Mechanical Response of Materials Investigated Through Novel In-Situ Experiments and Modeling: Session VI
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, Microstructure Engineering; 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

Thursday 8:30 AM
March 3, 2022
Room: 206B
Location: Anaheim Convention Center

Session Chair: Ankit Srivastava, Texas A&M University; Isabel Crystal, Lawrence Livermore National Laboratory

8:30 AM  
In-situ SEM Investigation of Thermally Induced Cracking in Shape Memory Ceramics: Isabel Crystal1; Haoxue Yan2; Christopher Schuh2; 1Lawrence Livermore National Laboratory; 2Massachusetts Institute of Technology
    Transformation induced cracking is considered the main limitation in translating shape memory ceramics (SMCs) to bulk form. It is thought that micro-cracks nucleate at the tips of the martensitic plates. Here we employ a custom heating stage within an SEM to collect in-situ videos of bulk polycrystalline SMCs undergoing cyclic transformation. The videos show that cracks open and propagate on the cooling portion of the cycle, during the forward martensitic transformation from the austenite to martensite phase. Smaller grains are found to contain a single variant of martensite while larger grains have complex multi-variant structures that evolve with cycling. The above observations are in line with calorimetry experiments collected during cyclic martensitic transformations. An additional grain pop-out phenomenon is noted on the reverse transformation for which the closing of the crack causes grains along the crack to eject from the surface.

8:50 AM  
Determination of Fracture Toughness Using the Compression Fracture Technique: Carl Cady1; Cheng Liu1; 1Los Alamos National Laboratory
    Many engineering materials of importance can be mechanically characterized as brittle or quasi-brittle solids. A technique has been developed for observing and studying the process of macroscopic crack initiation and propagation using digital image correlation (DIC), and using linear elastic fracture mechanics (LEFM), determination of fracture toughness has been made. Specimen design, loading configuration, and diagnostics for identifying crack initiation and location, and scheme for extracting the stress intensity factor at the moving crack tip will be described. An interesting characteristic of this techniques is that it can be applied to the characterization of materials as a function of loading rate with the only limitation on its application being the resolution and rate at which images can be captured. It is known that the crack speed is a material characteristic that is associated loading rate and fracture toughness. This investigation will also show the relationship between loading rate and fracture.

9:10 AM  
X-ray Microbeam Characterization of Electromigration Process in Al(0.25wt% Cu) Interconnect: Ping-Chuan Wang1; Kieran Cavanagh1; 1SUNY New Paltz
    Various x-ray microbeam techniques have been developed around 20 years ago to provide fundamental understanding of electromigration (EM) mechanisms in Al- and Cu-based interconnects. For solid solution based interconnects, such as Al with Cu impurity added for reliability purpose, interaction between solvent and solute during EM process significantly complicates the resulting stress/strain distribution. This was directly measured for the first time using x-ray microdiffraction by Cargill’s group at Lehigh University in 2003. Around the same time, the x-ray micro-topography technique was developed, providing high strain sensitivity to allow finer observation of local stress evolution during early stages of EM process. In this presentation, we will revisit the micro-topography technique in achieving real-time simultaneous measurement of EM-induced stress and Cu distribution in Al(Cu) interconnects. New insight yielded from recent data analyses will be discussed, along with numerical modeling, to further explore the role of Cu solute in retarding Al electromigration.

