ABSTRACT
Bauschinger effect is a well-known phenomenon, in which the tensile stress is higher than the reverse compressive stresses. This chapter reports that gradient structured copper exhibits an extraordinarily large Bauschinger effect. Bauschinger effect has been extensively reported in conventional homogenous materials. However, the Bauschinger effect in homogenous materials is usually not very strong, and has not been related with mechanical properties such as strength and ductility. Bauschinger effect is a phenomenon that the reverse compressive yield stress is lower than the initial forward flow stress at the beginning of unloading. The microstructure of gradient structured (GS) copper is heterogeneous and the grain sizes vary from nanoscale to microscale. Layers with different grain sizes have different flow stress, which first leads to the development of two dynamically migrating plastic/elastic boundaries, and later two migrating necking/stable boundaries. The GS copper shows extraordinary Bauschinger effect in which the reverse yield stress increases with increasing pre-strain.
