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1
Suzuki, Asuka, Yusuke Sasa, Makoto Kobashi, Masaki Kato, Masahito Segawa, Yusuke Shimono e Sukeharu Nomoto. "Persistent Homology Analysis of the Microstructure of Laser-Powder-Bed-Fused Al–12Si Alloy". Materials 16, n. 22 (18 novembre 2023): 7228. http://dx.doi.org/10.3390/ma16227228.
Testo completoAbstract (sommario):
The laser powder bed fusion (L-PBF) process provides the cellular microstructure (primary α phase surrounded by a eutectic Si network) inside hypo-eutectic Al–Si alloys. The microstructure changes to the particle-dispersed microstructure with heat treatments at around 500 °C. The microstructural change leads to a significant reduction in the tensile strength. However, the microstructural descriptors representing the cellular and particle-dispersed microstructures have not been established, resulting in difficulty in terms of discussion regarding the structure–property relationship. In this study, an attempt was made to analyze the microstructure in L-PBF-built and subsequently heat-treated Al–12Si (mass%) alloys using the persistent homology, which can analyze the spatial distributions and connections of secondary phases. The zero-dimensional persistent homology revealed that the spacing between adjacent Si particles was independent of Si particle size in the as-built alloy, whereas fewer Si particles existed near large Si particles in the heat-treated alloy. Furthermore, the first principal component of a one-dimensional persistent homology diagram would represent the microstructural characteristics from cellular to particle-dispersed morphology. These microstructural descriptors were strongly correlated with the tensile and yield strengths. This study provides a new insight into the microstructural indices describing unique microstructures in L-PBF-built alloys.
2
Zeng, Qiu Lian, Zhong Guang Wang e J. K. Shang. "Microstructural Effects on Low Cycle Fatigue of Sn-3.8Ag-0.7Cu Pb-Free Solder". Key Engineering Materials 345-346 (agosto 2007): 239–42. http://dx.doi.org/10.4028/www.scientific.net/kem.345-346.239.
Testo completoAbstract (sommario):
Low cycle fatigue behavior of Sn-3.8Ag-0.7Cu solder was investigated under fully reversed cyclic loading, with particular emphasis on microstructural effects. The LCF behavior of the solder with equiaxed microstructure was found to differ greatly from that of the solder with a dendrite microstructure. At a given total strain amplitude, the dendrite microstructure exhibited a much longer fatigue life than the equiaxed microstructure. Such a strong microstructural effect on fatigue life arose from the difference in cyclic deformation and fracture mechanisms between the two microstructures. A large number of microcracks along grain boundaries of the equiaxed structure solder developed with increasing cycling, while for the dendrite structure solder, cyclic deformation took place along the direction of the maximal shear stress during fatigue tests and microcracks initiated and propagated along shear deformation bands. Besides, the fatigue behavior of the dendritic microstructure was very sensitive to cyclic frequency whereas the fatigue behavior of the equiaxed microstructure showed less sensitivity to cyclic frequency.
3
Trzciński, Jerzy, e Emilia Wójcik. "Application of microstructure classification for the assessment of the variability of geological-engineering and pore space properties in clay soils". Open Geosciences 11, n. 1 (12 giugno 2019): 236–48. http://dx.doi.org/10.1515/geo-2019-0019.
Testo completoAbstract (sommario):
Abstract The performed investigations were focused on analysing the variability of geological-engineering properties in clay soils from central-eastern Europe with regard to microstructures. Thirty-nine soils differing in origin, lithology and microstructure type were selected for analysis. Results of studies on lithological and physical and mechanical parameters were analysed, coupled with quantitative microstructural parameters based on microstructure images. The relationships between lithological, physical and mechanical and pore space parameters were determined with regard to microstructure types. Sediment origin and diagenesis, and soil microstructure and pore space parameters had influence on the geological-engineering properties. Such approach allows for predicting engineering parameters based on soil microstructure types and their pore space parameters.
4
Dolzhenko, Anastasiia, Marina Tikhonova, Rustam Kaibyshev e Andrey Belyakov. "Microstructures and Mechanical Properties of Steels and Alloys Subjected to Large-Strain Cold-to-Warm Deformation". Metals 12, n. 3 (8 marzo 2022): 454. http://dx.doi.org/10.3390/met12030454.
Testo completoAbstract (sommario):
The effect of large-strain cold-to-warm deformation on the microstructures and mechanical properties of various steels and alloys is critically reviewed. The review is mainly focused on the microstructure evolution, whereas the deformation textures are cursorily considered without detailed examination. The deformation microstructures are considered in a wide strain range, from early straining to severe deformations. Such an approach offers a clearer view of how the deformation mechanisms affect the structural changes leading to the final microstructures evolved in large strains. The general regularities of microstructure evolution are shown for different deformation methods, including conventional rolling/swaging and special techniques, such as equal channel angular pressing or torsion under high pressure. The microstructural changes during deformations under different processing conditions are considered as functions of total strain. Then, some important mutual relationships between the microstructural parameters, e.g., grain size vs. dislocation density, are revealed and discussed. Particular attention is paid to the mechanisms of microstructure evolution that are responsible for the grain refinement. The development of an ultrafine-grained microstructure during large strain deformation is considered in terms of continuous dynamic recrystallization. The regularities of the latter are discussed in comparison with conventional (discontinuous) dynamic recrystallization and grain subdivision (fragmentation) phenomenon. The structure–property relations are quantitatively represented for the structural strengthening, taking into account various mechanisms of dislocation retardation.
5
Tian, Yan, Mingchun Zhao, Wenjian Liu, Jimou Zhang, Min Zhang, Hongying Li, Dengfeng Yin e Andrej Atrens. "Comparison on Tensile Characteristics of Plain C–Mn Steel with Ultrafine Grained Ferrite/Cementite Microstructure and Coarse Grained Ferrite/Pearlite Microstructure". Materials 14, n. 9 (29 aprile 2021): 2309. http://dx.doi.org/10.3390/ma14092309.
Testo completoAbstract (sommario):
This work investigated the tensile characteristics of plain C–Mn steel with an ultrafine grained ferrite/cementite (UGF/C) microstructure and coarse-grained ferrite/pearlite (CGF/P) microstructure. The tensile tests were performed at temperatures between 77 K and 323 K. The lower yield and the ultimate tensile strengths were significantly increased when the microstructure was changed from the CGF/P to the UGF/C microstructures, but the total elongation and the uniform elongation decreased. A microstructural change from the CGF/P microstructure to the UGF/C microstructure had an influence on the athermal component of the lower yield and the ultimate tensile strengths but not on the thermal component. The UGF/C microstructure with a higher carbon content provided a higher strength without losing ductility because cementite particles restrained necking.
6
Hua, Tian, Ziyin Xiang, Xiangling Xia, Zhangling Li, Dandan Sun, Yuanzhao Wu, Yiwei Liu, Jie Shang, Jun Chen e Runwei Li. "A Sensitivity-Optimized Flexible Capacitive Pressure Sensor with Cylindrical Ladder Microstructural Dielectric Layers". Sensors 23, n. 9 (27 aprile 2023): 4323. http://dx.doi.org/10.3390/s23094323.
Testo completoAbstract (sommario):
Flexible capacitive pressure sensors have attracted extensive attention due to their dynamic response and good sensing capability for static and small pressures. Using microstructural dielectric layers is an effective method for improving performance. However, the current state of microstructure design is primarily focused on basic shapes and is largely limited by simulation results; there is still a great deal of potential for further innovation and improvement. This paper innovatively proposes to increase the ladder structure based on the basic microstructures, for example, the long micro-ridge ladder, the cuboid ladder, and cylindrical ladder microstructures. By comparing 9 kinds of microstructures including ladder structure through finite element simulation, it is found that the sensor with a cylindrical ladder microstructure dielectric layer has the highest sensitivity. The dielectric layers with various microstructures are obtained by 3D printed molds, and the sensor with cylindrical ladder microstructure dielectric layer has the sensitivity of 0.12 kPa−1, which is about 3.9 times higher than that without microstructure. The flexible pressure sensor developed by us boasts sensitivity-optimized and operational stability, making it an ideal solution for monitoring rainfall frequency in real time.
7
Morri, A., L. Ceschini, M. Pellizzari, C. Menapace, F. Vettore e E. Veneri. "Effect of the Austempering Process on the Microstructure and Mechanical Properties of 27MnCrB5-2 Steel". Archives of Metallurgy and Materials 62, n. 2 (1 giugno 2017): 643–51. http://dx.doi.org/10.1515/amm-2017-0094.
