Microstructure and grain refining efficiency of Al-5Ti-1B master alloys prepared by halide salt route

A1-5Ti-1B master alloys were prepared by reacting K2TiF6 and KBF4 salts with Al melt. During the reaction period between the fluoride salts and Al melt, the non-homogenous distribution of solutes B and Ti in the Al melt close to the salts/Al melt interface causes the formation of the unstable AIB(2) phase. The AIB(2) phase transforms to TiB2 particles by the diffusion of solutes Ti and B in the Al melt during the afterward holding temperature period, which causes an increase both in the number density of TiB2 particles and in the grain refining efficiency of the master alloys. After the transformation of AIB(2) phase to TiB2 phase, TiB2 particles coarsen by Ostwald ripening, which leads to a decrease both in the number density of TiB2 particles and in the grain refining efficiency of the master alloys. (C) 2017 Published by Elsevier B.V.