Download or read book Study of Deformation Behavior of Nanocrystalline Nickel Using Nanoindentation Techniques written by Changli Wang and published by . This book was released on 2010 with total page 94 pages. Available in PDF, EPUB and Kindle. Book excerpt: Nanocrystalline materials with grain size less than 100 nm have been receiving much attention because of their unparallel properties compared with their microcrystalline counterparts. Because of its high hardness, nanocrystalline nickel has been used for MEMS. Long term thermomechnical properties and deformation mechanism at both ambient and elevated temperatures need to be evaluated which is vital for reliability of its applications as structural material. In this thesis, nanoindentation creep of nanocrystalline nickel with an as-deposited grain size of 14 nm was characterized at elevated temperatures. The nanoindentation creep rate was observed to scale with temperature and applied load (or stress), and could be expressed by an empirical power-law equation for describing conventional crystalline solids. Creep activation energy was found to be close to that for grain boundary self-diffusion in nickel. The activation volume was also evaluated using a stress relaxation technique. The creep results were compared with those for fine-grained nickel in the literature. Possible mechanisms were discussed in light of the creep rate and temperature ranges. To provide a direct comparison, uniaxial creep tests were conducted on nanocrystalline nickel with an as-deposited grain size of 14 nm at 398 K. It was found that stress exponents under the two test conditions are almost the same, indicating a similar creep mechanism. However, the strain rate measured by nanoindentation creep was about 100 times faster than that by uniaxial creep. The rate difference was discussed in terms of stress states and the appropriate selection of Tabor factor. To further explore the time-dependent plastic behavior, multiple unload-reload tests were conducted on electrodeposited nanocrystalline nickel in both compression and tension. A hysteresis was observed during each unload-reload cycle, indicating irreversible energy dissipation. The dissipated energy was evaluated and the energy dissipation rate was found to increase with the flow stress to the third power and sensitive to the stress state (tension or compression). A mechanistic model based on grain boundary sliding was proposed to describe the unload-reload behavior. Experimental results were found to be in good agreement with the model predictions, suggesting the observed hysteresis was indeed caused by grain boundary sliding.

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 The Systematic Study of Deformation and Fracture Mechanism of Nano Crystalline Nickel written by Manish Sharma and published by . This book was released on 2020-04-14 with total page 136 pages. Available in PDF, EPUB and Kindle. Book excerpt: The present study is initiated with the specific objective of observing, both during and after deformation in Nickel Crystal by TEM experiments, the mechanisms of the deformation and fracture using state of the art experimental tools in high purity, fully dense nanocrystalline metals with a narrow range of gain sizes. The goal is to develop a strategy to reach the rational design of nanomaterials i.e. nanocrystal Nickel with modelled and controlled particles size, morphology, orientation, and crystal structure, i.e. purpose-built nanomaterials, to probe, tune, and optimize their physical, chemical properties and mechanical properties. In our view, to achieve such ambitious challenge, the most pertinent parameter to monitor is the dislocation mechanism of the system. In an attempt to take part in the fascinating nanoworld, and to contribute to its ambitious challenges, the present review will expose the outcome of a novel general concept of nucleation, growth, thin film processing method. Now a days, new concepts of nanocomposites and nano glasses are also being investigated with special emphasis on ceramic composites to increase their strength and toughness. There appears to be a great potential for applications in the near future for nanocrystalline materials. The extensive investigations in recent years on structure-property correlations in nanocrystalline materials have begun to unravel the complexities of these materials, and pave the way for successful exploitation of alloy design principles to synthesize better materials than hitherto available. For the first time, direct and compelling conclusive evidence of the deformation mechanism crossover is provided. In addition, unexpected dislocation activities are also observed in grains as small as 5 nm. Nano beam diffraction observations revealed that a nanocrystalline grain with a size of about 20 nm may experience ultrahigh elastic strain during deformation and the implication of this finding is discussed in detail. Also Understanding the formation mechanisms and role of grain agglomerates in nanocrystalline metals is expected to directly impact the processing methods required to create nanocrystalline metals with improved strength and ductility.

