Deformation mechanisms in commercial Ti (0.5 at. pct oineq) at intermediate and high temperatures (0.3 - 0.6 tinm)

Döner, M.; Conrad, H.

doi:10.1007/bf02644581

Cited by 101 publications

(40 citation statements)

References 32 publications

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“…200±300, 500±650, and 700±900 K, have been found within which dynamic strain aging took place, each at its own activation energy, i.e. 42, 130, and 210 kJ/mol [8,29]. These are associated with hydrogen, carbon, and oxygen diusion, respectively, as reported by Doner and Conrad [8].…”

Section: Dynamic Strain Agingmentioning

confidence: 60%

“…42, 130, and 210 kJ/mol [8,29]. These are associated with hydrogen, carbon, and oxygen diusion, respectively, as reported by Doner and Conrad [8]. However, the activation energy of 130 kJ/mol for the intermediate dynamic strain-aging range is lower than that of 182 kJ/mol for carbon diusion, but is closer to that of iron.…”

Section: Dynamic Strain Agingmentioning

confidence: 69%

“…Dynamic strain aging often occurred in the temperature range of 600±850 K and strain rates of 3 Â 10 À5 ±3 Â 10 À2 as. As noted by Doner and Conrad [8], mechanisms that have been proposed for dynamic strain aging are based either on the impurity-drag model or on the impurity-pinning model. Garde and co-workers [9,10] state that deformation twinning occurs signi®cantly, and is important in the low temperature deformation of various grades of titanium of dierent longitudinal textures (basal plane parallel to the stress axis) over a range of grain sizes.…”

Section: Introductionmentioning

confidence: 99%

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Mechanical properties and deformation mechanisms of a commercially pure titanium

1999

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AbstractÐThe mechanical behavior of a commercially pure titanium (CP-Ti) is systematically investigated in quasi-static (Instron, servohydraulic) and dynamic (UCSD's recovery Hopkinson) compression. Strains over 40% are achieved in these tests over a temperature range of 77±1000 K and strain rates of 10 À3 ±8000/s. At the macroscopic level, the¯ow stress of CP-Ti, within the plastic deformation regime, is strongly dependent on the temperature and strain rate, and displays complex variations with strain, strain rate, and temperature. In particular, there is a three-stage deformation pattern at a temperature range from 296 to 800 K, the speci®c range depending on the strain rate. In an e ort to understand the underlying mechanisms, a number of interrupted tests involving temperature jumps are performed, and the resulting microstructures are characterized using an optical microscope. Based on the experimental results and simple estimates, it is concluded that the three-stage pattern of deformation at temperatures from 296 to 800 K, is a result of dynamic strain aging, through the directional di usion of dislocation-core point defects with the moving dislocation at high strain rates, although the usual dynamic strain aging by point defects segregating outside the dislocation core through volume di usion is also observed at low strain rates and high temperatures. The microscopic analysis shows that there is substantial deformation twinning which cannot be neglected in modeling the plastic¯ow of CP-Ti. The density of twins increases markedly with increasing strain rate, strain, and decreasing temperature. Twin intersections occur, and become more pronounced at low temperatures or high strain rates. In sum, the true stress±true strain curves of CP-Ti show two stages of deformation pattern at low temperatures, three stages at temperatures above 296 K, and only one stage at temperatures exceeding 800 K, although all three stages may exist even at 1000 K for very high strain rates, e.g. 8000/s. While the dislocation motion is still the main deformation mechanism for plastic¯ow, the experimental results suggest that dynamic strain aging should be taken into account, as well as the e ect of deformation twinning. #

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Section: Dynamic Strain Agingmentioning

confidence: 60%

Section: Dynamic Strain Agingmentioning

confidence: 69%

Section: Introductionmentioning

confidence: 99%

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Mechanical properties and deformation mechanisms of a commercially pure titanium

1999

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“…[29] In the case of higher activation energies, the rate-controlling process at higher temperatures was assumed to be diffusion controlled because the activation energy for the high-temperature creep was similar to that of self-diffusion in a-Ti (e.g., 242 kJ/mol). [26] Therefore, we concluded that deformation in the a phase is dominant in near-a Ti alloys with a small volume fraction of b phase, even though the activation energy in a-Ti is affected by solute diffusion. [36] The activation energies obtained in this study are greater than that for self-diffusion in a-Ti and are similar to the values reported for conventional alloys such as Ti-6242S and IMI 834, [27,32,33] even though the effects of Si solid solution and silicide precipitation were not factors in this study.…”

