2016 Materials Science Abstracts

Poster Number: MSE-01

Title: In situ Study of Defect Accumulation in Ti-6Al-4V Under Heavy Ion Irradiation: Influence of the Microstructure

Authors: Aida Amroussia; Carl J. Boehlert; Frederique Pellemoine

Abstract: Due to their high specific strength, good fatigue and creep properties, corrosion resistance and their commercial availability, titanium alloys have been widely used in industrial, aerospace and biomedical applications. Ti-alloys are also extremely attractive for nuclear applications, being highly compatible with coolants (lithium, helium, water) and exhibiting low activation in radioactive environments. Ti-6Al-4V is considered as a structural material for the beam dump drum for the Facility for Rare Isotope Beams. The traditional manufacturing of titanium parts can be difficult, time consuming and have high material wastage and manufacturing costs. Additive manufacturing such as Direct Metal Laser Sintering presents an attractive alternative due to its capability to produce near net shape components with less production time and material waste. Successful prediction of the material’s performance overtime and under irradiation requires an understanding of the basic formation mechanisms of radiation-induced defects at initial damage stages at lower doses and its accumulation at higher dose levels which results in the complex features in the microstructure. A unique in-situ TEM irradiation study was performed at the IVEM-Tandem Facility at Argonne National Laboratory. Three different Ti-6Al-4V samples (Powder metallurgy (PM) rolled , as received (DMLS) and DMLS then followed by Hot Isostatic Pressing (HIP)) were irradiated with 1 MeV Kr2+ at 350ºC. The fluence was up to 1016 ions.cm-2, equivalent to a dose of 24 dpa. In all irradiated samples, we observed the accumulation overtime of fine nanometer size black spots indicative of defects formed due to irradiation damage. A preliminary analysis of the results will be presented.

This work was supported in part by This work was partially supported by the U.S. Department of Energy, Office of Science under Cooperative Agreement DE-SC0000661. This work was also supported by Michigan State University under the Strategic Partnership Grant “FRIB - Materials in Extreme En

 

Poster Number: MSE-02

Title: Carbon Fiber Polymer Matrix Composites Modified with Cellulose Nanowhiskers

Authors: Mariana D. R. Batista; Lawrence T. Drzal

Abstract: Lightweight, high-strength and high-stiffness are often identified as desirable properties for aerospace and automotive applications. In order to achieve these engineering needs and meet the growing government requirement for fuel economy, carbon fiber reinforced polymer (CFRP) composites have gained attention because of their high strength-to-weight ratio. The global CFRP market is projected to reach USD 35.75 billion by 2020. However, one drawback of CFRP, typically epoxy-based CFRP, is its brittle fracture mechanism, which reveals low level of adhesion between the carbon fiber and the polymeric matrix. Therefore, to achieve good mechanical properties and resist crack propagation, a well-bonded interface is required. Cellulose nanowhiskers (CNWs) have attracted considerable attention due to their high mechanical properties, low cost, low density and sustainable nature. In this work, we developed a process to coat carbon fiber with CNWs where they would function as a nano-reinforcement to improve the adhesion between the carbon fiber and the epoxy matrix. CNWs were applied as part of a sizing agent to improve the stress transfer at the fiber-matrix interface. Scanning electron microscope (SEM) micrographs showed that CNWs uniformly coated the carbon fibers. Moreover, single fiber fragmentation specimens were fabricated to evaluate the interfacial shear strength of the CNW sized carbon fibers in the epoxy matrix with increasing CNW content. This research on modification of the fiber-matrix interface has the potential to improve the mechanical properties of these carbon fiber-epoxy composites and be utilized for interfacial optimization in biobased natural fiber composites as well.

