Fine Grain Research Articles

Synthesis of fine Na-type zeolite grains from coal fly ash and the assessment of the adsorption capability of lead ions from aqueous solutions

Fine Na-type zeolite grains (ZE) were prepared by dry milling treatment (D-ZE) or wet milling treatment (W-ZE).

Microstructural regulation and mechanical behavior of asymmetrically extruded high-content TC4p reinforced AZ31 composite

Asymmetric extrusion (AE) is frequently used to weaken the texture of magnesium (Mg) alloys to improve their mechanical properties. In this paper, to explore the influence of asymmetric extrusion on the microstructure and mechanical properties of Mg matrix composites (MMCs), we synthesized TC4/AZ31 composite sheets via ball milling coupled with sintering and then various extrusions (including conventional extrusion (CE), transverse-directional AE (TDE), and normal-directional AE (NDE)). The differences in microstructure and performance among the three processed samples were compared and analyzed using SEM, XRD, EBSD characterization and tensile testing. The results showed that the asymmetrically extruded samples achieved better mechanical properties compared to their CE counterparts. It found that the grain refinement was relatively significant and texture evolution was dispersed in AE samples compared to the CE ones, which was attributed to the TC4 particle (TC4p) disturbance and extra asymmetric shear of matrix flow. Three different macro-textures were obtained in various extruded processes, and the micro-texture of each sample changed in diverse regions. Based on grain orientation spread (GOS) analysis, the introduction of TC4p resulted in dynamic recrystallization (DRX) and particle-stimulated nucleation (PSN) effects during the AE process at 350 °C. The mechanisms of the combination of ductility and strength in the AE-processed sheets were related to the finer grains, high Schmid factor (SF), evenly distributed dislocations and scattered texture. This work can also provide the feasibility and prospects of applying asymmetric extrusion to MMCs.

Раціональні технологічні засади отримання коксу із заданими показниками питомого електричного опору

DOI: 10.31081/1681-309X-2024-0-1-8-15 Specialty 161. U.D.C. 661.66.2:537.311/.312 RATIONAL TECHNOLOGICAL BASES OF PRODUCTION OF COKE WITH SPECIFIED ELECTRICAL RESISTIVITY © I.V. Shulga, Ph.D. in Technical Sciences, O.V. Sytnyk, Ph.D. in Technical Sciences (State Enterprise “Ukrainian State Research Institute for Carbochemistry (UKHIN)”, 7 Vesnina str., Kharkiv, 61023, Ukraine), O.I. Zelenskii, Ph.D. in Technical Sciences, V.V. Vladymirenko (National Technical University "Kharkiv Polytechnic Institute", 2, Kyrpychova str., Kharkiv, 61002, Ukraine) The article is devoted to the practically important issue of obtaining coke with a specific electrical resistance of no more than 0.1 Ohm∙cm for the needs of blast furnace production. Achievement of this indicator should occur simultaneously with the improvement of the entire range of properties of blast furnace coke. It is noted that the concept of production of blast furnace coke of improved quality consists of the formation of a rational raw material base, ensuring proper coking technology and post-furnace coke treatment. It has been shown that the production of high-quality blast furnace coke with low resistivity requires: high sinterability and coking capacity of the charge based on highly sinterable coals; coking pressure of the coal charge not exceeding 7 kPa; coking speed not exceeding 24 mm/hour; final coking temperature of 1050-1100 °C; maximum temperature level in the heating system not exceeding 1410 °C. It is confirmed that in order to obtain a low electrical resistivity, it is necessary to produce coke with the most ordered anisotropic structure. It is shown that the resistivity of coke naturally changes when used in blast furnace production: the destruction of lumps leads to the formation of fragments of different sizes. At the same time, coarser fragments have lower resistivity values, and smaller ones, characterized by an increased concentration of structural defects that are the centers of crack formation, have a higher resistivity. After gasification with carbon dioxide, the number of structural defects increases in grains of any size due to the weakening of the surface due to chemical interaction, so the resistivity of coke increases and becomes almost equal for both coarser and finer grains. Keywords: hard coal coke, blast furnace production, resistivity, vertical temperature, final coking temperature, coke gasification. Corresponding author I.V. Shulga, e-mail: ko@ukhin.org.ua

