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Time-dependence of the alpha to epsilon phase transformation in iron

Author(s): Smith, Raymond F; Eggert, Jon H; Swift, Damian C; Wang, Jue; Duffy, Thomas S; et al

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Abstract: Iron was ramp-compressed over timescales of 3 ≤ t(ns) ≤ 300 to study the time-dependence of the α→ε (bcc→hcp) phase transformation. Onset stresses (σα→ε) for the transformation ∼14.8-38.4 GPa were determined through laser and magnetic ramp-compression techniques where the transition strain-rate was varied between 106 ≤μ̇ α→ε(s−1) ≤ 5×108. We find σα→ε= 10.8 + 0.55 ln(μ̇ α→ε) for μ̇ α→ε < 106/s and σα→ε= 1.15(μ̇ α→ε)0.18 for μ̇ α→ε > 106/s. This μ̇ response is quite similar to recent results on incipient plasticity in Fe [Smith et al., J. Appl. Phys. 110, 123515 (2011)] suggesting that under high rate ramp compression the α→ε phase transition and plastic deformation occur through similar mechanisms, e.g., the rate limiting step for μ̇  > 106/s is due to phonon scattering from defects moving to relieve strain. We show that over-pressurization of equilibrium phase boundaries is a common feature exhibited under high strain-rate compression of many materials encompassing many orders of magnitude of strain-rate.
Publication Date: 11-Dec-2013
Citation: Smith, R. F., J. H. Eggert, D. C. Swift, J. Wang, T. S. Duffy, D. G. Braun, R. E. Rudd et al. "Time-dependence of the alpha to epsilon phase transformation in iron." Journal of Applied Physics 114, no. 22 (2013): 223507. doi:10.1063/1.4839655.
DOI: doi:10.1063/1.4839655
ISSN: 0021-8979
EISSN: 1089-7550
Pages: 223507
Language: English
Type of Material: Journal Article
Journal/Proceeding Title: Journal of Applied Physics
Version: Final published version. Article is made available in OAR by the publisher's permission or policy.

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