Download or read book A Transmission Electron Microscopy Study of the Deformation Behavior Underneath Nanoindents in Nano scale Al TiN Multilayered Composites written by and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Nano-scale multilayered Al-TiN composites were deposited with DC magnetron sputtering technique in two different layer thickness ratios - Al:TiN = 1:1 and Al:TiN = 9:1. The Al layer thickness varied from 2 nm to 450 nm. The hardness of the samples was tested by nanoindentation using a Berkovich tip. Cross-sectional Transmission Electron Microscopy (TEM) was carried out on samples extracted with Focused Ion Beam (FIB) from below the nanoindents. This paper presents the results of the hardness tests in the Al-TiN multilayers with the two different thickness ratios and the observations from the cross-sectional TEM studies of the regions underneath the indents. These studies showed remarkable strength in the multilayers, as well as some very interesting deformation behavior in the TiN layers at extremely small length scales, where the hard TiN layers undergo co-deformation with the Al layers.

Download or read book An Investigation of the Deformation Behaviour of Ni3ai Using Nanoindentation and Nanoscratch Methods written by Pui-Ching Wo and published by Open Dissertation Press. This book was released on 2017-01-26 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation, "An Investigation of the Deformation Behaviour of Ni3AI Using Nanoindentation and Nanoscratch Methods" by Pui-ching, Wo, 胡佩晶, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: Abstract of thesis entitled An Investigation of the Deformation Behaviour of Ni Al Using Nanoindentation and Nanoscratch Methods submitted by Wo Pui Ching for the degree of Doctor of Philosophy at the University of Hong Kong in August 2005 Rapid advancements in micro- and nano-technology have made it vital for scientists to understand the mechanical behaviour of materials at the submicron length scale. The recent invention of nanoindenter and nanoscratch testers enables convenient testing of submicron volume deformation. Mechanical properties such as initial yield and subsequent plastic flow are found to exhibit size dependency and behave stochastically. The recent discovery that well-annealed crystal cannot sustain elastic loading indefinitely has re-focused attention on the origin and mechanism of incipient plasticity at the sub-micron length scale. In this study, constant-load nanoindentations were performed within a single Ni Al grain. The waiting time for plastic deformation after prolonged elastic contact was found to be statistically distributed. At high applied loads, the waiting time distribution was exponentially decaying, so that longer waiting times were rarer. This form of distribution is consistent with the picture of homogeneous nucleation of dislocations. At lower applied loads, peaked Poisson-like distributions were observed, and the most probable waiting time (the peak) decreased as the load increased. This form of distribution suggests that the mechanism is more complicated than homogeneous nucleation of dislocations. A mechanism which involves the climb growth of an atomic sized dislocation loop is proposed. i The yielding behaviour with an additional tangential traction is another interesting issue. In this study, constant-load scratching was performed after a period of static elastic load application. Within a narrow range of normal loads between elastic and plastic behaviour, incipient plasticity was observed during scratching. At this intermediate load, initial yielding was sensitive to spatial inhomogeneity, and was influenced by the elastically deformed volume prior to scratching. Plastic deformation on nanoscratches and cube-corner nanoindents were observed through a transmission electron microscope. The cube-corner indents were found to be surrounded by dense dislocation clouds, which were larger than the Oliver-Pharr equation would lead us to expect. This provides direct evidence for the hypothesis, already argued in several studies, that the breakdown of the Nix-Gao model for indentation size effect for hardness is due to the expansion of the geometrically-necessary-dislocation zone. Slip transmission behaviour at grain boundaries was also studied. Nanoindentations were performed at various distances from some selected grain boundary segments in pure and boron-doped Ni Al. Hardness was found to be ineffective in probing the intergranular slip transmission behaviour in undoped samples. However, topographical information of the indents in pure Ni Al obtained from SEM and AFM examination revealed a strong correlation between the intergranular slip behaviour with the misorientation between the slip systems across the grain boundary. This relationship was not observed in boron-doped Ni Al, probably due to preferential boron segrega

