Neutron and X-ray Scattering in Materials Science: Engineering Diffraction
Sponsored by: TMS Functional Materials Division, TMS: Chemistry and Physics of Materials Committee
Program Organizers: Michael Manley, Oak Ridge National Laboratory; Chen Li, University of California-Riverside; Jennifer Niedziela, Oak Ridge National Lab; Hillary Smith, Swarthmore College
Wednesday 8:30 AM
March 22, 2023
Room: Aqua 311B
Location: Hilton
Session Chair: Chihpin (Andrew) Chuang, Argonne National Lab
8:30 AM Invited
Pyrochlore as Potential Nuclear Waste Form – Structure-property Insights from Scattering Experiments: Sarah Finkeldei1; Maik Lang2; Gordon Thorogood3; 1University of California-Irvine; 2University of Tennessee, Knoxville; 3Australian Nuclear Science and Technology Organisation
Pyrochlore oxides (A2B2O7, with B = Zr, Ti) are considered as potential nuclear waste forms. The immobilization of radionuclides, e.g. Pu, can lead to non-stoichiometric pyrochlores that can undergo order-disorder phase transformations into defect fluorite structures due to the chemical substitutions as well as response to self-irradiation. Synchrotron X-ray scattering was utilized to gain insights into the structural response of radionuclide immobilization. X-ray diffraction data enable insights into the long-range structure, which was complemented by short-range order analysis via pair distribution functions. Self-irradiation was mimicked by Helium irradiation of zirconate and titanate pyrochlores. The different irradiation response of these two potential waste forms was analyzed by a combination of X-ray and neutron diffraction as well as transmission electron microscopy and electron backscattering diffraction.
9:00 AM
High Speed Operando X-ray Diffraction and Imaging during 3D Laser Printing: Steven Van Petegem1; 1Paul Scherrer Institut
Laser powder bed fusion (L-PBF) is a “layer-by-layer” additive manufacturing process, in which parts are built up by adding precursor powder layers and selectively scanning them with a high-power laser, resulting in the densification of consecutive slices of a three-dimensional object. During L-PBF, heating and cooling rates up to 10 million degrees per second have been reported, leading to far-from-equilibrium microstructures, high residual stresses and various defects that are detrimental to the thermo-mechanical reliability of the printed components.To study these issues, we have developed a dedicated miniaturized L-PBF device optimized for installation at synchrotron X-ray diffraction and imaging beamlines. In combination with fast X-ray detectors, this setup allows tracking the evolution of crystallographic phases, local temperature, cracks, pores, etc. during 3D laser printing. In this presentation, I will demonstrate how this device was used to study the microstructure evolution in various metallic systems with time resolutions down to 25µs.
9:20 AM
Determination of Residual Stress and Strain Fields during Cold Expansion Processing Using Complementary Diffraction Techniques: Nicholas Bachus1; Donald Brown2; Christopher Budrow3; Bjųrn Clausen2; J.Y. Peter Ko4; Kelly Nygren4; Renan Ribeiro5; Michael Hill1; 1University Of California Davis; 2Los Alamos National Laboratory; 3Budrow Consulting LLC; 4Cornell High Energy Synchrotron Source; 5Hill Engineering LLC
Synchrotron X-ray and time-of-flight neutron diffraction measurements are used to determine elastic residual strain and stress fields in the vicinity of geometrically large holes in 7050-T7451 aluminum plate samples caused by cold expansion (Cx) processing. The measurements are relevant because Cx is widely used in the aircraft industry to improve the fatigue resistance of critical components containing fastener holes. Recent model development reveals a large discrepancy between computed and measured residual stress fields. The Los Alamos SMARTS and Cornell FAST diffractometers are used to determine the residual stress and strain fields in partially (50%) and fully (100%) processed samples. Consistent strain trends are observed in both samples for the two types of measurements, with the datasets being complementary: neutrons offering determination of stress, and X-rays revealing fine spatial variations of strain. Together these data provide opportunities for improving process models of Cx.
