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.

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.

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This paper aims to study the peculiarities of a modified layer in the surface of ultrafine-grained (UFG) Ti-6Al-4V alloy after high energy ion nitrogen implantation. The UFG structure in the alloy was produced by equal channel angular pressing. X-ray diffraction analysis and scratch-testing were applied for the investigation. The influence of low-temperature annealing (400°C during 1 hour) on the substructure parameters and phase composition of the surface layer depending on a number of cycles of ion implantation with annealing was shown in the research. The effect of the UFG structure on mechanisms and strengthening degree of the surface after ion implantation is discussed.

This work studies a near-surface layer microstructure in Ti-6Al-4V alloy samples subjected to plasma electrolytic polishing (PEP) and subsequent high-energy ion implantation with nitrogen (II). Samples with a conventional coarse-grained (CG) structure with an average α-phase size of 8 μm and an ultrafine-grained (UFG) structure (α-phase size up to 0.35 μm) produced by equal channel angular pressing were used in the studies. Features of phase composition and substructure in the thin surface layers are shown after sequential processing by PEP and II of both substrates with CG and UFG structures. Irrespective of a substrate structure, the so-called “long-range effect” was observed, which manifested itself in enhanced microhardness to a depth of surface layer up to 40 μm, exceeding the penetration distance of an implanted ion he. The effect of a UFG structure on depth and degree of surface hardening after PEP and ion-implantation is discussed.