Engineering Commons^™

Diffusion-Based Deformation In Elevated Temperature Micropillar Compression Of Mg-Nb Multilayers, Keith Thomas, Juri Wehrs, Siddharta Pathak, Johann Michler

Nanomechanical Testing in Materials Research and Development V

multilayer, elevated-temperature, micropillar compression

Indentation Behavior Of Superelastic Hard Carbon, Olga Chernogorova, Ekaterina Drozdova, Iraida Ushakova, Evgenii Ekimov, Vicente Benavides, Aleksander Soldatov

Nanomechanical Testing in Materials Research and Development V

Supererlastic hard carbon particles up to 1 mmin size were produced by fullerene collapse upon high-pressure high-temperature treatment with simultaneous sintering of metal-matrix composite materials (CM) reinforced by such particles. The hardness of carbon particles can be varied in a wide range by changing the parameters of their structure, which consists of curved graphene planes or their packets of different sizes. Such carbon phase was called “nanoclusterd graphene phase” (NGP) [1]. The properties of the carbon particles were controlled by changing treatment pressure (5 and 8 GPa) and temperature (1100-1800 K), composition of parent fullerites (C60 or C60/70), and pre-treatment …

Studying Fatigue Damage Evolution At Grain Boundaries Using Micro Mechanical Test Methods, Christian Motz

Nanomechanical Testing in Materials Research and Development V

Fatigue of materials and components is one of the main reasons that limit their lifetime and impacts sustainability. The ongoing miniaturization in many areas of modern technology, e.g. microelectronics, medical devices etc., requires the knowledge of mechanical properties in small dimensions to guarantee their reliability. The size of typical fatigue dislocation structures, which control the damage evolution, is in the order of micrometers. Hence, reducing the size of parts and components down into this regime raises the question, whether such microstructures can occurs or not and how this affects the damage evolution. For this reason, the development of fatigue microstructures …

Fracture Toughness Measurement With Microscopic Chevron-Notched Specimens, Goran Zagar, Martin Mueller, Vaclay Pejchal, Lionel Michelet, Marta Fornabaio, Marco Cantoni, Andreas Morensen

Nanomechanical Testing in Materials Research and Development V

The fracture toughness of a material is, in theory, a rather well defined mechanical material property; for ideally brittle material, it is the stress intensity of a sharp crack present in the material at the moment when crack propagation becomes unstable. Measuring the fracture toughness of materials, however, has always been difficult, mainly because meeting the conditions under which the property is well defined can be a challenge. In testing of macroscopic samples the validity of measurements is most often deduced by confronting results of various established testing protocols and sample configurations with criteria derived on the basis of analysis …

Thermo-Mechanical Characterization Of Polymer Samples Using Nanoindentation - From Bulk Characterization To Thin Film Properties, Dennis Bedorf, Martin Knieps, Wolfgang Stein

Nanomechanical Testing in Materials Research and Development V

Polymer films for the use of coating or structuring applications for small scale devices are widely used. For the raw bulk material the thermal and mechanical data are easily accessible and often supplied by the manufacturer. For the final use as a thin film, the verification of these properties is more difficult. Nanoindentation techniques can be used for the characterization of thin film due to the small-scaled mechanical stress field of the nanoindenter tip. Studies comparing nanoindentation data on bulk polymer samples with conventional DMA data show a good agreement in storage and in loss modulus [1]. Since thermal properties …

In-Situ Fracture Tests Of Brittle Materials At The Microscale, Giorgio Sernicola, Giovannini Tommaso, Rui Hao, T. Ben Britton, Finn Giuliani

Nanomechanical Testing in Materials Research and Development V

The fracture toughness of ceramics is often dominated by the structure of their grain boundaries. Our ability to improve life of ceramic components depends on our ability to investigate properties of individual grain boundaries.

