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1
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.
Abstract (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.
2
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.
Abstract (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.
3
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.
Abstract (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.
4
Yue, Tao, Shenyu Gu, Na Liu, Yuanyuan Liu, Yancong Yu, Xinye Zhang, Weixia Lan, Toshio Fukuda, Long Li e Quan Zhang. "Self-alignment of microstructures based on lateral fluidic force generated by local spatial asymmetry inside a microfluidic channel". AIP Advances 12, n. 3 (1 marzo 2022): 035335. http://dx.doi.org/10.1063/5.0086138.
Abstract (sommario):
Three-dimensional (3D) microstructures have various applications in many fields due to their unique physical properties. Manufacturing 3D microstructures with precise micron-scale features is difficult. Although the assembly of two-dimensional (2D) structures is a smart way to construct complex 3D microstructures, the way to assemble those 2D structures precisely is still immature. One key issue is that alignment errors often occur during the assembly process, affecting the architecture accuracy of the assembled 3D structures. In this paper, we propose a method to eliminate the alignment error during the self-assembly process only by lateral fluid force. Theoretical analysis has been conducted to demonstrate how alignment errors in the assembly channel are automatically corrected, during which a force perpendicular to the flow direction is generated by the channel’s local spatial asymmetry to automatically correct those alignment errors. Besides, the movement of microstructures in the channel has been numerically simulated, whose results were consistent with the theoretical analysis, and there was indeed a lateral force that causes the self-aligning of the microstructure in the channel. The effect of the microstructure’s dimensions and the channel’s size for self-alignment procedure has also been analyzed. It shows that the self-alignment of the microstructure can complete when the ratio of the diameter of microstructures to the width of the channel is greater than 85%. Besides, experiments of the self-alignment between adjacent layers of microstructures were successful, which show the presented idea using lateral fluid force is a promising way to build 3D structures with less assembly errors.
5
Rodgers, Theron M., Hojun Lim e Judith A. Brown. "Three-Dimensional Additively Manufactured Microstructures and Their Mechanical Properties". JOM 72, n. 1 (30 ottobre 2019): 75–82. http://dx.doi.org/10.1007/s11837-019-03808-x.
Abstract (sommario):
Abstract Metal additive manufacturing (AM) allows for the freeform creation of complex parts. However, AM microstructures are highly sensitive to the process parameters used. Resulting microstructures vary significantly from typical metal alloys in grain morphology distributions, defect populations and crystallographic texture. AM microstructures are often anisotropic and possess three-dimensional features. These microstructural features determine the mechanical properties of AM parts. Here, we reproduce three “canonical” AM microstructures from the literature and investigate their mechanical responses. Stochastic volume elements are generated with a kinetic Monte Carlo process simulation. A crystal plasticity-finite element model is then used to simulate plastic deformation of the AM microstructures and a reference equiaxed microstructure. Results demonstrate that AM microstructures possess significant variability in strength and plastic anisotropy compared with conventional equiaxed microstructures.
6
Beh, Chong You, Ee Meng Cheng, Xiao Jian Tan, Nashrul Fazli Mohd Nasir, Mohd Shukry Abdul Majid, Mohd Ridzuan Mohd Jamir, Shing Fhan Khor, Kim Yee Lee e Che Wan Sharifah Robiah Mohamad. "Complex Impedance and Modulus Analysis on Porous and Non-Porous Scaffold Composites Due to Effect of Hydroxyapatite/Starch Proportion". Polymers 15, n. 2 (8 gennaio 2023): 320. http://dx.doi.org/10.3390/polym15020320.
Abstract (sommario):
This study aims to investigate the electric responses (complex modulus and complex impedance analysis) of hydroxyapatite/starch bone scaffold as a function of hydroxyapatite/starch proportion and the microstructural features. Hence, the non-porous and porous hydroxyapatite/starch composites were fabricated with various hydroxyapatite/starch proportions (70/30, 60/40, 50/50, 40/60, 30/70, 20/80, and 10/90 wt/wt%). Microstructural analysis of the porous hydroxyapatite/starch composites was carried out by using scanning electron microscopy. It shows that the formation of hierarchical porous microstructures with high porosity is more significant at a high starch proportion. The complex modulus and complex impedance analysis were conducted to investigate the electrical conduction mechanism of the hydroxyapatite/starch composites via dielectric spectroscopy within a frequency range from 5 MHz to 12 GHz. The electrical responses of the hydroxyapatite/starch composites are highly dependent on the frequency, material proportion, and microstructures. High starch proportion and highly porous hierarchical microstructures enhance the electrical responses of the hydroxyapatite/starch composite. The material proportion and microstructure features of the hydroxyapatite/starch composites can be indirectly reflected by the simulated electrical parameters of the equivalent electrical circuit models.
7
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.
Abstract (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.
8
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.
Abstract (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.
9
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.
Abstract (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.
10
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.
Abstract (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.
11
Burke, M. G., e M. K. Miller. "A Comparison of Tem and Apfim to the Interpretation of Modulated Microstructures". Proceedings, annual meeting, Electron Microscopy Society of America 43 (agosto 1985): 70–71. http://dx.doi.org/10.1017/s042482010011742x.
Abstract (sommario):
Interpretation of fine-scale microstructures containing high volume fractions of second phase is complex. In particular, microstructures developed through decomposition within low temperature miscibility gaps may be extremely fine. This paper compares the morphological interpretations of such complex microstructures by the high-resolution techniques of TEM and atom probe field-ion microscopy (APFIM).The Fe-25 at% Be alloy selected for this study was aged within the low temperature miscibility gap to form a <100> aligned two-phase microstructure. This triaxially modulated microstructure is composed of an Fe-rich ferrite phase and a B2-ordered Be-enriched phase. The microstructural characterization through conventional bright-field TEM is inadequate because of the many contributions to image contrast. The ordering reaction which accompanies spinodal decomposition in this alloy permits simplification of the image by the use of the centered dark field technique to image just one phase. A CDF image formed with a B2 superlattice reflection is shown in fig. 1. In this CDF micrograph, the the B2-ordered Be-enriched phase appears as bright regions in the darkly-imaging ferrite. By examining the specimen in a [001] orientation, the <100> nature of the modulations is evident.
12
Robson, J. D., O. Engler, C. Sigli, A. Deschamps e W. J. Poole. "Advances in Microstructural Understanding of Wrought Aluminum Alloys". Metallurgical and Materials Transactions A 51, n. 9 (8 luglio 2020): 4377–89. http://dx.doi.org/10.1007/s11661-020-05908-9.
Abstract (sommario):
Abstract Wrought aluminum alloys are an attractive option in the quest for lightweight, recyclable, structural materials. Modern wrought aluminum alloys depend on control of complex microstructures to obtain their properties. This requires an understanding of the coupling between alloy composition, processing, and microstructure. This paper summarizes recent work to understand microstructural evolution in such alloys, utilizing the advanced characterization techniques now available such as atom probe tomography, high-resolution electron microscopy, and synchrotron X-ray diffraction and scattering. New insights into precipitation processes, deformation behavior, and texture evolution are discussed. Recent progress in predicting microstructural evolution using computer modeling is also summarized.
13
Bassini, Emilio, Giulio Marchese e Alberta Aversa. "Tailoring of the Microstructure of Laser Powder Bed Fused Inconel 718 Using Solution Annealing and Aging Treatments". Metals 11, n. 6 (5 giugno 2021): 921. http://dx.doi.org/10.3390/met11060921.