Testo completoAbstract (sommario):
AbstractThe effect of austempering parameters on the microstructure and mechanical properties of 27MnCrB5-2 steel has been investigated by means of: dilatometric, microstructural and fractographic analyses; tensile and Charpy V-notch (CVN) impact tests at room temperature and a low temperature.Microstructural analyses showed that upper bainite developed at a higher austempering temperature, while a mixed bainitic-martensitic microstructure formed at lower temperatures, with a different amount of bainite and martensite and a different size of bainite sheaf depending on the temperature. Tensile tests highlighted superior yield and tensile strengths (≈30%) for the mixed microstructure, with respect to both fully bainitic and Q&T microstructures, with only a low reduction in elongation to failure (≈10%). Impact tests confirmed that mixed microstructures have higher impact properties, at both room temperature and a low temperature.
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Müller, Martin, Marie Stiefel, Björn-Ivo Bachmann, Dominik Britz e Frank Mücklich. "Overview: Machine Learning for Segmentation and Classification of Complex Steel Microstructures". Metals 14, n. 5 (7 maggio 2024): 553. http://dx.doi.org/10.3390/met14050553.
Testo completoAbstract (sommario):
The foundation of materials science and engineering is the establishment of process–microstructure–property links, which in turn form the basis for materials and process development and optimization. At the heart of this is the characterization and quantification of the material’s microstructure. To date, microstructure quantification has traditionally involved a human deciding what to measure and included labor-intensive manual evaluation. Recent advancements in artificial intelligence (AI) and machine learning (ML) offer exciting new approaches to microstructural quantification, especially classification and semantic segmentation. This promises many benefits, most notably objective, reproducible, and automated analysis, but also quantification of complex microstructures that has not been possible with prior approaches. This review provides an overview of ML applications for microstructure analysis, using complex steel microstructures as examples. Special emphasis is placed on the quantity, quality, and variance of training data, as well as where the ground truth needed for ML comes from, which is usually not sufficiently discussed in the literature. In this context, correlative microscopy plays a key role, as it enables a comprehensive and scale-bridging characterization of complex microstructures, which is necessary to provide an objective and well-founded ground truth and ultimately to implement ML-based approaches.
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Abdalla, Ayad Omran, Astuty Amrin, Roslina Mohammad e M. A. Azmah Hanim. "Microstructural Study of Newly Designed Ti-6Al-1Fe Alloy through Deformation". Solid State Phenomena 264 (settembre 2017): 54–57. http://dx.doi.org/10.4028/www.scientific.net/ssp.264.54.
Testo completoAbstract (sommario):
Recently, iron (Fe) is introduced to substitute vanadium (V) in Ti-alloy. Therefore, new (α+β) titanium alloy, Ti-6Al-1Fe was designed through a complete replacement of V by Fe with major composition modifications of Ti-6Al-4V. This new alloy is believed could provide similar properties of Ti-6Al-4V through modification of its microstructures. Different heat treatments can lead to a diversity of microstructural permutations and combinations. Thus, it is very crucial to study in-depth understanding about the microstructure of Ti-6Al-1Fe. Results reveal that the microstructure of as-received alloy is a typical fine lamellar microstructure. The bi-modal microstructure can be obtained by hot rolling below beta-transus temperature (Tβ) followed by recrystallization treatment at 925°C. While cold rolling followed by recrystallization treatment at 925°C produce equiaxed microstructure.
10
Gallardo-Basile, Francisco-José, Yannick Naunheim, Franz Roters e Martin Diehl. "Lath Martensite Microstructure Modeling: A High-Resolution Crystal Plasticity Simulation Study". Materials 14, n. 3 (2 febbraio 2021): 691. http://dx.doi.org/10.3390/ma14030691.
Testo completoAbstract (sommario):
Lath martensite is a complex hierarchical compound structure that forms during rapid cooling of carbon steels from the austenitic phase. At the smallest, i.e., ‘single crystal’ scale, individual, elongated domains, form the elemental microstructural building blocks: the name-giving laths. Several laths of nearly identical crystallographic orientation are grouped together to blocks, in which–depending on the exact material characteristics–clearly distinguishable subblocks might be observed. Several blocks with the same habit plane together form a packet of which typically three to four together finally make up the former parent austenitic grain. Here, a fully parametrized approach is presented which converts an austenitic polycrystal representation into martensitic microstructures incorporating all these details. Two-dimensional (2D) and three-dimensional (3D) Representative Volume Elements (RVEs) are generated based on prior austenite microstructure reconstructed from a 2D experimental martensitic microstructure. The RVEs are used for high-resolution crystal plasticity simulations with a fast spectral method-based solver and a phenomenological constitutive description. The comparison of the results obtained from the 2D experimental microstructure and the 2D RVEs reveals a high quantitative agreement. The stress and strain distributions and their characteristics change significantly if 3D microstructures are used. Further simulations are conducted to systematically investigate the influence of microstructural parameters, such as lath aspect ratio, lath volume, subblock thickness, orientation scatter, and prior austenitic grain shape on the global and local mechanical behavior. These microstructural features happen to change the local mechanical behavior, whereas the average stress–strain response is not significantly altered. Correlations between the microstructure and the plastic behavior are established.
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Lannutti, J. J. "Characterization and Control of Compact Microstructure". MRS Bulletin 22, n. 12 (dicembre 1997): 38–44. http://dx.doi.org/10.1557/s0883769400034734.
Testo completoAbstract (sommario):
The microstructure and properties of a ceramic component are largely predetermined by the processes and process controls used to manufacture them. The metric for success in manufacturing is often based on gross density. For example, optimizing pressure-density response, maximizing overall density, and minimizing springback and delaminations in powder pressing all focus on characterization and control of the overall (macroscopic) state of a powder compact. Unfortunately this focus on macroscopic effects has contributed to a general neglect of the compact at the microstructural level. Process-control variables in powder compaction have been defined and discussed by many workers, but their quantitative application to predict and control compaction behavior is limited. Advances in characterization technology and computer modeling now allow us to quantitatively characterize and simulate microstructures more easily. These and other tools can help provide the scientific and technological foundation necessary to predict and control microstructure and microstructural evolution during processing.
12
Weng, Yung-Jin, Jen-Ching Huang, Yueh-Yang Chen, Shao-Teng Hsu e Zu-Rong Zhang. "A Study on the Dynamic Forming Mechanism Development of the Negative Poisson’s Ratio Elastomer Molds—Plate to Plate (P2P) Forming Process". Polymers 13, n. 19 (24 settembre 2021): 3255. http://dx.doi.org/10.3390/polym13193255.
Testo completoAbstract (sommario):
This study proposed a dynamic forming mechanism development of the negative Poisson’s ratio elastomer molds—plate to plate (P2P) forming process. To dynamically stretch molds and control the microstructural shape, the proposal is committed to using the NPR structure as a regulatory mechanism. The NPR structural and dynamic parallel NPR-molds to control microstructure mold-cores were simulated and analyzed. ANSYS and MATLAB were used to simulate and predict dynamic NPR embossing replication. The hot-embossing and UV-curing dynamic NPR P2P-forming systems are designed and developed for verification. The results illustrated that the dynamic forming mechanism of the negative Poisson’s ratio elastomer molds proposed by this study can effectively control microstructure molds. This can effectively predict and calculate the geometrical characteristics of the microstructures after embossing. The multi-directional dynamic NPR microstructural replication process can accurately transfer microstructures and provide high transfer rate-replication characteristics.
13
Ito, Tsutomu, e Takashi Mizuguchi. "Superplastic Elongation through Deformation Mechanism Transition during High-Temperature Deformation in Thermally Unstable Fine-Grained Aluminum Solid Solution Alloy". Key Engineering Materials 723 (dicembre 2016): 21–26. http://dx.doi.org/10.4028/www.scientific.net/kem.723.21.
