Deformation Mechanisms, Microstructure Evolution, and Mechanical Properties of Nanoscale Materials: Poster Session
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 5:30 PM
March 20, 2023
Room: Exhibit Hall G
Location: SDCC
Cancelled
A Discrete Dislocation Dynamics Investigation of the Mechanical Behavior of Irradiated FeCrAl Alloys: Yash Pachaury1; Anter El-Azab1; 1Purdue University
In this work, we investigate the mechanical behavior of irradiated FeCrAl nanopillars using discrete dislocation dynamics (DDD) simulations. Different irradiation induced defects such as a/2<111> and a<100> prismatic loops, and composition fluctuations/α’ precipitates are incorporated in DDD by taking cues from experimental observations and the effects of these defects on the mechanical behavior of the irradiated FeCrAl alloys have been studied. Subsequently, the mechanical behavior of the nanopillars have also been compared with the bulk deformation response of the irradiated FeCrAl alloys. It is observed that the 0.2% yield strength of the irradiated nanopillars is always larger than the homogeneous/pristine nanopillars. Orientation dependent mechanical behavior of the irradiated nanopillars is also discussed.
G-1: Change of Ni Composition According to pH Value of Fe-Ni Invar Manufactured by Electroforming: Jihan Gwak1; Jun Ha Lee1; Seung-Joon Lee2; Se-Eun Shin1; Yong-Bum Park1; 1Sunchon National University; 2Tech University of Korea
Fine metal mask used in the organic light-emitting diode display industry uses Fe-Ni Invar alloy with a low coefficient of thermal expansion(CTE). Fe-Ni Invar alloy can be manufactured by a hot-rolling process, however, Fe-Ni Invar alloy is fabricated by electroplating to obtain a thinner sheet for broad application. In the case of Fe-Ni Invar manufactured by electroforming, the CTE is higher than the hot-rolling process, and Fe-Ni Invar alloy close to 0 can be obtained by adjusting the contents of Ni. In this discussion, a Fe-Ni Invar alloy sample with a clean surface and a constant elemental composition was prepared by adjusting the pH value among several variables that control the contents of Ni. When the pH value is high, the Fe composition increases, and the Ni composition decreases, but when the pH value is low, a replated region is generated.
G-2: Deformation Mechanisms of Metal Matrix Nanocomposites: A Molecular Dynamics Study: Wenwu Xu1; Md. Shahrier Hasan1; 1San Diego State University
With nanoscale reinforcements resulting in high density of matrix/particle interfaces, Metal Matrix Nanocomposites (MMNC) behave differently as compared to their micro-composite counterparts. An atomistic understanding of fundamental deformation mechanisms is necessary to link the nanoreinforcers with the strengthening and fracture properties of the nanocomposite. Using Al-SiC nanocomposite as a model material, we conducted Molecular Dynamics simulations to investigate the deformation mechanism and defect evolution in the material by varying SiC particle size and particle volume fraction. We found that the deformation mechanism of Al-SiC MMNC is characterized into three subsequent mechanisms, which are: (I) defect free deformation driven by lattice distortion of the metal matrix, (II) dislocation-based deformation driven by dislocation nucleation and growth, and (III) failure-based deformation driven by interface separation and void growth. Our fundamental understanding of atomistic deformation mechanisms in the Al-SiC nanocomposite is expected to provide a basis for a more targeted design of advanced MMNCs.