Section: Resultsmentioning

confidence: 79%

“…The a phase composition affects the creep process, which is regarded as a thermally activated process that includes dislocation climb, where the mobility of a solute atom in alloyed a-Ti can vary with the solute atom's effective size. [7,18,26] The tensile strength at 923 K (650°C) suggests that the a phase in the Ga-added alloy may lead to a higher creep strength than that in the Sn-added alloy. However, the creep behavior was strongly dependent on the microstructure morphology in this study, as shown in the creep curves collected at 873 K (600°C) and 923 K (650°C) under a constant stress of 310 MPa (Figure 2).…”

Section: Resultsmentioning

confidence: 99%

Effects of Ga and Sn Additions on the Creep Strength and Oxidation Resistance of Near-α Ti Alloys

Kitashima

Yamabe‐Mitarai

Iwasaki

et al. 2016

Metall Mater Trans A

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The effects of Ga and Sn additions, with an almost constant value regarding Al equivalence, on the creep properties and oxidation resistance of the near-a Ti alloy Ti-5Al-4Zr-1Mo were investigated. The creep strain rate increased due to the replacement of Sn with Ga, which was accompanied by an increase in the volume fraction of primary equiaxed a phase. In addition, the replacement of Sn with Ga decreased the activation energy of the steady-state creep rate for the similar volume fraction of the equiaxed a phase. Ga addition improved the oxidation resistance without Ga segregation at the TiO 2 /substrate interface, whereas Sn promoted oxide spallation with metallic Sn segregation at the interface. Ga uniformly dissolved into the internal TiO 2 and into the external Al 2 O 3 as a result of solid solution formation between Ga 2 O 3 and the aforementioned oxides, which suppressed oxide growth. The formation of (GaAl) 2 TiO 5 in TiO 2 and Al 2 O 3 was also discussed on the basis of the phase relationships in the TiO 2 -Al 2 O 3 -Ga 2 O 3 system.

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Application to HCP Metals and Alloys

2014

Fundamentals of Strength

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Section 3.3 summarized several unique characteristics of slip in hexagonal close-packed (HCP) metals. In particular, the close-packed system-the basal plane (0001) and the close-packed direction < > 1120 -has only three independent systems compared with the 12 available in the face-centered cubic (FCC) crystal structure. Therefore, slip is observed on other crystal planes. The prismatic plane was referred to in Section 3.3. In the Miller-Bravais coordinate system, this is the ( ) 1010 plane and the close-packed direction < > 1120 . Slip is also observed on the pyramidal system, which is ( ) 1011 plane and, once again, the close-packed direction < > 1120 . The ease of slip in HCP metals as influenced by the dislocation energy and the spacing between parallel slip planes (as discussed in Section 3.2 in regard to the Peierls stress) is affected by the active slip system(s). One implication of this is that one should expect less commonality between in deformation kinetics in HCP metals than observed in FCC and body-centered cubic (BCC) metals.In this chapter, the temperature dependence and, in some cases, the strainrate dependence of deformation in pure Cd, Ti, Zn, and Zr and in Mg, Zr, and Ti alloys is examined. The analysis presented in these HCP metals is complicated by (1) the limited availability of extensive experimental campaigns available for model FCC and BCC systems, (2) contributions of deformation twinning observed in most of the HCP systems-particularly at low (homolo-Fundamentals of Strength: Principles, Experiment, and Applications of an Internal State Variable Constitutive Formulation, First Edition. Paul S. Follansbee.

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Deformation mechanisms in commercial Ti (0.5 at. pct oineq) at intermediate and high temperatures (0.3 - 0.6 tinm)

Cited by 101 publications

References 32 publications

Mechanical properties and deformation mechanisms of a commercially pure titanium

Mechanical properties and deformation mechanisms of a commercially pure titanium

Effects of Ga and Sn Additions on the Creep Strength and Oxidation Resistance of Near-α Ti Alloys

Application to HCP Metals and Alloys

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