Annihilation of free volumes and residual strain in nanocrystalline metal layers

• Applicant: Professor Dr. Harald Schmidt
• Subject Area: Thermodynamics and Kinetics as well as Properties of Phases and Microstructure of Materials ; Mechanical Properties of Metallic Materials and their Microstructural Origins
• Term: from 2009 to 2015
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 109158040

Topic of the present project is the basic understanding and mutual correlation of the following physical processes in materials: (1) relaxation of residual strain, (2) temporal change of vacancy concentration, (3) structural re-orientation of grains, and finally (4) self-diffusion processes. The time-resolved (minutes) determination of vacancy concentration, residual strain, and structural re-orientation is done with the newly developed method of Synchrotron based differential dilatometry. There, the lattice parameters and the film thickness are measured (quasi-)simultaneously in-situ during isothermal annealing by X-ray diffractometry and X-ray reflectometry. Investigation of self-diffusion (in grains and grain boundaries) in a stable nano-structure is accomplished with focusing neutron reflectometry on isotope multilayers. In order to obtain a reliable comparison of results, all experiments are carried out on the same type of samples. The planned fundamental research will help to understand microstructural and stress controlled processes in nano-crystalline metals and will also help to optimize the properties of these materials.

• DFG Programme: Research Grants