AlB5% has AlB2 phases, but how to avoid the agglomeration problem during casting to get the uniform distribution? Is any additive or salt activators is to be added in the melt?
You may try adding a modifier element to the melt, such as Mg or Ca, to lower the surface tension of the Al-rich melt, to facilitate the dispersion of the intermetallic particles in your final product. Below, a paper shows this effect on SiC particles.