ICF100902PR HIGH STRAIN RATE DEFORMATION BEHAVIOR OF AL-MG ALLOYS T. Masuda1, T. Kobayashi2 and H. Toda2 1Graduate Student, Graduate School of Toyohashi University of Technology 2Department of Production Systems Engineering, Toyohashi University of Technology, Toyohashi-city, AICHI, 441-8580, Japan ABSTRACT The aim of the present study is to characterize the strain rate dependency and the microstructural change behavior of Al-Mg series alloys over a wide range of strain rate. Impact tensile tests are carried out using a split-Hopkinson bar apparatus and servo hydraulic testing machine. SEM observation is made to analyze the microstructural changes of fracture surface. Al-Mg alloys show an increase in 0.2% proof stress, ultimate tensile strength, elongation, reduction of area and work hardening exponent with increasing strain rate. Although strain rate dependency of the stress and work hardening exponent are negligible up to the strain rate of approximately 102s-1, the extent of rate sensitivity appears to increase from this strain rate. The elongation and reduction of area show linear increases with increasing strain rate. Although fracture surfaces mainly exhibit the shear type dimple pattern under the low strain rates, ordinary equiaxed dimple fracture is observed under the high strain rates. KEYWORDS Hopkinson bar, strain rate dependency, Al-Mg series alloys, impact tensile test, SEM, fracture surface, dimple, impact stress-strain curve INTRODUCTION The dynamic deformation behaviors of materials have become increasingly important in many applications related to the design especially in the field of transportation industry such as automobiles. Because Al-Mg series alloy has superior mechanical properties such as a high strength/weight ratio, good corrosion resistance and deformability, it is considered for many advanced applications where the structural components are subjected to dynamic loading. In order to optimize deformation and fracture performance of this alloy under the high strain rates, it is necessary to understand the dynamic deformation mechanisms [1]. It is recognized that materials often respond in different ways to high strain rate loading as compared to low strain rate loading. As strain rate is increased from static to dynamic, it results in an increase of the strength with increasing strain rate. Further, the flow stress of a material depends not only on the strain and strain rate but also on its microstructure especially at the dislocation level. In order to combine the micromechanisms of deformation and macroscopic constitutive relationships, there is a need to understand the microstructural changes which take place during deformation [2,3]. Therefore, it is the purpose of this work to study the
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