This research involves experimental investigations of strain localization on single - and poly-crystalline ductile-matrix material systems, analyses of mechanisms of micro-localization, e.g. shear banding, at intermediate and large plastic strains in these material systems, and the development of constitutive relations for the effective plastic response of ductile materials including the effects of complex multi-slip hardening, particles and pores, and microscopic shear localizations. The goal is to develop techniques to achieve optimal processing conditions so as to avoid undesirable flow localizations.