Modeling Twin Clustering and Strain Localization in Hexagonal Close-Packed Metals

It has been suggested that microtextures related to deformation twinning can affect the stretch formability of hexagonal close-packed (hcp) metals. We study the evolution of strain localization and the formation of twin clusters in hcp polycrystals due to softening induced by twinning reorientation of the crystal lattice. We performed three-dimensional crystal plasticity finite element simulations of uniaxial and biaxial deformation using basal starting textures of various strengths. Weaker textures resulted in relatively homogeneous deformation, strong textured systems, however, showed significant shear band formation in biaxial tension. In this case, highly strained regions coincided very well with dense clusters of twins. Due to the scarcity of available slip systems, such shear localization due to twin clustering may lead to eventual crack initiation and failure. The spatial correlation of twins was analyzed and was found to be significantly affected by texture. The decay of the correlation function was well approximated by a power law, a characteristic of a wide range of phenomena associated with self-organized criticality.