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1
Herbster, Maria, Karsten Harnisch, Paulina Kriegel, et al. "Microstructural Modification of TiAl6V4 Alloy to Avoid Detrimental Effects Due to Selective In Vivo Crevice Corrosion." Materials 15, no. 16 (2022): 5733. http://dx.doi.org/10.3390/ma15165733.
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TiAl6V4 wrought alloy is a standard material used for endoprostheses due to its ideal characteristics in terms of osseointegration. However, the insufficient wear and crevice corrosion resistance of TiAl6V4 are limiting factors that can cause clinical problems. Therefore, the objective of this study was to analyze and identify suitable phases and microstructural states of TiAl6V4 alloy with advantageous implant properties by thermal treatments. By varying the temperature and cooling rate, four heat treatment strategies were derived that produced different microstructural states that differed in morphology, arrangement and proportions of phases present. All TiAl6V4 modifications were characterized regarding their microstructure, mechanical, corrosive and tribological properties, as well as cell adhesion. The acicular, martensitic microstructure achieves a significant hardness increase by up to 63% and exhibits improved corrosion and wear resistance compared to the forged condition. Whereas the modified microstructures showed similar electrochemical properties in polarization tests using different electrolytes (PBS with H2O2 and HCl additives), selective α or β phase dissolution occurred under severe inflammatory crevice conditions after four weeks of exposure at 37 °C. The microstructurally selective corrosion processes resemble the damage patterns of retrieved Ti-based implants and provide a better understanding of clinically relevant in vivo crevice corrosion mechanisms. Furthermore, a microstructural effect on cell attachment was determined and is correlated to the size of the vanadium-rich β phase. These key findings highlight the relevance of an adapted processing of TiAl6V4 alloy to increase the longevity of implants.
2
Zeng, Qiu Lian, Zhong Guang Wang, and J. K. Shang. "Microstructural Effects on Low Cycle Fatigue of Sn-3.8Ag-0.7Cu Pb-Free Solder." Key Engineering Materials 345-346 (August 2007): 239–42. http://dx.doi.org/10.4028/www.scientific.net/kem.345-346.239.
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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.
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Griffiths, Malcolm. "Microstructural Effects on Irradiation Creep of Reactor Core Materials." Materials 16, no. 6 (2023): 2287. http://dx.doi.org/10.3390/ma16062287.
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The processes that control irradiation creep are dependent on the temperature and the rate of production of freely migrating point defects, affecting both the microstructure and the mechanisms of mass transport. Because of the experimental difficulties in studying irradiation creep, many different hypothetical models have been developed that either favour a dislocation slip or a mass transport mechanism. Irradiation creep mechanisms and models that are dependent on the microstructure, which are either fully or partially mechanistic in nature, are described and discussed in terms of their ability to account for the in-reactor creep behaviour of various nuclear reactor core materials. A rate theory model for creep of Zr-2.5Nb pressure tubing in CANDU reactors incorporating the as-fabricated microstructure has been developed that gives good agreement with measurements for tubes manufactured by different fabrication routes having very different microstructures. One can therefore conclude that for Zr-alloys at temperatures < 300 °C and stresses < 150 MPa, diffusional mass transport is the dominant creep mechanism. The most important microstructural parameter controlling irradiation creep for these conditions is the grain structure. Austenitic alloys follow similar microstructural dependencies as Zr-alloys, but up to higher temperature and stress ranges. The exception is that dislocation slip is dominant in austenitic alloys at temperatures < 100 °C because there are few barriers to dislocation slip at these low temperatures, which is linked to the enhanced recombination of irradiation-induced point defects.
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Agboola, Joseph, Emmanuel Anyoku, and 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, no. 1 (2021): 43–49. http://dx.doi.org/10.26776/ijemm.06.01.2021.04.
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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.
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Akbari, G. H., H. Abbaszadeh, and H. Ghotbi Ravandi. "Effects of Al, Si and Mn on the Recrystallization Behaviors of Fe Containing 70B Brass." Materials Science Forum 558-559 (October 2007): 107–11. http://dx.doi.org/10.4028/www.scientific.net/msf.558-559.107.
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The effects of alloying elements and impurities on the microstructure and properties of metals and alloys are important. Understanding of these effects may help to control and produce products with desired properties at lower cost. In the present work the effects of Al, Si and Mn on the recrystallization behavior, hardness and microstructural changes of an Fe- containing brass during annealing were studied. The results show that alloying elements strongly affect recrystallization kinetics and resulted finer microstructures. Hardness variations during annealing are consistent with microstructural observations and the presence of alloying elements. All elements slow down recrystallization progress and increase resulted hardness values. The resulted microstructures in the presence of alloying elements are much finer than that of plain 70B brass. It was concluded that the present alloying elements affect the recrystallization behavior of 70B brass in a similar manner. Their mechanism of interactions is solute drag effect and their effects sum up when they present together.
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Zhong, Ning, Songpu Yang, Tao Liu, et al. "Effects of Compositional Inhomogeneity on the Microstructures and Mechanical Properties of a Low Carbon Steel Processed by Quenching-Partitioning-Tempering Treatment." Crystals 13, no. 1 (2022): 23. http://dx.doi.org/10.3390/cryst13010023.
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Quenching-partitioning-tempering (Q-P-T) heat treatment is a relatively novel approach to attain excellent ductility in high-strength steels. In the present work, the microstructural evolution and the mechanical properties of a low carbon microalloyed advanced steel were systematically investigated after the Q-P-T process. The microstructural evolution was explored by employing X-ray diffraction, transmission electron microscopy and scanning electron microscopy. The results indicate that the multiphase microstructures strongly depend on both the initial microstructure and the processing parameters of the quenching and partitioning process, especially the quenching temperature. Compositional inhomogeneity during the Q-P-T process results in multiphase microstructures, in which the mechanical properties of the quenching and partitioning steels may be strongly impacted by the distribution of heterogeneous austenite phase in the steel matrix.
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Regone, Wiliam, and 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, no. 4 (2004): 303–11. http://dx.doi.org/10.1590/s0370-44672004000400014.
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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.
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Hu, Zhitao, Xin Wang, Yuzhou Du, et al. "Effects of graphite nodule count on microstructural homogeneity of austempered ductile iron (ADI)." Metallurgical Research & Technology 120, no. 2 (2023): 217. http://dx.doi.org/10.1051/metal/2023031.