Granulometric Analyses of Stream Sediments from Kolar River Sub-Basin, Central India

This paper focuses on a granulometric study conducted to investigate the sedimentary characteristics of channel sediments in the upper, middle, and lower reaches of the Kolar River Sub-basin. The study's primary objective is to gain a detailed understanding of sediment transport by seamlessly integrating field surveys and laboratory analyses. The study investigates grain size distribution and the deposition environment in the Kolar River Sub-basin. From sediment data, statistical measures were prepared and utilized to construct bivariate diagrams and examine the inter-relationship of various parameters. The results indicate that the upper reach exhibits poor sediment sorting, while the middle and lower reaches show more moderate sorting. Skewness values indicate dominance of coarser sediments in the upper reach, finer grain sizes in the middle reach, and a mixed distribution in the lower reach. Kurtosis values suggest concentrated distributions in specific areas of the upper and middle reaches, while the lower reach displays a broader distribution. The CM plot analysis reveals distinct sediment transport types in each reach, reflecting the energy level of water transport and sediment load. This study provides valuable insights into spatial variations in sediment dynamics, contributing to a comprehensive understanding of the overall sedimentary regime of the river. With this understanding, effective river basin management techniques, such as vegetative stabilization, check dam construction and prevention of excessive deposition can be implemented to ensure the sustainable management of the Kolar River Sub-basin. Keywords: Granulometry, Stream Sediments, Depositional Environment, Sustainable Management, Kolar River Sub-Basin, Central India

Improved mechanical properties of high-speed extruded BA53 alloy through long-range water-cooling system

A recently developed Mg–5Bi–3Al (BA53, wt%) alloy exhibited remarkable extrudability despite its high alloying content. However, when subjected to high-speed extrusion with a die exit speed of 67 m/min, grain coarsening of recrystallized grains occurs, increasing their size from 12.1 to 26.4 μm due to excessive heat generation during extrusion. Herein, a long-range water-cooling system is installed immediately after the extrusion die to mitigate grain coarsening and attain finer grains in the high-speed extruded alloy. The results demonstrate that the use of the cooling system leads to a significant reduction in the average grain size (from 26.4 to 15.7 μm) of the BA53 alloy extruded at high speed. Furthermore, grain refinement led to notable increases in the ultimate tensile strength (from 255 to 276 MPa) and elongation (from 7.5% to 8.6%) of the alloy. These enhancements in strength and elongation are primarily attributed to the enhanced grain-boundary hardening effect and suppression of twinning during tension, both of which are consequences of grain refinement. This study underscores the effectiveness of a long-range water-cooling system, comprising water spraying over a length of 2 m, in achieving grain refinement during high-speed extrusion of the BA53 alloy and improving both the strength and ductility of the alloy after high-speed extrusion.

Effect of Sc contents on the mechanical properties and damping capacity of Al–Zn–Mg–Cu–Zr–Sc alloys with different grain structures

Al–Zn–Mg–Cu–Zr–Sc alloys with different Sc contents were fabricated by casting, deformation, and T6 treatment. Deformation methods including rolling and friction-stir processing (FSP) were used to design their grain structure. A low additive amount (0.1) of Sc cannot refine the grains of the alloy with rolling and T6 treatment, and it instead coarsened the grains. The reason was the non-uniform distribution of nanosize Al3(Sc,Zr) phases that led to the occurrence of abnormal grain growth during homogenization. Meanwhile, the alloy with only 0.1Sc exhibited finer grains after FSP and T6 treatment than the alloys subjected to the same process but with higher Sc additive amount. Alloys with rolling-induced elongated grain structure exhibited better mechanical properties, and alloys with FSP-induced fine equiaxed grain structure exhibited higher high-strain and high-temperature internal friction values. These features are important performance parameters for applications in fields where vibration and noise are sensitive. The optimum additive amounts of Sc for alloys with elongated and fine equiaxed grain structures were 0.25 and 0.1, respectively.

