General Poster Session: Characterization
Program Organizers: TMS Administration

Tuesday 5:30 PM
February 25, 2020
Room: Sails Pavilion
Location: San Diego Convention Ctr


K-138: Automated Reconstruction of Spherical Kikuchi Maps: Chaoyi Zhu1; Kevin Kaufmann1; Kenneth Vecchio1; 1University of California, San Diego
    Electron backscatter diffraction (EBSD) is a surface characterization technique, based in the scanning electron microscope, to extract location specific crystallographic orientation information from crystalline materials. Conventional setup of the EBSD involves analysis of Kikuchi patterns that are gnomonically projected onto a flat phosphor screen. We report in this study a fully automated method to recover the spherical Kikuchi map from experimental Kikuchi patterns. First, experimental patterns are filtered based on the pattern quality, relative misorientation and cross-correlation coefficient with simulated patterns. Next, inverse gnomonic projection can be implemented to transform the collected pattern in the gnomonic projection frame to the detector frame before rotating it into the correct orientation in the Cartesian crystal frame (Figure). This method potentially enables more accurate orientation determination, new pattern center refinement method, and EBSD based phase identification.

K-140 In-situ Measurement of Thin Film Moduli and Yield Stress via Confined Compression: Owen Brazil1; 1Texas A&M
    The measurement of thin film properties free from substrate influence remains one of the outstanding challenges in nanomechanics. Here we introduce a technique based on indentation of a supported film with a flat punch whose diameter is many times the initial film thickness. This geometry generates a state of confined uniaxial strain for material beneath the punch, allowing direct access to intrinsic stress versus strain response. For simple elastic – plastic materials this enables material parameters such as elastic modulus, bulk modulus, Poisson’s ratio, and yield stress to be simultaneously determined from a single loading curve. This confined plastic yield phenomenon has not been previously observed in thin films or homogeneous materials. We demonstrate this technique for 190 – 470 nm polystyrene films as well as PMMA and amorphous Selenium films on silicon.

K-141: Investigation of Strain Rate Sensitivity with Novel High Strain Rate Nanoindentation: Christopher Walker1; George Pharr1; 1Texas A&M University
    Efficient studies of strain-rate dependency can be conducted with nanoindentation but are limited by data acquisition rates (DAQs) and electronic time constants. At high strain rates, DAQs under 1 kHz provide few usable data points for analysis. Current loading time constants prevent ultra-high strain rate testing as the applied load is difficult to determine when moving faster than the time constant. Pairing electromagnetic forces with laser-guided displacement readings will be used to improve the possible data acquisition rate from 100 kHz to as high as 5 MHz. Using the laser’s control system to bypass the slow USB control process for the electromagnetic coil will lower the associated time constant to near-instantaneous application. Ultra-high strain rate sensitivities will be measured in various materials including single crystals, multi-phase materials, and non-equilibrium vapor-deposited thin films. Results of these experiments will provide further experimental input for simulations and models for strain rate sensitivity.

Cancelled
K-143: The Effects of Aging on Mechanical Properties on Ni-base Superalloy Casting Alloys for A-USC Power Generation Application: Jaihyun Park1; Jieun Kim1; Kyongwoon Lee2; Keeyoung Lee3; 1RIST; 2DOOSAN; 3KPCM
    Nickel based super alloys are candidate material for the gas turbine parts for Hyper Super Critical (HSC) power plants that use steam temperature above 700°C because of their high tensile strength, creep strength, and outstanding corrosion resistance in high temperatures. The HSC power generation material is exposed to high temperature heat for a long time, it is necessary to observe the change in mechanical properties by heat exposure for a long time. In this study, the nickel based superalloy Alloy 625 was used to analyze the mechanical properties through mechanical tests such as tensile tests(room and high temperature) and hardness tests before and after long- term heat treatment at 700°C. In addition, The changes in microstructure were analyzed by Optical Microscope, Scanning Electron Microscope and Transmission Electron Microscope

K-144: Wear Characteristics of Aluminum-quartz-barite Composites: Emmanuel Akpan1; Torti Uwaike2; Oluwashina Gbenebor2; Oluwaseyi Taiwo2; Samson Adeosun2; Samuel Olaleye2; 1Institut fur Verbundwerkstoffe ; 2University of Lagos
    In this experimental study, quartz, barite and quartz/barite reinforced AA6063 Aluminium Alloy were produced using double stir casting method. Reinforcements were added in particulates form (5, 10, 15, 20 and 25 wt. %) to the aluminium matrix. Wear, microstructural, and mechanical characterizations were carried out. Results show that mechanical properties of the composites were enhanced by the reinforcement. The wear rate was found to decrease with increase in weight fraction of the reinforcement in all cases. Coefficient of friction of composites ranges between 0.32 – 0.56 while thermal conductivity lies between 0.082 – 0.252 W/mK. AA6063/quartz-barite composites show superior wear, mechanical and thermal properties to current used brake pad materials in utility vehicles.