G-3: Energetics and Mechanisms of Slip-Grain Boundary Interaction in Magnesium and Its Alloys: Vaidehi Menon1; Yong-Jie Hu2; Liang Qi1; 1University of Michigan; 2Drexel University
It is well-known that slip-grain boundary (GB) interactions strengthen materials (Hall-Petch relation). Analyzing these interactions in HCP Mg alloys could provide crucial information on how to improve their strength and ductility for light-weight structural applications. In a previous study (in publication), via molecular dynamics (MD) simulations, we found that certain GB + loading orientations promote nucleation of pyramidal partial <½c+p> dislocations at GBs, and adding Y-clusters to the GB lowers critical stress for slip nucleation. Further interaction of <½c+p> slip with GBs nucleated more <½c+p> slip (evidenced by high number of I1 SFs). In this talk, we extend our MD investigation to the interaction of different slip systems with several individual Mg GBs, to analyze both geometric and energetic transmission parameters, and relate them to macroscopic values. We also compare the pure Mg GB results with solute-segregated Mg GBs, to understand the effect of GB chemistry on slip transmission behavior.
Epoxy Based GFRP Nanocomposites Containing Silanized Nanoclay and Compatibilized Polyethylene Fibers for High Impact Strength Applications: Daksh Shelly1; Tarun Nanda1; Rajeev Mehta1; 1Thapar University
Epoxy based GFRP composites comprising of surface-treated polyethylene fibers (PE) and silanized nanoclay were processed through vacuum assisted resin infusion moulding with substantial improvements in impact strength. PE fibers were used owing to characteristics like good toughness, strength, resistance to chemicals, and light-weight. Nanoclay and PE fibers were subjected to surface treatments for improving compatibilization which was confirmed by FESEM-EDS and FTIR techniques. XRD/TEM analysis was used to determine morphology of nanoclay platelets. Reinforcement of pristine PE fibers decreased the mechanical properties owing to less compatibility among constituents of composite system. However, reinforcement of compatibilized PE fibers to GFRPs boosted the impact strength. GFRPs reinforced with maleic anhydride grafted PE fibers and silanized nanoclay provided maximum enhancement of 160% in impact strength over the base composite. FESEM micrographs identified the mechanisms causing improvement in impact behaviour.
G-4: In Situ Nanomechanical Testing Under Cryogenic Conditions: Eric Hintsala1; Kevin Schmalbach1; Sanjit Bhowmick1; Douglas Stauffer1; 1Bruker Nano Surfaces and Metrology
The combination of nanomechanical testing and cryogenic temperature-capability enables the exploration of a rich variety of materials’ behaviors, from phase transitions in metals to glass transitions in polymers. Similar to the studies performed in the high temperature, high vacuum, regime, in situ cryo work requires that the tip and sample be and remain in equilibrium temperature for the test. Here, a study using two common alloys with applications for reliability in extreme cold/aerospace conditions, is presented. These materials show a range of nano/micromechanical behavior that varies as a function of the applied temperature, including a ductile to brittle transition that greatly affects structural reliability.
G-5: In Situ SEM Tension Study of Al-Si Nanofibrous Composite: Wenqian Wu1; Bingqiang Wei1; Amit Misra2; Jian Wang1; 1University of Nebraska-Lincoln; 2University of Michigan
Strong and ductile Al alloys are highly desired in aerospace and automobile industries. By processing as-cast alloy via laser rapid solidification techniques, we refine coarse-grained Al-20 wt.% Si alloy into Al-Si nanofibrous composite with nanoscale, fibrous, fully eutectic microstructure. By strategically preparing in-situ tensile samples with different Si nanofiber orientation and colony numbers, we investigated the anisotropic mechanical behaviour of Al-Si nanofibrous composites and deformation incompatibility between different colonies. The present work provides fundamental knowledge to design high performance Al-Si bulk materials using additive manufacturing. This work is funded by DOE, Office of Science, Office of Basic Energy Sciences with the grant number of DE-SC0016808.
