Advanced Characterization Techniques for Quantifying and Modeling Deformation: Plasticity Modeling / Experiments
Sponsored by: TMS Materials Processing and Manufacturing Division, TMS Structural Materials Division, TMS: Shaping and Forming Committee, TMS: Materials Characterization Committee
Program Organizers: Rodney McCabe, Los Alamos National Laboratory; Thomas Bieler, Michigan State University; Marko Knezevic, University of New Hampshire; Irene Beyerlein, University of California, Santa Barbara; Wolfgang Pantleon, Technical University of Denmark; C. Tasan, Massachusetts Institute of Technology; Arul Kumar Mariyappan, Los Alamos National Laboratory
Wednesday 2:00 PM
February 26, 2020
Room: Theater A-2
Location: San Diego Convention Ctr
Session Chair: Nathan Mara, University of Minnesota; George Pharr, Texas A&M University
2:00 PM Invited
High-throughput Elevated Temperature Nanomechanical Mapping of Fe-based Alloys: Nathan Mara1; Youxing Chen2; Eric Hintsala3; Bartosz Nowakowski3; Douglas Stauffer3; 1University of Minnesota; 2University of North Carolina, Charlotte; 3Bruker Nano Surfaces Division
Experimentally quantifying the mechanical effects of radiation damage in reactor materials in a high-throughput fashion is critical for developing next-generation alloys. This is especially true for increasingly complex multiphase alloys, where mechanical models require statistically significant datasets from experiment for the individual phases for guidance and validation. High-throughput elevated temperature nanoindentation in a vacuum environment offers the capability to spatially resolve microstructurally-dependent mechanical behavior in the fraction of the time of uniaxial testing. We will present our recent results on mechanical mapping of Fe-based materials that reveal mechanical contrast between phases at elevated temperatures that mimic reactor service conditions. Berkovich nanohardness measurements, as well as elevated temperature nanoindentation-based creep testing will be presented, and will be discussed in terms of deformation mechanisms and outlook for mechanical behavior modeling for this class of materials.
2:30 PM
Microstructure Evolution During Dynamic Compression in Titanium Characterized with the XFEL at LCLS-2: Sven Vogel1; Cindy Bolme1; Donald Brown1; Ellen Cerreta1; Joseph Mang1; Benjamin Morrow1; Kyle Ramos1; Igor Usov1; Suzanne Ali2; Damian Swift2; Eric Galtier3; Arianna Gleason3; Eduardo Granados3; Amy Lazicki2; Philip Heimann3; Despina Milathianaki3; Bob Nagler3; Luca Lutterotti4; 1Los Alamos National Laboratory; 2Lawrence Livermore National Laboratory; 3SLAC; 4Universita di Trento
Transient time of a shock wave traveling at a few thousand meters per second through ten micrometers of material is a few nanoseconds. Post mortem analysis provides only limited insight into the microstructural evolution during such a shock. The advent of XFELs as intense, short pulse X-ray sources for diffraction characterization in conjunction with high-powered optical lasers to induce shocks into materials have enabled in situ characterization during dynamic compression of single crystal or polycrystalline materials. In this presentation we report the first successful application of Rietveld analysis to obtain strains, volume fractions, and textures of the phases occurring during shock of pure titanium metal, thus providing for the first time a complete picture of the microstructure evolution during shock. A sequence of fresh samples characterized in this way with a 0.5 ns temporal resolution allowed to study for the first time the microstructural evolution in titanium during shock.
2:50 PM
Combining X-ray Diffraction Contrast Tomography and Topo-tomography to Study In-situ the Mechanics of Polycrystalline Materials: Henry Proudhon1; Wolfgang Ludwig2; Jean-Charles Stinville3; Patrick Callahan3; 1Mines Paristech Centre Des Materiaux; 2Université de Lyon; 3University of California Santa Barbara
Diffraction Contrast Tomography (DCT) remains the fastest 3D grain mapping characterization method and allow further characterization of specific crystallographic locations. Mechanical testing under in situ X-ray topo-tomography (TT), carried out at the European synchrotron, will be presented to study the incipient plasticity of polycrystalline metallic alloys. As the method becomes more and more automated, it allows both quantitative and statistical measurements in the bulk of the microstructure. Examples in both Aluminium and Titanium alloys will be shown. Coupling experiments with crystal plasticity finite element computations at the grain scale is the key to unlock microstructure-deformation mechanisms. Here, detailed activation of slip systems in selected grains located under the surface will be investigated. Simultaneous modeling/experimental approaches will be discussed in light of the results.
