@conference {1596, title = {3D Characterization of the Columnar-to-Equiaxed Transition in Additively Manufactured Inconel 718}, booktitle = {Superalloys 2020}, year = {2020}, publisher = {Springer International Publishing}, organization = {Springer International Publishing}, abstract = {

Additive manufacturing (AM) provides enormous process- ing flexibility, enabling novel part geometries and opti- mized designs. Access to a local heat source further per- mits the potential for local microstructure control on the scale of individual melt pools, which can enable local con- trol of part properties. In order to design tailored process- ing strategies for target microstructures, models predict- ing the columnar-to-equiaxed transition must be extended to the high solidification velocities and complex thermal histories present in AM. Here, we combine 3D charac- terization with advanced modeling techniques to develop a more complete understanding of the solidification pro- cess and evolution of microstructure during electron beam melting (EBM) of Inconel 718. Full calibration of existing microstructure prediction models demonstrates the differ- ences between AM processes and more conventional weld- ing techniques, underlying the need for accurate deter- mination of key parameters that can only be measured directly in 3D. The ability to combine multisensor data in a consistent 3D framework via data fusion algorithms is essential to fully leverage these advanced characteriza- tion approaches. Thermal modeling provides insight on microstructure development within isolated solidification events and demonstrates the role of Marangoni effects on controlling solidification behavior.

}, keywords = {Additive manufacturing, Microstructure, Solidification, Tomography}, isbn = {9783030518349}, doi = {10.1007/978-3-030-51834-9}, url = {http://dx.doi.org/10.1007/978-3-030-51834-9_65}, author = {Polonsky, Andrew T. and Raghavan, Narendran and Echlin, Mclean P. and Kirka, Michael M. and Dehoff, Ryan R. and Pollock, Tresa M.}, editor = {Tin, Sammy and Hardy, Mark and Clews, Justin and Cormier, Jonathan and Feng, Qiang and Marcin, John and O{\textquoteright}Brien, Chris and Suzuki, Akane} } @article {1336, title = {Accelerated discovery of oxidation resistant CoNi-base γ/γ{\textquoteright} alloys with high L12 solvus and low density}, journal = {Materials and Design}, volume = {189}, year = {2020}, pages = {1{\textendash}12}, abstract = {

A systematic and accelerated methodology for alloy design is demonstrated by combining combinatorial synthesis, high-throughput oxide scale characterization, computational density functional theory, and CALPHAD database calculations. By applying this strategy to the senary Co-Ni-W-Al-Cr-Ta material system, a novel \γ/\γ\&$\#$39; alloy exhibiting a superior combination of properties has been identified. Properties include a \γ\&$\#$39; solvus near 1200 \°C, continuous \α-Al2O3 scale formation after 1 h in air at 1100 \°C, and comparable density to 2nd-generation commercial Ni-base superalloys. This novel alloy SB-CoNi-10 has a nominal composition of 39.8Co \– 36.5Ni \– 13.2Al \– 1.0W \– 6.0Cr \– 3.5Ta at.\%, and its properties are compared with other recently studied Co-, CoNi-, and Ni-base \γ/\γ\&$\#$39; alloys.

}, keywords = {Alloy design, Cobalt-base superalloys, Combinatorial synthesis, Oxidation, Superalloys}, issn = {18734197}, doi = {10.1016/j.matdes.2019.108445}, author = {Stewart, Colin A. and Murray, Sean P. and Suzuki, Akane and Pollock, Tresa M. and Levi, Carlos G.} } @conference {1611, title = {Creep, Fatigue, and Oxidation Interactions During High and Very High Cycle Fatigue at Elevated Temperature of Nickel-Based Single Crystal Superalloys}, booktitle = {Superalloys 2020}, year = {2020}, abstract = {

High-temperature fatigue of Ni-based single crystal superalloys is studied at 1000 \°C in a wide range of loading conditions (\−1 ? R ? 0.8) and number of cycles (103 \− 109). Under fully reversed conditions, a competition between crack initiations from the surface\— assisted by oxidation\—and from internal metallurgical defects\—mostly large casting pores\—is observed. Increasing the testing frequency shifts the competition to a higher number of cycles. Conversely, decreasing the casting pore size or coating the specimen promotes surface initiations. When a positive mean stress is added (R ? 0), a creep deformation/damage mechanism mainly controls fatigue life, despite fracture surfaces presenting a variety of initiation types. Fatigue life can be predicted by a simple creep law if the contribution of the alternating stress is considered. A linear damage summation method that considers pure fatigue and pure creep damage is used to predict the fatigue lives, and Haigh diagrams for different alloys are presented.