G-6: Influence of Substrate Topography and Mechanical Compliance on the Morphology of Nanoporous Gold Thin Films: Sadi Md Shahriar1; Noah Goshi1; Conner Winkeljohn1; Jeremy Mason1; Erkin Seker1; 1University of California- Davis
Nanoporous gold (np-Au) has found use in applications ranging from catalysis to biosensing, but its desirable performance relies on the tuneability of its morphology. While morphology evolution of bulk np-Au has been widely studied, knowledge about its thin film form is limited, where topography and mechanical compliance of the thin film substrate likely plays a critical role in np-Au morphology. In order to study these substrate effects, silicon and silicone substrates with varying ridge geometries were sputter-coated with sub-micron-thick gold-silver alloys followed by dealloying to obtain np-Au thin films. The pore morphology and surface cracks were characterized as functions of substrate topography and compliance. Overall, both topography and compliance led to significant variations in grain structure, pore morphology, and cracks, emphasizing the importance of accounting for substrate effects when fabricating np-Au thin films. We expect these results to assist in integrating np-Au thin films in miniaturized devices and flexible electronics.
G-7: Mechanical Characterization of Stacked Single-Crystal of Polyethylene and Monolayer MoSe2: Gang Feng1; Dong Zhou1; Henna Khosla1; Scott Retterer2; Bo Li1; 1Villanova University; 2Oak Ridge National Laboratory
Polymer single crystal (SC) is a key building block of semicrystalline polymers. However, experimental measurement of freestanding mono-lamella polymer SC has not been demonstrated. This is, in large part, due to the difficulties associated with manipulating freestanding individual mono-lamella SC because of its extremely low rigidity and low robustness. We demonstrate a new strategy to suspend a polymer SC by using a two-dimensional (2D) material (MoSe2) as backing. The hybrid stacks can be suspended over microholes. Nanoindentation was used to probe the suspended PE-SC/MoSe2 stack and MoSe2 monolayer. The results suggest the first experimentally-measured in-plane moduli of PE-SC and 2D MoSe2 as 32±3 GPa and 237±15 GPa, respectively. Such stacked unit represents an ultrathin structure of polymer-ceramic laminate and the idea can be applied to other laminated composite systems. Therefore, this research will pave the way to accurately measure the mechanical properties of polymer SCs and their composites.
G-8: Mechanical Properties of Nickel-Platinum Nanoparticles Fabricated by Solid-State Dewetting: Mor Levi1; Anuj Bisht1; Eugen Rabkin1; 1Technion – Israel Institute of Technology
We have studied the morphology and mechanical properties of Ni-Pt nanoparticles synthesized by solid-state dewetting of Ni-Pt bilayers deposited on a sapphire substrate. Such nanoparticles may be of interest for a number of catalysis-related applications. The size, shape, and spacing of the particles, as well as the degree of the long-range atomic order within them, were manipulated by varying annealing temperatures and times. We found that the morphology of the nanoparticles depends on composition: Increasing Pt content resulted in lower and wider nanoparticles, and in the change of their orientation with respect to the substrate. The in-situ micro-compression tests of the particles indicated that their strength decreases with increasing Pt content. We discussed this solid solution weakening trend, which is in contrast with the strengthening trend of bulk Ni-Pt solid solutions, in terms of nucleation-controlled plasticity.
G-9: Micro-mechanical Characterization on Amorphous Carbon and its Nanoporous Structures: Zhongyuan Li1; Ayush Bhardwaj2; James Watkins2; Seok-Woo Lee1; 1University of Connecticut; 2University of Massachusetts Amherst
Carbon materials have a strong potential as structural materials due to their strong ionic/covalent C-C bonds. In this study, we have developed amorphous carbon and its nanoporous structures with 50~70% of porosity and have investigated their mechanical behaviors. Both fully dense and nanoporous structures exhibit a large compressive fracture strain up to ~35% with a high work hardening rate. Raman spectroscopy revealed that the plasticity results from dynamic re-distribution of sp2 and sp3 bonds. Interestingly, fracture strength was found to be nearly independent of porosity. This porosity-independent fracture strength could result from the size-affected strength of nanoscale ligands. All amorphous carbon samples demonstrate the excellent modulus of resilience the orders of magnitude higher than most engineering materials, implying a strong capability to absorb and release the mechanical energy. Our study provides an insight into understanding of mechanical behavior of amorphous carbon and its nanoporous structure.