Abstract (sommario):
Inconel 718 (IN718) is a nickel-based superalloy with high weldability and is thus ideal for being processed via laser powder bed fusion (LPBF). Unlike traditional casting, LPBF IN718 develops a complex microstructure due to the rapid solidification that characterizes this manufacturing process. As a result, LPBF microstructures are different from those expected in equilibrium conditions, and for this reason, specific heat treatments should be designed. This paper, using differential scanning calorimetry (DSC), thermal mechanical analysis (TMA), and a field emission scanning electron microscope (FESEM), aims to develop a complete heat treatment that maximizes the material strength, thereby enhancing its microstructure. The paper shows that high-temperature annealing followed by two aging steps is the most suitable way to achieve the abovementioned task. More specifically, a complete dissolution of the δ phase via solution annealing at 1080 °C is the key factor in gaining an even and intense precipitation of γ′ and γ″ during the subsequent aging treatments. The microstructural analyses showed the elimination of needle-like δ particles and detrimental Laves phases. At the same time, intense precipitation of spherical and of discoidal reinforcing particles was achieved by performing the aging treatments at 720 and 630 °C, respectively.
14
Ott, J., A. Burghardt, D. Britz, S. Majauskaite e F. Mücklich. "Qualitative and Quantitative Microstructural Analysis of Copper for Sintering Process Optimization in Additive Manufacturing Applications". Practical Metallography 58, n. 1 (1 gennaio 2021): 32–47. http://dx.doi.org/10.1515/pm-2020-0002.
Abstract (sommario):
Abstract This work will present possibilities for the characterization of copper powder green bodies and sintered copper microstructures during pressureless sintering. The introduction of new parameters to microstructural characterization based on qualitative and quantitative microstructural analysis will facilitate the systematic optimization of the sintering process. As a result of the specific evaluation of the microstructure evolution, conventional isothermal sintering could be successfully replaced by multi-step temperature profiles, thus achieving sintering densities of more than 99 % by simultaneously reducing process time. This systematic optimization of the sintering process of Cu through specific microstructural analysis may now be applied to sinter-based manufacturing technologies such as Binder Jetting and Metal Powder Injection Moulding, enabling the manufacture of complex and highly conductive Cu parts for applications in electronics.
15
Snopiński, Przemysław, Krzysztof Matus e Ondřej Hilšer. "Investigation of the Effects of Various Severe Plastic Deformation Techniques on the Microstructure of Laser Powder Bed Fusion AlSi10Mg Alloy". Materials 16, n. 23 (29 novembre 2023): 7418. http://dx.doi.org/10.3390/ma16237418.
Abstract (sommario):
In this paper, we present a complete characterization of the microstructural changes that occur in an LPBF AlSi10Mg alloy subjected to various post-processing methods, including equal-channel angular pressing (ECAP), KoBo extrusion, and multi-axial forging. Kikuchi transmission diffraction and transmission electron microscopy were used to examine the microstructures. Our findings revealed that multi-axis forging produced an extremely fine subgrain structure. KoBo extrusion resulted in a practically dislocation-free microstructure. ECAP processing at temperatures between 100 °C and 200 °C generated moderate grain refinement, with subgrain diameters averaging from 300 nm to 700 nm. The obtained data highlighted the potential of severe plastic deformation as a versatile method for tailoring the microstructure of the AlSi10Mg alloy. The ability to precisely control grain size and dislocation density using specific SPD methods allows for the development of novel materials with ultrafine-grained microstructures that offer the potential for enhanced mechanical and functional properties.
16
Regone, Wiliam, e Sérgio Tonini Button. "Effects of deformation on the microstructure of a Ti-V microalloyed steel in the phase transition region". Rem: Revista Escola de Minas 57, n. 4 (dicembre 2004): 303–11. http://dx.doi.org/10.1590/s0370-44672004000400014.
Abstract (sommario):
Microalloyed steels are used in the forging of many automotive parts like crankshafts and connecting rods. They are hot worked in a sequence of stages that includes the heating to the soaking temperature, followed by forging steps, and finally the controlled cooling to define the microstructure and mechanical properties. In this work it was investigated the thermomechanical behavior and the microstructural evolution of a Ti-V microalloyed steel in the phase transition region. Torsion tests were done with multiple steps with true strain equal to 0.26 in each step. After each torsion step the samples were continuous cooled for 15 seconds to simulate hot forging conditions. These tests provided results for the temperature at the beginning of the phase transformation, and allowed to analyze the microstructural changes. Also, workability tests were held to analyze the microstructural evolution by optical and scanning electron microscopy. Results from the torsion tests showed that the temperature for the beginning of phase transformation is about 700 ºC. Workability tests held at 700 ºC followed by water-cooling presented microstructures with different regions: strain hardened, and static and dynamic recrystallized. Workability tests at 700 ºC followed by air-cooling showed a complex microstructure with ferrite, bainite and martensite, while tests at 650 and 600 ºC followed by water-cooling showed a microstructure with allotriomorphic ferrite present in the grain boundaries of the previous austenite.
17
Silva, M. A., e J. N. F. Holanda. "Electrical Porcelain Containing Ornamental Rock Waste: Microstructural Development". Materials Science Forum 660-661 (ottobre 2010): 692–96. http://dx.doi.org/10.4028/www.scientific.net/msf.660-661.692.
Abstract (sommario):
Aluminous electrical porcelains are used in the production of materials of high voltage insulators. The microstructure plays an important role in the performance of electrical porcelain. On the other hand, the porcelain materials undergo a series of physical and chemical transformations during firing. This makes the understanding of their microstructures rather complex. In this work was studied the microstructural development of electrical porcelain containing up to 35 wt.% of ornamental rock waste. The pieces ceramics were pressed at 50 MPa and sintered at 1300 °C. The porcelain pieces were characterized via X-ray diffraction and scanning electron microscopy. The results indicate that the presence of the ornamental rock waste influenced the microstructural development of the pieces of electrical aluminous porcelain.
18
Rodriguez, Salvador Valtierra, Michael Greenwood, Delin Li, Jean-Benoît Lévesque, Vladimir Timoshevskii, Daniel Paquet e Nikolas Provatas. "Phase-field modeling of austenitic steels used in turbines". IOP Conference Series: Materials Science and Engineering 1281, n. 1 (1 maggio 2023): 012047. http://dx.doi.org/10.1088/1757-899x/1281/1/012047.
Abstract (sommario):
Abstract The performance in hydro-electric turbine casting and repair requires understanding of how process parameters and chemistry selection affect solidification microstructures. The aim of this study is to provide a quantitative phase-field formulation for process-microstructure relationships that seeks to model stainless steels. We have developed a phase-field model to simulate austenitic stainless steel solidification under experimental thermal histories. To this end we look at a pseudo-binary approximations for numerical efficiency. The pseudo-binary formulation is underpinned by the alloying element equivalent value, a metallurgical tool used to analyze the microstructural impact of “minor” alloying elements in stainless steels. For model validation we develop thin wall casting experiments to measure the thermal history and chemistry controlled microstructure. The models incorporate a thermodynamic parameterization and are linked to a thermal-phase transformation model which represents the experimentally measured thermal history. The results display a good agreement with the primary branch spacing and cellular to dendritic transition of the casting experiments. These models and software provide the basis for future expansion to include more complex microstructures.
