Mechanical Response of Materials Investigated Through Novel In-Situ Experiments and Modeling: Session II
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; Josh Kacher, Georgia Institute of Technology; Minh-Son Pham, Imperial College London; Jagannathan Rajagopalan, Arizona State University; Robert Wheeler, Microtesting Solutions LLC

Monday 2:00 PM
February 28, 2022
Room: 206B
Location: Anaheim Convention Center

Session Chair: Shailendra Joshi, University of Houston; C. Tasan, Massachusetts Institute of Technology


2:00 PM  Invited
Linking Local and Global Strains: From Films to Lattices: Mitra Taheri1; 1Johns Hopkins University
    In the quest for improved materials, length scale effects are an option for tuning properties. Reduction in grain size can increase strength and manipulation of strut size and distribution in lattice structures can alter myriad properties. A key challenge in using length scale as a tuning parameter is understanding stresses and strains across scales to inform the design process. This talk reviews recent work that leverages a suite of spatially resolved and in situ/operando techniques including diffraction and spectroscopy, to correlate global and local strains and stresses during microstructural evolution. Specifically, linking grain to subgrain scales is addressed. The work presented describes a platform for reliable, multiscale tuning in systems such as additively manufactured materials, high entropy alloys, and fine-grained metals.

2:30 PM  
Investigation of Dislocation-grain Boundary Interactions through In-situ Micro-mechanical Testing with Strain Mapping: Dongyue Xie1; Sumit Suresh1; Jade Peng1; Jonathan Gigax1; Nithin Mathew1; Darby Luscher1; Abigail Hunter1; Saryu Fensin1; Nan Li1; 1Los Alamos National Laboratory
    In polycrystalline metals and alloys, grain boundaries (GBs) are the largest impediment to the dislocation motion and can dramatically change the mechanical properties of material. Therefore, understanding the process of the interactions between dislocations and GBs will be helpful for predicting the properties of material. Different phenomenon can occur during this process. For example, a dislocation can transmit across a GB, be partially absorbed at the GB, or glide along the GB and re-emit, altering the GB structure. To investigate the detailed information about deformation process, we used in-situ micro-pillar compression testing with simultaneous high angular resolution electron backscatter diffraction characterization. The strain maps and correlated lattice rotation of different moments during the tests were calculated. The influence of grain boundary structure on the mechanical property and interaction behavior with dislocations were explored. In addition, such information has provided a unique validation for the modeling at both atomic and mesoscales.

2:50 PM  
Effect of Temperature and Composition on the Superelasticity of SrNi2P2 Single Crystal: Shuyang Xiao1; Juan Schmidt2; Gorgen-Lesseux Guilherme2; Paul Canfield2; Seok-Woo Lee1; 1University of Connecticut; 2Iowa State University
    SrNi2P2 , one of ThCr2Si2-type intermetallic compounds, has been discovered to exhibit the ultrahigh elastic strain limit of ~18% via forming and breaking P-P bonds. The process of forming and breaking P-P bonds must be strongly sensitive to temperature change and elemental doping. In this work, therefore, the effects of temperature and composition on superelasticity of SrNi2P2 have been investigated. We have developed the state-of-the-art in-situ cryogenic nanomechanical tester to study the temperature effect on superelasticity of pristine SrNi2P2. SrNi2-XRhxP2 (x = 0.2, 0.3, 0.4) were also studied to understand how Rh-doping modifies the lattice structure and the superelastic behavior. It was found that both the critical stress and strain of lattice collapse are significantly affected by temperature and composition. Also, we discovered the deformation-induced structural stabilization due to the metastable state of as-received doped samples. Our results provide a fundamental insight into understanding the superelasticity of ThCr2Si2-type intermetallic compounds.

3:10 PM  
Deformation Behavior Identification of a Friction Stir Welded 304L Austenitic Stainless-steel Using In-situ EBSD: Nitish Bibhanshu1; Maxim Gussev1; Wei Tang1; 1Oak Ridge National Laboratory
    Friction stir welding (FSW) is a solid-phase joining technique that may join irradiated materials without helium-induced cracking due to its low heat generation capabilities along with low mechanical induced thermal strain gradient. In this work, we present microstructural evolution after friction stir welding (FSW) of 304L austenitic stainless-steel that shows the distribution of the Helium (He) bubbles in the stir zone (SZ) as well as in the thermomechanical affected zone (TMAZ) with an amount of ~5.2 appm. The investigations were carried out on three tensile miniature samples picked from the SZ, TMAZ, and base metal (BM). The FSW causes a gradient in the microstructural features like grain size, grain boundary character and their percentage from the BM to the SZ. With three different microstructural features, deformation responses were investigated. Results reveal that the change of the grain boundary character occurred during the deformation and it also influences the hardening response.