This work was supported in part by CAPES Foundation (BEX:13655-13-2)

 

Poster Number: MSE-03

Title: The Effects of Vacancy Substitution on CuGaTe2 for Thermoelectric Applications

Authors: Winston D. Carr; Donald T. Morelli

Abstract: Thermoelectric generators offer the ability to convert waste heat directly into electricity through solid state processes. This has the advantage of requiring no moving parts and of being highly scalable, which are both important features for commercial applications. However, the wide spread use of thermoelectric generators has been limited by low device efficiency and dependence on toxic or rare elements such as lead and tellurium. The performance of a thermoelectric material is characterized by the dimensionless figure of merit, ZT, which depends on three inter-related material properties: the electrical conductivity, the thermal conductivity, and the thermopower, also known as the Seebeck coefficient. A high ZT requires a large electrical conductivity and a low thermal conductivity, an atypical combination. The following work is on the progress of optimizing the thermoelectric material CuGaTe2 through co-substitution of zinc atoms and vacancies on the copper atomic site. This approach offers a path to optimize both the thermal and electrical conductivity at the same time. By substituting both divalent zinc and vacancies for monovalent copper the total average valance can be maintained, which should keep electrical properties relatively unchanged, however the difference in mass of copper and zinc, as well as the vacancy sites, further scatters heat carrying phonons and lowers overall thermal conductivity.

This work was supported in part by This work was supported as part of the “Revolutionary Materials for Solid State Energy Conversion,” an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences under Award # DE-SC0001054.

 

Poster Number: MSE-04

Title: Unique Twinning in Orchestrated Deformation Mechanisms to Stiffen and Toughen Nacre Under Impacts

Authors: Jialin Liu; Zaiwang Huang; Xiaodong Li; Yue Qi

Abstract: It has long been identified that nacre, natural body armor, has prominent mechanical properties such as high strength and eminent toughness. What’s more, under dynamic strain rate (~103 s-1), both strength and elongation to break are significantly increased comparing with quasi-static strain rate (~10-3 s-1). Currently, stiffen and toughen behavior under impact is attributed to nacre’s hierarchical macroscopic structures which lead to highly coordinated deformation mechanisms. However, the atomic origin of nacre’s high impact toughening behavior remains ambiguous. Recently, the unique deformation twinning observed in dynamic uniaxial compression tests provided new understandings on atomic deformation mechanisms. to further explain the underlying mechanisms, Ab initial calculation is carried out using density function theory (DFT) and nudge elastic band (NEB) method based on experiment observation to calculate generalized stacking fault energy (GSFE) and fracture energy. The atomic structure relaxation process are analyzed with details. The results showed nacre have an extraordinary large unstable stacking fault energy (USFE) to SFE ratio. Under high strain rate, this large ratio allow deformation twinning provide extra toughness while other mechanisms are “frozen” and biopolymers are stiff. Comparing with other materials, this unique properties are originated from its specific lattice parameter and sliding distance relationship, ionic bonding nature and large number of neighbors.

 

Poster Number: MSE-05

Title: Influence of Novel Chemical Modifier Addition on the Solidification Kinetics of Aluminum-Silicon Alloys

Authors: Yang Lu; Andre Lee

Abstract: Microstructures and solidification kinetics of nearly eutectic, Al-12wt%Si (A4047), casting alloys modified with trisilanol phenyl polyhedral oligomeric silsesquioxanes (TSP) were investigated. Optical microscopy was used to examine the microstructure of ingots made from A4047 powders with and without TSP treatment. It was found the incorporation of TSP reduced the secondary dendrite arm spacing of primary Al phase, and modified the morphology of eutectic Si from flaky to fibrous form. Solidification of alloys was examined to further understand the observed changes in microstructure. Both undercooling and eutectic growth temperature were depressed with TSP incorporation. In addition, the thermal analysis of the A4047 ingots with different amount of TSP, which were obtained by sequentially diluting TSP-treated with untreated samples, showed that these changes of undercooling and eutectic growth temperature were dependent on the TSP content. Based on the observed reduced undercooling and eutectic temperature with TSP incorporation, and the refinement of primary Al and a flaky-fibrous transition in the eutectic Si morphology, it is proposed that nano-sized cage structure of TSP served as heterogeneous nucleation sites to refine primary Al and modify eutectic Si.