Insight into the slope-plateau capacity behaviour of polymer-derived silicon oxycarbide anodes in Na-ion batteries

Silicon oxycarbide-based amorphous ceramic material was prepared by crosslinking and step-wise pyrolysis of polysiloxane-based Polyramic resin at temperatures up to 1200 °C as a matrix for anode in Na-ion batteries (NIBs). The synthesized powder was milled under low and high energy ball milling (LEM, HEM) conditions to investigate the effect of powder characteristics on the electrochemical properties of anodes in NIBs. The XPS and EDX analyses showed that the chemical compositions of anodes prepared from LEM and HEM SiOC were similar. However, the SiOC anodes prepared from finer grain sized HEM SiOC powders exhibited better performance like lower charge transfer resistance and faster Na+ diffusion coefficient. The slope capacity and thereby the total specific capacity was enhanced in HEM-SiOC anode. Therefore, the refinement of the particle size and increased surface area are vital for producing high-energy density SiOC anodes for NIBs.

Strain-rate-dependent behavior of additively manufactured alumina ceramics: Characterization and mechanical testing

This study experimentally investigates the mechanical behavior of additively manufactured (AM) alumina ceramics by stereolithography technique. The AM alumina specimens with two different printing orientations (POs) are tested under quasi-static and dynamic loading rates. The material shows a quasi-static (i.e., a strain rate of 10−3 s−1) compressive strength of 1640.54 ± 99.33 MPa and 1494.25 ± 260.08 MPa for the PO1 and PO2, respectively, and a dynamic (i.e., a strain rate of 640–730 s−1) compressive strength of 3077.25 ± 174.07 MPa and 3107.33 ± 97.03 MPa for the PO1 and PO2, respectively, which are among the highest reported values for AM alumina due to the higher density and finer grain size. The strain-rate-dependent compressive strength of the material is slightly affected by the PO which is alleviated with the increase in strain rate from quasi-static to dynamic loading conditions. In contrast, the PO noticeably affects the macro-scale failure pattern. The fractography analysis shows the dominant contribution of the intergranular failure mechanism and a combination of intergranular and transgranular mechanisms under quasi-static and dynamic loading, respectively. The crack speed propagation is found to be 785 ± 174 m/s on average which is ∼68% less than that of conventional ones in the literature. The current AM alumina shows a hardness of 24.45 ± 0.88 GPa which is higher than that of the majority of other AM alumina. Overall, this study discusses the potentiality of using AM ceramics in engineering fields replacing the conventionally-made counterparts, and provides implications for designing better-performing AM ceramics.

Study on microstructure evolution and mechanical properties of similar joint of Al-Mg-Si alloy by tungsten inert gas welding

Study on microstructure evolution and mechanical properties of similar joint of Al-Mg-Si alloy by tungsten inert gas welding

Thermo-mechanical process variables driven microstructure evolution during additive friction stir deposition of IN625

Additive friction stir deposition is an innovative technique for solid-state additive manufacturing involving complex thermo-mechanical processes such as frictional heating, plastic deformation, and viscoplastic material flow, which repeats layer by layer during material deposition. The present study is an attempt to understand the relationship between the complex thermo-mechanical process attributes and the resultant microstructure in additive friction stir deposition of IN625. The estimation of thermo-mechanical process attributes, primarily temperature and strain rate during multi-layer deposition was based on the already established thermo-pseudo-mechanical description of friction stir based processes. The complex thermo-mechanical interaction associated with multi-layer material deformation, deposition, and flash formation can be attributed to variations in the average deposition temperature and the strain rate. Microstructural examination of the additive friction stir deposited sample was performed using electron backscatter diffraction. As a result of the additive friction stir deposition associated thermo-mechanical conditions, the microstructure exhibited fine equiaxed grains in the plane along the build direction along with bands of very fine grains within the interface regions between deposited layers. The observation of fine equiaxed grains and a lower degree of in-grain misorientation in the additively fabricated sample pointed to dynamic recrystallization as the governing restoration mechanism during the deposition process. The grain size refinement during additive friction stir deposition of IN625 resulted in substantial augmentation in the yield strength compared to IN625 feed material and as-cast IN625.

