Development of Al-Nb-B master alloys using Nb and KBF4 Powders

We recently reported that the combined employment of niobium and boron (i.e. Nb-based intermetallics formed in the melt by the addition of powders), instead of niobium or boron individually, is a highly effective way to refine the grain size of Al-Si alloys without the inconvenience of the poisoning effect typical of commercial Al-Ti-B master alloys. In this work the progress concerning the development of Al-xNb-yB master alloys, which are much more suitable for its use in aluminium foundries, is reported and discussed. Precisely, a first approach to produce Al-xNb-yB master alloys as well as its characterisation by means of EDS mapping and TEM is presented. The study is completed by testing the effectiveness of the produced Al-xNb-yB master alloys on pure aluminium and binary Al-10Si alloy as well as commercial hypoeutectic and near-eutectic Al-Si alloys. It is found that the approach employed to produce the Al-xNb-yB master alloys is suitable because the size of the primary alpha-Al dendrites is significantly reduced in each of the case investigated. (C) 2015 The Authors. Published by Elsevier Ltd.