This requires development of new fracture testing methods allowing high spatial resolution and high control over the area to test. Further benefits of these ‘small scale’ approaches will enable testing of specimens for which big volumes are not available (e.g. thin films, coating, or simply samples of dimensions limited by production process).

Recently, several techniques have been developed using small scaled mechanical testing, based within a …

Some Recent Advances In Nanomechanical Testing: High Strain Rates, Variable Temperatures, Fatigue And Stress Relaxation, Combinatorial Experimentation, J. Michler, J. Wehrs, G. Moharty, J. Schwiedrzik, G. Guillonneau, R. Schoeppner, J. Best, J.M. Wheeler, J.M. Breguet, Marcelo Conte

Nanomechanical Testing in Materials Research and Development V

In the first part of the talk, I will present two recently developed platforms for high temperature nanomechanical testing. The first platform allows for variable temperature and variable strain rate testing of micropillars in situ in the scanning electron microscope. By utilizing an intrinsically displacement-controlled micro-compression setup, which applies displacement using a miniaturized piezo-actuator, we’ve recently extended the attainable range of strain rates to up to~ 10³ s⁻¹, and enabled cyclic loading up to 10⁷ cycles and load relaxation tests. Stable, variable temperature indentation/micro-compression in the range of -45°C to 600°C is achieved through independent heating …

Cracking In Brittle Materials During Nanoindentation: New Insights Gained From Cohesive Zone Finite Element Modeling, George Pharr

Nanomechanical Testing in Materials Research and Development V

Cracking during nanoindentation of brittle solids with sharp pyramidal indenters like the Vickers and Berkovich has been modeled and systematically examined using cohesive zone finite element simulations. Although the initial stages of crack initiation cannot be adequately captured by these techniques, the cracks that form eventually evolve into long-crack geometries that behave much like those observed in experiment, provided the crack length is approximately ten times greater than the cohesive zone size. Once this is achieved, the simulations accurately describe how cracks grow and change during loading and unloading and how the sequence of cracking events depends on material parameters …

Limits Of Determining Stress States By Fib Method Due To Ga Implantation, Diana Courty, Alla Sologubenko, Stephan Gerstl, Ralph Spolenak

Nanomechanical Testing in Materials Research and Development V

In order to assess the stress state in different kinds of materials in a reliable and flexible way, a Focused Ion Beam Microscope (FIB) routine has been developed to obtain information on the stress state in a material, in particular in thin films [A-C]. This method, named FIB-DIC micron-scale ring-core method, is based on monitoring relaxation of the material during a progressively deeper milling with a FIB beam. With digital image correlation (DIC), the change in the feature position can be analyzed and converted in residual strain and then with some modelling to residual stress. The method has already been …

Accessing The Phase Transformation And Deformation Behavior Of Metastable Stainless Steels Through Cyclic Nanoindentation, Ina Sapenzanskaia, J.J. Roa, A. Mateo, A. Redjaimia, R. Kouitat

Nanomechanical Testing in Materials Research and Development V

Austenitic metastable stainless steels are a materials group distinguished by their excellent mechanical properties, offering high potential for further improvement by thermo-mechanical treatments. Under deformation, these steels undergo a complex deformation and phase transformation. Their mechanical properties at macroscale, such as strength, ductility or fatigue behavior, have been largely investigated, yet they are not always predictable, as they highly depend on the microstructural characteristics of the material. In order to achieve a better understanding at the microstructural level, this work aims at the investigation of the deformation mechanisms in metastable stainless steels at sub-grain level and the interaction between grains. …

Extraction Of Crystal Plasticity Parameters Of In718 Using High Temperature Micro-Compression, Bin Gan, Aitor Cruzado, Marcos Jimenez, Koldo Ostolaza, Arantza Linaza, Javier Segurado, Javier Lloca, Jon Molina

