A multi-scale model for description of strain localization in friction stir welded magnesium alloy

Abstract

Friction stir welding has many advantages over the traditional fusion welding process and has great potential application to magnesium alloy. The deformation behavior of the welded joint is one of the topics under investigation. Strong strain localization is generally observed during tension and compression of friction stir welded magnesium alloy. In this work, numerical simulations are performed to investigate the deformation behavior and the underlying mechanisms of friction stir welded magnesium alloy. A multi-scale model is proposed, in which the macroscopic model is used to describe the macroscopic deformation while the mesoscopic model is adopted to analyze the deformation mechanisms and predict the texture evolution. The two scale models are sequentially coupled. The parameters’ evolution of the macroscopic model is dependent on the meso-scale calculation while the strain path of the meso-scale calculation comes from the macroscopic modeling. In current work, the Cazacu model (Plunkett et al., 2006) and the VPSC model (Lebensohn and Tomé, 1993) are used as the macroscopic model and the mesoscopic model, respectively. It is demonstrated that the non-uniform macroscopic deformation of the friction stir welded magnesium alloy can be well represented by the proposed model. The mesoscopic analysis indicates that different deformation mechanisms (slip or twinning) dominate the plastic deformation in different sub-regions of the joint and that the activation of the tensile twinning significantly affects the strain distribution and the deformed texture.