Search

The article explores the impact of cast part size on the microstructure and mechanical properties of bainitic High-Carbon and High-Silicon Cast Steel. The study focuses on the segregation phenomena in high-silicon cast steels and the influence of varying casting thicknesses on bainitic transformation and mechanical properties. The research findings suggest that microsegregation patterns significantly affect phase transformations during heat treatments, but the mechanical properties remain comparable between different cast sample thicknesses. The study highlights the potential advantages of using high-silicon cast steels with bainitic microstructures in various industries due to their uniform mechanical behavior across different thicknesses. [Extracted from the article]

In this study, the laser surface melting of cobalt-based superalloy ECY768, which has been in service for 40,000 h at a temperature of 1000 °C, has been investigated. Subsequently, laser surface welding and post-welding heat treatment is performed on the samples. This study was conducted in order to restore the microstructure of the damaged service-aged gas turbine nozzle to as-cast state. The results showed that by performing laser surface remelting, the microstructure of as-cast state can be approached. Also, the results of this study have investigated the weldability, microsegregation and solidification path of this superalloy, and it can be used in the repairing this superalloy in the industry. Laser surface melting was performed using a continuous wave fiber laser at various speeds of 10, 12, 14, 20, 50, and 70 mm/s. The microstructure and phase characteristics of the samples were examined using optical and scanning electron microscopes. Upon analyzing the macrostructure of the weld metal, it was observed that the depth of the melt zone at the speed of 12 mm/s is 585 ± 40 μm. In the investigating the microstructure of the solidification modes, namely planar, cellular, columnar dendritic, and equiaxed dendritic, it was observed that microsegregation occurs during laser welding of the samples due to the presence of heavy elements such as tantalum and tungsten. The solidification distribution coefficient for tantalum was calculated to be 0.37, which increased to 0.60 after the solution annealing heat treatment, resulting in an improved segregation behavior. Characterizing the surface hardness profiles of laser-melted samples it was observed that the hardness in the melt zone significantly increased compared to the base metal. The results of the current research indicate that the weldability (resistance to various welding defects, especially hot cracks) of the cobalt-based superalloy ECY768 is acceptable, and this process can be used for rejuvenating service-aged ECY768 cobalt-based gas turbine nozzle.

Large TiN inclusions in nickel-based superalloys promote micropore formation, compromising the mechanical properties of the alloys. However, current research lacks a comprehensive coupled model that considers both solute element microsegregation and TiN precipitation specifically in nickel-based superalloys. This study investigated TiN precipitation during the solidification of IN718 alloys through a combined thermodynamic and kinetic approach. A modified Clyne–Kurz model was applied to account for multi-element microsegregation, enabling an integrated analysis of both microsegregation and precipitation processes. The results indicated that solute elements in the molten alloy segregated to varying degrees during solidification. At an initial nitrogen concentration of 25 ppm, TiN inclusions precipitated when the solid fraction reached 0.256, eventually resulting in a total TiN precipitation of 64 ppm by the end of solidification, while residual nitrogen in the liquid phase decreased to 1.3 ppm. Increasing the initial nitrogen concentration from 10 ppm to 40 ppm advanced the onset of TiN precipitation and raised the total amount from 16 ppm to 126 ppm. Further analysis indicated that cooling rates of 0.03 °C/s, 0.06 °C/s, and 0.18 °C/s did not significantly affect the final TiN accumulation. [ABSTRACT FROM AUTHOR]

By regulating Inconel718‐xRene88DT (x = 0–100%) alloy powder, microstructure evolution and microsegregation of as‐deposited samples fabricated by direct energy deposition (DED) are investigated. The novelty of this approach lies in the systematic regulation of the alloy composition to study its impact on microstructure and microsegregation, which is an important prerequisite to improving the performance of DED superalloys. It is found that the as‐deposited microstructure mainly consists of predominant γ columnar dendrites directionally growing along the deposition direction. With the increase of Rene88DT proportion, thelayered structure tends to be more obvious, and the amount and size of γ′ phase increases. The content of the Laves phase is in decline. As a result of the microsegregation, the needlelike δ (Ni3Nb) and lath‐shaped η (Ni3Ti) precipitate in the interdendritic regions when the proportion of Rene88DT is above 60%. The various microstructures, microsegregation, and their correlations at different proportions of Rene88DT DED samples are discussed. The relationship between composition and microstructure evolution is investigated based on the alloying mechanism, which can guide alloy design and process optimization for enhanced properties in AM‐built Ni‐based superalloys. [ABSTRACT FROM AUTHOR]

In order to gain insight into the unique characteristics of manufacturing large-scale products with intricate geometries, experimental nozzle-shaped samples were created using wire-feed electron beam additive technology. Bimetal samples were fabricated from nickel-based alloy and copper. Two distinct approaches were employed, utilizing varying substrate thicknesses and differing fabrication parameters. The two approaches were the subject of analysis and comparison through the examination of the surface morphology of the samples using optical microscopy, scanning electron microscopy, and X-ray diffraction analysis. It has been demonstrated that the variation in heat flux distributions resulting from varying the substrate thicknesses gives rise to the development of disparate angles of grain boundary orientation relative to the substrate. Furthermore, it is demonstrated that suboptimal choice of the fabrication parameters results in large disparities in the crystallization times, both at the level of sample as a whole and within the same material volume. For example, for the sample manufacturing by Mode I, the macrostructure of the layers is distinguished by the presence of non-uniformity in their geometric dimensions and the presence of unmelted wire fragments. In order to characterize the experimental nozzle-shaped samples, microhardness was measured, uniaxial tensile tests were performed, and thermal diffusivity was determined. The microhardness profiles and the mechanical properties exhibit a higher degree of strength than those observed in pure copper samples and a lower degree of strength than those observed in Inconel 625 samples obtained through the same methodology. The thermal diffusivity values of the samples are sufficiently close to one another and align with the properties of the corresponding materials in their state after casting or rolling. The data discussed above indicate that Mode II yields the optimal mechanical properties of the sample due to the high cooling rate, which influences the structural and phase state of the resulting products. It was thus concluded that the experimental samples grown by Mode II on a thinner substrate exhibited the best formability. [ABSTRACT FROM AUTHOR]

