Progress towards Understanding the Synthesis and Behavior of Metals Far from Equilibrium: A SMD Symposium Honoring Enrique Lavernia on the Occasion of His 60th Birthday: Nanostructured Metals II
Sponsored by: TMS Structural Materials Division, TMS: Mechanical Behavior of Materials Committee, TMS: Advanced Characterization, Testing, and Simulation Committee, TMS: Composite Materials Committee
Program Organizers: Haiming Wen, Missouri University of Science and Technology; Suveen Mathaudhu, Colorado School of Mines; Yuntian Zhu, City University of Hong Kong; Manoj Gupta, National University of Singapore; Kaka Ma, Colorado State University; Troy Topping, California State University Sacramento; Yizhang Zhou, University of California, Irvine; Joshua Yee, Sandia National Laboratories; Dalong Zhang, Pacific Northwest National Laboratory; Yaojun Lin, Wuhan University of Technology; Fei Chen, Wuhan University of Technology
Monday 2:30 PM
February 24, 2020
Room: 31B
Location: San Diego Convention Ctr
Session Chair: Suveen Mathaudhu, University of California, Riverside; Yuntian Zhu, North Carolina State University
2:30 PM Invited
Sputter Deposited Nanotwinned NiMoW Alloys with Impressive Properties and Stability: Kevin Hemker1; 1Johns Hopkins University
The focus on nanoscience has greatly advanced our ability to synthesize, characterize, and model nanomaterials with unprecedented physical and chemical properties that are derived from dimensional constraints. However, challenges in bridging nano- to mesoscale fabrication and microstructural instabilities present serious obstacles to the wide spread commercialization of structural nanomaterials. Sputter deposited nanotwinned NiMoW films have been shown to possess ultrahigh mechanical strength, extreme anisotropic plasticity, low electrical resistivity, low thermal expansion, and much needed thermal and mechanical microstructural stability. Here we report on in-situ experiments to elucidate the fundamental deformation mechanisms that underpin the extreme strength and highly anisotropic deformation of nanotwinned NiMoW. Related efforts involving the fabrication of freestanding microcantilever arrays possessing the dimensional stability required for next generation metal MEMS and IoT technologies will also be discussed.
3:00 PM Invited
Trimodal Composites: An Overview: Julie Schoenung1; 1University of California, Irvine
Metal matrix composites provide a degree of design flexibility that is not attainable with homogeneous materials. Extensive research on MMC design often includes topics such as tailoring of reinforcement size, morphology and material composition. Trimodal composites, consisting of coarse grain matrix regions and ultrafine grain matrix regions embedded with hard ceramic particles, represent an interesting intersection of MMCs with nanostructured metals. In this presentation, the processing, microstructure evolution, and mechanical behavior of trimodal composites (specifically, Al alloys reinforced with boron carbide) will be reviewed. Relevant length scales range from nanoscale through macroscale, with significant emphasis on designing and understanding the role of interfaces, using both in-situ and ex-situ techniques. Performance enhancements provided by trimodal composites include not only significant increases in strength, but more importantly the ability to selectively design for desired strength and ductility combinations. Future opportunities to expand the applications for these materials will also be discussed.
3:30 PM Invited
Real Space Charge Density Imaging with Sub-Å Resolution by 4D STEM: Xiaoqing Pan1; 1University of California, Irvine
The charge density distribution in materials dictates their structure and properties. While measuring charge density of bulk materials is possible using X-ray or electron diffraction techniques, resolving charge density in inhomogeneous structures remains a great challenge. In this talk, I will present a real space imaging technique to map the local charge density between atoms using a confined electron probe of 0.6 Å in size in scanning transmission electron microscope, along with an angle resolved pixelated fast electron detector. As an example, using this technique, we directly imaged the interfacial charge distribution and ferroelectric polarization configuration at the ferroelectric/insulator heterojunction with the sub-Å resolution, and discovered electronic charge accumulated at the interface induced by the penetration of polarization field inside the insulator. The charge density imaging established in this work advances electron microscopy from detecting atoms to imaging electrons, paving a new route to study local bonding in crystalline solids.
4:00 PM Break
4:20 PM Invited
Nanotechnology Enabled Metallurgy for New Age of Metals: Xiaochun Li1; 1University of California, Los Angles
High performance metals offer tremendous potential to improve medical systems. However, conventional processing methods in metals manufacturing have reached certain limits in further improving the properties. Incorporation of nanoelements into various functional materials can obtain unusual physical, chemical, and mechanical properties. Here we show a newly discovered mechanism of nanoparticle self-dispersion and stabilization to achieve a uniform self-dispersion of nanoparticles in various metals to deliver unprecedented properties. This talk will specifically discuss about various scientific and technological aspects on how nanotechnology can be applied to break metallurgical barriers, enabling unprecedented micro/nano-structure control and property tuning in metals manufacturing. This approach of nanotechnology enabled metals manufacturing paves a revolutionary pathway for a new age of metals to meet sustainability challenges in today’s society.
