Download or read book On the Mechanical Behavior of Nanocrystalline Ni Based Alloys written by Thomas Robert Koenig and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The fabrication and characterization of a ternary nanocrystalline (NC) stabilized Ni-Cu-P alloy was reported. The complexities of fabrication a low contamination, equiaxed NC material was discussed. For comparison, elemental Ni was prepared via sputter deposition, highlighting the difficulty in fabricating an idealized structure within the confines of the parametric space. An exchange between the ideal grain size distribution and film coalescence was discussed with the ramifications of substrate heat, deposition pressure, and deposition rate considered. These results were then compared to a kinetic model to assess the validity of the model and its ability to capture the complex growth behavior noted between the Ni films.A series of ternary NC Ni-Cu-P thin films were fabricated, characterized, and loaded via in situ annealing and nanoindentation. Examination of the thermal stability behavior revealed differences in precipitation behavior as a function of Cu and P solute content. Furthermore the Ni-40Cu-0.6P (at.%) alloy was noted as the only NC stabilized composition at 550 ©2℗ʻC. The Ni-40Cu-0.3P deposit developed nanoscale precipitates upon annealing to temperatures of 550 ©2℗ʻC which ultimately resided in the matrix. It was found that the ternary Ni-Cu-P films are harder than previously studied binary Ni-1P and Ni-4P (at.%) systems. Adding Cu to the Ni-P system promoted solid solution strengthening which mitigated softening in those binary alloys previously reported.A MEMS device was then employed for in situ thermomechanical testing of the stabilized Ni-40Cu-0.6P film for comparison with a binary Ni-40Cu counterpart. Digital image correlation (DIC) was employed to data mine microstructural evolutions that occurred while the films were loaded. Increased fracture strength was reported with the P solute addition, irrespective of the loading temperature. The ramifications of adding this stabilizing solute were discussed with respect to the fracture profile and microstructural stability.

Download or read book The Effects of Annealing Treatment on Mechanical Behavior and Microstructure in Nanocrystalline Nickel written by Hsiao-Wei Yang and published by . This book was released on 2009 with total page 90 pages. Available in PDF, EPUB and Kindle. Book excerpt: Nanocrystalline (nc) materials are characterized by a grain size in the range 1-200 nm. Because of this characteristic, these materials exhibit unique microstructures in which the volume of grain boundaries is significant. Nc-materials offer interesting possibilities related to many structural applications. In order to explore some of these possibilities, an understanding of the origin of mechanical properties such as strength, hardness, and ductility is essential. Mechanical properties in materials are very sensitive to their microstructure. One important process that can be used to manipulate the details microstructure in materials is annealing. In the present dissertation, annealing treatment was utilized to provide insight into the correlation between mechanical properties and microstructure. Primary among the mechanical properties that were selected for investigation are hardness, the elastic modulus, strength and ductility. Experiments on hardness and the modulus of elasticity were conducted at room temperature on samples of electrodeposited (ED) nc-Ni that were annealed at temperatures ranging from 323 K to 693 K. The results showed the presence of three regions: regions I, II, and III. In region I (300 K T 350 K), hardness and the elastic modulus remained essentially constant. In region II (350

Download or read book Fundamental Mechanical behavior Studies of Annealed and Nano particle strengthened Nickel based Alloys Using In situ Neutron experiments written by E-Wen Huang and published by . This book was released on 2009 with total page 239 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation addresses two issues concerning the fundamental mechanical behavior of the nickel-based superalloys: (1) the deformation mechanisms and (2) the nano-precipitate-strengthening effect. The precipitates are known to fortify the mechanical behavior of the metallic alloys. These precipitates can interact with the matrix upon the applied load. While the precipitation strengthening has been facilitated for many purposes, this research puts forward the mechanistic understanding. The dissertation considers the thesis that Deformation Mechanisms and Nano-precipitate Strengthening and their effects on the microstructure are central to the mechanical behavior of nickel-based superalloys. The experimental methods employed in this research are in-situ neutron-diffraction measurements, in-situ thermal characterization, ex-situ small-angle neutron-scattering, and electron microscopy experiments. The microscopic structural information obtained from the diffraction profiles is compared with the electron-microscopy images to be complementary to each other. The microscopic features are connected with the macroscopic states, such as the applied stresses and temperature evolution to bridge the understanding of the bulk property. This dissertation assumes that the macroscopic-material responses are the convolution of two contributions: the linear-elastic contribution and the plasticity-induced intra/inter-granular contribution. Within the context of this analysis, the mechanistic understanding of the deformation of the alloys is presented.