In this study, we simulated the solidification behavior, microsegregation, and heat treatment in Fe–xMn–7.5Al–5Cr–1.0C lightweight steels using the CALculation of PHAse Diagrams method. The solidification paths and microsegregation of these steels were calculated with the Scheil-Gulliver model and equilibrium calculator in the Thermo-Calc® software. At the same time, thermodynamic calculations predicted heat-treatment temperatures for different steels. The transformation path of the Fe–xMn–7.5Al–5Cr–1.0C (x = 18 and 20 wt.%) lightweight steels is as following: liquid → liquid + δ-ferrite → δ-ferrite + γ-austenite → γ-austenite → γ-austenite + M7C3, according to equilibrium and Scheil's calculations. In case of 25 wt.% Mn steel, the two-phase region of δ-ferrite and γ-austenite is absent in the transition path. The segregation behaviour of solute elements in the liquid, ferrite, and austenite phases were predicted using the Scheil model. The heat treatment temperature for single-phase formation is expected to be between 900 °C and 1030 °C. [ABSTRACT FROM AUTHOR]

The central segregation of elements in continuous casting slab is an important factor affecting the properties of steel materials. S segregation exists in the form of MnS. It is found in production practice that despite the ultra-low sulfur content of [ S ] ≤ 10 ppm in steel, MnS will still precipitate if the central segregation of slab is not well controlled, and MnS is an important factor causing the unqualified flaw detection of high-grade thick plate products. There are few studies on the microsegregation of ultra-low sulfur steel continuous casting slab. In this paper, the microsegregation model of continuous casting slab is established, and the effect of phase transformation on element segregation is fully considered. The precipitation behavior of MnS and the microsegregation of S, P, C, and Mn elements during slab solidification are discussed. Taking X pipeline steel as the research object, the simulation calculation shows that the segregation degree of P, S, and C is higher than that of Mn. When the solid fraction fs is greater than 0.9, the inflection point of S segregation decreases and MnS is formed. The segregation ratios of P, S, and C (CL / C0) after complete solidification were 4.5, 4.1, and 5.5, respectively. The carbon content affects the degree of element segregation by affecting the local solidification time. With the increase of carbon content, the degree of element segregation at the end of liquid steel solidification decreases. [ABSTRACT FROM AUTHOR]

There are several ways of theorizing the process of segregation. From a geographical perspective the spatiality is one of the most decisive component of the term. There are two types of spatial segregation; the horizontal residential segregation, which can be considered as default understanding of segregation. This is a more frequently researched and generally known type. The less researched vertical residential segregation applies a three-dimensional approach to the process and implies, that segregation can evolve through the upward expansion of the city. It has a long history, however it has been overshadowed by the transport-development led urban sprawl, suburbanisation and deurbanisation in the 20th century. In addition, the Chicago School's study about urban models have contributed to the rapid development of the theory and research of horizontal residential segregation. According to the avai lable literature, the 2000's brought a change in the research on vertical residential segregation across Europe, however no focused research has been carried out in Hungary so far. In this study the theory of vertical residential segregation is presented through literature review. Based on the literature three types of vertical residential segregation was identified as the theoretical framework of the paper. Three sample areas in Szeged, Hungary were selected based on the three different forms and archetypes of vertical segregation. To confirm the theoretical framework of the existence of the three archetype of vertical segregation an online housing market survey was made on properties offered for sale in 2020 to examine the supply side of the real estate market. To research the demand side, data on apartments sold between 2015 and 2019 were processed and analysed. Based on these, correlation between floor and price, size was analysed to set residential segregation trends for each type on the sample areas, and regression analysis between the location of the property within the building and the average price. Results show that vertical residential segregation can be observed in Szeged. The location of the properties within a building influence where certain social groups move to. A correlation between the average unit price of the property and the floors can be detected, but the co-movement of the two variables is at most moderately related according to social science interpretations. With the data on the real estate market, we have succeeded in revealing the vertical form of residential segregation. In the future more research with social indicators will be necessary to complement the research of the authors to get a more accurate picture of the micro-scale segregation process within buildings. [ABSTRACT FROM AUTHOR]

Carbon-free nickel alloy maraging steel has high demand in manufacturing aerospace vehicles and hypersonic missiles. Due to the absence of carbon and the strengthening of intermetallic precipitates, maraging steel can attain high strength and toughness with ductility. This material has enormous weldability in both annealed and post-weld heat-treated (PWHT) conditions. During high-thickness sections, the heat flow rate and the number of passes were found to be redundant. The existence of reverted austenite (RA) has been identified because prolonged aging also has an impact on the mechanical characteristics of the weldment. The present research demonstrates the characterization of plasma arc welded (PAW) maraging steel MDN 250 in welded and PWHT conditions. The weldments were subjected to three types of heat treatment, namely, (i) Subsequent Aging (TA), (ii) Solution treating + Subsequent Aging (STA), and (iii) Homogenizing + Solution treating + Subsequent Aging (HTA). This study also emphasizes the importance of precipitates and RA in affecting the strength and toughness of welded joints. The HTA treatment solely helps to eliminate the RA from the weldment. The microstructural study depicts the formation of reverted austenite in the TA condition. The reverted austenite has not been found in the microstructure under HTA conditions. The EBSD (Electron backscatter diffraction) analysis has resulted that the RA has been eliminated. The EDS (Electron Dispersive Spectroscopy) analysis shows that segregation of the enriched alloys has been effectively lowered in HTA condition. Compared to the other weldments' mechanical characterization, the HTA condition gives supremacy results. The average ultimate tensile strength of 1830 MPa has been achieved in HTA condition, with a yield strength of 1809 MPa. The average fracture toughness results of 88.3 MPa√ m was obtained in HTA condition. The work display of PAW (Plasma Arc Welding) is capable of meeting all of the requirements for welding maraging steel in high-thickness sections. [ABSTRACT FROM AUTHOR]