Download or read book In Situ Nanoindentation in a Transmission Electron Microscope written by Andrew Murphy Minor and published by . This book was released on 2002 with total page 246 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Atomistic Studies of Deformation Mechanisms in Nanoscale Multilayered Metallic Composites written by Shuai Shao and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The goal of this thesis is to understand the interaction between dislocations and various metallic interfaces in nanoscale metallic multilayers (NMM). At lower strain rates, this mean understanding the effect of interfaces to the strain hardening of the NMMs; at higher strain rates, this means the effect of the interfaces on the spallation strengths of the NMMs. NMMs possess ultra-high strength level which is owing to the interactions between single dislocations (i.e. no pile-up) and interfaces. In this thesis, aiming at the goal, using atomistic simulations several nanoscale metallic multilayers subjected to different loading conditions and strain rates are being considered.

Download or read book Defects and Deformation in Nanostructured Metals written by Christopher Earl Carlton and published by . This book was released on 2009 with total page 394 pages. Available in PDF, EPUB and Kindle. Book excerpt: A better understanding of how the nanoscale environment affects the mechanical properties of materials, in particular metallic nanoparticles and nanocrystalline metals is vital to the development of next generation materials. Of special interest is obtaining a fundamental understanding of the inverse Hall-Petch Effect in nanocrystalline metals, and nanoindentation in individual nanoparticles. Understanding these subjects is critical to understanding how the mechanical properties of materials are fundamentally affected by nanoscale dimensions. These topics have been addressed by a combination of theoretical modeling and in-situ nanoindentation transmission electron microscopy (TEM) analysis. Specifically, the study of the inverse Hall-Petch effect in nanocrystalline metals will be investigated by a thorough review of the literature followed by a proposed novel theoretical model that better explains the experimentally observed behavior of nanocrystalline metals. On the other hand, the nanoindentation of individual nanoparticles is a very new research topic that has yet to aggregate a large body of experimental data. In this context, in-situ TEM nanoindentation experiments on silver nanoparticles will be first performed to determine the mechanisms of deformation in these nanostructures. A theoretical explanation for the observed deformation mechanisms will be then developed and its implications will be discussed. In addition to nanoparticles, this study will also provide unique and valuable insight into the deformation mechanisms of nanopillars, a growing area of research despite much controversy and speculation about their actual mechanisms of deformation. After studying the novel behavior of both nanocrystalline metals and nanoparticles, useful applications of both classes of materials will be explored. The discussion of applications will focus on utilizing the interesting behaviors explored in the dissertation. Of particular interest will be applications of nanoparticles and nanocrystalline materials to coatings, radiation resistance and super-plastic materials.