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 Effects of High pressure Torsion on the Structure and Mechanical Properties of a Nanocrystalline Ni Fe Alloy written by Song Ni and published by . This book was released on 2012 with total page 300 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Atomistic Simulation Study of Nickel Solute Segregation and Mechanical Behavior in Nanocrystalline Fcc Bcc and Hcp Binary Alloys written by Ève-Audrey Picard and published by . This book was released on 2021 with total page 136 pages. Available in PDF, EPUB and Kindle. Book excerpt: Nanocrystalline metals and alloys have been proven to possess unprecedentedly higher tensile strength than coarse-grained conventional metals. The extreme grain refinement in nanocrystalline metals, however, negatively affects these materials by reducing their ductility through grain-boundary embrittlement and shear localization mechanisms that are promoted by segregation of solute atoms to the interfaces. Different segregation behaviors described in the literature can be divided into either heterogeneous or homogeneous types. Yet current understanding of the impact of solute atom arrangements within grain boundary networks on mechanical properties of cubic and hexagonal nanocrystals remains limited. In this thesis, hybrid Monte-Carlo and molecular dynamics simulations were used to study the segregation behavior of Ni solute atoms in polycrystals made of FCC Ag-Ni, FCC Al-Ni, BCC Nb-Ni, and HCP Zr-Ni alloys. Solute segregation in 4 binary alloys with a constant solute content of 4 at.% Ni was simulated and quantified at the same homologous temperature and at their respective maximum solubility temperature. A spectrum of segregation configurations varying from fully heterogeneous to fully homogeneous was found: Pure heterogeneous segregation (Ag96Ni4 500 K), homogeneous segregation with second-phase precipitates (Al96Ni4 378 K, Nb96Ni4 1110 K), homogeneous segregation with small-scale Ni clusters (Nb96Ni4 1564 K, Zr96Ni4 464 K), and pure homogeneous segregation with amorphous intergranular films (Al96Ni4 913 K, Zr96Ni4 1118 K). These differences in segregation behavior are shown to lead to significant variations in stress-strain response for each alloy. It is found that segregation involving the presence of grain-boundary precipitates with homogeneous segregation behavior promoted the most significant shear localization.

Download or read book The Mechanical Properties and Oxidation Behavior of Nanocrystalline NiAl Synthesized Via Shock Consolidation of Mechanically Alloyed Powders of Ni and Al written by Tao Chen and published by . This book was released on 1999 with total page 304 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Nanostructure Stabilization and Mechanical Behavior of Binary Nanocrystalline Alloys written by Jason R. Trelewicz and published by . This book was released on 2008 with total page 290 pages. Available in PDF, EPUB and Kindle. Book excerpt: The unique mechanical behavior of nanocrystalline metals has become of great interest in recent years, owing to both their remarkable strength and the emergence of new deformation physics at the nanoscale. Of particular interest has been the breakdown in Hall-Petch strength scaling, which is frequently attributed by atomistic simulations to a mechanistic shift to interface dominated plasticity. Experimental validation has been less abundant, primarily due to the processing challenges associated with achieving homogeneous nanocrystalline samples suitable for mechanical testing. Alloying has been proposed as a potential route to high-quality nanocrystalline metals, although choice of an appropriate alloy system, based on available thermodynamic data, remains elusive. In this thesis, we propose a thermodynamic model for nanostructure stabilization that derives from the energetic state variables characteristic of binary alloys. These modeling results motivate the study of Ni-W alloys in particular, which may be synthesized via aqueous electrodeposition, accessing grain sizes across the entire Hall-Petch breakdown regime as characterized by x-ray diffraction and transmission electron microscopy. Ambient temperature nanoindentation testing is employed to evaluate the mechanical behavior of the as-deposited alloys, assessing the nature of flow, the rate sensitivity, and pressure sensitivity of deformation, with emphasis on property inflections required to bridge the behavior of nanocrystalline metals to amorphous solids. The rate sensitivity, in particular, demonstrates an inherent dependence on nanocrystalline grain size, exhibiting a maximum in the vicinity of the Hall-Petch breakdown as a consequence of a shift to glass-like shear localization. In light of this finding, we study the Hall-Petch breakdown at high strain rates, and show that an "inverse Hall-Petch" weakening regime emerges at high rates. Additional effects from structural relaxation are investigated, and illustrated to strongly influence the strength scaling behavior and shift to inhomogeneous flow. Relaxed samples are also subjected to elevated temperature indentation tests, and the results discussed in the context of thermally-activated plasticity, thus providing a more quantitative analysis of the nanoscale deformation mechanisms.