Precipitation strengthening is a crucial method for enhancing the mechanical properties of steel. The bridgman directional solidification furnace, optical microscope (OM), scanning electron microscope (SEM), electron probe analyzer (EPMA) and transmission electron microscope (TEM) were used to investigate the effect of solidification cooling rate on the solidification microstructure, microsegregation, and nanoprecipitates in medium carbon CrMo cast steel. The results indicate that as the cooling rate increases, the solidification microstructure is significantly refined. The relationship between the cooling rate (CA) and primary dendrite arm spacing (PDAS, λ1) and secondary dendrite arm spacing (SDAS, λ2) are given by λ1 = 123.74 × C-0.4088A, λ2 = 66.63 × C-0.6532 A. Solute elements like Cr, Mo, and V exhibit noticeable positive segregation in the inter-dendritic. When the cooling rate does not exceed 0.47 °C/s, the solute concentrations in the inter-dendritic increase with higher cooling rate, leading to a decrease in the effective solute partition coefficient. This phenomenon is primarily attributed to the back diffusion of solute elements during solidification. Following heat treatment, precipitation of M6C, V(C,N), and M23C6 occurs within the inter-dendritic regions. If the solidification cooling rate does not exceed 0.47 °C/s, the density and volume fraction of nanoprecipitates increase with higher cooling rate. This trend primarily results from the reduction in critical nucleation radius and critical nucleation energy, facilitating easier nucleation of nanoprecipitates.

Residual δ-ferrite is ubiquitous in M50NiL bearing steel and seriously deteriorates impact toughness. In the present work, the formation mechanism of δ-ferrite in M50NiL steel and the influence of element segregation on its formation process were investigated. The residual δ-ferrite was proved to form directly from the final liquid phase at the end of solidification due to serious segregation of Mo and V elements. Calculation results indicate that the segregation of Mo and V elements expanded the “L + δ'' two-phase region and stabilized δ-ferrite. Due to the high concentration of Mo and V, large-sized V-rich MC and Mo-rich M2C carbides would precipitate in δ-ferrite at 900–1200 °C if the cooling rate is slow. When kept at 1200 °C for no more than 30 min, Mo and V elements derived from the decomposition of large-sized carbides are preferentially diffused into δ-ferrite, enhancing the stability of δ-ferrite. To achieve the effective elimination of δ-ferrite in M50NiL steel, it is necessary to keep the ingot at 1200 °C for at least 20 h.

In this research, dissimilar welding of the nickel-based superalloy Inconel 59 and austenitic stainless steel AISI 904L steel was successfully done with double-pulsed gas metal arc welding (DP-GMAW) using the filler ERNiCrMo-13. Macroscopic analysis showed a defect-free weld with an aspect ratio of 2.4, attributed to the efficient heat delivery (0.642 kJ/mm) in DP-GMAW. The microstructure of the weld joint was examined through both optical microscopy and scanning electron microscopy. Examination of the microstructure of the weld interface exposed grain coarsening near the heat-affected zone on the AISI 904L side. In contrast, the weld fusion zone contained fine equiaxed dendrites. Microsegregation and alloying element migration across the entire weld area were assessed through energy dispersive X-ray spectroscopy point analysis and line mapping, revealing controlled microsegregation across the region. X-ray diffraction (XRD) analysis was used to ascertain the average grain size (38.41 nm) and secondary phase composition. The XRD-cosα method was used to assess the residual stress of the weld joint, revealing tensile residual stress in the weld zone and compressive residual stress in other regions. Tensile, Charpy impact, and Vickers hardness tests were conducted in the study to evaluate the strength, toughness, and hardness of a dissimilar weld. The impact of two cryogenic treatments, namely shallow and deep, on tensile and toughness characteristics was investigated in this study. The cryogenic treatments significantly enhanced the mechanical properties of weld samples compared to their as-welded condition, leading to an 11.5% increase in tensile strength and a 10% improvement in toughness. [ABSTRACT FROM AUTHOR]

This study investigates the structure–property relationship in a dissimilar joint between super duplex stainless steel (sDSS 2507) and pipeline steel (X-70) using gas tungsten arc welding and ER2594 filler. Tubing and risers used to transport hydrocarbons are regularly joined using these dissimilar metals. The microstructures of lower heat input (LHI-0.7 kJ/mm) and higher heat input (HHI-1.4 kJ/mm) weldments were examined to understand the influence of heat input on the structure–property relationship. The weldments' mechanical characteristics were tested via hardness, impact, and tensile tests. Base metal and weld zone/interface characterization were studied utilizing optical and scanning electron microscopes with energy-dispersive spectroscopy (EDS). Elemental variation was confirmed by EDS spectra, elemental line mapping, and electron probe microanalysis with wavelength-dispersive spectrometer along the weld interface and weld zone. Significant microstructure variation was observed in X-70 BM at the LHI and HHI weld interfaces. Type II boundary and macro-segregation forms like peninsulas and islands were present in both weldments. In LHI and HHI weldment, duplex microstructure dominates the weld zone cap and filler pass. In the backing pass, duplex microstructure replaces skeletal ferrite, which predominates in the root pass of the HHI weld zone. LHI weldment has an average microhardness of 275 ± 7 HV0.5, while HHI had 285 ± 5 HV0.5. Both weldment's tensile tests revealed that the sample fractured on the weaker X70 BM side. LHI and HHI weldments had 600 MPa and 610 MPa ultimate tensile strengths and 22% and 18% elongation percentages, respectively. LHI weldments (200 ± 7 J, 210 ± 4 J) and HHI weldments (210 ± 5 J, 220 ± 8 J) have lower average impact toughness in cap and root pass than the sDSS 2507 BM (320 ± 3 J) and X-70 BM (300 ± 6 J), respectively. The increase in heat input led to a minimal 2% difference in tensile strength, a notable 10% increase in hardness, and a slight 5% variation in impact toughness between LHI and HHI weldments. Marine and offshore applications may benefit from investigating the sDSS 2507/X-70 DWJ's process parameter selection, thermodynamic analysis, and structure–property relationship. [ABSTRACT FROM AUTHOR]