Download or read book In Situ Transmission Electron Microscopy Characterization of Nanomaterials written by Joon Hwan Lee and published by . This book was released on 2013 with total page 226 pages. Available in PDF, EPUB and Kindle. Book excerpt: With the recent development of in situ transmission electron microscopy (TEM) characterization techniques, the real time study of property-structure correlations in nanomaterials becomes possible. This dissertation reports the direct observations of deformation behavior of Al2O3-ZrO2-MgAl2O4 (AZM) bulk ceramic nanocomposites, strengthening mechanism of twins in YBa2Cu3O7−x (YBCO) thin film, work hardening event in nanocrystalline nickel and deformation of 2wt% Al doped ZnO (AZO) thin film with nanorod structures using the in situ TEM nanoindentation tool. The combined in situ movies with quantitative loading-unloading curves reveal the deformation mechanism of the above nanomaterial systems. At room temperature, in situ dynamic deformation studies show that the AZM nanocomposites undergo the deformation mainly through the grain-boundary sliding and rotation of small grains, i.e., ZrO2 grains, and some of the large grains, i.e., MgAl2O4 grains. We observed both plastic and elastic deformations in different sample regions in these multi-phase ceramic nanocomposites at room temperature. Both ex situ (conventional) and in situ nanoindentation were conducted to reveal the deformation of YBCO films from the directions perpendicular and parallel to the twin interfaces. Hardness measured perpendicular to twin interfaces is ~50% and 40% higher than that measured parallel to twin interfaces, by ex situ and in situ, respectively. By using an in situ nanoindentation tool inside TEM, dynamic work hardening event in nanocrystalline nickel was directly observed. During stain hardening stage, abundant Lomer-Cottrell (L-C) locks formed both within nanograins and against twin boundaries. Two major mechanisms were identified during interactions between L-C locks and twin boundaries. Quantitative nanoindentation experiments recorded during in situ experiments show an increase of yield strength from 1.64 to 2.29 GPa during multiple loading-unloading cycles. In situ TEM nanoindentation has been conducted to explore the size dependent deformation behavior of two different types (type I: ~ 0.51 of width/length ratio and type II: ~ 088 ratio) of AZO nanorods. During the indentation on type I nanord structure, annihilation of defects has been observed which is caused by limitation of the defect activities by relatively small size of the width. On the other hand, type II nanorod shows dislocation activities which enhanced the grain rotation under the external force applied on more isotropic direction through type II nanorod. The electronic version of this dissertation is accessible from http://hdl.handle.net/1969.1/148150

Download or read book Nanometrology Using the Transmission Electron Microscope written by Vlad Stolojan and published by Morgan & Claypool Publishers. This book was released on 2015-10-12 with total page 69 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Transmission Electron Microscope (TEM) is the ultimate tool to see and measure structures on the nanoscale and to probe their elemental composition and electronic structure with sub-nanometer spatial resolution. Recent technological breakthroughs have revolutionized our understanding of materials via use of the TEM, and it promises to become a significant tool in understanding biological and biomolecular systems such as viruses and DNA molecules. This book is a practical guide for scientists who need to use the TEM as a tool to answer questions about physical and chemical phenomena on the nanoscale.

Download or read book Small Scale Deformation using Advanced Nanoindentation Techniques written by Ting Tsui and published by MDPI. This book was released on 2019-06-11 with total page 168 pages. Available in PDF, EPUB and Kindle. Book excerpt: Small scale mechanical deformations have gained a significant interest over the past few decades, driven by the advances in integrated circuits and microelectromechanical systems. One of the most powerful and versatile characterization methods is the nanoindentation technique. The capabilities of these depth-sensing instruments have been improved considerably. They can perform experiments in vacuum and at high temperatures, such as in-situ SEM and TEM nanoindenters. This allows researchers to visualize mechanical deformations and dislocations motion in real time. Time-dependent behavior of soft materials has also been studied in recent research works. This Special Issue on "Small Scale Deformation using Advanced Nanoindentation Techniques"; will provide a forum for researchers from the academic and industrial communities to present advances in the field of small scale contact mechanics. Materials of interest include metals, glass, and ceramics. Manuscripts related to deformations of biomaterials and biological related specimens are also welcome. Topics of interest include, but are not limited to: Small scale facture Nanoscale plasticity and creep Size-dependent deformation phenomena Deformation of biological cells Mechanical properties of cellular and sub-cellular components Novel mechanical properties characterization techniques New modeling methods Environmentally controlled nanoindentation In-situ SEM and TEM indentation

