Insight into {10 1‾ 2} twinning-driven high ductility behaviors in severely deformed titanium alloy composites

The conventional approach of enhancing the strength of titanium alloys and their composites through mechanical processing to induce dislocations often leads to compromised ductility. In recent years, structural design strategies have stimulated the exploration of the material community towards deformation mechanisms and their impact on mechanical properties. Herein, we introduce the {10 1 ‾ 2} twinning to the B@Gr/TC4 composites, which were synthesized using ball milling, spark plasma sintering, hot rolling, and heat treatment processes. These composites are reinforced by in-situ formed TiC and TiB hybrid phases, achieving a high ultimate tensile strength (UTS) of 1424 MPa and fractured elongation (FE) of 13%, which are superior to those of TC4 alloy (with its UTS of 984 MPa and FE of 12%) and Gr/TC4 composite (with its UTS of 1325 MPa and FE of 12%). The enhanced strength of the composite is primarily attributed to the grain refinement and dislocation strengthening effects contributed by the high percentage of small-angle grain boundaries pinned by TiC and TiB hybrid phases. Furthermore, the twinning-induced strain softening effect is identified as the key mechanism for maintaining exceptional ductility. This study provides an effective structural strategy to simultaneously improve the strength-ductility of Ti matrix composites.