The as‐cast microstructure, microsegregation of alloying elements, and microstructure evolution during homogenization of the newly designed 15Cr–30Ni–Fe heat‐resistant alloy are studied. Ti, Nb, Si, and Mo segregate at the interdendritic region. The brittle eutectic Laves phase contains Fe, Ti, Ni, Nb, Si, and Mo, which is identified as the Fe2Ti Laves phase. The activation energy for the Fe2Ti Laves phase dissolution is close to the activation energy for Ti diffusion in the γ matrix based on the Johnson–Mehl–Avrami–Kolmogorov analysis. The back‐diffusion of Ti to the γ matrix is the limiting step for the dissolution of Fe2Ti Laves phase. The kinetic equation of homogenization considering lattice parameters and pre‐exponential factor correction is established. After the double‐stage homogenization at 980 °C/10 h + 1140 °C/4 h, the volume fraction of the Laves phase decreases from 5.11% to 0.26%, and the large eutectic Laves phase is completely dissolved. The reduction in the standard deviation of microhardness at different soaking times effectively reflects the gradual decrease in the degree of microsegregation of alloying elements. The average grain size of the alloy after homogenization is 410 ± 63.1 μm, which is beneficial to control the further refinement of grain during the subsequent hot working. [ABSTRACT FROM AUTHOR]

The objective of this study was to investigate how weld overlays with nickel superalloys are important for the integrity, due the high temperatures and corrosive environments that can be experienced in mineral processing environments, of mining and processing equipment. The Ni-Cr-Mo superalloy Inconel 686 overlays are fabricated through automatic gas metal arc welding with variations in arc voltage and travel speed (i.e., heat input), and they have overlap between adjacent weld tracks for applications in the mining and minerals sector. The impact of variations in the process parameters and the size of the weld overlapping on the dilution, solidification morphology, microsegregation, and microhardness were investigated. Both geometric and chemical composition definitions were used to quantify the extent of the weld dilution. Subsequently, the weld geometry and dilution were correlated with the solidification microstructure and phase transformations. The maximum dilutions were measured to be 13.63% (1/2 overlap, 5.96 kJ·cm−1) and 15.39% (1/3 overlap, 4.77 kJ·cm−1), which shows that less of an overlap increases the dilution level. Scanning electron microscopy and chemical composition analysis revealed that an increase in weld heat input and dilution level led to higher levels of microsegregation for Mo and Cr, as well as the volume fraction of Mo- and Cr-rich phases in the interdendritic/intercellular regions in the overlay layer. Analysis of the weld overlays in the current study revealed strong and unprecedented connections between the weld overlay process conditions, the resultant metallurgy (i.e., dendrite arm spacing, microsegregation, and phase formation), and the hardness of the overlay. It was concluded that the optimal weld overlays in the processing window studied in this investigation were fabricated at mid-level heat inputs (i.e., 4–5 kJ·cm−1) and a 1/2 track overlap. [ABSTRACT FROM AUTHOR]

Understanding the as-cast structure acts as a precursor, providing insights for alloy processing into a candidate structural material. The recent developments in high-entropy alloys (HEAs) draw attention to explore such domains for their suitability for commercial structural applications. The present work investigates the correlation between the macro-, microstructure, and mechanical properties of a cast single-phase Al0.2CoCrFeNi HEA. The alloy was produced using a vacuum induction melting route and subsequently characterized using X-ray diffraction (XRD), optical microscopy, and field-emission scanning electron microscopy (FESEM). Mechanical properties were evaluated through uniaxial tensile tests and nanoindentation. The macrostructure of the ingot displayed classical solidification features in both the top and bottom portions. Notably, no macrosegregation was observed in the ingot. However, microsegregation of Al and Ni was detected between the dendritic and interdendritic regions in the top part. Despite the absence of significant variation in macrohardness, the tensile tests revealed noteworthy differences in tensile strength between the top center (330 MPa) and bottom center (464 MPa) of the ingot. This variation in strength was attributed to differences in dendrite arm spacing. Further nanoindentation studies supported the observed tensile behavior, with the top center showing relatively high hardness. This high hardness was found to be correlated with the composition of the dendritic and interdendritic regions. [ABSTRACT FROM AUTHOR]

This study aims at assessing the impact of casting size on the bainitic transformation, resulting microstructures, and tensile properties of a high-carbon, high-silicon steel austempered at different temperatures. The casting size was analyzed by using Y blocks of two different thicknesses. The microsegregation, a common occurrence in cast parts, leads to different bainitic transformation rates at the microscopic scale. Specifically, interdendritic areas with higher alloying contents exhibit a slower transformation, resulting in a lower degree of transformation and a higher amount of blocky austenite. Despite differences in solidification structure and distribution of alloying elements, samples obtained from the thinner and thicker Y blocks yield comparable transformation times and mechanical properties, leading to enhanced uniformity in the mechanical behavior of the entire component. However, it is essential to ensure that the bainitic transformation is completed to minimize the detrimental effects of microsegregation in these cast steel components. The presence of very fine microstructures results in ultra-high strength with low ductility cast steel.

Oxide particles with suitable size can refine the microstructure and improve the strength and toughness of steel. In this study, the particles containing Al2O3 were successfully introduced into H13 steel by vacuum casting. The micro-sized Al2O3-containg particles were randomly distributed in the dendritic structure and their number was increased by almost a factor of one. The secondary dendritic arm spacing of the ingot was decreased, which might be attributed to the heterogeneous nucleation of these oxides during solidification. Meanwhile, the alloying element segregation of the ingot was also alleviated. The micro-sized primary carbides were refined as the oxide particles were introduced to H13 steel, especially for V-rich carbides. After hot rolling and heat treatment, the size of austenitic grain was reduced by up to 75% (7.2 ± 1.8 μm), which was due to the particle stimulated nucleation and Zener pinning of micro- and nanoscale oxides in the oxide-added steel. The mechanical properties were obviously modified with the ultimate tensile strength of 1835 MPa, yield strength of 1479 MPa, tensile elongation of 13.4% and impact toughness of 24 J/cm2 after the introduction of oxide particles. It is expected that the introduction of oxide particles by vacuum casting can be applied widely in other die steel for superior performance.