19
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.
Abstract (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.
20
Yamane, Gen, Vincent Velay, Vanessa Vidal e Hiroaki Matsumoto. "Mechanical Behavior of Ti-6Al-2Sn-4Zr-2Mo Titanium Alloy under Hot and Superplastic Forming Conditions: Experiment and Modeling". Defect and Diffusion Forum 385 (luglio 2018): 413–18. http://dx.doi.org/10.4028/www.scientific.net/ddf.385.413.
Abstract (sommario):
Titanium alloys are widely used in the aircraft industry. Under sheets form, they can be employed to the manufacturing of pylon or engine parts. With the aim of a cost reduction, this study proposes to act on the starting microstructure so as to improve the mechanical properties during the forming stages. In the present study, investigations are focused on Ti-6Al-2Sn-4Zr-2Mo (Ti6242) alloy specially used for the hot areas (e.g. parts close to the engine or the combustion chambe...). Presently, an important mechanical test campaign was performed on Ti6242 alloy, it examines, on the one hand, the microstructure qualified by the aircraft industry and, on the other hand, a new range of refined microstructures obtained by hot straining process. For each test, microstructural observations exhibited complex phenomena including simultaneously both grain growth and dynamic recrystallization. The occurrence, sequencing and coupling of the mechanisms, strongly depend on the starting microstructure and the test conditions (time-temperature and strain rate) investigated. They are not easy to understand and require further tests and observations. In such a framework, the implementation of mechanical models are efficient and relevant to promote a better knowledge of the microstructural evolution observed and their influence on the mechanical behavior.
21
Jirková, Hana, David Aišman, Indrani Sen, Martin F. X. Wagner, Mária Behúlová, Martin Kusý e Bohuslav Mašek. "Mini-Thixoforming of a Steel Produced by Powder Metallurgy". Solid State Phenomena 192-193 (ottobre 2012): 500–505. http://dx.doi.org/10.4028/www.scientific.net/ssp.192-193.500.
Abstract (sommario):
Semi-solid processing is complicated by various inherent technical problems. However, once these problems are solved, thixoforming allows intricately shaped components to be manufactured very effectively – often with microstructures that cannot be produced by any other techniques. The recently introduced mini-thixoforming method is an example of such a novel technique for semi-solid processing of steel. The wall thicknesses of resulting parts are about 1 mm. Microstructures of semi-solid-processed steels typically consist of a high proportion of globular particles of metastable austenite embedded in a carbide network, the latter being much harder and more brittle. This paper illustrates that mini-thixoforming allows inverting that microstructural configuration. As an experimental material, powder steel with increased content of vanadium and chromium was used. The post-thixoforming microstructure consisted of a dispersion of carbides and high-vanadium and high-chromium eutectic in an austenitic matrix. Applying optimised processing parameters, complex-shaped parts could be produced. According to the high hardness of resulting microstructural components, the new materials are likely to exhibit extraordinary strength and wear resistance.
22
Iza-Mendia, Amaia, e Isabel Gutiérrez. "Microstructure-Mechanical Properties Relationships for Complex Microstructures in High Strength Steels". Materials Science Forum 783-786 (maggio 2014): 783–88. http://dx.doi.org/10.4028/www.scientific.net/msf.783-786.783.
Abstract (sommario):
Due to the increased complexity of steel microstructures, when considering the application of available Hall-Petch type equations for yield strength prediction, a number of difficulties raises. For example, the correlation between grain size measurements by EBSD technique and optical microscopy (OP) in complex microstructures is required in order to integrate data to the traditional equations developed for OP results and ferrite-pearlite microstructures. Besides, the introduction of some additional terms to the equations to account for precipitation, C in solution and forest dislocation contributions presents some difficulties that need to be overcome to improve prediction accuracy. Different microstructures (ferrite-pearlite, bainite, quenched and Q&T) have been produced by thermal and thermomechanical treatments, followed by microstructural characterisation and mechanical testing. A Hall-Petch coefficient dependent on the boundary misorientation distribution is proposed. This approach allows dealing in a similar way ferritic, bainitic and martensitic microstructures. The Hall-Petch coefficient, thus defined, corresponds to the previously proposed by Pickering for ferrite, while bainitic microstructures give a smaller value. Additionally, the equation used to express the fracture appearance transition temperature of ferritic-pearlitic microstructure has been generalized from the developments made in the calculation of the yield stress.
23
Liu, Lishuai, Peng Wu, Yanxun Xiang e Fu-Zhen Xuan. "Autonomous characterization of grain size distribution using nonlinear Lamb waves based on deep learning". Journal of the Acoustical Society of America 152, n. 3 (settembre 2022): 1913–21. http://dx.doi.org/10.1121/10.0014289.
Abstract (sommario):
Characterization of grain microstructures of metallic materials is crucial to materials science and engineering applications. Unfortunately, the universal electron microscopic methodologies can only capture two-dimensional local observations of the microstructures in a time-consuming destructive way. In this regard, the nonlinear ultrasonic technique shows the potential for efficient and nondestructive microstructure characterization due to its high sensitivity to microstructural features of materials, but is hindered by the ill-posed inverse problem for multiparameter estimation induced by the incomplete understanding of the complicated nonlinear mechanical interaction mechanism. We propose an explainable nonlinearity-aware multilevel wavelet decomposition-multichannel one-dimensional convolutional neural network to hierarchically extracts multilevel time-frequency features of the acoustic nonlinearity and automatically model latent nonlinear dynamics directly from the nonlinear ultrasonic responses. The results demonstrate that the proposed approach establishes the complex mapping between acoustic nonlinearity and microstructural features, thereby determining the lognormal distribution of grain size in metallic materials rather than only average grain size. In the meantime, the integration of the designed nonlinearity-aware network and the quantitative analysis of component importance provides an acceptable physical explainability of the deep learning approach for the nonlinear ultrasonic technique. Our study shows the promise of this technique for real-time in situ evaluation of microstructural evolution in various applications.
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Strzelecki, Piotr Jan, Anna Świerczewska, Katarzyna Kopczewska, Adam Fheed, Jacek Tarasiuk e Sebastian Wroński. "Decoding Rocks: An Assessment of Geomaterial Microstructure Using X-ray Microtomography, Image Analysis and Multivariate Statistics". Materials 14, n. 12 (13 giugno 2021): 3266. http://dx.doi.org/10.3390/ma14123266.
Abstract (sommario):
An understanding of the microstructure of geomaterials such as rocks is fundamental in the evaluation of their functional properties, as well as the decryption of their geological history. We present a semi-automated statistical protocol for a complex 3D characterization of the microstructure of granular materials, including the clustering of grains and a description of their chemical composition, size, shape, and spatial properties with 44 unique parameters. The approach consists of an X-ray microtomographic image processing procedure, followed by measurements using image analysis and statistical multivariate analysis of its results utilizing freeware and widely available software. The statistical approach proposed was tested out on a sandstone sample with hidden and localized deformational microstructures. The grains were clustered into distinctive groups covering different compositional and geometrical features of the sample’s granular framework. The grains are pervasively and evenly distributed within the analysed sample. The spatial arrangement of grains in particular clusters is well organized and shows a directional trend referring to both microstructures. The methodological approach can be applied to any other rock type and enables the tracking of microstructural trends in grains arrangement.
