Nanostructuring of Ti-alloys by SPD processing to achieve superior fatigue properties

Abstract

This work is related to the enhancement of the fatigue properties in ultrafine-grained Ti alloys produced by severe plastic deformation techniques. To process commercially pure Ti Grade 4 and Ti-6Al-4V alloys, combined severe plastic deformation techniques that include equal channel angular pressing and additional thermal and deformation treatments were used. As a result we could produce ultrafine-grained Ti materials with a similar grain size of less than 300–400 nm but different in their shape and grain boundary structure (both low- and high-angle, equilibrium and non-equilibrium grain boundaries). It is shown that tailoring grain boundaries by severe plastic deformation techniques makes it possible to considerably enhance the strength of Ti materials while preserving high ductility. In turn, ultrafine-grained materials with enhanced strength and ductility demonstrate superior fatigue endurance and life.

Mechanical behavior and impact toughness of the ultrafine-grained Grade 5 Ti alloy processed by ECAP

“…A final one-hour annealing was imposed at 773 K for reducing the internal elastic stresses without inducing significant growth of the grains [5,20]. The state produced by ECAP and extrusion will be further referred to as «UFG1».…”

Influence of phase volume fractions on the processing of a Ti–6Al–4V alloy by high-pressure torsion

“…Several reports are now available describing the processing of pure Ti by ECAP [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23] and HPT [24][25][26] and there are also some reports on the processing of the Ti-6Al-4V alloy by ECAP [27][28][29][30] and HPT [31][32][33][34]. Nevertheless, a review of these data shows that all of the experiments were conducted using commercial Ti-6Al-4V alloys that were processed in the hot-rolled or extruded condition.…”

Processing of an ultrafine-grained titanium by high-pressure torsion: An evaluation of the wear properties with and without a TiN coating

“…A corrosion study reported superior corrosion resistance in UFG Ti due to rapid passivation along the grain boundaries (Balyanov et al, 2004). The fatigue life of Ti is enhanced by SPD so that in Grade 4 Ti the fatigue limit after 10 7 cycles was increased to $590 MPa using ECAP compared with $350 MPa in the coarse-grained (CG) condition (Semenova et al, 2008(Semenova et al, , 2009Estrin and Vinogradov 2010). Recent research on biocompatibility has documented improved pre-osteoblast attachment and rate of growth on UFG pure Ti compared with CG pure Ti and Ti-6Al-4V substrates, where this is attributed to the presence of surface discontinuities, the surface energy, a higher wettability and the presence of stable TiO 2 films which improve the protein adsorption on the surface (Faghihi et al, 2007;Park et al, 2009;Bindu et al, 2009).…”