In this work, the characteristics of surface morphology and structure of experimental samples of nickel-based alloy and copper nozzles manufactured by the electron beam additive method have been studied. It is found that the grain boundaries on the outer sample surface are oriented at different angles relative to the substrate due to uneven heat dissipation during printing. It is found that 3D printing in a non-optimal temperature regime produces a highly heterogeneous structure within the material layer. A curvilinear boundary zone is observed in which different structural phase components are formed, including solid solutions and mechanical mixtures. [ABSTRACT FROM AUTHOR]

In order to gain insight into the unique characteristics of manufacturing large-scale products with intricate geometries, experimental nozzle-shaped samples were created using wire-feed electron beam additive technology. Bimetal samples were fabricated from nickel-based alloy and copper. Two distinct approaches were employed, utilizing varying substrate thicknesses and differing fabrication parameters. The two approaches were the subject of analysis and comparison through the examination of the surface morphology of the samples using optical microscopy, scanning electron microscopy, and X-ray diffraction analysis. It has been demonstrated that the variation in heat flux distributions resulting from varying the substrate thicknesses gives rise to the development of disparate angles of grain boundary orientation relative to the substrate. Furthermore, it is demonstrated that suboptimal choice of the fabrication parameters results in large disparities in the crystallization times, both at the level of sample as a whole and within the same material volume. For example, for the sample manufacturing by Mode I, the macrostructure of the layers is distinguished by the presence of non-uniformity in their geometric dimensions and the presence of unmelted wire fragments. In order to characterize the experimental nozzle-shaped samples, microhardness was measured, uniaxial tensile tests were performed, and thermal diffusivity was determined. The microhardness profiles and the mechanical properties exhibit a higher degree of strength than those observed in pure copper samples and a lower degree of strength than those observed in Inconel 625 samples obtained through the same methodology. The thermal diffusivity values of the samples are sufficiently close to one another and align with the properties of the corresponding materials in their state after casting or rolling. The data discussed above indicate that Mode II yields the optimal mechanical properties of the sample due to the high cooling rate, which influences the structural and phase state of the resulting products. It was thus concluded that the experimental samples grown by Mode II on a thinner substrate exhibited the best formability.

Thermal and electrical conductivity are essential when selecting materials for certain applications. We first present here an analysis of main influencing factors in electrical conductivity of as-cast Mg binary alloys, particularly the effect of the microsegregation of solutes during solidification. A theoretical model is then developed for electrical conductivity in binary Mg alloys, focusing on the effect of solute type and content, and applied to 8 Mg alloy systems with remarkable agreement. Electrical conductivity is then converted into thermal conductivity by Wiedemann–Franz's law, which is also applied to 8 Mg alloy systems, showing significant consistency. This finding provides an easy method for designing and evaluating the electrical/thermal conductivity for Mg alloys, or may be extended to other alloys.

A combined experimental/modeling approach had been performed to investigate the evolution of microsegregation-induced precipitates and its effects on the crack initiation and propagation behavior of 9% Ni steel weldments filled with different kinds of nickel-based alloys. The study found that Nb was more inclined to segregate at the inter-dendritic region than Mo during the cooling of weld metal (WM), which facilitated the precipitation of the Laves phase for Ni–Cr–Mo–Nb weld metal (Ni-WM2), while the segregation of Mo resulted in the precipitation of the P phase for Ni–Cr–Mo weld metal (Ni-WM1). Despite the approximate widths over a range of 1 μm–3 μm for various precipitates, the Laves phase was almost twice as long as the P phase. Besides, the elongated Laves phase had sharp edges and a larger area fraction than the P phase. This caused Ni-WM2 with Laves phase to exhibit quite more deteriorative bending ductility than Ni-WM1 with the P phase. Then, the crack initiation and propagation behaviors were investigated based on the microstructure-based simulation and experimental observation. Further, the great disparity in fracture mechanisms of Ni-WM1 and Ni-WM2 induced by the bending test was revealed.

The production reality of sheet steels from casting to the end product is such that in the cases of ultra- and advanced high-strength steels, we have to deal with the segregation of elements on macro- and microlevels. Both can have a significant impact on the microstructure formation and resulting properties. There are several production stages where it can influence the transformations, i.e., casting, hot rolling process and annealing after cold rolling. In the present work, we focus on the latter, and more specifically, the transformation from ferrite–cementite to austenite, especially the nucleation process, in cold-rolled material. We vary the levels of two substitutional elements, Mn and Si, and then look in detail at the microsegregation and nucleation processes. The classical nucleation theory is used, and both the chemical driving force and strain energy are calculated for various scenarios. In the case of a high Mn and high Si concentration, the nucleation can thus be explained. In the cases of high Mn and low Si concentrations as well as low Mn alloys, more research is needed on the nuclei shapes and strain energy. [ABSTRACT FROM AUTHOR]

Under the industrial process conditions, trace tellurium (13 ppm and 22 ppm) was added to medium-carbon low-sulfur steel to optimize the morphology of MnS inclusion and thereby enhance the machinability of the steel. Voller-Beckermann microsegregation model was used to calculate the precipitation thermodynamics and growth kinetics of MnS inclusion. The morphology of observed MnS inclusion is mainly polygonal (type III), the observed microstructures of the steel are bulk-, acicular-ferrite, and pearlite, the inclusions are mainly present in the bulk-ferrite. The calculation results of inclusion relative plasticity show that 13 ppm Te reduces the relative plasticity of inclusions, while at a Te content of 22 ppm, the relative plasticity of inclusions increases by approximately 70%. Compared with the steel without Te, when containing 22 ppm Te, the material has the best machinability, the average cutting force and average surface roughness of steel are reduced by 3.47% and 38.75%, respectively. [ABSTRACT FROM AUTHOR]

The concept of microsegregation has gained increasing popularity among researchers dealing with socio-spatial disparities in cities. This is because urban space has become increasingly multifaceted over recent decades, and the boundaries of socio-spatial segregation have also become increasingly subtle, often taking invisible forms below the neighborhood level. This study contributes to the literature on microsegregation by exploring small-scale forms of social disparities in one of the neighborhoods of Szeged, a second-tier city in Hungary. We used both quantitative and qualitative research methods to capture visible and invisible forms of microsegregation in the study area. An analysis of census data confirmed the coupling of socio-economic diversity and polarization at the census-tract level in three different forms as a result of various underlying factors, among which the sorting effect of the housing market plays a leading role. The results of in-depth interviews with experts and residents suggest that although the overall perception of the neighborhood is good and that serious conflicts do not occur, there are palpable socio-spatial differences and signs of segregation at the micro scale. The weak sense of segregation can be partly linked to the lack of public spaces where daily encounters between people from different social groups could take place. [ABSTRACT FROM AUTHOR]

