A phase-field model of twinning and detwinning coupled with dislocation-based crystal plasticity for HCP metals

• Published in: Computational materials science Vol. 95; pp. 672 - 683
• Main Authors: Kondo, R., Tadano, Y., Shizawa, K.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.12.2014; Elsevier
• Subjects: Condensed matter: structure, mechanical and thermal properties; Crystal plasticity; Defects and impurities in crystals; microstructure; Deformation and plasticity (including yield, ductility, and superplasticity); Dislocations; Exact sciences and technology; Finite elements; Indirect evidence of dislocations and other defects (resistivity, slip, creep, strains, internal friction, epr, nmr, etc.); Mechanical and acoustical properties of condensed matter; Mechanical properties of solids; Phase-field method; Physics; Structure of solids and liquids; crystallography; Twinning; Crystal plasticity; Finite elements; Twinning; Phase-field method; Dislocations; Plastic anisotropy; Dislocation motion; Mean free path; Boundary conditions; Order parameters; Phase field method; Stress-strain relations; Monocrystals; Kinematics; Plasticity; Magnesium; HCP lattices; Critical resolved shear stress; Flow stress
• ISSN: 0927-0256; 1879-0801
• DOI: 10.1016/j.commatsci.2014.08.034

[Display omitted] •A model describing both mechanical and morphological behavior of Mg is proposed.•This model can reproduce both the twinning and detwinning under the cyclic loading.•The softening mechanism by the basal slip under [0001] compression is suggested.•The stress relaxation occurs with increase of number of twin nuclei by twinning. In this study, a phase-field model describing both twinning and detwinning that is coupled with a dislocation-based crystal plasticity model is constructed for HCP metals, particularly for magnesium. The driving force of twinning is assumed to be resolved shear stress acting on the twin system. The plastic anisotropy of dislocation mobility in an HCP crystal is described via the dislocation mean free path model, which is incorporated into the hardening law. These models are coupled through an order parameter and stress. Using the present model, several FE analyses on single-crystal magnesium are carried out. The obtained results show that the nominal stress–strain response, twinning and detwinning behavior and the consistent value of twin shear around twins are reproduced by this model. In addition, from the results of tensile simulation of a specimen including a number of twin nuclei, twin nucleation is suggested to occur so as not to increase the mechanical energy by the accumulation of elastic strain and dislocation.