4:50 PM Invited
Targeted Processing of Nanocrystalline Alloys to Elicit Nonequilibrium Interfacial States: Glenn Balbus1; Zhitong Bai2; McLean Echlin1; Tresa Pollock1; Yue Fan2; Daniel Gianola1; 1University of California, Santa Barbara; 2University of Michigan
The nonequilibrium nature of amorphous solids such as metallic glasses shares intriguing commonalities with grain boundaries in nanocrystalline materials, owing largely to the multiplicity of energy states inherent to disorder. Here, we report on studies of nanocrystalline materials and novel synthesis and processing routes for controlling the structural state – and as a consequence, the mechanical properties. We study relaxation processes at grain boundaries in nanocrystalline materials that facilitate atomic reconfigurations toward a lower energy state such as low temperature annealing, which enhance mechanical strength while promoting shear localization. A particular focus in this talk will be on strategies for rejuvenation at grain boundaries with the goal of suppressing shear localization and endowing damage tolerance. Parallels between our results and rejuvenation processes in glasses, as well as the interplay between grain boundary structure and chemistry through segregation engineering, will be discussed in the context of controlling metastable structural configurations.
5:20 PM Invited
Moving Closer to Equilibrium but Maintaining the Defects (and the Properties): Timothy Rupert1; 1University of California, Irvine
Traditional materials theory sees a defect as a feature that moves us further from equilibrium, which means that the most interesting materials are often extremely unstable. In this talk, I discuss how one can manipulate the natural variations in stress, chemistry, and atomic structure near grain boundaries and dislocations to stabilize these features. We use atomistic modeling to demonstrate that dislocations can drive local complexion transformations, with the final structure strongly dependent on the alloy choice. We also show that grain boundary networks can allow for interesting complexion transitions, driven by local variations in dopant segregation. Finally, we also show preliminary results outlining the kinetics of these transformations. Specifically, carefully designed variations in cooling rate are connected to complexion thickness in a polycrystalline material. As a whole, this work demonstrates that our field is arriving at the cusp of a new era of materials science, where one can make “defects-by-design.”
5:50 PM
Targeting Specific Nanotwin Configurations in Sputter Deposited Alloys to Enable Systematic Investigation of Dislocation-twin Interactions: Francisco Andrade Chavez1; Orcun Koray Celebi1; Huseyin Sehitoglu1; Jessica Krogstad1; 1University of Illinois at Urbana-Champaign
The remarkable strength of nanotwinned metals and metallic alloys has been attributed to a number of mechanisms, all involving frequent dislocation-twin interactions. Despite the high density of nanotwins that have been achieved through a variety of processing routes, the relative distribution of twins remain stochastic. For simple deformation modes, such a distribution of dislocation barriers can be accommodated by adapting traditional strengthening models. However, under cyclic loading conditions, the spacing between obstacles play a much more nuanced role. Modeling approaches have begun to tackle this problem, but without experimental validation in a controlled microstructure, the impact remains limited. Here we present preliminary efforts to understand the relationship between magnetron sputtering parameters, substrate constraint and the intrinsic properties of the alloy, including chemistry, stacking fault energy and the propensity for local ordering. This insight can be leveraged to tune the microstructure of nanotwinned thin films and systematically investigate fundamental dislocation-twin interactions.
6:10 PM
Ultrafine-grained and Nanocrystalline Steels for Enhanced Mechanical Properties and Irradiation Resistance: Haiming Wen1; Andrew Hoffman1; Jiaqi Duan1; Maalavan Arivu1; 1Missouri University of Science and Technology
Steels have important applications in current and advanced nuclear reactors, however, their irradiation tolerance and mechanical properties need to be improved. Bulk ultrafine-grained (UFG) and nanocrystalline (NC) metals possess drastically higher strength than their conventional coarse-grained (CG) counterparts, and may have significantly enhanced irradiation tolerance. In this study, UFG and NC austenitic and ferritic-martenstic steels were manufactured by equal-channel angular pressing (ECAP) and high-pressure torsion (HPT). The microstructure and mechanical behavior of these steels were carefully studied. Their thermal stability was also investigated. Neutron irradiation is being performed to study irradiation behavior of the steels. Ion irradiation was also conducted to compared with the neutron irradiation. Results indicated that the UFG and NC steels possess significantly improved hardness/strength compared to their CG counterparts. All the UFG and NC steels are thermally stable at least up to 500 °C. UFG and NC steels possess enhanced irradiation resistance than their CG counterparts.