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di Schino, Andrea, e Mauro Guagnelli. "Metallurgical Design of High Strength/High Toughness Steels". Materials Science Forum 706-709 (gennaio 2012): 2084–89. http://dx.doi.org/10.4028/www.scientific.net/msf.706-709.2084.
Abstract (sommario):
The proper balance between yield strength, YS, and ductile to brittle transition temperature, DBTT, has been the main concern during development of high strength engineering steels and the effect of microstructure on impact toughness has attracted a great attention during the last decades. In this paper a review concerning the relationship between strength and toughness in steels will be presented and the effect of different microstructural parameters will be discussed, aiming toimprovesuch properties in designingnewhigh strength steels. Complex microstructures, obtained by quenching and tempering (Q&T) and thermo-mechanical (TM) processing are considered. The steels are low/medium carbon steels (C=0.04%-0.40%) with yield strength in the range YS=500-1000 MPa. Results show that the strength and the impact toughness behaviour are controlled by different microstructural parameters and not, as in the case of polygonal ferritic steels, by the same structural unit (the grain size) and that a “fine” microstructure is required in order to achieve high levels of both strength and toughness. The metallurgical design of high strength steels with toughness requirements is discussed using the same approach for both Q&T and TMCP processes.
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Nolan, T. P., R. Sinclair, T. Yamashita e R. Ranjan. "Correlation of microstructural and magnetic properties of longitudinal recording media using TEM". Proceedings, annual meeting, Electron Microscopy Society of America 51 (1 agosto 1993): 1016–17. http://dx.doi.org/10.1017/s0424820100150915.
Abstract (sommario):
Cobalt alloy on chromium thin film media are used in industry because of their large values of coercivity (Hc), remanent magnetization (Mr), squareness (S*), and relatively low noise. The magnetic properties depend strongly on processing conditions and, as will be shown, the resulting microstructure.A complete structure-processing-properties analysis requires effective measurement of both magnetic and microstructural properties. Direct micromagnetic-microstructural comparison is not yet readily available, but bulk hysteresis loop parameters are reproducible and highly correlated with both desired recording characteristics and microstructures, and so provide a valuable, albeit indirect comparison. Signal to noise (S/N) measurements are also used as a more direct measure of usefulness in a high density disk drive. The nanoscale microstructural features which dramatically affect these bulk magnetic properties are difficult to observe. However, careful combination of TEM techniques, including bright-field, dark-field, high-resolution, selected area diffraction and elongated-probe microdiffraction can determine the subtle microstructural differences.
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Hanhan, Imad, e Michael D. Sangid. "Design of Low Cost Carbon Fiber Composites via Examining the Micromechanical Stress Distributions in A42 Bean-Shaped versus T650 Circular Fibers". Journal of Composites Science 5, n. 11 (7 novembre 2021): 294. http://dx.doi.org/10.3390/jcs5110294.
Abstract (sommario):
Recent advancements have led to new polyacrylonitrile carbon fiber precursors which reduce production costs, yet lead to bean-shaped cross-sections. While these bean-shaped fibers have comparable stiffness and ultimate strength values to typical carbon fibers, their unique morphology results in varying in-plane orientations and different microstructural stress distributions under loading, which are not well understood and can limit failure strength under complex loading scenarios. Therefore, this work used finite element simulations to compare longitudinal stress distributions in A42 (bean-shaped) and T650 (circular) carbon fiber composite microstructures. Specifically, a microscopy image of an A42/P6300 microstructure was processed to instantiate a 3D model, while a Monte Carlo approach (which accounts for size and in-plane orientation distributions) was used to create statistically equivalent A42/P6300 and T650/P6300 microstructures. First, the results showed that the measured in-plane orientations of the A42 carbon fibers for the analyzed specimen had an orderly distribution with peaks at |ϕ|=0∘,180∘. Additionally, the results showed that under 1.5% elongation, the A42/P6300 microstructure reached simulated failure at approximately 2108 MPa, while the T650/P6300 microstructure did not reach failure. A single fiber model showed that this was due to the curvature of A42 fibers which was 3.18 μm−1 higher at the inner corner, yielding a matrix stress that was 7 MPa higher compared to the T650/P6300 microstructure. Overall, this analysis is valuable to engineers designing new components using lower cost carbon fiber composites, based on the micromechanical stress distributions and unique packing abilities resulting from the A42 fiber morphologies.
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Sun, Jia, Lingyan Zhao, Huaxin Liang, Yao Zhang, Xuexiong Li, Chunyu Teng, Hao Wang e Hailong Bai. "A Review on Phase Field Modeling for Formation of η-Cu6Sn5 Intermetallic". Metals 12, n. 12 (28 novembre 2022): 2043. http://dx.doi.org/10.3390/met12122043.
Abstract (sommario):
Formation of intermetallic compounds (IMCs) exhibits remarkable microstructural features and provides opportunities for microstructure control of microelectronic interconnects. Excessive formation of brittle IMCs at the Cu/Sn interface such as η-Cu6Sn5 can deteriorate the reliability and in turn lead to solder joint failure in the Pb-free Sn-based solder joints. Phase field method is a versatile tool for prediction of the mesoscopic structure evolution in solders, which does not require tracking interfaces. The relationships between the microstructures, reliability and wettability were widely investigated, and several formation and growth mechanisms were also proposed for η-Cu6Sn5. In this paper, the current research works are reviewed and the prospective of the application of phase field method in the formation of η-Cu6Sn5 are discussed. Combined phase field simulations hold great promise in modeling the formation kinetics of IMCs with complex microstructural and chemical interactions.
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Go Roa, Stewart M., Eduardo Magdaluyo Jr. e Wojciech Gierlotka. "Microstructural Characterization and Properties of Sn-Ag-Cu (SAC) Compound Induced by Zn Alloying". Nano Hybrids and Composites 16 (giugno 2017): 33–36. http://dx.doi.org/10.4028/www.scientific.net/nhc.16.33.
Abstract (sommario):
The microstructural properties and intermetallic (IMC) formation of Sn-Ag-Cu (SAC) through varying amounts of zinc were examined in this study while having tin held at constant composition. Samples were prepared and heated in a furnace for 168 hours to achieve complete solidification and homogenization. Results showed relatively fine microstructure primarily containing Sn dendrites, eutectic, and pro-eutectic phases. Microstructures for each alloy was similar for which majority of them formed copper-based IMCs and Sn dendrites. The alloy (0.7Sn-0.15Ag-0.1Cu-0.05Zn) containing minimal amount of zinc with high amount of Ag resulted to high Vickers hardness number. Structural analysis showed that these group of alloys composed mainly of β-Sn, Cu6Sn5, and Ag3Sn.
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Bandaru, Pravallika, Saswata Bhattacharyya e Shourya Dutta-Gupta. "Insights into propagating surface plasmons in Ag–Cu alloy thin films: Enhancement of spin angular momentum of light". Journal of Applied Physics 132, n. 18 (14 novembre 2022): 183101. http://dx.doi.org/10.1063/5.0119124.
