Characterization of Minerals, Metals, and Materials: Powders and Foams
Sponsored by: TMS Extraction and Processing Division, TMS: Materials Characterization Committee
Program Organizers: Shadia Ikhmayies, Al Isra University; Bowen Li, Michigan Technological University; John Carpenter, Los Alamos National Laboratory; Jian Li, CanmetMATERIALS; Jiann-Yang Hwang, Michigan Technological University; Sergio Monteiro, Military Institute of Engineering ; Firrao Donato, Collegio Universitario, Italy; Mingming Zhang, ArcelorMittal Global R&D; Zhiwei Peng, Central South University; Juan P. Escobedo-Diaz, UNSW Australia; Chenguang Bai, Chongqing University; Eren Kalay, METU; Ramasis Goswami, Naval Research Laboratory; Jeongguk Kim, Korea Railroad Research Institute

Tuesday 2:00 PM
February 28, 2017
Room: 31B
Location: San Diego Convention Ctr

Session Chair: Juan Escobedo-Diaz, UNSW Australia; Brahim Akdim, Air force Research Lab

2:00 PM  
Microstructural Evaluation of Ti-6Al-4V Powder Compacts Sintered by Microwave Energy: Kenneth Grabowski1; Evan Groopman2; Benjamin Rock1; M Imam3; Albert Fahey1; 1Naval Research Laboratory; 2National Research Council; 3George Washington University
    Sintering of Ti-6Al-4V powder compacts by microwave energy may provide a more economical approach to fabricating near-net shapes of this alloy due to improved efficiencies in processing. Microwaves couple more directly with the powder, thereby shortening the time required to attain a given high temperature for consolidation of powder compacts. A susceptor is used to homogenize the temperature. This work examines the microstructure obtained from microwave sintering of relatively large compacts at 1250°C for various times. Comparison is made with conventional recrystallization annealed material. To study the resulting microstructure and its effect on mechanical properties, a new and unique instrument combining a secondary ion mass spectrometer with a single stage accelerator mass spectrometer (SIMS-SSAMS) was employed, enabling the spatial distribution of H as well as Ti, Al, and V to be examined. This will be combined and discussed with x-ray maps of Ti, Al, and V obtained by SEM.

2:20 PM  
Residual Stress Analysis within Steel Encapsulated Metal Matrix Composites Via Neutron Diffraction: Sean Fudger1; Dimitry Sediako2; Prashant Karandikar3; Chaoying Ni1; 1University of Delaware; 2Canadian Neutron Beam Centre; 3M Cubed Technologies, Inc.
    Neutron diffraction measurements were performed on steel encapsulated metal matrix composites (MMCs) in order to quantify bulk residual stresses. A coefficient of thermal expansion (CTE) mismatch induced residual compressive stress method is utilized as a means of improving the ductility of the MMCs and overall efficiency of several macro hybridized materials systems. Systems consisting of an A36, 304 stainless steel, or Nitronic®50 stainless steel shell filled with an Al-SiC or Al-Al2O3 metal matrix composite are evaluated in this work. Upon cooling from processing temperatures residual strains are generated due to a CTE mismatch between each of the phases: steel, aluminum, and reinforcement. The analysis shows variation in the measured strain and stress results due to outer steel thickness, difference in CTE between materials, and relative position within the composite.

2:40 PM  
Microstructure and Phase Evolution during the Synthesis of Manganese Germanides: Vamsi Meka1; Tanjore Jayaraman1; 1University of Michigan
    Transition metal germanides are known to have interesting combination of electronic and magnetic properties suitable for a variety of applications including magnetoelectronic devices. In this work, microstructure and phase evolution during the synthesis of germanium-rich manganese-germanides is presented. Mechanical alloying of manganese-germanium elemental powder blends was carried out as a function of milling time. X-ray diffraction and scanning electron microscopy were employed to characterize the phases present in the milled powders. At the initial stages of milling, supersaturated solid solutions were formed. Increased milling time, greater than ~50 hours, resulted in the formation of the desired intermetallic metastable phase. The magnetic properties of manganese-germanides were characterized by vibration sample magnetometry. The properties were compared with transition metal germanides available in the literature.

3:00 PM  
Application of AFM in Morphology Determination of Powder Material: Jian Wu1; Ping Long1; Yaochun Yao1; 1Kunming University of Science and Technology
     Atomic force microscope (AFM) is widely used for determining of surface performance of materials with smoother surface. In this research, atomic force microscope was used in morphology determination of powder material. Samples were dispersed in aqueous system by ultrasound wave and prepared on mica sheet. Multiple mappings of different powder samples, such as ferrous oxalate, lithium carbonate, barium carbonate, boron powder, ferric oxide and zinc oxide, were investigated and analyzed in detail. Results showed as follow: ferrous oxalate sintered in different processes and conditions presented different morphology characteristics both in shape and size. Ferrous oxalate obtained special process presented two-dimension lamella structure and self-assembly phenomenon. The shape and size of lithium carbonate particles were uniform. Defects of mappings on boron powder, ferric oxide and zinc oxide reflected problems of the preparation process before scanning. Determination experiences of powder material in AFM technology could be obtained.