 

Poster Number: MSE-06

Title: Oxygen Surface Exchange Curvature Relaxation Measurements Performed with Diffusion Barrier Layers

Authors: Yuxi Ma; Jason Nicholas

Abstract: The Curvature Relaxation (KR) technique is a new, in situ, electrode-free method used to measure the chemical oxygen surface exchange coefficient (kchem) of dense or porous, thin or thick film samples. Typically, the KR technique determines kchem by fitting a solution of Fick’s 2nd Law to the curvature response of mechano-chemically active film | inert substrate bilayers reacting to sudden oxygen partial pressure changes. Unfortunately, undesirable chemical reactions between the film and substrate can occur during film fabrication and/or measurement at high temperature. The resulting impurities and/or secondary phases can unexpectedly alter the measured kchem and stress levels. The object of this work was to accurately measure the oxygen surface exchange coefficient of praseodymium doped ceria (PCO) by utilizing gadolinium doped ceria (GDC) barrier layers to prevent interdiffusion between PCO and 9.5 mole % yttria stabilized zirconia (YSZ) substrates. to achieve this, a PCO|GDC|YSZ multilayer sample was prepared by 1) sputtering GDC on (100) oriented single crystal YSZ substrates, 2) sintering the resulting GDC|YSZ bilayers at 650oC for 1 hour to crystallize the sputtered GDC, 3) sputtering PCO on the sintered GDC|YSZ bilayers, and 4) sintering the resulting PCO|GDC|YSZ trilayers at 725oC to crystallize the sputtered PCO. The PCO|GDC|YSZ samples were then KR tested from 300 to 600oC by rapidly switching the surrounding atmosphere from synthetic air (21% O2-79% Ar) to a 10% synthetic air-90% Ar mixture. After KR measurements, scanning electron microscopy and/or ellipsometry were used to determine the thickness of each layer. X-ray Photoelectron Spectroscopy and X-ray Diffraction measurements were also performed to examine the PCO surface chemistry and bulk crystal structure.

This work was supported in part by This material is based upon work supported by the Department of Energy under Award Number DE-FE0023315

 

Poster Number: MSE-07

Title: Hydroforming of a Large Grain Niobium Tube

Authors: Aboozar Mapar; Thomas R. Bieler; Farhang Pourboghrat

Abstract: Currently most of Niobium (Nb) cavities are manufactured from fine grain Nb sheets. As-cast ingots go through a series of steps including forging, milling, rolling, and intermediate annealing, before they are deep-drawn into a half-cell shape and subsequently electron beam welded to make a full cavity. Tube hydroforming, a manufacturing technique where a tube is deformed into a die using a pressurized fluid, is an alternative to the current costly manufacturing process. A whole cavity can be made from a tube using tube hydroforming. This study focuses on deformation of large grain Nb tubes during hydroforming. The crystal orientation of the grains is recorded. The tube is marked with a circle-grid which is used to measure the strain after deformation. The deformation of the tube is modeled with crystal plasticity finite element. The results of the simulation and experiments are compared.

 

Poster Number: MSE-08

Title: Microstructure and Mechanical Behavior of High Pressure torsion Al 2139-T8 Alloy

Authors: Uchechi Okeke; Hakan Yilmazer; Huihong Liu; Niinomi Mitsuo; Carl Boehlert

Abstract: Al 2139-T8 is a Cu based alloy which also contains Mg and Ag elements.  The alloy previously underwent a T8 temper process which consists of solutionizing, cold working, and artificial ageing.  This temper yields an ultimate tensile strength (UTS) of 430MPa and a strain-to-failure (ef) of 7.2%.  High pressure torsion (HPT) is another processing technique that uses severe plastic deformation to refine the microstructure to submicron dimensions which leads to superplasticity and increased strength.  In order to provide an objective analysis, the Al 2139-T8 was annealed at 460°C for one hour to remove the T8 tempering.  HPT was performed at room temperature on the annealed Al 2139-T8.  Samples were discs with a diameter of 20mm and a thickness ranging from 0.85-0.9mm.  HPT was performed using revolutions of N=1, 2, 4, and 8 at 0.2RPM.  A pressure of 5 GPa was applied to the anvil.  High resolution scanning electron microscopy and electron backscattered diffraction revealed that all of the revolutions yielded submicron grains.  Additionally, with each revolution, the precipitates were increasingly fractionated.  At N=8, there was noticeable grain growth and the fractioning of the precipitates was the highest.  Vickers hardness acquired from the center of the discs towards the full radius did not reveal a significant difference in hardness between the revolutions.  Tensile tests revealed that HPT increased the UTS up to 900MPa. 