Testo completoAbstract (sommario):
In this study, the superplastic behavior on a fine-grained aluminum solid solution alloy consisting of thermally unstable microstructures was investigated. In order to obtain the fine-grained microstructure, friction stir processing (FSP) was applied to a commercial 5083 aluminum alloy. An equiaxial fine-grained microstructure of 7.8 mm was obtained after FSP, but this microstructure was thermally unstable at high temperatures. Commonly, for fine-grained superplasticity to occur (or to continue grain boundary sliding (GBS)), it is necessary to keep the fine-grained microstructure to less than 10 mm during the high-temperature deformation. However, in this study, a large elongation of over 200% was observed at high temperatures in spite of the occurrence of grain growth. From the microstructural observations, it was determined that the fine-grained microstructure was maintained until the early stage of deformation, but the transgranular deformation was observed at a strain of over 100%. The microstructural feature of the abovementioned transgranular deformation is similar to the deformation microstructure of the solute drag creep occurring in "Class I"-type solid solution alloys. This indicates that the deformation mechanism transition from GBS to the solute drag creep occurred during high-temperature deformation. Here, the possibility of occurrence of the superplastic elongation through deformation mechanism transition is discussed as a model of the thermally unstable aluminum solid solution alloy.
14
Nolan, T. P., R. Sinclair, T. Yamashita e R. Ranjan. "Correlation of micro-structural, micro-chemical and micro-magnetic properties of longitudinal recording media using CM20FEG Lorentz TEM". Proceedings, annual meeting, Electron Microscopy Society of America 52 (1994): 892–93. http://dx.doi.org/10.1017/s042482010017219x.
Testo completoAbstract (sommario):
Cobalt alloy on chromium thin film magnetic media are used in industry computer hard disk drives because of their large values of coercivity (Hc), remanent magnetization (Mr), squareness (S*), and relatively low noise. The magnetic performance depends strongly on processing conditions and the resulting nanometer scale microstructure.A complete structure-processing-properties analysis requires effective measurement of magnetic and microstructural properties. To date, most structure-properties analyses have involved correlation of bulk magnetic (hysteresis loop) properties and magnetic recording measurements with physical microstructures observed by high-resolution SEM and TEM.The nanoscale microstructural features that dramatically affect magnetic properties are difficult to observe but careful TEM analysis has been used to observe subtle, important differences in the atomic scale physical microstructure. Even these impressive capabilities are becoming insufficient for continued development of improved magnetic recording media. Microstructural design is moving into a regime where appropriate control of magnetic properties requires control of elemental composition and second phase formation as well as crystallography and morphology, at near-atomic levels.
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Han, Yuexing, Chuanbin Lai, Bing Wang, Tianyi Hu, Dongli Hu e Hui Gu. "SEGMENTATION AND ANALYSIS METHOD FOR TWO-PHASE CERAMIC (HfB2-B4C) BASED ON THE DETECTION OF VIRTUAL BOUNDARIES". Image Analysis & Stereology 38, n. 1 (11 aprile 2019): 95. http://dx.doi.org/10.5566/ias.1992.
Testo completoAbstract (sommario):
Microstructure of a material stores the genesis of the material and shows various properties of the material. To efficiently analyse the microstructure of a material, the segmentation of different phases or constituents is an important step. However, in general, due to the microstructure’s complexity, most of segmentation is manually done by human experts. It is challenging to automatically segment the material phases and the microstructure. In this work, we propose a method which combines the the dilation operator, GLCM (gray-level co-occurrence matrix), Hough transform and DBSCAN (density-based spatial clustering of applications with noise) for phases segmentation in the examples of certain material of eutectic HfB2-B4C ceramics. In the segmented regions, the further analysis for the microstructural elements is done with DBSCAN. The experimental results show that the proposed method achieves 95.75% segmentation accuracy for segmenting phases and 86.64% correct classification rate for the microstructure in the segmented phases. These experimental results show that our method is effective for the difficult task of the both segmentation and classification of the microstructural characteristics.
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Ding, Qingqing, Hongbin Bei, Xinbao Zhao, Yanfei Gao e Ze Zhang. "Processing, Microstructures and Mechanical Properties of a Ni-Based Single Crystal Superalloy". Crystals 10, n. 7 (3 luglio 2020): 572. http://dx.doi.org/10.3390/cryst10070572.
Testo completoAbstract (sommario):
A second-generation Ni-based superalloy has been directionally solidified by using a Bridgman method, and the key processing steps have been investigated with a focus on their effects on microstructure evolution and mechanical properties. The as-grown microstructure is of a typical dendrite structure with microscopic elemental segregation during solidification. Based on the microstructural evidence and the measured phase transformation temperatures, a step-wise solution treatment procedure is designed to effectively eliminate the compositional and microstructural inhomogeneities. Consequently, the homogenized microstructure consisting of γ/γ′ phases (size of γ′ cube is ~400 nm) have been successfully produced after a two-step (solid solution and aging) treatment. The mechanical properties of the resulting alloys with desirable microstructures at room and elevated temperatures are measured by tensile tests. The strength of the alloy is comparable to commercial monocrystalline superalloys, such as DD6 and CMSX-4. The fracture modes of the alloy at various temperatures have also been studied and the corresponding deformation mechanisms are discussed.
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Sachana, Suphattra, Kohei Morishita e Hirofumi Miyahara. "Microstructural Examination of Molten Marks on Copper Wire for Fire Investigation". Forensic Sciences 3, n. 1 (6 gennaio 2023): 12–19. http://dx.doi.org/10.3390/forensicsci3010002.
Testo completoAbstract (sommario):
Fire investigators have attempted to study fire behaviors through microstructural examination of molten marks on copper wire. However, there have not been many studies on the metallurgical examination of real-world cases. This research examined the surface morphology and microstructure in the longitudinal section of molten marks on copper wire from various fire scenes to explain how they formed and identify the surrounding materials. The results show that the foreign elements discovered via EDS on the surface of molten marks vary depending on their environment. Molten mark microstructures differed even if they were collected from the same fire scene; a distinct microstructure implies different molten mark formations. Moreover, the presence of residual elements in the microstructure indicates the existence of surrounding materials during formation in a fire. Therefore, microstructural diversity and the presence of residual elements may guide fire investigators in explaining the formation of molten marks and the fire environment for fire investigation.
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Murr, L. E. "Microstructure-property hypermaps for shock-loaded materials". Proceedings, annual meeting, Electron Microscopy Society of America 44 (agosto 1986): 416–19. http://dx.doi.org/10.1017/s0424820100143675.
Testo completoAbstract (sommario):
Residual deformation-induced metallurgical effects or structure (microstructure)-property relationships are now generally well documented to be the result of stress or strain-induced microstructures, or microstructural changes in polycrystalline metals and alloys. In many cases, strain hardening, work hardening, or other controlling deformation mechanisms can be described by the generation, movement, and interactions of dislocations and other crystal defects which produce drag, or a range of impedances, including obstacles to dislocation motion.
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Anisimov, Evgeniy, Jan Manak, Maxim Puchnin e Pavel Sachr. "The Effect of Microstructural Features on Mechanical Properties". Key Engineering Materials 606 (marzo 2014): 47–50. http://dx.doi.org/10.4028/www.scientific.net/kem.606.47.
Testo completoAbstract (sommario):
Every material is structured in its unique way and has its own recognizable microstructure. There are a number of approaches in establishing the relationship between mechanical properties and microstructure of a material, but none of them is universal and correlation free, probably because of luck of attention to the sub-grain structure. The possibility of calculating the hardness number using only geometric sizes of microstructural formations is discussed in this paper, where the grain is meant to be a container of the two most frequently occurred shapes in the microstructures globula and lamellae.
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Dong, Qin, Zhong Wei Yin, Hu Lin Li, Yang Mao e Geng Yuan Gao. "3D Reconstruction of Microstructure for Centrifugal Casting Babbitt Lining of Bimetallic Bearing Based on Mimics". Key Engineering Materials 841 (maggio 2020): 94–98. http://dx.doi.org/10.4028/www.scientific.net/kem.841.94.
Testo completoAbstract (sommario):
Babbitt alloys are the most commonly used bearing materials for low speed diesel engines due to their excellent attributes. An understanding of microstructures in these alloys is important, especially quantifying microstructure in 3D. In this study, we used serial sectioning technique to reconstruct 3D microstructure of tin-based Babbitt lining of bimetallic bearing made by centrifugal casting based on medical software Mimics. The morphologies and volume fraction of hard phase particles and α-Sn matrix were obtained. The volume fraction of the reconstructed microstructures was verified by the area fraction of the metallographic sections, which proved a higher reliability of 3D reconstruction. The results of 3D microstructural characterization and analysis will enable a comprehensive understanding the structure–property relationships of these materials.