G-10: Molecular Dynamics of Nanosuspension Droplet Impact on Solid Surfaces: Baiou Shi1; Siddharth Ravi1; 1Pennsylvania State University Erie
The behavior of nano-fluids, or fluid suspensions containing nanoparticles in the realm of capillary fluid flow, has garnered tremendous attention recently for applications spanning from household and personal care products to advanced targeted drug therapy and materials fabrication. One concern is how to control the ordering of nano-particle arrays and to fabricate those functional devices. Nano-suspension provides us a path to synthesize and disperse nanoparticles in fluids, however, the fundamental mechanisms about interfaces and wetting kinetics are still unknown when a nanosuspension drop spreads on a solid surface. Herein, results from molecular dynamics simulations will be presented to explore the nanosuspension metal droplet impact process. Furthermore, results presented illustrate how the role of impact angle and velocity affect the spreading kinetics and how this connects to dynamic droplet morphology and associated particle positioning on surfaces.
Multiscale Chemistry for Hydrogen-based Direct Reduction of Iron in Steelmaking: Xueli (Sherry) Zheng1; Lauren Moghimi1; Subhechchha Paul1; Yi Cui1; Leora Dresselhaus-Marais1; 1Stanford University
Steelmaking contributes to 8% of the total CO2 emissions globally. One approach to decarbonizing steelmaking is to shift from the coal-based blast furnaces to hydrogen-based direct reduction of iron. While extremely important, the chemistry in these reactors is often complex and poorly understood. Herein, we measure the kinetics of magnetite (Fe3O4) reduction with H2, comparing industrial Fe3O4 to the lab-synthesized nanoscale Fe3O4 samples. Using in-situ synchrotron X-ray diffraction, we demonstrate that the magnetite to wustite (FeO) step of the reaction occurs quickly, while the subsequent FeO to metallic Fe is rate-limiting. We “zoom in” on the nanoparticulate samples on the full T-dependence of the nanoscale chemistry and the associated structural changes in the sample morphology. Using small-angle X-ray scattering, we demonstrate how the kinetics evolve simultaneously with mesoscopic structural changes. Environmental transmission electron microscopy indicates the self-assembly and fusion of the reacting particles into elongated and irregular structures.
G-11: Nanoindentation Studies on the Surface Properties of Irradiated Concentrated Solid-solution Alloys: Youxing Chen1; Liuqing Yang2; Jimmie Miller2; William Weber3; Hongbin Bei4; Yanwen Zhang5; 1University of North Carolina at Charlotte ; 2University of North Carolina at Charlotte; 3University of Tennessee; 4Zhejiang University; 5Oak Ridge National Laboratory
Concentrated solid-solution alloys (CSAs), as a new type of alloys, have shown great potential for radiation-tolerant structural materials. However, the mechanical properties of the irradiated CSAs are less explored due to the limited volume of the irradiated region. Nanoindentation is a unique technique to probe surface properties at the micrometer and sub-micrometer scales in a high-throughput manner, accompanied by challenges from indentation size effect, pile-up/sink-in effect, and strain rate sensitivity. In this talk, Ni-based CSAs consisting of 3d transition metal elements including Co, Cr, Mn, and Fe will be studied, including unique single-crystal Ni, NiCo, NiFe, Ni80Cr20, and NiCoFeCr samples with (100) surfaces. The influence of radiation dose and different elements will be investigated through nanoindentation and nanoindentation strain rate jump tests.
