Mechanical Response of Materials Investigated through Novel In-situ Experiments and Modeling: Session I
Sponsored by: TMS Structural Materials Division, TMS Functional Materials Division, TMS: Advanced Characterization, Testing, and Simulation Committee, TMS: Thin Films and Interfaces Committee
Program Organizers: Saurabh Puri, VulcanForms Inc; Amit Pandey, Lockheed Martin Space; Dhriti Bhattacharyya, Australian Nuclear Science and Technology Organization; Dongchan Jang, Korea Advanced Institute of Science and Technology; Shailendra Joshi, University of Houston; Minh-Son Pham, Imperial College London; Jagannathan Rajagopalan, Arizona State University; Robert Wheeler, Microtesting Solutions LLC; Josh Kacher, Georgia Institute of Technology
Tuesday 8:00 AM
March 21, 2023
Room: Aqua 310B
Location: Hilton
Session Chair: Josh Kacher, Georgia Institute of Technology; Ashley Bucsek, University of Michigan
8:00 AM Invited
Effect of Defect Spatial Distribution on Ductile Failure in Additively Manufactured 316L: David Rowenhorst1; Aeriel Leonard2; 1Naval Research Laboratory; 2Ohio State University
Additive manufacturing (AM) has presented a new processing route for structural alloys, but also localized variations in processing conditions can lead to unique, and nonhomogenous defect populations. In this study we examine the effect that the localized part size and processing can have on the mechanical properties of AM materials, especially the influence on the ductile failure. Using using high energy X-rays at the Cornell High Energy Synchrotron Source (CHESS), the evolution of defect pore morphologies in AM 316L samples are evaluated in-situ during plastic loading. Additionally we examine the evolution of the crystallographic texture of these samples and how the the build texture influences the anisotropies in the yield strength. These results are complimented by further ex-situ 3D examinations that reconstruct the grain structure in these materials, showing further inhomogeneities in the defect and grain structures.
8:30 AM
Direct Measurement of the Effective Mechanical Properties of Additively Manufacturing Octet Truss Lattices using High Energy X-ray Diffraction: Nathan Johnson1; 1Stanford University
Modern additive manufacturing technologies have enabled manufacturing of lattice-like structures that have comparable mechanical properties to full-dense metal structures but at a fraction of the weight. As additive manufacturing technology advances trusses are being built with smaller and smaller feature sizes. This makes traditional mechanical characterization techniques difficult. This presentation details an experiment that uses high energy X-ray diffraction to measure the elastic stress-strain response of titanium octet truss lattices under compressive load. Octet truss structures were manufactured using laser powder bed fusion with truss sizes as small as 500 microns. X-ray diffraction enabled measurement of strain in regions only a hundred microns in width and height. The stress-strain response is shown along with measurements for the Young's modulus of the structure and the components of the elastic compliance tensor.
8:50 AM
Load Transfer in Ni-CrC Composites Studied by Synchrotron X-ray Diffraction and X-ray Microtomography: Lewei He1; Eshan Ganju2; Nikhilesh Chawla2; Mostafa Hassani1; 1Cornell University; 2Purdue University
Load transfer between the soft and hard phases is a critical mechanism governing the overall mechanical behavior of metal matrix composites. A complete understanding of the phenomenon requires insight beyond what can be obtained by conventional mechanical testing. In this talk, we will describe the use of synchrotron high-energy x-ray diffraction and x-ray microtomography to resolve the microstructure and the phase-specific response of Ni-CrC composites under uniaxial loading. We fabricated the composites using a solid-state additive approach, namely cold spray, that allows co-deposition of more than one type of powder particles. We studied, in detail, the three-dimensional distribution and the characteristics of reinforcing particles and defects in the as-manufactured and heat-treated composites. These were also correlated to the phase-specific lattice strains and stresses upon loading. We will discuss the extent of internal load transfer in both cases and the connection to defect characteristics in the composite.
9:10 AM
Transmission X-Ray Microscopy Reveals Role of Secondary Cracks in Hydrogen Embrittlement: Andrew Lee1; Abhinav Parakh1; Wendy Gu1; 1Stanford University
Hydrogen embrittlement of existing ferritic steel transmission pipelines imposes significant limitations for the safe and cost-effective transport of hydrogen. While post-failure fractography has been the dominate method of analysis, in-situ imaging of crack propagation and microstructural evolution provides novel insight to a mechanistic understanding of hydrogen embrittlement. In this work, we use a custom strain stage coupled with in-situ X-ray microscopy to image dynamic crack propagation and the transition from quasi-cleavage to intergranular fracture in iron films charged with hydrogen. In the quasi-cleavage regime, we observe multiple sharp crack-fronts propagating simultaneously and the formation of nanoscale voids in front of the crack. In the intergranular regime, we observe blunting of the crack tip and significant secondary cracking. We discuss the role of hydrogen in increased nucleation and growth of secondary cracks throughout deformation and their role in the transition to intergranular failure, including strain-field interactions and effect on hydrogen concentration.