21
James, R. D. "Microstructure of Shape-Memory and Magnetostrictive Materials". Applied Mechanics Reviews 43, n. 5S (1 maggio 1990): S189—S193. http://dx.doi.org/10.1115/1.3120802.
Testo completoAbstract (sommario):
Recent advances in the analysis of microstructure is providing models and methods for treating the kinds of optimization problems that arise in the study of microstructure. The main advance has been the development of theory and methods for treating the case in which arbitrary microstructures compete for the minimum (or maximum). This contrasts for example with micromechanics in which the geometry of the microstructure is assumed, or assumed up to the choice of a few parameters, and then the optimization or stress analysis is carried out under severe geometric restrictions. Micromechanics is effective in dealing with a particular experimentally observed microstructure, but not for understanding microstructures that might be optimal in a certain sense. Much of this recent research has been fueled by critical discussions among engineering scientists, mathematicians and electron microscopists. The intent of this paper is first to summarize, in terms accessible to a broad audience, the nature of this research and then to describe applications to the improvement of shape-memory and magnetostrictive materials. The general part of the lecture will focus on three areas, effective properties of materials, optimal design of materials and phase transformation and active materials. A central role is played by the question “How does one meaningfully average a quantity whose values vary rapidly on a microstructural scale?” A second recurring theme is that the optimal microstructure is predicted to have fine structure. The latter is closely related to the failure of conditions of material stability.
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Mossaab, Blaoui Mohammed, Mokhtar Zemri e Mustapha Arab. "Effect of medium carbon steel microstructure on tensile strength and fatigue crack growth". International Journal of Structural Integrity 10, n. 1 (4 febbraio 2019): 67–75. http://dx.doi.org/10.1108/ijsi-05-2018-0030.
Testo completoAbstract (sommario):
Purpose The purpose of this paper is to evaluate the effects of medium carbon steel microstructure on the tensile strength and fatigue crack growth (FCG) behavior. Design/methodology/approach To achieve this aim, four different heat treatment methods (normalizing, quenching, tempering at 300°C and tempering at 600°C) were considered. Microstructural evolution was investigated by scanning electron microscopy. FCG rate tests were conducted on the resultant microstructures with compact tension specimens at room temperature by a standard testing method. Findings The results show that the normalized microstructure had the largest number of cycles to failure, indicating a high fatigue resistance, followed by the as received, tempered at 600°C, tempered at 300°C and quenched microstructure. Originality/value The paper shows the influence of the microstructure on the fatigue-propagation behavior with the definition of the Paris parameters of each heat treatment condition.
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Basanta, David, Mark A. Miodownik, Elizabeth A. Holm e Peter J. Bentley. "Evolving 3D Microstructures Using a Genetic Algorithm". Materials Science Forum 467-470 (ottobre 2004): 1019–24. http://dx.doi.org/10.4028/www.scientific.net/msf.467-470.1019.
Testo completoAbstract (sommario):
We describe a general approach to obtaining 3D microstructures as input to computer simulations of materials properties. We introduce a program called MicroConstructor, that takes 2D micrographs and generates 3D discrete computer microstructures which are statistically equivalent in terms of the microstructural variables of interest. The basis of the code is a genetic algorithm that evolves the 3D microstructure so that its stereological parameters match the 2D data. Since this approach is not limited by scale it can be used to generate 3D initial multiscale microstructures. This algorithm will enable microstructural modellers to use as their starting point, experimentally based microstructures without having to acquire 3D information experimentally, a very time consuming and expensive process.
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Belan, Juraj, Alan Vaško, Lenka Kuchariková e Eva Tillová. "Metallography Evaluation of Cast and Wrought Ni-Base Superalloys". Materials Science Forum 891 (marzo 2017): 414–19. http://dx.doi.org/10.4028/www.scientific.net/msf.891.414.
Testo completoAbstract (sommario):
. The Ni-base superalloys have an interesting history and evolution since they start to be used in aero jet engines. Microstructures of superalloys have dramatically changed through the years as modern technology of its casting or forging becomes more sophisticated. The first superalloys have polyedric microstructure consist of gamma solid solution, some fraction of gamma prime and of course grain boundaries. As demands on higher performance of aero jet engine increases, the changes in superalloys microstructure become more significant. Further step in microstructure evolution was directionally solidified alloys with columnar gamma prime particles. The latest microstructures are mostly monocrystalline, oriented in [001] direction of FCC gamma matrix. What does not changed through the years is elementary FCC structure of matrix and fundamental group of alloying elements. All microstructure changes bring necessity of proper preparation and evaluation of microstructure. Except already mentioned structures have gamma double prime and various carbides form appear. These structural parameters have mainly positive influence on important mechanical properties of superalloys. However, some detrimental phases as Laves, σ-phase appears as well and have negative influence on heat resistance of superalloys. Paper deals with such microstructural evaluation of both groups of alloys – cast and wrought as well. Microstructure evaluation helps to describe mechanism at various loading and failure of progressive superalloys. Such example where microstructure evaluation is employed is fractography of failure surfaces after fatigue tests, which are as example of metallography evaluation described in this paper as secondary objective. Fatigue test done in this article were at high frequency with push-pull loading, so called high frequency fatigue loading (HFFL) and at low frequency three point flexure, so called low frequency fatigue loading (LFFL).
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Li, Luoyang, Marissa J. Betts, Hao Yun, Bing Pan, Timothy P. Topper, Guoxiang Li, Xingliang Zhang e Christian B. Skovsted. "Fibrous or Prismatic? A Comparison of the Lamello-Fibrillar Nacre in Early Cambrian and Modern Lophotrochozoans". Biology 12, n. 1 (11 gennaio 2023): 113. http://dx.doi.org/10.3390/biology12010113.
Testo completoAbstract (sommario):
The Precambrian–Cambrian interval saw the first appearance of disparate modern metazoan phyla equipped with a wide array of mineralized exo- and endo-skeletons. However, the current knowledge of this remarkable metazoan skeletonization bio-event and its environmental interactions is limited because uncertainties have persisted in determining the mineralogy, microstructure, and hierarchical complexity of these earliest animal skeletons. This study characterizes in detail a previously poorly understood fibrous microstructure—the lamello-fibrillar (LF) nacre—in early Cambrian mollusk and hyolith shells and compares it with shell microstructures in modern counterparts (coleoid cuttlebones and serpulid tubes). This comparative study highlights key differences in the LF nacre amongst different lophotrochozoan groups in terms of mineralogical compositions and architectural organization of crystals. The results demonstrate that the LF nacre is a microstructural motif confined to the Mollusca. This study demonstrates that similar fibrous microstructure in Cambrian mollusks and hyoliths actually represent a primitive type of prismatic microstructure constituted of calcitic prisms. Revision of these fibrous microstructures in Cambrian fossils demonstrates that calcitic shells are prevalent in the so-called aragonite sea of the earliest Cambrian. This has important implications for understanding the relationship between seawater chemistry and skeletal mineralogy at the time when skeletons were first acquired by early lophotrochozoan biomineralizers.
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Kim, Young Ho, Jeong-Woo Sohn, Youngjae Woo, Joo-Hyun Hong, Gyu Man Kim, Bong Keun Kang e Juyoung Park. "Preparation of Microstructure Molds of Montmorillonite/Polyethylene Glycol Diacrylate and Multi-Walled Carbon Nanotube/Polyethylene Glycol Diacrylate Nanocomposites for Miniaturized Device Applications". Journal of Nanoscience and Nanotechnology 15, n. 10 (1 ottobre 2015): 7860–65. http://dx.doi.org/10.1166/jnn.2015.11224.
Testo completoAbstract (sommario):
Environmentally friendly microstructure molds with montmorillonite (MMT) or multi-walled carbon nanotube (MWCNT) reinforced polyethylene glycol diacrylate (PEGDA) nanocomposites have been prepared for miniaturized device applications. The micropatterning of MMT/PEGDA and MWCNT/PEGDA with 0.5 to 2.0 wt% of MMTs and MWCNTs was achieved through a UV curing process with micro-patterned masks. Hexagonal dot arrays and complex patterns for microstructures of the nanocomposites were produced and characterized with an optical microscope; their thermal properties were studied by thermogravimetric analysis (TGA). The TGA results showed that these nanocomposites were thermally stable up to 350 °C. Polydimethylsiloxane thin replicas with different microstructures were prepared by a casting method using the microstructured nanocomposites as molds. It is considered that these microstructure molds of the nanocomposites can be used as microchip molds to fabricate nanobio-chips and medical diagnostic chip devices.
