Resume

• 2008

  PhD

  Materials Science and Engineering

  Materials Advantage

  OSU triathlon club

  marathon-in-training club

  The Ohio State University

• 2006

  Masters of Sciences

  Materials Science and Engineering

  Materials Advantage

• 2001

  Bachelor of Science

  Mechanical Engineering/ Materials Science and Engineering Double

  Tau Beta Pi

  ASCE

  ASCE steel bridge team

  Materials Advantage

• Scanning Electron Microscopy

  Characterization

  Electron Microscopy

  Metallography

  TEM

  Engineering Education

  EDX

  Spectroscopy

  Failure Analysis

  FIB

  Powder X-ray Diffraction

  Composites

  Design of Experiments

  Experimentation

  Optical Microscopy

  Materials

  Nanomaterials

  Mechanical Testing

  Materials Science

  Local Strain Accommodation in Polycrystalline Ni Base Superalloys

  Michael J. Mills

  Robert Wheeler

  To exploit new hybrid nickel-based superalloys

  physics-based computational models are needed to predict material properties and describe material behavior during exposure to complex life cycles. Such models will allow an iterative assessment of microstructural morphology as related to mechanical properties prior to production of large-scale test specimens or components

  thereby reducing development time and cost. Development of these models is currently hindered by a gap in the understanding of local deformation behavior at the intra- and intergranular level. A new in-situ experimental methodology is being developed to characterize local strain heterogeneities in nickel-based superalloys that have a relatively fine grain size (dave<50μm). Initial work has been performed on Rene 104 that was heat treated to produce two sets of samples with a similar grain size but different γ’ distributions and grain boundary morphologies. One sample set had planar boundaries and a bimodal γ’ distribution

  the other set had serrated boundaries and a trimodal γ’ distribution. Progress has been made towards implementation of a suitable speckle pattern for digital image correlation (DIC). Quasi-isostatic room temperature tensile tests were performed in a scanning electron microscope

  with images acquired at regular strain intervals. This preliminary data was qualitatively analyzed using Correlated Solutions VIC-2D software. The data for the serrated boundaries indicates that there are indeed interesting strain heterogeneities being developed that are related to grain orientations

  boundary relationships to the tensile axis and other boundaries.

  Local Strain Accommodation in Polycrystalline Ni Base Superalloys

  A materials data analytics (MDA) methodology was developed in this study to evaluate publicly available information on 9% Cr family steel and to handle nonlinear relationships and the sparsity in materials data for this alloy class. The overarching goal is to accelerate the design process as well as to reduce the time and expense associated with qualification testing of new alloys for fossil energy applications. Data entries in the analyzed data set for 82 iron‐base alloy compositions

  several processing parameters

  and results of tensile mechanical tests selected for this study were arranged in 34 columns by 915 rows. While detailed microstructural information was not available

  it is assumed that the compositional space for the 9 to 12% Cr steels is limited such that all data entries have a tempered martensitic microstructure during service. Establishing a hierarchy of first‐order trends in the publicly available data requires the MDA to filter out the biases. Complexity of the phase transformations and microstructure evolution in the multicomponent alloys (using 21 chemical elements) with major influence on mechanical properties

  leads to inefficiency in direct application of unbiased linear regression across the entire data space. To address the nonlinearity

  analyses of tensile data were performed in composition‐based clusters. Clusters corresponding to moderately frequent patterns and maximized information gain were further refined by using p‐norm distance measures

  matching the alloy classification groups adopted by industry. The evolutionary method of propagating an ensemble of competing cluster‐based models proved to be a viable option in dealing with scarce

  multidimensional data.

  Materials Data Analytics for 9% Cr Family Steel

  Functional graded materials (FGM) allow for reconciliation of conflicting design constraints at different locations in the material. This optimization requires a priori knowledge of how different architectural measures are interdependent and combine to control material performance. In this work

  an aluminum FGM was used as a model system to present a new network modeling approach that captures the relationship between design parameters and allows an easy interpretation. The approach

  in an un-biased manner

  successfully captured the expected relationships and was capable of predicting the hardness as a function of composition.

