Inelastic deformation of polycrystalline face centered cubic materials by slip and twinning

• Published in: Journal of the mechanics and physics of solids 1998, Vol.46 (4), p.671,675-673,696
• Main Authors: Staroselsky, A., Anand, L.
• Format: Article
• Language: English
• Subjects: A. twinning; Applied sciences; B. constitutive behavior; B. crystal plasticity; C. finite elements; C. mechanical testing; Condensed matter: structure, mechanical and thermal properties; Deformation and plasticity (including yield, ductility, and superplasticity); Elasticity. Plasticity; Exact sciences and technology; Mechanical and acoustical properties of condensed matter; Mechanical properties and methods of testing. Rheology. Fracture mechanics. Tribology; Mechanical properties of solids; Metals. Metallurgy; Physics
• ISSN: 0022-5096
• DOI: 10.1016/S0022-5096(97)00071-9

There have been considerable recent advances in the understanding of anisotropy due to crystallographic texturing, and a reasonably successful elasto-viscoplasticity theory for the deformation of face-centeredcubic (f.c.c.) single crystals and polycrystals with high stacking fault energies is now at hand. The high stacking fault energy f.c.c. materials (e.g. Cu, Al) deform predominantly by crystallographic slip. In contrast, for materials with low stacking energies, e.g. α-brass, in addition to crystallographic slip, deformation twinning plays an important role in maintaining generalized plastic flow. A direct manifestation of twinning is the different crystallographic texture that is observed in 70−30 brass as compared to pure copper. In this paper we formulate a rate-independent constitutive model which accounts for both slip and twinning. We have also developed a new scheme to determine the active systems and the shear increments on the active slip and twin systems. We have implemented our constitutive equations and computational procedures in the finite-element program ABAQUS/Explicit (1995). By using comparisons between model predictions and macroscopically-measured stress-strain curves and texture evolution we have deduced information about the values of the single-crystal parameters associated with slip and twin system deformation resistances and hardening due to slip and twinning. We show that our model is able to reproduce both the experimentally measured pole figures and the stress strain curves in plane strain compression for α-brass. With the model so calibrated, we show that the predictions for the texture and stress-strain curves from the model are also in reasonably good agreement with experiments in simple compression. We have also evaluated the applicability of a Taylor-type model for combined slip and twinning. Our calculations show that for the high-symmetry f.c.c. brass, a Taylor-type model for crystals deforming by combined slip and twinning is able to reasonably well predict the macroscopic stress-strain curves and crystallographic texture evolution. Our calculations show that in plane strain as well as simple compression, the crystallographic texture that develops is a result of lattice rotation due to both slip and twinning, and that as suggested by Wassermann (1963), in contrast to copper which does not twin under normal circumstances, it is twinning which is responsible for the brass-type texture that is observed in f.c.c. metals