Abstract
In order to reveal the controlling factors of stretchability in Al–Mg–Si alloys, the Erichsen tests, tensile tests and metallographic observations were carried out. There appeared to be little correlation between tensile elongation and the Erichsen value and good correlation between 0.2% proof stress and the Erichsen value. The Erichsen value increased with the decrease of 0.2% proof stress and increased with the decrease of grain size. Fractographic observation revealed that the frequency of the occurrence of intergranular fracture increased with the increase of 0.2% proof stress, and that the fractography changed from intergranular fracture to transgranular fracture by the grain refinement. Dimple patterns were observed on the intergranular fractured surface and it suggested that precipitates on the grain boundary caused ruptures. These results showed that the decrease of precipitates on the grain boundary or the refinement of grain size was effective for the improvement of stretchability in Al–Mg–Si alloys.
