Advanced Thermo-mechanical Characterization of Materials with Special Emphasis on In Situ Techniques: In Situ Techniques II
Sponsored by: TMS Structural Materials Division, TMS: Advanced Characterization, Testing, and Simulation Committee, TMS: Nanomechanical Materials Behavior Committee, TMS: Thin Films and Interfaces Committee
Program Organizers: Amit Pandey, LG Fuel Cell Systems Inc.; Sanjit Bhowmick, Hysitron; Jeff Wheeler, ETH Zurich; María Teresa Pérez Prado, IMDEA Materials Institute; Robert Wheeler, MicroTesting Solutions LLC; Josh Kacher, Georgia Tech

Monday 2:00 PM
February 27, 2017
Room: 32A
Location: San Diego Convention Ctr

Session Chair: Robert Wheeler, MicroTesting Solutions LLC; Amit Pandey, LG Fuel Cell Systems

2:00 PM  Invited
Advanced In Situ Loading Environments for High Energy Synchrotron X-ray Experiments: Paul Shade1; Basil Blank2; Jay Schuren1; Joel Bernier3; Darren Pagan3; David Menasche4; Robert Suter4; Armand Beaudoin5; Peter Kenesei6; Jun-Sang Park6; Jonathan Almer6; Darren Dale7; Peter Ko7; Todd Turner1; 1Air Force Research Laboratory; 2PulseRay; 3Lawrence Livermore National Laboratory; 4Carnegie Mellon University; 5University of Illinois at Urbana Champaign; 6Argonne National Laboratory; 7Cornell University
    High energy x-ray characterization methods hold great potential for gaining insight into the behavior of materials and providing comparison datasets for the validation and development of mesoscale modeling tools. A suite of techniques have been developed by the x-ray community for characterizing the 3D structure and micromechanical state of polycrystalline materials; however, combining these techniques with in situ mechanical testing under well characterized and controlled boundary conditions has been challenging due to experimental design requirements. In this presentation, we describe advanced sample loading and heating environments that have been developed for in situ high energy synchrotron x-ray experiments. Example datasets that were collected utilizing this hardware will be described.

2:25 PM  
Unveiling the Micromechanical Response of Mg Alloys by EBSD-assisted Slip Trace Analysis: Carmen M. Cepeda-Jiménez1; María Teresa Pérez Prado1; 1IMDEA Materials Institute
    EBSD-assisted slip trace analysis is utilized to determine qualitatively the relative activities of basal, prismatic and pyramidal systems in a Mg rare earth alloy in different states of precipitation following tensile and compression deformation to a given strain level at ambient temperature and high temperature and quasi-static rates. The incidence of the different systems is then related to the alloy grain size, texture, and precipitation state. Finally, the macromechanical behavior of the AZ91 alloy and, in particular, the strength, the ductility and the yield stress asymmetry are rationalized based on the measured slip activities.

2:45 PM  
Development of a High Temperature Tensile Tester for Micromechanical Characterization of Materials Supporting Meso-Scale ICME Models: Zafir Alam1; David Eastman1; Minjea Jo1; Kevin Hemker1; 1Johns Hopkins University
    A high temperature tensile tester (HTTT) has been developed for the evaluation of micro-mechanical properties of materials at the meso-scale. This system allows for testing of metals and ceramics at temperatures and strain rates between room temperature an 1200 C and 10^-5 and 10^-1 s-1, respectively. The samples are heated in a compact clamshell furnace and strain is measured directly in the sample gage through digital image correlation. The HTTT extracts representative mechanical properties, as evidenced by the similarity in the evaluated micro-tensile properties of a Ni-base superalloy Ni-625 with that of the bulk response. The effectiveness of the HTTT has also been demonstrated in evaluating the tensile and stress relaxation/short-term creep properties of a polycrystalline Ni-base superalloy René 88DT. The versatility in carrying out tensile, short-term creep, bend tests, and fracture toughness measurements makes the HTTT a robust experimental tool for scale specific benchmarking of multi-scale ICME models.

3:05 PM  Invited
In Situ Micro-mechanical Testing of Ion Irradiated Materials: Dhriti Bhattacharyya1; Alan Xu1; Lyndon Edwards1; 1ANSTO
    The mechanical testing of materials in small volumes, such as those encountered in thin ion- irradiated layers, is of particular interest when this is the only method for assessing the properties of the volume of interest. In situ micro-mechanical testing of these materials inside a scanning electron microscope provides a novel way of imaging the deformation processes during the test and correlating them with the corresponding stress-strain conditions. Here we present the results of quasi-static and strain-rate dependent tests on 12 μm thick single crystal Ni films irradiated with He2+ ions. The effect of orientation on the measured properties is also investigated. Further analysis was performed using the transmission electron microscope to examine samples extracted from the post-test specimens using the focused ion beam. These tests provide valuable insight into the deformation behaviour of ion-irradiated materials and indicate a pathway to developing methodologies for scaling these results to bulk properties.