Download or read book Radiation Effects on Mechanical Properties of Thin 3c sic Investigated by in Situ Nanoindentation Via Transmission Electron Microscopy written by Xuying Liu (Ph.D.) and published by . This book was released on 2020 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: In situ nanoindentation tests on thin 3C-SiC in a transmission electron microscope show small but non-negligible plastic deformation at room temperature. SiC is brittle in macroscopic studies but it can be become ductile when deformation occurs in small volumes. Here, we report such a brittle to ductile transition of 3C-SiC during nanoindentation of thin films (150-270 nm thick), and we reveal mechanisms of plastic deformation in situ. We find that plasticity in 3C-SiC is driven by dislocations, and that there is a pronounced plastic strain recovery at these length scales. We suggest that plastic deformation recovery arises from annihilation of transient dislocation extension driven by retracted external stress. In addition, we demonstrate that when the sample thickness is less than 90 nm, 3C-SiC becomes brittle again, and therefore the thickness of the films is important in determining whether the sample is brittle or ductile. In situ TEM nanoindentation tests on thin 3C-SiC irradiated at different radiation conditions indicate different mechanical behavior that is related to different microstructures. Samples irradiated at 600 [degrees]C 0.3 dpa and 600 2̐ʻC 3 dpa are easier to fracture under applied force than as-synthesized 3C-SiC. Long, straight, and simple crack paths are characteristic features for 600 [degrees]C 3 dpa samples, which is an evidence of easier fracture than 600 [degrees]C 0.3 dpa. However, 900 [degrees]C 3 dpa samples do not exhibit noticeable brittleness. Instead, they exhibit plastic deformation under applied force, which is the same as as-synthesized samples. Based on the microstructure of the irradiated samples, increasing the density of black spot defects that form at 600 [degrees]C degrades resistance to cracking, but the change of defect type to dislocation loops at 900 [degrees]C restores the plastic behavior. The results from this study are not consistent with macroscale analysis of fracture and cracking in irradiated SiC, which suggest different behavior and the microscale in irradiated as well as unirradiated SiC. These results therefore provide useful insights into the microscale properties of 3C-SiC which are important to multiscale simulation of 3C-SiC to predict mechanical performance of microelectromechanical systems, coatings, and next-generation fission reactor fuels.

Download or read book Development of Many body Potential for Deformation Study in Al TiN Nanolayered Composites written by Paul Simanjuntak and published by . This book was released on 2017 with total page 234 pages. Available in PDF, EPUB and Kindle. Book excerpt: A novel interatomic potential of ternary Al-TiN has been developed to study the deformation behavior of Al-TiN nanolaminates. The ternary nanolayered Al-TiN composite has attracted a lot of interest due to its combination of strength and ductility. The current analysis on the system has been primarily concentrated on continuum models which are inadequate to explain the key deformation events such as nucleation and interaction of dislocations. Progress in the preferred atomistic approach has been hampered however by the lack of available interatomic potential optimized for the ternary system. I developed a many-body potential based on embedded atomic model (EAM) by employing the force-fitting code Potfit to sample the energy and force data generated from the ab-initio molecular dynamics simulations of the ternary system using VASP code. The potential’s analytical EAM function was subsequently optimized and utilized to simulate structures of bulk Al & TiN and Al-TiN nanolaminates. I then focused on modeling the deformation behavior of Al-TiN multilayers under compression through classical molecular dynamics simulations. I found that the total bilayer thickness as well as volume ratio between TiN and Al nanolayers play a major role in controlling the dislocation nucleation and mobility and the stress accumulation at the layer interface and thus determine the deformation behavior and failure mechanisms of the nanolayered composites.

