Grain refinement in Al-Si alloys improves their mechanical properties. Research available in the literature shows the search for refinement efficiency through heterogeneous nucleation of the grain, involving the stoichiometric ratio between the alloy elements, the inoculant, and process parameters. In these surveys, there are divergences of information. However, this study does not aim to contradict this information but present an investigation made with the Al-4Nb-0.5B master alloy, where Nb >> B, used via sticks, with variations from 0 to 1 Wt.% of Nb and B according to a stoichiometric calculation added to the alloys cast with Al (7, 9, 12) Wt.% of Si and 1 Wt.% of Fe. The study also enabled an investigation into the morphology behavior of the β-Fe precipitates arising from Fe-critic in the alloy. Samples cast according to the TP1-2012 mold standard. The alloy microstructure analyzed was by energy-dispersive X-ray spectroscopy. The small addition of Nb-B can efficiently and significantly refine the size of the primary α-Al grain and has caused changes in the morphology of Fe-rich intermetallic, which became very refined spheroidised, suggesting an improvement in the mechanical properties of the material.

Many components for aerospace and automotive industries are currently manufactured using superplastic forming, being the fine-grained aluminum alloy AA5083 widely used for this proposes. However, the development of cavitation voids is inherent in this process and reduces the ductility of the alloy. Back pressure can be used to diminish the growth of cavitation void. The experimental conditions used in this work are in the best condition for nucleation and grow of cavitation, because of the coarse grain size (81 µm), large second phase particles (9 µm) and elevated test temperature (570ºC) in a AA 5083. Domes were formed at 570ºC and at a strain rate of 5x10-5 s-1 by blow forming with and without back-pressure. They were compared in terms of their final shape, thickness distribution, and quantity of cavitation voids. The effectiveness of the usage of back pressure to reducing the quantity of cavitation void was analyzed.