Influence of aging products on tensile deformation behavior of Al-0.62 mass%Mg-0.32 mass%Si alloy

Tensile tests and microstructural observations were carried out to investigate the influence of aging products on tensile deformation behavior of Al-0.62 mass%Mg-0.32 mass%Si alloy. Solution-treated alloys were aged to form needle-like β" precipitates or Mg-Si clusters. The aged alloy with β" precipitates showed higher yield stress than that with Mg-Si clusters. Transmission electron microscopy observations revealed that the β" precipitates pinned dislocations. It was suggested that the strengthening types of the alloy with β" precipitates were both Orowan and cutting mechanism, by estimating the Orowan stress and considering crystal structure of β" precipitates. In contrast, the aged alloys with Mg-Si clusters showed excellent performance of uniform elongation due to large work hardening compared to those of the alloy with β" precipitates. Dislocations in the alloy with Mg-Si clusters were wavy in morphology. The yield stress of the alloy with Mg-Si clusters was higher than that of the solution-treated alloy and much lower than the estimated Orowan stress. This result indicated that the cutting mechanism was the main strengthening type of the aged alloy with Mg-Si clusters, and this strengthening mechanism gave a good balance of strength and elongation.