Phenomenological crystal plasticity modeling and detailed micromechanical investigations of pure magnesium Jing Zhang, Shailendra P. Joshi n Department of Mechanical Engineering, National University of Singapore, Singapore 117576, Singapore article info Article history: Received 15 March 2011 Received in revised form 14 October 2011 Accepted 4 January 2012 Available online 14 January 2012 Keywords: Pure magnesium Single crystal plasticity Constitutive laws Slip and twinning Micromechanics abstract We present a single crystal plasticity model for pure Mg incorporating slip and deformation twinning. The model uses the basic framework of Kalidindi (1998), but proposes constitutive descriptions for the slip and twin evolution and their interactions that are motivated by experimental observations. Based on compelling experimental evidences, we distinguish between the constitutive descriptions of the tension and compression twinning to better represent their roles in the overall hardening of Mg single crystals. With these improved phenomenological descriptions, we first calibrate material parameters for the different slip and twin modes by performing three- dimensional simulations mimicking the plane-strain compression experiments by Kelley and Hosford (1967, 1968) on single crystal pure Mg. In doing so, these computational responses are critically compared with their corresponding orienta- tion-dependent microscopic (slip and twin activities) and macroscopic (stress–strain responses) experimental observations. Then, the calibrated parameters are used to predict several other experimental results on pure single- and poly-crystal Mg under different loading conditions. We also investigate the role of pre-existing heterogeneities such as initial twin population and stiff, elastic inclusions on the single crystal macroscopic and microscopic responses. Microstructural characteristics show that such heterogeneities strongly influence the local and global evolution of the slip and twin activities, and in some cases modulate the strength anisotropy that is commonly observed in monolithic single crystals. These results may provide useful indicators toward designing novel composite Mg microstructures. & 2012 Elsevier Ltd. All rights reserved. 1. Introduction Magnesium (Mg) and its composites are potential candidates for structural applications ranging from energy-savvy automotive and aerospace sectors to biomedical components, due to its low mass density (  35% lighter than aluminum) and excellent biocompatibility. There has been a renewed emphasis toward developing novel micro-architectures with impressive specific strengths (strength/density) using pure Mg or its alloys by inducing barriers to plastic deformation through a variety of techniques including grain size refinement, nano-reinforcements, or combinations thereof (Gharghouri et al., 1998; Xu et al., 2007; Zhong et al., 2007). 1 For example, starting with pure Mg matrix, Zhong et al. Contents lists available at SciVerse ScienceDirect journal homepage: www.elsevier.com/locate/jmps Journal of the Mechanics and Physics of Solids 0022-5096/$ - see front matter & 2012 Elsevier Ltd. All rights reserved. doi:10.1016/j.jmps.2012.01.005 n Corresponding author. Tel.: þ65 6516 4496; fax: þ65 6779 1459. E-mail address: Shailendra@nus.edu.sg (S.P. Joshi). 1 Although Mg alloys may be popular starting materials from a practical standpoint, pure Mg is a good model material for fundamental investigations for such novel attempts. Journal of the Mechanics and Physics of Solids 60 (2012) 945–972