Advanced Characterization Techniques for Quantifying and Modeling Deformation: Session VI
Sponsored by: TMS Extraction and Processing Division, TMS Materials Processing and Manufacturing Division, TMS Structural Materials Division, TMS: Advanced Characterization, Testing, and Simulation Committee, TMS: Materials Characterization Committee
Program Organizers: Rodney McCabe, Los Alamos National Laboratory; 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; Olivia Underwood Jackson, Sandia National Laboratories

Wednesday 2:00 PM
March 17, 2021
Room: RM 13
Location: TMS2021 Virtual


2:00 PM  Invited
Dominant Microstructural Features for Structural Properties in Additively Manufactured AlSi10Mg: Jay Carroll1; Christopher Laursen1; Philip Noell1; John Emery1; David Moore1; Garrett Pataky2; 1Sandia National Laboratories; 2Clemson University
    The behavior of additively manufactured (AM) materials is affected by many different microstructural characteristics such as grain structure, the distribution of alloying elements, and flaw population. Some of these characteristics are dominant over the others in some circumstances depending on the loading scenario, the material, and the magnitude of the features among other variables. This work focuses on the effects of microstructural features on the structural properties and failure in AM alloy AlSi10Mg. Several experiments are presented that demonstrate the effects of various microstructural characteristics on strength, ductility, and fracture behavior. These interactions have been investigated through the analysis and alignment of several datasets from different experimental techniques. Measurements from scanning electron microscopy (SEM), X-Ray computed tomography (CT) and large numbers of high throughput tensile bars are compared.

2:30 PM  Invited
Investigation of Porosity, Texture, and Damage Evolution of Additively Manufactured 316L Stainless Steel during In-situ Tensile Loading Using High Energy X-rays: Aeriel Murphy-Leonard1; David Rowenhorst1; 1Naval Research Laboratory
    The micromechanical response of additive manufactured 316L stainless steel produced via laser powder bed fusion was investigated during in-situ tensile loading using high energy x-rays. X-ray computed tomography (XCT) measurements were performed to determine the initial porosity and monitor the evolution of porosity during tensile loading as well as detect the initiation and growth of cracks from defects in the specimens. Far-field x-ray diffraction measurements were performed to quantify crystallographic texture and the distribution of elastic strains during loading. The initial texture was so that a strong {220} texture was aligned parallel to the build direction showing the preferred crystallographic texture that arises during building. As a result of tensile deformation, a strong {111} + {200} double fibre texture develops at high tensile strains and remains until fracture. XCT confirmed that both pore wall thinning and crack bridging influenced the evolution of porosity and damage during tensile loading.

3:00 PM  
Temperature-dependent Intermittent Microplasticity: Quentin Rizzardi1; Cameron McElfresh2; Jaime Marian2; Douglas Stauffer3; Robert Maass4; 1University of Illinois Urbana Champaign; 2University of California Los Angeles; 3Bruker Nano Surfaces; 4Federal Institute for Materials Research and Testing (BAM)
    Statistical investigations of intermittent deformation indicate scale-invariance, which is a paradigm shift away from traditional concepts that rely on well-defined averages. Recently, we have developed an experimental method to trace the spatiotemporal dynamics of correlated dislocation activity that underlies stress-strain discontinuities. These experiments reveal non-trivial scaling behavior (Phys.Rev.Mat. 2 (2018) 120601) and provide rational the transition from intermittent to smooth flow (Phys.Rev.Mat. 3 (2019) 080601). Here we pay attention to the effects of temperature on the statistics of intermittent microplasticity in a bcc metal. We find an excellent agreement between the temperature-dependent stress-strain response at the small and bulk scale. A change of the slip-size distribution is observed, with increasingly small event sizes dominating with decreasing temperature. We trace the effect of temperature on the spatiotemporal velocity profiles of slip that exhibits a distinct temperature sensitivity. We discuss our results in terms of thermally activated plasticity of bcc metal.

3:20 PM  
Characterization and Modeling of Fatigue-induced Grain Growth in Ultrafine Grained Ni: Alejandro Barrios1; Ebiakpo Kakandar2; Xavier Maeder3; Gustavo Castelluccio2; Olivier Pierron1; 1Georgia Institute of Technology; 2Cranfield University; 3Empa, Swiss Federal Laboratories for Materials Science and Technology
    This work presents the evaluation of fatigue-induced grain coarsening in the ultrafine grained regions of electroplated Ni microbeams tested under bending. Electron backscatter diffraction (EBSD) tomographies reveal that microbeams with a (001) texture microstructure show abnormal grain growth after fatigue tests conducted at maximum strain amplitudes ranging from 0.18 to 0.85% and cycles ranging from 103 to 108. Results highlight cycle dependent growth of grains which exhibit a near (001) orientation along the microbeam’s length direction and average grain growth rates ranging from 10-4 to 1 nm/cycle. Finite Element Simulations of synthetic models of the same microstructure reveal that the main driving force for grain growth is the reduction in elastic strain energy, although the strain energy density of the coarser grains is not at the minimum. Additionally, the apparent Schmid factor of the coarser grains tends to be larger suggesting that plastic deformation enables grain growth.