This work was supported in part by 2015 NSF East Asia and Pacific Summer Institute Award, NSF Division of Materials Research (Grant # DMR1107117)

 

Poster Number: MSE-09

Title: Enhanced Thermoelectric Efficiency of Ball Milled PtSb2 by Sn Doping

Authors: Spencer Waldrop; Donald Morelli

Abstract: Many future and next-generation products will require not only passive heat dissipation, but active cooling to attain their required performance. Thermoelectric cooling modules will play an integral role in this due to their solid state nature which allows for their adoption in applications where large, vibrating, mechanically clunky coolers are not well suited. Utilizing PtSb2 in these modules for cooling below room temperature requires a reduction of thermal conductivity by ball milling to enhance the thermoelectric efficiency. Further enhancement of ball milled PtSb2 can be found by increasing the electrical conductivity and Seebeck coefficient by Sn doping. Samples with composition PtSb2-xSnx x= 0, 0.005, 0.01, 0.02, 0.04, and 0.08 were studied. A slight increase in Seebeck coefficient, decrease in electrical resistivity, and decrease in thermal conductivity were found with increasing concentrations of Sn. This resulted in a large increase in efficiency at room temperature with modest increases at low temperatures.

This work was supported in part by Air Force Office of Scientific Research under the Multi-University Research Initiative (MURI), “Cryogenic Peltier Cooling,” Contract No. FA9550-10-1-0533

 

Poster Number: MSE-10

Title: Introduction of Precisely Controlled Microstructural Defects into SRF Cavity Nb Sheet and their Impact on Local Superconducting Properties

Authors: Mingmin Wang; Di Kang; Zuhawn Sung; Peter Lee; Anatoli Polyanskii; Christopher Compton; Thomas Bieler

Abstract: Formation of SRF cavity from Nb sheets introduces microstructural defects such as dislocations and low-angle grain boundaries that can serve as favorable sites for pinning centers for magnetic flux that may degrade cavity performance. Therefore, effects of grain boundary on magnetic flux behavior in carefully strained bicrystal Nb samples were investigated. Laue X-ray and EBSD-OIM crystallographic analyses were used to characterize microstructural defects and then predict which grain boundaries and orientations will produce desired model defects by tensile deformation. Grain boundaries and orientations were chosen to favor specific slip systems, which generate dislocations with special angles with respect to the grain boundaries of the bicrystal Nb samples. The generated defect structures were confirmed by OIM and ECCI. Cryogenic magneto-optical imaging was used to directly observe the penetration of magnetic flux into the deformed Nb. These model samples have deformation that is similar to that expected in typical cavity forming processes.

This work was supported in part by Research supported by DOE/OHEP (contract number DE-FG02-09ER41638 at MSU, and DE-SC0009960 at FSU) and the State of Florida.

 

Poster Number: MSE-11

Title: Tetrahedrite Thermoelectrics: Mechanical Alloying versus SPS Solid-State Reaction Synthesis

