Unraveling the temperature dependence of the yield strength in single-crystal tungsten using atomistically-informed crystal plasticity calculations

Significance Statement

 The plastic response of body-centered cubic (bcc) metals such as iron or tungsten is notoriously difficult to predict due to the existence of a strong temperature dependence and the so-called non-Schmidt effects. Non-Schmidt behavior manifests itself in the form of a tension/compression asymmetry in uniaxial tensile tests that is unique to crystals with bcc structure. For its part, temperature effects are such that bcc metals generally behave as brittle crystals at low temperatures and as ductile ones at higher temperatures. The origin of this behavior can be found in the particular features of screw dislocation cores, which –in contrast with other crystal structures– display highly nonplanar characteristics. Despite the fundamental nature of this issue, and the technological importance of bcc metals, no truly quantitative model for bcc plasticity existed in the literature. Cereceda et al. have developed a numerical approach that can simulate macroscopically relevant time and length scales and, at the same time, predict the temperature and tensile response of bcc crystals purely from first-principles physical information. Their approach links the atomistic properties of screw dislocations with a macroscopic representation of plasticity that allows the calculations to be compared one-to-one with experiments. Their results show excellent agreement for the case of tungsten, and their methodology provides the basis for quantitative explaining the anomalous plastic behavior of bcc metals and their alloys.

Unraveling the temperature dependence of the yield strength in single-crystal tungsten using atomistically-informedcrystal plasticity calculations. . Advances in Engineering

About The Author

Dr Martin Diehl works at the Max-Planck-Institut für Eisenforschung in the department “Microstructure physics and alloy design” headed by Prof. Dierk Raabe. He obtained his Ph.D. in materials engineering in 2015 from RWTH Aachen. From 2005 to 2010 he studied mechanical engineering (Diplom) at TU München, specialising in materials engineering and numerical mechanics. Martin Diehls scientific interest is the understanding of grain interactions in polycrystalline materials which he investigates with the help of simulations using the DAMASK toolbox. 

 

About The Author

 

Professor J. Manuel Perlado is the chair of the Nuclear Physics Department and Director of the Institute of Nuclear Fusion at the Polytechnic University of Madrid, Spain. His main research interests are in the fields of nuclear fusion, irradiation damage of nuclear materials, transmutation, and neutronics, where he has authored over 250 peer-reviewed articles..

About The Author

Professor Dierk Raabe graduated from RWTH Aachen in physical metallurgy and metal physics. Later he joined Carnegie Mellon University and the High Magnet Field Laboratory in Tallahassee. Currently he is at the Max-Planck Institut für Eisenforschung in Düsseldorf and Professor at RWTH Aachen University. His research interests are in atom probe tomography, alloy design, microstructures, simulations and mechanical properties of metallic alloys.

 

About The Author

Professor Jaime Marian is an Associate Professor in the Department of Materials Science and Engineering at the University of California Los Angeles (UCLA). His main research focus is the computational modeling of the mechanics and thermodynamics of advanced materials for energy. He spent nine years at Lawrence Livernore National Laboratory as a staff scientist developing methods to predict materials behavior under extreme irradiation, loading, and temperature conditions. Prior to that he was a Postdoctoral Scholar at the California Institute of Technology, where he worked on spall failure in metals using computational mechanics.

 

About The Author

Dr David Cereceda received his PhD degree from Universidad Politecnica de Madrid in 2015 under the guidance of Prof. Jaime Marian and Prof. José Manuel Perlado. His PhD research, performed at Lawrence Livermore National Laboratory and University of California Los Angeles, focused on the multiscale modeling of tungsten as one of the main candidates for fusion energy applications.  He is currently a Postdoctoral fellow at Hopkins Extreme Materials Institute, where he is mentored by Profs. Lori Graham-Brady and Nitin Daphalapurkar. His research at Hopkins is aimed at understanding the dynamic fragmentation of brittle materials under extreme loading conditions. 

About The Author

Dr Franz Roters has been group leader at the Max-Planck-Institut für Eisenforschung since 2000. He studied physics at TU Braunschweig. In 1999, Roters earned his PhD degree at RWTH Aachen and received his Habilitation degree in computational material science 2011 also from RWTH Aachen. Since this time he is Post Doctoral Lecturer in Aachen. From 1999 to 2000, he worked at the Research and Development department of VAW aluminium in Bonn. Roters is mainly active in computational materials science and crystal plasticity.

Journal Reference

International Journal of Plasticity, Volume 78, March 2016, Pages 242-265.

David Cereceda1,2,3, Martin Diehl4, Franz Roters4, Dierk Raabe4, J. Manuel Perlado3, Jaime Marian1

Show Affiliations
  1. Department of Materials Science and Engineering, University of California Los Angeles, Los Angeles, CA 90095, USA
  2. Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, CA, USA
  3. Instituto de Fusión Nuclear, Universidad Politécnica de Madrid, E-28006 Madrid, Spain
  4. Max-Planck-Institut für Eisenforschung, Max-Planck-Straße 1, 40237 Düsseldorf, Germany.  

Abstract

We use a physically-based crystal plasticity model to predict the yield strength of body-centered cubic (bcc) tungsten single crystals subjected to uniaxial loading. Our model captures the thermally-activated character of screw dislocation motion and full non-Schmid effects, both of which are known to play critical roles in bcc plasticity. The model uses atomistic calculations as the sole source of constitutive information, with no parameter fitting of any kind to experimental data. Our results are in excellent agreement with experimental measurements of the yield stress as a function of temperature for a number of loading orientations. The validated methodology is employed to calculate the temperature and strain-rate dependence of the yield strength for 231 crystallographic orientations within the standard stereographic triangle. We extract the strain-rate sensitivity of W crystals at different temperatures, and finish with the calculation of yield surfaces under biaxial loading conditions that can be used to define effective yield criteria for engineering design models.

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