  Physics-Informed Network Models: a Data Science Approach to Metal Design

  Tensile and fracture toughness behavior of a Zr-based bulk metallic glass matrix composite (BMGMC) containing a body-centered cubic crystalline phase was examined over temperatures from 77 K to 653 K (−196 °C to 380 °C). The BMGMC exhibited tensile plasticity at all test temperatures. The sample tested in tension at 173 K (−100 °C) exhibited work hardening but the remaining samples tested at higher temperatures exhibited work softening. EBSD analysis of the crystalline phase after tensile testing provides insight into active deformation mechanisms in the crystalline phase. At 603 K (330 °C)

  the dendrites exhibit significant plastic strain

  with the dendrites oriented {101} parallel to the loading direction exhibiting the least amount of strain. Schmid factor analysis leads to the hypothesis that {110}〈111〉 dislocation mechanisms are active at this temperature. Additionally

  measurements of dendrite shape as a function of macroscopic strain state in the tension experiments provide insight into cooperative deformation mechanisms in the composite. At low temperatures

  the fracture toughness of the notch toughness samples exceeded that of fatigue precracked samples; but at and above room temperature

  the toughness values of notched and fatigue precracked samples converge. These observations are rationalized based on the changes to the flow and fracture behavior of the glass and the crystalline phases over this temperature range. At low temperatures

  the crystalline phase is sensitive to defects and changes in stress state that reduce its energy absorbing ability. At higher temperatures

  both constituents possess lower strength and are less sensitive to defects

  enabling more significant crack tip blunting in the fatigue precracked samples. This produces toughness values that are similar to those obtained for the notched samples.

  Henry J. Neilson

  Materials Science and Engineering A

  Using a large database of metallic glasses (N=174)

  an equation was developed to improve estimating shear and bulk moduli of metallic glasses containing multiple constituents. This equation was applied to several different subsets of metallic glasses: those containing any element

  those containing only metallic elements

  those containing at least one nonmetal

  and those containing at least one constituent with no more than 5 at% of the whole glass. Comparisons to other calculation methods and measured elastic constants for these systems are provided. The present equation provided an improved confidence in the estimations of bulk and shear moduli for all of the cases examined in comparison to previous equations

  while the biggest improvement occurred for metallic glasses containing nonmetal constituents.

  An improved method for calculation of elastic constants of metallic glasses

  In this paper

  an automated algorithm

  written in Python (v2.7)

  is presented to apply modified Hertz’s theory to extract the Elastic Modulus and indentation stress-strain curve from the load-displacement data. Two methods of assuming the contribution of the elastic deformation of the indenter are presented.

  An Automated Technique to Analyze Micro Indentation Load-Displacement Curve

  At present

  obtaining accurate volume fraction and size measurements of γ″

  γ′

  and δ precipitates in Superalloy 718 has been challenging due to their size

  crystal structures

  low volume fractions

  and similar chemistries. These measurements are necessary to validate precipitation models that in turn enhance selective laser melting fabrication. Superalloy 718 is a promising candidate for selective laser melting fabrication due to a combination of excellent mechanical properties and workability. A new technique

  combining high resolution distortion corrected SEM imaging and with high resolution x-ray energy dispersive spectroscopy

  has been developed to accurately and independently measure the size

  volume fraction

  and number densities of these three precipitates. A specimen of selective laser melted superalloy 718 was obtained and underwent a conventional heat treatment for superalloy 718 where it was solutionized at 1010 °C for one hour

  gas quenched and followed by a two-step age (718 °C/11 h → 621 °C/6 h) in order to produce a microstructure with all three precipitate types present. These results were further validated using x-ray diffraction and phase extraction methods.

  Characterization of nanoscale precipitates in superalloy 718 using high-resolution SEM imaging

  Molecular dynamics (MD) was used to gain insights into grain boundary (GB) shear mechanisms in alloys that require GB mobility in a field of coherent precipitates. The area fraction of the Σ11 affected by the \uD835\uDEFE′ was systematically varied to explore how GB shear mechanisms change with increased number of precipitates. Without precipitates

  local atomic shuffling accommodates the Σ11 GB shear; above an area-fraction threshold

  GB shear required dislocation emission. In addition to precipitate area fraction

  the transition in GB shear mechanisms may also depend on precipitate shape/size

  temperature

  and GB misorientation. These factors will be investigated in future work.