3:20 PM  Cancelled
Fracture Toughness Characterization of Spark Plasma Sintered Boron Carbide with Different Additives.: Burcu Apak1; Meral Cengiz1; Onuralp Yucel1; Gultekin Goller1; Filiz Sahin1; 1İstanbul Technical University
    Boron carbide powders with different amounts of light weight metallic and carbon additives are spark plasma sintered in order to examine the effects of these additives on boron carbide. As widely known, boron carbide has an extremely high hardness whereas the main drawback of boron carbide is its low fracture toughness. With different additions made to the boron carbide structure, to increase the fracture toughness is aimed. The spark plasma sintering is held in the temperature range between 1400-1550 °C for 4 minutes, under an applied pressure of 50 MPa. After spark plasma sintering procedure, the densification of composites were measured by Archimedes method whereas the hardness and fracture toughness of boron carbide composites were measured by Vickers indentation technique. The crack propagation behavior of ceramics were observed by using Scanning Electron Microscopy

3:40 PM Break

3:55 PM  
Effects of Thermal Processing on Closed-Cell Aluminium Foams: Andrew Brown1; Wayne Hutchison1; Md Ashraful Islam1; Md Abdul Kader1; Juan Pablo Escobedo-Diaz1; Paul Hazell1; 1UNSW Australia
    The effects of post-foaming thermal processing on the quasi-static compressive strength of closed-cell aluminum foam with an average relative density of 0.56 g/cc have been investigated. Samples were subject to one of four material conditions: as-received (AR), warm aged (WA), solution treated (ST), and annealed (AT). X-ray diffraction (XRD) was performed to determine a relationship between each material condition and macro-crystallographic texture of the dendritic α-Al phase. It was found that all heat treated samples contained clear deviations from random texture towards the exterior regions of the samples, indicating non-uniform recrystallization kinetics. The ST and WA samples exhibited the highest yield stresses and energy absorption, with the AT samples exhibiting the lowest. Additionally, it was found that the AR and WA conditions lost 12.8% and 15.6% of their total mass from brittle cell wall crumbling, whereas the AT and ST conditions lost 2.5% and 3.0% of their total mass.

4:15 PM  
Experimental Investigation of Mechanical Behaviour of Closed-Cell Aluminium Foams under Drop Weight Impact: Md Ashraful Islam1; Md Abdul Kader1; Andrew Brown1; Paul Hazell1; Juan Pablo Escobedo - Diaz1; Mohammad Saadatfar1; 1UNSW Canberra
    The dynamic pore collapse mechanisms and energy absorption capacity of closed-cell aluminium foams subjected to low velocity impacts have been investigated. Impact experiments were carried out using an instrumented drop-tower with two impactor geometries: a 50 mm square flat steel impactor to investigate pore collapse mechanisms and a 20 mm diameter hemispherical steel impactor to study indentation resistance. X-ray computed tomography was utilized to generate views of the deformation field within the impacted specimen. The results show that the strain rate and incident impact energy influence the energy absorption capacities of closed-cell aluminium foams. Furthermore, damage initiation, propagation and cell collapse mechanisms under drop weight impact have been elucidated.

4:35 PM  
Deformation Mechanisms of Closed Cell-Aluminium Foams during Drop Weight Impact: M.A. Kader1; M.A. Islam1; M. Saadatfar2; Juan P. Escobedo-Diaz1; P.J. Hazell1; A.D. Brown1; 1School of Engineering and Information Technology, UNSW Australia; 2Department of Applied Mathematics, Australian National University
    The present study investigates the dynamic deformation mechanisms of closed-cell aluminium foams during low velocity drop weight impact with experimental analyses and finite element (FE) simulation. The evolution of foam collapse was explored with FE simulation using ABAQUS/Explicit. X-ray computed tomography (XRT) based geometry was reconstructed to understand the actual microstructural changes during impact. The experimental stress-strain response was compared with FE simulation with reasonably good agreement observed between FE prediction and experimental data. A vertical cross-sectional XRT slice was analysed at different strains from FE simulation to understand the pore collapse mechanisms.

4:55 PM  
Optical Characterization of α-Ti Grain Orientation: Insight from First-principles Calculations: Brahim Akdim1; Chris Woodward1; Micheal Uchic1; 1Air Force Research Lab
    Ellipsometry is a well-developed characterization method based on the analysis of the polarization of light reflected from the sample. It is a non-destructive technique, with the advantage of imaging large areas in a short time basis. In this work, optical properties of pure alpha-phase titanium in the bulk structure were derived using first-principles calculations. The predicted optical conductivity, obtained within the random phase approximation, demonstrated high anisotropy, discerning the basal plane from the principle axis of the hexagonal lattice. The results were subsequently used to guide the ellipsometry measurements by identifying wavelengths that exhibit the largest anisotropy. In addition, the predicted refractive indices were used, through generalized Fresnel's equations derived for uniaxial crystals, to interpret the observed intensities as a function of the orientation of the principle axis in the grain with respect to the laboratory frame.

5:15 PM  
Tracking 3D Microstructure Evolution during Sintering of Copper Particles by Laboratory Diffraction Contrast Tomography (LabDCT): Samuel McDonald1; Christian Holzner2; Erik Lauridsen3; Peter Reischig3; Arno Merkle2; Michael Feser2; Philip Withers1; 1University of Manchester; 2Carl Zeiss X-ray Microscopy; 3Xnovo Technology
    The development of a novel laboratory-based X-ray diffraction contrast tomography modality (LabDCT) has enabled the wider accessibility of the DCT technique for in-depth studies of temporal changes in crystallographic grain structure non-destructively during ‘4D’ studies of microstructure evolution. Here we use the newly established LabDCT technique to follow all the processes occurring during sintering of copper powder from loose powder to high levels of consolidation. Conventional absorption delineates the diffusion and deformation-related shape changes of the sintering particles. In mapping the individual grains within the polycrystalline copper particles, time lapse LabDCT has enabled the particle rearrangements and rotations to be inferred from measuring the changes in crystallographic orientation of grains. Over longer timescales, LabDCT has also allowed grain growth to be tracked. Such information provides unique insights into the sintering micromechanisms and will hopefully lead to better sintering process control leading to dense products with minimal grain growth.