G-12: Nanomechanical Testing of Limited Slip System Materials: Deformation and Fracture: Hugh Grennan1; David Bahr1; 1Purdue University
Organic crystalline materials, commonly used in energetics and pharmaceuticals, are typically non-cubic materials with limited slip systems. Nanoindentation is conducive to measuring modulus, hardness, and fracture behavior in these solids, where individual crystals with sub-mm dimensions are commonly used in composite systems. We examine two monoclinic material systems with the same crystal structure but different slip behavior. Post nanoindentation scanning probe microscopy shows impressions which are non-conformal to pyramidal indenters in an azoxyfurazan-based crystal (modulus and hardness approximately 14 GPa and 660 MPa, respectively), whereas a similar modulus and hardness nitrosamine-based crystal (about 11 GPa and 430 MPa) showed post-indent impressions that correspond to the shape of the probe. Both materials show minor evidence of yield phenomena, suggesting similar initial dislocation densities. Multi-angle probes were then used to compare the likelihood of indent-induced fracture and the propensity for fracture appears to increase in molecular organics with fewer active slip systems.
G-13: Nanoscale Liquid Infiltration – an Ultra-fast Deformation Mechanism for Energy Mitigation: Mingzhe Li1; Weiyi Lu1; 1Michigan State University
Inspired by the capillary effect, forced liquid infiltration into hydrophobic nanopores has been employed as an advanced energy absorption mechanism in liquid nanofoam (LN) systems. The energy dissipating mechanism is to force a non-wetting liquid to flow into hydrophobic nanopores, converting the external mechanical energy into solid-liquid interaction energy and heat. However, under dynamic impacts whether liquid infiltration can be fully activated is fundamentally unanswered. To this end, we have experimentally investigated the competition between liquid infiltration and pore crushing at the nanoscale.Under a wide range of strain rates from quasi-static compression to dynamic impact, our results show that the nanopores in LN remain undeformed, as demonstrated by the strain rate-independent liquid infiltration behavior. These findings offer a mechanistic explanation for the ultra-fast energy dissipation rate and high energy absorption efficiency of LN at high strain rate impact and blast scenarios.
G-14: Optimization of Nanocrystalline, Ultra-fine Grained and Bimodal Nickel According to Mechanical Properties: Michael Marx1; Dominic Rathmann1; Christian Motz1; 1Saarland University
Optimizing the mechanical properties of nanocrystalline (nc), bimodal and ultrafine grained (ufg) nickel has been investigated with focus on tensile and fatigue strength and thermal and mechanical stability of the microstructure. The material was prepared by pulsed electro deposition with a layer thicknesses up to 2 mm and very homogeneous microstructure. Electron backscatter diffraction and transmission Kikuchi diffraction in scanning electron microscope were optimized as high resolution measurement techniques. Nc, bimodal and ufg microstructures could be adjusted by selecting suitable amount of additives and heat treatment parameters. The mechanical stability was investigated especially under cyclic loading with crack growth. The nc microstructures show the best mechanical properties. By atom probe tomography the reduction of strength and ductility of the bimodal and ufg microstructures could be attributed to grain boundary embrittlement caused by sulfur containing additives and heat treatment. Therefore, further approaches were discussed to increase the stability of nc metals.
G-15: Orientation Dependent Micro-mechanical Deformation Behavior of Refractory High Entropy Alloy as a Function of Strain Rate and Temperature: Shristy Jha1; Sundeep Mukherjee1; Saideep Muskeri1; Maryam Sadeghilaridjani1; Abhishek Sharma1; Sriswaroop Dasari1; Rajarshi Banerjee1; Yu-Chia Yang1; 1University of North Texas
Refractory high entropy alloys (R-HEAs) have attracted widespread scientific and technological interest due to their superior properties compared to conventional refractory metals. Here, the deformation behavior of a single-phase body centered cubic R-HEA, namely HfTaTiVZr, was evaluated by micropillar compression at different strain rates over a range of temperatures for two orientations, namely [101] and [111]. There were significant differences in the strengths, strain hardening rates, deformation morphologies and strain rate sensitivities between the two orientations micropillars at room temperature (RT). These differences were attributed to the variations in the operative mechanisms of plasticity (TRIP vs dislocation plasticity), studied with the help of transmission electron microscopy for the two cases. Significant differences in micro-mechanical deformation behavior were observed as a function of temperature too, which was attributed to different underlying mechanisms, explored via in-situ deformation videos, post-compression images, and dislocation theory based molecular dynamics (MD) simulations.