Geochemical Characteristics of the Mallawa Formation, and its Relationship with the History of Source Rock Formation in the South Makassar Basin, South Sulawesi

A hydrocarbon system to determine the hydrocarbon potential in an area can be determined by the presence of three main components that ensure its existence together, one of main components are source rock. The South Makassar Basin has the potential to have a petroleum system that acts as a source rock for the Mallawa Formation. Source rock is a component of the petroleum system that has the ability to produce and store hydrocarbons, where this rock is generally a rock with fine grains such as coal or shale. Oil and gas exploration in Indonesia is a common thing because there are many prospect areas that have the potential to produce hydrocarbons. The South Makassar Basin is a Tertiary sedimentary basin of land type which is geographically located along West Sulawesi to South Sulawesi and this basin occurs due to tectonics or structures with high frequency. The South Makassar Basin was formed as a result of the expansion of the Makassar Strait which occurred at no younger than the Early Paleocene age where the tectonic consequences would influence the maturation process of the source rocks in the South Makassar Basin. Apart from that, in this research a geochemical method was carried out in the form of laboratory analysis to determine the maturity of the source rock using cuttings samples. So this research provides something new in the exploration of the maturity of source rocks, which in the South Sulawesi area has a complex tectonic setting.

Analysis of quenching temperature variations in the heat straightening processFor multiple ripair FCAW welding HSLA SM490YA material

In the steel structure fabrication industry, girders play a crucial role as supporting beams during construction. The girder's components include end plates and beams, with the end plate serving as a critical connection point for the beam to the column. Welding at this juncture demands careful consideration. This analytical research focuses on the impact of multiple repair welding and quenching temperatures during the heat straightening process on the toughness and microstructure of HSLA SM490YA material, utilizing FCAW welding. To assess the effects of multiple repair welding, the study compares different repair scenarios—welding without repair, two repairs, and three repairs, all performed at a 50% depth. Subsequently, the heat straightening process occurs at a temperature of 650ºC on the repaired material. Post-heat straightening, quenching is carried out with temperature variations of 650ºC, 475ºC, and 300ºC. The findings indicate that the repair process during welding and subsequent quenching after the heat straightening process leads to a decrease in toughness values. This results in a finer grain size, with the material phase predominantly composed of pearlite. These research outcomes should be carefully considered by industry professionals, particularly in critical connections, when determining quenching temperatures after the heat straightening process in repair procedures.

A Comparative Reservoir Study of Zubair and Nahr Umr Formations in Subba Oilfield, Southern Iraq

The lower Cretaceous sandstones of Zubair and Nahr Umr formations are the main producing reservoirs in Subba oilfield in southern Iraq. Key differences in their petrophysical and depositional attributes exist affecting their reservoir characteristics. The evaluation of well logs and core porosity-permeability data show better reservoir properties in Nahr Formation. The Litho-saturation logs indicate greater thickness of oil-saturated reservoir units for Nahr Unr Formation associated with lower values of shale volume, and higher values of effective porosity. In addition, higher values of permeability for Nahr Umr Formation is suggested by applying porosity-irreducible water saturation cross plot. The reducing reservoir quality of Zubair Formation sandstones is related to finer grains of sandstone reservoirs, higher clay volume, and more effect of compaction resulting from greater depth. A reservoir layering scheme is proposed by sequence stratigraphic analysis leading to the identification of systems tracts and their key surfaces within Zubair and Nahr Umr formations, and forms the basis for predicting of reservoir architecture and quality. Laterally continuous, and thick amalgamated sandstone reservoirs are formed during highstand systems tract in Nahr Umr Formation as a result of low accommodation/sediment supply conditions. Within the transgressive systems tract of Zubair Formation, the sandstone reservoir bodies become isolated as accommodation exceeds sediment supply.