}, keywords = {Creep, fatigue, High temperature, Superalloy}, isbn = {9783030518349}, doi = {10.1007/978-3-030-51834-9}, url = {http://dx.doi.org/10.1007/978-3-030-51834-9_65}, author = {Cervellon, A. and Yi, J. Z. and Corpace, F. and Hervier, Z. and Rigney, J. and Wright, P. K. and Torbet, C. J. and Cormier, J. and Jones, J. W. and Pollock, T. M.}, editor = {Tin, Sammy and Hardy, Mark and Clews, Justin and Cormier, Jonathan and Feng, Qiang and Marcin, John and O{\textquoteright}Brien, Chris and Suzuki, Akane} } @conference {1591, title = {Microstructure and Tensile Properties of a CoNi-Based Superalloy Fabricated by Selective Electron Beam Melting}, booktitle = {Superalloys 2020}, year = {2020}, publisher = {Springer International Publishing}, organization = {Springer International Publishing}, abstract = {

Successful application of selective electron beam melting to a novel CoNi-based superalloy named SB-CoNi-10 is demonstrated. Crack-free as-printed microstructures exhibit excellent ductilities above 30\% and ultimate tensile strengths above 1.1 GPa at room temperature in tension. Conventional post-processing consisting of a super-solvus hot isostatic pressing (HIP), a solution heat treatment (SHT), and a low-temperature aging has been applied to remove microstructural inhomogeneities present in the as-printed microstructure. The microstructures of the as-printed and HIP+SHT+Aged alloys have been investigated to determine the effect of post-processing heat treatments on the nanoscale \γ/\γ\&$\#$39; microstructure and the mesoscale grain structure. Tensile tests have been conducted at room temperature and elevated temperatures above 850 {\textopenbullet}C to investigate mechanical properties in both the as-printed and HIP+SHT+Aged conditions. The high- temperature ductility and strength are strongly affected by the microstructure, with a mostly columnar-grained microstructure in the as-printed condition exhibiting superior ductility to the fully recrystallized microstructure in the HIP+SHT+Aged condition.

}, keywords = {Additive manufacturing, CoNi-based superalloys, Mechanical properties}, isbn = {9783030518349}, doi = {10.1007/978-3-030-51834-9}, url = {http://dx.doi.org/10.1007/978-3-030-51834-9_65}, author = {Murray, Sean P. and Pusch, Kira M. and Polonsky, Andrew T. and Torbet, Chris J. and Seward, Gareth G. E. and Nandwana, Peeyush and Kirka, Michael M. and Dehoff, Ryan R. and Zhou, Ning and Forsik, St{\'e}phane A. J. and Slye, William and Pollock, Tresa M.}, editor = {Tin, Sammy and Hardy, Mark and Clews, Justin and Cormier, Jonathan and Feng, Qiang and Marcin, John and O{\textquoteright}Brien, Chris and Suzuki, Akane} } @conference {1606, title = {Role of Non-metallic Inclusions and Twins on the Variability in Fatigue Life in Alloy 718 Nickel Base Superalloy}, booktitle = {Superalloys 2020}, year = {2020}, publisher = {Springer International Publishing}, organization = {Springer International Publishing}, abstract = {

