Grain-structure refinement in titanium alloy under different loading schedules

Effect of strain reversal on the dynamic spheroidization of Ti-6Al-4V during hot deformation

“…The present strain-path results can be compared with previous observations by Korshunov et al, [7] who investigated the effect of strain reversal on dynamic spheroidization kinetics in alloy VT9 (Ti-6.6Al-3.5Mo-1.7Zr-0.27Si, in wt pct) (Figure 13). These former tests were conducted at a deformation temperature of 960°C and strain rate of 0.001 s Ϫ1 .…”

“…These can affect flow behavior, texture, and microstructure development in a number of materials. For example, the effects of deformation mode and strain path on the dynamic spheroidization kinetics of the titanium-based VT9 alloy were studied by Korshunov et al [7] This work showed that different monotonic deformation modes, such as tension or torsion, result in similar spheroidization kinetics, but that large strain-path changes, such as that in reversed torsion testing, retard the spheroidization kinetics compared with monotonic deformation. These results are similar to those seen in work examining the effect of strain-path reversal on the dynamic recrystallization kinetics of stainless steel, [12] microalloyed steel, [13] and lead.…”

“…13-Comparison of dynamic spheroidization kinetics of alloy VT9 deformed at 960°C, 0.001 s Ϫ1 via uniaxial tension, torsion, or reversed torsion. [7] radial line across the sample would lead to an error in the strain of ϳ0.06 (in a sample deformed to a total strain of 2). Such an error would be especially important for strains in the range between 1 and 1.5 (for monotonic deformation), because the rate of increase in the percent spheroidized with increasing strain is high in this region.…”

“…[2] Due to the importance of spheroidization during the industrial processing of ␣ ϩ ␤ titanium alloys, considerable work has been performed to investigate the kinetics and mechanisms of spheroidization. Dynamic spheroidization has been studied by several authors, including Seshacharyulu et al, [3] Semiatin and co-workers, [4,5,6] and Korshunov et al [7] For example, the work of Semiatin et al [5] quantified the effect of deformation temperature on the dynamic spheroidization kinetics of Ti-6-4 at three strain rates. For a material with a prior-␤ grain size of 100 m, they showed that the kinetics exhibit little dependence on temperature at a low strain rate (0.001 s Ϫ1 ), but the rate of spheroidization decreases somewhat with increasing temperature at higher strain rates.…”

Cavitation and failure during hot forging of Ti-6Al-4V

“…A number of researchmodels for the initiation and growth of cavities therefore ers have examined the mechanisms of dynamic recrystalliis very important. zation of single-phase alloys, dynamic globularization of Raj, [13] Matsumoto et al, [l4] and Suzuki and Eylon [15] lamellar microstructures, etc., [3,4,5] as well as the phenomemade attempts to define strain rate/temperature regimes nology of such processes (e.g., recrystallization/globularizain which cavitation is most severe in alpha/beta titanium tion kinetics [6,7,8] ). However, only relatively little effort alloys with transformed beta microstructures through meahas been expended to inter-relate mechanistic and phenomsurements of reduction in area or gross fracture appearance enological knowledge.…”