This work deals with the study of strength and ductility in ultrafine‐grained (UFG) Ti Grade 4 produced by equal channel angular pressing (ECAP) in combination with subsequent thermomechanical treatments. We found that additional annealing of UFG Ti resulted in unusual enhancement of strength and ductility, which is associated with not only small grain size but also with a grain boundary structure. The origin of this phenomenon is investigated using the results of transmission electron microscopy and atom probe tomography. The innovation potential of UFG Ti for medical use is considered.

Bulk nanocrystalline Ti bars (Grade 4, Φ4 × 3000 mm(3)) were massively fabricated by equal channel angular pressing (ECAP) via follow-up conform scheme with the microcrystalline CP Ti as raw material. Homogeneous nanostructured crystals with the average grain size of 250 nm were identified for the ECAPed Ti, with extremely high tensile/fatigue strength (around 1240/620 MPa) and adorable elongation (more than 5%). Pronounced formation of bonelike apatite for the nanocrystalline Ti group after 14 days static immersion in simulated body fluids (SBF) reveals the prospective in vitro bioactive capability of fast calcification, whereas an estimated 17% increment in protein adsorption represents good bioaffinity of nanocrystalline Ti. The documentation onto the whole life circle of osteoblast cell lines (MG63) revealed the strong interactions and superior cellular functionalization when they are co-incubated with bulk nanocrystalline Ti sample. Moreover, thread-structured specimens were designed and implanted into the tibia of Beagles dogs till 12 weeks to study the in vivo responses between bone and metallic implant made of bulk nanocrystalline Ti, with the microcrystalline Ti as control. For the implanted nanostructured Ti group, neoformed bone around the implants underwent the whole-stage transformation proceeding from originally osteons or immature woven bone to mature lamellar bone (skeletonic trabecular), even with the remodeling being finished till 12 weeks. The phenomenal osseointegration of direct implant-bone contact can be revealed from the group of the ECAPed Ti without fibrous tissue encapsulation in the gap between the implant and autogenous bone.

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The results of fatigue tests to determine the properties of commercially pure ultrafinegrained (UFG) Ti long-length rods processed by severe plastic deformation are presented. Fatigue tests were carried out on smooth and notched samples. It is shown that the formation of a UFG structure in Ti rods resulted in enhancement of the fatigue strength of smooth and notched samples.