G-16: Phase Transition and Nanomechanical Properties of Refractory High-entropy Alloy Thin Films: Effects of Co-sputtering Mo and W to a TiZrHfNbTa System: Changjun Cheng1; Michel Haché1; Xiaofu Zhang2; Yu Zou1; 1University of Toronto; 2Chinese Academy of Sciences
Composed of multiple principal refractory elements, refractory high-entropy alloys (RHEAs) have attracted significant attention due to their interesting structure and properties. However, current research on RHEAs mainly focuses on a few well-known compositions such as NbMoTaW, NbMoTaWV, and TiZrHfNbTa. Finding new RHEAs with improved mechanical properties is highly desirable. In this work, using a three-target (TiZrHf, NbTa, and Mo/W) magnetron co-sputtering system, we fabricate two new RHEA thin films – TiZrHfNbTaMo and TiZrHfNbTaW. The TiZrHfNbTaMo and TiZrHfNbTaW thin films exhibit an amorphous state, while the TiZrHfNbTa one shows a nanocrystalline structure. The nanoindentation results show that the addition of Mo or W in the TiZrHfNbTa increases the hardness while maintaining comparable elastic moduli. Based on strain rate sensitivity tests, we demonstrate their activation volumes and discuss their deformation mechanisms in the nanoindentation tests.
Cancelled
G-17: Photo-stable Thermoset Shape-memory Polymers: Role of Unique Graphene Nanoscrolls for Superior Service Life: Dilip Depan1; Owolabi Akanni1; William Chirdon1; Ahmed Khattab1; 1University of Louisiana at Lafayette
Thermosetting shape memory polymers (TSMPs) have attracted significant attention from academia and industries due to their unique smart properties. However, their complete utilization, especially long-term weathering is not understood due to complications in their chemical structure during environmental degradation. To improve their service life, we used a unique and novel carbon nanofiller, graphene nanoscrolls (GNS) with TSMPs. GNS has scrolled architecture with tunable internal diameter. The prepared nanocomposites were exposed to artificial weathering such as ultraviolet (UV) light and moisture, followed by characterization using FTIR, DSC, nanoindentation and SEM techniques. The degradation is explained in terms of competing reactions such as chain scission and cross-linking, further modulating the thermo-mechanical properties of TSMPs. GNS renders superior mechanical properties and prevents UV induced photo-degradation. Morphological and thermal analysis confirmed surface degradation and an increase in glass transition temperature due to cross-linked polymer chains.
Stochastic Mechanical Modeling of Cavitary Defects in Porous Aluminum Structures: Mujan Seif1; Alexandre Martin1; Matthew Beck1; 1University of Kentucky
The inherent complex, disordered, and porous microstructure of aluminum foam makes it an ideal material for hypervelocity impact shielding. However, this same structure makes predictive modeling of its mechanical properties difficult. Its randomly oriented constituent ligament structure also creates significant variability in properties at different length scales. An understanding of the transition from nano-/micro- (local) to macro- (bulk) length scales is critical to quantifying the structural effects of various inhomogeneities like inclusions, cracks, etc. To this end, we utilize a homogenizing approach inspired by those applied to polycrystals. Rather than simplifying the material such that its unique characteristic structural features are neglected, this approach integrates complex structure and predicts mechanical behavior in the form of statistical distributions—as opposed to arithmetic means—of properties. Here, we compute and compare these distributions as a function of cavity shape, orientation, and volume, as well as overall length scale.