Abstract (sommario):
Surface plasmon polaritons (SPPs) can be supported by metal–dielectric interfaces and have been exploited for various applications. Typically, most studies deal with plasmons excited in pure metallic films or homogenous alloy thin films and the understanding of plasmon behavior in films with complex microstructures is limited. In this work, we numerically study the surface plasmons that are supported at the interface of an Ag–Cu alloy film that undergoes spinodal decomposition to produce a two-phase microstructure, when an initially compositionally homogenous alloy film (with composition within spinodal limits) is processed within the miscibility gap. We use phase-field simulated spinodally decomposed microstructures for our optical simulations to study the effect of microstructure on propagating surface plasmons in Ag–Cu alloy films. We demonstrate that the far-field response is governed principally by the composition of the alloy film and is not affected by the microstructural feature size. On the contrary, near-fields are strongly dependent on the microstructure and composition of the films. The origin of inhomogenous fields is demonstrated to be the result of constructive and destructive interference of SPPs. Finally, we demonstrate the enhancement of both transverse and longitudinal components of spin angular momentum in these phase-separated alloy films. The longitudinal components can be enhanced by more than a hundred times in the alloy films as compared to the pure metal films. This study paves the way for exploiting multi-phase alloy thin films for applications in sensing, nanomanipulation, and light modulation.
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Wusatowska-Sarnek, Agnieszka M., Gautam Ghosh, Gregory B. Olson, Martin J. Blackburn e Mark Aindow. "Characterization of the microstructure and phase equilibria calculations for the powder metallurgy superalloy IN100". Journal of Materials Research 18, n. 11 (novembre 2003): 2653–63. http://dx.doi.org/10.1557/jmr.2003.0371.
Abstract (sommario):
The microstructure of the Ni-based superalloy IN100 processed by a powder metallurgy route was evaluated to reveal the structures, volume fractions, distributions, and chemistries of the various phases present. These data were compared with those predicted by computational thermodynamics. It is shown that the microstructural parameters expected on the basis of global equilibrium conditions differ significantly from those measured experimentally. However, modification of these calculations by use of constrained and successive equilibria compensated for kinetic effects and led to accurate (or better) predictions of phase volume fractions and chemistries in this alloy. This demonstrated that such modified phase equilibria calculations could be powerful tools for modeling microstructures, even in complex multicomponent alloys processed under nonequilibrium conditions.
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Rakesh, C., Ravi Babu T., Vandna Kumari, Sonali Jayronia, Fouad A. Al-Saady e Amandeep Nagpal. "Multiscale Characterization of Microstructural Evolution in Powder Metallurgy and Ceramic Forming Processes". E3S Web of Conferences 430 (2023): 01128. http://dx.doi.org/10.1051/e3sconf/202343001128.
Abstract (sommario):
The microstructural evolution of materials during powder metallurgy and ceramic forming processes is a complex phenomenon that spans multiple length scales. In this study, we present a comprehensive multiscale characterization of the microstructural changes occurring during these processes. We employ a combination of advanced experimental techniques, including high-resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM), and X-ray diffraction (XRD), to investigate the microstructural features at various length scales. Our results reveal the intricate interplay between grain growth, phase transformation, and defect formation during sintering and forming processes. We observe a strong correlation between the initial powder characteristics, such as particle size and morphology, and the resulting microstructure. Furthermore, we employ phase-field modeling to simulate the microstructural evolution and validate our experimental findings. Our simulations provide insights into the kinetics of grain growth and the role of interfacial energy in governing microstructural changes. The results of this study have significant implications for the design and optimization of powder metallurgy and ceramic forming processes, enabling the tailoring of microstructures for specific applications. This work contributes to the fundamental understanding of microstructural evolution in these processes and paves the way for the development of advanced materials with tailored properties.
33
Aroca, V. P., C. Philippot, J. Pujante, D. Frómeta, F. G. Caballero e C. Capdevila. "Crashworthiness evaluation of press hardened steels with different lath-like microstructures." IOP Conference Series: Materials Science and Engineering 1284, n. 1 (1 giugno 2023): 012034. http://dx.doi.org/10.1088/1757-899x/1284/1/012034.
Abstract (sommario):
Abstract The deployment of Press Hardened Steels (PHSs) in the Body-In-White structures that took place during the two last decades is at the origin of a breakthrough weight saving on vehicles while guaranteeing the safety requirements of the automotive industry. The production of parts with complex shapes and a high strength between 1500-2000MPa was made possible by taking advantage of the hot rheology of austenite combined with the fast cooling obtained by in-die quenching leading to auto-tempered martensitic microstructures. In the present work, PHS1500 was hot stamped with different thermomechanical processes to promote different lath-like microstructures (bainite, tempered martensite…). An innovative approach is proposed to link the complex microstructures formed between thermoregulated dies to the mechanical behaviour and local ductility of these materials during crash-like solicitations. The microstructure has been characterised through a multi-characterization technique approach including light optical microscopy, scanning electron microscopy and X-ray diffraction. The local ductility is assessed with a combination of crack initiation tests (bending, notch tensile test) and crack propagation resistance tests (Essential work of fracture). Despite similar microstructural crystallographic features, lower bainite and auto-tempered martensite can lead to very different strength – local ductility compromise.
34
Fuentes, Sandrine. "LA TRADUCTION DES NOMS DE PROFESSION DANS UN SYSTÈME DE DICTIONNAIRES ÉLECTRONIQUES COORDONNÉS (ES-FR)". Verbum 7, n. 7 (20 dicembre 2016): 66. http://dx.doi.org/10.15388/verb.2016.7.10259.
Abstract (sommario):
Dans cet article, nous nous attachons à la problématique posée par la traduction des noms de professions de l’espagnol vers le français et ce, dans une perspective de Traitement Automatique des Langues (TAL). Malgré la proximité linguistique des deux langues mises en regard, des obstacles d’ordre général comme la polysémie ou le figement et d’autres plus spécifiques comme le haut degré de technicité des termes concernés ou encore la structure interne complexe des syntagmes terminologiques peuvent entraver le processus de traduction automatique. C’est pourquoi il est nécessaire de fournir au système des descriptions linguistiques exhaustives, minutieuses et formalisées. C’est ce que nous proposons dans le dictionnaire électronique DicPro, où chaque lemme est associé à des champs lexicographiques de différents types (morphologique, sémantique, syntaxique, etc.) et ce, conformément au modèle de microstructure des dictionnaires électroniques conçus au sein du LDI (Université Paris 13). Il convient de souligner que chaque entrée du dictionnaire correspond à une seule et unique unité lexicale et que les formes polysémiques sont donc automatiquement dédoublées. D’autre part, nous concevons le dictionnaire bilingue comme une paire de dictionnaires monolingues coordonnés (Blanco : 1999), c’est pourquoi les équivalents de traduction que nous offrons servent de pointeurs vers le module français, dans lequel les lemmes sont munis de leurs propres descriptions linguistiques.
35
Fuentes, Sandrine. "LA TRADUCTION DES NOMS DE PROFESSION DANS UN SYSTÈME DE DICTIONNAIRES ÉLECTRONIQUES COORDONNÉS (ES-FR)". Verbum 7, n. 7 (22 dicembre 2016): 66. http://dx.doi.org/10.15388/verb.2016.7.10287.
