The formation of AlN and TiN particles during nitrogen bearing gas injection into Al–Mg–Ti melt

The fabrication of AlN–TiN/Al composites through nitrogen-bearing gas injection into Al–Mg–Ti melts was experimentally and analytically studied. It is shown that AlN and TiN particles can be formed by the in situ reaction of mixture gas (N2 + NH3) with Al–Mg–Ti melts. The titanium in melts and NH3 in mixture gas can promote the reaction and shorten the treatment time. It was considered that AlN and TiN are formed by the direct reaction of Al and Ti with nitrogen bearing gas at the interface of gas bubble and melt, and the AlN and TiN particles formed have the tendency of moving upwards together with gas bubbles, which results in uneven distribution of particles in melts. A method to promote the formation of AlN and TiN particles and to get composites with uniform microstructure was also suggested.