Effect of commercial purity levels on the mechanical properties of ultrafine-grained titanium

authored by: G. Purcek, G. G. Yapici, I. Karaman, H. J. Maier
Abstract: Two grades of commercial purity (CP) titanium (grades 2 and 4) were processed using equal-channel angular extrusion (ECAE) at 300°C and 450°C, respectively. The processing temperatures were the minimum temperatures at which eight pass ECAE could be performed without any shear-localization. The coarse-grained (CG) microstructures of as-received grade-2 and grade-4 CP-Ti, with average grain sizes of 110μm and 70μm, respectively, were refined down to sub-micron levels with a mean grain size of about 300nm for both grades after 8 ECAE passes. The ultrafine-grained (UFG) microstructures led to substantial enhancement in strength for both grades. The grade-2 sample showed a more than two fold increase in yield strength (σ_y), from 307MPa for the as-received one to about 620MPa for the processed samples. The grade-4 CP-Ti exhibited a relatively smaller increase in strength due to the higher processing temperature, and it showed about 50% increase in σ_y after eight pass ECAE, from 531 to 758MPa. These strength levels were obtained with high ductility levels of 21% and 25% for UFG grade-2 and grade-4 Ti, respectively. These improvements in mechanical properties are attributed to the substantially refined grain size and increased dislocation density. Grade-4 Ti is stronger than grade-2 because of the higher oxygen content. The higher ductility and significantly higher strain hardening capability of UFG grade-4 Ti, in spite of the similar grain size and microstructure with UFG grade-2 Ti, is also due to the higher impurity content, probably resulting in a higher dislocation storage capability during room temperature deformation, and thus, higher strain hardening capacity. Such properties make UFG grade-4 Ti comparable to the commercial Ti-6Al-4V alloy for biomedical applications without negative effects of the alloying elements on biocompatibility.
External Organisation(s): Karadeniz Technical University
Texas A and M University
Ozyegin University
Paderborn University
Type: Article
Journal: Materials Science and Engineering A
Volume: 528
Pages: 2303-2308
No. of pages: 6
ISSN: 0921-5093
Publication date: 13.11.2010
Publication status: Published
Peer reviewed: Yes
ASJC Scopus subject areas: General Materials Science, Condensed Matter Physics, Mechanics of Materials, Mechanical Engineering
Electronic version(s): https://doi.org/10.1016/j.msea.2010.11.021 (Access: Unknown)

BibTeX

@article{0a243487eb774d7fbf3ac66601d3a372,
title = "Effect of commercial purity levels on the mechanical properties of ultrafine-grained titanium",
abstract = "Two grades of commercial purity (CP) titanium (grades 2 and 4) were processed using equal-channel angular extrusion (ECAE) at 300°C and 450°C, respectively. The processing temperatures were the minimum temperatures at which eight pass ECAE could be performed without any shear-localization. The coarse-grained (CG) microstructures of as-received grade-2 and grade-4 CP-Ti, with average grain sizes of 110μm and 70μm, respectively, were refined down to sub-micron levels with a mean grain size of about 300nm for both grades after 8 ECAE passes. The ultrafine-grained (UFG) microstructures led to substantial enhancement in strength for both grades. The grade-2 sample showed a more than two fold increase in yield strength (σy), from 307MPa for the as-received one to about 620MPa for the processed samples. The grade-4 CP-Ti exhibited a relatively smaller increase in strength due to the higher processing temperature, and it showed about 50% increase in σy after eight pass ECAE, from 531 to 758MPa. These strength levels were obtained with high ductility levels of 21% and 25% for UFG grade-2 and grade-4 Ti, respectively. These improvements in mechanical properties are attributed to the substantially refined grain size and increased dislocation density. Grade-4 Ti is stronger than grade-2 because of the higher oxygen content. The higher ductility and significantly higher strain hardening capability of UFG grade-4 Ti, in spite of the similar grain size and microstructure with UFG grade-2 Ti, is also due to the higher impurity content, probably resulting in a higher dislocation storage capability during room temperature deformation, and thus, higher strain hardening capacity. Such properties make UFG grade-4 Ti comparable to the commercial Ti-6Al-4V alloy for biomedical applications without negative effects of the alloying elements on biocompatibility.",
keywords = "Equal-channel angular extrusion/pressing, Grade-2 and grade-4 CP-Ti, Mechanical properties, Microstructure, Ultrafine-grained materials",
author = "G. Purcek and Yapici, {G. G.} and I. Karaman and Maier, {H. J.}",
note = "Funding information: This work was mainly supported by the National Science Foundation – International Materials Institute Program through the grant no. DMR 08-44082 , Office of Specific Programs, Division of Materials Research, Arlington, Virginia. GP would like to acknowledge the support from the Scientific Research Projects of Karadeniz Technical University, Turkey and TUBITAK, Turkey , under 2219-International Postdoctoral Research Scholar Program.",
year = "2010",
month = nov,
day = "13",
doi = "10.1016/j.msea.2010.11.021",
language = "English",
volume = "528",
pages = "2303--2308",
journal = "Materials Science and Engineering A",
issn = "0921-5093",
publisher = "Elsevier BV",
number = "6",
}