Non-metallic inclusions (NMIs) and slip bands parallel to and slightly offset from twin boundaries are observed to be preferential sites for fatigue crack nucleation in wrought superalloys. Potential interactions between NMI cracking and slip activity within neighboring grains or at twin boundaries were investigated under monotonic tensile loading (up to 1.3\% total strain) at room temper- ature. High resolution- and Heaviside-digital image correlation measurements were performed during inter- rupted tensile loading to identify strain localization, associated slip systems, and damage initiation. Different mechanisms and scenarios were identified: (1) Microplas- ticity generally starts at twin boundaries even at stresses as low as 70\% of the macroscopic yield strength, (2) transgranular slip activity intensively develops above the macroscopic yield stress, (3) intense slip activity develops near and parallel to 21\% of the twin boundaries intercepting NMIs, (4) 7\% of the twin boundaries inter- cepting NMIs lead to slip-assisted NMI cracking, (5) no transgranular slip activity participates in NMI cracking, (6) the fraction of cracked NMIs progressively increases with the load, and (7) within the NMIs that initiated cracks, 67\% cracked below 90\% of the macroscopic yield strength without the presence of slip activity in the neighboring grains. While slip-assisted NMI cracking was evidenced in the present study, most NMI cracking is due to strain incompatibility between NMIs and neighboring grains at the high end of the elastic regime without slip interaction.

}, keywords = {fatigue, High Resolution-Digital Image Correlation (HR-DIC), In-situ tensile testing, Non-metallic inclusions (NMIs), Twin boundary}, isbn = {9783030518349}, doi = {10.1007/978-3-030-51834-9}, url = {http://dx.doi.org/10.1007/978-3-030-51834-9_65}, author = {Texier, Damien and Stinville, Jean-Charles and Charpagne, Marie-agathe and Chen, Zhe and Valle, Valery and Villechaise, Patrick and Pollock, Tresa M. and Cormier, Jonathan}, editor = {Tin, Sammy and Hardy, Mark and Clews, Justin and Cormier, Jonathan and Feng, Qiang and Marcin, John and O{\textquoteright}Brien, Chris and Suzuki, Akane} } @conference {1616, title = {Tuning Strain Localization in Polycrystalline Nickel-Based Superalloys by Thermomechanical Processing}, booktitle = {Superalloys 2020}, year = {2020}, publisher = {Springer International Publishing}, organization = {Springer International Publishing}, abstract = {

Thermomechanical processing routes are used to produce microstructures that minimize plastic strain localization at the sub-grain scale in a polycrystalline \γ \− \γ\&$\#$39; nickel- based superalloy. This novel approach is made possible by the use of innovative experimental tools and statistical data analysis that capture slip events over large represen- tative fields of view. Results are correlated to conventional observations of fatigue crack initiation and early stage of propagation. The effect of coherent twin boundaries and primary \γ\&$\#$39; precipitates on fatigue properties and plastic localization is detailed.

}, keywords = {3D microstructure, Annealing twin boundaries, Nickel-based superalloy, Primary γ{\textquoteright} precipitates, Slip bands}, isbn = {9783030518349}, doi = {10.1007/978-3-030-51834-9}, url = {http://dx.doi.org/10.1007/978-3-030-51834-9_65}, author = {Charpagne, M. A. and Stinville, J. C. and Polonsky, A. T. and Echlin, M. P. and Murray, S. P. and Chen, Z. and Bozzolo, N. and Cormier, J. and Valle, V. and Pollock, T. M.}, editor = {Tin, Sammy and Hardy, Mark and Clews, Justin and Cormier, Jonathan and Feng, Qiang and Marcin, John and O{\textquoteright}Brien, Chris and Suzuki, Akane} } @conference {1601, title = {The Yield Strength Anomaly in Co-Ni Design Space}, booktitle = {Superalloys 2020}, year = {2020}, publisher = {Springer International Publishing}, organization = {Springer International Publishing}, abstract = {

