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Shusen Wu State Key Lab of Materials Processing and Die & Mould Technology, Huazhong University of Science and Technology, Wuhan 430074, People’s Republic of China (Received 29 October 2014; accepted 10 February 2015)

High performance die castings are urgently expected to be used as structural components subjected to dynamic loading. Therefore, tensile properties, fatigue, and corrosion-fatigue behavior of automotive die cast AlMg5Si2Mn alloy are studied in the current work. The results indicate that the tensile strength and yield strength of the as-cast specimens are obviously lower than those of the age-treated specimens, while the elongation decreases with increasing aging time. Neutral corrosive environment (3.5% NaCl solution) dramatically decreases the fatigue limits from 75 to 50 MPa. Fatigue lives of the directly corroded and precorroded specimens are close to each other. The values of material constants m and C are in the range of 5.756–5.874 and 2.421
1010 to 4.285
109, respectively. Obscure fatigue striations and featureless facets are observed in crack propagation regions. Anodic dissolution is dominantly responsible for the premature crack initiation and stress corrosion cracking leading to the formation of fractured a-Al matrix.

I. INTRODUCTION

High pressure die casting (HPDC) is a promising near net shape technology due to the eco-friendliness, good efficiency, and flexibility. Die castings possess good outlook, dimensional accuracy, and integrity, thus they are greatly expected to be used as automotive structural components (e.g., suspensions and B pillars1,2). Those components should own thin walls, complicated structures, and good toughness to reduce the weight of car body, moreover, they should also have moderate corrosion resistance due to the severe air pollution today. To produce those high-duty structural components economically, several high performance die-cast aluminum alloys with a low Fe-content (#0.2%) were developed.3 As compared to other die cast alloys, AlMg5Si2Mn alloy has several advantages: Reduction of heat treatments, good corrosion resistance, and elongation.4 Consequently, mechanical properties and microstructure segregation of AlMg5Si2Mn alloy have been extensively studied. For instance, Ji et al.5,6 systematically studied the tensile properties of AlMg5Si1.5MnFe0.25Ti0.2 alloy and highlighted its excellent elongation (d 5 15%). Kaufmann and Uggowitzer4 compared the mechanical properties of die casting, squeeze casting, and semisolid casting AlMg5Si2Mn specimens, and they found that die casting

specimens possess superior mechanical properties due to the finer average grain size and lower porosity. Otarawanna et al.7,8 documented that the interaction of liquid alloys, which have different solid fractions, is dominantly responsible for the formation of segregated microstructures, such as surface layer and shear bands. Thus, previous research mainly focused on the static mechanical properties of HPDC AlMg5Si2Mn alloy, while the research on its dynamic mechanical behavior wa