In-situ TiC particle reinforced Ti–Al matrix composites: powder preparation by mechanical alloying and selective laser melting behavior

Mechanical alloying of Ti–Al–graphite elemental powder mixture was performed to synthesize
nanocomposite powder with Ti(Al) solid solution matrix reinforced by in-situ formed TiC particles. The
evolutions in phases, microstructures, and compositions of milled powders with the applied milling
times were investigated. It showed that with increasing the milling time, the starting irregularly shaped
powder underwent a successive change in its morphology from a flattened shape (10 h) to a highly
coarsened spherical one (15 h) and, eventually, to a fine, equiaxed and uniform one (above 25 h). The
prepared TiC/Ti(Al) composite powder was nanocrystalline, with the estimated average crystallite size of
12 nm and of 7 nm for Ti(Al) and TiC, respectively. Formation mechanisms behind the
microstructural development of powders were elucidated. The Ti(Al) solid solution is formed through
a gradual and progressive solution of Al into Ti lattice. The formation of TiC is through an abrupt,
exothermic, and self-sustaining reaction between Ti and C elements. Selective Laser Melting (SLM) of asprepared
TiC/Ti(Al) composite powder was performed. The TiC particle reinforced TiAl3 (a major phase)
and Ti3AlC2 (a minor phase) matrix composite part was obtained after SLM. Although a slight grain
growth occurred as relative to as-milled powder, the SLM processed composites still exhibited a refined
microstructure.