Mechanical Behavior of Ti-6Al-2Sn-4Zr-2Mo Titanium Alloy under Hot and Superplastic Forming Conditions: Experiment and Modeling

Yamane, Gen; Velay, Vincent; Vidal, Vanessa; Matsumoto, Hiroaki

doi:10.4028/www.scientific.net/ddf.385.413

Cited by 6 publications

(7 citation statements)

References 8 publications

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“…The testing conditions are summarized in Table 2. Additionally, tensile tests of the FG1 specimen were also conducted at 730, 750, and 920°C (open circles in Table 2) using a tensile specimen with a gauge length of 20 mm and width of 8 mm [19]. The strain rate sensitivity m was determined by evaluating the slope of log σ (at a true plastic strain of 0.1)-log ε˙curves or the strain rate change test.…”

Section: Evaluation Of High-temperature Deformation Behaviormentioning

confidence: 99%

“…4 summarizes the elongation to fracture of the UFG, FG, and Table 2 Tensile test conditions in this work (✔)and in other works (○) according to Ref. [19]. The strain rate ranges from 1 × 10 −4 to 1 × 10 −2 s −1 .…”

Section: Flow Behavior and Elongation To Fracturementioning

confidence: 99%

“…9(b), the results obtained at 730, 840, and 920°C using the same FG1 specimen according to Ref. [19] are also presented. Regardless of the testing temperature, the UFG1 and FG1 specimens exhibit similar grain size evolution.…”

Section: °Cmentioning

confidence: 99%

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Superplasticity of metastable ultrafine-grained Ti 6242S alloy: Mechanical flow behavior and microstructural evolution

Imai

Yamane

Matsumoto

et al. 2019

Materials Science and Engineering: A

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Keywords:Ti-6Ale2Sne4Zre2Mo-0.1Si alloy Superplasticity Ultrafine-grained microstructure Metastable microstructure Grain-boundary-sliding Accommodation mechanism A B S T R A C T Herein we quantitatively clarify the effects of grain size, β fraction, and morphology on the high-temperature deformation behavior of the Tie6Ale2Sne4Zre2Mo-0.1Si alloy. For this purpose, five materials were subjected to high-temperature tensile deformation: the UFG1 specimen (having an equiaxed morphology with d α = 0.78 μm and V β = 2.8%), the UFG2 specimen (having an equiaxed morphology with d α = 0.99 μm and V β = 24.2%), the FG1 specimen (having an equiaxed morphology with d α = 2.65 μm and V β = 11.2%), the FG2 specimen (having an equiaxed morphology with d α = 4.12 μm and V β = 11.0%), and the STQ specimen (with an acicular α′ martensite morphology). The UFG1 specimen is produced by hot-rolling of the STQ specimen having an acicular α′ martensite microstructure at 750°C. The UFG2 specimen is prepared by heat treatment of the UFG1 specimen at 400°C. The FG1 specimen is as-received Tie6242S alloy plate, and the FG2 specimen was prepared by heat treatment of the FG1 specimen at 900°C. The UFG specimens exhibited higher ductility associated with frequent activation of superplasticity than the FG specimens owing to the effect of decreasing grain size. The STQ specimen exhibited higher ductility at 700°C than the FG specimens. Quantitative analysis of the deformation mode according to internal-variable theory revealed much more grain boundary sliding in the UFG specimens. A comparison of the deformation behavior of the UFG1 and UFG2 specimens revealed excellent superplastic ductility in the UFG2 specimen at higher strain rates (10 −3 and 10 −2 s −1 ) and in the UFG1 specimen at lower strain rates (5 × 10 −4 and 10 −4 s −1 ). This behavior is ascribed mainly to different accommodation mechanisms during deformation of these specimens; dynamic β precipitation from supersaturated α microstructure occurred in the UFG1 specimen, whereas a decomposition process in which supersaturated β precipitates dissolve into the α phase was enhanced in the UFG2 specimen. In addition, the excess β precipitation observed in the UFG2 specimen led to enhanced α/β grain boundary sliding, resulting in further enhancement of the superplasticity. (H. Matsumoto). Fig. 13. Fraction of GMD and GBS relative to the overall deformation for the UFG1, UFG2, FG1, and FG2 specimens at (a), (b) 700°C, and (c), (d) 800°C and at strain rates of (a), (c) 10 −3 s −1 and (b), (d) 10 −4 s −1 .

