# Effect of Ti-B Grain Refiners on Wear and Corrosion of the A332 Alloy with Sr Modification
## 5 Conclusions  
A comparison between two grain refiners (Al5 Ti2B and Al5 Ti1B) shows that their use promoted an effective grain size reduction. Corrosion analyses show some mechanisms related with phase interactions, furthermore, the elastic modulus of the phases helps to understand their influence in the hardness and corrosion mechanisms. The following conclusions were drawn from this work:  
* Effective dispersion of grain refinement was achieved when using the melting temperature of 750 \({}^{\circ}\)C. The procedure adopted can be used to insert the Al5 Ti1B and Al5 Ti2B master alloys in the A332 alloy with an induction furnace. * The morphology of elongated arms of dendrites of primary aluminum changes to more equiaxed grains when the grain refiners (Al5 Ti1B or Al5 Ti2B) are added. This modification of the shape and size of the grains results from increasing the formation of solidification nuclei through different refining utilized. Furthermore, the image analysis allowed a note of the modifications from acicular-shaped to lamellar due to the presence of the Sr modifier. * The fundamental function of the grain refiner was successfully obtained using both master alloys. The grain refiners (Al5 Ti2B and Al5 Ti1B) are adequate to achieve smaller grain sizes for the A332 aluminum alloy compared to as-cast conditions,probably promoting adequate places for heterogeneous nucleation. Al5 Ti1B was the most effective grain refiner, reducing (33.3 \(\pm\) 3.3 \(\upmu\)m) in comparison with Al5 Ti2B (38.8 \(\pm\) 4.4 \(\upmu\)m). * The average hardness increased after adding grain refiner due to the Hall-Petch relation and Fe-based intermetallic phase length increases. Albeit the non-homogeneous grain size through the samples led to a significant variation in the values of the standard deviation factor. Hence, it is not possible to confirm if there is any improvement in microhardness with the addition of different refiners. * In the combined addition of grain refiner and modifier samples, Fe-based intermetallic phase Al\({}_{5}\)FeSi measurements indicate an increase in the phase length. The Al5 Ti2B condition presents volumetric fraction values (4.2 \(\pm\) 0.74%) slightly higher than the other (Al5 Ti1B), around 3.6 \(\pm\) 1,45%. This higher fraction of Al\({}_{5}\)FeSi could be responsible for the slight difference in the wear resistance. The data index \(\frac{\text{H}^{2}}{\text{E}_{\text{e}}^{2}}\) obtained from the nanoindentation analysis shows a relation with the higher resistance to the wear of the Al\({}_{5}\)FeSi phase. * Addition of grain refiners improved the relative wear resistance. Although the difference between them is modest because the values are 1.359 to Al5 Ti2B and 1.353 to Al5 Ti1B, both values are higher to those of the as-cast condition (1), used as a reference. The observed effect might be linked to a refinement and an increase in the length of the intermetallic particles Al\({}_{5}\)FeSi, which would be related to the improved wear resistance of the aluminum alloy A332. * A relation between corrosion resistance and addition of grain refiner cannot be established. While Al5 Ti2B has shown an overall decrease in corrosion resistance, Al5 Ti1B has an enhanced performance. Nonetheless, pitting morphology should be considered before the use of grain refinement. Although the pitting formation started at a higher corrosion potential with the use of grain refiners, the optical microscopy images have shown deeper pits. Furthermore, the Al\({}_{5}\)FeSi phase acts as a cathodic function in the corrosion reaction, dissolving the adjacent matrix, primary aluminum, and generating pit growth. Conceptualization, H.D.C.F., B.E.A. and L.A.L. ; methodology, B.E.A., A.R.M., W.R.d.O., L.A.L. and H.D.C.F. ; validation, W.R.d.O., A.R.M., E.M.-C. and H.D.C.F. ; formal analysis, W.R.d.O., A.R.M., B.E.A. ; investigation, B.E.A., H.D.C.F., A.R.M. and W.R.d.O. ; resources, H.D.C.F., E.M.-C. and L.A.L. ; data curation, H.D.C.F. and L.A.L. ; writing--original draft preparation, B.E.A. and H.D.C.F.