G-18: Structures and Nanomechanical Behavior of Cu-Mo-W Nanocomposite Thin Films: Forrest Wissuchek1; Bibhu Sahu1; Amit Misra1; 1University of Michigan
The morphology of multiphase thin films produced by co-depositing immiscible elements is dependent on the competition between how fast the species diffuse on the surface and how quickly they are buried by the incoming deposition. The processing-structure relationship of binary systems, such as Cu-Mo, has identified morphological transitions due to increasing the processing temperature or decreasing the deposition rate. Adding W, a bcc refractory metal with very low mobility, impedes phase separation and delays the morphological transitions seen previously in Cu-Mo to higher deposition temperatures. The Cu-Mo-W nanocomposites deposited at temperatures above 800 C display a very fine layered structure which is unique at such elevated temperatures. The fine layered structure exhibits high strength due to the high density of interfaces, and compared to sequentially deposited multilayers with similar layer thicknesses, exhibit enhanced ductility by preventing shear banding.
G-19: Surface Film-induced Reversible Electrochemical Actuation in Nanoporous Metals Investigated using In Situ Small- and Wide-angle X-ray Scattering.: Alexander Ng1; Eric Detsi1; 1University of Pennsylvania
Nanoporous metal actuators, also known as metallic muscles, are strong and stiff like conventional piezoelectric actuators. However, unlike piezoelectric actuators that usually operate at very high voltages (> 100 V), nanoporous metals actuators operate at less than 2 V. The actuation mechanism in nanoporous metals with high surface-to-volume ratios arise from changes in surface stress. The common way to change the surface stress of nanoporous metals is via capacitive and faradaic redox reactions at the metal/electrolyte interface. In this talk, I will show that electrochemically growing/stripping a film onto/from a nanoporous metal electrode in aqueous media results in reversible dimensional changes of the nanoporous metal. We will use small- and wide-angle x-ray scattering (SAXS, WAXS) to probe changes in the dimension (SAXS) and changes in the crystal structure of the materials (WAXS) in situ during film deposition/stripping.
G-20: The Effects of Local Structures on the Dislocation Transmission Across Symmetric Tilt Grain Boundaries in Cu via Atomistic Simulations: Khanh Dang1; Sumit Suresh1; Avanish Mishra1; Nithin Mathew1; Edward Kober1; Saryu Fensin1; 1Los Alamos National Laboratory
Dislocations, grain boundaries (GB), and their interactions play a major role in the plasticity and fracture of polycrystalline metals. While there have been many dislocation-GB interaction studies, they tend to simplify the problems by only considering a subset of low-energy GB structures, which is not representative of those observed in experiments. In this work, molecular dynamics (MD) simulations are utilized to comprehensively study the dislocation- symmetric tilt grain boundary (STGB) interactions in Cu. A database of over 2,000 MD simulations of the interactions is generated for a wide range of dislocations (edge, screw, and mixed) and GB metastable structures under different loading conditions. Importantly, the GB structures are analyzed using strain functional descriptors that can be correlated to the outcomes of the interactions via machine learning techniques. The overall roles of the GB structures will be discussed with the focus on specific examples of the Σ3 [110](112) and Σ41 [110](338).
G-21: The Impact of Interface Orientation on the Vibration Behavior of Joined Aluminum Substrates: Milad Khajehvand1; Henri Seppänen2; Panthea Sepehrband1; 1Santa Clara University; 2Kulicke & Soffa Industries, Inc.
In various joining techniques, including ultrasonic bonding and friction stir welding, the contact area is under vibration. Challenges in detailed analysis of the interface during bonding have limited our understanding about the underlying mechanisms of bond formation in such processes. In this work, Molecular Dynamics simulations are utilized to study the interface by forming a contact between two misoriented aluminum substrates and applying subsequent vibration parallel to their interface. The evolution of the network of interfacial dislocations and atomic movements as a function of the interface orientations are analyzed. It is found that the (111)-interface planes present low-resistance sliding, while the (001)- and (110)-oriented systems exhibit multiplication of interfacial dislocations during vibration, leading to a substantial amount of atomic displacements not only parallel to the interface, but also perpendicular to it. This perpendicular atomic movement across the interface can explain development of strong bond in joining processes that employ vibration.