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Section: Evaluation Of High-temperature Deformation Behaviormentioning

confidence: 99%

Section: Flow Behavior and Elongation To Fracturementioning

confidence: 99%

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Superplasticity of metastable ultrafine-grained Ti 6242S alloy: Mechanical flow behavior and microstructural evolution

Imai

Yamane

Matsumoto

et al. 2019

Materials Science and Engineering: A

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“…In this study, two temperature levels (T = 730 • C and T = 840 • C) below the usual industrial superplastic forming conditions (around 900 • C) are considered. The aim is to evaluate the deformation mechanisms of the material at low temperatures so as to avoid strain hardening occurring at and above 900 • C [4] and for several strain rate conditions from 10 −4 s −1 to 10 −2 s −1 . For both temperatures and each strain rate, test until failure are conducted as well as interrupted tensile tests, performed in the same conditions, to investigate both the mechanical behavior and the microstructural evolution induced for several elongations.…”

Section: Methodsmentioning

confidence: 99%

Experimental Analysis and Behaviour Modelling of the Deformation Mechanisms of a Ti-6242S Alloy under Hot and Superplastic Forming Conditions

Song

Anzu

Despax

et al. 2020

Metals

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In this work, the hot deformation characteristics of a near-α Ti-Al-2SnZr-2Mo alloy (Ti6242 alloy) with a Fine-Grained (FG) microstructure (dα = 2.86 μm) were investigated at two levels of temperature, T = 730 ∘C and T = 840 ∘C. The initial microstructure consists of equiaxed nodules of the α phase as well as some α lamellae sparsely distributed and separated by thin layers of the BCC β phase. For both temperatures, three strain rates (10−4,10−3,10−2s−1) were analysed during loading. Moreover, the microstructural evolution (α size and morphology) was also evaluated by conducting interrupted tensile tests. The different tensile testing conditions greatly influence the stress-strain response of the material as well as the microstructure evolution. Indeed, various phenomena can take place such as elongation of the grain structure, globularization, dynamic recrystallization and grain growth of the equiaxed areas depending on the temperature, the strain rate and the strain level. The FG Ti6242 alloy exhibits interesting superplastic ductility at T = 840 ∘C. At this temperature either a very gradual flow softening (at higher strain rate) or flow hardening (at lower strain rate) can be observed and are related respectively to one or more of the following mechanisms: lamellae globularization, DRX and grain growth. At the intermediate strain rate, both mechanisms, strain hardening and softening, coexist. At T = 730 ∘C, the onset of the α lamellae globularization was only promoted at low strain rate. A mechanical behavior model was developed in the temperature range of 730–840 ∘C, which was able to take into account all the observed phenomena: viscosity, softened behavior and strain hardening. Constitutive equations were calibrated from the stress-strain responses and microstructural observations, and the computed results were in good agreement with the experiments.

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“…However, determining how to manufacture complex thin-walled components made of high-temperature titanium alloys efficiently is difficult because of the high deformation resistance and severe springback at room temperature [ 8 ]. Complex thin-walled titanium alloys components were traditionally formed by superplastic forming [ 9 ]. However, both the high forming temperature and long forming time not only increased the cost greatly but also impaired the post-form properties [ 10 ], which limited its wide application.…”

Section: Introductionmentioning

confidence: 99%

Hot Gas Pressure Forming of Ti-55 High Temperature Titanium Alloy Tubular Component

et al. 2020

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In this paper, hot gas pressure forming (HGPF) of Ti-55 high temperature titanium alloy was studied. The hot deformation behavior was studied by uniaxial tensile tests at temperatures ranging from 750 to 900 °C with strain rates ranging from 0.001 to 0.05 s−1, and the microstructure evolution during tensile tests was characterized by electron backscatter diffraction. Finite element (FE) simulation of HGPF was carried out to study the effect of axial feeding on thickness distribution. Forming tests were performed to validate this process for Ti-55 alloy. Results show that when the temperature was higher than 750 °C, the elongation was large enough for HGPF of Ti-55 alloy. Dynamic recrystallization (DRX) occurred during the tensile deformation, which could refine the microstructure. The thickness uniformity of the formed part could be improved by increasing feeding length. The maximum thinning ratio decreased from 27.7% to 11.5% with the feeding length increasing from 0 to 20 mm. A qualified Ti-55 alloy component was successfully formed at 850 °C, the microstructure was slightly refined after forming, and the average post-form yield strength and peak strength were increased by 8.7% and 6.9%, respectively. Pre-heat treatment at 950 °C before HGPF could obtain Ti-55 alloy tubular component with bimodal microstructure and further improve the post-form strength.

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Mechanical Behavior of Ti-6Al-2Sn-4Zr-2Mo Titanium Alloy under Hot and Superplastic Forming Conditions: Experiment and Modeling

Cited by 6 publications

References 8 publications

Superplasticity of metastable ultrafine-grained Ti 6242S alloy: Mechanical flow behavior and microstructural evolution

Superplasticity of metastable ultrafine-grained Ti 6242S alloy: Mechanical flow behavior and microstructural evolution

Experimental Analysis and Behaviour Modelling of the Deformation Mechanisms of a Ti-6242S Alloy under Hot and Superplastic Forming Conditions

Hot Gas Pressure Forming of Ti-55 High Temperature Titanium Alloy Tubular Component

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