Deformation Mechanisms, Microstructure Evolution, and Mechanical Properties of Nanoscale Materials: 2D Materials and Multilayers
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
Tuesday 2:30 PM
March 21, 2023
Room: Aqua 300AB
Location: Hilton
Session Chair: Hesam Askari, University of Rochester; Shoeib Chowdhury, University of Rochester
2:30 PM Invited
Microstructural Evolution of Nanomultilayers with Various Types of Interfaces: Andrea Hodge1; 1University of Southern California
Nano multilayers films consist of alternating layers of materials with thicknesses on the order of nanometers and typically display many attractive properties which are attributed to the fact that, as the layer thicknesses decrease, the individual layer behavior changes and the interface volume increases. In this presentation, I will show how to synthesize and characterize systems of nanostructured multilayers, leveraging nanoscale features to enhance properties and function. To address this, samples with a wide range of composition and layer thicknesses were synthesized via DC/RF and reactive magnetron sputtering. Multilayer configurations with crystalline/crystalline and crystalline/amorphous interfaces were designed as model systems in order to identify the contributions of both interface properties and composition and identify global relationships between predictions and observations of nanoscale microstructures.
3:00 PM
Inter-relationship of Stress and Microstructure in BCC and ‘Beta’ Tungsten Films: Jonathan Johnson1; Tong Su2; Eric Chason3; Gregory Thompson1; 1University of Alabama; 2Brown University ; 3Brown University
Thin films experience significant residual stresses during deposition that is linked to the coalescence of the film. A series of W films are deposited at different deposition rates and pressures. Films deposited at the three highest pressures were tensile in stress, had small grains (~ 15 to 20 nm), and stabilized the metastable A15 phase often referred to as beta-W. At the lowest pressure, the films were compressive in stress, larger grain sizes (~ 70 to 90 nm), and primarily stabilized the bcc W phase. If a W seed layer was grown under either the bcc W or beta-W growth conditions, the subsequent W layer adopted the phase state of the seed layer, independent of processing conditions and/or grain sizes, suggesting that the phase state is most likely determined in the initial stages of nucleation.
3:20 PM
High Peak Hardness in Al-Ni Multilayer Thin Films Originate from Intermetallic Interface Contributions: Nicolas Peter1; Marilaine Moreira de Lima1; Xi Li1; Ruth Schwaiger1; 1Forschungszentrum Jülich
Nanometallic multilayer systems provide a suitable tool to study the effect of interfaces subjected to thermodynamic or mechanical stimuli. Most studies fabricated layered systems of elements with a positive enthalpy of mixing to create almost atomically sharp interfaces, e.g. Cu-Ag. By contrast, few studies investigated the interface morphology for systems with negative enthalpy of mixing in depth. We investigate here the reactive Ni-Al system on sputter deposited samples with a varying layer thickness between 5 and 250 nm. It was found by aberration-corrected electron microscopy and electron energy loss spectroscopy that a relatively large negative enthalpy of mixing leads to intermetallic-like bonding at the interface for small layer thicknesses and B2-NiAl “pockets” at the interface of large layer thicknesses. Consequently, we measure a peak hardness of 9.03 ± 0.14 GPa, which is the highest measured so far for fcc-fcc layered systems and shows the potential of this interface engineering route.
3:40 PM
Deformation Behavior of the Crystalline/Amorphous Al/Si Nanocomposite Having Nanolaminate and Nano-fiber Morphology: Bibhu Prasad Sahu1; Wenqian Wu2; Jian Wang2; Amit Misra1; 1University of Michigan; 2University of Nebraska-Lincoln
The deformation mechanism in crystalline Al / amorphous Si nanocomposite sputtered thin films are compared for nanolaminate and nanofibrous morphologies. Nanocomposite morphology of crystalline Al nanofibers, approximately 40-50 nm in length and 15-20 nm in diameter and 20 nm spacing, embedded in amorphous Si are shown to suppress shear band formation, in compression, to plastic strains exceeding 24% and exhibit strain hardening to a maximum flow stress of 2.9 GPa. Nanolaminate morphology, 80 nm crystalline Al - 20 nm amorphous Si, exhibits catastrophic shear bands starting at plastic strains of ≈14%. In the nanolaminate morphology, shear bands with brittle fracture in Si are observed. In the nano-fibrous morphology, cross-sectional transmission electron microscopy of the deformed samples reveals a high density of stacking faults and nanotwins in Al nanofibers and no micro-shear bands in the fibrous morphology suggesting plastic co-deformability.