Download or read book Radiation Effects on Mechanical Properties of Thin 3c sic Investigated by in Situ Nanoindentation Via Transmission Electron Microscopy written by Xuying Liu (Ph.D.) and published by . This book was released on 2020 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: In situ nanoindentation tests on thin 3C-SiC in a transmission electron microscope show small but non-negligible plastic deformation at room temperature. SiC is brittle in macroscopic studies but it can be become ductile when deformation occurs in small volumes. Here, we report such a brittle to ductile transition of 3C-SiC during nanoindentation of thin films (150-270 nm thick), and we reveal mechanisms of plastic deformation in situ. We find that plasticity in 3C-SiC is driven by dislocations, and that there is a pronounced plastic strain recovery at these length scales. We suggest that plastic deformation recovery arises from annihilation of transient dislocation extension driven by retracted external stress. In addition, we demonstrate that when the sample thickness is less than 90 nm, 3C-SiC becomes brittle again, and therefore the thickness of the films is important in determining whether the sample is brittle or ductile. In situ TEM nanoindentation tests on thin 3C-SiC irradiated at different radiation conditions indicate different mechanical behavior that is related to different microstructures. Samples irradiated at 600 [degrees]C 0.3 dpa and 600 2̐ʻC 3 dpa are easier to fracture under applied force than as-synthesized 3C-SiC. Long, straight, and simple crack paths are characteristic features for 600 [degrees]C 3 dpa samples, which is an evidence of easier fracture than 600 [degrees]C 0.3 dpa. However, 900 [degrees]C 3 dpa samples do not exhibit noticeable brittleness. Instead, they exhibit plastic deformation under applied force, which is the same as as-synthesized samples. Based on the microstructure of the irradiated samples, increasing the density of black spot defects that form at 600 [degrees]C degrades resistance to cracking, but the change of defect type to dislocation loops at 900 [degrees]C restores the plastic behavior. The results from this study are not consistent with macroscale analysis of fracture and cracking in irradiated SiC, which suggest different behavior and the microscale in irradiated as well as unirradiated SiC. These results therefore provide useful insights into the microscale properties of 3C-SiC which are important to multiscale simulation of 3C-SiC to predict mechanical performance of microelectromechanical systems, coatings, and next-generation fission reactor fuels.

Download or read book Quantitative In Situ TEM Studies of Small Scale Plasticity in Irradiated and Unirradiated Metals written by Claire Chisholm and published by . This book was released on 2015 with total page 84 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this work, unirradiated and irradiated model body centered cubic (BCC) and face centered cubic (FCC) materials are investigated using advanced electron microscopy techniques to quantitatively measure local stresses and strains around defects, with the overarching goal of obtaining a fundamental understanding of defect physics. Quantitative in-situ transmission electron microscopy (TEM) tensile tests are performed with Molybdenum-alloy nano-fibers, functioning as a model BCC structural material. Local true stress and strain around an active Frank-Read type dislocation source are obtained using quantitative load-displacement data and digital image correlation. A mixed Frank-Read dislocation source, b=a/2[-1-11](112) with a line direction 20° from a screw orientation and length 177 nm, is observed to begin operating at a measured local stress of 1.38 GPa. The measured local true stress values compare very well to estimated stresses using dislocation radius of curvature, and a line-tension model of a large bow-out configuration, with differences of only ~1%. The degree to which the local true stresses can be measured is highly promising. However, the ultimate failure mode of these fibers, sudden strain softening after dislocation starvation and exhaustion, cannot be captured at the typical camera frame rate of 30 frames per second. Thus, fibers are mechanically tested while under observation with the Gatan K2-IS direct electron detector camera, where the frame rate is an order of magnitude larger at 400 fps. Though the increase in frame rate adds to the overall understanding of the sudden failure, by definitively showing that the nano-fibers break rather than strain soften, the failure mechanism still operates too quickly to be observed. In the final investigation of this BCC model structural alloy, the mechanical behavior of heavily dislocated, but unirradiated, and He1+ and Ni2+ irradiated nano-fibers are compared. Remarkable similarities are found in the mechanical data, as the two defect conditions exhibit similar yield strengths, ultimate tensile strengths, and number and size of load-drops. This similarity implies that, even if materials contain dissimilar individual defects, the collective defect behavior can result in similar mechanical properties. Thus, the origin of mechanical properties can be ambiguous and caution should be taken when extrapolating to different size scales. Furthermore, such similarities highlight the importance of in-situ observation during deformation. These experiments provide a key test of theory, by providing a local test of behavior, which is much more stringent than testing behaviors averaged over many regions. Advanced electron microscopy imaging techniques and quantitative in-situ TEM tensile tests are performed with Au thin-film as a model FCC structural material. These investigations highlight the various hurdles experimental studies must overcome in order to probe defect behavior at a fundamental level. Two novelly-applied strain mapping techniques are performed to directly measure the matrix strain around helium bubbles in He1+ implanted Au thin-film. Dark-field inline holography (DFIH) is applied here for the first time to a metal, and nano-beam electron diffraction (NBED) transient strain mapping is shown to be experimentally feasible using the high frame rate Gatan K2 camera. The K2 camera reduces scan times from ~18 minutes to 82 seconds for a 128x256 pixel scan at 400 fps. Both methods measure a peak strain around 10 nm bubbles of 0.7%, correlating to an internal pressure of 580 MPa, or a vacancy to helium ion ratio of 1V:2.4He. Previous studies have relied on determining the appropriate equation of state to relate measured or approximated helium density to internal bubble pressure and thus strain. Direct measurement of the surrounding matrix strain through DFIH and NBED methods effectively bypasses this step, allowing for easier defect interaction modeling as the bubble can be effectively simplified to its matrix strain. Furthermore, this study demonstrates the feasibility of fully strain mapping, in four dimensions, any in-situ TEM experiment. The final set of experiments with this model FCC structural material shows the attempted correlation of defect interactions and deformation behavior at the nano-scale. Experimental comparison of mechanical behavior from quantitative in-situ TEM tensile tests of focused ion beam (FIB) shaped, He1+ implanted, and FIB-shaped He1+ implanted Au thin-film show a wide range of behavior that could not be directly linked to irradiation condition. This is due to the large role that overall microstructural features, such as grain boundary orientation and texture, play in mechanical behavior at this size scale. However, these tests are some of the first to in-situ TEM mechanically strain single grain-boundaries free of FIB-damage. It is expected that, with well-defined grain orientations and boundaries, real conclusions can be made.