A new computational approach to model precipitate compositions and properties in the CoNi-design space for yield strength anomaly prediction is presented. The antiphase boundary (APB) energies on {111} and {010} and the degree of elastic anisotropy are known to influence the yield strength anomaly. APB energies were estimated by a diffuse multi-layer fault (DMLF) model using the structural energies of proximate structures: L12, ca\′, and D023. The elastic moduli were calculated via the energy-strain approach using density functional theory calculations. (Ni1\−xCox)3(Al1\−yWy) was chosen as the model system, and Yoo\&$\#$39;s criterion is evaluated over the entire range ofcompositions to identify regions that exhibit the yield strength anomaly. (Ni0.65Co0.35)3(Al0.5W0.5) has the maximum APB (111) and any two-phase alloy (c + c') in Ni\–Co\–Al\–W system with this precipitate composition might exhibit higher strength upon shearing by a matrix dislocation. ThermoCalc was employed to identify stable L12 regions in (Ni1\−xCox)3(Al1\−yWy). The effect of Co on the yield strength anomaly was investigated experimen- tally in three (Ni1\−xCox)3Al alloys with L12 structure. All three alloys exhibited the yield strength anomaly, validat- ing the computational approach. The addition of Co provides solid solution strengthening to Ni3Al at room temperature; however, this contribution to the overall strength diminished as a function of temperature. CoNi-alloys displayed strengths similar to Ni3Al at elevated temperatures with Co addition resulting in a marginal increase in strength at the peak temperature. The present study elucidates that APB energies from a DMLF model combined with elastic moduli can be employed to predict yield strength anomaly using Yoo\&$\#$39;s criteria.