3:10 PM
Investigation of Residual Stress Using High Resolution XRD and Localized Lattice Rotation Under Fatigue Loading
: Ramasis Goswami1; 1Naval Research Laboratory
The characteristics of plastic zone are crucial for understanding the underlying physics of the deformation process and the generation of residual stress around a crack tip under fatigue loading. A significant change in residual stress around a fatigue crack has been observed in Al alloys. For Al 7075, the residual stress increases by 200% closer to the crack. However, in Al 1100, the residual stress decreases by 80% closer to the crack. The dislocation density increases by 25 to 30 % for Al 7075. However, it actually decreases by 10% for Al 1100. Such change in dislocation density cannot explain the observed change in residual stress closer to the crack. We conclude that the deformation associated with the lattice rotation would be a major contributing factor to the residual stress. This provides a new insight on the role of lattice rotation on the residual stress under fatigue loading.
3:30 PM Break
3:50 PM Invited
Measurement of Power Law Creep Parameters by Nanoindentation: George Pharr1; Zhiyuan Liang1; 1Texas A&M University
Great progress has been made in recent years in making mechanical property measurements at small scales by load- and depth-sensing indentation methods, also known as nanoindentation. Such measurements are usually made with sharp pyramidal indenters, which allow for high point-to-point spatial mapping of properties as well as the mechanical characterization of very thin films, thin surface layers, and small particles. Recent advances have expanded the technique to high temperatures, thus paving the way for the small-scale measurement of parameters characteristic of time-dependent creep deformation. However, in doing so, serious experimental difficulties are often encountered, and how one converts the data obtained in nanoindentation tests to the parameters normally used to characterize uniaxial creep is not at all straightforward. In this presentation, we report on recent progress in making meaningful measurements of power law creep parameters based on improved experimental methods and analytical procedures.
4:20 PM
Measurement of the Thermal Expansion of Ti-7Al Using High Energy X-ray Diffraction Microscopy: Rachel Lim1; Darren Pagan2; Joel Bernier3; JY Peter Ko2; Anthony Rollett1; 1Carnegie Mellon University; 2Cornell High Energy Synchrotron Source; 3Lawrence Livermore National Laboratory
Hexagonal metals have anisotropic coefficients of thermal expansion (CTEs), and there is little agreement in literature on the CTEs for these metals. Far-field high energy x-ray diffraction microscopy, a non-destructive, in situ, micromechanical characterization technique, has been used to determine the anisotropic CTEs for Ti-7Al. Two samples of polycrystalline Ti-7Al were continuously heated from room temperature to 850°C while far-field HEDM scans were being taken. The lattice parameters at a given temperature were calculated based on the distribution of lattice parameters of the individual grains. The results showed that the CTEs in were different in the a- and c-directions respectively, and both dropped as a function of temperature. It was also found that the equivalent strain and von Mises stress were lower after the thermal cycle with the outliers in the initial state having shifted the most after the thermal cycle.
4:40 PM
Effects of the Orientation of the α β Interphase on the Time-dependent Fatigue Behavior of Ti-6Al-4V: Kartik Kapoor1; Priya Ravi1; Jun-Sang Park2; Ryan Noraas3; Vasisht Venkatesh3; Michael Sangid1; 1Purdue University; 2Argonne National Laboratory; 3Pratt & Whitney
A crystal plasticity finite element (CPFE) model for dual phase (α and β) Ti-6Al-4V is developed, explicitly accounting for both phases. This model is calibrated using a systematic optimization routine, utilizing time-dependent cyclic and monotonic macro-scale experiments and the lattice strains for the α and β phases from in situ high-energy x-ray diffraction experiments, for multiple Ti-6Al-4V pedigrees with varying β volume fractions. Depending on the processing route, Ti-6Al-4V can exist in a wide number of microstructural forms, which often results in the α and β phases either having well-aligned slip systems (following the Burgers orientation relationship (BOR)) or having misaligned slip systems (not following the BOR). In this work, the fully-calibrated CPFE model is used to gain a comprehensive understanding of deformation behavior of Ti-6Al-4V, specifically, the effect of microstructures that follow the BOR (or not) on time dependent cyclic loading.
5:00 PM
Measurement of Strain Rate Sensitivity by the Constant Load and Hold Indentation Method: A Case Study in Calcium Fluoride: Zhiyuan Liang1; George Pharr1; 1Texas A&M University
Over the past decade, there has been a growing interest in measuring the strain rate sensitivity of materials by load- and depth-sensing indentation. These measurements are based on the finding that the macroscopic strain rate sensitivity can be determined from the relation between the indentation strain rate and its corresponding hardness. Nevertheless, the situation becomes complicated when the subject material exhibits an indentation size effect. In this case, the hardness is a function of both the indentation strain rate and the indent size. Here, we address this issue by means of a constant load and hold indentation testing method. Using single crystal calcium fluoride as a model material, it is shown that the proposed approach can obtain the size-independent hardness over four orders of indentation strain rate, which can then be used to determine the macroscopic strain rate sensitivity.