Download or read book The Nanoindentation Size Effects of Creep written by Han Li and published by . This book was released on 2017-01-27 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation, "The Nanoindentation Size Effects of Creep" by Han, Li, 李晗, 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: The Nanoindentation Size Effects of Creep Submitted by LI, Han for the degree of Master of Philosophy at The University of Hong Kong in December, 2004 Nanoindentation provides convenient and localized measurements of the mechanical properties of materials, and is an especially useful technique for the study of thin films and materials of small volumes. Previous investigations showed that the submicron contacts with the rigid indenting punch could yield creep at an enormous speed at low homologous temperatures, where the same material in bulk condition would normally not exhibit any creep. The influence of this time dependent deformation on the calculation of material properties has been investigated, and compensation methods have been proposed, but the fundamental mechanisms leading to such a high creep rate remain unknown. It would also be interesting to establish if creep behavior and its mechanisms change as the indent size diminishes towards incipient plasticity, and if so, how. The aim of this study is therefore to investigate the characteristics and mechanisms of the nanoindentation creep in different materials over a wide range of indent sizes (from several nm to above one micron). A depth-sensing, constant load creep test was used to measure the stress exponent, chosen to quantify indentation creep behavior, at different indentation sizes on both Ni Al (111) single crystal, polycrystalline Al, amorphous fused quartz and nanocrystalline Ni-at25%Al alloy films with a spectrum of grain sizes. bExperimental results demonstrated that the stress exponents in all materials increased significantly as the indent size increased, exhibiting an intense size effect. The near unity stress exponent of Al in the smallest indent suggests that the creep mechanism is likely to be diffusional flow, and a simple pipe-diffusion model is proposed as a theoretical explanation. For the amorphous fused quartz, the size effect on the stress exponent can be explained by a reduction of the localized shear volume as the indent size decreases. For the nanocrystalline thin films with different average grain sizes, the stress exponent was also found to increase with grain size at the same nominal peak load. This is ascribed to the operation of increasing dislocation activities near grain boundaries at larger grain sizes. A preliminary study of the initial contact behavior of a nanocrystalline film during nanoindentation is also presented. It is well known that single crystals with low defect densities can support stresses near the theoretical limit without yielding, and incipient plasticity is usually manifested in the indentation curve as a sudden displacement burst, associated with dislocation nucleation and multiplication. The initial contact deformation of nanocrystalline materials appears to be more complicated and less well documented. Through nanometer scale indentation tests on a nanocrystalline Ni-25at.%Al alloy thin film, three representative deformation modes were observed by immediate pre and post-indentation atomic force microscopy. One exhibited near elastic deformation, with elastic modulus equal to the upper limit for all loads and even close to the bulk value. In the other two modes, the deformation was elastoplastic from the very beginning. Strain burst was rarely observed. 473 words (main body) DOI: 10.5353/th_b3069638 Subje

Download or read book An Investigation for Fracture Toughness and Creep Behavior in Carbon Doped Nanocrystalline Nickel written by and published by . This book was released on 2002 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Electrodeposited nanocrystalline nickel that exhibits extraordinary high strength would be a promising candidate for a structural material. The potential engineering applications of nanocrystalline materials need more detailed study on deformation and fracture toughness at room and elevated temperatures under tensile loading. Fracture toughness and creep deformation of nanocrystalline Ni, Ni-C, and Ni-B studied under the course of this research. The results have been published in four (4) papers in refereed journals and have been presented in several international symposiums. One additional manuscript has been submitted recently for publication. Tensile behavior and fracture in nickel and carbon doped nanocrystalline nickel, Creep behavior of nanocrystalline nickel at 290 and 373 K, Creep in boron-doped nanocrystalline nickel, R-Curve characterization of the fracture toughness of nanocrystalline nickel thin sheets, Effect of interstitials on tensile strength and creep in nanostructured Ni.

Download or read book Deformation Mechanisms of Nanocrystalline Nickel Studied by In situ X ray Diffraction written by Stefan Brandstetter and published by . This book was released on 2009 with total page 195 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Mechanical Properties of Nanocrystalline Materials written by James C. M. Li and published by CRC Press. This book was released on 2011-09-02 with total page 346 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book concentrates on both understanding and development of nanocrystalline materials. The original relation that connects grain size and strength, known as the Hall-Petch relation, is studied in the nanometer grain size region. The breakdown of such a relation is a challenge. Why and how to overcome it? Is the dislocation mechanism still operating when the grain size is very small, approaching the amorphous limit? How do we go from the microstructure information to the continuum description of the mechanical properties?

