Electron-Correlation Microscopy (ECM) for relaxation and diffusion studies

Basic data for this project

Description

A novel method, electron correlation microscopy (ECM) shall beapplied to analyze the local mechanisms governing relaxation anddiffusion in a deformation-induced amorphous structure (NiTi), and ina deformed amorphous structure (AlYFe). Heterogeneities within theamorphous phases give rise to exceptional crystallization behavior. Bycollecting nano-beam diffraction patterns (NBDP) under isothermalheating conditions as a function of time it is possible to determineintensity variations of the NBDP as a function of time. Thus it ispossible to analyze the medium-range order present in the samples,and, by determining the time dependence of the intensityautocorrelation function, it is also possible to address the timeevolution of the medium-range order. In this respect, theautocorrelation function represents a decay time of the jumpfrequency within the materials, and is thus directly correlated to thediffusive jumps. Methodological and technical aspects of large datasethandling and evaluation shall be addressed, as well as materialsscience issues concerning the diffusion mechanisms and therelaxation behavior in metallic glasses. Specifically, the followingissues shall be addressed in this project: 1) relaxation in differentlyprocessed amorphous structures, a deformation induced andsputtered Ni50.1Ti49.1, 2) relaxation and diffusion in the deformedmetallic glass Al88Y7Fe5. From the comparison of the two modelsystems, crucial insight into the basic mechanisms governing thedeformation processes and atomic motions shall be gained. Sincediffusion is a fundamental process relevant for structure formation andstructure stability, the method has an enormous potential to beapplied to various material classes and related physical questions.