Nanomechanical Testing in Materials Research and Development V

Ni-based superalloys are widely utilized in structural applications in aeroengine and power generation industries, owing to their exceptional high temperature mechanical properties in corrosive and oxidizing environments. Depending on the application fields, different types of superalloys with disparate microstructures are employed. For the turbine discs and some static components, forged or cast polycrystalline Ni-based superalloys are usually used. In the present investigation, site-specific micropillars with the diameter varying from 1 um to 18 um were milled out by Focused Ion Beam (FIB) from a polycrystalline IN718 superalloy specimen and then measured with high temperature micro-compression techniques up to 575 ºC. …

Mechanical Properties Of Lithiated Silicon: A Candidate Electrode For Lithium Ion Batteries, William Nix, Lucas Berla

Nanomechanical Testing in Materials Research and Development V

Recent advances in nanoindentation of lithiated silicon are described. Silicon, due to its high theoretical specific capacity for electrochemical lithium incorporation, has emerged as one of the most appealing materials to replace conventional graphitic anodes in lithium ion batteries^. But inserting lithium into silicon causes a large volume expansion (~300%) that can promote fracture during lithiation/delithiation cycling, thereby reducing the practical capacity of silicon lithium ion battery anodes. Understanding these mechanical behavior problems is essential for their management and control. Current FEM modeling is based on only estimates of the elastic and properties of lithiated Si. Better knowledge of …

Nanoindentation Induced Deformation Anisotropy In Wc, Β-Si3n4 And Zrb2 Crystals, Tamas Csanadi, Dusan Nemeth, Alexandra Kovalcikova, Jan Dusza

Nanomechanical Testing in Materials Research and Development V

The influence of crystal orientation on elastic and plastic response of WC, β-Si₃N₄ and ZrB₂ ceramic grains is important to understand, model and enhance its composite mechanical properties. In order to investigate this, nanoindentation testing was carried out using Berkovich tip on selected surface areas which were mapped by electron backscatter diffraction (EBSD) prior to the tests. To study the surface morphology after nanoindentation and to characterize the resulted deformation fields around the imprints additional EBSD, atomic force microscopy (AFM) and scanning electron microscopy (SEM) investigations were performed. Considerable elastic and plastic anisotropy was found is …

Length-Scale Dependent Deformation Behavior Of Nanolayered Cu-Based Micropillars, Gang Liu, Jin Zhang, Jun Sun

Nanomechanical Testing in Materials Research and Development V

By using microcompression methodology, deformation of nanolayered crystal/crystal (C/C) Cu/Zr and Cu/ Cr, and crystal/amorphous (C/A) Cu/CuZr micropillars was systematically investigated within wide ranges of intrinsic layer thickness (5 – 150 nm) and extrinsic sample diameter (300 – 1500 nm). The intrinsic size effect, extrinsic size effect and their interplay were respectively revealed. Competition between the intrinsic and extrinsic size effects leads to a common experimental observation of a critical layer thickness of about 20 nm, above which the deformation is predominantly intrinsic-size-related and insensitive to sample size, while below which the two size effects are comparable. The underlying deformation …

How Residual Stresses Affect The Fracture Properties Of Layered Thin Films, D. Kiener, R. Treml, D. Kozic, J. Keckes, J. Zechner

Nanomechanical Testing in Materials Research and Development V

The continued miniaturization effort has revealed exciting new material behavior at small length scales, where pronounced size effects come into play and material properties are subject to change. This has led to the development of miniaturized testing techniques to determine local plastic properties. So far, however, only few efforts regarding the determination of residual stresses and fracture properties in miniaturized systems were made.

In this presentation, we will focus on recent developments regarding the measurement of residual stresses and miniaturized fracture properties using FIB based sample preparation and in situ SEM experiments. The depth resolved residual film stresses are determined …

Probing The Initial Stages Of Plasticity With Nanoindentation, Easo George

Nanomechanical Testing in Materials Research and Development V

The probed volumes in nanoindentation can be comparable to the characteristic length scales of some of the defect configurations that control early-stage plastic deformation in metals. Representative examples from work carried out with my collaborators will be reviewed with a view to shedding light on the elementary processes associated with the transition from elastic to plastic deformation. Among the topics to be discussed are: homogeneous versus heterogeneous dislocation nucleation, nucleation versus activation of pre-existing dislocations, effects of source density, pinning by interstitial elements, and influence of crystal structure.