  Exploration of the sliding behavior of a Σ11 grain boundary with precipitates in Ni–Al system using molecular dynamics

  David Ellis

  Materials Science and Engineering A

  Reusable launch vehicles require main combustion chamber liner materials that can withstand elevated temperatures and high stresses without creeping. GRCop-84 (Cu-8 at.% Cr-4 at.% Nb) was developed to meet this need. The Cr2Nb precipitates formed in the alloy strengthen the Cu matrix by impeding dislocation motion and inhibiting grain growth. GRCop-84 has been produced in a variety of forms

  each with a unique processing history. The creep properties of the various forms were compared

  and results demonstrated that processing had a statistically significant

  quantifiable effect upon the creep properties of GRCop-84. The differences in creep properties could largely be explained by texture

  testing environment and scatter of the test results. Even with the statistical differences

  GRCop-84 did not show grossly different creep results as a function of processing

  indicating that any of the processing methods would be suitable for producing a rocket engine liner.

  A Statistical Study of The Effects of Processing Upon the Creep Properties of GRCop-84

  Jeffery C. Gibeling

  Anita Garg

  Lawrence G. Vetraino (primary author)

  The particle-strengthened Cu–8 at.%Cr–4 at.%Nb alloy is processed by consolidation of atomized powders followed by extrusion to obtain bars and rolling to produce sheets. Comparison of copper matrix grain and second-phase particle structures in both extruded and rolled Cu–8Cr–4Nb was performed. Extruded material displayed locally banded arrangements of Cr2Nb particles

  while the distribution of particles was more uniform in rolled material. Mean Cr2Nb particle sizes were found to be essentially the same for both processing methods. Non-spherical particles in the extruded alloy showed some preferred orientation

  whereas the rolled material displayed a more uniform particle orientation distribution. Extruded material exhibited a dual grain size distribution with smaller grains in banded regions. The mean grain size of 1.36 lm in extruded material was larger than the 0.65 lm grain size of rolled material. A [101] texture was evident in extruded material

  whereas the rolled material was only slightly textured along the [001] and [111] directions. The processing differences for the rolled and extruded forms give rise to different microstructures and hence higher creep strength for the extruded material in the temperature range of 773–923 K.

  Influence of Processing on the Microstructure of Cu-8Cr-4Nb

  Michael Mills

  michael uchicM

  Hamish Fraser

  Paul Shade

  John Sosa

  Focused ion beam (FIB) based serial sectioning was utilized to characterize the morphology of two high angle grain boundaries (HAGB) in a nickel based superalloy

  one that experienced grain boundary sliding (GBS) and the other experienced strain accumulation

  during elevated temperature constant stress loading conditions. A custom script was utilized to serial section and collect ion-induced secondary electron images from the FIB-SEM system. The MATLAB based MIPARTM software was utilized to align

  segment and reconstruct 3D volumes from the sectioned images. Analysis of the 3D data indicates that the HAGB that exhibited GBS had microscale curvature that was planar in nature

  and local serrations on the order of ±150 nm. In contrast

  the HAGB that exhibited strain accumulation was not planar and had local serrations an order of magnitude greater than the other grain boundary. It is hypothesized that the serrations and the local grain boundary network are key factors in determining which grain boundaries experience GBS during creep deformation.

  The potential link between high angle grain boundary morphology and grain boundary deformation in a nickel-based superalloy

  Enrique J. Lavernia

  The cyclic deformation behavior of cryomilled AA5083 alloys was compared to that of conventional AA5083-H131. The materials studied were a 100% cryomilled alloy with a Gaussian grain size average of 315 nm and an alloy created by mixing 85% cryomilled powder with 15% unmilled powder before consolidation to fabricate a plate with a bimodal grain size distribution with peak averages at 240 nm and 1.8 μm. Although the ultra-fine grained alloys exhibited considerably higher tensile strengths than those of the conventional material

  the results from plastic strain controlled low cycle fatigue tests demonstrate that all three materials exhibit identical fatigue lives across a range of plastic strain amplitudes. The cryomilled materials exhibited softening during the first cycle

  similar to other alloys produced by conventional powder metallurgy

  followed by continual hardening to saturation before failure. The results reported in this study show that fatigue deformation in the cryomilled material is accompanied by slight grain growth

  pinning of dislocations at the grain boundaries and grain rotation to produce macroscopic slip bands which localize strain

  creating a single dominant fatigue crack. In contrast

  the conventional alloy exhibits a cell structure and more diffuse fatigue damage accumulation.