Abstract (sommario):
Dans cet article, nous nous attachons à la problématique posée par la traduction des noms de professions de l’espagnol vers le français et ce, dans une perspective de Traitement Automatique des Langues (TAL). Malgré la proximité linguistique des deux langues mises en regard, des obstacles d’ordre général comme la polysémie ou le figement et d’autres plus spécifiques comme le haut degré de technicité des termes concernés ou encore la structure interne complexe des syntagmes terminologiques peuvent entraver le processus de traduction automatique. C’est pourquoi il est nécessaire de fournir au système des descriptions linguistiques exhaustives, minutieuses et formalisées. C’est ce que nous proposons dans le dictionnaire électronique DicPro, où chaque lemme est associé à des champs lexicographiques de différents types (morphologique, sémantique, syntaxique, etc.) et ce, conformément au modèle de microstructure des dictionnaires électroniques conçus au sein du LDI (Université Paris 13). Il convient de souligner que chaque entrée du dictionnaire correspond à une seule et unique unité lexicale et que les formes polysémiques sont donc automatiquement dédoublées. D’autre part, nous concevons le dictionnaire bilingue comme une paire de dictionnaires monolingues coordonnés (Blanco : 1999), c’est pourquoi les équivalents de traduction que nous offrons servent de pointeurs vers le module français, dans lequel les lemmes sont munis de leurs propres descriptions linguistiques.
36
Kučerová, Ludmila, Martin Bystrianský e Josef Káňa. "The Effect of Isothermal Hold Temperature on Microstructure and Mechanical Properties of TRIP Steel". Solid State Phenomena 270 (novembre 2017): 253–57. http://dx.doi.org/10.4028/www.scientific.net/ssp.270.253.
Abstract (sommario):
TRIP (transformation induced plasticity) steels are low alloyed low carbon steels with complex microstructures consisting of ferrite, bainite and retained austenite. This complex microstructure provides them with excellent strength to ductility balance, making them a member of advanced high strength steels (AHSS) group. Suitable microstructure can be obtained by either heat or thermo-mechanical treatment. A hold in bainite transformation region is an integral part of any form of commercial TRIP steel processing route, as it enables formation of sufficient volume fraction of bainite and also stabilization of retained austenite in the final microstructure. Various bainitic hold temperatures ranging from 350 °C to 500 °C were tested within thermo-mechanical treatment of 0.2C-1.5Mn-0.6S-1.5Al steel and the final microstructures were evaluated with regard to the suitability to TRIP effect and achieved mechanical properties. The microstructures were analyzed by scanning electron microscopy and mechanical properties measured by tensile test.
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Fan, Y., W. Tian, Y. Guo, Z. Sun e J. Xu. "Relationships among the Microstructure, Mechanical Properties, and Fatigue Behavior in Thin Ti6Al4V". Advances in Materials Science and Engineering 2016 (2016): 1–9. http://dx.doi.org/10.1155/2016/7278267.
Abstract (sommario):
The microstructures of Ti6Al4V are complex and strongly affect its mechanical properties and fatigue behavior. This paper investigates the role of microstructure on mechanical and fatigue properties of thin-section Ti6Al4V sheets, with the aim of reviewing the effects of microstructure on fatigue properties where suboptimal microstructures might result following heat treatment of assemblies that may not be suited to further annealing, for example, following laser welding. Samples of Ti6Al4V sheet were subjected to a range of heat treatments, including annealing and water quenching from temperatures ranging from 650°C to 1050°C. Micrographs of these samples were inspected for microstructure, and hardness, 0.2% proof stress, elongation, and fracture strength were measured and attributed back to microstructure. Fractography was used to support the findings from microstructure and mechanical analyses. The strength ranking from high to low for the microstructures of thin Ti6Al4V sheets observed in this study is as follows: acicularα′martensite, Widmanstätten, bimodal, and equiaxed microstructure. The fatigue strength ranking from high to low is as follows: equiaxed, bimodal, Widmanstätten, and acicularα′martensite microstructure.
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Sakharova, Nataliya A., e José Valdemar Fernandes. "Dislocation Microstructure in Copper Multicrystals Deformed under the Sequences: Rolling - Tension and Tension - Rolling". Materials Science Forum 514-516 (maggio 2006): 589–93. http://dx.doi.org/10.4028/www.scientific.net/msf.514-516.589.
Abstract (sommario):
The microstructure evolution of copper multicrystalline sheets, undergoing plastic deformation in the sequences of strain paths rolling – tension and tension – rolling, was studied in the present work. For both sequences, two different types of change of strain path were studied: the tensile and rolling directions were parallel and normal to each other. Samples submitted to these four complex strain paths were investigated by transmission electron microscopy (TEM). TEM observations have shown the typical dislocations microstructures for the prestrain paths in tension and rolling. The dislocation microstructures observed during the second path were analysed and discussed as a function of the sequence and of the type of strain path change (parallel and normal sequential paths). Special microbands features were observed during the second path, for both sequences, rolling – tension and tension – rolling. The appearance of such microstructural features is discussed in terms of the sequence and type of strain path change and it is linked with the slip activity during the second deformation mode.
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Ramakrishna R, VSM, e JP Gautam. "Optimization of post weld heat treatment cycle of fiber laser welded bainitic steel". E3S Web of Conferences 184 (2020): 01039. http://dx.doi.org/10.1051/e3sconf/202018401039.
Abstract (sommario):
Automobile industry has always been in look out for advanced materials that would account for greater crash resistance, high fatigue strength, optimum ductility and longer service life despite heavy mechanical loads applied on these engine components. These critical requirements are met through maintaining the complex microstructures and optimum phase constituents. The retention of microstructural constituents has always been a key parameter while fabricating these advanced automobile materials by fusion welding process. Carbide free bainitic steels are emerging out to be the candidate materials for automobile applications. Owing to their microstructure consisting fine bainitic ferrite laths that are interwoven with retained austenite in their lath boundaries. The fine Bainitic laths provide enough strength and the retained austenite phase facilitates the desired ductility. The current paper critically discusses the microstructural and microhardness variation across the zones during Fiber Laser welding of bainitic steel sheets. Keeping the phase transformations during welding in view, post weld heat treatments were undertaken. The welded steel was austenitized at 820 OC, rapidly cooled to 390 OC, and soaked at different durations before furnace cooing. The microstructure variation and microhardness profiling were done at all these heat treatment conditions. Basing on the analyses, the heat treatment cycle has been optimized.
40
Malik, Affan, Danqi Qu e Hui-Chia Yu. "Smoothed Boundary Method Electrochemical Simulation Framework for Complex Electrode Microstructures". ECS Meeting Abstracts MA2022-01, n. 46 (7 luglio 2022): 1968. http://dx.doi.org/10.1149/ma2022-01461968mtgabs.
