Interfacial/intragranular reinforcement of titanium-matrix composites produced by a novel process involving core-shell structured powder

Abstract

Powder metallurgy (P/M) route is commonly adopted to fabricate titanium-matrix composites (TMCs). However, majority of the reinforcements are distributed along the grain boundaries, but are absent within the grains, such that the desired mechanical properties are rarely obtained. We have developed a novel process of interfacial/intragranular reinforcement of TMC involving core-shell structured carbon nanotubes (CNTs)/amorphous-C coated Ti–6Al–4V composite powder. In comparison to pristine Ti–6Al–4V alloy, the addition of 0.25 wt% C led to more than 500 MPa increase in compressive yield strength. This is ascribed to the synergistic strengthening effect of interfacial-distributed CNTs/TiC nanoparticles and intragranular-distributed TiC nanoplatelets. The friction coefficient was effectively reduced by more than 30% because of the pinning effect of uniform TiC nanoplatelets that were deeply embedded inside the Ti–6Al–4V matrix.