9:30 AM Break
9:50 AM Invited
Three-dimensional In-situ Measurements of Martensitic Phase Transformation Across Length Scales using X-ray Topotomography and Dark-field X-ray Microscopy: Ashley Bucsek1; 1University of Michigan
Martensitic phase transformation is the enabling deformation mechanism behind a diversity of materials including multiferroics, shape memory alloys, and lightweight steels. Martensitic phase transformation operates via phase interfaces that mobilize across the microstructure, often while generating defects. Under certain conditions, the transformation is reversible, making it observable only through in-situ characterization. Here, we use synchrotron X-ray characterization to resolve the hierarchical nature of martensitic phase transformation micromechanics in situ, in 3D, and across length scales. We present experimental results on the evolution of martensite morphology, interfacial stress fields at the austenite-martensite interface, and how martensitic phase transformation interacts with and generates defects during stress-induced martensitic phase transformations in CuAlNi shape memory alloys using X-ray topotomography, diffraction contrast tomography, and dark-field X-ray microscopy. The results demonstrate how recent and ongoing advances in synchrotron X-ray characterization techniques can be used to shed new light on complex, metastable micromechanical behaviors.
10:20 AM
Damage Evolution in Al Alloys Assessed via X-ray Computed Tomography and Crystallographic Orientation Data: Philip Noell1; Raiyan Seede2; Kyle Johnson1; 1Sandia National Laboratories; 2Lawrence Livermore National Laboratory
Damage evolution in Al alloys were evaluated using in-situ X-ray computed tomography and a neural network segmentation strategy. Void nucleation was observed to occur throughout the deformation process, whereas void volume did not grow significantly until later stages of deformation. Void nucleation began prior to necking but was primarily concentrated in the rgion where the neck eventually formed - limited damage nucleation was observed outside of the neck until late stages of deformation. Inhomogeneities in void and particle spacing in the initial undeformed state of the material are observed to correlate well with the location of strain and damage localization during deformation. In-situ data were supplemented with post-mortem electron backscatter diffraction data to assess the effects of crystallographic orientation on void nucleation. These results provide new insights into ductile failure and how pre-existing defects influence rupture. SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525.
10:40 AM
Assessment of Phase-field Fracture Simulations of Brittle Fracture in Polycrystalline Materials: Mythreyi Ramesh1; Sara Gorske2; Jean-Michel Scherer2; Blaise Bourdin3; Kaushik Bhattacharya2; Katherine Faber2; Peter Voorhees1; 1Northwestern University; 2California Institute of Technology; 3McMaster University
Fracture is an important failure mechanism involving an interplay of phenomena across length scales spanning several orders of magnitude. Many experimental and computational techniques have been developed to study fracture at different length scales. The phase-field (PF) method for fracture is a powerful technique because of its ability to capture complex crack morphologies without any ad hoc criteria for nucleation or branching of cracks. However, there is a lack of systematic validation studies that compare PF fracture simulations in polycrystalline materials with experiments. We attempt to bridge this gap by comparing high-energy diffraction microscopy and tomography experiments to PF simulations starting with the same microstructure. We focus on the crack propagation paths near features like grain boundaries and triple junctions, which will clarify the impact of the diffuse treatment of the cracks in PF methods and allow the mechanical properties of grain boundaries to be estimated.
11:00 AM
On the Deformation Mechanisms of Ductility Enhanced Mg-X-Ca Alloys at Elevated Temperatures: Mohammed Said1; David Collins1; 1University of Birmingham
Magnesium alloys are lighter than commonly used structural materials, particularly for automotive applications, although poor formability at room temperature has hindered their widespread commercial use. Wrought magnesium alloys experience anisotropy due to; a strong basal crystallographic texture and dislocation motion mostly constrained to basal slip. This study explores prototype Ca-containing magnesium alloys, where the addition weakens the basal texture and improves ductility, however, the governing microplasticity processes are broadly unexplored. These alloys were investigated using in-situ synchrotron diffraction during tensile testing at forming relevant temperatures to reveal micromechanical evolution. This enabled texture and lattice strains development, related to a temperature dependency of non-basal slip, to be explored. The measurements have enabled key parameters including critical resolved shear stress and slip activation energy barriers to be determined, as a function Ca level. This approach, combined microscopy including EBSD, show significant slip activity differences when benchmarked against the commercial AZ31 Mg alloy.