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

Here, 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 (σ α→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 10 6 ≤ $$\dot{μ}$$ α→ε(s ₋1) ≤ 5×10 8. We find σ α→ε= 10.8 + 0.55 ln($$\dot{μ}$$ α→ε) for $$\dot{μ}$$ α→ε < 10 6/s and σ α→ε= 1.15($$\dot{μ}$$ α→ε) 0.18 for $$\dot{μ}$$ α→ε > 10 6/s. This $$\dot{μ}$$ response is quite similar to recent results on incipient plasticity in Fe 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 $$\dot{μ}$$ > 10 6/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.
Authors:
 [1] ;  [1] ;  [1] ;  [2] ;  [2] ;  [1] ;  [1] ;  [1] ;  [3] ;  [3] ;  [1]
  1. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
  2. Princeton Univ., Princeton, NJ (United States)
  3. Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
Publication Date:
Grant/Contract Number:
NA0002154
Type:
Accepted Manuscript
Journal Name:
Journal of Applied Physics
Additional Journal Information:
Journal Volume: 114; Journal Issue: 22; Journal ID: ISSN 0021-8979
Publisher:
American Institute of Physics (AIP)
Research Org:
Princeton Univ., NJ (United States)
Sponsoring Org:
USDOE National Nuclear Security Administration (NNSA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE
OSTI Identifier:
1337783

Smith, R. F., Eggert, J. H., Swift, D. C., Wang, J., Duffy, T. S., Braun, D. G., Rudd, R. E., Reisman, D. B., Davis, J. -P., Knudson, M. D., and Collins, G. W.. Time-dependence of the alpha to epsilon phase transformation in iron. United States: N. p., Web. doi:10.1063/1.4839655.
Smith, R. F., Eggert, J. H., Swift, D. C., Wang, J., Duffy, T. S., Braun, D. G., Rudd, R. E., Reisman, D. B., Davis, J. -P., Knudson, M. D., & Collins, G. W.. Time-dependence of the alpha to epsilon phase transformation in iron. United States. doi:10.1063/1.4839655.
Smith, R. F., Eggert, J. H., Swift, D. C., Wang, J., Duffy, T. S., Braun, D. G., Rudd, R. E., Reisman, D. B., Davis, J. -P., Knudson, M. D., and Collins, G. W.. 2013. "Time-dependence of the alpha to epsilon phase transformation in iron". United States. doi:10.1063/1.4839655. https://www.osti.gov/servlets/purl/1337783.
@article{osti_1337783,
title = {Time-dependence of the alpha to epsilon phase transformation in iron},
author = {Smith, R. F. and Eggert, J. H. and Swift, D. C. and Wang, J. and Duffy, T. S. and Braun, D. G. and Rudd, R. E. and Reisman, D. B. and Davis, J. -P. and Knudson, M. D. and Collins, G. W.},
abstractNote = {Here, 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 ≤ $\dot{μ}$α→ε(s₋1) ≤ 5×108. We find σα→ε= 10.8 + 0.55 ln($\dot{μ}$ α→ε) for $\dot{μ}$ α→ε < 106/s and σα→ε= 1.15($\dot{μ}$ α→ε)0.18 for $\dot{μ}$α→ε > 106/s. This $\dot{μ}$ response is quite similar to recent results on incipient plasticity in Fe 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 $\dot{μ}$ > 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.},
doi = {10.1063/1.4839655},
journal = {Journal of Applied Physics},
number = 22,
volume = 114,
place = {United States},
year = {2013},
month = {12}
}