Optimization of Casting Process Parameters for Synthesis of Al-Nb-B Master Alloy

Al-Nb-B master alloys were synthesized using commercial pure aluminum, niobium, and KBF4 salts. Two different sources of Nb (pure Nb powder and Al-60%Nb powder) were used to prepare the master alloy. Casting process parameters such as reaction time and melt stir time interval were varied to enhance the formation of in situ intermetallic particles in the master alloys. The size, shape and distribution of intermetallic particles in these master alloys were studied using microscopy techniques. The results show that the Al-5Nb-1B master alloy prepared with Al-60%Nb powders has a uniform distribution of intermetallic particles as compared to the master alloy prepared with pure Nb powders. Increase in boron content from 1 wt.% to 2 wt.% in the master alloys resulted in a higher fraction of intermetallic particles. Among all the master alloys synthesized, Al-5Nb-2B was observed to have the highest number of well-distributed intermetallic particles which could act as potential grain refiners of aluminum alloys.