9:40 AM
Micromechanical Response of Nitrocarburized Steel Studied by In-situ X-ray Microdiffraction during Nanoindentation: Albin Stormvinter1; Shun Yu1; Melina da Silva1; Gabriel Spartacus2; Peter Hedstrom2; Anton Davydok3; 1RISE; 2KTH Royal Institute of Technology; 3Helmholtz Hereon
Nitrocarburizing of steel produces a complex surface microstructure that can be subdivided into a compound layer (CL) on the surface and a diffusion zone (DZ) below. The CL generally constitute of two types of iron nitride phases, ε and γ’, whereas in the DZ ferrite is strengthened by solid solution and small nitride- and carbide-precipitates. Nitrocarburizing can also be combined with post oxidation to yield a few microns of oxide to further improve corrosion properties. The nitrocarburized steel components will benefit from improved fatigue, wear, friction and corrosion properties. However, the understanding of the relationship between the nitrocarburizing process, obtained microstructure and properties is not well established. By using in-situ nanoindentation and scanning synchrotron x-ray microbeam diffraction we have interrogated the micromechanical response of two different types of nitrocarburized steel surfaces with different phase constitutions. The roles of ε-phase- and γ’-phase on the micromechanical properties of the components are discussed.
10:00 AM Break
10:15 AM
On the Estimation of Elastic Constants in Low Symmetry Materials with In-situ Neutron Diffraction Measurements: Nathan Peterson1; Daniel Savage2; Sean Agnew1; Donald Brown2; Bjųrn Clausen2; Aaron Stebner3; Elena Garlea4; 1University of Virginia; 2Los Alamos National Laboratory; 3Georgia Institute of Technology; 4Y-12 National Security Complex
Knowledge of the single crystal elastic constants for a given material is essential for many modeling efforts in materials science. Traditionally, these constants were measured with acoustic methods on single crystals, which are difficult to obtain for certain materials. Alternatively, an assessment can be made using in-situ diffraction measurements on polycrystals, which provides a stress-strain response at both the aggregate and grain set level. These two measures are then connected with a micromechanical model, such as the Voigt, Reuss, or Kröner (self-consistent) models. In this work, a combined elastic self-consistent model and whole pattern fitting approach was used to analyze in-situ neutron diffraction data to estimate the elastic constants of two low symmetry materials: α-U (orthorhombic) and B19’ NiTi (monoclinic). The robustness of the approach was evaluated through a variance-based sensitivity analysis, while the uncertainty of the elastic constant estimates was assessed using a Markov Chain Monte Carlo (MCMC) approach.
10:35 AM
Bulk Residual Stress and Strain Measurements Near Geometrically Large Holes for Improving Cold Expansion Process Models: Michael Hill1; Nicholas Bachus1; Donald Brown2; Chris Budrow3; Michael Burba4; Bjųrn Clausen2; Adrian DeWald5; J.Y. Peter Ko6; Kelly Nygren6; Mark Obstalecki4; Robert Pilarczyk5; Renan Ribeiro5; Paul Shade4; Matthew Shultz7; 1University of California Davis; 2Los Alamos National Laboratory; 3Budrow Consulting LLC; 4Air Force Research Laboratory; 5Hill Engineering, LLC; 6Cornell High Energy Synchrotron Source; 7Fatigue Technology, Inc
We report on a series of measurements of residual stress and residual strain near large cold expanded holes. The work was undertaken to improve engineering models of the hole cold expansion (Cx) process and support more effective use of compressive residual stress treatments that extend fatigue life and/or inspection periods. Measurements were made in samples with a 25.4 mm thickness and a centered 25.4 mm hole, so the features are large relative to typical applications. Measurements use a complement of diverse techniques: the contour method, time-of-flight neutron diffraction (LANL SMARTS instrument), and EDXRD (CHESS FAST instrument). Comparisons of data show all techniques in agreement. Comparisons of data to outputs from a process simulation are consistent with systematic discrepancies reported in prior publications that have significant effects on forecasts of Cx fatigue benefits. The measurement data therefore provide an engineering basis for making improvements to the process simulation.
