Annealing behavior of severely-deformed titanium Grade 4

G. S. Dyakonov, S. Mironov, N. Enikeev, R. Z. Valiev, S. L. Semiatin

Результат исследований: Научные публикации в периодических изданияхстатьянаучнаярецензирование

1 цитирование (Scopus)

Выдержка

The static-annealing behavior and evolution of the microstructure-strength relationship of severely-deformed commercial-purity titanium Grade 4 over the temperature range of 50–850 °C (0.16–0.57 Tm, where Tm is the melting point) were established. The severely-deformed material was obtained via equal-channel angular pressing (ECAP) using the Conform (ECAP-C) technique at 200 °C to an effective accumulated true strain of 8.4. The resulting ultrafine structure was stable to 400 °C. The excellent thermal stability was concluded to be associated with a strain-aging effect, i.e., the enhanced diffusion of solutes within this temperature interval resulting in the formation of solute atmospheres at/near dislocations. At 450–500 °C, rapid growth of strain-free grains occurred, which eliminated the severely-deformed microstructure and promoted softening. This process was deduced to be controlled primarily by grain-boundary energy and therefore was interpreted primarily in terms of grain growth rather than discontinuous recrystallization expected in this temperature range. A further increase in annealing temperature to 600 °C led to normal grain growth. Analysis of the microstructure-strength relationship suggested a significant influence of mechanical twinning on yield strength of the fully-annealed material. At 600 °C and higher temperatures, dissolution of constituent iron-rich particles was observed. This promoted a partial α → β transformation at the temperatures noticeably below the typical beta-transus of pure titanium (~880 °C). This phenomenon resulted in the precipitation of nanoscale β particles which imparted substantial strengthening. Water quenching of the material annealed at 850 °C gave rise to a β → α′ martensitic transformation. The latter process was governed by exceptionally strong variant selection and thereby provided a nearly-ideal restoration of crystallographic orientations of parent α-grains.

Язык оригиналаанглийский
Страницы (с-по)89-101
Число страниц13
ЖурналMaterials Science and Engineering A
Том742
DOI
СостояниеОпубликовано - 10 янв 2019

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  • Материаловедение (все)
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  • Общее машиностроение

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Dyakonov, G. S. ; Mironov, S. ; Enikeev, N. ; Valiev, R. Z. ; Semiatin, S. L. / Annealing behavior of severely-deformed titanium Grade 4. В: Materials Science and Engineering A. 2019 ; Том 742. стр. 89-101.
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Annealing behavior of severely-deformed titanium Grade 4. / Dyakonov, G. S.; Mironov, S.; Enikeev, N.; Valiev, R. Z.; Semiatin, S. L.

В: Materials Science and Engineering A, Том 742, 10.01.2019, стр. 89-101.

Результат исследований: Научные публикации в периодических изданияхстатьянаучнаярецензирование

TY - JOUR

T1 - Annealing behavior of severely-deformed titanium Grade 4

AU - Dyakonov, G. S.

AU - Mironov, S.

AU - Enikeev, N.

AU - Valiev, R. Z.

AU - Semiatin, S. L.

PY - 2019/1/10

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N2 - The static-annealing behavior and evolution of the microstructure-strength relationship of severely-deformed commercial-purity titanium Grade 4 over the temperature range of 50–850 °C (0.16–0.57 Tm, where Tm is the melting point) were established. The severely-deformed material was obtained via equal-channel angular pressing (ECAP) using the Conform (ECAP-C) technique at 200 °C to an effective accumulated true strain of 8.4. The resulting ultrafine structure was stable to 400 °C. The excellent thermal stability was concluded to be associated with a strain-aging effect, i.e., the enhanced diffusion of solutes within this temperature interval resulting in the formation of solute atmospheres at/near dislocations. At 450–500 °C, rapid growth of strain-free grains occurred, which eliminated the severely-deformed microstructure and promoted softening. This process was deduced to be controlled primarily by grain-boundary energy and therefore was interpreted primarily in terms of grain growth rather than discontinuous recrystallization expected in this temperature range. A further increase in annealing temperature to 600 °C led to normal grain growth. Analysis of the microstructure-strength relationship suggested a significant influence of mechanical twinning on yield strength of the fully-annealed material. At 600 °C and higher temperatures, dissolution of constituent iron-rich particles was observed. This promoted a partial α → β transformation at the temperatures noticeably below the typical beta-transus of pure titanium (~880 °C). This phenomenon resulted in the precipitation of nanoscale β particles which imparted substantial strengthening. Water quenching of the material annealed at 850 °C gave rise to a β → α′ martensitic transformation. The latter process was governed by exceptionally strong variant selection and thereby provided a nearly-ideal restoration of crystallographic orientations of parent α-grains.

AB - The static-annealing behavior and evolution of the microstructure-strength relationship of severely-deformed commercial-purity titanium Grade 4 over the temperature range of 50–850 °C (0.16–0.57 Tm, where Tm is the melting point) were established. The severely-deformed material was obtained via equal-channel angular pressing (ECAP) using the Conform (ECAP-C) technique at 200 °C to an effective accumulated true strain of 8.4. The resulting ultrafine structure was stable to 400 °C. The excellent thermal stability was concluded to be associated with a strain-aging effect, i.e., the enhanced diffusion of solutes within this temperature interval resulting in the formation of solute atmospheres at/near dislocations. At 450–500 °C, rapid growth of strain-free grains occurred, which eliminated the severely-deformed microstructure and promoted softening. This process was deduced to be controlled primarily by grain-boundary energy and therefore was interpreted primarily in terms of grain growth rather than discontinuous recrystallization expected in this temperature range. A further increase in annealing temperature to 600 °C led to normal grain growth. Analysis of the microstructure-strength relationship suggested a significant influence of mechanical twinning on yield strength of the fully-annealed material. At 600 °C and higher temperatures, dissolution of constituent iron-rich particles was observed. This promoted a partial α → β transformation at the temperatures noticeably below the typical beta-transus of pure titanium (~880 °C). This phenomenon resulted in the precipitation of nanoscale β particles which imparted substantial strengthening. Water quenching of the material annealed at 850 °C gave rise to a β → α′ martensitic transformation. The latter process was governed by exceptionally strong variant selection and thereby provided a nearly-ideal restoration of crystallographic orientations of parent α-grains.

KW - Characterization

KW - Grains and interfaces

KW - Phase transformation

KW - Plasticity methods

KW - Titanium alloys

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JO - Materials Science & Engineering A: Structural Materials: Properties, Microstructure and Processing

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SN - 0921-5093

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