  Low Cycle Fatigue of Ultra-Fine Grained Cryomilled 5083 Aluminum Alloy

  Lawrence G. Vettraino

  The particle-strengthened Cu-8 at.%Cr-4 at.%Nb alloy is processed by consolidation of atomized powders followed by extrusion to obtain bars and rolling to produce sheets. Comparison of copper matrix grain and second-phase particle structures in both extruded and rolled Cu-8Cr-4Nb was performed. Extruded material displayed locally banded arrangements of Cr2Nb particles

  while the distribution of particles was more uniform in rolled material. Mean Cr2Nb particle sizes were found to be essentially the same for both processing methods. Non-spherical particles in the extruded alloy showed some preferred orientation

  whereas the rolled material displayed a more uniform particle orientation distribution. Extruded material exhibited a dual grain size distribution with smaller grains in banded regions. The mean grain size of 1.36 mu m in extruded material was larger than the 0.65 mu m grain size of rolled material. A [101] texture was evident in extruded material

  whereas the rolled material was only slightly textured along the [001] and [111] directions. The processing differences for the rolled and extruded forms give rise to different microstructures and hence higher creep strength for the extruded material in the temperature range of 773-923 K.

  The Influence of Post-Processing on Creep and Microstructure of Rolled Cu-8Cr-4Nb

  A look at techniques different members of the Academic community can employ to promote a healthy work environment for graduate students

  The Elephant in the Room: Where is the Empathy in Science?

  Michael J. Mills

  in situ surface deformation measurement techniques were applied to characterize strain localization sites in nickel-based superalloys when tested under constant load at 700C. Deformation maps were coupled with electron backscatter diffraction (EBSD) measurement of grain location and orientation to correlate localization sites with underlying surface microstructure. Superalloy René-104 was heat treated and quenched to create two microstructures with similar grain sizes but different grain boundary character: the standard microstructure had microscopically planar grain boundaries

  and the other microstructure had serrated grain boundaries. Analysis of full-field strain maps calculated from in situ scanning electron microscopy (SEM) images indicated distinct differences in strain localization as a function of total strain for the two microstructures. The standard microstructure showed very little intra-granular strain accumulation

  and annealing twin boundaries played an important role in strain localization sites

  whereas the serrated microstructure experienced strain accumulation more evenly throughout the microstructure. Grain boundary sliding (GBS) was observed in both microstructures

  but the development of serrated grain boundaries significantly decreased the contribution of this mechanism to the overall strain accommodation from 20% to 14% of the total plastic strain being accommodated by GBS.

  Characterization of Localized Deformation Near Grain Boundaries of Superalloy René-104 at Elevated Temperature

  Jeffery L. Clounch

  Arthur C. Nunes

  Study of Radiographic Linear Indications and Subsequent Microstructural Features in Gas Tungsten Arc Welds of Inconel 718

  Friction Stir Welding of GRCop-84

  Michael Mills

  Robert Wheeler

  An experimental methodology has been developed to characterize local strain heterogeneities in alloys via in-situ scanning electron microscope (SEM) based mechanical testing. Quantitative measurements of local strains as a function of grain orientation

  morphology and neighborhood are crucial for mechanistic understanding and validation of crystal plasticity models. This study focuses on the technical challenges associated with performing creep tests at elevated temperatures ≤700°C in an SEM. Samples of nickel superalloy Rene 104 were used for this study

  but the technique is applicable to testing of any metal samples at elevated temperature. Electron beam lithography was employed to produce a suitable surface speckle pattern of hafnium oxide to facilitate full field displacement measurements using a commercial software package. The speckle pattern proved to have good thermal stability and provided excellent contrast for image acquisition using secondary electron imaging at elevated temperature. The speckle pattern and microscope magnification were optimized to obtain the resolution necessary to discern strain localizations within grain interiors and along grain boundaries. Minimum strain resolution due to SEM image distortions was determined prior to tensile testing

  and image integration methods were utilized to minimize imaging artifacts. Limitations due to the present specimen heating method and potential solutions to these limitations are also addressed.

