Understanding and Predicting Dynamic Behavior of Materials : Deformation in Metals
Sponsored by: TMS Materials Processing and Manufacturing Division, TMS Structural Materials Division, TMS: Computational Materials Science and Engineering Committee, TMS: Mechanical Behavior of Materials Committee
Program Organizers: Saryu Fensin, Los Alamos National Laboratory; Avinash Dongare, University of Connecticut; Benjamin Morrow, Los Alamos National Laboratory; Marc Meyers, University of California, San Diego; George Gray, Los Alamos National Laboratory
Tuesday 2:00 PM
February 25, 2020
Room: 5A
Location: San Diego Convention Ctr
Session Chair: Darby Luscher, Los Alamos National Laboratory
2:00 PM
Slip, Twinning and Phase Transformations in Multiphase Metallic Materials under Shock Loading Conditions: Avanish Mishra1; Avinash Dongare1; 1University of Connecticut
The shock deformation and spall failure behavior of layered FCC/BCC multiphase metallic materials usually rely on the ability of the interface to control the dislocation evolution behavior, which is determined by the interface microstructure, i.e., orientation-relationship, spacing, impedance mismatch, etc. The recent capabilities to synthesize FCC/BCC laminate microstructures enable the understanding of the competing mechanisms of dislocation slip, deformation twinning, and phase transformation under dynamic loading conditions. Large scale molecular dynamics (MD) simulations are carried out to investigate the spallation behavior of various possible Cu/Fe laminate microstructure with variation in size and orientation relationship of interfaces. The shock response behavior of this nanolaminate is characterized by deformation twinning and (BCC→HCP) phase transformation. The ductile failure behavior under the dynamic loading conditions transpires due to the interaction of reflected waves, forming triaxial tensile stresses, and is characterized by nucleation, growth, and coalescence of voids. This talk discusses the role of interface microstructure on the shock wave propagation and reflection behavior during shock compression and the contributions to plasticity from twinning and phase transformation behavior. The spacing of interfaces, as well as the loading conditions (shock pulse), modifies the wave reflection behavior and results in modifications in void nucleation at the interface and in the FCC and BCC phases. The MD snapshots are characterized to identify the twining/de-twinning mechanisms as well as the reverse phase transformation mechanisms (HCP→BCC) and the role of these mechanisms on damage nucleation and evolution behavior. The effect of orientation-relationship and impact velocity on the deformation response and the spall strength will be presented.
2:20 PM
High-throughput Atomistic Investigations of Dynamic Defect responses in Crystalline Materials: Lucas Hale1; 1National Institute of Standards and Technology
Classical atomistic simulations are powerful tools that can reveal connections between atomic-level structures and larger-scale dynamic mechanical behaviors. However, the empirical nature of classical interatomic potentials makes predicted results strongly dependent on the choice of potential. To help address this problem, high-throughput atomistic calculations are being performed to characterize how hundreds of interatomic potentials predict bulk crystalline and defect properties at different temperatures. Collecting such data makes it possible to compare predictions across potentials and select the atomic models most suited for specific investigations. The high-throughput tools also provide a means of exploring the relationships between different properties.
2:40 PM
Twinning/Detwinning Behavior of Cu-Ta Trilayer Under Shock Loading Conditions at The Atomic Scale: Marco Echeverria1; Avinash Dongare1; 1University of Connecticut
The shock, spall failure behavior, and void nucleation response of multiphase metallic microstructures comprised of FCC/BCC phases are determined by the interplay between dislocation slip and deformation twinning. MD simulations indicate that deformation twinning has a contrasting response for Cu and Ta phases, where an increase of twin volume fraction in Cu results in an increase in spall strengths, whereas it decreases for Ta. Large MD simulations are carried out to investigate the role of interface structure and spacing of Cu/Ta interfaces on the spall strengths, and twinning/de-twinning behavior of Ta. The simulations comprise of tri-layer (Cu-Ta-Cu) alloys with layer thicknesses ranging from 100 nm to 500 nm to investigate the role of shock wave reflections at the interfaces in the Ta layer and the resultant spall response. The links between nucleation/growth of voids, dislocation evolution, and the role these play on the spall response of Cu-Ta alloys are presented.
3:00 PM
Thermodynamic Theory of Crystal Plasticity – Formulation and Application to fcc Copper: Charles Lieou1; Curt Bronkhorst2; 1Los Alamos National Laboratory; 2University of Wisconsin-Madison
We present a thermodynamic description of crystal plasticity. Our formulation is based on the Langer-Bouchbinder-Lookman (LBL) theory of dislocation motion, which asserts the fundamental importance of an effective temperature that describes the state of configurational disorder and therefore the dislocation density of the crystalline material. We extend the LBL description from isotropic plasticity to crystal plasticity with many slip systems. Finite-element simulations show favourable comparison with experiments on polycrystal fcc copper under uniaxial compression. The thermodynamic theory of crystal plasticity thus provides a thermodynamically consistent and physically rigorous description of dislocation motion in crystals. We also discuss new insights about the interaction of dislocations belonging to different slip systems.