27
Fan, Fang-Yu, Hsin-Hua Chou, Wei-Chun Lin, Chiung-Fang Huang, Yi Lin, Yung-Kang Shen e Muhammad Ruslin. "Optimized Micro-Pattern Design and Fabrication of a Light Guide Plate Using Micro-Injection Molding". Polymers 13, n. 23 (3 dicembre 2021): 4244. http://dx.doi.org/10.3390/polym13234244.
Testo completoAbstract (sommario):
This study examined the uniformity of illuminance field distributions of light guide plates (LGPs). First, the authors designed microstructural patterns on the surface of an LGP. Then, a mold of the LGP with the optimal microstructural design was fabricated by a photolithography method. Micro-injection molding (μIM) was used to manufacture the molded LGPs. μIM technology can simultaneously manufacture large-sized wedge-shaped LGPs and micro-scale microstructures. Finally, illuminance values of the field distributions of the LGPs with various microstructures were obtained through optical field measurements. This study compared the illuminance field distributions of LGPs with various designs and structures, which included LGPs without and those with microstructure on the primary design and the optimal design. The average illuminance of the LGP with microstructures and the optimal design was roughly 196.1 cd/m2. Its average illuminance was 1.3 times that of the LGP without microstructures. This study also discusses illuminance field distributions of LGPs with microstructures that were influenced by various μIM process parameters. The mold temperature was found to be the most important processing parameter affecting the illuminance field distribution of molded LGPs fabricated by μIM. The molded LGP with microstructures and the optimal design had better uniformity than that with microstructures and the primary design and that without microstructures. The uniformity of the LGP with microstructures and the optimal design was roughly 86.4%. Its uniformity was nearly 1.65 times that of the LGP without microstructures. The optimized design and fabrication of LGPs with microstructure exhibited good uniformity of illuminance field distributions.
28
Kovalčíková, Alexandra, Ján Balko e Ján Dusza. "Influence of Microstructure on Tribological Properties and Nanohardness of Silicon Carbide Ceramics". Key Engineering Materials 662 (settembre 2015): 55–58. http://dx.doi.org/10.4028/www.scientific.net/kem.662.55.
Testo completoAbstract (sommario):
The influence of microstructural variations on the tribological properties and nanohardness of liquid phase sintered silicon carbide (LPS SiC) has been observed. In order to modify the microstructures samples were further heat treated at 1650°C and 1850°C for 5 hours to promote grain growth. The depth-sensing indentation tests of SiC materials were performed at several peak loads in the range 10-400 mN. The pin-on-flat dry sliding friction and wear experiments have been made on SiC ceramics in contact with Al2O3 ceramic ball at 10-50 N loads in an ambient environment. The nanohardness of samples with plate-like microstructure was about 34 GPa i.e. 3 GPa higher than nanohardness of SiC with fine globular microstructure. The SiC materials with coarser plate-like microstructure had similar COF (0.4-0.55) and better wear resistance (one order of magnitude at normal forces 10-20N) than SiC materials with fine globular microstructure.
29
Rodriguez vargas, Bryan ramiro, Luciano Albini, Giulia Tiracorrendo, Riccardo Massi, Giulia Stornelli e Andrea Di Schino. "EFFECT OF ULTRAFAST HEATING ON AISI 304 AUSTENITIC STAINLESS STEEL". Acta Metallurgica Slovaca 29, n. 2 (20 giugno 2023): 104–7. http://dx.doi.org/10.36547/ams.29.2.1833.
Testo completoAbstract (sommario):
This study explores the effects of ultrafast heating on AISI 304 austenitic stainless steel. The research shows that ultrafast heating can lead to fine-grained mixed microstructures in steel, making it a potential alternative for modifying microstructure in stainless steel. The study demonstrates that a minimum temperature of 980 °C is required to achieve a fully recrystallized microstructure. The results also suggest that a lower temperature can result in a finer recrystallized grain size compared to higher temperature results. The study provides valuable insights into the impact of ultrafast heating on the microstructural constituents, recrystallization temperatures, and mechanical properties of investigated steel.
30
YEOM, JONG-TAEK, JEOUNG HAN KIM, JAE-KEUN HONG, NHO-KWANG PARK e CHONG SOO LEE. "INFLUENCE OF INITIAL MICROSTRUCTURE ON HOT WORKABILITY OF Ti-6Al-4V ALLOY". International Journal of Modern Physics B 23, n. 06n07 (20 marzo 2009): 808–13. http://dx.doi.org/10.1142/s0217979209060063.
Testo completoAbstract (sommario):
Hot workability of Ti -6 Al -4 V alloy with different initial microstructures was investigated by considering processing maps and the dynamic material deformation behavior. The emphasis has been focused on the effect of initial microstructure (equiaxed versus bimodal structure). Process maps were generated using the dynamic material model (DMM), unifying the relationships between constitutive deformation behavior, hot workability and microstructures evolution. Also, the flow instability was investigated using the various flow instability criteria and microstructural analysis. To establish the processing maps with different initial microstructures, high temperature compression tests were carried out at various temperatures and strain rates up to a true strain of 0.7. Microstructural changes occurring during the deformation were analyzed in terms of high temperature deformation mechanisms. Finally the useful instability criterion for predicting the forming defects was suggested through the compression test results with different temperatures and strain rates.
31
Meng, Yi, Hui Min Zhou, Jia Lin Gan e Sumio Sugiyama. "Microstructural Evolution of SKD11 Tool Steel during Multi-Stage Thixoforming and Subsequent Heat Treatments". Solid State Phenomena 285 (gennaio 2019): 45–50. http://dx.doi.org/10.4028/www.scientific.net/ssp.285.45.
Testo completoAbstract (sommario):
The application of semisolid forming (SSF) is inhibited significantly by the inhomogeneous distributions of microstructure and mechanical properties in the products manufactured by SSF. Beside of forming parameters including forming temperature, isothermal holding time, and forming speed, post heat treatments of SSF is one of the most important facts affecting the microstructure and mechanical properties of the SSF-manufactured products. In this study, heat treatments including annealing, quenching, and tempering different experimental conditions were conducted on the SKD11 tool steel samples manufactured by multi-stage thixoforming with different forming parameters. The microstructures in different regions of specimen processed by different experimental conditions were investigated by using a field-emission scanning electron microscopy (FE-SEM), an energy-dispersive X-ray spectroscopy (EDS), and X-ray diffractometer (XRD). Base on the results of microstructural analyses, the microstructural evolution of SKD11 tool steel during multi-stage thixoforming and subsequent heat treatments with varies experimental parameters were discussed and summarized. Meanwhile, the relationship between microstructure and mechanical properties of SKD11 tool steel processed by multi-stage thixoforming and subsequent heat treatment was also discussed.
32
Chen, Haisheng, Fang Hao, Shixing Huang, Jing Yang, Shaoqiang Li, Kaixuan Wang, Yuxuan Du, Xianghong Liu e Xiaotong Yu. "The Effects of Microstructure on the Dynamic Mechanical Response and Adiabatic Shearing Behaviors of a Near-α Ti-6Al-3Nb-2Zr-1Mo Alloy". Materials 16, n. 4 (7 febbraio 2023): 1406. http://dx.doi.org/10.3390/ma16041406.
Testo completoAbstract (sommario):
The formation and evolution of adiabatic shear behaviors, as well as the corresponding mechanical properties of a near-Ti-6Al-3Nb-2Zr-1Mo (Ti-6321) alloy during dynamic compression process, were systematically investigated by the split Hopkinson pressure bar (SHPB) compression tests in this paper. Ti-6321 samples containing three types of microstructures, i.e., equiaxed microstructure, duplex microstructure and Widmanstätten microstructure, were prepared to investigate the relationship between microstructures and dynamic mechanical behaviors under different strain rates in a range from 1000 s−1 to 3000 s−1. It was found by the dynamic strain–stress relation that the Ti-6321 alloys containing equiaxed microstructure, duplex microstructure and Widmanstätten microstructure all exhibited a strong strain-hardening effect. The samples containing equiaxed microstructure exhibited a larger flow stress than samples containing duplex microstructure and Widmanstätten microstructure. The adiabatic shearing behaviors in Ti-6321 alloy are significantly influenced by different types of microstructures. The formation of adiabatic shearing bands occurs in equiaxed microstructure when the strain rate is increased to 2000 s−1. The adiabatic shear bands are formed in duplex microstructure when the strain rate reaches 3000 s−1. However, the initiation of adiabatic shear bands is found in Widmanstätten microstructure under the strain rate of 1000 s−1. The Widmanstätten microstructure shows a larger sensitivity to adiabatic shearing than the equiaxed microstructure and duplex microstructure samples.