Two kinds of 25Cr-35NiBr Fe-based superalloy deposits with the distinguishing microsegregation were fabricated through controlling processing parameters of laser additive manufacturing (LAM). The effect of microsegregation on microstructural evolution was investigated thoroughly at high temperature. The results show that the microsegregation of Nb and Ti near cell boundaries plays a dominant role on the microstructural evolution at high temperature. When Nb. and Ti do not segregate significantly near cell boundaries, at elevated temperature the microstructure tends to evolve into a multiscale precipitated phases structure of Cr23C6, Cr7C3 and (Nb, Ti)C to improve the microstructural high-temperature stability. When Nb and Ti are obviously segregated near cell boundaries, at high temperature the microstructure possess a tendency to evolve into a chain (Nb, Ti)C to significantly decline the microstructural high-temperature stability. This research will provide new insights into the performance control and the microstructural evaluation of superalloy fabricated by LAM. [ABSTRACT FROM AUTHOR]

As a kind of urban neighborhood with strong internal heterogeneity, mixed-housing neighborhoods have attracted wide attention from scholars in recent years. Strengthening community ties in mixed-housing neighborhoods is of great significance for increasing neighborhood social capital, cultivating a sense of community, and promoting sustainable development of the neighborhood. The neighborhood activities of residents are an important factor in promoting community ties. However, different housing groups in mixed-housing neighborhoods may have differentiated or even segregated overall daily activities, which may impact their neighborhood activities and call for differentiated planning strategies. In this study, we conduct an empirical study in Fuzhou, China, to identify the spatiotemporal-behavior-based microsegregation and differentiated community ties between residents of different types of housing. The data were collected in 2021 and included residents' activity diary data and questionnaire data about neighborhood interaction and community ties. Through an analysis of the daily overall activity space and activities within the neighborhood areas, the spatiotemporal-behavior-based social segregation of various housing groups is depicted. Furthermore, a multigroup structural equation modeling method was used to analyze the relationships among residents' spatiotemporal behaviors, neighborhood interactions, and community ties, and the heterogeneous influence effects across housing groups. The results show that the more residents' activity spaces overlap with the neighborhood area, the more out-of-home time they spend within the neighborhood, and that the more types of activities are conducted within the neighborhood area, the stronger their community ties are. In addition, neighborhood interaction played a linkage role in the relationships of residents' spatiotemporal behaviors and community ties. Our research aims to further the understanding of microsegregation at the neighborhood level and provide references for the development of mixed-housing neighborhoods and urban land use. [ABSTRACT FROM AUTHOR]

The phase transformation of carbon steel has always been a research hotspot. Researchers study the phase transformation process of steel in terms of the original structure, chemical composition, and process conditions, and the cooling rate in process conditions has an important influence on the phase transformation of steel. In this study, Thermo-calc thermodynamic software is used to simulate and calculate the phase transformation process of 3.52%Al (mass fraction) delta ferrite transformation-induced plasticity (δ-TRIP) steel, and differential scanning calorimetry (DSC) and the Ohnaka microsegregation model are used to analyze the effect of cooling rate on the peritectic transformation temperature and solute element segregation during solidification of 3.52%Al δ-TRIP steel. The results show that the smaller the cooling rate is, the closer the DSC phase transition temperature is to the thermodynamic equilibrium value calculated by Thermo-calc. Increasing the cooling rate from 10 to 30 to 50 ℃·min−1 decreases the phase transition temperature of L→L+δ and first decreases and then increases those of L+δ→L+δ+γ and L+δ+γ→δ+γ. The former temperature is mainly affected by cooling, and the latter temperatures are mainly affected by element segregation. Among the six elements (C, Si, Mn, P, S, and Al) of 3.52%Al δ-TRIP steel, the segregation of S is the most severe. This result is obtained because the partition coefficient k of the S element at the solid–liquid interface is much smaller than those of other solute elements. The rapid S element enrichment at the end of solidification increases the possibility of sulfide precipitation, forms a low melting point liquid film between dendrites, reduces the zero plastic temperature, and increases the solidification brittleness range and crack sensitivity. Therefore, the sulfur content in steel should be strictly controlled during composition smelting. The cooling rate slightly affects C, Mn, and S segregation but greatly affects Si, P, and Al segregation, and the degree of segregation of Si, P, and Al increases with the cooling rate. The segregation of Si, P, and Al delays the peritectic reaction process, the segregation of Si and P slightly delays the peritectic reaction process, and Al segregation clearly delays the peritectic reaction process. With increasing cooling rate, the lower the peritectic reaction area moves, the slower the peritectic reaction process. This study can provide a theoretical basis for the continuous casting process parameters of δ-TRIP steel.

In recent years, multiple-burden maps were developed as a tool for assessing environmental health inequities in cities. Maps of this kind are particularly useful in identifying disadvantaged neighbourhoods. In the case of Erlangen (Germany), the historical development of poorer neighbourhoods may mean that their situation as regards environmental assets is relatively favourable. However, urban renewal often precipitates the redistribution of environmental “goods” and “bads” in such a way as to place a disproportionate burden on socio-economically deprived people and privilege the better-off. This type of environmental microsegregation occurs on a scale below that of neighbourhoods, which means that newly developed approaches in urban geography may fail to identify it. This article details the roots of these processes in changes in the structure of ownership and the respective administration of housing and considers possible methods for monitoring these tendencies.

The paper addresses the microsegregation of Mn, Mo, Cr, W, V, Si, Al, Cu and P in the white cast iron. Eutectic alloy with the content of 4.25% C was studied. The white cast iron was directionally solidified in the vacuum Bridgman-type furnace at a constant pulling rate v = 83 μm/s and v = 167 μm/s and at a constant temperature gradient G = 33.5 K/mm. The microstructural research was conducted using light and scanning electron microscopy. The microsegregation of elements in ledeburite was evaluated by EDS measurements. Content of elements in ledeburitic cementite and ledeburitic pearlite was determined. The tendency of elements to microsegregation was found dependent on the solidification rate. Microsegregation of elements between pearlite and cementite structural constituents has been specified. The effect of solidification rate on the type and intensity of microsegregation in directionally solidified eutectic white cast iron was observed. A different type of microsegregation was observed in the components of ledeburite in cementite and pearlite.