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The microstructural homogeneity of austempered ductile iron (ADI) with different graphite counts was evaluated by microstructural observations and hardness measurement. ADI was composed of spheroidal graphite, ausferrite, and stabilized austenite. Microstructural observation and microhardness evaluation indicated that graphite nodule counts affected the microstructure significantly, in a sense that the microstructure was more homogeneous for samples with higher graphite counts. More graphite nodules provided more positions for ferrite nucleation and gave rise to a fine ausferrite microstructure. However, for samples with fewer graphite nodules, the diffusion of carbon atoms in austenite far away from graphite was inhibited, which stabilized the austenite and gave rise to the existence of large-size blocky austenite. Consequently, ADI with high graphite nodule count exhibited superior ductility. This study suggested that more graphite nodule is preferred in ADI to obtain a more homogeneous microstructure.
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Yang, Hongyue, Ji Qian, Ming Yang, Chunxi Li, Hengfan Li, and Songling Wang. "Study on the Effects of Microstructural Surfaces on the Attachment of Moving Microbes." Energies 13, no. 17 (2020): 4421. http://dx.doi.org/10.3390/en13174421.
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The research of marine antifouling is mainly conducted from the aspects of chemistry, physics, and biology. In the present work, the movement model of microorganisms along or against the flow direction on the microstructural surface was established. The model of globose algae with a diameter of 5 μm in the near-wall area was simulated by computational fluid dynamics (CFD), and the fluid kinematic characteristics and shear stress distribution over different-sized microstructures and in micropits were compared. Simulation results revealed that the increase of the β value (height to width ratio) was prone to cause vortexes in micropits. In addition, the closer the low-velocity region of the vortex center to the microstructural surface, the more easily the upper fluid of the microstructure slipped in the vortex flow and reduced the microbial attachment. Moreover, the shear stress in the micropit with a height and width of 2 μm was significantly higher than those in others; thus, microbes in this micropit easily fell off.
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Snopiński, Przemysław, Krzysztof Matus, Ondřej Hilšer, and Stanislav Rusz. "Effects of Built Direction and Deformation Temperature on the Grain Refinement of 3D Printed AlSi10Mg Alloy Processed by Equal Channel Angular Pressing (ECAP)." Materials 16, no. 12 (2023): 4288. http://dx.doi.org/10.3390/ma16124288.
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In this work, we used an AlSi10Mg alloy produced by selective laser melting (SLM) to study the effects of build direction and deformation temperature on the grain refinement process. Two different build orientations of 0° and 90° and deformation temperatures of 150 °C and 200 °C were selected to study this effect. Light microscopy, electron backscatter diffraction and transmission electron microscopy were used to investigate the microtexture and microstructural evolution of the laser powder bed fusion (LPBF) billets. Grain boundary maps showed that the proportion of low-angle grain boundaries (LAGBs) dominated in every analysed sample. It was also found that different thermal histories caused by the change in build direction resulted in microstructures with different grain sizes. In addition, EBSD maps revealed heterogeneous microstructures comprising equiaxed fine-grained zones with ≈0.6 μm grain size and coarse-grained zones with ≈10 μm grain size. From the detailed microstructural observations, it was found that the formation of a heterogeneous microstructure is closely related to the increased fraction of melt pool borders. The results presented in this article confirm that the build direction has a significant influence on the microstructure evolution during the ECAP process.
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Li, Hui, Zhanglong Zhao, Yongquan Ning, Hongzhen Guo та Zekun Yao. "Characterization of Microstructural Evolution for a Near-α Titanium Alloy with Different Initial Lamellar Microstructures". Metals 8, № 12 (2018): 1045. http://dx.doi.org/10.3390/met8121045.
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The effects of initial lamellar thickness on microstructural evolution and deformation behaviors of a near-α Ti-5.4Al-3.7Sn-3.3Zr-0.5Mo-0.4Si alloy were investigated during isothermal compression in α + β phase field. Special attention was paid to microstructural conversion mechanisms for α lamellae with different initial thicknesses. The deformation behaviors, including flow stress, temperature sensitivity, and strain rate sensitivity, and processing maps and their dependence on initial lamellar thickness were discussed. The detailed microstructural characterizations in different domains of the developed processing maps were analyzed. The results showed that the peak efficiency of power dissipation decreased with increasing initial lamellar thickness. The interaction effects with different extents of globularization, elongating, kinking, and phase transformation of lamellar α accounted for the variation in power dissipation. The flow instability region appeared to expand more widely for thicker initial lamellar microstructures during high strain rate deformation due to flow localization and local lamellae kinking. The electron backscatter diffraction (EBSD) analyses revealed that the collaborative mechanism of continuous dynamic recrystallization (CDRX) and discontinuous dynamic recrystallization (DDRX) promoted the rapid globularization behavior for the thinnest acicular initial microstructure, whereas in case of the initial thick lamellar microstructure, CDRX leading to the fragmentation of lamellae was the dominant mechanism throughout the deformation process.
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Ding, Qingqing, Hongbin Bei, Xinbao Zhao, Yanfei Gao, and Ze Zhang. "Processing, Microstructures and Mechanical Properties of a Ni-Based Single Crystal Superalloy." Crystals 10, no. 7 (2020): 572. http://dx.doi.org/10.3390/cryst10070572.
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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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Yang, Yo Sep, S. Y. Park, Hyun Jo Jun, Chan Gyung Park, S. H. Lim, and D. Y. Ban. "Effects of Microstructure on the Fatigue Resistance of Steel Tire Cords." Materials Science Forum 475-479 (January 2005): 4125–28. http://dx.doi.org/10.4028/www.scientific.net/msf.475-479.4125.
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Effects of microstructural parameters on fatigue resistance (σFL) of the steel tire cords have been investigated experimentally from microscopic points of view. At first, microstructural parameters depending on carbon content have been identified by using transmission electron microscopy (TEM). The fatigue resistance of the steel tire cords depending on carbon content has been measured by using the Hunter rotating beam tester under the bending stress of 900 to 1500 MPa. The fatigue resistance was improved with increasing the carbon content from 0.7, 0.8 to 0.9 wt. % C, due to variations of microstructural parameters, such as lamellar spacing (λp), cementite thickness (tc), and volume fraction (Vc) of cementite. As the carbon content increased, the lamellar spacing and the cementite thickness decreased, while the volume fraction of cementites increased. The effects of microstructure on fatigue resistance have been discussed in terms of the microstructural parameters mentioned above.