}, keywords = {Antiphase boundaries, CoNi-based superalloys, Yield strength anomaly}, isbn = {9783030518349}, doi = {10.1007/978-3-030-51834-9}, url = {http://dx.doi.org/10.1007/978-3-030-51834-9_65}, author = {Vamsi, K. V. and Murray, Sean P. and Pollock, Tresa M.}, editor = {Tin, Sammy and Hardy, Mark and Clews, Justin and Cormier, Jonathan and Feng, Qiang and Marcin, John and O{\textquoteright}Brien, Chris and Suzuki, Akane} } @article {1391, title = {Oxidation Behavior Across Composition Space Relevant to Co-based γ/γ' Alloys}, journal = {Metallurgical and Materials Transactions A}, volume = {50}, year = {2019}, pages = {5445{\textendash}5458}, issn = {1073-5623}, doi = {10.1007/s11661-019-05413-8}, url = {https://doi.org/10.1007/s11661-019-05413-8}, author = {Stewart, Colin A. and Suzuki, Akane and Rhein, Robert K. and Pollock, Tresa M. and Levi, Carlos G.} } @article {1321, title = {Rapid Assessment of Oxidation Behavior in Co-Based γ/γ' Alloys}, journal = {Oxidation of Metals}, volume = {90}, year = {2018}, pages = {485{\textendash}498}, keywords = {Cobalt-base superalloys, Combinatorial synthesis, Oxidation, Photostimulated luminescence spectroscopy}, isbn = {0030-770X}, issn = {0030770X}, doi = {10.1007/s11085-018-9849-2}, url = {https://doi.org/10.1007/s11085-018-9849-2}, author = {Stewart, Colin A. and Suzuki, Akane and Pollock, Tresa M. and Levi, Carlos G.} } @article {jorgensen2016bond, title = {Bond coatings with high rumpling resistance: Design and characterization}, journal = {Surface and Coatings Technology}, volume = {300}, year = {2016}, pages = {25{\textendash}34}, publisher = {Elsevier}, author = {Jorgensen, David J and Suzuki, Akane and Lipkin, Don M and Pollock, Tresa M} } @article {titus2015creep, title = {Creep-induced planar defects in L1 2-containing Co-and CoNi-base single-crystal superalloys}, journal = {Acta Materialia}, volume = {82}, year = {2015}, pages = {530{\textendash}539}, publisher = {Pergamon}, author = {Titus, Michael S and Eggeler, Yolita M and Suzuki, Akane and Pollock, Tresa M} } @article {titus2015high, title = {High resolution energy dispersive spectroscopy mapping of planar defects in L1 2-containing co-base superalloys}, journal = {Acta Materialia}, volume = {89}, year = {2015}, pages = {423{\textendash}437}, publisher = {Pergamon}, author = {Titus, Michael S and Mottura, Alessandro and Viswanathan, G Babu and Suzuki, Akane and Mills, Michael J and Pollock, Tresa M} } @article {suzuki2015l12, title = {L12-Strengthened Cobalt-Base Superalloys}, journal = {Annual Review of Materials Research}, volume = {45}, year = {2015}, pages = {345{\textendash}368}, publisher = {Annual Reviews}, author = {Suzuki, Akane and Inui, Haruyuki and Pollock, Tresa M} } @article {eggeler2014creep, title = {Creep deformation-induced antiphase boundaries in L1 2-containing single-crystal cobalt-base superalloys}, journal = {Acta Materialia}, volume = {77}, year = {2014}, pages = {352{\textendash}359}, publisher = {Pergamon}, author = {Eggeler, Yolita M and Titus, Michael S and Suzuki, Akane and Pollock, Tresa M} } @conference {suzuki2014oxide, title = {Oxide-assisted crack growth in hold-time low-cycle-fatigue of single-crystal superalloys}, booktitle = {MATEC Web of Conferences}, volume = {14}, year = {2014}, pages = {04004}, publisher = {EDP Sciences}, organization = {EDP Sciences}, author = {Suzuki, Akane and Gao, Yan and Lipkin, Don and Singhal, Anjali and Krug, Matthew and Konitzer, Douglas and Almer, Jonathan and Pollock, Tresa and Bewlay, Bernard} } @article {titus2014sub, title = {Sub-nanometer Resolution Chemi-STEM EDS Mapping of Superlattice Intrinsic Stacking Faults in Co-based Superalloys}, journal = {Microscopy and Microanalysis}, volume = {20}, number = {S3}, year = {2014}, pages = {1028{\textendash}1029}, publisher = {Cambridge University Press}, author = {Titus, Michael S and Suzuki, Akane and Mills, Michael J and Pollock, Tresa M} } @article {titus2012creep, title = {Creep and directional coarsening in single crystals of new $\gamma${\textendash}$\gamma$' cobalt-base alloys}, journal = {Scripta Materialia}, volume = {66}, number = {8}, year = {2012}, pages = {574{\textendash}577}, publisher = {Elsevier}, author = {Titus, Michael S and Suzuki, Akane and Pollock, Tresa M} } @article {titus2012high, title = {High Temperature Creep of New L12 Containing Cobalt-Base Superalloys}, journal = {Superalloys 2012}, year = {2012}, pages = {823{\textendash}832}, publisher = {Wiley Online Library}, author = {Titus, Michael S and Suzuki, Akane and Pollock, Tresa M} } @article {pollock2011oxide, title = {Oxide-Assisted Degradation of Ni-Base Single Crystals During Cyclic Loading: the Role