Weld overlays of Ni-based superalloys provide high-temperature corrosion, oxidation, and wear resistance for industrial applications. The objective of this study was to evaluate the microstructure of Ni–Cr-Mo superalloy Inconel 686 overlays fabricated using automatic gas metal arc welding (GMAW) with three different levels of voltage, travel speed, and wire feed speed. The variation of these parameters and their effects on the weld quality, dilution, and microsegregation were analyzed. The weld surface quality was assessed by visual examination. The weld dilution was measured by both geometric and chemical composition definitions. The maximum dilution was measured at 13.63%, induced by the highest weld heat input (5.97 kJ cm−1) and lowest wire feed speed (6 m min−1). The overlay dilution and the heat-affected zone (HAZ) size decreased by increasing the wire feed speed. However, increasing the wire feed speed and the heat input reduced the weld quality and even resulted in noncomplete joints. Microsegregation of elements was evaluated using energy-dispersive X-ray spectroscopy (EDS) analysis and it was found that microsegregation of Mo and Cr and the volume fraction of secondary phases in the interdendritic areas increased with increasing the weld heat input. According to the visual examination results and macro- and microscopic evaluation, the weld overlay parameters were found to be optimized for the mid-level heat inputs (4–5 kJ cm−1) and wire feed speeds between 6 and 8 m min−1. [ABSTRACT FROM AUTHOR]

Experimental results of microstructural studies of refractory nickel alloys obtained by selective laser melting under different crystallization conditions are systematized. The dendritic (cellular) structure and the distribution of the alloying elements in the volume of dendrite arms are studied by scanning and transmission electron microscopy. The detected microsegregation matches a normal crystallization law and is caused by concentration supercooling. It is shown that the main factors responsible for formation of the fine structure of a track are the orientation growth (epitaxy) and the competitive growth of crystallites. The orientation of the crystallites is transferred not only by the first-order arms but also by the second-order arms, and a specific direction is implemented upon coincidence of the crystallographic orientation of the crystallite with the radial direction of the heat removal. The increasing complexity and the fragmentation of the fine structure are associated with the mechanism of stochastic binarization of the crystallographic orientation implemented upon partial remelting and opening of fragments of cells in the current and preceding layers. [ABSTRACT FROM AUTHOR]

Rapid solidification during metal additive manufacturing (AM) leads to non-equilibrium microsegregation, which can result in the formation of detrimental phases and cracking. Most of the microsegregation models assume a Scheil-type solidification, where the solidification interface is planar and there exists a local equilibrium at the interface along with either zero or infinite solute diffusion in the respective participating phases—solid and liquid. This assumption leads to errors in prediction. One has to account for finite solute diffusion and the curvature at the dendritic tip for more accurate predictions. In this work, we compare different microsegregation models, that do and do not consider finite diffusion and dendrite tip kinetics, against experiments. We also propose a method to couple dendrite tip kinetics with the diffusion module (DICTRA®) implemented in Thermo-Calc®. The models which accounted for both finite diffusion and dendrite tip kinetics matched well with the experimental data. [ABSTRACT FROM AUTHOR]

Aluminum–lithium alloys have the potential for use in aerospace applications, and improving their physical, mechanical, and operational characteristics through alloying is a pressing task. Lithium, with a density of 0.54 g/cm3, enhances the elastic modulus of aluminum while reducing the weight of the resulting alloys, making them increasingly attractive. Adding transition metal additives to aluminum alloys enhances their strength, heat resistance, and corrosion resistance, due to their modifying effect and grain refinement. The study aimed to investigate the impact of titanium content on the microstructure, corrosion resistance, and hardness of Al-Li alloys. Four alloys were prepared with varying amounts of titanium at 0.05 wt%, 0.1 wt%, 0.5 wt%, and 1.0 wt%. The results showed that the microstructure of the alloy was modified after adding Ti, resulting in a decrease in average grain size to about 60% with the best refinement at 0.05 wt% Ti content. SEM and EDS analysis revealed an irregular net-shaped interdendritic microstructure with an observed microsegregation of Al3Li compounds and other trace elements at the grain boundaries. The samples showed casting defects due to the high content of Li in the alloy, which absorbed air during casting, resulting in casting defects such as shrinkage holes. The corrosion resistance test results were low for the samples with casting defects, with the least resistance recorded for a sample containing 0.1 wt% Ti content, with more casting defects. The addition of Ti increased the microhardness of the alloy to an average of 91.8 ± 2.8 HV. [ABSTRACT FROM AUTHOR]

In this paper, the as-cast microstructure, microsegregation, precipitates and suitable homogenization process of a novel Ni-based wrought superalloy prepared by vacuum induction melting (VIM) + vacuum arc remelting (VAR) were investigated by optical microscope (OM), scanning electron microscope (SEM), electron probe microanalysis (EPMA), differential scanning calorimetry (DSC), high temperature confocal laser scanning microscope (HT-CLSM) and thermal simulation compression. The results show that severe element segregation exists in the ingot. Nb, Ti and Al are mainly segregated in the interdendritic region, while W is mainly segregated in the dendrite arm. The precipitates in the alloy mainly include non-uniform γ′ strengthening phase, coarse (γ + γ′) eutectic phase and MC carbide, among which, the redissolution temperature range of γ′ phase is 1060–1220 °C; the (γ + γ′) eutectic phase can be redissolved obviously above 1180 °C but melted into liquid at 1250 °C; the redissolution temperature range of MC carbide is 1349–1358 °C, exceeding the solidus temperature of the alloy. After homogenization at 1220 °C/10 h, all the γ′ phase and most of the (γ + γ′) eutectic phase can be redissolved, and the element segregation can be significantly alleviated, moreover, the hot deformation resistance of the alloy is lower and the dynamic recrystallization (DRX) degree is higher, indicating that 1220 °C/10 h is an ideal single-stage homogenization process.