3:20 PM Break
3:40 PM
Structure / Property (Constitutive and Dynamic Strength / Damage)
Characterization of Additively Manufactured (AM) 316L SS: George Gray1; David Jones1; Veronica Livescu1; Colt Montgomery1; Daniel Martinez1; Michael Brand1; Saryu Fensin1; 1Los Alamos National Laboratory
Certification requirements generally involve meeting engineering and physicsrequirements tied to the functional requirements of the engineering component and finally process and product qualification. In this presentation, the results of a study quantifying the microstructure and constitutive behavior of 316L SS fabricated using an EOS 400 – Laser-Powder-Bed Additive Manufacturing(AM) method is presented. The mechanical behavior of the AM built 316L SS was characterized using compression testing as a function of strain rate, temperature, and across a laser-laser overlap build region for this 4-laser EOS machine. The dynamic damage evolution and failure response of the AM-316L SS material as a function of position away from and across the build overlap region, as well as wrought 316L SS, was probed using flyer-plate impact driven spallation experiments. The damage evolution of the AM-316L SS and wrought-316L SS was characterized using optical metallography and electron-back-scatter diffraction (EBSD).
4:00 PM
Laser Shock Wave Induced Mechanical Response on an Additive Manufacturing Ti6Al4V Alloy: Bathusile Masina1; 1Council for Scientific and Industrial Research
Several studies has been done on the shock-induced mechanical response of the commercial Ti6Al4V sample but studies on its counterpart Ti6Al4V sample produced using Additive Manufacturing (AM) is quite limited. In this study, a high energy pulsed laser (1064 nm, 10 Hz and 8-10 ns) was used to induce a shock wave on a Ti6Al4V sample while varying the sample thickness from 0.5 to 1.5 mm, respectively. These Ti6Al4V samples were produced using an AM process called selective laser melting (SLM). A velocity interferometer system for any reflector (VISAR) system was employed to study the mechanical response of the Ti6Al4V samples. The mechanical properties and Hugoniot elastic limit (HEL) of the AM Ti6Al4V were determined using the VISAR back free surface velocity profile. Furthermore, the shock wave parameters were determined as well. Comparison study of the mechanical response and measured HEL for the commercial and AM Ti6Al4V will be discussed.
4:20 PM
Mesoscale Modeling of Shock Loading Induced Twinning/De-twinning and Spall Failure Behavior of Ta Microstructures: Sergey Galitskiy1; Avinash Dongare1; 1University of Connecticut
Classical molecular dynamics (MD) simulations are carried out to investigate the role of shock pressures and texture on the twinning/de-twinning behavior and resulting spall strengths at the atomic scales. The MD simulations, however, are limited to small system sizes of up to a few hundred nanometers. In addition, quasi-coarse-grained dynamics (QCGD) simulations, that use a reduced number of representative atoms (R-atoms) and scaling relationships for atomic scale interatomic potentials, is shown to be able to extend the capabilities of MD simulations to the mesoscales. The QCGD approach is validated by reproducing the MD-predicted temporal evolution of pressure, defects and void nucleation, growth and coalescence mechanisms during shock compression and spall failure. The capability of QCGD will be demonstrated for Ta microstructures with dimensions of up to tens of microns under varying loading conditions focusing on the mesoscale mechanics of twinning/de-twinning and damage nucleation and evolution behavior.
4:40 PM
Experimental Study on the Dynamic Behavior of Ti6AL4V ELI: Tshifhiwa Maimela1; Madindwa Mashinini1; Monnamme Tlotleng2; Bathusile Masina2; 1University of Johannesburg; 2CSIR
In this study, a dynamic behavior of Ti6Al4V ELI under high pressure shock waves was investigated. High energy 1064 nm Nd:YAG laser was used to induce a shock wave onto Ti6Al4V ELI specimens with thicknesses ranging from 0.25 to 0.5 mm. The shock wave velocity was measured using the VISAR Interferometer with the intention of analyzing the dynamic behavior of Ti6Al4V ELI. There are no studies reporting on shock wave induced by lasers that are studied using VISAR Interferometer on Ti6Al4V ELI; hence the relevance of this current study. The results show that the impact velocity increased with the decrease in sample thickness. In addition the thinner sample deformed easier than the thick sample. This is in agreement with Hugoniot Elastic Limit.