  In-situ Mechanical Testing for Characterizing Strain Localization during Deformation at Elevated Temperatures

  Michael Mills

  Hamish Fraser

  Yunzhi Wang

  Adam Pilchak

  Paul Shade

  John Sosa

  Characterization of Strain Accumulation at Grain Boundaries of Nickel-based Superalloys

  The research goal is to test the hypothesis that statistical data analytics can lead to a versatile design paradigm for the manufacturing of interface-rich materials for particular performance requirements. The predictive capabilities of these data-derived models will be assessed for Inconel-706 a forged Ni-based superalloy

  with the performance metrics of high temperature strength and low cycle fatigue life. This alloy is significant for the manufacturing of efficient energy harvesting applications. The data for this research includes manufacturing

  mesostructure and performance measures from legacy data obtained over the past 10 years by Alcoa Forging Research Group. The research team will test this hypothesis by cultivating an open

  robust

  data infrastructure that goes beyond a simple electronic \"filing cabinet\" and allows for seamless access to the data by analysis tools and allows for the analysis results to also be stored with all the associated metadata. Exploratory data analysis will guide the team in determining what additional datasets are needed to increase the statistical validity of the data-derived models. This research program supports broader efforts of the Material Science community through both the Materials Genome Initiative and Integrated Computational Materials Engineering by producing a robust

  open-source data framework

  which is generalizable to manufacturing routes of other interface-rich materials.

  Transmission Kikuchi Diffraction (TKD) in SEM

  Maryam Zahiri Azar

  Shenjia Zhang

  Jennifer

  Carter

  NASA-Marshall Space Flight Center

  contracted via Universities Space Research Association

  NASA Marshall Space Flight Center

  contracted via Universities Space Research Association

  UC Davis

  Case Western Reserve University

  The Ohio State University

  UC Davis

  NASA-Marshall Space Flight Center

  contracted via Universities Space Research Association

  Metals Engineering Branch

  In this position I supported development of heat treatment procedures for D6AC steel for the Ares I First Stage Solid Rocket Booster project. I also assessed corrosion properties of conversion coated and uncoated aluminum alloys (AA2014

  AA2219

  and AA2195) for the Ares I Upper Stage project.

  Engineering Intern

  NASA-Marshall Space Flight Center

  contracted via Universities Space Research Association

  Depart. of Chemical and Material Science and Engineering

  Dr. Jeffery Gibeling

  My MS research concentrated on assessing how microstructural variations in ultra-fine grained AA5083 effect low cycle fatigue properties. This work focused on developing a new ballistic resistant aluminum alloy using severe plastic deformation processing. In this work I collaborated with researchers at Los Alamos National Laboratory to texture analysis via EBSD prior to conducting fatigue testing.

  Graduate Research Assistant

  UC Davis

  Metals Engineering Branch

  During this internship I performed a material selection and design study for the anvil on a High Speed Friction Stir Welding system. The anvil was used to weld a particle strengthened copper alloy (GRCop-84).

  Engineering Intern

  NASA Marshall Space Flight Center

  contracted via Universities Space Research Association

  Metals Engineering Branch

  I determined a method of validating weld defects from radiographic indications in Inconel 718 TIG welds used on the Space Shuttle Main Propulsion System. My duties included developing a design of experiment

  conducting the experiments on an automated TIG welder

  and analyzing radiographic and optical microscopy images. The final work was published as a guideline for manufacturing.