The annealing response of 316L stainless steel manufactured with both laser powder bed fusion (PBF-LB) and wire-arc directed energy deposition (DED-Arc) was investigated in the context of microstructural evolution and mechanical properties. Because additive manufacturing (AM) comprises several technologies that differ in heat source, feedstock, and scan strategy, among other build variables, the final products can experience a range of thermal histories and defect (dislocation) populations. These unique thermal histories can subsequently influence as-built properties and annealing response of AM materials, most notably those manufactured with different AM deposition processes. The PBF-LB process (with higher cooling rates) yielded finer austenite microstructures having more lattice strain, higher dislocation densities, and higher yield strength values than the DED-Arc 316L process (with lower cooling rates). Electron backscattered diffraction (EBSD) data of the kernel average misorientation (KAM), boundary density, and geometrically necessary dislocation (GND) density support the differences in lattice strain. As a result, the PBF-LB 316L exhibited more recovery and recrystallization after annealing at elevated temperatures above 873 K based on changes to yield strength, work hardening behavior, and microstructure evolution. The DED-Arc 316L exhibited a δ-ferrite/austenite microstructure with microsegregation that influenced deformation mechanisms active after annealing. Tensile data, deformed microstructures and misorientation histograms from EBSD showed a decreasing amount of deformation twinning when comparing the as-built condition to annealed conditions (up to 1473 K/1h) of PBF-LB 316L. The opposite trend was noted in DED-Arc 316L. The behavior was interpreted to be due to the differences in chemical segregation during solidification and the effects of heat treatment on chemical homogenization and local stacking fault energy. [ABSTRACT FROM AUTHOR]

We introduce both CALPHAD coupling and interfacial non-equilibrium to a model of microsegregation that accounts for finite diffusion. The approach can also be used to perform Gulliver–Scheil calculations using a kinetic phase diagram, which would normally involve solving an underdetermined system of equations. The non-equilibrium finite-diffusion model is first applied to the Ag–15wt.%Cu system, where we find that previously reported experimental measurements can be completely described with the full non-linear phase diagram and the choice of appropriate kinetic constitutive parameters, indicating that the effects of finite liquid diffusion remain significant under processing conditions relevant to additive manufacturing. The model is enhanced to account for multiple phases forming from the liquid and then applied to a multicomponent Co-base superalloy, showing that finite liquid diffusion can influence both the compositions and fractions of secondary solid phases. [ABSTRACT FROM AUTHOR]

The production reality of sheet steels from casting to the end product is such that in the cases of ultra- and advanced high-strength steels, we have to deal with the segregation of elements on macro- and microlevels. Both can have a significant impact on the microstructure formation and resulting properties. There are several production stages where it can influence the transformations, i.e., casting, hot rolling process and annealing after cold rolling. In the present work, we focus on the latter, and more specifically, the transformation from ferrite–cementite to austenite, especially the nucleation process, in cold-rolled material. We vary the levels of two substitutional elements, Mn and Si, and then look in detail at the microsegregation and nucleation processes. The classical nucleation theory is used, and both the chemical driving force and strain energy are calculated for various scenarios. In the case of a high Mn and high Si concentration, the nucleation can thus be explained. In the cases of high Mn and low Si concentrations as well as low Mn alloys, more research is needed on the nuclei shapes and strain energy.

Local variations of the chemical composition, that is, compositional inhomogeneities, play an important role in the thermodynamic stability and spatial distribution of phases in multiphase steels. As is already known, the inhomogeneity of the distribution of chemical elements in the structure of structural grade carbon steels is formed mainly during their crystallization, during the hardening of the ingot or continuously cast billet. The limited solubility of alloying elements in the solid state in steel leads to liquation during solidification. During crystallization, the solute is partitioned between the solid and the liquid to enrich or deplete the interdendritic regions. This naturally leads to variations in the composition on a micrometer scale, i.e., microsegregation. The formation of the liquation background (dendritic pattern) is due to the alternate enrichment of elements of individual microzones (segregation) during steel crystallization. The areas of segregation of manganese and silicon even in carbon steels have a strong influence on the morphology and arrangement of phases of the final structure formed in carbon steel products. Diffusion of solid elements during the reheat cycle, particularly aluminium and manganese, is too slow to result in chemical homogenization. As a result, the segregation profiles present after casting remain during all subsequent processes and have a significant impact on the final striated in homogeneity of the microstructure. Thus, the control of microsegregation during hardening in modern steels is crucial for obtaining uniform mechanical properties of the final product, since phase transformations occurring during thermal and/or deformation treatments determine the final microstructure and are reflected by the local distribution of hardness. [ABSTRACT FROM AUTHOR]

In recent years, multiple-burden maps were developed as a tool for assessing environmental health inequities in cities. Maps of this kind are particularly useful in identifying disadvantaged neighbourhoods. In the case of Erlangen (Germany), the historical development of poorer neighbourhoods may mean that their situation as regards environmental assets is relatively favourable. However, urban renewal often precipitates the redistribution of environmental "goods" and "bads" in such a way as to place a disproportionate burden on socio-economically deprived people and privilege the better-off. This type of environmental microsegregation occurs on a scale below that of neighbourhoods, which means that newly developed approaches in urban geography may fail to identify it. This article details the roots of these processes in changes in the structure of ownership and the respective administration of housing and considers possible methods for monitoring these tendencies. [ABSTRACT FROM AUTHOR]

The paper studies the chemical and phase composition of the product from heat-resistant nickel-based superalloy formed by wire-feed electron beam additive manufacturing (EBAM). Microsegregation on macro-(dendrites/interdendritic space) and microscale (γ/γˈ) was evaluated. It is shown that in additively formed material, there is a significant (by an order of magnitude) refinement of structural and phase elements. The degree of microsegregation remains unchanged after the additive process, despite the increase in the volume fraction of dendrites, and the complex thermal history does not lead to the formation of undesirable phases. [ABSTRACT FROM AUTHOR]

The concept of microsegregation has gained increasing popularity among researchers dealing with socio-spatial disparities in cities. This is because urban space has become increasingly multifaceted over recent decades, and the boundaries of socio-spatial segregation have also become increasingly subtle, often taking invisible forms below the neighborhood level. This study contributes to the literature on microsegregation by exploring small-scale forms of social disparities in one of the neighborhoods of Szeged, a second-tier city in Hungary. We used both quantitative and qualitative research methods to capture visible and invisible forms of microsegregation in the study area. An analysis of census data confirmed the coupling of socio-economic diversity and polarization at the census-tract level in three different forms as a result of various underlying factors, among which the sorting effect of the housing market plays a leading role. The results of in-depth interviews with experts and residents suggest that although the overall perception of the neighborhood is good and that serious conflicts do not occur, there are palpable socio-spatial differences and signs of segregation at the micro scale. The weak sense of segregation can be partly linked to the lack of public spaces where daily encounters between people from different social groups could take place.