Download or read book Deformation mechanism Maps written by H. J. Frost and published by Pergamon. This book was released on 1982 with total page 184 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Mechanical Behavior of Nanocrystalline Materials and Application of Shear Punch Test written by and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Nanocrystalline (nc) materials show superior strength compared to conventional grain size materials. Synthesizing bulk nc materials often results in small quantities, which limits making large scale specimens for conventional testing such as tensile, compression etc. In such instances, miniaturized specimen test techniques are very useful. The intent of the present work was to study the mechanical behavior of nc materials and also to develop a miniaturized specimen testing procedure -"shear punch test (SPT)" for nc material testing. A new setup for SPT was built and the testing procedure was standardized using different conventional metals. A linear correlation between SPT measurements and tensile data was established. The effect of test setup parameters such as specimen thickness and the die-punch clearance was studied in order to rationalize the technique. Using Finite Element Analysis, SPT was modeled and the physical basis of through-thickness plastic zone development at shear yield measurements was examined. The deformation behavior and the state of stress at different stages of the punching operation during an SPT test were studied. In order to understand the mechanical behavior of various materials from conventional to amorphous through nano regime, studies were done on investigating the mechanical properties of a Zr -- based amorphous alloy (BMG -- 11 alloy) using SPT. Strain rate dependent deformation behavior was studied and at high strain rates reduced strength was attributed to thermal softening. In order to examine the applicability of SPT for testing of nc materials, initial experiments were carried out on electrodeposited nc Cu. The SPT and mini tensile experiments were conducted and compared. An attempt was made to examine the strain rate effect. The SPT technique was extended to measure the strain rate sensitivity and the activation volumes and compared with the isostrain rate tensile test measurements. The nc materials pure Fe, Fe-Pb allo.

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 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 Multiscale modeling of contact plasticity and nanoindentation in nanostructured FCC metals written by Virginie Dupont and published by . This book was released on 2008 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: ABSTRACT Nanocrystalline thin films are materials with a grain size less than 100 nm which are commonly used to fabricate microscale electro-mechanical devices. At such small scale, nanoindentation is the only standard experimental technique to study the mechanical properties of thin films. However, it is unclear if the continuum laws commonly used in nanoindentation analysis of polycrystalline materials are still valid for nano-grained metals. It is therefore critical to better understand the behavior of nanocrystalline materials under nanoscale contact. This dissertation summarizes the results of atomistic simulations aimed at modeling the nanoindentation of nanocrystalline metal thin films for which the grain size is smaller than the indenter diameter. The nanoindentation of aluminum thin films was first studied using the Quasicontinuum method, which is a concurrent multiscale model where regions of small gradients of deformations are represented as a continuum medium by finite elements, and regions of high gradients of deformation are fully-treated atomistically. Two embeddedatom- method potentials for aluminum were used in order to study the effect of the potential on the nanoindentation behavior. The aim is to better understand the effects of a grain boundary network on the plasticity and the underlying mechanisms from an atomistic perspective. Our results show that a grain boundary network is the primary medium of plasticity at the nanoscale, via shear banding that causes flow serration. We also show that although the dislocation mechanisms are the same, the mechanisms involving grain boundaries are different depending on the interatomic potential. In a second part, abnormal grain growth in aluminum thin films under nanoindentation is studied using both the Quasicontinuum method and parallel molecular dynamics simulations. The effects of the potential, the nature of the indenter and of its size on the grain growth under nanoindentation are investigated. Our results show that the potential used, which can be related to the purity of the material, can reduce grain growth. We also show that the size and material used for the indenter both have significant effects on grain growth. More specifically, grain growth under the indenter is found to occur via atom diffusion if the indenter is of the same material as the thin film. Finally, the sample size effects were studied using parallel molecular dynamics simulations on nickel thin films and nanowires. Single crystals with different sizes are modeled in order to investigate the effects of the free boundaries as well as of the thickness of the samples. It is shown that the yield point and the incipient plasticity mechanisms are similar for all simulations. However, the hardness of the nanowires is found to decrease with the nanowire size during nanoindentation, due to the interaction of prismatic loops and dislocations with the free boundaries. This dissertation has shed light on the plastic deformation mechanisms under nanoscale contact. The results obtained will help the scientific community gain a better understanding of the behavior of nanomaterials, which will lead to the fabrication of more reliable nanodevices.

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 Applied Nanoindentation in Advanced Materials written by Atul Tiwari and published by John Wiley & Sons. This book was released on 2017-08-18 with total page 935 pages. Available in PDF, EPUB and Kindle. Book excerpt: Research in the area of nanoindentation has gained significant momentum in recent years, but there are very few books currently available which can educate researchers on the application aspects of this technique in various areas of materials science. Applied Nanoindentation in Advanced Materials addresses this need and is a comprehensive, self-contained reference covering applied aspects of nanoindentation in advanced materials. With contributions from leading researchers in the field, this book is divided into three parts. Part one covers innovations and analysis, and parts two and three examine the application and evaluation of soft and ceramic-like materials respectively. Key features: A one stop solution for scholars and researchers to learn applied aspects of nanoindentation Contains contributions from leading researchers in the field Includes the analysis of key properties that can be studied using the nanoindentation technique Covers recent innovations Includes worked examples Applied Nanoindentation in Advanced Materials is an ideal reference for researchers and practitioners working in the areas of nanotechnology and nanomechanics, and is also a useful source of information for graduate students in mechanical and materials engineering, and chemistry. This book also contains a wealth of information for scientists and engineers interested in mathematical modelling and simulations related to nanoindentation testing and analysis.