Study of Sediment Deposit Characteristics based on Geotechnical Properties and Geographic Information System (GIS) Approaches

Several sedimentation processes occur in the downstream area between river mouths and the sea. One of the effects of this sedimentation process is the occurrence of siltation around the coast. Not infrequently, this disrupts sea passages when the ship is about to head to the pier or go to sea. Kuala Beach is one of the locations in Pangkalpinang where the sedimentation process continues to occur enough to disrupt the smooth flow of sea traffic. This study aims to provide an overview and analysis of results related to sediment characteristics, spatial analysis of deposits, and predictions of deposition rates around Kuala Beach, Pangkalpinang City. This research was conducted using the following methods: 1) Method of investigating sediment characteristics by collecting data through field testing in the form of hand drills and laboratory testing, 2) Spatial analysis method by mapping the area of sedimentation based on the results of sediment characteristic tests using Agisoft Metashape and QGIS. The results of this study note that sediment deposits are dominated by sediments with sandy grain characteristics (SP symbol based on the Unified Soil Classification System) and a fine grain content (passing sieve number 200) of around 1-3%. The pattern of distribution of sediment deposits is known to have relatively flat contours and relatively uniform characteristics down to a depth of 1.5 m. The coefficient of grain uniformity (Cu) is in the range of 2.43-8.2 with the tendency of uniformity level getting higher to the southeast. The coefficient of grain gradation (Cc) is in the range of 0.44-1.64 with the tendency of the gradation level getting better to the southeast.

Enhancing grain refinement and mechanical properties of AA1100/MgAZ31/AA1100 composites by using different roll bonding techniques

This paper examines the microstructure and mechanical properties of AA1100/Mg AZ31/AA1100 composites processed by conventional accumulative roll bonding (ARB) and cross accumulative roll bonding (CARB) methods. Based on the results, with an increase in deformation strain, Mg layers gradually lose their continuity in the form of localized necking and fragmentation. However, changing the strain path and pre-annealing the initial sheets could retard and homogenize the plastic instabilities. According to the results of electron back-scattering diffraction (EBSD), applying severe plastic deformation led to refined-grain structures with equiaxed grains. The finer grains were obtained in composites processed by the CARB method following the pre-annealing treatment. Employing this procedure also intensified the basal-type texture and circled its shape. The strong basal texture and grain refinement led to the highest Mg alloy and Al hardness values of 99 and 64 HV, respectively. Furthermore, changing the strain path and pre-annealing treatment increased the elongation by 46% in the seventh pass compared to ARBed samples. Also, this procedure increased the ultimate strength from 375 to 391 MPa and gave rise to yield strength from 164 to 176 MPa.

Effect of deformation heterogeneity on development of geometrically necessary dislocation density in heterogeneous-structured CrMnFeCoNi high-entropy alloy

Heterogeneous-structured high-entropy alloys (HEAs) overcome strength-ductility trade-off, demonstrating potential for a wide range of applications in aerospace, defense and military fields. In this work, the evolution of geometrically necessary dislocation (GND) density in a heterogeneous-structured CrMnFeCoNi HEA is investigated at different strains. This HEA consists of fine- and coarse-grained domains. GND density measurements are performed using electron backscatter diffraction. GND density increases significantly in the fine-grained domains while increases slightly in the coarse-grained domains. The disparity of GND density between the coarse and fine grains indicates a distinct deformation gradient, which is related to back-stress strengthening. At 7% strain, the GND density in the fine-grained domains reaches parity with that in the coarse-grained domains, indicating a transition from single slip to multiple slip. The local misorientation distributions are described by a lognormal function.

Dynamic compression responses of heterogeneous-structured CrMnFeCoNi high-entropy alloy at cryogenic temperatures

Dynamic compression experiments are conducted on a heterogeneous-structured CrMnFeCoNi high-entropy alloy (HEA) at different strain rates (1000–5000 s−1) and temperatures (123–293 K) with a split Hopkinson pressure bar system. Yield strength and strain hardening rate increase considerably with decreasing temperature at 5000 s−1 (low-temperature strengthening), but are insensitive to strain rate at 173 K, which can be well described by the Zerilli–Armstrong model. Compared to typical aluminum alloys and homogeneous-structured CrMnFeCoNi HEA, the heterogeneous-structured HEA exhibits higher thermal sensitivity and strain hardening rate. Microstructural characterizations show that dislocation density in the fine-grained domains increases more drastically than in the coarse-grained domains, inducing high deformation gradient between the coarse- and fine-grained domains. At 123 K, nano-scale primary and secondary deformation twins form in grain interior, along with a great number of stacking faults on twin boundaries; the twin width and spacing in coarse grains are considerably higher than in fine grains. In addition, the twin density at 123 K is significantly higher than that at 293 K. Overall, the increased deformation twinning and deformation gradient contribute to pronounced strengthening and strain hardening with decreasing temperatures in the heterogeneous-structured HEA under dynamic compression.

