Date of Award
Doctor of Philosophy (PhD)
Materials Science and Engineering
The present work has examined the role of shear bands, distribution of second-phase particles, and changes in strain path on deformation and recrystallization processes in single phase and two-phase Al alloys.
The development of shear bands and their influence on the overall recrystallization kinetics in an Al-4.8% Mg alloy was studied at both the macroscopic and microscopic level. Shear bands which contained high angle boundaries acted as preferential nucleation sites for recrystallization nucleation, and influenced the early states of recrystallization kinetics.
The evolution of the substructure around non-deformable silicon particles was studied in Al-Si-Cu single crystals which were oriented for single and mutiple slips. The relationship of the local substructure around particles was related to the subsequent recrystallization behaviour by using electron diffraction. The influence of the spatial distribution of second-phase particles was correlated to the occurrence of recrystallization nuclei in particle-stimulated nucleation (PSN) by using the Dirichlet cell technique. PSN appears to involve only a small fraction of particles in the distribution, indicating that recrystallization nucleation depends on particle clustering as well as particle size and the level of imposed strain.
The influence of change in strain path on mechanical response (deformation and strain hardening) and microstructural evolution during deformation and recrystallization processes were examined. The rate of dynamic recovery appears to be enhanced by the change in strain path. The change in strain path is reflected in changes in recrystallization behaviour and can be rationalized in terms of the energy stored by various strain paths. An attempt has been made to correlate the experimental findings with phenomenological models of dynamic recovery available in the literature.
Koken, Erdogan, "Recrystallization in Aluminum Alloys" (1989). Open Access Dissertations and Theses. Paper 3097.