Effect of Geometrical Hardening and Statility on the Formability of FCC Sheet Metals with an Initial 45 Degrees ND Rotated Cube Orientation in Plane-Strain Stretching

Abstract

The stability of ideal orientations is a key aspect in the characterization and understanding of texture evolution during plastic deformation. As is well known, texture evolution, and hence anisotropy, strongly affects formability. In this research, we examine the limit-strain values in the plane-strain stretching mode, in terms of the evolution and stability of crystallographic orientations. The effect that geometric or textural hardening has on the macroscopic response is also quantified.
In particular, we are focusing on the behavior of recrystallized FCC alloy sheets (like aluminum) with initial{100}<100> cube orientations, when the orthotropic axes are inclined at 45 degrees relative to the rolling direction and lying near plain-strain forming paths. As reported in the literature (Lopes et al., 2003; Yoshida et al., 2007, 2009), the limit-strain values are significantly increased near these plane-strain forming paths. In order to understand how these orientations evolve in the Euler space, lattice rotation field maps were calculated using the Full Constraint (FC) and Viscoplastic Self-Consistent (VPSC) models. Results show that these orientations are metastable during rolling and, as deformation proceeds, rotate to Copper and Taylor orientations. The correlation between orientation stability and geometrical hardening is linked to the high formability in plane-strain loading. Texture evolution and the limit-strain predicted by VPSC are in agreement with experimental data reported by Liu and Morris (2002) and Lopes et al. (2003) respectively.