Impact-resistant titanium alloy with fine equiaxed structure fabricated by powder metallurgy

Abstract

Although fine equiaxed structure benefits both strength and ductility in titanium alloys, it is often considered incompatible with high toughness, for its insufficient ability to deflect propagating cracks compared to coarse lamellar structure. This work reports an excellent combination of standard Charpy impact toughness (∼100 J) and yield strength (∼820 MPa) in a powder metallurgy titanium alloy with fine equiaxed structure (∼1.5 μm), wherein the β matrix exists as equiaxed nodules and fine ligaments for globularization of α grains. The impact curve divided with the “compliance changing rate” (CCR) method indicates that the energy consumed by crack propagation is dominant (∼82%) during the impact process. Fractographic and structural examinations indicate that multiple micro-voids nucleation near boundaries between fine β ligaments and α grains mitigates local stress concentration, and that coordinated deformation between equiaxed β nodules and α grains hinders crack propagation, which together enable the excellent combination of yield strength and impact toughness. Our work provides a new pathway for designing impact-resistant titanium alloys.