  Engineering Intern

  NASA-Marshall Space Flight Center

  contracted via Universities Space Research Association

  Department of Material Science and Engineering

  Dr Michael Mills

  My PhD research has focused on assessing grain-scale deformation mechanisms in polycrystalline Ni-based superalloys. This research emphasizes the use of digital image correlation (DIC) and site-specific TEM analysis to characterize deformation mechanisms at the grain boundaries of Ni-based superalloys. DIC of in-situ SEM images creates full field deformation maps to assess sub-grain size (<20μm) strain localizations during elevated temperature creep environments. To accomplish DIC a speckle pattern was adhered to the specimen surface utilizing clean-room sample preparation techniques in a novel fashion. This work was done in close collaboration with engineers at Wright Patterson Air Force Base.

  Graduate Research Assistant

  The Ohio State University

  Assistant Professor

  Cleveland/Akron

  Ohio Area

  Case Western Reserve University

  Dept. of Chemical and Materials Science and Engineering

  Dr. Jeffery Gibeling

  As an undergraduate research assistant I performed a study of how microstructural characteristics effect creep properties of a particle strengthened copper alloy. Work included sample preparation for electron microscopy analysis

  conducting texture analysis via EBSD

  and performing creep tests and analyzing the resulting data.

  Undergraduate Research Assistant

  UC Davis

  2014-2016: TMS Women in Materials Science and Engineering Chairperson

  volunteer

  TMS

  MRS

  volunteer

  ASM

  The PECASE is the highest honor bestowed by the United States Government to outstanding scientists and engineers who are beginning their independent research careers and who show exceptional promise for leadership in science and technology.\n\nEstablished in 1996

  the PECASE acknowledges the contributions scientists and engineers have made to the advancement of science

  technology

  education

  and mathematics (STEM) education and to community service as demonstrated through scientific leadership

  public education

  and community outreach. The White House Office of Science and Technology Policy coordinates the PECASE with participating departments and agencies.\n\nhttps://www.whitehouse.gov/briefings-statements/president-donald-j-trump-announces-recipients-presidential-early-career-award-scientists-engineers/

  White House Office of Science and Technology Policy

  NSF

  Future Faculty Grant

  Academic Keys

  Poster Presenter Winner

  Physical Metallurgy Gordon Research Conference

  Henry DeWitt Smith Scholarship

  The principal aim and purpose of this scholarship fund is to further the mineral industries by affording educational opportunities in the arts and sciences pertaining to those industries

  particularly by assisting worthy students in the mining

  metallurgical and petroleum departments of leading colleges and universities which confer degrees in mineral engineering.

  AIME

  National Neutron X-Ray Scattering School

  Acceptance into the 14th annual school on neutron and x-ray scattering techniques. A two week intensive course on theory and experimental techniques at the Advanced Photon Source

  and the Spallation Neutron Source and the High Flux Isotope Reactor.

  DOE: Argonne and Oak Ridge National Laboratories

  Graduate Excellence in Materials Science Sapphire Award

  American Ceramic Society

  MS&T

  Young Leader

  The TMS Young Leaders Professional Development Award was created to enhance the professional development of dynamic young people from TMS’s five technical divisions by helping them participate in Society activities

  become better acquainted

  make important contacts with TMS leaders

  and network with prominent Society members.

  TMS: Structural Materials Division

  member

  For exceptional character and academic performance

  Tau Beta Pi

  TMS International Young Leader

  The Japan Institute of Metals (JIM) and the Federation of European Materials Societies (FEMS) established joint Young Leaders International Scholar Programs with TMS to promote young member activities and strengthen the collaborations between TMS and these two international societies. These collaborations have resulted in exchange programs

  which offer select young members the opportunity to present papers at international sessions.\n\nTMS

  FEMS

  and JIM identify one or more young leaders to travel to the other organization's meeting to present a paper. The chosen International Scholars also spend a few days visiting select industrial facilities

  research labs

  or universities. On their return

  they are required to write an article about their experiences for their host organization's publication. The host organization supports the scholars

  in part

  during their stay overseas with complimentary meeting registration and financial/non-financial assistance as necessary. FEMS holds a five-day EUROMAT Conference every two years in September with presentations of about 2

  000 papers in total. In the even years

  FEMS holds a five-day Junior EUROMAT in July in Lausanne with presentations of about 350 papers. The TMS scholar to FEMS will attend the Euromat meeting in odd-numbered years.

  TMS Membership & Student Development Committee