Transition In Plastic Deformation Of Nanolayered Thin Films: Role Of Interfaces And Temperature, R. Raghavan, J.M. Wheeler, J. Michler, G. Dehm

Nanomechanical Testing in Materials Research and Development V

Insights into the parameters governing the plasticity of immiscible, nanocrystalline metals stacked in the form of layers are pivotal both from scientific and applications’ perspectives. An outstanding case consists of the contact metallurgy of pure copper used ubiquitously as metallic interconnects in electronic devices. Diffusion barrier layers such W or TiN are necessary to prevent undesirable diffusion of Cu into the Si-based device during synthesis and service. Also, supersaturated Cu-Cr alloys are desirable for improving the strength, while retaining optimal functional properties required for the application. The scientific curiosity lies in understanding the effects of reducing microstructural length scales on …

Hydrogen Effects On Nanoindentation Behavior Of Metallic Glass Ribbons, Yakai Zhao, In-Chul Choi, Moo-Young Seok, Jin-Yoo Suh, Jae-Il Jang

Nanomechanical Testing in Materials Research and Development V

Recently, metallic glass (MG) membranes that are permeable to hydrogen have gained interest due to the increasing importance of hydrogen separation in a number of applications, e.g., hydrogen-powered fuel cells. An important issue in the context of MG membranes is the hydrogen-induced embrittlement and efforts to understand the role played by hydrogen in the mechanical properties, especially yielding and plastic deformation behavior, of MGs are being made. In this study, therefore, an attempt was made by performing nanoindentation tests with cube-corner and spherical indenter tips on a series of Ni–Nb–Zr amorphous alloy ribbons to investigate the hydrogen effects on nanohardness …

Probing Nanoscale Damage Gradients In Irradiated Materials With Spherical Nanoindentation, Nathan Mara, Siddhartha Pathak, Yongqiang Wang, Russ Doerner, Surya Kalidindi

Nanomechanical Testing in Materials Research and Development V

We discuss applications of spherical nanoindentation stress-strain curves in characterizing the local mechanical behavior of materials with modified surfaces. Using ion-irradiation on tungsten as a specific example, we show that a simple variation of the indenter size (radius) can identify the depth of the radiation-induced-damage zone, as well as quantify the behavior of the damaged zone itself. Using corresponding local structure information from electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM) we look at (a) the elastic response, elasto-plastic transition, and onset of plasticity in ion-irradiated tungsten under indentation, and compare their relative mechanical behavior to the unirradiated state, …

In-Situ Nano-Mechanical Tests In The Light Of Μlaue Diffraction, Thomas Cornelius, Cedric Leclere, Zhe Ren, Anton Davydok, Olivier Thomas

Nanomechanical Testing in Materials Research and Development V

In the recent past, low-dimensional materials attracted enormous attention due to the extraordinary properties found for nanostructures compared to their bulk counterparts. For instance, micro- and nano-mechanical tests revealed an increasing yield strength with decreasing size of the structure reaching the ultimate limit of the material for nanowires. While bulk fcc metals fail at stresses of few MPa, ultra-high strengths were demonstrated for gold nanowires with an elastic limit of few GPa [1, 2]. Additionally, while semiconductors such as Si and InSb are brittle at room temperature and become ductile at elevated temperatures of few hundred degrees Celsius, pillars of …

Nano-Scale Behavior Of Irradiated Nano-Structured Alloys, David Armstrong, John Waite, Steve Fitzgerald, Angus Wilkinson, Alan Xu, T. Ben Britton