33
Santos, Dagoberto Brandão, Élida G. Neves e Elena V. Pereloma. "Effect of Processing Route on Mechanical Behavior of C-Mn Multiphase High Strength Cold Rolled Steel". Materials Science Forum 539-543 (marzo 2007): 4375–80. http://dx.doi.org/10.4028/www.scientific.net/msf.539-543.4375.
Testo completoAbstract (sommario):
The multiphase steels have complex microstructures containing polygonal ferrite, martensite, bainite, carbide and a small amount of retained austenite. This microstructure provides these steels with a high mechanical strength and good ductility. Different thermal cycles were simulated in the laboratory in order to create the microstructures with improved mechanical properties. The samples were heated to various annealing temperatures (740, 760 or 780°C), held for 300 s, and then quickly cooled to 600 or 500°C, where they were soaked for another 300 s and then submitted to the accelerated cooling process, with the rates in the range of 12-30°C/s. The microstructure was examined at the end of each processing route. The mechanical behavior evaluation was made by microhardness testing. The microstructural characterization involved optical microscopy (OM), X-ray diffraction (XRD), scanning electron microscopy (SEM) with electron backscattering diffraction (EBSD) and transmission electron microscopy (TEM). The use of multiple regression analysis allowed the establishment of quantitative relationship between the microstructural parameters, cooling rates and mechanical properties of the steel.
34
Nguyen, Thao A., Tadashi Yogi e Steven E. Lambert. "The effect of sputtering pressure on microstructure and recording performance of high-density magnetic recording media". Proceedings, annual meeting, Electron Microscopy Society of America 48, n. 4 (agosto 1990): 770–71. http://dx.doi.org/10.1017/s0424820100176988.
Testo completoAbstract (sommario):
Understanding the magnetic properties of thin films applicable to high density recording requires detailed knowledge of the microstructure and microchemistry of the film. Interactions such as exchange and magnetostatic as well as anisotropies have been shown theoretically to influence the magnetic properties and recording characteristics of the media. These magnetic interactions and anisotropies are very sensitive to microstructure. This study reports the efTcct of sputtering pressure on the microstructurc and magnetic properties of thin CoPtCr films. The relation between the microstructural features and the magnetic interactions will be discussed.The film structure, C/Co77Pt6Cr17/Cr, was sequentially sputtered onto Si and NiP/AlMg substrates precleaned by an rf plasma. The thicknesses were 25/25-60/100 nm respectively. Sputtering pressures ranging from 3 to 24 mtorr were investigated. The magnetic properties of the films (coercive field, Hc, coercive squareness, S*, remanent and saturation moments, Mrand Ms) were determined by vibrating sample magnetometry. The magnetic recording measurements were made with thin film inductive write heads and experimental shielded magnetoresistive read head with a track width of about 10μm. The head-media spacing was 5 μin. Noise voltages for transition densities up to 3000 fc/mm were determined in the usual fashion. The microstructures were studied using the JEOL JEM 2000 FX and 4000 EX transmission electron microscopes.
35
Barboza, Luis, Enrique López, Hugo Guajardo e Armando Salinas. "Effect of Initial Microstructure on the Temperature Dependence of the Flow Stress and Deformation Microstructure under Uniaxial Compression of Ti-407". Metals 14, n. 5 (26 aprile 2024): 505. http://dx.doi.org/10.3390/met14050505.
Testo completoAbstract (sommario):
In this study, the influence of initial microstructure and deformation temperature on the flow stress behavior and microstructural evolution of TIMETAL®407 (Ti-407) alloy are investigated. For this purpose, compression cylinders were β-annealed at 940 °C and then cooled to room temperature using furnace cooling, static air, and water quenching to promote three initial microstructures with different α lath thicknesses. The annealed cylinders were compressed isothermally in the range of 750 °C to 910 °C at a constant crosshead speed of 0.05 mm/s up to an engineering strain of −0.8. The resulting stress–strain curves are discussed in terms of the morphology and distribution of the α and β phases. It was found that flow stress is inversely proportional to deformation temperature for all initial microstructures. At the lowest temperatures, compressive yield strength was higher in water-quenched and air-cooled samples than in furnace-cooled specimens, suggesting that the acicular α-phase morphology obtained by rapid cooling could enhance mechanical strength by hindering dislocation motion. Two high-temperature flow regimes were determined based on the shape of the flow stress curves, indicating microstructural changes occurring during deformation. At higher temperatures, the effect of the initial microstructure is negligible as the primary α phase is transformed to the β phase at around 850 °C irrespective of the initial α-lath thickness.
36
Sfikas, Athanasios K., Spyros Kamnis, Martin C. H. Tse, Katerina A. Christofidou, Sergio Gonzalez, Alexandros E. Karantzalis e Emmanuel Georgatis. "Microstructural Evaluation of Thermal-Sprayed CoCrFeMnNi0.8V High-Entropy Alloy Coatings". Coatings 13, n. 6 (28 maggio 2023): 1004. http://dx.doi.org/10.3390/coatings13061004.
Testo completoAbstract (sommario):
The aim of this work is to improve the understanding of the effect of the cooling rate on the microstructure of high-entropy alloys, with a focus on high-entropy alloy coatings, by using a combined computational and experimental validation approach. CoCrFeMnNi0.8V coatings were deposited on a steel substrate with high velocity oxy-air-fuel spray with the employment of three different deposition temperatures. The microstructures of the coatings were studied and compared with the microstructure of the equivalent bulk high-entropy alloy fabricated by suction casting and powder fabricated by gas atomization. According to the results, the powder and the coatings deposited by low and medium temperatures consisted of a BCC microstructure. On the other hand, the microstructure of the coating deposited by high temperature was more complex, consisting of different phases, including BCC, FCC and oxides. The phase constitution of the bulk high-entropy alloy included an FCC phase and sigma. This variation in the microstructural outcome was assessed in terms of solidification rate, and the results were compared with Thermo-Calc modelling. The microstructure can be tuned by the employment of rapid solidification techniques such as gas atomization, as well as subsequent processing such as high velocity oxy-air-fuel spray with the use of different spray parameters, leading to a variety of microstructural outcomes. This approach is of high interest for the field of high-entropy alloy coatings.
37
Carter, Joseph G., e George R. Clark. "Classification and Phylogenetic Significance of Molluscan Shell Microstructure". Notes for a Short Course: Studies in Geology 13 (1985): 50–71. http://dx.doi.org/10.1017/s0271164800001093.
Testo completoAbstract (sommario):
Like most classifications of molluscan shell microstructure published during the past 25 years (e.g., MacClintock, 1967; Kobayashi, 1964, 1971; Taylor, Kennedy and Hall, 1969, 1973; Grégoire, 1972a), the present one is based largely on Bøggild's (1930) monographic work, redefined from a modern perspective of combined light and scanning electron microscopy. However, this is the first attempt to integrate shell microstructure terminology for mollusks with that employed by students of bryozoan and brachiopod shell microstructure (e.g., Williams, 1968a,b, 1970, 1973; Williams and Wright, 1970; Armstrong 1968, 1969; Sandberg, 1971, 1977; Brunton, 1972; MacKinnon, 1974, 1977; MacKinnon and Williams, 1974; Iwata, 1981, 1982). An integration of nomenclatorial schemes is desirable for purposes of interphylum comparison, and is presently needed because there is considerable overlap and inconsistency in the application of microstructural terminology even within single molluscan classes. The present synthesis of shell microstructure nomenclature is possible primarily because of the extensive data base of invertebrate shell mineralogy, microstructure and especially ultrastructure published in more than 300 references in the past 15 years. To these data, the authors have contributed original information of shell mineralogy and microstructure for scores of Recent and fossil mollusks, brachiopods and bryozoans, with a clear emphasis on bivalved mollusks. Many inadequately described microstructure terms have been reanalyzed during the course of this study, either by examining species cited in the literature, or by using closely related species. Perhaps because they are better studied, but probably for other reasons as well, the diversity of molluscan shell microstructures is considerably greater than that of brachiopods and bryozoans combined (Carter, 1979). Consequently, most of the present nomenclature is based on mollusks, and only three of the major microstructural arrangements described in this guide (crossed bladed, semi-nacreous and semi-foliated) were known first in brachiopods or bryozoans and later recognized in molluscs.
