ABSTRACT In this paper, a microstructure-based three-dimensional (3D) finite element modeling method is adopted to investigate the effects of porosity in thin-walled high pressure die-cast (HPDC) magnesium alloys on their ductility. For this purpose, the cross-sections of AM60 casting samples are first examined using optical microscope and X-ray tomography to obtain the general information on the pore distribution features. The experimentally observed pore distribution features are then used to generate a series of synthetic microstructure-based 3D finite element models with different pore volume fractions and pore distribution features. Shear and ductile damage models are adopted in the finite element analyses to induce the fracture by element removal, leading to the prediction of ductility. The results in this study show that the ductility monotonically decreases as the pore volume fraction increases and that the effect of ‘skin region’ on the ductility is noticeable under the condition of same local pore volume fraction in the center region of the sample and its existence can be beneficial for the improvement of ductility. The further synthetic microstructure-based 3D finite element analyses are planned to investigate the effects of pore size and pore size distribution etc. INTRODUCTION Magnesium castings have found increasing applications in lightweight vehicles because magnesium and its alloys are the lightest metallic structure materials. However, a critical technical hurdle hindering the wider applications ofmagnesium castings in vehicle applications is its limited ductility. It is well established that, among various factors, microstructure-level features such as properties and distributions of porosity, brittle eutectic phases and grain size can significantly influence the ductility of magnesium castings. However, all these microstructure-level features vary from specific alloy to alloy, different casting processes, and different locations on a single casting [ 1, 2]. Although some commercial casting softwares or material models are available for the researches of magnesium castings, their predictive capability typically stops short of predicting the location dependent stress-strain behavior, particularly ductility. Previous studies [ 1, 2] have demonstrated that, for the magnesium casting samples with pore volume fraction exceeding a critical value, the extrinsic defects (i.e., porosity) can be the dominant ductility limiting factor. As the effects of porosity on the ductility of magnesium casting samples have been of interest in our study, a microstructure-based finite element modeling method has been adopted to predict the ductility of those materials by explicitly considering the different pore size and distributions [ 3, 4]. The purpose of this study is to examine the qualitative effects of pore volume fraction and ‘skin region’ of thin-walled magnesium casting samples on the ductility using synthetic microstructure-based three-dimensional (3D) finite element models. As a first step, only one constant pore size is considered in the current study before the consideration of more realistic pore distributions (i.e., different pore sizes, various pore size distributions) in the future study. Effects of Pore Distributions on Ductility of Thin- Walled High Pressure Die-Cast Magnesium2013-01-0644 Published 04/08/2013 Kyoo Sil Choi, Dongsheng Li and Xin Sun Pacific Northwest National Laboratory Mei Li Ford Motor Co John Allison University of Michigan Copyright © 2013 SAE International doi:10.4271/2013-01-0644Downloaded from SAE International by University of Birmingham, Tuesday, August 21, 2018EXPERIMENTS In this study, AM60 castings were selected to use as the experimental material. The chemical compositions of this material are listed in Table 1. Thin-walled AM60 castings of complex geometry were first produced under various high pressure die-cast (HPDC) conditions. The tensile samples, as schematically shown in