Download or read book Hetero twin Formation During Growth of Nano scale Al TiN Composites Experimental and DFT Studies written by and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: It is well known that high stacking fault energy metals such as Al do not form either growth twins or mechanical twins easily. Although mechanical twins in nanocrystalline Al have been observed under certain conditions, growth twins have never been observed. In this work, the authors report for the first time, through transmission electron microscopy (TEM), that Al layers, when deposited on TiN layers, tend to grow in a twin relationship to both the TiN layer and the underlying Al layer. The TiN layers assume the orientation of the Al layers below. Calculations using density functional theory (DFT) show that nitrogen termination in the [111] growth plane of the TiN layers favors the growth of twin oriented Al layers over these TiN layers. This finding provides a way to create a twin-modulated structure in Al with the inclusion of intermediate nm-scale layer of an ionic solid such as TiN. Al metal is resistant to twinning, as it has a high stacking fault energy (SFE) of> 150 mJ/m. Although twins have been observed in nano-scale grains of Al, and predicted by molecular dynamics (MD) simulations in conditions when the nanoscale grains are plastically deformed, no process or phenomenon has been reported yet in which the deposition of an intermediate layer of a different material phase causes the subsequent layer of Al to be deposited in the twin orientation. The authors show in this paper that it is possible to form Al layers in twin orientation to each other across polar TiN layers, if these are grown so that both the Al and TiN layers have a [111] surface as their growth front. Since the deposition of Al and TiN layers is used in the formation of diffusion barriers, and the mechanical properties of these nanoscale multilayers are also seen to be exceptional, it is important to investigate and understand their structure at the nanometer length scale, and thence to be able to control it. Moreover, these findings point out a method of introducing nano-scale twins in high SFE materials in general, and can potentially improve the properties of nano-layered materials.