38
Han, Dong, Yongqing Zhao e Weidong Zeng. "Effect of Zr Addition on the Mechanical Properties and Superplasticity of a Forged SP700 Titanium Alloy". Materials 14, n. 4 (14 febbraio 2021): 906. http://dx.doi.org/10.3390/ma14040906.
Testo completoAbstract (sommario):
The present study focuses on the effect of 1% Zr addition on the microstructure, tensile properties and superplasticity of a forged SP700 alloy. The results demonstrated that Zr has a significant effect on inhibiting the microstructural segregation and increasing the volume fraction of β-phase in the forged SP700 alloy. After annealing at 820 °C for 1 h and aging at 500 °C for 6 h, the SP700 alloy with 1% Zr showed a completely globular and fine microstructure. The yield strength, ultimate tensile strength and tensile elongation of the alloy with optimized microstructure were 1185 MPa, 1296 MPa and 10%, respectively. The superplastic deformation was performed at 750 °C with an elongation of 1248%. The improvement of tensile properties and superplasticity of the forged SP700 alloy by Zr addition was mainly attributed to the uniform and fine globular microstructures.
39
Vurobi, Selauco, Thiago Ferreira de Andrade e Osvaldo Mitsuyuki Cintho. "Utilization of Color Metallography in Characterization of a Modified SAE 4118H Steel Submitted to Isothermal Treatments". Materials Science Forum 805 (settembre 2014): 242–47. http://dx.doi.org/10.4028/www.scientific.net/msf.805.242.
Testo completoAbstract (sommario):
A modified SAE 4118H steel was subjected to isothermal treatments between 700 °C and 400 oC every 50 °C range, with the intention of evaluating the decomposition of austenite at constant temperature. It was varied time of stay in the isothermal treatment between 15 and 28800 seconds depending on the treatment temperature. After each isothermal treatment and standard metallographic preparation, the samples were etched with color metallography reagents for revealing the microstructure obtained. At temperatures of 700oC to 550°C the steel showed microstructure composed of ferrite and pearlite. Between 500oC and 400°C bainitic microstructure was quickly formed. The reduction of treatment temperature provided finer microstructures, which increased the hardness of steel. With the use of color metallography reagents, excellent contrast for determining the volume fraction of microstructural constituents formed isothermally was obtained, helping the study of isothermal decomposition of austenite.
40
Tao, Xue Li, Kai Ming Wu e Xiang Liang Wan. "Effect of Nb on Microstructure Evolution of Coarse-Grained Heat-Affected Zone with Large Heat Input Welding". Advanced Materials Research 284-286 (luglio 2011): 1174–79. http://dx.doi.org/10.4028/www.scientific.net/amr.284-286.1174.
Testo completoAbstract (sommario):
The effect of Nb microalloying on microstructure transformation of coarse-grained heat-affected zone of high strength low alloy steels were investigated utilizing different heat input welding simulation. For the low-Nb steel, the microstructures of coarse-grained heat-affected zone mainly consisted of acicular ferrite, bainite and grain boundary ferrite for small heat input welding; the amount of acicular ferrite decreased whereas grain boundary ferrite, polygonal ferrite and pearlite increased with increasing heat input. In constrast, for the high-Nb steel, granular bainite was the dominant microstructure. The formation of granular bainitic microstructure was associated with the solid solution of Nb, which suppressed ferrite transformation and promoted the formation of granular bainite. The hardness of coarse-grained heat-affected zone increased with increasing Nb content, and decreased with decreasing heat input, which was attributed to the microstructural change.
41
Mohideen, S. Rasool, Ahmad Zaidi Ahmad Mujahid, Abdullah Shohaimi e S. Ravi. "Metallographic Investigation on the Effect of Cryogenic Temperature on Steel Weldments". Applied Mechanics and Materials 629 (ottobre 2014): 456–60. http://dx.doi.org/10.4028/www.scientific.net/amm.629.456.
Testo completoAbstract (sommario):
Materials are subjected to low temperatures either intentionally as in the case of cryogenic fuels or non-intentionally as in the case of aerospace environment and are observed to undergo changes in their properties. Microstructural changes are the premier indications of changes in the properties of materials. This paper investigates the effect of cryogenic temperature on the microstructure of low alloy steel weldments. The weldments were subjected to liquid nitrogen temperature of 77K and the microstructures were analyzed using optical microscope and transmission electron Microscope. A distinct change in the microstructure was observed which would reason out the changes in the mechanical properties of weldments.
42
Agboola, Joseph, Emmanuel Anyoku e Atinuke Oladoye. "Effects of Cooling Rate on the Microstructure, Mechanical Properties and Corrosion Resistance of 6xxx Aluminium Alloy". International Journal of Engineering Materials and Manufacture 6, n. 1 (30 gennaio 2021): 43–49. http://dx.doi.org/10.26776/ijemm.06.01.2021.04.
Testo completoAbstract (sommario):
The applicability of materials is highly dependent on its microstructure and mechanical properties. Aluminium alloy is being used extensively under diverse conditions. This study investigates the effects of cooling rate on the microstructure, mechanical properties and corrosion resistance of 6xxx-series aluminium alloy. Aluminium ingot was melted in a muffle furnace and cast into rods. The cooling rate was controlled by holding the moulds at different temperatures. Microstructural characteristics were examined by optical microscopy. Mechanical properties such as impact strength, hardness, and tensile strength were analysed using standard methods. Corrosion resistance was evaluated by potentiodynamic polarization. It was found that microstructures are dominated by ferrite and pearlite phases with different morphologies and grain sizes depending on the cooling rate. Increasing the cooling rate resulted in microstructural refinement and chemical homogeneity, improvement in mechanical properties and corrosion resistance of the 6xxx alloy.
43
Tang, Wei Neng, Rong Shi Chen, En Hou Han e Wei Ke. "Flow Behavior and Microstructural Evolution of ZW61 Alloy during Hot Compressive Deformation". Materials Science Forum 686 (giugno 2011): 140–45. http://dx.doi.org/10.4028/www.scientific.net/msf.686.140.
Testo completoAbstract (sommario):
The flow behavior and microstructural evolution of the ZW61 (Mg-6Zn-0.6Y-0.5Zr ) alloy during uniaxial compressive deformation at temperatures of 250-400°C and strain rates of 0.5-0.001s-1.were investigated. The results indicated that the flow stress could be described with a power law equation related to the temperature and strain rate. Furthermore, the deformation microstructures at different strain rates and temperatures were different. Microstructural evolution deformed under 350 °C and 0.001s-1found that the twinning and different modes of slip systems were selectively activated during deformation, and that misorientation in some grains increased with lattice rotation during hot deformation, which resulted in the gradual formation of new grain boundaries. In addition, dynamic recrystallization (DRX) preferably took place nearby the boundaries of original grains/twinning/slipping bands and coarse particles, which resulted in an inhomogeneous deformation microstructure, i.e. necklace microstructure.
44
Talmon, Yeshayahu. "Cryo-TEM of amphiphilic polymer and amphiphile/polymer solutions". Proceedings, annual meeting, Electron Microscopy Society of America 51 (1 agosto 1993): 876–77. http://dx.doi.org/10.1017/s0424820100150216.
Testo completoAbstract (sommario):
To achieve complete microstructural characterization of self-aggregating systems, one needs direct images in addition to quantitative information from non-imaging, e.g., scattering or Theological measurements, techniques. Cryo-TEM enables us to image fluid microstructures at better than one nanometer resolution, with minimal specimen preparation artifacts. Direct images are used to determine the “building blocks” of the fluid microstructure; these are used to build reliable physical models with which quantitative information from techniques such as small-angle x-ray or neutron scattering can be analyzed.To prepare vitrified specimens of microstructured fluids, we have developed the Controlled Environment Vitrification System (CEVS), that enables us to prepare samples under controlled temperature and humidity conditions, thus minimizing microstructural rearrangement due to volatile evaporation or temperature changes. The CEVS may be used to trigger on-the-grid processes to induce formation of new phases, or to study intermediate, transient structures during change of phase (“time-resolved cryo-TEM”). Recently we have developed a new CEVS, where temperature and humidity are controlled by continuous flow of a mixture of humidified and dry air streams.
