Superstrength of Nanostructured Ti Grade 4 with Grain Boundary Segregations

Severe plastic deformation and subsequent heat treatments yield nanostructured commercially pure (CP) titanium Grade 4 with average grain size of about 100 nm and exceptional strength. To elucidate the underlying strengthening mechanisms in this nanotitanium (nanoTi), this study uses atom probe tomography (APT) to analyze the atomic structure of grain boundaries and assess impurity segregation. Results reveal the formation of grain boundary segregations, primarily composed of iron (Fe) atoms, reaching concentrations up to 3.3 ± 0.2 at% in localized regions. The average width of these segregation layers is 6.13 ± 0.45 nm. The paper considers a mechanism for forming these segregations and discusses relevant theoretical models describing their contribution to the material’s enhanced strength.