Dynamic deformation and failure of ultrafine-grained titanium
Dynamic deformation and shear localization of ultrafine-grained (∼120 nm) pure titanium are examined. The strain hardening can be considered as having two regimes: below and above a strain ∼0.04; at this point there is a drastic decrease in the slope. The strain-rate sensitivity of ultrafine-grained...
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Published in: | Acta materialia 2017-02, Vol.125 (C), p.210-218 |
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Main Authors: | , , , , , |
Format: | Article |
Language: | English |
Subjects: | |
Citations: | Items that this one cites Items that cite this one |
Online Access: | Get full text |
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Summary: | Dynamic deformation and shear localization of ultrafine-grained (∼120 nm) pure titanium are examined. The strain hardening can be considered as having two regimes: below and above a strain ∼0.04; at this point there is a drastic decrease in the slope. The strain-rate sensitivity of ultrafine-grained titanium is found to be approximately the same as its coarse grained counterpart. Based on experimentally determined parameters, the Zerilli-Armstrong equation is modified to describe the mechanical response of the ultrafine-grained titanium over the strain rate range 10−5 to 103 s−1. Adiabatic shear banding is examined in a forced shear configuration where large strain is imposed in a narrow region. The microstructure inside the adiabatic shear band consists of a mixture of elongated grains and equiaxed nanograins (∼40 nm) that are significantly smaller than the initial grains (∼120 nm). The formation of equiaxed nanograins is modeled through a mechanism of rotational dynamic recrystallization. This further reduction in grain size from the one generated by ECAP is interpreted in terms of the Zener-Hollomon parameter for quasistatic and dynamic deformation. The adiabatic shear band eventually fractures by a combination of brittle and ductile failure.
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ISSN: | 1359-6454 1873-2453 |
DOI: | 10.1016/j.actamat.2016.11.041 |