45
Pancholi, V., A. Raja e K. Rohit. "Deformation Behavior of Inhomogeneous Layered Microstructure". Materials Science Forum 879 (novembre 2016): 1437–42. http://dx.doi.org/10.4028/www.scientific.net/msf.879.1437.
Testo completoAbstract (sommario):
Multipass friction stir processing (FSP) technique was used to get inhomogeneous layered microstructure in Al 5086 alloy. Different proportions of fine and coarse grain microstructures were generated using FSP. In the present work, material with inhomogeneous layered microstructure generated using FSP was subjected to deformation at temperature of 500°C and at strain rate in the range of 5×10-4 to 1×10-2 s-1. It was observed that the inhomogeneous layered microstructure with more than 50% fine grain microstructure is required to get higher elongation to failure. However material having homogeneous fine grain microstructure showed lower elongation to failure than the material having both fine and coarse grain microstructures. By varying the proportion of fine and coarse grain microstructures higher ductility was obtained at higher strain rate as compared to a material with homogeneous microstructure. It is clear that materials with inhomogeneous microstructure are not following “rule of mixture” type of behaviour.
46
Xu, Bin, Kang Guo, Likuan Zhu, Xiaoyu Wu e Jianguo Lei. "Applying Foil Queue Microelectrode with Tapered Structure in Micro-EDM to Eliminate the Step Effect on the 3D Microstructure’s Surface". Micromachines 11, n. 3 (24 marzo 2020): 335. http://dx.doi.org/10.3390/mi11030335.
Testo completoAbstract (sommario):
When using foil queue microelectrodes (FQ-microelectrodes) for micro electrical discharge machining (micro-EDM), the processed results of each foil microelectrode (F-microelectrode) can be stacked to construct three-dimensional (3D) microstructures. However, the surface of the 3D microstructure obtained from this process will have a step effect, which has an adverse effect on the surface quality and shape accuracy of the 3D microstructures. To focus on this problem, this paper proposes to use FQ-microelectrodes with tapered structures for micro-EDM, thereby eliminating the step effect on the 3D microstructure’s surface. By using a low-speed wire EDM machine, a copper foil with thickness of 300 μm was processed to obtain a FQ-microelectrode in which each of the F-microelectrodes has a tapered structure along its thickness direction. These tapered structures could effectively improve the construction precision of the 3D microstructure and effectively eliminate the step effect. In this paper, the effects of the taper angle and the number of microelectrodes on the step effect were investigated. The experimental results show that the step effect on the 3D microstructure’s surface became less evident with the taper angle and the number of F-microelectrodes increased. Finally, under the processing voltage of 120 V, pulse width of 1 μs and pulse interval of 10 μs, a FQ-microelectrode (including 40 F-microelectrodes) with 10° taper angle was used for micro-EDM. The obtained 3D microstructure has good surface quality and the step effect was essentially eliminated.
47
Kawa, Marek. "Failure Criterion for Brick Masonry: A Micro-Mechanics Approach". Studia Geotechnica et Mechanica 36, n. 3 (28 febbraio 2015): 37–48. http://dx.doi.org/10.2478/sgem-2014-0025.
Testo completoAbstract (sommario):
Abstract The paper deals with the formulation of failure criterion for an in-plane loaded masonry. Using micro-mechanics approach the strength estimation for masonry microstructure with constituents obeying the Drucker-Prager criterion is determined numerically. The procedure invokes lower bound analysis: for assumed stress fields constructed within masonry periodic cell critical load is obtained as a solution of constrained optimization problem. The analysis is carried out for many different loading conditions at different orientations of bed joints. The performance of the approach is verified against solutions obtained for corresponding layered and block microstructures, which provides the upper and lower strength bounds for masonry microstructure, respectively. Subsequently, a phenomenological anisotropic strength criterion for masonry microstructure is proposed. The criterion has a form of conjunction of Jaeger critical plane condition and Tsai-Wu criterion. The model proposed is identified based on the fitting of numerical results obtained from the microstructural analysis. Identified criterion is then verified against results obtained for different loading orientations. It appears that strength of masonry microstructure can be satisfactorily described by the criterion proposed.
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Park, C. H., Young Gun Ko, Chong Soo Lee, Kyung Tae Park, Dong Hyuk Shin e Ho Sung Lee. "High-Temperature Deformation Behavior of ELI Grade Ti-6Al-4V Alloy with Martensite Microstructure". Materials Science Forum 551-552 (luglio 2007): 365–72. http://dx.doi.org/10.4028/www.scientific.net/msf.551-552.365.
Testo completoAbstract (sommario):
High-temperature deformation behavior and microstructural evolution process of ELI Ti-6Al-4V alloy having martensite microstructure were investigated with the variation of strain, strain rate and temperature. A series of hot compression tests was carried out isothermally for martensite microstructure at the true strain range of 0.6 to 1.4, strain rate range of 10-3 s-1 to 1 s-1 and temperature range of 700 oC to 950 oC. The processing maps for martensite microstructures were constructed on the basis of dynamic materials model (DMM). At the strain rate higher than 10-2 s-1 and the temperature lower than 750 oC regions of flow instability such as adiabatic shear band and micro-cracking were observed. Also, after imposing an effective strain of ≈ 1.4, deformed microstructure showed the significant kinking/bending behavior of lamellae resulting in the dynamic globularization associated with the fragmentation of beta-phase. The effects of strain, strain rate and temperature for dynamic globularization were discussed based on the microstructure and efficiency of power dissipation.
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Zhang, Yaodan, Zhijun Li, Yuanren Xiu, Chunjiang Li, Baosen Zhang e Yu Deng. "Microstructural Characteristics of Frazil Particles and the Physical Properties of Frazil Ice in the Yellow River, China". Crystals 11, n. 6 (31 maggio 2021): 617. http://dx.doi.org/10.3390/cryst11060617.
Testo completoAbstract (sommario):
Frazil particles, ice crystals or slushy granules that form in turbulent water, change the freezing properties of ice to create “frazil ice”. To understand the microstructural characteristics of these particles and the physical properties of frazil ice in greater depth, an in situ sampler was designed to collect frazil particles in the Yellow River. The ice crystal microstructural characteristics of the frazil particles (morphology, size, air bubble, and sediment) were observed under a microscope, and their nucleation mechanism was analyzed according to its microstructure. The physical properties of frazil ice (ice crystal microstructure, air bubble, ice density, and sediment content) were also observed. The results showed that these microstructures of frazil particles can be divided into four types: granular, dendritic, needle-like, and serrated. The size of the measured frazil particles ranged from 0.1 to 25 mm. Compared with columnar ice, the crystal microstructure of frazil ice is irregular, with a mean crystal diameter less than 5 mm extending in all directions. The crystal grain size and ice density of frazil ice are smaller than columnar ice, but the bubble and sediment content are larger.
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Muiruri, Amos, Maina Maringa e Willie du Preez. "Validation of a Microstructure-Based Model for Predicting the High Strain Rate Flow Properties of Various Forms of Additively Manufactured Ti6Al4V(ELI) Alloy". Metals 11, n. 10 (13 ottobre 2021): 1628. http://dx.doi.org/10.3390/met11101628.
Testo completoAbstract (sommario):
To increase the acceptance of direct metal laser sintered Ti6Al4V(Extra Low Interstitial—ELI) in industry, analytical models that can quantitatively describe the interrelationships between the microstructural features, field variables, such as temperature and strain rate, and the mechanical properties are necessary. In the present study, a physical model that articulates the critical microstructural features of grain sizes and dislocation densities for use in predicting the mechanical properties of additively manufactured Ti6Al4V(ELI) was developed. The flow stress curves of different microstructures of the alloy were used to obtain and refine the parameters of the physical model. The average grain size of a microstructure was shown to influence the athermal part of yield stress, while the initial dislocation density in a microstructure was seen to affect the shape of the flow stress curve. The viscous drag effect was also shown to play a critical role in explaining the upturn of flow stress at high strain rates. The microstructure-based constitutive model developed and validated in this article using experimental data showed good capacity to predict the high strain rate flow properties of additively manufactured Ti6Al4V(ELI) alloy.