Exceptional dislocation plasticity and amorphization of stack-faulted TiB intermetallic compound in the reinforced titanium alloys

The incorporation of TiB reinforcing phase is widely employed to enhance the mechanical properties of titanium alloys, with the resulting improvements generally attributed to its overall reinforcement effect and associated modifications in the matrix microstructure. However, fundamental understanding of the intrinsic microscopic deformation mechanisms within the TiB phase itself remain limited. In this study, the deformation behaviors of TiB unidirectional whiskers embedded in a Ti-6Cr-5Mo-5V-4Al high-strength titanium alloy are systematically investigated by integrating experimental characterizations with first-principles calculations. It is demonstrated that TiB whiskers, traditionally classified as hard-and-brittle intermetallic compounds, exhibit exceptional dislocation plasticity and even amorphization in the Ti alloy under applied loading. This unconventional plasticity is closely linked to the highly anisotropic distribution of grown-in stacking fault (SF) nanobundles within the TiB whiskers. The pre-existing SF nanobundles act as effective barriers to dislocation slip, facilitate dislocation-SF interactions, and promote progressive dislocation accumulation, ultimately leading to the formation of unique 3D amorphous bands along the TiB whiskers, as rationalized by crystallographic orientation analysis and energy landscape calculations. These findings unveil the underlying deformation mechanisms of TiB reinforcing phase, suggesting that the plastic potential of traditionally hard-and-brittle phases can be exploited in the microstructural design.