Characterization of Minerals, Metals and Materials: Advances in Characterization Methods I
Sponsored by: TMS Extraction and Processing Division, TMS: Materials Characterization Committee
Program Organizers: Jian Li, CanmetMATERIALS; Mingming Zhang, Baowu Ouyeel Co. Ltd; Bowen Li, Michigan Technological University; Sergio Monteiro, Instituto Militar de Engenharia; Shadia Ikhmayies; Yunus Kalay, Middle East Technical University; Jiann-Yang Hwang, Michigan Technological University; Juan Escobedo-Diaz, University of New South Wales; John Carpenter, Los Alamos National Laboratory; Andrew Brown, Devcom Arl Army Research Office
Monday 8:00 AM
February 24, 2020
Room: Theater A-5
Location: San Diego Convention Ctr
Session Chair: Mingming Zhang, ArcelorMittal Global R&D; Kelvin Xie, Texas A&M University
8:00 AM Introductory Comments
8:05 AM
Auger Spectroscopy Analysis of Alpha Brass Fracture: Sergio Monteiro1; Fabio Garcia Filho1; Fernanda Luz1; Ulisses Costa2; Lucio Fabio Nascimento1; 1Military Institute of Engineering - IME; 2Military Institute of Engineering
The ductile fracture of a type 65/35 alpha brass tested in tension at room temperature has been studied inside the ultra-high vacuum chamber of an Auger/scanning/micro-probe equipment. The fracture characteristics of small specimens tensile deformed in especially designed apparatus were registered in terms of the morphological aspects and quantitative participation of elements. It was observed that the ductile fracture is associated with ZNS inclusions separated from the Pb rich alloy interface. Regions without inclusions but with Pb segregation are possible sites favorable to the fracture propagation.Keywords: Auger spectroscopy, alpha brass, ductile fracture, Pb segregation
8:25 AM
Comparison of Diffraction Techniques for Texture Evaluation in Triaminotrinitrobenzene (TATB): Matthew Schmitt1; Sven Vogel1; John Yeager1; Ricardo Schwarz1; 1Los Alamos National Laboratory
The study of highly hydrogenated materials, such as hydrocarbons, geological materials, or hydrogen storage materials using diffraction techniques is often difficult. This is no exception for the explosives triaminotrinitrobenzene (TATB), and PBX 9502 (95% TATB, 5% binder). These materials are difficult to characterize using traditional laboratory techniques due to a problematic combination of low-Z composition, weak mechanical integrity, and a triclinic crystal structure. This study compares texture analysis of TATB samples using three different diffraction techniques: laboratory x-ray, synchrotron x-ray, and neutron diffraction. Laboratory x-ray diffraction was used to rapidly obtain partial pole figures for thinly sliced samples. Synchrotron x-ray at the Advance Light Source (ALS) was used to provide complete pole figures of spatially resolved locations within the samples. Finally, neutron diffraction experiments using the HIPPO diffractometer at the Los Alamos Neutron Science Center (LANSCE) provides an average bulk sample textures that can be analyzed from much thicker samples.
8:45 AM
EBSD Characterization of Aluminum Magnesium Alloys: Karina Hemmendinger1; Joel Bahena1; Andrea Hodge1; 1University of Southern California
5xxx series aluminum alloys are susceptible to sensitization, where magnesium beta-phase precipitates at the grain boundaries increase the likelihood of intergranular corrosion. One method that could improve the corrosion resistance of these materials is to increase the proportion of special grain boundaries (Sigma ≤ 29) through grain boundary engineering. Thus, films of 5xxx series aluminum were synthesized via magnetron sputtering to study the effect of sputtering rate on the proportion of special grain boundaries.Electron backscatter diffraction (EBSD) was used to determine the grain structure, grain orientations, and distribution of special grain boundaries through the material. Standard EBSD and transmission EBSD (t-EBSD) were performed. Analysis of EBSD measurements and TEM images showed a correlation between sputtering rates and the fractions of special grain boundaries, as well as between sputtering rates and grain diameter.
9:05 AM
Using the New Rotation Vector Base Line Electron Back Scatter Diffraction (RVB-EBSD) Method to Characterize Single Crystal Cast Microstructures: Pascal Thome1; Setareh Medgalchi1; Felicitas Scholz1; Gunther Eggeler1; Jan Frenzel1; 1Ruhr-Universität-Bochum
We present the Rotation Vector Base Line Electron Back Scatter Diffraction (RVB-EBSD) method, a new correlative orientation imaging method for scanning electron microscopy (OIM/SEM). The RVB-EBSD method was developed to study small angle orientation defects in single crystals (SX). The technique allows to quantify small misorientation angles between subgrains and to interpret associated accommodation processes in terms of geometrically necessary dislocations (GNDs). The RVB-EBSD method was inspired by previous approaches which use cross correlation EBSD procedures. It applies Gaussian band pass filtering to improve the quality of more than 500 000 experimental patterns. A rotation vector approximation and a correction procedure, which relies on a base line function, are used. The method moreover features a novel way of intuitive color coding which allows to easily appreciate essential features of single crystal defects. In the present work we present examples from RVB-EBSD characterization of single crystals and additively manufactured materials.