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Lannutti, J. J. "Characterization and Control of Compact Microstructure." MRS Bulletin 22, no. 12 (1997): 38–44. http://dx.doi.org/10.1557/s0883769400034734.
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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.
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Murr, L. E. "Microstructure-property hypermaps for shock-loaded materials." Proceedings, annual meeting, Electron Microscopy Society of America 44 (August 1986): 416–19. http://dx.doi.org/10.1017/s0424820100143675.
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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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Habibi, Niloufar, Santhosh Mathi, Thorsten Beier, Markus Könemann, and Sebastian Münstermann. "Effects of Microstructural Properties on Damage Evolution and Edge Crack Sensitivity of DP1000 Steels." Crystals 12, no. 6 (2022): 845. http://dx.doi.org/10.3390/cryst12060845.
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In the present work, the microstructural damage behavior of two DP1000 steel test subjects through various stress states was studied to thoroughly learn the interaction between microstructure, damage evolution, and edge stretchability. In addition, microstructural changes at the fracture sites and fracture surfaces were observed using a scanning electron microscope. The distinctive mechanical and damage behaviors of the materials were revealed. However, the steels were slightly different in chemical composition, microstructural characteristics, and yield stress. The results showed that when microstructural and mechanical properties of phases were more similar, i.e., the microstructure was more homogenous, the damage was initiated by cracking at ferrite-martensite interfaces, and it propagated along the loading direction. This allowed the material to represent high local formability and significant necking. In contrast, by increasing the dissimilarity between ferrite and martensite phases, damage propagated by the shear linking of the voids hindered local deformation of the material and led it to sudden fracture after negligible necking. These distinct damage evolutions noticeably influenced the materials’ edge stretchability. Since higher local formability favors the edges with higher resistance to cracking, the hole expansion ratio increases, as clearly observed throughout the current study.
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Bang, Kook Soo, Woo Yeol Kim, Chan Park, Young Ho Ahn, and Jong Bong Lee. "Effects of Nitrogen on Weld Metal Microstructure and Toughness in Submerged Arc Welding." Materials Science Forum 539-543 (March 2007): 3906–11. http://dx.doi.org/10.4028/www.scientific.net/msf.539-543.3906.
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The effects of nitrogen content on weld metal impact toughness in submerged arc welding were investigated and interpreted in terms of microstructural changes and solid solution hardening. The weld metal impact toughness in as-welded condition decreased with increasing nitrogen content from 110 to 200 ppm. The weld metal microstructure changed with increasing nitrogen content; ferrite with second phase increased at the expense of tough acicular ferrite. In addition to microstructural changes, the microhardness of acicular ferrite increased gradually with the nitrogen content. Therefore, the loss of impact toughness can be attributed to a combination of the effects of microstructural changes and solid solution hardening.
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Gariboldi, Elisabetta, and Marco Colombo. "Characterization of Innovative Al-Si-Mg-Based Alloys for High Temperature Applications." Key Engineering Materials 710 (September 2016): 53–58. http://dx.doi.org/10.4028/www.scientific.net/kem.710.53.
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The role played by transition elements and rare earths, added in small quantities (fractions of unity in weight percent) was proved by several authors to be beneficial for the age-hardening response and for the microstructural stability at high temperature of Al-based alloys. The paper illustrates the results of an experimental investigation on the effects of erbium (Er) additions on the microstructural features, microstructural stability and mechanical properties of an Al-7Si-0.4Mg alloy of wide industrial use. The effects are multifold: in the cast microstructure, a silicon (Si) eutectic modification was observed with the formation of several Er-containing intermetallic phases. After solution treatment and aging, an increase in peak hardness and an enhanced microstructural stability were obtained. In this preliminary study, the beneficial effects of Er additions were confirmed.
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Mohrbacher, Hardy, Jer-Ren Yang, Yu-Wen Chen, Johannes Rehrl, and Thomas Hebesberger. "Metallurgical Effects of Niobium in Dual Phase Steel." Metals 10, no. 4 (2020): 504. http://dx.doi.org/10.3390/met10040504.
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Dual phase (DP) steels are widely applied in today’s automotive body design. The favorable combination of strength and ductility in such steels is in first place related to the share of ferrite and martensite. The pronounced work hardening behavior prevents localized thinning and allows excellent stretch forming. Niobium microalloying was originally introduced to dual phase steel for improving bendability by refining the microstructure. More recently developed “high ductility” (HD) DP steel variants provide increased drawability aided by a small share of austenite retained in the microstructure. In this variant niobium microalloying produces grain refinement and produces a dispersion of nanometer-sized carbide precipitates in the steel matrix which additionally contributes to strength. This study investigates the microstructural evolution and progress of niobium precipitation during industrial processing of high-ductility DP 980. The observations are interpreted considering the solubility and precipitation kinetics of niobium. The influences of niobium on microstructural characteristics and its contributions to strength and formability are discussed.
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Rodriguez vargas, Bryan ramiro, Luciano Albini, Giulia Tiracorrendo, Riccardo Massi, Giulia Stornelli, and Andrea Di Schino. "EFFECT OF ULTRAFAST HEATING ON AISI 304 AUSTENITIC STAINLESS STEEL." Acta Metallurgica Slovaca 29, no. 2 (2023): 104–7. http://dx.doi.org/10.36547/ams.29.2.1833.
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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.
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Widener, Christian A., Dwight A. Burford, and Sarah Jurak. "Effects of Tool Design and Friction Stir Welding Parameters on Weld Morphology in Aluminum Alloys." Materials Science Forum 638-642 (January 2010): 1261–66. http://dx.doi.org/10.4028/www.scientific.net/msf.638-642.1261.
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Friction stir welding (FSW) is a complex thermo-mechanical process which produces wrought microstructure with microstructural gradients in grain size, grain orientation, dislocation density, and precipitate distribution. The type and degree of microstructural modification is a function of the particular alloy chosen, its initial temper, the tool design and corresponding weld process parameter window, and other variables like material thickness, size, fixturing, etc. Since the microstructural changes produced can dramatically affect resultant mechanical performance and corrosion response, a thorough understanding of the variables involved in those changes is needed. A design of experiments approach was used to study the effects of welding parameter selection on the microstructural changes wrought by FSW with two different sizes of the same FSW tool design. A combination of microhardness mapping and electrical conductivity testing was used to investigate potential differences. The importance of these factors and the means for characterizing them for developing standards and specifications are also discussed.
