Deformation Mechanisms, Microstructure Evolution, and Mechanical Properties of Nanoscale Materials: Size Effects
Sponsored by: TMS Materials Processing and Manufacturing Division, TMS: Nanomechanical Materials Behavior Committee
Program Organizers: Niaz Abdolrahim, University of Rochester; Matthew Daly, University of Illinois-Chicago; Hesam Askari, University Of Rochester; Eugen Rabkin, Technion; Jeff Wheeler, Femtotools Ag; Wendy Gu, Stanford University
Monday 2:00 PM
March 20, 2023
Room: Aqua 300AB
Location: Hilton
Session Chair: Eugen Rabkin, Technion; Anuj Bisht, Technion
2:00 PM Invited
Nanoparticles under High Pressure: Assembly and Formation of Active Nanostructures: Hongyou Fan1; 1Sandia National Laboratories
Precise control of structural parameters through nanoscale engineering to improve optical and electronic properties of nanoparticles continuously remains an outstanding challenge. Previous work on nanoparticle assembly has been conducted largely at ambient pressure. Here I will present a new Pressure-Induced Assembly and Fabrication method in which we applied high pressure or stress to nanoparticle arrays to induce structural phase transition and to consolidate new nanomaterials with precisely controlled structures and tunable properties. By manipulating nanoparticle coupling through external pressure, a reversible change in their assemblies and properties has been achieved and demonstrated. Additionally, over a certain threshold, the applied pressure will force these nanoparticles into coalescence, thereby allowing the formation and consolidation of one- to three-dimensional nanostructures. Through pressure induced nanoparticle assembly, materials engineering and synthesis become remarkably flexible without relying on traditional crystallization process. SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525.
2:30 PM
The Effect of Ion Irradiation on Strength of Ni Nanoparticles: Anuj Bisht1; Yuanshen Qi2; Eugen Rabkin1; 1Technion; 2GTIIT
Recent studies indicate that the strength of faceted metal nanoparticles obtained by solid state dewetting is comparable to the theoretical strength of respective metals. The particles compressed with a flat punch exhibit purely elastic behavior up to very high values of strain approaching 10%, followed by a large displacement burst and a catastrophic plastic collapse. In this work we demonstrated that irradiating pristine Ni particles with Ga and Xe ions significantly reduces their strength, with Ga ions causing the most drastic strength drop. The displacement bursts in compressive load-displacement curves of Xe-irradiated Ni particles were much smaller than in the case of their pristine counterparts, while the Ga-irradiated particles demonstrated nearly continuous plastic deformation. We characterized the defects in the particles induced by irradiation and correlated their type with the mechanical properties of the particles.
2:50 PM
Atomistic Modeling of Peierls Barriers to Dislocation Glide in Metals: Yipin Si1; David L. McDowell1; Ting Zhu1; 1Georgia Institute of Technology
Dislocation glide plays an important role in plastic deformation of crystalline solids. We perform nudged elastic band (NEB) calculations to determine the Peierls barrier and Peierls stress for screw and edge dislocations glide in face-centered cubic nickel. The minimum energy paths (MEPs) across multiple Peierls barriers are determined under different shear loads. The results demonstrate the decrease of Peierls barriers with increasing shear load and quantify the Peierls stresses. The calculated activation energies across sequential Peierls barriers are not constant from strain-controlled NEB. In contrast, the stress−controlled NEB method resolves this issue, giving the constant Peierls barriers even in small supercells. Furthermore, the free-end NEB methods are used to compute MEPs for long, highly tilted reaction paths. Our work demonstrates how to achieve accurate and efficient quantification of Peierls barriers to dislocation glide in metals, and provides a basis of investigation of Peierls barriers in compositionally complex alloys.
3:10 PM
In-situ Investigation of Tension-compression Anisotropic Behaviour of Ni-SiOC Nanocomposites: Bingqiang Wei1; Wenqian Wu1; Jian Wang1; 1University of Nebraska-Lincoln
Through co-sputtering Ni and Si-O-C, we synthesized Ni-SiOC nanocomposites with two characteristic microstructures: core (crystalline Ni)-shell (amorphous SiOC) nanostructures and nanograined Ni containing amorphous ceramic SiOC nanoparticles which developed during annealing the co-sputtered Ni-SiOC nanocomposites up to 800 oC. In-situ SEM compression tests show that both Ni-SiOC nanocomposites exhibit high plastic flow stability, which was attributed to microstructure-promoted plastic co-deformation between amorphous ceramics and Ni grains. However, limited plasticity was observed during their tension test. The core-shell nanostructures present brittle behaviour due to cracking along grain boundaries. The nanograined structure exhibits a limited tension plasticity and interface decohesion due to obvious deformation incompatibility between soft Ni and hard SiOC ceramic.
