Deformation kinetics of coarse-grained and ultrafine-grained commercially pure Ti

Blum, W.; Li, Yujiao; Breutinger, F.

doi:10.1016/j.msea.2006.05.171

Cited by 22 publications

(15 citation statements)

References 9 publications

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“…Table II shows that the activation energies for interstitial bulk diffusion, even for the fastest hydrogen atoms, are significantly larger than the activation energy presently found for the low-temperature DSA in UFG Ti (17.3 kJ/mol). This discrepancy is reported here for the first time, since other works of DSA in UFG Ti [42,44] did not indicate activation energies.…”

Section: Activation Energy For Dynamic Strain Agingcontrasting

confidence: 84%

“…Moreover, they report an abnormal strain hardening behavior at large strains and dynamic strain rates. Contrary to Blum and Breutinger, [42] Wang et al [43] concluded that such behavior might be associated with twinning instead of DSA, despite little evidence of twinning activity reported at quasi-static strain rates except at very large strains.…”

Section: Introductionmentioning

confidence: 91%

“…[13,18,22] In recent years, investigations on the mechanical behavior of ultrafine-grained titanium (UFG Ti) processed by severe plastic deformation (SPD) have received considerable attention due to its potential applications, primarily in the biomedical field. However, these studies have either ignored [27][28][29][30][31][32][33][34][35][36][37][38][39][40][41] or merely superficially discussed [42][43][44] the possible occurrence of DSA. Serrations in stress-strain curves were never analyzed in the UFG Ti processed by equal channel angular pressing (ECAP) [27,28,[31][32][33]35,36,[38][39][40][41] or equal channel angular extrusion (ECAE), [34,37] even though they were observed.…”

Section: Introductionmentioning

confidence: 99%

“…Blum and Breutinger [42] investigated the deformation kinetics of ECAPed UFG Ti and attributed a work softening at 723 K (450°C) to DSA. Wang et al [43] also discussed the possibility of DSA in ECAPed UFG Ti compressed at RT at quasi-static (10 À4 to 10 À1 s À1) and dynamic (10 3 to 10 4 s À1 ) strain rates.…”

Section: Introductionmentioning

confidence: 99%

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Room Temperature Dynamic Strain Aging in Ultrafine-Grained Titanium

Lopes

Zhao

et al. 2015

Metall Mater Trans A

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Dynamic strain aging (DSA) in coarse-grained (CG) titanium is usually observed at intermediate to high temperatures 473 K to 973 K (200°C to 700°C) and is characterized by serrations in the stress vs strain curves. In the present work, despite the absence of apparent serrations, ultrafine-grained titanium (UFG Ti) undergoes DSA at room temperature, exhibited through an abnormal increase in the elastic limit and negative strain rate sensitivity. This effect is observed at 293 K (20°C) in the strain rate interval of 10 À4 to 10 À2 s À1 , and at 203 K (À70°C) and 373 K (100°C) in a distinct strain rate range. Based on a calculated activation energy of 17.3 kJ/mol and microstructural observations by transmission electron microscopy, it is proposed that the dominant mechanism for DSA in UFG Ti involves interstitial solutes interacting with dislocations emitted from grain boundaries. The interstitials migrate from the grain boundaries along dislocation lines bowing out as they are emitted from the boundaries, a mechanism with a low calculated activation energy which is comparable with the experimental measurements. The dislocation velocities and interstitial diffusion along the dislocation cores are consistent.

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Section: Activation Energy For Dynamic Strain Agingcontrasting

confidence: 84%

Section: Introductionmentioning

confidence: 91%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Room Temperature Dynamic Strain Aging in Ultrafine-Grained Titanium

Lopes

Zhao

et al. 2015

Metall Mater Trans A

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“…The load required for the sample entirely depends on the strength of the material and the effect of of dislocations and no strain hardening. In addition, another mechanism has been suggested based on the breakaway of dislocations from solute clouds 52 . In the initial state, it is very difficult to break the dislocations from solute atoms in the case of ultra fine grained titanium as compared to that of coarse grained.…”

Section: Suitability For Large Scale Productionmentioning

confidence: 99%

ECAP of commercially pure titanium: A review

Ravisankar

Park

2008

Trans Indian Inst Met

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REVIEWECAP has emerged as an attractive technique in last two decades and is gaining as a potential route for industrial production. Though it is a well known the technique, for the sake of completeness a brief introduction about ECAP process is given.In the ECAP process a well lubricated billet is pressed in a die that contains two channels, equal in cross section, intersecting at an angle called die channel angle. The material is subjected to shear deformation at the intersection plane. Since the process is capable of maintaining the net dimensions of the work piece, repetitive extrusion is possible, provided that the material has sufficient ductility, to withstand heavy deformations. The multiple ECAP passes make it possible to rotate the billet around its longitudinal axis between the passes, creating different routes.Conventionally ECAP has been classified into four routes based on the rotation of billet between each passes with reference to its longitudinal axis as (i) Route A, no rotation (ii) Route B A , rotating 90 0 in opposite directions, (iii) Route B c , rotating 90 0 in the same direction and (iv) Route C, rotating 180 0 . Figure 1 schematically illustrates the four processing routes of ECAP.The shear planes in extrusion axis (X direction), Perpendicular axes (Y and Z direction) tend to rotate based on the channel angle and processing route and hence the properties tend to change accordingly. The shearing plane on the three directions and in four routes is schematically given in Fig. 2.Usually, the billets are rotated with reference to X axis only. The rotation of the samples in X plane is more effective as compared to Y and Z axis based on the shearing patterns which can be understood from Fig. 2. ABSTRACTEqual Channel Angular Extrusion (ECAE) also called as Equal Channel Angular Pressing (ECAP) is an emerging mechanical or thermo mechanical method for synthesis of bulk ultra fine grained or nano materials. The uniqueness of ECAP is that the fine grains are obtained without changing any of the dimensions of the sample. The grain refinement increases the strength of CP-Ti to the strength levels of Ti-6Al-4V, a commonly used material for bio implants. Though Ti-6Al-4V alloys satisfy the biomedical requirements, the Al and V are toxic to human tissue. ECAP is an attracting technique for strengthening commercially pure titanium (CP-Ti) to a level of Ti-6Al-4V since CP-Ti has better compatibility for bio medical applications. Hence, the research is focused on ECAP of CPTi. This overview mainly focuses on the mechanical properties, corrosion resistance, wear resistance, fatigue resistance and the influence of external and internal parameters on the properties of ECAPed CP-Ti. It also highlights the methods employed for increasing the deformability of CP-Ti. Finally, the suitability of ECAP for industrial production is also discussed. The state of the art in this field is encouraging and showing positive signs of commercializing ECAP of CP-Ti in the near future.

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