Hybrid Modification of Microstructure and Tensile Properties of A319 Alloy by Heat Treatment and Be Addition

The microstructure and tensile properties of A319 aluminum alloy were modified by three methods including the addition of three different amounts of beryllium, T4 heat treatment, and a hybrid method of adding 0.06 wt.% Be plus T4 heat treatment. The optimal amount of Be was 0.06 wt.%, which resulted in almost the absence of the β-phase and the best aspect ratio of the α-phase and changed the coarse acicular Si to fibrous Si. However, the T4 heat treatment distributed the phases uniformly, but it could not inhibit the formation of the β-phase. The hybrid method led to the best results since the addition of Be caused the formation of the α-phase, prevented the formation of the β-phase and distributed the phases uniformly. Moreover, the fracture mode in the sample modified by the hybrid method was completely ductile while the other samples exhibited a contribution of brittle fracture to some extent.