3:30 PM Break
3:50 PM Invited
How are Natural Structural Materials Toughened from the Nanoscale?: Ottman Tertuliano1; 1University of Pennsylvania
In structural materials engineering, we often aim to create materials that are simultaneously strong, tough and lightweight- a combination classically considered mutually exclusive. Biogenic composite materials such as bone exhibit a combination of these properties exceeding that of their constituents, a feat generally credited to their hierarchal structure, down to the nanoscale. In this talk, we will demonstrate the use of micro and nanoscales site-specific microstructural characterization and mechanical experiments to probe the strength, deformation, and fracture of human bone. We will demonstrate an in situ SEM/nanoindentor methodology, that enables 3-point bending fracture experiments with observation and measurement of crack growth and toughening behavior at nano and micrometer scales. We will discuss how expanding these small scale experiments on natural materials can enable future efforts in fundamental understanding of hierarchical structural design.
4:20 PM
Multi-stage Superelasticity in SrNi2P2 Intermetallic Compound via Lattice Collapse and Expansion and the Influence of Cryogenic Temperature: Shuyang Xiao1; Vladislav Borisov2; Adrian Valadani2; Guilherme Gorgen-Lesseux3; Roser Valentí2; Paul Canfield3; Seok-Woo Lee1; 1University of Connecticut; 2Goethe University; 3Iowa State University
Mechanical behavior of SrNi2P2 , one of ThCr2Si2-structured intermetallic compounds, has been investigated using in-situ micro-compression and micro-tension along [001] direction at room temperature, 200K and 100K. Room temperature mechanical testing revealed the giant superelasticity with an elastic strain limit near 20% if both compression and tension are considered. This is nearly the highest elastic strain limit ever reported for crystalline solids. Density Functional Theory calculation and High-Resolution Transmission Electron Microscopy show that this excellent superelastic performance is achieved by multiple-stage lattice collapse and expansion, which result from forming and breaking P-P bonds in two co-existing crystal structures. Our state-of-the-art in-situ cryogenic nanomechanical testing shows that at lower temperature, phase transition requires the lower transition stress under compression but the higher transition stress under tension due to the temperature-dependent P-P distance. Our results provide an insight into fundamental understanding of the superelasticity mechanism of SrNi2P2 at different temperatures.
4:40 PM
Grain Size Refinement Altering Yielding Mechanism in an Ultrafine-grained High-Mn Austenitic Steel: Chang-Yu Hung1; Yu Bai2; Tomotsugu Shimokawa3; Ya-Peng Yu1; Nobuhiro Tsuji2; Mitsuhiro Murayama1; 1Virginia Tech; 2Kyoto University; 3Kanazawa University
Some ultrafine-grained (UFG) metals have been found to overcome the paradox of strength and ductility. An UFG high-Mn austenitic steels is one of these and exhibits a unique macroscopic discontinuous yielding behavior. This presentation will address the underlying mechanism of discontinuous yielding behavior using ex/in-situ deformation TEM and dislocation analyses. We experimentally revealed that the plastic deformation mechanisms around macroscopic yield point show a prominent association with grain size. The main mechanism shifts from conventional slip in grain interior to twinning nucleation from grain boundaries by decreasing grain size to less than 1μm. The atomistic insights of dislocation reaction into twinning nucleation at the dominant type of GB (sigma3 boundary) were detailed. Expressly, the twin boundary having Shockley partial dislocations with disconnection character acts as a preferential twin nucleation site, that is characteristically different from coarse-grained counterparts and is likely ascribed to the lack of interior dislocation activities in UFG.
5:00 PM
Mechanical and Microstructural Analysis of a Nanocrystalline Supersaturated Solid Solution Cr-Cu Coatings: Michael Burtscher1; Markus Alfreider1; Christina Kainz1; Daniel Kiener1; 1Montanuniversitaet Leoben
The Cr-Cu system not only combines high strength and oxidation resistance, it furthermore enables beneficial electric properties and thermal conductivity. Hence, 60/40 and 70/30 at.% Cr-Cu films of this promising material system were fabricated by PVD at room temperature. In both cases, a film thickness of about 2 µm of a supersaturated solid solution was deposited on Si substrates. The microstructures of the nano crystalline alloys were investigated by SEM, STEM and EDX maps, while the mechanical strength and fracture properties were determined by nanoindentation techniques and in-situ notched bending beam experiments. Furthermore, high-temperature XRD experiments under a protective atmosphere unveiled the segregation temperature for both supersaturated solid solutions. To further investigate the segregation kinetics, in-situ TEM annealing experiments were carried out. Hence, this study provides a comprehensive insight into the segregation behavior of supersaturated solid solution Cr-Cu coatings and the related influence on the mechanical properties.