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Stewart, Peter S., Stephen H. Davis, and Sascha Hilgenfeldt. "Microstructural effects in aqueous foam fracture." Journal of Fluid Mechanics 785 (November 23, 2015): 425–61. http://dx.doi.org/10.1017/jfm.2015.636.
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We examine the fracture of a quasi-two-dimensional surfactant-laden aqueous foam under an applied driving pressure, using a network modelling approach developed for metallic foams by Stewart & Davis (J. Rheol., vol. 56, 2012, p. 543). In agreement with experiments, we observe two distinct mechanisms of failure analogous to those observed in a crystalline solid: a slow ductile mode when the driving pressure is applied slowly, where the void propagates as bubbles interchange neighbours through the T1 process; and a rapid brittle mode for faster application of pressures, where the void advances by successive rupture of liquid films driven by Rayleigh–Taylor instability. The simulations allow detailed insight into the mechanics of the fracturing medium and the role of its microstructure. In particular, we examine the stress distribution around the crack tip and investigate how brittle fracture localizes into a single line of breakages. We also confirm that pre-existing microstructural defects can alter the course of fracture.
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Mishnaevsky, Leon. "Computational Analysis of the Effects of Microstructures on Damage and Fracture in Heterogeneous Materials." Key Engineering Materials 306-308 (March 2006): 489–94. http://dx.doi.org/10.4028/www.scientific.net/kem.306-308.489.
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3D FE (finite element) simulations of the deformation and damage evolution of particle reinforced composites are carried out for different microstructures of the composites. Several new methods and programs for the automatic reconstruction of 3D microstructures of composites on the basis of the geometrical description of microstructures as well as on the basis of the voxel array data have been developed and tested. Different methods of reconstruction and generation of finite element models of 3D microstructures of composite materials (geometry-based and voxel array based) are discussed and compared. It was shown that FE analyses of the elasto-plastic deformation and damage of composite materials using the microstructural models of materials generated with these methods yield very close results. Numerical testing of composites with random, regular, clustered and gradient arrangements of spherical particles is carried out. The fraction of failed particles and the tensile stress-strain curves were determined numerically for each of the microstructures. It was found that the rate of damage growth as well as the critical applied strain, at which the damage growth in particles begins, depend on the particle arrangement, and increase in the following order: gradient < random < regular < clustered microstructure.
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Li, Jing Yuan, and Xiao Lei Du. "Effects of Microstructural Morphology on Mechanical Properties of Magnesium Alloys." Materials Science Forum 686 (June 2011): 113–19. http://dx.doi.org/10.4028/www.scientific.net/msf.686.113.
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The mechanical property of magnesium alloy depends on the alloy elements and microstructure strongly. The multiple dependency relations are studied by investigating magnesium alloys with different Al and Zn contents. The semi-continuous casting billets exhibit quite different microstructural morphologies between the centre and edge of the cross section. The centre shows fine and uniform microstructure while the edge is coarse and reticular. However the difference is almost eliminated when the billets were homogenized at 380°C for 15h. The generation mechanism of casting microstructure is also discussed in this paper. The results show that the morphology of second phase and the size of grain have greater effect on the mechanical properties than the element Zn. The alloys with uniform, fine and non-dendrite microstructure exhibit both high strength and elongation when Al content is about 6% and Zn content is various from 0 to 3%. In contrast, the strength increases and elongation decreases significantly as Al content increases from 0 to 6%.
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Ferreira-Palma, Carlos, Héctor J. Dorantes-Rosales, Víctor M. López-Hirata, and Alberto A. Torres-Castillo. "Effect of Ag additions on the microstructure and phase transformations of Zn-22Al-2Cu (wt.%) alloy." International Journal of Materials Research 112, no. 2 (2021): 108–17. http://dx.doi.org/10.1515/ijmr-2020-8009.
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Abstract The relationship between microstructure and mechanical properties is studied for eutectoid Zn-22Al (wt.%) alloys modified with Cu and Ag. Three alloys with a Cu content of 2 wt.% and varying amounts of Ag were cast and hot-extruded. Different microstructural characteristics were induced by heat treatments: natural aging, artificial aging and furnace cooling. Structural and microstructural characterizations were carried out with X-ray diffraction and scanning electron microscopy. Mechanical properties were determined by tensile testing. Dilatometry was used for determining the effects of composition on the transformation points. The addition of Ag increased the ε phase fraction and provided solid solution strengthening, improving the mechanical strength and reducing ductility. Ag additions also displaced the eutectoid reaction to higher temperatures. The microstructure of the matrix has proven to have a strong impact on mechanical properties. The naturally aged specimens presented the highest ductility and tensile strength; however, these properties are severely affected by aging. Lamellar microstructures present the lowest ductility and values of tensile strength between those of the natural and artificially-aged specimens.
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Boutin, C. "Microstructural effects in elastic composites." International Journal of Solids and Structures 33, no. 7 (1996): 1023–51. http://dx.doi.org/10.1016/0020-7683(95)00089-5.
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Haddour, Lillia, Mourad Keddam, and Nadir Mesrati. "Relationships between Microstructure and Mechanical Properties of Polycristalline Alumina." Applied Mechanics and Materials 625 (September 2014): 192–95. http://dx.doi.org/10.4028/www.scientific.net/amm.625.192.
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Some low purity alumina ceramics with an alumina content ranging from 86% to 93% were investigated, in order to explore the effects of microstructural parameters (grain size, intergranular phase) on mechanical (wear) and dielectrical parameters. The microstructure and worn surfaces were analysed using scaning electron microscopy. The correlation between microstructural, dielectrical properties and wear is discussed. It has been proposed that mechanical and electrical properties are two aspects of the same fundamental mechanism. Key words: Al2O3, Microstructure final, Wear resistance, Breakdown.
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Vander Voort, George Frederic, Beatriz Suárez-Peña, and Juan Asensio-Lozano. "Metallographic Assessment of Al-12Si High-Pressure Die Casting Escalator Steps." Microscopy and Microanalysis 20, no. 5 (2014): 1486–93. http://dx.doi.org/10.1017/s143192761400172x.
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AbstractA microstructural characterization study was performed on high-pressure die cast specimens extracted from escalator steps manufactured from an Al-12 wt.% Si alloy designed for structural applications. Black and white, color light optical imaging and scanning electron microscopy techniques were used to conduct the microstructural analysis. Most regions in the samples studied contained globular-rosette primary α-Al grains surrounded by an Al-Si eutectic aggregate, while primary dendritic α-Al grains were present in the surface layer. This dendritic microstructure was observed in the regions where the melt did not impinge directly on the die surface during cavity filling. Consequently, microstructures in the surface layer were nonuniform. Utilizing physical metallurgy principles, these results were analyzed in terms of the applied pressure and filling velocity during high-pressure die casting. The effects of these parameters on solidification at different locations of the casting are discussed.
