The Aspects of Practical Application of Ultrafine-Grained Titanium Alloys Produced by Severe Plastic Deformation

Abstract

The mechanical and physical properties of ultrafine-grained titanium alloys produced by severe plastic deformation are considered. It is found that the formation of ultrafine-grained structure in these materials causes a significant enhancement in their mechanical properties at room temperature and in their resistance to hydrogen embrittlement as well as a change in their acoustic properties. Moreover, superplasticity is realized in these materials at less elevated temperatures relative to the respective coarse grained counterparts. It is shown that the above changes in material properties permit optimization of conditions by the production of items from the titanium alloys, e.g. medical implants having the requisite strength and stepped waveguides having long life even in the high power density conditions of an ultrasound system.

Effect of Hydrogen on the Development of Superplastic Deformation in the Submicrocrystalline Ti–6Al–4V Alloy

“…1, b). This character of flow curves is often observed during superplastic deformation of submicro-and nanocryctalline metals and alloys [1][2].…”

“…Interest in such materials is primarily caused by their unique physical-mechanical properties that are substantially different from those of coarse-and fine-grained analogs. For example, for SMC (α + β) titanium alloys superplastic flow is observed already at 873-973 K [1][2], whereas for fine-grained (grain size 2-10 µm) alloys it is observed at temperatures above 1100 K [3].…”

Strength and Fatigue Life at 625 K of the Ultrafine-Grained Ti-6Al-4V Alloy Produced by Equal-Channel Angular Pressing

“…However, the real application of UFG Ti alloys in aircraft engine building requires studying a whole range of mechanical properties, including long-term strength at operating temperatures [40,41]. The previously conducted long-term strength tests of the UFG Ti-6Al-4V alloy at operating temperatures (not higher than 350 • C) show its obvious advantage over its coarse-grained counterpart [27].…”

Fatigue Properties of Ti Alloys with an Ultrafine Grained Structure: Challenges and Achievements

“…Such a behavior makes grain refinement an efficient factor for improving a material's resistance to hydrogen embrittlement, underlain by a decrease in hydrogen's 'effective' diffusion rate value, due to a decrease in the relative fraction of hydrogen per area unit of a grain boundary. Another paper [99] examined the effect of increasing the resistance to hydrogen embrittlement of the UFG Ti-6Al-4V alloy, by means of increasing its maximum permissible hydrogen concentration in comparison to the CG state. A paper [100] showed that the elongation and impact toughness of nanocrystalline Ti with a hydrogen content from 0.1 to 5 at.% are practically the same, while in microcrystalline Ti they decrease when hydrogen is added, which indicates a lower risk of hydride-induced embrittlement in nanocrystalline Ti than in its microcrystalline counterpart.…”