Achieving superior strength-ductility and prolonged strain hardening effects in Ti matrix composite reinforced with FCC-Ti and intragranular TiC

Achieving exceptional strain hardening is a promising strategy for simultaneously enhancing the strength and ductility of titanium matrix composites (TMCs). In this study, a novel carbon-based nanomaterial, namely polypyrrole (PPy), was used to fabricate TMCs reinforced with intragranular titanium carbide (TiC) through spark plasma sintering and hot rolling. Concurrently, face-centered cubic of titanium (FCC-Ti) was formed through the synergistic effects of high local stress field and interstitial solid solution oxygen atoms. The ultimate tensile strength and uniform elongation of the Ti-0.6PPy composites reached 1029 MPa and 11.3%, representing a 67% and 88% improvement over the pure Ti (614 MPa, 6.0%), respectively. The significantly enhanced strength was benefited from the O atoms solid solution strengthening and Orowan strengthening. Ex-situ EBSD combined with TEM characterization were conducted to analyze the microstructure of the deformed Ti-0.6PPy composites. It had revealed that dislocation hot spots moved from grain boundaries to the grain interiors and surrounded to the new formed FCC-Ti phase. This transformation enhanced the dislocation storage capacity, led to higher dislocation density and prolonged strain hardening, thereby achieved superior uniform elongation and ductility.