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Mikulla, Christoph, Lars Steinberg, Philipp Niemeyer, Uwe Schulz, and Ravisankar Naraparaju. "Microstructure Refinement of EB-PVD Gadolinium Zirconate Thermal Barrier Coatings to Improve Their CMAS Resistance." Coatings 13, no. 5 (2023): 905. http://dx.doi.org/10.3390/coatings13050905.
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Rare-earth zirconates are proven to be very effective in restricting the CMAS attack against thermal barrier coatings (TBCs) by forming quick crystalline reaction products that seal the porosity against infiltration. The microstructural effects on the efficacy of Electron Beam-Physical Vapor Deposition gadolinium zirconate (EB-PVD GZO) against CMAS attack are explored in this study. Four distinct GZO microstructures were manufactured and the response of two selected GZO variants to different CMAS and volcanic ash melts was studied for annealing times between 10 min and 50 h at 1250 °C. A significant variation in the microstructural characteristics was achieved by altering substrate temperature and rotation speed. A refined microstructure with smaller intercolumnar gaps and long feather arms lowered the CMAS infiltration by 56%–72%. Garnet phase, which formed as a continuous layer on top of apatite and fluorite, is identified as a beneficial reaction product that improves the CMAS resistance.
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Lin, Yu-Ju, Che-Hua Yang, and Jiunn-Yuan Huang. "Influence of Microstructural Changes’ Effects on the Linear and Nonlinear Ultrasonic Parameters of Cast Stainless Steels." Applied Sciences 10, no. 10 (2020): 3476. http://dx.doi.org/10.3390/app10103476.
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In this research, some nondestructive ultrasonic techniques were employed to inquire into the effect of microstructural changes induced by thermal aging and cold work on the ultrasonic response. As thermal embrittlement is a risk to the safety of nuclear power plants, a nondestructive detection method has to be developed for on-site monitoring. The austenitic stainless steel with δ-ferrite specimens were used to study the behavior of microstructural changes caused by age-treating and cold work and then examined by the velocity, attenuation, and nonlinear ultrasonic technique. The variations of the linear and the nonlinear ultrasonic parameters were related to the microstructural changes. Additionally, the experimental results suggest that the ultrasonic nonlinearity parameter of cast stainless steel is determined by the microstructure evolution caused by spinodal decomposition and the phase precipitation process.
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Kaijalainen, A., N. Vähäkuopus, M. Somani, S. Mehtonen, D. Porter, and J. Kömi. "The Effects of Finish Rolling Temperature and Niobium Microalloying on the Microstructure and Properties of a Direct Quenched High-Strength Steel." Archives of Metallurgy and Materials 62, no. 2 (2017): 619–26. http://dx.doi.org/10.1515/amm-2017-0091.
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AbstractThis paper comprehends the effects of finish rolling temperature (FRT) and Nb-microalloying on the microstructural evolution and resultant properties of a low carbon direct quenched steel in the yield strength category of ≥900 MPa. Results indicate that a decrease in FRT close to Ar3temperature significantly influenced the microstructure following phase transformation, especially at the subsurface (~50-400 μm) of the rolled strip. On decreasing the FRT, the subsurface microstructure revealed a fine mixture of ferrite and bainite obviously as a result of strain-induced transformation, whereas the structure at the centreline remained essentially martensitic. Further, Nb-microalloying promoted the formation of ferrite and bainite even at higher FRTs, thus influencing the mechanical properties. The microstructures of the hot-rolled strips were further corroborated with the aid of CCT diagrams.
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Rezvanian, O., M. A. Zikry, and A. M. Rajendran. "Statistically stored, geometrically necessary and grain boundary dislocation densities: microstructural representation and modelling." Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 463, no. 2087 (2007): 2833–53. http://dx.doi.org/10.1098/rspa.2007.0020.
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A unified physically based microstructural representation of f.c.c. crystalline materials has been developed and implemented to investigate the microstructural behaviour of f.c.c. crystalline aggregates under inelastic deformations. The proposed framework is based on coupling a multiple-slip crystal plasticity formulation to three distinct dislocation densities, which pertain to statistically stored dislocations (SSDs), geometrically necessary dislocations (GNDs) and grain boundary dislocations. This interrelated dislocation density formulation is then coupled to a specialized finite element framework to study the evolving heterogeneous microstructure and the localized phenomena that can contribute to failure initiation as a function of inelastic crystalline deformation. The GND densities are used to understand where crystallographic, non-crystallographic and cellular microstructures form and the nature of their dislocation composition. The SSD densities are formulated to represent dislocation cell microstructures to obtain predictions related to the inhomogeneous distribution of SSDs. The effects of the lattice misorientations at the grain boundaries (GBs) have been included by accounting for the densities of the misfit dislocations at the GBs that accommodate these misorientations. By directly accounting for the misfit dislocations, the strength of the boundary regions can be more accurately represented to account for phenomena associated with the effects of the GB strength on intergranular deformation heterogeneities, stress localization and the nucleation of failure surfaces at critical regions, such as triple junctions.
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Xiaoyu, Jiang, and Kong Xiangan. "Computer Simulation of 3-D Random Distribution of Short Fibers in Metal Matrix Composite Materials." Journal of Engineering Materials and Technology 121, no. 3 (1999): 386–92. http://dx.doi.org/10.1115/1.2812391.
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In this paper, the microstructure of “Saffil”-Al2O3 short fiber reinforced Al-Mg5.5 metal matrix composite material is simulated by computer. In the simulation it is taken into account of that the lengths, diameters, orientations, and locations of short fibers, etc. For the 3-D randomly distributed short fibers in composite materials, the typical distributions of short fiber microstructures on different planes are obtained for different short fiber volume fractions. The microstructural effects of average fiber length, diameter and their standard deviations on the overall strength of metal matrix composite materials are analyzed. From the short fiber microstructural distribution in metal matrix composite materials, the short fiber diameter coefficient ξd and short fiber length coefficient ξ1 are obtained for different standard deviations σd and σl, respectively. The short fiber orientation coefficient ξa is obtained, also. The results of these coefficients may be useful to the manufacture and use of short fiber reinforced composite materials. Considering these coefficients ξa ξd and ξl, the improved formula is given for the direct calculation of overall strength of short fibers reinforced composite materials. The improved formula may reflect the microstructural characteristics of short fibers reinforced composite materials.
