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This research examines the creep behavior of an ultrafine‐grained (UFG) Ti−6Al−4V alloy processed by equal‐channel angular pressing followed by extrusion. It is shown that modifying the surface of the UFG alloy with nitrogen ions and then applying of a coating of (Ti + V)N inhibits the softening of the UFG alloy at temperatures up to 700 K due to a barrier effect in which the coating hinders the release of dislocations onto the surface. The differences in the mechanisms of crack initiation and failure of UFG samples are also examined both with and without a coating. The prospects of the proposed approach to the improving of titanium alloys are discussed, including the formation of an UFG structure in the bulk of the material and subsequent modification by ion‐plasma methods for the manufacture of highly loaded parts operating at elevated operating temperatures.

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Abstract. An overall approach to enhance service properties of Ti alloys is based on material nanostructuring in its volume and surface layer. In this work ultrafine-grained (UFG) structure is formed in Ti-6Al-4V alloy through equal channel angular pressing via the Conform scheme with subsequent drawing. Samples modelling the shape of blades are prepared. Their surface is subjected to ion implantation with N + . Fatigue tests are performed in the conditions imitating the stress-strain state of blades. It is shown the increasing the resistance of a high-cycle fatigue of blades due to formation of the UFG structure and subsequent surface modification in the material. The fatigue behaviour of the UFG alloy subjected to ion implantation is discussed.

The mechanical behavior of the Ti-6Al-4V ELI alloy in both conventional grain size (CG) and ultrafine-grained (UFG) conditions under tension and compression at elevated temperatures (500 -800 C) is considered. Grain refinement by equal-channel angular pressing (ECAP) followed by multicycle extrusion was observed to result in a considerable improvement of superplastic characteristics of Ti-6Al-4V ELI alloy. The alloy exhibits a superplastic deformation behavior already at 600 C. The enhanced regime of superplasticity allows more efficient forming of parts and components. In addition, the UFG microstructure and, consequently, enhanced mechanical properties are kept after superplastic forming.

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XPS measurements of coarse-grained and nanostructured nitinol (Ni 50.2 Ti 49.8 ) before and after chemical treatment in hydrofluoric acid (40% HF, 1 min) are presented. The nanostructured state, providing the excellent mechanical properties of nitinol, is achieved by severe plastic deformation. The near-surface layers of nitinol were studied by XPS depth profiling. According to the obtained results, a chemical treatment in hydrofluoric acid reduces the thickness of the protective TiO 2 oxide layer and induces a nickel release from the nitinol surface and an arsenic contamination, and can therefore not be recommended as conditioning to increase the roughness of NiTi-implants. A detailed evaluation of the resulting toxicological risks is given. How to cite this article: Korotin DM, Bartkowski S, Kurmaev EZ, Borchers C, Neumann M, Gunderov DV, Valiev RZ, Cholakh SO. 2012. Arsenic contamination of coarse-grained and nanostructured nitinol surfaces induced by chemical treatment in hydrofluoric acid. J Biomed Mater Res Part B 2012:100B:1812-1816.