An analytical model to predict strain-hardening behaviour and twin volume fraction in a profoundly twinning magnesium alloy

• Published in: International journal of plasticity Vol. 119; pp. 273 - 290
• Main Authors: Sahoo, Sudeep K., Toth, Laszlo S., Biswas, Somjeet
• Format: Journal Article
• Language: English
• Published: New York Elsevier Ltd 01.08.2019; Elsevier BV; Elsevier
• Subjects: Ambient temperature; Compression tests; Deformation; Deformation twinning; Domains; Electron back-scattered diffraction; Engineering Sciences; Lamellar structure; Magnesium alloy; Magnesium alloys; Magnesium base alloys; Mathematical models; Microstructure; Plastic deformation; Plastic properties; Strain hardening; Strain hardening behaviour; Twinning; Electron back-scattered diffraction; Deformation twinning; Strain hardening behaviour; Plastic deformation; Magnesium alloy
• ISSN: 0749-6419; 1879-2154
• DOI: 10.1016/j.ijplas.2019.04.007

An analytical model is presented that can successfully predict the strain hardening behaviour as well as the variations in twin volume fraction in polycrystalline Magnesium alloy Mg-3Al-0.3Mn that twins profoundly during deformation. The model is composed of three basic elements: (i) Twin fraction prediction, based on crystal plasticity elements, (ii) a two-phase composite model composed of the matrix and the twins by adopting the “Iso-work” hypothesis, (iii) a strain hardening approach inspired from a crystal plasticity model. The experiments include uniaxial compression tests for two different cases at ambient temperature. The microstructures were characterized at various strains up to fracture using the Electron Back-Scattered Diffraction technique in a FEG-SEM. The microstructural investigation revealed the formation of a lamellar structure of alternated layers of matrix and {101¯2}〈101¯1¯〉 -extension twin domains. With progressive deformation, the twins broadened and consumed the entire microstructure prior to fracture. The model could accurately reproduce the experimental twin-induced sigmoidal shaped flow curve together with the twin volume fraction evolution. [Display omitted] •A new analytical model is presented for strain hardening and twinning in Mg.•The twinning fraction is given by a single-parameter analytical function.•The matrix-twin composite uses the uniform work hypothesis.•The strain hardening is based on a simplified crystal plasticity law.•It has been shown that both texture-hardening and dislocation hardening occurs in Mg.