9:25 AM
On the Depth Resolution of Transmission Kikuchi Diffraction (TKD) Analysis: Junliang Liu1; Sergio Lozano-Perez1; Angus Wilkinson1; Chris Grovenor1; 1University of Oxford
Transmission Kikuchi diffraction (TKD) has been widely utilized in the characterization of nano-crystalline materials, but a better understanding of the achievable depth resolution is still required to understand the potential and the limitations of this technique. In this work we report on experimental measurements on model Zr-Nb alloys of the depth resolution achievable using an on-axis TKD system. The results indicate that the signals contributing to Kikuchi bands originate from a depth of approximately the mean free path of thermal diffuse scattering from the bottom surface of samples, ~20 nm in Zr-Nb alloy. This strong surface sensitivity can thus lead to the observation of different grain structures when opposite sides of the same region of a nano-crystalline foil are scanned. These results also provide a guideline for the optimum sample thickness in order to achieve clear and indexable Kikuchi patterns for TKD analysis.
9:45 AM Break
10:00 AM
Correlative Microscopy Studies of <c+a> Dislocations in a Hot-roll AZ31 Mg Alloy: Dexin Zhao1; Xiaolong Ma1; Kelvin Xie1; 1Texas A&M University
In this work, we developed a correlative microscopy technique, employing both EBSD and TEM to characterize the <c+a> dislocations in a highly textured hot-rolled AZ31 Mg alloy. EBSD was firstly used to map the grains in the electron transparent region to reveal the crystal orientation with respect to the loading direction. TEM was then applied to study the dislocations in the EBSD examined grains. We observed that <c+a> dislocations were activated in most of the grains even for those with the grain orientations unfavorable for <c+a> dislocations. This observation suggests that the overall texture may strongly influence individual grain’s deformation mode and the roles of the exact orientation of individual grains is less relevant.
10:20 AM
Micromechanical Properties of Marginal Glass Forming Alloys: İlkay Kalay1; Tolga Han Ulucan2; Sezer Özerinç2; Yunus Kalay2; 1Çankaya University; 2Middle East Technical University
Al-Rare Earth (RE) based alloys constitute an important class of the marginal glass forming alloys, where the primary crystallization is accompanied by the presence of Al nanocrystals. In this study, we produced Al-Tb melt-spun marginal metallic glass ribbons and heat-treated them at different temperature to form Al nanocrystals with different size and number density embedded in the amorphous matrix. Nanoindentation and micropillar compression tests were performed to reveal the micro mechanical properties of the amorphous and partially crystalline alloys. SEM images have been taken to investigate fracture behavior. The heat-treated specimens which contain fcc-Al nanocrystals show strengths above 1.2 GPa with the indication of curvatures in stress-strain demonstrating an enhanced ductility. The mechanisms behind the increased strength and ductility through devitrification will be discussed in details using a combined study of micromechanical characterization, differential scanning calorimetry, X-ray diffraction and electron microscopy.
10:40 AM
Case Study of A36 Steel Plate: Ramon Martinez1; Veronica Livescu1; Jillian Bennett1; Carl Cady1; James Valdez1; Carl Trujillo1; 1Los Alamos National Laboratory
The development of a proper flow stress model is essential in predicting material deformation behavior at high strain rates and temperatures. The present study addresses detailed experimental investigation of A36 steel plate carried out at varying strain rates and temperatures to determine parameters for modeling and simulation. Stress state is an important factor determining when fracture occurs; in particular, the stress triaxiality plays an important role in the tendency for ductile fracture. The Johnson-Cook model is used to capture rate-dependent plasticity and ductile damage, which can be used for impact and penetration problems. Digital image correlation was performed when applicable to verify the materials mechanical response. The true stress and strain relationship as well as the stress triaxiality factors as a function of failure strain were determined. The discussion will also address sample design/selection, as well as influence of microstructure orientation on material behavior.
11:00 AM
In-situ Raman Microprobing and Ex-situ Raman Mapping of Indented Glasses: Yvonne Gerbig1; Chris Michaels1; 1National Institute of Standards and Technology (NIST)
This talk will address two challenges in the spectroscopic characterization of indented glasses: (1) in-situ observations of local structural changes during indentation: The integration of in-situ Raman microscopy with instrumented indentation has the potential to provide descriptive insights into the relationship between structure and densification of glasses. (2) ex-situ mapping of the densified region: Raman spectroscopic measurements in the past suffered from low spatial resolution, hence, requiring impressions created by Newton-range forces to map densification variations with reasonable resolution but potentially affecting the densified area due to crack initiation. This talk will describe a custom-built optical instrument for in-situ Raman microscopy suitable for collecting high-quality spectroscopic data during the indentation of glasses. Experimental conditions for ex-situ Raman mapping will be discussed under which indentations at milli-Newton force can be effectively studied. Possible pitfalls in ex-situ and in-situ measurements on indented glasses and resulting misinterpretations of spectral data will be highlighted.
11:20 AM
Synchrotron X-ray Diffraction and Computed Tomography Studies of Ultrasonic Welding Dissimilar Mg-Fe Metals: Lianghua Xiong1; Chihpin Chuang1; Dileep Singh1; Jian Chen2; Yong Chae Lim2; Zhili Feng2; 1Argonne National Laboratory; 2Oak Ridge National Laboratory
Ultrasonic welding dissimilar metals (like magnesium and steel) combines the merits of lightweight and high strength, and has vast potential in automotive industry requiring components with cost and energy efficiency. Due to the metallurgical incompatibility between magnesium and steel, formation of intermetallic compounds and residual strain across the interface remain open questions and hinder the wider application. However, it is challenging for conventional methods, such as optical and scanning/transmission electron microscopies, to obtain three-dimensional interface structure. Here, we apply synchrotron x-ray diffraction and high-energy computed tomography to characterize the microstructure across Mg-Fe interface. New intermetallic compounds are revealed and residual strain is quantified. High-resolution 3D morphology of Mg-Fe interface is reconstructed and quantified. The results obtained will benefit producing reliable joints of dissimilar metals and validate metallurgical and mechanical modelling.