INFLUENCE OF THE MAGNESIUM CONCENTRATION ON THE RELATIONSHIP BETWEEN FRACTURE MECHANISM AND STRAIN-RATE IN HIGH-PURITY AL-MG ALLOYS

In order to clarify the influence of magnesium atomic concentration in the solute on interaction with dislocations, Al-Mg binary alloys with various magnesium contents from 1.8 wt.% to 8.4 wt.% and aluminium in high purity were prepared. Furthermore, the influence of magnesium concentration on the fracture mechanism of these alloys has been investigated in the wide strain rate range from 1 x 10(-4) to 2 x 10(3) s(-1) at room temperature. Total elongations of prepared materials are larger at high strain rates. We suggest models of void nucleations, which are valuable for strain rates and concentrations of magnesium. Fractographs obtained by scanning electron microscopy observation revealed that the voids are very close together in alloys with high magnesium content, while void growth occurs to give a large ductile dimple failure in alloys with low magnesium content as the failure progresses. Large total elongations at high strain rates are caused by the change in the mode of void growth.