Authors: Daniel P. Weller; Junchao Li; Wei Lai; Donald T. Morelli

Abstract: Thermoelectric (TE) materials are capable of converting thermal energy to electrical energy by a phenomenon known as the Seebeck effect. These materials could play an important role in alleviating the world’s energy crisis by recovering waste heat and transforming it into usable electric power. However, there are many setbacks which are impeding the widespread use of thermoelectrics in our society. For example, numerous TE materials are comprised of toxic elements, such as lead, or costly elements like tellurium. Additionally, numerous thermoelectrics involve complicated synthetic procedures that hold them back from being used in large-scale commercial applications. Nevertheless, one promising material has emerged as a potential solution to all of these issues. Tetrahedrite, a common mineral that occurs naturally in the earth, has been shown to demonstrate good electrical and thermal properties for TE applications. This material is entirely composed of inexpensive and environmentally friendly elements such as copper, antimony, and sulfur. Typical synthesis of tetrahedrite consists of a slow heating process with a lengthy annealing time, usually on the order of one to two weeks total. In this work, results will be shown for samples made by mechanical alloying and by direct reaction via spark-plasma-sintering (SPS). Mechanically alloyed samples can be synthesized in approximately forty eight hours, while those made via SPS can be prepared in less than two hours. The properties of the samples made with the different techniques will be presented for both zinc and nickel doped samples.

This work was supported in part by NSF-CBET Award No. 1507789

 

Poster Number: MSE-12

Title: Understanding the Superior thermoelectric Performance of Sb Precipitated Ge17Sb2Te20

Authors: Jared B. Williams; Donald T. Morelli

Abstract: Phase change materials are based on Ge-Sb-Te alloys and named so because of their memory storage applications, which exploit the large optical/electrical contrast between the amorphous and crystalline phases. They are being researched as a nonvolatile replacement to RAM-based memory systems which are volatile and limited in storage capacity. Recently these materials have also been identified as high-performance thermoelectric materials. Thermoelectric materials are utilized in waste-heat recovery applications ranging from large scale, such as diesel generators, down to small scale applications, such as microelectronics and flexible electronics. When alloys from the GeTe-Sb2Te3 pseudo-binary tie-line are quenched from the melt they exhibit a highly disordered metastable phase with low thermal conductivity and high Seebeck coefficient. Upon heating, the compounds undergo an ordering transition to a stable rhombohedral phase which is metallic in nature, all while maintaining a low thermal conductivity and high Seebeck coefficient. The following work examines the effects which Sb precipitates have on the thermoelectric properties of Ge17Sb2Te20. It was found that the precipitation of Sb within the matrix of Ge17Sb2Te20 lowers thermal conductivity and enhances the Seebeck coefficient, which leads to an optimization of ZT, a dimensionless figure-of-merit based on the electrical conductivity, thermal conductivity, and Seebeck coefficient, which is used to quantify the efficiency of thermoelectric materials.

This work was supported in part by Department of Energy's Energy Frontier Research Center; National Science Foundation

 

Poster Number: MSE-13

Title: Crystal Plasticity Analysis of Polycrystalline Ti-5Al-2.5Sn Using Realistic 3D Microstructure

Authors: C. Zhang; P. Eisenlohr; T.R. Bieler; M.A. Crimp; C.J. Boehlert

Abstract: to investigate damage nucleation in polycrystalline materials with computational analysis, it is crucial to numerically represent the heterogeneous slip activity induced by plastic defor- mation, which is affected by both the intrinsic material properties and the spatial arrangement of grains. A previous study of a Ti-5Al- 2.5Sn sample deformed in uniaxial tension at room temperature demonstrated that the combination of a realistic 3D microstruc- ture and a simple phenomenological power-law based constitu- tive model can successfully capture the plastic deformation in- duced crystal reorientation. An improved version of this computational framework is presented here with automated microstructure reconstruction and a faster solver for the stress analysis simulation using the spectral solver provided by the DAMASK package.

This work was supported in part by This research was supported by DOE/BES grant DE-FG02-09ER46637, and the DAXM characterization at the Advanced Photon Source was supported by DOE contract DE-AC02-06CH11357.

