Recent Advances in the Design and Fabrication of Strong and Ductile (Tensile) Titanium Metal Matrix Composites

Titanium metal matrix composites (TiMMCs) offer much improved strength, elastic modulus, and wear resistance at both room and elevated temperatures but often at the expense of tensile ductility, which excludes them from most key engineering applications. Recent advances show that this long-standing strength-ductility dilemma can be controlled to a large extent by adopting novel design concepts based on powder metallurgy (PM). These include: 1) reinforcing the Ti matrix with a three-dimensional (3D) network-like architecture of TiB whiskers or nanowires; 2) the use of nanostructured carbon precursors (nanotubes, fibers, and graphene) to enable in situ formation of TiC reinforcements; and 3) the exploitation of “ductility-detrimental” interstitial elements (O, N, H) for strengthening. On a laboratory scale, the fabricated TiMMCs all exhibit an excellent combination of tensile strength and elongation, comparable to, or even better than, solution-treated and aged (STA) wrought Ti–6Al–4V. The mechanisms behind these novel developments are analyzed. New insights into the design and fabrication of stronger and more ductile (tensile) TiMMCs are offered.