Effect of ferrous primary crystals on cavitation in Al–4.5 mass%Mg alloys during creep deformation

Abstract

Deformation and cavitation characteristics have been investigated at 613∼693 K for Al–4.5 mass%Mg–0.05 mass%Fe and Al–4.5 mass%Mg–0.2 mass%Fe alloys with grain size of 50 μm. The alloys showed strain-rate sensitivity of 0.3 over a strain-rate range from 10⁻⁵ s⁻¹ to 10⁻² s⁻¹ and elongation-to-failure above 300% at a strain-rate of 1 × 10⁻³ s⁻¹. The results indicates that the alloys behave like Glass I type which deformation is controlled by dislocation glide dragged by solute atoms. Cavitation was increased by increasing iron content for all strains. Most cavities were nucleated at the interface between ferrous primary crystal and matrix and elongated parallel to the tensile direction. The critical diameter of the primary crystal, above which cavity is nucleated, was 1.5 μm at grain boundary and 0.5 μm at grain interior, which were very close to the theoretical results.