücken Germany
2. FR Experimentalphysik; Saarland University; 66123 Saarbrücken Germany
3. Department of Experimental Physics; Saarland University; 66123 Saarbrücken Germany
4. Department of Engineering Design and Materials; Norwegian University of Science and Technology; Trondheim 7491 Norway
5. Department of Materials Science; Saarland University; 66123 Saarbrücken Germany