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Wakai, Eiichi, Shuhei Nogami, Akira Hasegawa, et al. "Effects of Helium Production and Displacement Damage on Microstructural Evolution and Mechanical Properties in Helium-Implanted Austenitic Stainless Steel and Ferritic/Martensitic Steel." Materials Science Forum 1024 (March 2021): 53–69. http://dx.doi.org/10.4028/www.scientific.net/msf.1024.53.
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The effects of helium concentration and displacement damage on microstructural evolution at low dpa and low helium concentration were mainly investigated in specimens of austenitic stainless steel 316FR or SUS304 and a high chromium martensitic steel (HCM12A). The 316FR and HCM12A specimens were implanted uniformly with helium at 823 K up to 30 appm-He or 50 appm-He by 50 MeV cyclotron accelerator using energy degraders. After the helium implantation, the microstructures were examined by a transmission electron microscopy and positron annihilation lifetime measurements. Irradiation hardening behaviors were analyzed using SUS304 and HCM12A steels at 823 K implanted with He ion up to 100 appm with different He/dpa ratios in the HIT ion irradiation experiments and the hardening behaviors were examined by nano indentation method. In the irradiation and annealing specimens, these mechanical properties and microstructures were examined to understand the effects of helium production, displacement damage and annealing on microstructural development, and kinetic Monte Carlo (kMC) simulations were also performed to understand the microstructural development, and the results were compared with the results of TEM observation and positron annihilation lifetime measurements. Important some differences in the microstructural developments such as cavity formation and growth between austenitic stainless steel and martensitic steel were observed in low dpa and low helium concentration conditions.
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Bertolino, G., N. Bilger, and J. Crépin. "Modeling microstructures and microstructural effects on macroscopic and intragranular mechanical behavior." Computational Materials Science 40, no. 3 (2007): 408–16. http://dx.doi.org/10.1016/j.commatsci.2007.01.009.
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Tian, Qu, Jennifer Schrack, Bennett Landman, Amal Wanigatunga, Susan Resnick, and Luigi Ferrucci. "Relative Vigorous-Intensity Physical Activity Predicts Brain Microstructural Changes in Older Adults." Innovation in Aging 5, Supplement_1 (2021): 443. http://dx.doi.org/10.1093/geroni/igab046.1720.
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Abstract Physical activity especially at moderate-to-vigorous intensity may preserve brain structure in old age. However, current findings are cross-sectional and rely on absolute intensity. This study aimed to examine whether relative or absolute vigorous-intensity physical activity (VPA) predicts brain microstructural changes. We analyzed 260 initially cognitively normal and well-functioning participants(age=70.5yrs) who had VPA data via ActiHeart and longitudinal brain microstructure by DTI(follow-up=3.7yrs). Associations of VPA with microstructural changes were examined using linear mixed-effects models, adjusted for demographics. Each SD higher relative VPA defined by heart rate reserve (i.e. 21 min/day) was significantly associated with less decline in memory-related microstructural integrity, including mean diffusivity of entorhinal cortex and parahippocampal gyrus and fractional anisotropy of uncinate fasciculus and cingulum-hippocampal part, and not executive/motor-related microstructure. Absolute VPA was not associated with microstructural markers. Among well-functioning older adults, participating in VPA defined by heart rate reserve may predict less brain microstructural decline in memory-related areas.
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Lopes, Eder S. N., Alessandra Cremasco, Rodrigo Contieri, and Rubens Caram. "Effects of Aging Heat Treatment on the Microstructure of Ti-Nb and Ti-Nb-Sn Alloys Employed as Biomaterials." Advanced Materials Research 324 (August 2011): 61–64. http://dx.doi.org/10.4028/www.scientific.net/amr.324.61.
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The mechanical behavior of β titanium alloys applied as orthopedic biomaterials depends directly on their microstructural features, and can be improved by tailoring the microstructure through the control of their phase transformations. The aim of this investigation is to discuss phase transformations during the aging heat treatment of β Ti-30Nb and β Ti-30Nb-2Sn alloys and to correlate microstructure and mechanical behavior. The results of high temperature XRD experiments showed decomposition of orthorhombic α” phase, followed by the precipitation of ω and α phases. The mechanical behavior of Ti-Nb and Ti-Nb-Sn alloys was found to be highly sensitive to the microstructural changes caused by the addition of Sn and by heat treatments.
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Ostad Shabani, Mohsen, Amir Baghani, Mohammad Reza Rahimipour, Mansour Razavi, Mohammad Zakeri, and Fatemeh Heydari. "Effect of temperature, time, and shear force on the morphology and size of dendrites in A356-Al2O3 composites." Journal of Composite Materials 56, no. 2 (2021): 329–38. http://dx.doi.org/10.1177/00219983211052602.
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Dendrite arm spacing (DAS) plays a vital role in determining mechanical properties of aluminum casting composites. In this study, the effects of three different methods of gravity sand casting, squeeze casting, and semi-solid compo-casting with different electromagnetic stirring currents and times on the microstructural morphology of A356-Al2O3 composites were investigated. In order to investigate effects of shear forces on the formation of the globular-like structure, samples with different stirring electric current and times were produced by compo-casting in semi-solid state and analyzed. Optical emission microscopy was used to study the microstructure and DAS of nanocomposites. Quantitative analysis of microstructure was performed by utilizing an image analysis system. In this study, the optimum temperature for composite fabrication for this type of composite was calculated to obtain the most appropriate morphology and size of the microstructure. Also, the appropriate time to keep this composite at this temperature was obtained, and finally the relevant microstructures were fully discussed.
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Farh, Hichem, Hanna Belghit, Toufik Ziar, Abdelouahab Noua, and Fares Serradj. "The Cold Rolling Effects on the Microstructure and Micro-Hardness of Al-Mg-Si Alloy." Diffusion Foundations 18 (September 2018): 14–18. http://dx.doi.org/10.4028/www.scientific.net/df.18.14.
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Rolling is a very common technique for shaping sheet metal. It aims to reduce the thickness of a metal sample to adapt it to the usual conditions of use in the industry. Nevertheless, this technique is not without modifying the mechanical and microstructural properties of the materials that can influence the mechanical strength of shaped parts. The purpose of the present investigation is to study the changes in microstructures and micro-hardness of Al-Mg-Si alloy with different rolling reduction in thickness and following artificial aging treatments at 175° C . We notice that the micro-hardness increases with the increasing of the deformation level . Reduction in thickness shows a change in microstructure and texture. Characterization methods used in this work is: Optical Microscopy (OM) and, Vickers microhardness.
