Ductile-to-brittle fracture of CP titanium with torsion deformation

In this paper, the mechanical properties and fracture mechanisms of coarse-grained (CG) commercial-purity Ti subjected to both tensile and torsion deformations are investigated. During tensile deformation, CG Ti exhibits general excellent extendibility and ductile fracture. However, CG Ti presents absolutely brittle fracture during torsion deformation, despite its high torsion deformability. This is attributed to the specific fracture mechanism in torsion that the microcracks nucleate at the surface layer and propagate from the surface to the interior of torsion sample, which is contrast to the typical microcrack nucleation and propagation behaviors of ductile metals in tension. This study has an important significance for the design and application of metals carrying torsional load.