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Title: Creep study of mechanisms involved in low-temperature superplasticity of UFG Ti-6Al-4V processed by SPD

Abstract

The deformation kinetics of ultrafine-grained Ti-6Al-4V with mean (sub)grain size about 150 nm (produced by isothermal multiaxial forging) and superplastic properties at the relatively low temperature of 873 K was investigated in compression and tension over a large range of strain rates from 10{sup −7} to 10{sup −2} s{sup −1}. Electron microscopic observations showed that the grains coarsen during deformation towards the quasi-stationary spacing w{sub qs} of strain induced boundaries. In spite of the grain coarsening the grains were generally smaller than w{sub qs} allowing high-angle boundaries to dominate the quasi-stationary strength. Texture measurements indicate that dislocation glide plays a large role in deformation. Glide in this alloy is significantly influenced by solid solution strengthening leading to a stress sensitivity of strain rate of n = 3. The present ultrafine-grained Ti alloy displays a stress sensitivity exponent n = 2 over an extended stress range where its superplastic behavior is optimal. While the deformation kinetics of present ultrafine-grained Ti alloy can be roughly explained by the traditional formula for superplastic flow, the significant discrepancy to the measured values suggests that solid solution strengthening must be taken into account to get a complete insight. - Highlights: • The UFG Ti-6Al-4V alloymore » behaves superplastically at low temperature of 873 K. • Grain coarsening at low stresses limits superplasticity of UFG Ti alloy. • Solute strengthening plays an important role in low-temperature superplasticity. • Acceleration of creep in UFG Ti alloy is caused by processes related to hab.« less

Authors:
 [1];  [2];  [1];  [2];  [3]; ; ;  [4]; ;  [1];  [2]
  1. Institute of Physics of Materials, ASCR, Zizkova 22, CZ -61662 Brno (Czech Republic)
  2. (Czech Republic)
  3. Inst. f. Werkstoffwissenschaften, University of Erlangen-Nürnberg, D-91058 Erlangen (Germany)
  4. Belgorod State University, Laboratory of Bulk Nanostructured Materials, Pobeda Str. 85, 308015 Belgorod (Russian Federation)
Publication Date:
OSTI Identifier:
22587159
Resource Type:
Journal Article
Resource Relation:
Journal Name: Materials Characterization; Journal Volume: 116; Other Information: Copyright (c) 2016 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 77 NANOSCIENCE AND NANOTECHNOLOGY; CREEP; DISLOCATIONS; GRAIN SIZE; NANOSTRUCTURES; PLASTICITY; SENSITIVITY; SOLID SOLUTIONS; SOLIDS; STRAIN RATE; STRAINS; STRESSES; TEMPERATURE RANGE 0400-1000 K; TITANIUM ALLOYS

Citation Formats

Kral, Petr, E-mail: pkral@ipm.cz, CEITEC – IPM ASCR, v.v.i., Zizkova 22, CZ-61662 Brno, Dvorak, Jiri, CEITEC – IPM ASCR, v.v.i., Zizkova 22, CZ-61662 Brno, Blum, Wolfgang, Kudryavtsev, Egor, Zherebtsov, Sergey, Salishchev, Gennady, Kvapilova, Marie, Sklenicka, Vaclav, and CEITEC – IPM ASCR, v.v.i., Zizkova 22, CZ-61662 Brno. Creep study of mechanisms involved in low-temperature superplasticity of UFG Ti-6Al-4V processed by SPD. United States: N. p., 2016. Web. doi:10.1016/J.MATCHAR.2016.04.007.
Kral, Petr, E-mail: pkral@ipm.cz, CEITEC – IPM ASCR, v.v.i., Zizkova 22, CZ-61662 Brno, Dvorak, Jiri, CEITEC – IPM ASCR, v.v.i., Zizkova 22, CZ-61662 Brno, Blum, Wolfgang, Kudryavtsev, Egor, Zherebtsov, Sergey, Salishchev, Gennady, Kvapilova, Marie, Sklenicka, Vaclav, & CEITEC – IPM ASCR, v.v.i., Zizkova 22, CZ-61662 Brno. Creep study of mechanisms involved in low-temperature superplasticity of UFG Ti-6Al-4V processed by SPD. United States. doi:10.1016/J.MATCHAR.2016.04.007.
Kral, Petr, E-mail: pkral@ipm.cz, CEITEC – IPM ASCR, v.v.i., Zizkova 22, CZ-61662 Brno, Dvorak, Jiri, CEITEC – IPM ASCR, v.v.i., Zizkova 22, CZ-61662 Brno, Blum, Wolfgang, Kudryavtsev, Egor, Zherebtsov, Sergey, Salishchev, Gennady, Kvapilova, Marie, Sklenicka, Vaclav, and CEITEC – IPM ASCR, v.v.i., Zizkova 22, CZ-61662 Brno. 2016. "Creep study of mechanisms involved in low-temperature superplasticity of UFG Ti-6Al-4V processed by SPD". United States. doi:10.1016/J.MATCHAR.2016.04.007.
@article{osti_22587159,
title = {Creep study of mechanisms involved in low-temperature superplasticity of UFG Ti-6Al-4V processed by SPD},
author = {Kral, Petr, E-mail: pkral@ipm.cz and CEITEC – IPM ASCR, v.v.i., Zizkova 22, CZ-61662 Brno and Dvorak, Jiri and CEITEC – IPM ASCR, v.v.i., Zizkova 22, CZ-61662 Brno and Blum, Wolfgang and Kudryavtsev, Egor and Zherebtsov, Sergey and Salishchev, Gennady and Kvapilova, Marie and Sklenicka, Vaclav and CEITEC – IPM ASCR, v.v.i., Zizkova 22, CZ-61662 Brno},
abstractNote = {The deformation kinetics of ultrafine-grained Ti-6Al-4V with mean (sub)grain size about 150 nm (produced by isothermal multiaxial forging) and superplastic properties at the relatively low temperature of 873 K was investigated in compression and tension over a large range of strain rates from 10{sup −7} to 10{sup −2} s{sup −1}. Electron microscopic observations showed that the grains coarsen during deformation towards the quasi-stationary spacing w{sub qs} of strain induced boundaries. In spite of the grain coarsening the grains were generally smaller than w{sub qs} allowing high-angle boundaries to dominate the quasi-stationary strength. Texture measurements indicate that dislocation glide plays a large role in deformation. Glide in this alloy is significantly influenced by solid solution strengthening leading to a stress sensitivity of strain rate of n = 3. The present ultrafine-grained Ti alloy displays a stress sensitivity exponent n = 2 over an extended stress range where its superplastic behavior is optimal. While the deformation kinetics of present ultrafine-grained Ti alloy can be roughly explained by the traditional formula for superplastic flow, the significant discrepancy to the measured values suggests that solid solution strengthening must be taken into account to get a complete insight. - Highlights: • The UFG Ti-6Al-4V alloy behaves superplastically at low temperature of 873 K. • Grain coarsening at low stresses limits superplasticity of UFG Ti alloy. • Solute strengthening plays an important role in low-temperature superplasticity. • Acceleration of creep in UFG Ti alloy is caused by processes related to hab.},
doi = {10.1016/J.MATCHAR.2016.04.007},
journal = {Materials Characterization},
number = ,
volume = 116,
place = {United States},
year = 2016,
month = 6
}
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