Download or read book Uhlig s Corrosion Handbook written by R. Winston Revie and published by John Wiley & Sons. This book was released on 2011-04-12 with total page 1299 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book serves as a reference for engineers, scientists, and students concerned with the use of materials in applications where reliability and resistance to corrosion are important. It updates the coverage of its predecessor, including coverage of: corrosion rates of steel in major river systems and atmospheric corrosion rates, the corrosion behavior of materials such as weathering steels and newer stainless alloys, and the corrosion behavior and engineering approaches to corrosion control for nonmetallic materials. New chapters include: high-temperature oxidation of metals and alloys, nanomaterials, and dental materials, anodic protection. Also featured are chapters dealing with standards for corrosion testing, microbiological corrosion, and electrochemical noise.

Download or read book Properties and Applications of Nanocrystalline Alloys from Amorphous Precursors written by Bogdan Idzikowski and published by Springer Science & Business Media. This book was released on 2005-07-18 with total page 453 pages. Available in PDF, EPUB and Kindle. Book excerpt: Metallic (magnetic and non-magnetic) nanocrystalline materials have been known for over ten years but only recent developments in the research into those complex alloys and their metastable amorphous precursors have created a need to summarize the most important accomplishments in the field. This book is a collection of articles on various aspects of metallic nanocrystalline materials, and an attempt to address this above need. The main focus of the papers is put on the new issues that emerge in the studies of nanocrystalline materials, and, in particular, on (i) new compositions of the alloys, (ii) properties of conventional nanocrystalline materials, (iii) modeling and simulations, (iv) preparation methods, (v) experimental techniques of measurements, and (vi) different modern applications. Interesting phenomena of the physics of nanocrystalline materials are a consequence of the effects induced by the nanocrystalline structure. They include interface physics, the influence of the grain boundaries, the averaging of magnetic anisotropy by exchange interactions, the decrease in exchange length, and the existence of a minimum two-phase structure at the atomic scale. Attention is also paid to the special character of the local atomic ordering and to the corresponding interatomic bonding as well as to anomalies and particularities of electron density distributions, and to the formation of metastable, nanocrystalline (or quasi-crystalline) phases built from exceptionally small grains with special properties. Another important focus of attention are new classes of materials which are not based on new compositions, but rather on the original and special crystalline structure in the nanoscale.

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 Properties and Applications of Nanocrystalline Alloys from Amorphous Precursors written by Peter Švec and published by Springer Science & Business Media. This book was released on with total page 478 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Proceedings of the 8th International Symposium on Superalloy 718 and Derivatives written by The Minerals, Metals & Materials Society (TMS) and published by John Wiley & Sons. This book was released on 2014-12-02 with total page 958 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1995 with total page 702 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Tensile Properties of Nanocrystalline Nickel iron Alloys written by Hung-Hsun Wei and published by . This book was released on 2006 with total page 386 pages. Available in PDF, EPUB and Kindle. Book excerpt: The objective of this work was to develop a better understanding of the mechanical properties of fully dense bulk nanocrystalline Ni-Fe alloys. Nanocrystalline Ni-Fe alloys (grain size

Download or read book Microstructure and Mechanical Properties of Nanocrystalline Ni Produced by Three Different Synthesis Techniques written by Florian Dalla Torre and published by . This book was released on 2003 with total page 242 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Nanocrystalline Alloys written by Timothy John Rupert and published by . This book was released on 2011 with total page 132 pages. Available in PDF, EPUB and Kindle. Book excerpt: Nanocrystalline materials have experienced a great deal of attention in recent years, largely due to their impressive array of physical properties. In particular, nanocrystalline mechanical behavior has been of interest, as incredible strengths are predicted when grain size is reduced to the nanometer range. The vast majority of research to this point has focused on quantifying and understanding the grain size-dependence of strength, leading to the discovery of novel, grain boundary-dominated physics that begin to control deformation at extremely fine grain sizes. With the emergence of this detailed understanding of nanocrystalline deformation mechanisms, the opportunity now exists for studies that explore how other structural features affect mechanical properties in order to identify alternative strengthening mechanisms. In this thesis, we seek to extend our current knowledge of nanocrystalline structure-property relationships beyond just grain size, using combinations of structural characterization, mechanical testing, and atomistic simulations. Controlled experiments on Ni-W are first used to show that solid solution addition and the relaxation of nonequilibrium grain boundary state can dramatically affect the strength of nanocrystalline metals. Next, the sliding wear response of nanocrystalline Ni-W is investigated, to show how alloying and grain boundary structural state affect a more complex mechanical property. This type of mechanical loading also provides a strong driving force for structural evolution, which, in this case, is found to be beneficial. Mechanically-driven grain growth and grain boundary relaxation occur near the surface of the Ni-W samples during sliding, leading to a hardening effect that improves wear resistance and results in a deviation from Archard scaling. Finally, molecular dynamics simulations are performed to confirm that mechanical cycling alone can indeed relax grain boundary structure and strengthen nanocrystalline materials. In all of the cases discuss above, our observations can be directly connected to the unique deformation physics of nanocrystalline materials.