過剰Si型Al–Mg–Si合金薄板材の粒界破壊に対するひずみ速度と試験片寸法の影響

抄録

In this study, the effects of specimen size and strain rate on the intergranular fracture of Si-rich 6000 aluminum alloy sheets were investigated by using tensile tests and by finite element analysis. The tensile tests were carried out by using specimens having two different sizes, two different (coarse and fine) grain sizes, and two types of excess Si under three different strain rates including a dynamic strain rate (10⁻¹/s). With an increase in the strain rate and excess Si, the elongation decreased and the fracture mode of the intergranular fracture changed from ductile to brittle. The results of FEM analysis showed that the deformation of the grain boundary was restrained by the constraint effect of the plane strain. Therefore, the elongation of a specimen with a small aspect ratio of cross section increased as compared to that of a specimen with a large aspect ratio of cross section. The result of image analysis and the analysis of variance for the fracture surface showed that the strain rates are the most important factor determining the change of the intergranular fracture mode from ductile to brittle.