Microstructure and texture controlled mechanical behaviour of aluminium processed by static and dynamic severe plastic deformation

Microstructural engineering is at the core of a never ending quest for better performing materials. A key microstructural parameter which affects the physical, mechanical, chemical and biochemical properties of metals is their grain size. The grain size can be reduced considerably by imposing large plastic deformations. In this thesis, a static and dynamic setup, designed and realized within the framework of previous projects, was used to study the behavior of commercially pure aluminum subjected to severe torsional deformations. The static setup is a classic high pressure torsion setup. The dynamic setup, on the other hand, is based on the principles of split Hopkinson bar torsion testing. The refining efficiency of the dynamic and conventional high pressure torsion methods was compared in this investigation and is one of the important goals. To this end, the microstructural evolution in the aluminum, as a function of the applied strain was followed in terms of the grain shape, size, inter-boundary spacing, low and high angle boundary fractions, misorientation angle and crystallographic texture. The mechanical property characterization included Vickers microhardness measurements and uniaxial tensile testing of miniature dogbone-shaped samples. Three-dimensional digital image correlation was employed to acquire the information on local full-field strain maps for the deforming miniature tensile samples. Next, the experimental true stress-true strain data was modelled to understand the contributions of different strengthening mechanisms, the strain hardening within stable deformation limits, the plastic instability condition, and the reasons for the surprisingly large post-necking elongations, in prior severely deformed metals