Download or read book Deformation Behavior of Bulk Metallic Glasses and High Entropy Alloys by Nanoindentation written by Yuting Li (Industrial engineer) and published by . This book was released on 2013 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Nanoindentation has become a powerful tool in the measurement of the mechanical properties of diverse materials, such as metallic materials, polymer materials, and even biomaterials. In this thesis, three types of Zr-based bulk metallic glasses (BMGs) were investigated by nanoindentation. Our work focuses on the characterization of the hardness, the reduced modulus, and the deformation behavior under different indentation conditions. The study of the hardness and the reduced modulus is to access the effect of the indentation load on deformation behavior and to determine the inhomogeneous deformation. The morphological profiles of the residual indentation on the surface of the specimen after an indentation were observed by the atomic force microscope (AFM). Differential scanning calorimetry (DSC) measurements were performed to determine characteristic thermal properties, the glass transition temperature (T[g̳̳̳]), and the crystallization temperature (Tx̳). The serrated-flow behavior (or pop-in behavior) was investigated at different loading rates. It is concluded that the pop-in size gradually increases with the decrease in the loading rate and the increase of the indentation depth. And the research of the indentation tests on the several metallic glasses at different indentation rates indicates that a much higher critical strain rate will lead to the disappearance of flow serrations. Another type of material of a high-entropy alloy (HEA) was also investigated in this thesis. The hardness, reduced modulus, and deformation behavior were investigated by the indentation tests. Compared to Zr-based BMGs, this type of HEA has lower hardness and higher reduced modulus. Creep behavior was observed in the indentation tests. However, serrated flow behavior disappears. The microstructure of this HEA was investigated by the X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), and energy-dispersive spectroscopy (EDS). For the advanced research, the simulation of ion-implantation of HEAs was preformed, because the advanced reactor is one of the important potential applications of HEAs and advanced nuclear-energy systems, which will require materials that can withstand extreme reactor environments of high-temperature and high-doses radiation.

Download or read book Transmission Electron Microscopy Characterization of Nanomaterials written by Challa S.S.R. Kumar and published by Springer Science & Business Media. This book was released on 2013-12-09 with total page 718 pages. Available in PDF, EPUB and Kindle. Book excerpt: Third volume of a 40volume series on nanoscience and nanotechnology, edited by the renowned scientist Challa S.S.R. Kumar. This handbook gives a comprehensive overview about Transmission electron microscopy characterization of nanomaterials. Modern applications and state-of-the-art techniques are covered and make this volume an essential reading for research scientists in academia and industry.

Download or read book In Situ Nanoindentation in a Transmission Electron Microscope written by and published by . This book was released on 2002 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation presents the development of the novel mechanical testing technique of in situ nanoindentation in a transmission electron microscope (TEM). This technique makes it possible to simultaneously observe and quantify the mechanical behavior of nano-scale volumes of solids.

Download or read book Identifying Deformation and Strain Hardening Behaviors of Nanoscale Metallic Multilayers Through Nano wear Testing written by and published by . This book was released on 2016 with total page 13 pages. Available in PDF, EPUB and Kindle. Book excerpt: In complex loading conditions (e.g. sliding contact), mechanical properties, such as strain hardening and initial hardness, will dictate the long-term performance of materials systems. With this in mind, the strain hardening behaviors of Cu/Nb nanoscale metallic multilayer systems were examined by performing nanoindentation tests within nanoscratch wear boxes and undeformed, as-deposited regions. Both the architecture and substrate influence were examined by utilizing three different individual layer thicknesses (2, 20, and 100 nm) and two total film thicknesses (1 and 10 [mu]m). After nano-wear deformation, multilayer systems with thinner layers showed less volume loss as measured by laser scanning microscopy. Additionally, the hardness of the deformed regions significantly rose with respect to the as-deposited measurements, which further increased with greater wear loads. Strain hardening exponents for multilayers with thinner layers (2 and 20 nm, n ≈ 0.018 and n ≈ 0.022 respectively) were less than was determined for 100 nm systems (n ≈ 0.041). These results suggest that singledislocation based deformation mechanisms observed for the thinner systems limit the extent of achievable strain hardening. This conclusion indicates that impacts of both architecture strengthening and strain hardening must be considered to accurately predict multilayer performance during sliding contact across varying length scales.