In February, I passed exams of 'Fundamentals of solidification', 'Advanced scanning electron microscopy in materials science' and 'Transmission electron microscopy in materials science'.
I attended in PAS Seminars:
- MSc Eng. Jakub Kawalko: 'The use of methods and optical systems for measuring the stability of photo degradable materials',
- Prof. Antonio G. Checa: 'Multi-level approach to the study of microstructures fabricated by invertebrate molluscs',
- MSc Eng. Adam Debski: 'The enthalpy of formation of inter-metallic phases of lithium-silicon system'.
In that month, I also prepared a draft article under the title: ‘Early stages of recrystallization in ultra fine-grained AA1050 aluminium alloy’:
Abstract
Early stages of recrystallization in aluminium alloys are of considerable practical interest. They were observed for the AA1050 alloy. The samples were processed by equal channel angular pressing along route A up to six passes and then annealed for 1h at different temperatures to obtain different states of recrystallization. Microstructures have been analyzed in sections perpendicular to the extrusion direction, using scanning electron microscopy equipped with high-resolution electron backscattered diffraction facility.
The ECAP-deformed alloy contained a structure of flat grains with the spacing between high angle boundaries ranged from 100nm to 1µm. On annealing, structure coarsened and gets transformed into nearly equiaxed grains. Particular role in the rise of nuclei (at early stages of recrystallization) was attributed to migration of low-angle boundaries and cells coalescence. Later recrystallization stages were attributed to high-angle grain boundaries migration. These processes led to nearly equiaxed grains of similar size. It was documented that length of traces of low- and high- angle boundaries decrease with increasing time of annealing.
The average values of misorientation across both types of grain boundaries systematically grow. Orientation mappings showed that although orientations of new grains were widely scattered, they were not completely random.
Keywords : aluminium alloy, equal channel angular pressing, recovery and recrystallization, microstructure, EBSD