3:40 PM  Invited
Microstructure Evolution of a Stainless Steel Produced via Laser Powder Bed Fusion Subjected to Post-Fabrication Treatments: Gwenaelle Proust1; Wen Hao Kan2; Quentin Portella3; Mahdi Chemkhi4; Magnus Garbrecht1; Delphine Retraint3; 1University of Sydney; 2Monash University; 3University of Technology of Troyes; 4EPF
    Thin specimens of 316L stainless steel were produced by laser powder bed fusion. After their manufacturing, these specimens were subjected to heat treatment at temperatures ranging from 400°C to 1000°C and/or Surface Mechanical Attrition Treatment (SMAT). SMAT is a severe plastic deformation process that enhances the surface properties of a material through the creation of an ultrafine grained layer on the top surface of the material. An investigation has been conducted to quantify the property improvements in term of hardness and tensile strength due the surface treatment. The microstructure of the different specimens was characterized using electron backscatter diffraction, transmission Kikuchi diffraction, and transmission electron microscopy. The microstructure features investigated on the specimens that have seen either or the combination of both treatments include thickness of the ultrafine grained regions, size of the grains within that region and residual strain distribution within the specimen thickness.

4:10 PM  
Informing Mechanical Model Development Using Lower-dimensional Descriptions of Microstructural Evolution: Darren Pagan1; Gideon Schmidt2; Andy Borum2; Timothy Long2; Matthew Miller2; Armand Beaudoin3; 1Pennsylvania State University; 2Cornell University; 3Cornell High Energy Synchrotron Source
    The phenomenology of engineering alloy plastic deformation is usually expressed through the modeling of internal state variables representing the evolution of underlying microstructural features. However, determination of these state variables is often indirect, utilizing macroscopic mechanical data to isolate the effects of changing microstructure, rather than direct characterization of the microstructure in-situ. Here we present a novel method combining in-situ X-ray diffraction data and dimensionality reduction to inform the development of a state variable plasticity model. The method is applied to developing a model for pure nickel deformed in uniaxial tension in the small strain regime. First, we establish connections between state variables representing the evolution of mobile dislocations and the lower-dimensional representations of the data. Following connections being made, the lower-dimensional X-ray data are used to inform the inclusion of new terms in the evolution equations of the mobile and obstacle dislocation densities.

4:30 PM  
Effects of Room Temperature Interface Sliding in TIMETAL-407 (Ti-407): Zachary Kloenne1; Gopal Viswanathan1; Stoichko Antonov2; Stephen Fox3; Michael Loretto4; Hamish Fraser1; 1Ohio State University; 2Max-Planck-Institut für Eisenforschung GmbH; 3TIMET; 4University of Birmingham
    Titanium and its alloys have shown to deform through a combination of dislocation slip and deformation twinning. Grain boundary sliding has also been reported to contribute to the plasticity of CP titanium and Ti-6Al-4V (wt.%, Ti-64) , though these results have been reported far less frequently. More recently, Ti-0.85Al-3.9V-0.25Si-0.25Fe-0.15O (wt.%, Ti-407) has been shown to deform through sliding at the alpha/beta interface. In this work, the effects of interface sliding were investigated using a combination of in-situ SEM, cross-correlation EBSD, atomic force microscopy, and TEM. Primary sliding events were observed at the onset of yield, with secondary events occurring later in the deformation process. Further analysis showed a large plastic strain gradient associated with interface sliding. Interestingly, atom probe tomography and aberration corrected STEM EDS results showed a Si enrichment at the alpha/beta interface. Ti-6Al-2Sn-2Zr-2Mo-2Cr-0.18Si (wt.%, Ti-62222S) was also studied to probe underlying effects Si may have on interface sliding.

4:50 PM  
Combined In-situ Neutron and Synchrotron X-ray Diffraction Study of Tensile Deformation and Texture Evolution in a Magnesium Alloy: Tingkun Liu1; Aashish Rohatgi1; Ke An2; Yang Ren3; Bita Ghaffari4; Erin Barker1; Arun Devaraj1; 1Pacific Northwest National Laboratory; 2Oak Ridge National Laboratory; 3Argonne National Laboratory; 4Ford Motor Company
    In-situ neutron and synchrotron X-ray diffraction (XRD) experiments were performed on an AZXM2110 (Mg-2Al-1Zn-1Ca-0.3Mn) Mg alloy to investigate deformation mechanisms during room-temperature tensile deformation. During the early stages of deformation, in-situ neutron diffraction results showed a micro yielding that was activated at 0.1 % strain by basal slips. Tensile deformation beyond micro-yielding was dominated by basal and other non-basal slips with limited extension twinning. In-situ synchrotron XRD measured texture illustrated that the as-rolled sample had a strong basal texture. Tensile deformation along rolling direction (RD) developed {10-10}//RD and {11-20}//TD texture, as well as {0002}//ND slightly spreading towards TD. Further microstructure analysis and numerical modeling will be conducted to quantitatively investigate the dislocation types and activities of various deformation modes.

5:10 PM  
Modeling the Effects of Free Surfaces on Twinning Behavior: Brandon Leu1; M Arul Kumar2; Irene Beyerlein1; 1University of California Santa Barbara; 2Los Alamos National Laboratory
    Mg and Ti have gained increased popularity among structural metals due to their high specific strength and low density. A major interest in these metals is twinning deformation since the formation and propagation of twins play a critical role in determining their strength, ductility and stability. Many experimental observations of twinning deformation are conducted using electron microscopy techniques. However, the sample preparation processes necessarily introduces free surfaces to the sample that are not in the bulk. The free surfaces can influence the defect distribution and internal stresses that are experimentally measured, making it difficult to directly use the observations to predict material behavior outside of laboratory conditions. In this study, we use elasto-viscoplastic fast-fourier-transform (EVP-FFT) crystal plasticity modeling to explore the differences between micromechanical fields found in the bulk and near free-surfaces to determine when free surface effects are important and how they affect our understanding of twins.