 

Poster Number: MSE-14

Title: The Performance and Long-Term Stability of SOFC Cathodes Under Different Infiltration Conditions

Authors: Yubo Zhang; Jason D. Nicholas

Abstract: With the growing demand of high-efficiency, environment-friendly energy conversion technology, reversible Solid Oxide Fuel Cells (SOFCs) are becoming one of the most promising chemical to electrical conversion technologies because of 1) their high gravimetric and volumetric power densities and 2) ability to use either traditional fossil fuels or hydrogen as fuels. Unfortunately, the poor oxygen surface exchange kinetics of SOFC cathodes have hindered this technology by restricting commercial SOFC operating temperatures to greater than ~650C. The infiltration method has been shown to be an effective way to produce nano-composite SOFC cathodes that can operate at temperatures as low as 550C. In this technique, nano-sized Mixed Ionic and Electronic Conductor (MIEC) oxygen exchange catalyst particles are generated by infiltrating MIEC nitrate precursor solutions into porous Ionic Conducting (IC) scaffolds. Unfortunately, past studies have shown that it is difficult to control the size of the MIEC nanoparticles produced by infiltration. Furthermore, the relationship between particle sizes, structure, performance and long-term cathode stability remains to be fully understood. It’s been proved that desiccation can affect the particle size, performance and long-term stability of La0.6Sr0.4Co0.8Fe0.2O3- (LSCF) particles. The present work highlights how different infiltration conditions (nitrate precursor solution chemistries, desiccant strength, etc.) will affect the infiltrate particle size and phase purity, electrical resistance and long-term stability of La0.6Sr0.4FeO3(LSF) and La0.6Sr0.4Co0.2Fe0.8O3 (LSFC) cathodes.

 

Poster Number: MSE-15

Title: New Braze Materials for Planar Solid Oxide Fuel Cell (SOFC) Applications

Authors: Quan Zhou; Yuxi Ma; Tridip Das; Yue Qi; Jason D. Nicholas; Thomas R. Bieler

Abstract: A stable hermetic seal is crucial to the functionality and durability of planar solid oxide fuel cell (SOFC) stacks. Reactive air brazing (RAB) has become very popular and Ag-CuO brazes are commonly used in joining yttrium stabilized zirconia (YSZ) with stainless steels. However, despite the acceptable wettability and good ductility of Ag-based brazes, the high diffusivity of hydrogen and oxygen in silver makes Ag-based brazes vulnerable to internal water vapor bubble formation, which significantly shortens their lifetimes in SOFC stacks. Here, samples with compositions obtained from computational studies were fabricated using arc-melting. Optical/electronic microscopy, energy dispersive X-ray spectroscopy, differential scanning calorimetry, and thermal gravimetric analysis were performed to characterize the microstructure, chemistry, melting and oxidation behavior of new, computationally-suggested braze compositions. In addition, wetting studies with/without surface pre-treatments were carried out on both YSZ and alumina in a controlled atmosphere optical tube furnace.

This work was supported in part by This project is supported by DOE with Delphi under the award No.: FE0023315


Poster Number: MSE-16

Title: Exceptionally High Strength Beta Titanium Alloy at Elevated Temperatures Achieved by Thermomechanically-Induced Phase Transformation

Authors: Vahid Khademi; Carl J. Boehlert

Abstract: Titanium alloys have been used in diverse fields, such as aerospace, biomedical, energy, and chemical equipment, due to its combination of good mechanical properties, chemical and oxidation resistance, and biocompatibility. Furthermore, titanium alloys have been used for elevated temperature applications, for example in jet engine parts, and power plant equipment. However, the cost still could be considered as a major limitation on the expansion of new titanium alloys and their applications. In the current work, a new method was introduced which results in the highest measured tensile strength for a titanium alloy in the temperature range between 400 °C to 500 °C. The results indicated that the elevated temperature strength was significantly higher than the room temperature strength, i.e. the room temperature strength was 940 MPa, while the strength was 1435 MPa at 410 °C. It should be mentioned that strength usually decreases with increasing the temperature.  The transmission electron microscopy, in-situ scanning electron microscopy experiments, and dynamic mechanical analysis investigations relieved that thermomechanically-induced phase transformation plays an essential role on this exceptional phenomenon. Importantly, this method which was applied on a low-cost titanium alloy, might open a new window for the current state of titanium alloy applications and research. (Patent Pending)

This work was supported in part by DOE