Fractal analysis of strain induced microstructures in metals

Fractal Analysis; Dr. Robert KoprowskiThe deformation of materials is a key topic for different industrial sectors. The correlation between specific thermomechanical processes, like extrusion, rolling or additive manufacturing, and the resultant material’s microstructure, is particularly interesting. In these thermomechanical processes, the microstructure of the materials depends mainly on the applied stress, the magnitude of strain achieved in a given time period, and the temperature. In the case of metals and alloys, plastic deformation can be described microscopically based on the dynamics of a huge population of moving dislocations. Plasticity is characterized at the mesoscale by the avalanche-like collective behavior of dislocations, which is a typical case of self-organized systems. Dislocations are organized into cells named grains or subgrains that greatly influence the mechanical behavior of metals and alloys. The existence of these fractal structures of dislocations in metals is well established. However, it is very complex to conduct a fractal analysis of these microstructures. This is actually done by looking for a compromise between a detailed description of the complex fractal microstructure and the development of a practical procedure that avoids unaffordable extensive characterization in a different time and spatial scales. Several cases will be described considering different alloys and experimental conditions.This study was financially supported by Proyects MAT2017-83825-C4-1-R from MINECO and Y2018/NMT-4668 from CAM, Spain. The authors would like to thank Antonio Tomás, Dr. Judit Caballero, and Prof. Paloma Adeva from Electron Microscopy Lab of CENIM for their support and help with the microstructure characterization and Edurne Laurín for her help in TEM sample preparation