Nanomechanical Testing in Materials Research and Development V

Future fast neutron fusion and fission nuclear systems will be subjected to levels of radiation damage from fast neutrons which is significantly higher than the current generation of nuclear power stations. This will require innovative materials solutions to allow long term mechanical stability of reactors. One proposed class of materials are nanostructured alloys where the large number of interfaces allow for recombination defects and reduce the degree of radiation hardening seen. However their response under irradiation has not thoroughly been studied. In this work, two irradiated nanostructured alloys have been studied W-5%Re in both a nanostructured and annealed variant and …

Underpinning And Benchmarking Multi-Scale Models With Micro- And Nanoscale Experiments, Kevin Hemker, Zafir Alam, Suman Dasupta, David Eastman, Madhav Reddy, Paul Rottman

Nanomechanical Testing in Materials Research and Development V

Predictive models of materials behavior depend on: accurate databases of constitutive material properties, identification of underlying deformation mechanisms, and the availability of experimentally measured benchmarks with which to compare. Micro- and nano-scale experiments can be used to facilitate collection of salient mechanical properties of individual phases at appropriate temperatures, chemistries and microstructural states. Coupling with TEM observations allows one to identify underlying deformation mechanisms and to imbibe models with the requisite fundamental physics and materials science. Simulations must be benchmarked with experiments, conducted at scale with relevant material volumes and identifiable microstructures. This presentation will outline efforts to characterize the …

Anisotropy Of Ultrafine-Lamellar And Nanolamellar Pearlitic Structures Revealed By In-Situ Micro Compression Testing, Marlene Kapp, Anton Hohenwarter, Stefan Wurster, Bo Yang, Reinhard Pippan

Nanomechanical Testing in Materials Research and Development V

Applying severe plastic deformation to pearlitic steels leads to a transformation of the random ultrafine-lamellar (ufl) colony structure to a nanolamellar (nl) composite. The distinct reduction of the interlamellar spacing generates a high-strength steel with a strength of up to 3.7 GPa, which can readily be produced. Additionally, the ferrite and cementite lamellae align in a preferential direction giving rise to an anisotropic mechanical response.

The aim of this work is to determine the material anisotropy in terms of flow stress and deformation behavior in the nl state and to compare it with its ufl state. Thus, micron sized samples …

In-Situ Mechanical Testing At The Synchrotron, Steven Van Petegem

Nanomechanical Testing in Materials Research and Development V

A major challenge in metallurgy is to understand the relation between the microstructure of a metal and its behaviour under an applied load or temperature. This requires a detailed characterization of the evolution of the microstructure at different length scales through the determination of the crystal structure, defect density, grain size distribution, texture etc.

During last decade in-situ mechanical testing under synchrotron radiation has become a widespread tool to investigate the evolution of the microstructure of single and polycrystals during deformation [1]. Many such in-situ deformation tests are performed during continuous or interrupted uniaxial tensile and/or compression tests. Several microstructural …

In-Situ Strain Softening And Strain Hardening Of Natural Geomaterials On The Microscale, Younane Abousleiman, Katherine Hull, Ghaithan Al-Muntasheri, Peter Hosemann, Scott Parker, Cameron Howard

Nanomechanical Testing in Materials Research and Development V

Gas shale has proven to be a good candidate for mechanical characterization using nanoindentation. However, this natural material composed of nano-granular clay and microscale non-clay minerals also includes within its matrix a polymeric material. This kerogen biopolymer is interbedded and intertwined with the clay and non-clay minerals at almost all scales. Figure 1(a) demonstrates the nature of interlacing that occurs between shale rock and organic matter.