Microstructural evolution, mechanical properties and corrosion mechanisms of additively manufactured biodegradable Zn-Cu alloys

Additively manufactured (AM) biodegradable zinc (Zn) alloys constitute an important branch of orthopedic implants because of their moderate degradation properties and bone-mimicking mechanical properties. In this paper, the microstructural evolution and corrosion mechanisms of zinc-copper (Zn-Cu) alloys prepared by the laser-powder-bed-fusion (L-PBF) additive manufacturing method were investigated. Alloying with Cu significantly increases the ultimate tensile strength (UTS) of unalloyed Zn, but the UTS and ductility of unalloyed Zn and Zn-2Cu decrease with increasing laser energy density. Unalloyed Zn has a dendritic microstructure, while Zn-2Cu alloy has a peritectic microstructure. The formation of round peritectic grains is due to the low-temperature gradient of unalloyed Zn during the AM. The Zn-2Cu samples exhibited higher corrosion rates, addressing the problem of slow degradation of unalloyed Zn. The grain size distribution influences the corrosion behavior of the material. It enhances the corrosion rates of materials with fine grains in a non-passivating environment. However, the 100% extracts of Zn-2Cu samples exhibited greater values of cellular activity compared to unalloyed Zn samples, thus confirming their better cytocompatibility. This work demonstrates the great potential to design and modulate biodegradable Zn alloys to fulfill clinical needs by using AM technology.

Strength and ductility improvement in a heterostructured Mg-Gd-Y alloy with inversely-gradient hardness distribution

The Mg-8.75Gd-2.85Y (wt%) alloy processed by surface mechanical attrition treatment (SMAT) was annealed at 350 °C followed by peak-ageing. Recrystallization occurred in the surface layer of the specimen induced by the annealing treatment. The obtained heterostructure contained a fine-grained (FG) layer with thickness of about 350 μm on the top and a coarse-grained (CG) layer at the bottom. The sample exhibited a reversely-gradient distribution in hardness, in which the FG layer showed lower values than the CG layer. It was related to the different behaviors of recrystallization and precipitation. Compared with the homogeneous CG alloy, the heterostructured sample exhibited enhancement in both strength and ductility. The increase of yield strength was mainly ascribed to grain boundary strengthening and dislocation strengthening. The random texture of the FG layer and the synergetic effect of the heterostructure were beneficial to the improvement of ductility. This work provides valuable insights for developing gradient-structured Mg-RE alloys for high performance in engineering applications such as automotive, aerospace and defense industries.

Study on the interaction between inherent minerals of coal with refuse derived fuel (RDF) during co-firing

In this paper, refuse derived fuel (RDF) and bituminous coal were co-fired to investigate the particulate matter (PM) yields and the interaction between the inherit minerals in a lab-scale drop tube furnace (DTF). The PM1-10 yields during the co-firing of coal and RDF dramatically decreased by 16.29 %∼28.5 % of the combustion of coal alone. In addition, methane auxiliary combustion inhibited the PM1 yields by 7.95 % at air atmosphere. The Si-rich minerals in coal interreacted with the organic alkali (earth) metals in RDF, massively generating sticky particles with high liquid amount of K-Al-Si and Ca-Al-Si, promoting the transformation of fine grains into coarser mode. Moreover, it was proved that both methane auxiliary combustion and co-firing can reduce the emission of fine particles. The additional heat accelerated the burn of the char at the early stage of combustion, providing adequate time for the interaction between the inorganic species. Through thermodynamic equilibrium calculations of 1500 ∼ 3000 fly ash grains, it was found that co-firing increased the formation of sticky particles by 64.8 %∼70.3 %, resulting in a significant enhancement in capturing fine particles and Na, K vapor. Therefore, the co-firing of coal with RDF offers a promising approach to realize the harmless and resourceful treatment of municipal solid waste (MSW), and inhibit land resource losses caused by landfill