Abstract
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.
Highlights
It is highly desirable to obtain a structure of refined grains in the Al-Si alloys due to the gain in mechanical properties in terms of resistance and elasticity in the cast parts
Mahta et al.[3] reports that the presence of the element Fe in the Al-Si alloys, even in small amounts, promotes the formation of the intermetallic phase β-Al5FeSi (β-Fe), with morphology in the form of a plate or needle, which deteriorates the mechanical properties of the material
Can see further evidence of heterogeneous nucleation of α-Al grains in the study of Bolzoni and Babu[11] where it was demonstrated that the Al3Nb and NbB2-based heterogeneous nuclei have substrates that present a typical tetragonal and hexagonal plate-like morphology, respectively, as per the TEM bright image shown in Figure 4 of the NbB2 substrates
Summary
It is highly desirable to obtain a structure of refined grains in the Al-Si alloys due to the gain in mechanical properties in terms of resistance and elasticity in the cast parts. % Fe were used as the base alloys to analyze the effect of Nb addition via Al4Nb-0.5B master alloy in the size of the α-Al grain, eutectic phase of Al-Si, and intermetallic precipitates.
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