Effect of rolling-assisted deformation on the formation of an ultrafine-grained structure in a two-phase titanium alloy subjected to severe plastic deformation

Features of Duplex Microstructural Evolution and Mechanical Behavior in the Titanium Alloy Processed by Equal‐Channel Angular Pressing

“…Studies of microstructure transformation with increasing strain in the VT8M‐1 alloy during ECAP processing revealed several similar effects to those observed earlier in the Ti–6Al–4V alloy: specifically, a destruction and spheroidization of the α‐phase plates which leads to the formation of equiaxed ultrafine grains/subgrains and a fragmentation of the primary α‐phase grains with the formation of a wealky‐misoriented substructure . It is also interesting to note the difference in the evolution of the phase compositions of the Ti–6Al–4V and VT8M‐1 alloys.…”

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

“…In the two-phase α + β regions a UFG structure was formed with a mean grain/subgrain size of about 350 nm, as shown by the TEM images of the structure (Figure 3c). As shown in previous papers, the α-phase plates in the Ti-6Al-4V alloy transformed during the SPD processing at a relatively low temperature by means of the division of the plates by dislocation boundaries, their evolution leading to an increase in their misorientation due to the processes of dynamic recrystallization and spheroidization [29][30][31]. According to X-ray phase analysis, the volume fraction of the β-phase decreased from 15% to 10% due to a partial decomposition of the metastable β-phase during severe plastic deformation [32].…”

“…In the microstructure of the ECAP-processed Ti-6Al-4V alloy, the primary α-phase grains had a distorted shape (Figure 3a) and a weakly developed interior dislocation substructure (Figure 3b), but their size had not changed significantly and on average it was not above 8 µm. The interior regions of the primary α-phase can contain a cellular substructure or twins, depending on their crystallographic orientation with respect to the applied stress direction [29]. In the two-phase α + β regions a UFG structure was formed with a mean grain/subgrain size of about 350 nm, as shown by the TEM images of the structure (Figure 3c).…”

Advanced Materials for Mechanical Engineering: Ultrafine‐Grained Alloys with Multilayer Coatings

“…This approach was successfully used to produce large‐sized billets from the Ti–6Al–4V alloy with an SMC structure and UFG semiproducts by ECAP processing followed by rolling. [ 36,37 ] The relevant research showed that the features of the distribution of the α‐ and β‐phases, their shapes and their sizes, determine to a large extent the character of the structural transformations during ECAP processing and any subsequent deformational treatments. The evolution of the UFG structure during a subsequent shape‐forming deformation treatment is associated with various processes, including an additional fragmentation by slip and twinning, a recovery process, and polygonization, and by β‐phase decomposition.…”

“…In particular, experiments were conducted to examine the effect of ECAP processing on the character of microstructure refinement in the Ti–6Al–4V alloy during subsequent warm rolling via the “oval–square” arrangement at temperatures in the range of 450–650 °C. [ 37 ] It was established that, for the structure of the alloy in the as‐received condition, after rolling at 450 °C the globular α‐phase changes its shape primarily via multiple slip without any significant contribution from twinning, and this introduces a slight structural refinement. The fragmentation of the α‐phase grains is mainly accompanied by the formation of subgrain dislocation boundaries with low‐angle misorientations.…”