Download or read book Mechanical Properties and Deformation Behavior of Materials Having Ultra Fine Microstructures written by M. Nastasi and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 616 pages. Available in PDF, EPUB and Kindle. Book excerpt: In an attempt to meet the demand for new ultra-high strength materials, the processing of novel material configurations with unique microstructure is being explored in systems which are further and further from equilibrium. One such class of emerging materials is the so-called nanophased or nanostructured materials. This class of materials includes metals and alloys, ceramics, and polymers characterized by controlled ultra-fine microstructural features in the form oflayered, fibrous, or phase and grain distribution. While it is clear that these materials are in an early stage of development, there is now a sufficient body of literature to fuel discussion of how the mechanical properties and deformation behavior can be controlled through control of the microstructure. This NATO-Advanced Study Institute was convened in order to assess our current state of knowledge in the field of mechanical properties and deformation behavior in materials with ultra fine microstructure, to identify opportunities and needs for further research, and to identify the potential for technological applications. The Institute was the first international scientific meeting devoted to a discussion on the mechanical properties and deformation behavior of materials having grain sizes down to a few nanometers. Included in these discussions were the topics of superplasticity, tribology, and the supermodulus effect. Lectures were also presented which covered a variety of other themes including synthesis, characterization, thermodynamic stability, and general physical properties.

Download or read book Computational Modelling of the Mechanical Behavior of Nanocrystalline Metals Based on the Deformation Mechanisms and Their Transitions written by Baozhi Zhu and published by . This book was released on 2006 with total page 152 pages. Available in PDF, EPUB and Kindle. Book excerpt: There has been a growing research interest in understanding the mechanical behaviors and the deformation mechanisms of nanocrystalline metals and alloys in the past a few decades, due to their extraordinary mechanical prosperities, such as high strength, hardness, and wear resistance, which have great potentials in engineering applications. As grain sizes in crystalline metals and alloys transit down to the lower end of the nanometer range, the plastic deformations are no longer dominated by the intragrain dislocation activities. Instead deformations assisted by grain boundary start to play a more important role in deciding the mechanical response of the bulk materials, as the interfacial volume fraction increases with the reduction of grain sizes. A polycrystalline constitutive theory is developed in the form of the extend aggregate Taylor model of Asaro and Needleman for the nanocrystalline metals. The plastic deformation description is based on the Asaro, Krysl and Kad (AKK) model, which considers deformation mechanisms such as the emission of perfect, partial dislocations and deformation twins from grain boundary and grain boundary sliding when the grain size is sufficiently small in the nanometer regime (less than 100nm), and their transitions are governed by the factors such as grain size, stacking fault energy, temperature, and strain rate, etc. Therefore the effect of grain size distributions in addition to the mean grain size is considered important on the mechanical response in this constitutive theory. The grain size distributions can be simulated with the experimentally determined lognormal distributions for the electro-deposited nanocrystalline metals for example. Numerical simulations are carried out for nanocrystalline Ni, Cu, Al and Pd, and the simulated phenomena include the mechanical response of these materials when subjected to uniaxial tension and compression under different deformation rates, texture development under high pressure torsion (HPT), and the grain growth effect during nanoindentation, etc, where the contribution of each deformation mechanism is carefully studied. The obtained numerical results are in reasonably good agreement with the experiments. Due to the fact that the deformation mechanisms in nanostructured materials are not yet fully understood, this constitutive theory will need to be further improved with the future findings of deformation mechanisms, which this theory has the flexibility to easily incorporate.

Download or read book In Situ TEM Studies of Deformation Mechanisms in Nanoindentation of Ultrafine grained and Nanocrystalline Metals written by Miao Jin and published by . This book was released on 2006 with total page 182 pages. Available in PDF, EPUB and Kindle. Book excerpt: The mechanical properties of ultrafine-grained and nanocrystalline materials have received a great deal of recent attention because of their unusual and promising values. However, some of the most important mechanisms of deformation remain unclear. To address this issue, an in situ nanoindentation stage has been used in a transmission electron microscope to explore the deformation behaviors of nanocrystalline aluminum, ultrafine-grained aluminum, and ultrafine-grained iron in real time.