3:30 PM Break

3:50 PM  
Transmission X-ray Microscopy Reveals Role of Voids in Hydrogen Embrittlement: Andrew Lee1; Abhinav Parakh1; Wendy Gu1; 1Stanford University
    Hydrogen embrittlement of steel transmission pipelines remains a barrier to widespread adoption of hydrogen as a carbon-neutral energy source. Despite nearly a century of research, a connection between atomic scale embrittlement mechanisms and macroscale material behavior has eluded the field. In this work, we use in-situ transmission x-ray microscopy, digital image correlation, and micromechanical testing to connect microstructural differences to fracture behavior in iron and nickel thin-films exposed to hydrogen environments. We systematically examine the effect of grain size and hydrogen concentration on surface and sub-surface void distributions, strain-field development, and mechanical properties. While free hydrogen in the lattice inhibits formation of micron-sized voids across all samples and causes strain localization, smaller grain sizes and increase in density of hydrogen trap sites enhances the role of trapped hydrogen in fracture. This discontinuous transition in void distribution implies a change in mechanistic embrittlement regimes with changing microstructure.

4:10 PM  
Growing Voids and Migrating Twins: Shailendra Joshi1; 1University of Houston
     Ductile failure is a multi-scale phenomenon. In metals, atomic deformation mechanisms interact with micromechanical defects such as voids. Inter-void interactions lead to mesoscopic damage zones. Finally, the interaction of damage zones with component scale causes a macroscopic fracture. Coupling between these scales is complicated by the anisotropic nature of plasticity. We present the deformation stability and failure of nanotwinned materials whose grain-scale anisotropy is brought about by size effects associated with fine-scale growth twins. Using a length-scale dependent crystal plasticity finite element framework, we investigate the role of twin boundary mediated microstructural evolution in the damage due to nano-void evolution. The interaction between the rates of twin boundary migration and void growth is discussed from the vantage point of macroscopic deformation stability. While the investigation pertains to nanotwinned materials, the observations and analysis may be relevant to analogous situations in multi-layered materials with moving interfaces.

4:30 PM  
Examining Hot Corrosion Crack Tip Arrest through Advanced Microscopy Analysis of Ni-superalloy CMSX-4: Maadhav Kothari1; Andy Holwell1; Hrishikesh Bale1; Simon Gray2; Jonathan Leggett3; 1Carl Zeiss Microscopy Llc; 2Cranfield University; 3Rolls Royce
    Single crystal Ni superalloys are typically are used in power generation and aviation applications due to their unique properties. Recently, incidents of failure due increased temperature around root blade regions has caused Type II hot corrosion leading to cracking in blade roots resulting in catastrophic failure. Understanding the failure mechanism and crack characterisation is vital in solving this industrial issue. Here we demonstrate a unique workflow of characterization using micro computer tomography, FIB-SEM and laser lamellar preparation in order to characterize crack tips and crack stress. By extracting the fracture tip, both crystal plasticity and crystal deformity can be studied in detail resulting in orientation tomography of the corroded region of stress. Combining this correlative workflow we are able to demonstrate a unique technique in c-ring analysis and identifying structural defects not visible using typical microscopy techniques.

4:50 PM  Invited
Similarity of Microscopic Strain Localization in Very Different Microstructures: C. Tasan1; Krista Biggs1; Onur Guvenc1; Jiyun Kang1; Hyun Oh1; Shaolou Wei1; 1Massachusetts Institute of Technology
    Microscopic strain localization is a key process determining various mechanical properties of metallic materials, including formability. In this study, we compare the microscopic strain localization patterns of various single-phase and multi-phase alloys with very different matrix crystal structures (fcc, bct, hcp, bcc+hcp, etc.), textures, grain sizes, and properties. We observe that the strain localization patterns are interestingly similar regardless of these variations in crystal structure and properties. This observation supports the recent proposal that the statistical distribution of local strain in various steels follows a universal law, i.e., a lognormal distribution. It also enables the use of a simple skewness parameter to quantitatively describe the heterogeneity of strain localization.