4:00 PM Break
4:20 PM
Dislocation Formation and Evolution in Moiré Reconstructed Twisted Bilayer Graphene: Shoieb Ahmed Chowdhury1; Aditya Dey1; Hesam Askari1; 1University of Rochester
Controlling the relative rotation between two layers in a 2D material, namely "Twisted Bilayer", has resulted in many exciting properties. Within the Moiré patterns created in a twisted bilayer, the interlayer stacking of atoms show spatial variations and form different combinations depending on twist angle. We study the evolution of local stackings in twisted bilayer graphene (TBG) under heterostrain using atomistic simulations. To understand the associated mechanics, we present an inter-layer dislocations-based analysis. The variation in stackings within the Moiré pattern is described by dislocation arrays from the initial commensurate structure. Away from the centers of hexagonal Moiré patterns, regions with partial dislocations exist belonging to intermediate SP stackings, whose characteristic width is described by the width of these partials. Triangular domains of 'AB/BA' stacked regions are separated by partial dislocations summing to full dislocations. Our framework resolves Moiré reconstruction in large angle TBG.
4:40 PM
Mechanistic Design of Advanced Hierarchical Ti-Ti2AlC Metal-MAX Multilayered Nanolaminates: Skye Supakul1; Krishna Yaddanapudi2; Garritt Tucker3; Sid Pathak1; 1Iowa State University; 2University of California, Davis; 3Colorado School of Mines
We investigate the deposition, microstructure, and mechanical properties of unique hierarchical multilayered metallic (Ti) and MAX phase (TI2AlC) Nanolaminate (MMN) systems where the interface between metal and MAX phase layers are in direct competition with the internal interfaces within the MAX layers. We utilize a unique twin chamber atomic layer deposition and physical vapor deposition system that enables deposition in both chambers without breaking the chamber vacuum to explore various pathways to deposit MMN while minimizing the interlayer diffusion of atomic species. Transmission electron microscopy investigations confirm the presence of TI2AlC and Ti layers, and selected area electron diffraction analysis reveals the nanocrystalline nature of the deposited layers. Subsequent micro-pillar compression demonstrates an ~150% increase in stress across ~10% strain after yield compared to micro-compression on nanocrystalline Ti3AlC2 MAX phase which demonstrated an ~110% increase in stress across only ~1% strain after yield, suggesting higher strain accommodation in the MMN.
5:00 PM
The Effect of Annealing on the Mechanical Behaviors and Failure Mechanisms of Nano Metallic Laminates: Yifan Zhang1; Rodney McCabe1; Jonathan Gigax1; Nan Li1; Thomas Nizolek1; John Carpenter1; Matthew Schneider1; Laurent Capolungo1; 1Los Alamos National Laboratory
Nanometallic laminates (NMLs) exhibit high strength with limited work hardenability and can fail via different modes depending on loading conditions. Here, we investigate the effects of annealing on the mechanical properties of Cu/Nb and Ag/Fe NMLs using meso-scale tension and in situ micro pillar compression tests and through microstructure characterizations by S/TEM and transmission Kikuchi diffraction (TKD). Analyses show that annealing can reduce the initial intralayer dislocation density, change grain and layer morphology, and facilitate uniform deformation. Before annealing, as-rolled Cu/Nb NMLs exhibit little capacity for work hardening during tension and zero ductility for ND tension with failure occurring before yield via intergranular crack propagation within Nb layers. Annealing enhances the work hardenability, ductility, and fracture toughness with moderate decreases to overall strength of Cu/Nb NMLs. Annealing also affects the kinking propensity in Ag/Fe NMLs, by increasing the kink band (KB) onset strain, decreasing KB probability and load drop magnitude.