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Topping, Troy D., Ying Li, Enrique J. Lavernia, K. Manigandan, and T. S. Srivatsan. "The Influence of Processing on Microstructural Development, Tensile Response and Fracture Behavior of Aluminum Alloy 5083." Advanced Materials Research 410 (November 2011): 175–86. http://dx.doi.org/10.4028/www.scientific.net/amr.410.175.
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In this paper, the specific influence of quasi-isostatic forging and rolling of cryomilled powder on microstructural development and resultant tensile deformation and fracture behavior of aluminum alloy 5083 is highlighted and comparison made with the coarse grained counterpart. The specific influence and contribution of strain hardening to enhancing strength of the ultra-fine grain microstructure of the aluminum alloy is presented and discussed. It is shown that the capability of the ultra fine grain microstructure to recover strength through the mechanism of work hardening is quite similar to the conventionally processed counterpart. The influence and role of intrinsic microstructural features in governing tensile deformation and fracture behavior is elaborated upon. The viable microscopic mechanisms governing final fracture behavior is discussed in light of the competing and mutually interactive influences of nature of loading, intrinsic microstructural effects, and deformation kinetics. Key Words: aluminum alloy 5083, processing, microstructure, tensile properties, fracture
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Shekhar, Shashank, S. Abolghashem, S. Basu, J. Cai, and M. Ravi Shankar. "Interactive Effects of Strain, Strain-Rate and Temperatures on Microstructure Evolution in High Rate Severe Plastic Deformation." Materials Science Forum 702-703 (December 2011): 139–42. http://dx.doi.org/10.4028/www.scientific.net/msf.702-703.139.
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During high rate severe plastic deformation (HRSPD), strain and strain-rate are not the only external factors that determine microstructural transformations in materials, temperature-rise due to heat generation from deformation processes, also plays an important role. Temperature may influence the microstructure directly by controlling grain growth kinetics and it may also have an indirect effect through the interactive effect on material behavior, which in turn, influences strain and strain-rate parameters. This complex thermomechanics of HRSPD can lead to myriad of microstructure and consequently, material properties and phenomenon. These deformation parameters can be utilized as a ‘fingerprint’ for the resulting microstructure, and the properties and phenomenon related to it. Here, we capture some of these microstructural transformations by relating grain and sub-grain sizes, to the deformation parameters. In doing so, we find evidence of continuous dynamic recrystallization operative under these HRSPD conditions, where the interplay of strain, strain rate and temperatures offer varying degrees of multimodality in the grain-size distributions.
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Çalışkan, Salim, and Rıza Gürbüz. "Heat treatment effects on near threshold region for AISI 4340 steels." Materials Testing 65, no. 4 (2023): 536–44. http://dx.doi.org/10.1515/mt-2022-0405.
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Abstract The microstructure effect is critical in the near-threshold region in terms of fatigue crack propagation. Despite numerous studies on the crack growth phenomenon in the literature, there is still no comprehensive understanding of the mechanism behind it. The fatigue crack growth mechanism occurs in the plastic zone region, which is quite small in size; the order is regarded as microstructural units, particularly at low stress intensities. Microstructural differences caused by heat treatment methods are frequently attributed to changes in monotonic and yield strength, resulting in differences in plastic zone size. The driving force required for crack growth under alternating loading is proportional to the plastic zone size ahead of the crack tip. When the microstructure is modified using isothermal transformations, the stress intensity near the threshold and corresponding crack propagation rates were found to be affected by stress ratio, material yield strength, particle size distribution, and impurity segregation. The crack growth threshold ΔK 0 is discovered to be inversely related to steel strength, and a relationship between ΔK 0 and cyclic yield stress is established. In the scope of this paper, annealed and tempered conditions were investigated to assess near threshold behavior for AISI 4340 steel. Effect of microstructure will be detailed around low stress intensities via performed crack growth tests.
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Kim, Won Yong, Han Sol Kim, and Sung Hwan Lim. "Effects of Oxygen on Phase Stability and Mechanical Properties of Quenched Ti-Nb Alloys." Solid State Phenomena 124-126 (June 2007): 1377–80. http://dx.doi.org/10.4028/www.scientific.net/ssp.124-126.1377.
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The effects of oxygen content on microstructures, elastic modulus and tensile properties of quenched Ti-Nb alloys were investigated in order to design a desirable Ti based alloy through casting process. From the microstructural and phase analysis, it is evidently revealed that the volume fraction of β phase increased with increasing content of oxygen, and the occurrence of intermediate ω phase was suppressed in metastable β Ti-Nb based alloys. Martensite transformation temperature decreased with increasing content of oxygen. Therefore, it is suggested that oxygen acts to stabilize β phase rather than α stabilizer in quenched state. Yield strength increased with increasing content of oxygen without a large consumption of ductility in metastable β Ti-Nb based alloys. The variation of mechanical property was explained by the phase stability, phase formation and microstructure in correlation with oxygen and Nb content.
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Clasen, Antje, and Antonia B. Kesel. "Microstructural Surface Properties of Drifting Seeds—A Model for Non-Toxic Antifouling Solutions." Biomimetics 4, no. 2 (2019): 37. http://dx.doi.org/10.3390/biomimetics4020037.
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A major challenge in the shipping and marine industry is the biofouling on under water surfaces. So far, biocides have been the main remedy for the prevention of the adhesion of microorganisms that is also influenced by surface topography. In recent years, research projects have explored microstructured surfaces as a non-toxic antifouling strategy. In this study, physical factors of surfaces of seeds of 43 plant species were analyzed with regards to their antifouling effects. After exposure to cold water of the North Sea during the swarming periods of the barnacles larvae, the surface microstructures of seeds without fouling of barnacles were identified and compared with each other, using a scanning electron microscope (SEM). In order to validate the findings, selected microstructured surface structure properties were transferred to technical surfaces with a 2-component silicon system and subjected to the same conditions. The results of the analyses confirmed that drifting seeds with specific microstructural surface structure properties promote biofouling defense of epibionts. These results serve as a starting point for the development of non-toxic antifouling agents based on the interaction of microstructures and geometric shapes.
