Plastic anisotropy of electro-deposited pure 伪-iron with sharp crystallographic <1 1 1>// texture in normal direction: Analysis by an explicitly dislocation-based crystal plasticity model
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- 作者：Alankar Alankar ; David P. Field ; Dierk Raabe
- 关键词：Crystallographic texture ; 伪-Iron ; Dislocations ; Kink-pairs ; Metal sheet forming
- 刊名：International Journal of Plasticity
- 出版年：January, 2014
- 年：2014
- 卷：52
- 期：Complete
- 页码：18-32
- 全文大小：6405 K
文摘
We present a single crystal plasticity model based on edge and screw dislocation densities for body centered cubic (bcc) crystals. In a bcc crystal screw dislocations experience high lattice friction due to their non-planar core. Hence, they have much slower velocity compared to edge dislocations. This phenomenon is modeled by accounting for the motion of screw dislocations via nucleation and expansion of kink-pairs. The model, embedded as a constitutive law into a crystal plasticity framework, is able to predict the crystallographic texture of a bcc polycrystal subjected to 70%, 80% and 90% thickness reduction. We perform a parametric study based on the velocities of edge and screw dislocations to analyze the effect on plastic anisotropy of electro-deposited pure iron with long needle-shaped grains having sharp crystallographic <1 1 1>//ND texture (ND: normal direction). The model shows a large change in the r-value (Lankford value, planar anisotropy ratio) for pure iron when the texture changes from random to <1 1 1>//ND. For different simulated cases where the crystallites have an orientation deviation of 1掳, 3掳 and 5掳, respectively, from the ideal <1 1 1>//ND axis, the simulations predict r-values between 4.0 and 7.0 which is in excellent agreement with data observed in experiments by Yoshinaga et al. (ISIJ Intern., 48 (2008) 667-670). For these specific orientations of grains, we also model the effect of long needle shaped grains via a procedure that excludes dislocation annihilation.