Abstract (sommario):
Battery and fuel cell electrodes possess highly complex microstructures: tortuous interparticle space, irregular particle surfaces, and various particle sizes. Additionally, coupled physical mechanisms, such as mass transport and electron transport, heat generation, and phase transformations, simultaneously occur during the electrode’s operations. All these combined complexity makes modeling electrochemical processes with explicit considerations of electrode microstructures very challenging. As such, electrode designs are still heavily relied on experimental trial-and-error methods even though modern computational resources have grown rapidly. Furthermore, experimental technologies have become very mature to reconstruct three-dimensional (3D) microstructures. The abundant microstructure data open a window for directly simulating the physical processes in complex microstructures. This talk will introduce an innovative simulation method using a continuous function to define complex microstructures. Since the irregular complex microstructure surfaces are implicitly described, this method no longer requires meshes conformal to the complex microstructures as in the conventional simulations. Thus, it allows us to simulate detailed electrochemical phenomena in complex electrode microstructures in an unprecedented pace with ease, especially for image-based, reconstructed microstructures. We will showcase several recent simulations to demonstrate the presented method, including phase transformations in porous graphite anode, hybrid electrodes, electrochemical impedance spectroscopy, and electrochemical processes in NMC-separator-graphite full-cell. The presented method is applicable to other electrochemical systems, and can be extended to include other physical mechanisms for further studying cycling-induced phenomena such as stress, heat, and Li-plating. Figure 1
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Chen, Ming, Xiaodong Hu, Hongyang Zhao e Dongying Ju. "Recrystallization Microstructure Prediction of a Hot-Rolled AZ31 Magnesium Alloy Sheet by Using the Cellular Automata Method". Mathematical Problems in Engineering 2019 (16 settembre 2019): 1–15. http://dx.doi.org/10.1155/2019/1484098.
Abstract (sommario):
A large reduction rolling process was used to obtain complete dynamic recrystallization (DRX) microstructures with fine recrystallization grains. Based on the hyperbolic sinusoidal equation that included an Arrhenius term, a constitutive model of flow stress was established for the unidirectional solidification sheet of AZ31 magnesium alloy. Furthermore, discretized by the cellular automata (CA) method, a real-time nucleation equation coupled flow stress was developed for the numerical simulation of the microstructural evolution during DRX. The stress and strain results of finite element analysis were inducted to CA simulation to bridge the macroscopic rolling process analysis with the microscopic DRX activities. Considering that the nucleation of recrystallization may occur at the grain and R-grain boundary, the DRX processes under different deformation conditions were simulated. The evolution of microstructure, percentages of DRX, and sizes of recrystallization grains were discussed in detail. Results of DRX simulation were compared with those from electron backscatter diffraction analysis, and the simulated microstructure was in good agreement with the actual pattern obtained using experiment analysis. The simulation technique provides a flexible way for predicting the morphological variations of DRX microstructure accompanied with plastic deformation on a hot-rolled sheet.
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Choudhury, Amitava, Snehanshu Pal, Ruchira Naskar e Amitava Basumallick. "Computer vision approach for phase identification from steel microstructure". Engineering Computations 36, n. 6 (8 luglio 2019): 1913–33. http://dx.doi.org/10.1108/ec-11-2018-0498.
Abstract (sommario):
PurposeThe purpose of this paper is to develop an automated phase segmentation model from complex microstructure. The mechanical and physical properties of metals and alloys are influenced by their microstructure, and therefore the investigation of microstructure is essential. Coexistence of random or sometimes patterned distribution of different microstructural features such as phase, grains and defects makes microstructure highly complex, and accordingly identification or recognition of individual phase, grains and defects within a microstructure is difficult.Design/methodology/approachIn this perspective, computer vision and image processing techniques are effective to help in understanding and proper interpretation of microscopic image. Microstructure-based image processing mainly focuses on image segmentation, boundary detection and grain size approximation. In this paper, a new approach is presented for automated phase segmentation from 2D microstructure images. The benefit of the proposed work is to identify dominated phase from complex microstructure images. The proposed model is trained and tested with 373 different ultra-high carbon steel (UHCS) microscopic images.FindingsIn this paper, Sobel and Watershed transformation algorithms are used for identification of dominating phases, and deep learning model has been used for identification of phase class from microstructural images.Originality/valueFor the first time, the authors have implemented edge detection followed by watershed segmentation and deep learning (convolutional neural network) to identify phases of UHCS microstructure.
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Cai, Wen Zhong, Shan Tung Tu, Yang Yan Zheng e Jian Ming Gong. "Microstructure Reconstruction and Numerical Simulation of Deformation in Particle-Reinforced Composites". Key Engineering Materials 353-358 (settembre 2007): 567–70. http://dx.doi.org/10.4028/www.scientific.net/kem.353-358.567.
Abstract (sommario):
A new methodology of computer simulation is proposed to perform finite element (FE) calculations of uniaxial tensile deformation on the three-dimensional (3D) complex microstructures, through its application to the microstructure of aluminum matrix containing randomly distributed and oriented SiC particles of highly variable and angular geometry. Compared with the simplified microstructure model, the complex microstructure model shows significant differences in terms of micromechanical fields and macroscopic uniaxial deformation. The results reveal that a quantitative and convenient reconstruction of microstructure of particulate composites is crucial for both the prediction and design of material properties.
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Zhao, Chang Song, Jun Yong Wu, Fan Zhong Chu, Kai Rui Zhao e Lei Yu. "Study on Preparation of Microstructured Optical Membrane". Key Engineering Materials 861 (settembre 2020): 159–64. http://dx.doi.org/10.4028/www.scientific.net/kem.861.159.
Abstract (sommario):
Micro-structured optical film is one of the micro-optical elements and has a great market demand. This article studies the microstructured optical film formed by UV imprinting: The influence of embossing pressure on microstructure replication accuracy was explored. The larger the pressure, the better the material filling. When the pressure is 5N, the microstructure replication is complete; The relationship between the radiation intensity and warpage deformation was explored, and the decrease in the intensity of the UV light source can effectively reduce the warpage deformation; The influence of the material formula on the optical properties of the product was explored. When the oligomer content was 55%, the film had a high light transmittance. At the same time, the prepared film was subjected to an apparent inspection with good microstructure replication accuracy.Microstructured optical elements are widely used in optical fields such as semiconductors, lasers, beam shaping [1-2] and solar energy [3-5] due to their unique advantages such as small size and high performance. As a key component in many industries, it has a high market demand rate. However, the microstructure forming process is complicated, the manufacturing cost is high, and the accuracy is difficult to guarantee, which has restricted its development. With the advancement of science and technology and the increase in market demand, more and more researchers and enterprises have put their eyes on the research of preparing micro-structured optical elements.At present, the commonly used microstructures are mainly icrolens array [6-8], and the processing methods include micro-imprinting [9-10], etching [11], electron beam direct writing, and micro-injection [12], etc. This article studies the UV-curing embossing process in micro-embossing. This processing method has the advantages of fast molding, high efficiency, and environmental protection. And this process is conducive to mass production and has a broad market application prospect.In this paper, the forming process and material formulation of microstructured optical film prepared by light-cured micro-imprinting were investigated, and the microstructure morphology of the preparation was analyzed apparently.
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Larzabal, Gorka, Nerea Isasti, J. M. Rodriguez-Ibabe, Isabel Gutiérrez e P. Uranga. "Effect of the Time between Last Deformation Pass and Accelerated Cooling on the Mechanical Properties in Nb and Nb-Mo Microalloyed Steels". Key Engineering Materials 716 (ottobre 2016): 281–90. http://dx.doi.org/10.4028/www.scientific.net/kem.716.281.
