Main studies carried out during December:

- analysis of the results obtained so far,
- casting of new quaternary alloy,
- microstructure analysis of prepared ingot using SEM,
- preliminary tensile tests on melt-spun ribbons with molybdenum addition using INSTRON 6025,
- microstructure analysis of melt-spun ribbons with vanadium addition using TEM,
- participation in seminars and lectures

If the title is just 'report', that means that nothing really exciting happened... I have been slowly developing my tools for geometric grain boundary characterization, and collecting ideas for futher work. Hopefully, I should be able to analyze some statistical samples soon. What is more, there appeared the idea of comparing two methods for detecting GB character, as far as I know they have not been confronted yet.

My Research:

-Processing by ECAP (equal channel angular pressing) a sample of AA1050 three times according to route A.
-Completion of series of studies with scanning electron microscopy using technique - EBSD (electron backscatter diffraction) - for creating orientation maps (microstructure) for aluminum alloy AA1050.
-Creating pole figures based on data obtained from orientation maps (from EBSD/SEM measurements).

In December I performed some Vicker’s hardness test on the last series of composite samples (with submicron AlN reinforcement). It turned out that they have considerably lower hardness than the previous series (with ~1 micron AlN) – about 250 HV. The worse mechanical properties may origin from the tendency of fine AlN particles to form agglomerates.
I also calculated a matrix grain size distribution of this series of composites on the basis of TEM bright field micrographs analysis.

As December was passing by, and days until delivery of my titanium was freezing away I had the chance to read something more on plastic deformations of metals and KoBo method. Plastic deformation in low temperatures is inevitable tied to development of internal structure, decrease of ductility and increase of stress. This is related to dislocation nature of deformation. Structure formed during such deformation can be destabilized if initially set conditions of stress and temperature are altered. If such destabilization accrues with high dynamic at low temperature and high stress conditions, high dislocations energy it might lead to fracture of material. But if such process takes place with lower dynamic, for instance in higher temperatures, with low stress, destabilization of structure can be used to achieve very large plastic deformation without loosing integrity of material. This are some concepts that lead to realisation of KoBo method. Destabilisation of structure there is achieved by application of cyclically changing external stress. When internal structure is destabilised, material starts to deform by visco-plastic flow with very low internal stresses, thus allowing for very large deformation. Inventors of KoBo method argue that this type of deformation can take place at low temperatures but with specific strain conditions. The concept is that during high-rate deformation with cyclically changing deformation path high concentrations of point defects (vacancies, interstitial atoms) are created and maintained. Those defects has very low diffusion activation energies and therefore greatly improve ability of material to deform by plastic flow with almost no increase of internal stress. While this hypothesis presents completely new approach to plastic deformation it would be very interesting indeed to look closer at mechanisms involved with KoBo method. And that is one of the things I plan on doing in the foreseeable future.