Paper Title:
High-Rate Plastic Deformation of Nanocrystalline Tantalum to Large Strains: Molecular Dynamics Simulation
  Abstract

Recent advances in the ability to generate extremes of pressure and temperature in dynamic experiments and to probe the response of materials has motivated the need for special materials optimized for those conditions as well as a need for a much deeper understanding of the behavior of materials subjected to high pressure and/or temperature. Of particular importance is the understanding of rate effects at the extremely high rates encountered in those experiments, especially with the next generation of laser drives such as at the National Ignition Facility. Here we use large-scale molecular dynamics (MD) simulations of the high-rate deformation of nanocrystalline tantalum to investigate the processes associated with plastic deformation for strains up to 100%. We use initial atomic configurations that were produced through simulations of solidification in the work of Streitz et al [Phys. Rev. Lett. 96, (2006) 225701]. These 3D polycrystalline systems have typical grain sizes of 10-20 nm. We also study a rapidly quenched liquid (amorphous solid) tantalum. We apply a constant volume (isochoric), constant temperature (isothermal) shear deformation over a range of strain rates, and compute the resulting stress-strain curves to large strains for both uniaxial and biaxial compression. We study the rate dependence and identify plastic deformation mechanisms. The identification of the mechanisms is facilitated through a novel technique that computes the local grain orientation, returning it as a quaternion for each atom. This analysis technique is robust and fast, and has been used to compute the orientations on the fly during our parallel MD simulations on supercomputers. We find both dislocation and twinning processes are important, and they interact in the weak strain hardening in these extremely fine-grained microstructures.

  Info
Periodical
Materials Science Forum (Volumes 633 - 634)
Edited by
Yonghao Zhao and Xiaozhou Liao
Pages
3-19
DOI
10.4028/www.scientific.net/MSF.633-634.3
Citation
Robert E. Rudd, 2009, Materials Science Forum, 633-634, 3
Online since
November 2009
Authors
Price
US$ 28,-
Share
Authors: Yuri Estrin, Ralph Jörg Hellmig, Hyoung Seop Kim
29
Authors: Minoru Umemoto, Yoshikazu Todaka, Jin Guo Li, Koichi Tsuchiya
Abstract:Formation of nanocrystalline structure by severe plastic deformation has studied extensively. Although ultra fine grained structure (grain...
2787
Authors: Yulia Ivanisenko, Hans J. Fecht
Abstract:We suggest a simple method to study the mechanical behaviour of nanocrystalline (nc) samples in compression-torsion mode. High applied...
203
Authors: T. Chan, David Backman, R. Bos, T. Sears, I. Brooks, Uwe Erb
Chapter 12: Nanostructured Materials
Abstract:Commercially available polycrystalline nickel (grain size: 30 µm) and electrodeposited nanocrystalline nickel (grain size: 30 nm) were...
480