The Study of Some Al-5%Ti and Al-5%Ti-1%B Master Alloys

Several Al-5 wt.% Ti, Al-5 wt.% Ti-1 wt.% B master alloys and the Al castings grain refined by these master alloys were studied. Metallographic, SEM and TEM analyses suggest that the Al sub 3 Ti phase and the (Al sub 1-x , Ti sub x )B sub 2 phase in the master alloys are two potent nuclei for the alpha -Al. The nucleating efficiency of the Al sub 3 Ti phase fades rather fast with the contact time, whereas the efficiency of the (Al sub 1-x , Ti sub x )B sub 2 phase persists for > 2 h. The spatial distribution of the (Al sub 1-x , Ti sub x )B sub 2 particles is a sensitive factor for the grain refinement efficiency of an Al-Ti-B master alloy.