Abstract (sommario):
The microstructural refinement induced when the holding time between last deformation pass and accelerated cooling is reduced, affects the mechanical properties in low carbon Nb and Nb-Mo microalloyed steels. Plane strain compression tests were performed and mechanical property samples machined in order to quantify this effect using tensile and Charpy impact tests. A complete microstructural characterization was carried out using electron backscattered diffraction (EBSD) measuring unit size distributions and homogeneity of complex microstructures. The synergetic combination of Nb and Mo elements modifies the final microstructures and, therefore, affects the contribution of different strengthening mechanisms, such as substructure, precipitation hardening and dislocation density. Even though strength is not clearly affected by the reduction of the holding time after the last deformation pass, Charpy properties are considerably improved in the case of the Nb steel. The presence of MA islands in the Nb-Mo steel limits the beneficial effect of the microstructural refinement and toughness remains unmodified.
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da Silva, Elisabete Pinto, Wei Xu, Cecilia Föjer, Yvan Houbaert, Jilt Sietsma e Roumen H. Petrov. "Combined Martensite and Bainite Formation from Austenite Decomposition in HSLA Steel". Advanced Materials Research 922 (maggio 2014): 682–87. http://dx.doi.org/10.4028/www.scientific.net/amr.922.682.
Abstract (sommario):
Recent studies have shown the possibility to induce time-dependent phase transformations during isothermal treatment between the martensite start (MS)temperature and martensite finish(Mf,)temperature, i.e. after initial martensite formation. Such treatments result in specific complex microstructures consisting of bainite, martensite and retained austenite, depending on the holding temperature and time. However, the nature of the isothermal transformations belowMSis not completely understood and issues like isothermal formation of martensite and bainite formation are still under discussion. The purpose of this study is to investigate the phase transformations from austenite, subsequent to initial martensite formation, during isothermal treatments at different temperatures of HSLA steel. The microstructure development was monitored by means of dilatometry and microstructural characterization of the transformation products by Optical Microscopy, Scanning Electron Microscope, Electron Backscatter Diffraction and X-ray diffraction. The phase transformations and complex competition and interactions between the different transformation mechanisms are discussed.
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Yang, Zenan, Yong Li, Xiaolu Wei, Xu Wang e Chenchong Wang. "Martensite Start Temperature Prediction through a Deep Learning Strategy Using Both Microstructure Images and Composition Data". Materials 16, n. 3 (18 gennaio 2023): 932. http://dx.doi.org/10.3390/ma16030932.
Abstract (sommario):
In recent decades, various previous research has established empirical formulae or thermodynamic models for martensite start temperature (Ms) prediction. However, most of this research has mainly considered the effect of composition and ignored complex microstructural factors, such as morphology, that significantly affect Ms. The main limitation is that most microstructures cannot be digitized into numerical data. In order to solve this problem, a convolutional neural network model that can use both composition information and microstructure images as input was established for Ms prediction in a medium-Mn steel system in this research. Firstly, the database was established through experimenting. Then, the model was built and trained with the database. Finally, the performance of the model was systematically evaluated based on comparison with other, traditional AI models. It was proven that the new model provided in this research is more rational and accurate because it considers both composition and microstructural factors. In addition, because of the use of microstructure images for data augmentation, the deep learning had a low risk of overfitting. When the deep-learning strategy is used to deal with data that contains both numerical and image data types, obtaining the value matrix that contains interaction information of both numerical and image data through data preprocessing is probably a better approach than direct linking of the numerical data vector to the fully connected layer.
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Gao, Junjie, Daiying Deng, Haitao Han e Jijun Yu. "Microstructure Evolution and Multiscale Heat Transfer Characteristics of Resin-Based Ablative Material under Aerodynamic Heating". International Journal of Aerospace Engineering 2023 (16 ottobre 2023): 1–21. http://dx.doi.org/10.1155/2023/9069416.
Abstract (sommario):
This paper is aimed at investigating the microstructure evolution of resin-based ablative materials under aerodynamic heating. The microstructure, morphology, material density, and thermophysical parameters at different positions of the material after aerodynamic heating were deeply studied. The changes in the microstructural characteristics of materials caused by complex reaction processes were investigated, including microstructural morphology, porosity, the overlap relationship between microstructural components, and the mutual positional relationship. The relationship between microstructural evolution and material heat transfer is discussed. By analyzing the heat transfer mechanism and heat transfer path of the microstructure, combing with the analysis results of the evolution of the microstructure and the physical properties of the material, multiscale heat transfer unit cell models were established to predict the equivalent thermal conductivity. Thereby, the evolution of physical properties and microstructure of resin-based ablative materials under aerodynamic heating and the relationship between microstructure evolution and heat transfer process are obtained. It can improve the accuracy of ablative heat transfer simulation. In addition, it can provide reference for the process design of ablative materials and promote the application and development of ablative materials in the field of aircraft.
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Demirörs, Ahmet Faik, Diana Courty, Rafael Libanori e André R. Studart. "Periodically microstructured composite films made by electric- and magnetic-directed colloidal assembly". Proceedings of the National Academy of Sciences 113, n. 17 (11 aprile 2016): 4623–28. http://dx.doi.org/10.1073/pnas.1524736113.
Abstract (sommario):
Living organisms often combine soft and hard anisotropic building blocks to fabricate composite materials with complex microstructures and outstanding mechanical properties. An optimum design and assembly of the anisotropic components reinforces the material in specific directions and sites to best accommodate multidirectional external loads. Here, we fabricate composite films with periodic modulation of the soft–hard microstructure by simultaneously using electric and magnetic fields. We exploit forefront directed-assembly approaches to realize highly demanded material microstructural designs and showcase a unique example of how one can bridge colloidal sciences and composite technology to fabricate next-generation advanced structural materials. In the proof-of-concept experiments, electric fields are used to dictate the position of the anisotropic particles through dielectrophoresis, whereas a rotating magnetic field is used to control the orientation of the particles. By using such unprecedented control over the colloidal assembly process, we managed to fabricate ordered composite microstructures with up to 2.3-fold enhancement in wear resistance and unusual site-specific hardness that can be locally modulated by a factor of up to 2.5.
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Mustafa, Faisal, Mehmet Egilmez, Wael Abuzaid e Sami El-Khatib. "Effect of Heat Treatments on Microstructure and Mechanical Properties of Fe-Mn-Ni-Al-Gd Shape Memory Alloy". Journal of Physics: Conference Series 2751, n. 1 (1 aprile 2024): 012009. http://dx.doi.org/10.1088/1742-6596/2751/1/012009.
Abstract (sommario):
Abstract There are significant scientific and industrial efforts to develop and optimize Iron-based shape memory alloys (SMA) such as FeMnNiAl for cost-sensitive applications. This alloy system shows shape memory and superelastic properties across a large temperature range. However, many studies have pointed out the need for rather complex thermo-mechanical treatments for the optimization of the SMA properties. In addition, works considering the effects of alloying on the development of microstructures that are more conducive to pseudo-elasticity in this system remain limited. Hence, systematic studies aiming at the investigation of the microstructural evolution of the FeMnNiAl(Gd) system are of great interest. In this study, solution heat treatment is done to tune the microstructure for optimum mechanical properties. The effect of phase distribution on mechanical properties is investigated at different heat treatments. Whereas cyclic heat treatment induced abnormal grain growth (AGG) in all samples, so large grains were obtained. The phase variation and elemental composition are analyzed by X-ray diffraction and Energy Dispersive Spectroscopy, respectively. The microstructure and phase distribution are observed using Scanning Electron Microscope and then related to the microhardness results. The microstructure has a good correlation with mechanical properties where the fine distribution of phases results in a higher hardness number.