Kerogen within the shale matrix has been mechanically characterized using nanoindentation to determine Young’s modulus and hardness such as in the work by Zeszotarski et al. 2004. As a polymer kerogen not only has …

Nanoindentation-Based Mechanical Spectroscopy Of Wood Cell Walls, Joseph Jakes

Nanomechanical Testing in Materials Research and Development V

Mechanical spectroscopy is the assessment of a mechanical index, such as the viscoelastic Young’s modulus or the plastic flow stress, across a broad spectrum of time scale, deformation rate, temperature, or moisture content. In addition to providing thorough mechanical characterization, which is useful to predict material performance over a wide range of conditions, mechanical spectroscopy also provides information about the microphysical processes which are causally linked to the properties. Recently, broadband nanoindentation creep (BNC) has been developed to measure viscoplastic properties across 4-6 decades of strain rate and broadband nanoindentation viscoelasticity (BNV) to measure viscoelastic properties across greater than 4 …

In-Situ Observation Of The Onset Of Plastic Deformation By Prismatic Loop Emission, Sang Ho Oh

Nanomechanical Testing in Materials Research and Development V

We report direct observations on the incipient plasticity of dislocation-free single crystal Au [110] nanowires by in situ transmission electron microscopy nanomechanical testing. The diameter of the tested nanowires ranged from ~ 80 nm to 350 nm and the length-to-diameter ratio was larger than 5. The top end of all [110]-oriented Au nanowires is bound by two inclined {111} faces in a wedge shape, on the other hand the side faces consist of four large {111} and two small {100} planes, resulting in a truncated rhombic cross-section. In our deformation setup where the wedge-shaped growth end of nanowire was compressed …

Importance Of Dynamics In Small Scale Mechanical Testing: Fast Constant Strain Rate And Ballistic Testing, Sudharstan Phani, Warren Oliver

Nanomechanical Testing in Materials Research and Development V

Recent advances in electronics have enabled nanomechanical measurements with very low noise levels at fast time constants and high data acquisition rates. Nanomechanical testers with sub-nanometer noise levels at a displacement time constant of 20µs are currently available which open the doors for a wide range of ultra-fast nanomechanical testing. It not only enables accurate measurement of materials’ response during a dynamic event such as strain burst (pop-in) during micropillar or indentation testing, but also enables fast indentation tests. However, fast testing requires a precise understanding of the instrument’s dynamic response along with the time constants of the measurement signals. …

Effect Of Hydriding On Nanoscale Plasticity Mechanisms In Nanocrystalline Palladium Thin Films, Behnam Amin Ahmadi, Hosni Idrissi, Marc Fivel, Ranaud Delmelle, Stuart Turner, Thomas Pardoen, Joris Proost, Dominique Schryvers

Nanomechanical Testing in Materials Research and Development V

Thin palladium (Pd) membranes constitute an enabling material in hydrogen permeation and sensing applications. During hydriding of Pd, as long as the H/Pd (atomic ratio) stays below α_SSmax≈0.02, the α-Pd with face centered cubic (fcc) lattice will expand from 3.889 Å to 3.895 Å. When the ratio reaches 0.02 a β-phase, again fcc based, having a lattice constant near 4.025 Å appears which induces a 10% volume change. In the present work, nanoscale plasticity mechanisms activated in sputtered nanocrystalline (nc) Pd thin films subjected to hydriding at different hydrogen pressures have been investigated for the first time using …

Effect Of Hydrogen On The Nucleation And Motion Of Dislocations, Mohammad Zamanzade, Jorge Velayarce, Christian Motz, Oscar Torrents Abad, Afrooz Barnoush

Nanomechanical Testing in Materials Research and Development V

Conventional mechanical tests are costly, time consuming, and due to their large scale, not very successful in obtaining mechanistic information. In contrast, the local method like nanoindentation, compression or bending test of micro pillars have comprehensive ranges of possibilities to achieve an essential understanding about the influence of substitutional atoms and/or interstitial atoms (e.g., hydrogen and nitrogen) on the mechanical properties like Young´s modulus, Gibbs free energy for homogeneous dislocation nucleation, dislocation line energy and also friction stress. These methods allow us to measure the mechanical behavior in simulated environments and atmospheres close to the routine industrial applications.

Nanoindentation was …