of Coatings}, journal = {Journal of the American Ceramic Society}, volume = {94}, number = {s1}, year = {2011}, publisher = {Blackwell Publishing Inc}, author = {Pollock, Tresa M and Laux, Britta and Brundidge, Clinique L and Suzuki, Akane and He, Ming Y} } @article {tsunekane2011single, title = {Single-crystal solidification of new Co{\textendash}Al{\textendash}W-base alloys}, journal = {Intermetallics}, volume = {19}, number = {5}, year = {2011}, pages = {636{\textendash}643}, publisher = {Elsevier}, author = {Tsunekane, Masafumi and Suzuki, Akane and Pollock, Tresa M} } @article {terbush2008dislocation, title = {Dislocation substructures of three die-cast Mg{\textendash}Al{\textendash}Ca-based alloys}, journal = {Scripta Materialia}, volume = {58}, number = {10}, year = {2008}, pages = {914{\textendash}917}, publisher = {Pergamon}, author = {TerBush, JR and Suzuki, Akane and Saddock, ND and Jones, JW and Pollock, TM} } @article {suzuki2008high, title = {High-temperature strength and deformation of $\gamma$/$\gamma$' two-phase Co{\textendash}Al{\textendash}W-base alloys}, journal = {Acta Materialia}, volume = {56}, number = {6}, year = {2008}, pages = {1288{\textendash}1297}, publisher = {Elsevier}, author = {Suzuki, Akane and Pollock, Tresa M} } @article {suzuki2008precipitation, title = {Precipitation strengthening of a Mg-Al-Ca{\textendash}based AXJ530 die-cast alloy}, journal = {Metallurgical and Materials Transactions A}, volume = {39}, number = {3}, year = {2008}, pages = {696{\textendash}702}, publisher = {Springer US}, author = {Suzuki, Akane and Saddock, ND and TerBush, JR and Powell, BR and Jones, JW and Pollock, TM} } @article {suzuki2007effect, title = {Effect of Sr additions on the microstructure and strength of a Mg-Al-Ca ternary alloy}, journal = {Metallurgical and Materials Transactions A}, volume = {38}, number = {2}, year = {2007}, pages = {420{\textendash}427}, publisher = {Springer US}, author = {Suzuki, Akane and Saddock, ND and Riester, L and Lara-Curzio, E and Jones, JW and Pollock, TM} } @article {suzuki2007flow, title = {Flow stress anomalies in $\gamma$/$\gamma$' two-phase Co{\textendash}Al{\textendash}W-base alloys}, journal = {Scripta Materialia}, volume = {56}, number = {5}, year = {2007}, pages = {385{\textendash}388}, publisher = {Elsevier}, author = {Suzuki, Akane and DeNolf, Garret C and Pollock, Tresa M} } @conference {suzuki2007high, title = {High Temperature Strength of Co-based gamma/gamma{\textquoteright} Superalloys}, booktitle = {Advanced Intermetallic-Based Alloys(MRS Symposium Proceedings Series Volume 980)}, volume = {980}, year = {2007}, pages = {499{\textendash}504}, author = {Suzuki, Akane and DeNolf, Garret C and Pollock, Tresa M} } @booklet {saddock2007permanent, title = {Permanent Mold Casting and Creep Behavior of Mg-4 Al-4 X:(Ca, Ce, La, Sr) Alloys}, year = {2007}, publisher = {SAE Technical Paper}, author = {Saddock, Nicholas D and Suzuki, Akane and TerBush, Jessica R and Jones, J Wayne and Pollock, Tresa M and Zindel, Jake and Allison, John E} } @conference {suzuki2006high, title = {High Temperature Strength of Co-based $\gamma$/$\gamma${\textquoteright}Superalloys}, booktitle = {MRS Proceedings}, volume = {980}, year = {2006}, pages = {0980{\textendash}II08}, publisher = {Cambridge University Press}, organization = {Cambridge University Press}, author = {Suzuki, Akane and DeNolf, Garret C and Pollock, Tresa M} } @conference {saddock2006microstructure, title = {Microstructure and mechanical properties of permanent mold cast Mg-4 A1-4 (Ca, Ce, La, or Sr) ternary alloys}, booktitle = {Symposium on Magnesium Technology 2006 (TMS 12 March 2006 to 16 March 2006)}, year = {2006}, pages = {77{\textendash}82}, publisher = {The Minerals, Metals \& Materials Society (TMS)}, organization = {The Minerals, Metals \& Materials Society (TMS)}, author = {Saddock, Nicholas and Suzuki, Akane and TerBush, Jessica and Heininger, Eric and Zindel, Jacob and Allison, John and Pollock, Tresa and Jones, J} } @article {suzuki2006phase, title = {Phase equilibria in the Mg-Al-Ca ternary system at 773 and 673 K}, journal = {Metallurgical and Materials Transactions A}, volume = {37}, number = {3}, year = {2006}, pages = {975{\textendash}983}, publisher = {Springer}, author = {Suzuki, Akane and Saddock, Nicholas D and Jones, J Wayne and Pollock, Tresa M} } @article {suzuki2005phase, title = {Phase Transformation and Creep of Mg-Al-Ca Based Die-Cast Alloys}, journal = {Essential Readings in Magnesium Technology}, year = {2005}, pages = {291{\textendash}296}, publisher = {John Wiley \& Sons, Inc.}, author = {Suzuki, Akane and Saddock, Nicholas D and Jones, J Wayne and Pollock, Tresa M} }