Grain refining potency of Nb–B inoculation on Al–12Si–0.6Fe–0.5Mn alloy

In a recent work we reported that the combined addition of Nb and B has higher grain refinement effectiveness than the addition of these individual chemical elements. In this work a commercial Al–12Si–0.6Fe–0.5Mn alloy is employed to fully characterise the refining potency of Nb–B inoculation. It is found that the addition of Nb powder and KBF4 flux to Al–Si melt introduces potent nuclei with low lattice mismatch with the primary α-Al dendrites (i.e. low undercooling) and, thus, promote noteworthy grain refinement through heterogeneous nucleation. Nb–B inoculation induces a significant increment of the volumetric number of grains, decreases the undercooling needed for solidification and makes the grain size of the Nb–B inoculated material less sensitive to the cooling rate employed to solidify the material.