3:30 PM Break

3:50 PM  
Grain Growth and Mechanical Behavior of Nanostructured Intermetallic Films Studied Using In Situ TEM Annealing and Tensile Straining: Rohit Sarkar1; Jagannathan Rajagopalan1; 1Arizona State University
    The microstructure and mechanical properties of intermetallic films are intimately related and understanding this relationship is critical to elucidate their deformation behavior. We employed in situ TEM annealing and MEMS based tensile straining to uncover the structure-property relationships in intermetallic films. Amorphous thin films of NiTi and TiAl having thin crystalline seed layers of Ti were deposited by sputtering. In situ TEM annealing was carried out to study the effects of the seed layer on the crystallization kinetics and grain growth behavior of the films. The seed layers were found to curtail grain growth and facilitate the development of nanostructured thin films. Using the insights from the in situ annealing experiments, seed layer parameters were varied to control the size, aspect ratio and distribution of the grains. In situ TEM straining showed significant variation in the deformation behavior of films synthesized with different seed layer parameters.

4:10 PM  
Crystal Size and Temperature Effects on the Transformation in Deformation Modes in Twin Oriented Mg Single Crystals: Gi-Dong Sim1; Kelvin Xie1; Kevin Hemker1; Jaafar El-Awady1; 1Johns Hopkins University
    We present a comprehensive study to understand crystal size and temperature effects on the transformation in deformation modes in twin oriented Mg single crystals. Single crystal micropillars with size ranging from 2 to 23 μm were fabricated, then tested by in-situ SEM nanoindentation. First, we discuss crystal size effect on the transformation of deformation mechanisms at room temperature. The experiments reveal two regimes of size effects: (1) single twin propagation, where a typical “smaller the stronger” behavior was dominant in pillars ≤ 18 μm in diameter, and (2) twin-twin interaction, which results in anomalous strain hardening in pillars > 18 μm. In the second part, we report temperature effect (room temperature, 100oC, and 150oC) on the deformation mechanism at a fixed crystal size (6 μm). Unusually high flow stress was observed at 100oC while twinning still governs plasticity. Surprisingly, at 150oC, we observed strain softening due to dislocation-mediated plasticity.

4:30 PM  Invited
In Situ Characterization of Electromigration and Thermal Cycling Damage and Grain Growth in Cu/Pure Sn/Cu Solder Joints: Antony Kirubanandham1; Nikhilesh Chawla1; 1Arizona State University
    Electromigration and thermal cycling damage evolution was studied in situ in a scanning electron microscope (SEM) on Cu/Sn/Cu solder joints. The evolution of Sn grain structure was also analyzed in situ using Electron Backscatter Diffraction (EBSD). To isolate the influence of atmosphere, experiments were done both ex situ and in situ in an SEM. Similarly, to isolate the influences of electrical and thermal components on observed electromigration damage, several thermal aging and current stressing experiments were done in both interrupted and un-interrupted conditions. In situ thermal cycling was conducted between 25oC and 150oC to accelerate the damage mechanisms during interrupted thermal aging tests and study the long term thermal and mechanical stability. The contribution of each component on observed damage features such as grain boundary ledges, intermetallic delamination and fracture, and Sn grain growth will be elucidated.

4:55 PM  Invited
Plasticity of Nano-Sized Metallic Glasses: Dongchan Jang1; 1Korea Advanced Institute of Science and Technology
    Understanding of plasticity, especially in relation to the shear transformation zones (STZs) and macroscopic deformation modes, has been one of the most important topics for the metallic glasses in the past decades. In this presentation, we will introduce our recent experimental results for the strength and ductility of Zr-based metallic glasses as a function of the extrinsic size of the specimen at the nanoscale, fabricated by various techniques including the focused ion beam (FIB) milling and electroplating on the patterned templates. In addition, to decouple the pure sample size effect and ion irradiation which is the common artifact from the nano-sample fabrication using FIB, we irradiated a sample with protons and compared its mechanical propperties with un-irradiated one. The experimental results were corroborated by the molecular dynamic simulation to fully understand the atomic level mechanisms of the irradiation effects and mechanical behavior in the metallic glasses.

5:20 PM  
In-situ Experiments Combining SEM and X-ray Computed Tomography: Torin Quick1; Nathan Sesar2; Robert Wheeler3; 1Air Force Research Laboratory; 2Southwestern Ohio Center for Higher Education; 3MicroTesting Solutions LLC
    An experimental study is carried out to characterize the failure behavior of a fiber reinforced polymer matrix composite at the micro-scale using in-situ testing. Micron-sized specimens of IM7/BMI composite were fabricated using Focused Ion Beam milling. The specimens were compression tested using a custom built, SEM/X-ray CT-based in-situ micro-testing fixture. During compression, SEM images are acquired continuously between displacement intervals so the deformation phenomena can be observed. The in-situ fixture was also used to reload the sample in an X-Ray CT machine. Intermediate resolution x-ray CT data was acquired both in loaded and unloaded states to fully resolve the deformation in 3D. Furthermore; high-resolution CT scans taken of the standalone sample allowed an exact mapping of the fiber locations that was then overlaid with the lower resolution CT data to allow for higher accuracy volumetric feature tracking during in-situ testing.