10:55 AM
The Application of Neutron Scattering to Hard Metals and Related Systems: Ahmet Bahadir Yildiz1; Prasath Babu2; Susanne Norgren3; Peter Hedstrom2; 1Scatterin AB; 2KTH Royal Institute of Technology; 3Lund University, Sandvik Coromant R&D
Neutron scattering is one of few characterization methods that allow for non-destructive bulk characterization of micro- and nanostructures in hard metals that contain heavy elements such as tungsten. The non-destructive nature of neutron scattering can be applied to follow structural evolution in real-time during processing under relevant technical conditions. In the present work we elaborate on the use of in-situ neutron scattering to enhance the mechanistic understanding of structural evolution during high-temperature synthesis of carbides and heat treatment of hard metals as well as during high-temperature deformation of hard metals. In-situ small-angle neutron scattering and/or diffraction are applied depending on the structural scale of interest. The results obtained assist the interpretation of the underlying mechanisms of grain coarsening and inhibition during heat treatment of hard metals and creep property enhancement in doped hard metals at application temperatures as well as phase decomposition in hard metal relevant carbides.
11:15 AM
The Forging and the Precipitation Behaviour in the New VDM© Alloy 780 Studied via In Situ High Energy X-ray Diffraction: Massimo Fritton1; Frank Kümmel1; Andreas Kirchmayer2; Andreas Stark3; Masood Hafez Haghighat4; Bodo Gehrmann4; Steffen Neumeier2; Ralph Gilles1; 1Technische Universität München; 2Friedrich-Alexander-Universität Erlangen-Nürnberg; 3Helmholtz-Zentrum hereon GmbH; 4VDM Metals International GmbH
Polycrystalline Ni-based superalloys are developed for applications in extreme conditions such as the heavily stressed rotating discs in the hot sections of modern gas turbines or jet engines. In this study, the forging and the γ“ precipitation during cooling and age hardening are analysed of the newly developed polycrystalline VDM© Alloy 780 via in situ high energy x-ray diffraction to mimic the entire fabrication process. In the first step, during the compressive deformation at around 1000°C subgrain formation is observed and the evolution of a texture due to grain rotation in preferred orientations. In the second step, directly after the hot forming, three different cooling rates are applied and their influence on the precipitation of the γ“ phase is determined. Finally, the age-hardening step of the alloy is studied comparatively at holding temperatures of 720°C and 800°C. The diffraction data are substantiated by supplementary microscopic examinations.
11:35 AM
In Situ X-ray Diffraction Study of the (Ba,Sr)TiO3 Solid State Reaction: Leah Bellcase1; Corrado Harper1; Elizabeth Dickey2; Jennifer Forrester1; Jacob Jones1; 1North Carolina State University; 2Carnegie Mellon University
In situ high-temperature X-ray diffraction was used to investigate the phase evolution of precursors used to synthesize xBaTiO3-1-xSrTiO3 (BST), a potential component in multilayer capacitors. While single-phase materials are expected over large composition ranges, the system may not achieve full equilibrium during processing and retain secondary phases, leading to diminished properties in the final material. The kinetics of the phase formation may be influenced by processing conditions, and the composition and physical properties of the precursor materials.Experiments monitored the time-dependent reactions and solid-state phase transformations of the individual precursors (BaCO3, SrCO3, and TiO2), and combinations of precursors. Phase transitions were observed during heating of binary oxides, and in combination with TiO2. The BaCO3 and SrCO3 series showed lattice interdiffusion creating an intermediate phase, which then separated into high temperature BaCO3 and SrO phases. Interestingly, intermediate phases were not prerequisite in the formation of the final perovskite BST at ~950°C.