9:30 AM  
Achieving the Maximum Modulus of Resilience in Polymer Nanocomposites via Sequential Infiltration of Metal Oxides: Zhongyuan Li1; Nikhil Tiwale2; Ashwanth Subramanian2; Ying Li1; Chang-Yong Nam2; Seok-Woo Lee1; 1University of Connecticut; 2Brookhaven National Laboratory
    Engineering the modulus of resilience, the material’s maximum ability to store the elastic strain energy, has been challenging because it requires the asymmetric increase in yield strength and Young’s modulus against their mutual scaling behavior. To overcome this issue, we developed organic–inorganic nanocomposites by utilizing Al2O3 and ZnO infiltration into SU-8 polymer nanopillars. The in-situ nanomechanical measurements revealed a metal-like high yield strength (∼400 MPa) with an unusually low, foam-like Young’s modulus (∼3 GPa), which yields an ultrahigh modulus of resilience (∼26 MJ/m3), surpassing those of most engineering materials. We also developed the interphase composite model that captures the effects of nanoscale oxide on the mechanical properties and confirmed that our experimental data are close to the theoretical limit of modulus of resilience. Our results suggest that the sequential infiltration synthesis is the effective synthesis method for developing a polymer nanocomposite with an enhanced modulus of resilience.

9:50 AM Break

10:10 AM  
Characterization of the Role of Lath Boundaries in Lath Martensitic Steel Using In-situ Micro-pillar Compression Tests: Ye-Eun Na1; Hadi Ghaffarian1; Dongchan Jang1; 1KAIST
    Reduced-activation ferritic/martensitic (RAFM) steel is one of promising candidate materials for structural components of future nuclear energy systems. It is a type of lath martensite having hierarchical microstructure following Kurdjumov-Sachs orientation relationship. To fully understand mechanical behavior of lath martensitic steels, it is important to find out the role of each microstructural features. Until now, several studies have been done focusing on packet and block boundaries, i.e., high-angle grain boundaries (GBs). However, no in-depth study has been conducted on lath boundary, the most abundant feature in lath martensite. It is a low-angle GB known to consist of a periodic array of dislocations so it is expected to show different behaviors from other high-angle GBs. In this study, we made micro-pillars containing lath boundaries and performed in-situ compression tests accompanied by post-mortem SEM and TEM analysis. And we observed GB sliding along lath boundaries rather than lattice slip following Schmid’s law.

10:30 AM  
Super-fast Fabrication of Micropillar Arrays Using Laser FIB Combination for More Statistically Relevant Micropillar Compression Tests: Fang Zhou1; Tobias Volkenandt1; Tim Schubert2; Nicholas Randall3; Timo Bernthaler2; 1Carl Zeiss Microscopy GmbH; 2Aalen University; 3Alemnis AG
    Micropillar compression tests are widely used to probe the uniaxial stress-strain response of materials such as metals and alloys. Micropillar arrays and pillars with various sizes are fabricated to have more statistically relevant testing. Conventionally micropillars are machined using FIB which is extremely time-consuming, and an irradiation-damaged layer is created by Ga implantation. Thus, fabrication of good quality micropillar arrays with great control over the size and location on a large test volume is so far hardly possible. In this work, an all-in-one LaserFIB solution is introduced to speed up the fabrication of micropillar arrays. A femtosecond laser is used to fabricate micropillar arrays over an area of hundreds of microns up to centimeters within minutes. Achievable pillar diameters are in the order of 50 microns. The machined micropillar arrays are deformed with a flat punch indenter to measure the individual stress-strain curves in a SEM.

10:50 AM  
In Situ Observation of Room Temperature Crack-healing in an Atomically Layered Ternary Carbide: Hemant Rathod1; Thierry Ouisse2; Miladin Radovic1; Ankit Srivastava1; 1Texas A&M University; 2Université Grenoble Alpes
    Ceramic materials provide outstanding chemical and structural stability at high temperatures and in hostile environments but are susceptible to catastrophic fracture that severely limits their applicability. Herein, via in situ scanning electron microscope indentation of carefully grown single crystals of a ternary carbide using an in-house designed and build fixture, we demonstrate an intriguing possibility of healing the cracks as they form, even at room temperature. Crystals of this class of ceramic materials readily fracture along weakly bonded crystallographic planes. However, our results show that onset of an abstruse mode of deformation referred to as kinking in these materials induces large crystallographic rotations and plastic deformation that physically heal the cracks.