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Eliezer, Dan, E. Tal-Gutelmacher, and Lothar Wagner. "High Fugacity Hydrogen Effects in Beta-21S Titanium Alloy." Materials Science Forum 546-549 (May 2007): 1355–60. http://dx.doi.org/10.4028/www.scientific.net/msf.546-549.1355.
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Beta-21S titanium alloy is ranked among the most important advanced materials for a variety of technological applications, due to its combination of a high strength/weight ratio, good corrosion behavior and oxidation resistance. However, in many of these technological applications, this alloy is exposed to environments which can act as sources of hydrogen, and consequently, severe problems may arise. The objective of this paper is to investigate the influence of high fugacity hydrogen on Beta-21S alloy in as-received (mill-annealed and hot-rolled) condition. Hydrogen effects on the microstructure are studied using X-ray diffraction and electron microscopy, while the absorption and desorption characteristics are determined respectively by means of a hydrogen determinator and thermal desorption spectroscopy. Preliminary results at room temperature revealed hydrogen-induced straining and expansion of the lattice parameters. However, neither second phases formation (hydrides), nor hydrogen-induced cracking, were observed after hydrogenation. The main characteristics of hydrogen absorption/desorption behavior, as well as hydrogen-induced microstructural changes in both microstructures are discussed in detail.
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Calisti, V., A. Lebée, A. A. Novotny, and J. Sokolowski. "Sensitivity of the Second Order Homogenized Elasticity Tensor to Topological Microstructural Changes." Journal of Elasticity 144, no. 2 (2021): 141–67. http://dx.doi.org/10.1007/s10659-021-09836-6.
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AbstractThe multiscale elasticity model of solids with singular geometrical perturbations of microstructure is considered for the purposes, e.g., of optimum design. The homogenized linear elasticity tensors of first and second orders are considered in the framework of periodic Sobolev spaces. In particular, the sensitivity analysis of second order homogenized elasticity tensor to topological microstructural changes is performed. The derivation of the proposed sensitivities relies on the concept of topological derivative applied within a multiscale constitutive model. The microstructure is topologically perturbed by the nucleation of a small circular inclusion that allows for deriving the sensitivity in its closed form with the help of appropriate adjoint states. The resulting topological derivative is given by a sixth order tensor field over the microstructural domain, which measures how the second order homogenized elasticity tensor changes when a small circular inclusion is introduced at the microscopic level. As a result, the topological derivatives of functionals for multiscale models can be obtained and used in numerical methods of shape and topology optimization of microstructures, including synthesis and optimal design of metamaterials by taking into account the second order mechanical effects. The analysis is performed in two spatial dimensions however the results are valid in three spatial dimensions as well.
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Anghelina, Florina Violeta, Vasile Bratu, Elena Valentina Stoian, and Ileana Nicoleta Popescu. "Microstructural Investigation of Aluminum Alloys Type "2024" for the Aviation Industry." Advanced Materials Research 1114 (July 2015): 62–67. http://dx.doi.org/10.4028/www.scientific.net/amr.1114.62.
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This paper presents experimental results revealed on the samples type 2024 aluminum alloy used in aeronautics. The results of microstructural and compositional investigations presented in this paper were performed on samples taken from 2024 Al alloy samples produced by ALRO Slatina. The main objective of the investigation is the conformity assessment of alloys in terms of chemical composition with the specifications type of aviation [SAE AMS 47N, EN 515, etc]. It also aims microstructural conformity assessment in terms of the grain and the hardening effects by natural or artificial aging applied by the manufacturer. Adequate characterization of 2024 aluminum alloys type was achieved by combined investigations: (i) Wet Chemical Analysis, (ii) Spectrochemical Analysis and (iii) Electron Microscopy. The main conclusion that emerges from the investigations carried out on aluminum samples revealed that: (a) alloys fits in terms of composition with the standard specification for 2024, in all cases; (b) microstructure vary in fineness of grain, but meets the requirements of aviation rules; the investigated microstructures have been appreciated as adequate of aluminum alloys type "2024".
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Jurči, Peter, Jana Ptačinová, Martin Sahul, Mária Dománková, and Ivo Dlouhy. "Metallurgical principles of microstructure formation in sub-zero treated cold-work tool steels – a review." Matériaux & Techniques 106, no. 1 (2018): 104. http://dx.doi.org/10.1051/mattech/2018022.
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The beneficial influence of a sub-zero treatment on wear resistant tools and components has been known for over 100 years. On the other hand, the basic metallurgical principles being responsible for enhanced hardness and wear performance, changes in the tempering response and toughness and improved dimensional stability have become known only over the past decade. The sub-zero treatment has, thus, been changed from an art to accepted science. The topic of the current conference paper is the latest theory explaining the metallurgical background for this kind of treatment. This theory states that it is the low-temperature isothermal martensitic transformation that induces secondary microstructural effects, such as an accelerated precipitation rate for transient carbides, formation of very small globular carbides and overall refinement of the microstructure. Consequently, secondary microstructural effects have a clear impact on the most relevant properties. The extent of the improvement or deterioration of these properties may be a result of competitive microstructural effects.
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Mossaab, Blaoui Mohammed, Mokhtar Zemri, and Mustapha Arab. "Effect of medium carbon steel microstructure on tensile strength and fatigue crack growth." International Journal of Structural Integrity 10, no. 1 (2019): 67–75. http://dx.doi.org/10.1108/ijsi-05-2018-0030.
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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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Regier, R. W., A. Reguly, David K. Matlock, J. K. Choi, and John G. Speer. "Effects of Austenite Conditioning and Transformation Temperature on the Bainitic Microstructure in Linepipe Steels." Materials Science Forum 783-786 (May 2014): 85–90. http://dx.doi.org/10.4028/www.scientific.net/msf.783-786.85.
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Low carbon bainitic steels are important in applications such as linepipe, and the details of the bainite microstructure control strength and toughness. The transformation of austenite to bainitic ferrite has been widely researched over the years, although recent use of electron backscatter diffraction techniques has provided opportunity to advance the characterization of various crystallographic aspects. In recent work, microstructures were characterized in a base steel containing 0.04 C and 1.7 Mn (wt. pct.) and two additional steels having modest carbon and manganese variations to influence the transformation behavior, with an interest in the MA (martensite-austenite) constituent and characteristics of the bainite developed at different transformation temperatures. Effects of austenite conditioning were also examined, as these steels contained an addition of 0.04 wt. pct. Nb. Microstructural details including crystallographic characteristics assessed using EBSD are presented, along with comments related to the implications of the results.